Planet Formation and Evolution 2019
Rostock, Feb 27 - Mar 01, 2019 Rostock, Feb 27 - Mar 01, 2019
Organization Committee
J¨urgenBlum (Braunschweig) Stefan Dreizler (G¨ottingen) Cornelis Dullemond (Heidelberg) Barbara Ercolano (M¨unchen) Artie Hatzes (Tautenburg) Hubert Klahr (Heidelberg) Willy Kley (T¨ubingen) Alexander Krivov (Jena) Ralph Neuh¨auser(Jena) Susanne Pfalzner (Bonn) Heike Rauer (Berlin) Ronald Redmer (Rostock, chair) Mario Trieloff (Heidelberg) Sebastian Wolf (Kiel) Gerhard Wurm (Duisburg)
Local Organization Committee
Ronald Redmer Waltraud Dulinski Clemens Kellermann Anna Julia Poser Ludwig Scheibe Nadine Nettelmann Martin Preising
Sponsors
University of Rostock Institute of Physics DFG Research Unit 2440
Venue
H¨orsaal1 Institute of Physics Albert-Einstein-Straße 24 18059 Rostock
2 Planet Formation and Evolution 2019
Preface
The German community of researchers working in the fields of planet formation, exoplanets and planetary systems, protoplanetary and debris disks, astrobiology, and planetary research in general organizes the workshops ”Planet Formation and Evolution” since 2001. The meetings in the series are typically held every 1,5 years at different German universities that host research groups actively working on these topics. This workshop is the 12th in the series. PFE meetings are usually attended by up to 150 participants from all parts of Germany with a broad international participation. Following the spirit of the previous very stimulating meetings, the goal of this workshop is to provide a common platform for scientists working in the fields listed above. Most importantly, this workshop is aimed at stimulating and intensifying the dialogue between researchers using various approaches - observations, theory, and laboratory studies. In particular, students and postdocs are encouraged to present their results and to use the opportunity to learn more about the main questions and most recent results in adjacent fields. The workshops in the series are traditionally neutral in terms of funding. This implies that no registration fee is charged and that no financial support is offered to the participants. In exceptional cases, the organisers will try to arrange some support from the funds provided to us by the German Research Foundation (DFG) for the meeting organization.
Welcome Address
Welcome to the 12th Workshop on Planet Formation and Evolution in Rostock. The meeting is part of the program ”1419-2019”, celebrating the 600th anniversary of the University of Rostock. Our university was founded on November 12, 1419, in the church Saint Marien in the center of the city with a certificate of Pope Martin V and soon became recognized as the ”Northern Light” in the golden era of the Hanse. It is the oldest university in the Baltic Sea region. About 13500 students are currently enrolled in one of the nine faculties including Mathematics and Natural Sciences (MNF) and an Interdisciplinary Faculty (INF) with the Department of Light, Light and Matter (LLM). Main research areas at the Institute of Physics are Optics and Photonics, Surfaces and New Materials, and Atoms, Molecules, Clusters and Plasmas. The latter field includes also research in Planetary and Astroparticle Physics. Note that Astronomy and Astrophysics have also tradition in Rostock. For instance, Tycho Brahe studied in Rostock in 1566. Some historical astronomical instruments are on display in the small museum of the institute in the basement. We have also constructed an observatory on the roof of our new institute which will be used for teaching students and to perform amateur astronomical observations on variable stars and extrasolar planets. Tourists can walk along a planet hiking trail which starts at the old light house in Warnemnde near the beach. We hope that you enjoy your visit in the old Hanse City Rostock which has celebrated its 800th birthday in 2018. We wish you interesting sessions and discussions at the PFE 2019.
Thanks for coming and all the best, Ronald Redmer on behalf of the LOC
3 Rostock, Feb 27 - Mar 01, 2019
Tuesday, Feb 26
Registration and a first icebreaker get-together will start on Tuesday at 5 pm in the lecture hall’s foyer.
Wednesday, Feb 27
Registration will continue in the lecture hall’s foyer from 08:00 on. Time Talk ID Presenter Title
09:00 Redmer Welcome address
09:15 I01 Nixon The Maximum Mass Solar Nebula 09:45 I02 Kral Review of gas in debris discs
10:15 Poster Blitz 1 (Posters P101-P113) 10:30 Coffee Break
11:15 I03 Ormel What you don’t know about pebble accretion. 11:45 I04 Valencia Forming iron-rich and iron-poor Super-Earths
12:15 Poster Blitz 2 (Posters P201-P213) 12:30 Lunch Break
14:00 I05 Morbidelli Beyond the Nice model: planet instabilities commonly sculpt all sort of planetary systems 14:30 I06 Heller How to park a hot Jupiter at 0.05 AU around a sun-like star for billions of years
15:00 Poster Blitz 3 (Posters P301-P312) 15:15 Coffee Break
16:00 I07 Helled Towards a better understanding of Jupiter’s formation and internal structure 16:30 I08 M´enard Observing the first phases of planet formation
17:00 Poster Session 1
4 Planet Formation and Evolution 2019
Thursday, Feb 28
Time Talk ID Presenter Title
08:30 T01 Daffern-Powell Creating Free-Floating Planets in Young Star Forming Regions 08:45 T02 Drazkowska Planetesimal formation during protoplanetary disk buildup 09:00 T03 Dullemond The DSHARP ALMA survey of protoplanetary disks 09:15 T04 Kobus The potential of combining MATISSE and ALMA observations: Constraining the structure of the innermost region in protoplanetary disks 09:30 T05 Ginski Direct detection of a substellar companion with a disk around CS Cha 09:45 T06 Gonzalez Back-reaction of dust on gas in protoplanetary discs: crucial, yet often overlooked
10:00 Poster Blitz 4 (Posters P401-P412) 10:15 Coffee Break
11:00 T07 Nordlund Rocky Planet Formation by Chondrule Accretion 11:15 T08 Lichtenberg Gradual desiccation of rocky protoplanets from 26Al-heating 11:30 T09 Bitsch Formation of planetary systems by pebble accretion and migration: Growth of gas giants 11:45 T10 Stammler Planetesimal Formation in Dust Traps 12:00 T11 Booth Dust and Gas in the HD 95086 Planetary System
12:15 Poster Blitz 5 (Posters P501-P513) 12:30 Lunch Break
5 Rostock, Feb 27 - Mar 01, 2019
Thursday, Feb 28 (cont.)
Time Talk ID Presenter Title
14:00 T12 Geiler The scattered disc of HR 8799 14:15 T13 Kim Constraining the detectability of water ice in debris disks 14:30 T14 Musiolik Does water ice stick as weakly as silicates? 14:45 T15 Schr¨apler Collisional properties of cm-sized high-porosity ice and dust aggregates to understand early planet formation
15:00 Poster Blitz 6 (Posters P601-P613) 15:15 Coffee Break
16:00 T16 Steinpilz First Results from the ISS-Experiment ARISE Studying Grain Collisions 16:15 T17 Raetz Updates on the story of the young transiting planet candidate CVSO-30b 16:30 T18 Nettelmann Interior models of young transiting planets: the case of K2-33b and CVSO-30b 16:45 T19 Meru Is the ring inside or outside the planet?: The effect of planet migration on dust rings
17:00 Poster Session 2 19:30 Conference Dinner
6 Planet Formation and Evolution 2019
Friday, Mar 1
Time Talk ID Presenter Title
08:30 T20 Schlecker The Cradle of the TRAPPIST-1 Multiplanet System 08:45 T21 Kuiper Modeling the Formation of super-Earth Atmospheres 09:00 T22 Schmidt Atmospheric fitting & formation of directly imaged planet candidates 09:15 T23 Picogna Photoevaporation of planet-forming discs: where is the smoking gun? 09:30 T24 Flock 3D radiation MHD/HD simulations of gas and dust in protoplanetary disk 09:45 T25 Ataiee How much does turbulence change the pebble isolation mass for planet formation? 10:00 T26 Blum Comet activity can only be understood if comets formed as small objects by gravoturbulent collapse
10:15 Coffee Break
11:00 T27 Kley Particle accretion onto planets in discs with hydrodynamic turbulence 11:15 T28 Marleau The accretion shock in gas giant formation 11:30 T29 Krivov What do debris disks tell us about planetesimal formation mechanisms? 11:45 T30 Sandor Formation of planets in pressure maxima of protoplanetary disks 12:00 T31 McNally Towards a new understanding of planet migration in modern models of protoplanetary discs 12:15 T32 Pfalzner Stellar fly-by possibly shaped the outer solar system
12:30 Redmer Closing remarks
7 Rostock, Feb 27 - Mar 01, 2019
Posters Poster ID Presenter Title
P101 Barraza Dust traps in the protoplanetary disc MWC 758: Two vortices produced by two giant planets? P102 Birnstiel Thermal Waves in Planet Forming Disks P103 Bertrang Line polarization: The most direct tracer of magnetic fields in disks P104 Gressel Magneto-thermal winds launched from weakly-ionized protoplanetary disks P105 Hirsh Cavity Size in Circumbinary Discs P106 Brunngr¨aber Self-scattering in protoplanetary disks: the polarization reversal due to Mie scattering P107 Jung From Protostellar to Protoplanetary Discs – When do planetary embryos form? P108 Luppe The Oddity of M-Star Planetary Systems: A Debris Disk Perspective P109 Manger ALMA Vortex Signatures are Potentially Created by the Vertical Shear Instability P110 Picogna The dispersal of planet-forming discs. A new generation of X-ray photoevaporation models. P111 Rab The gas structure of the HD 163296 planet-forming disk - Gas gaps or not? P112 Schulik Accreting gas giants in 3D - New results from radiation hydrodynamics P113 Rometsch Are transition disks formed by planetary systems? P201 Savvidou Thermal structures of inner protoplanetary discs P202 Sch¨afer Streaming Instability and Vertical Shear Instability in Global Simulations of Protoplanetary Disks P203 Sende Planets induce a size dependency in the particle distribution of evolved debris disks P204 Woelfer Thermal and Hydrodynamical Simulations of X-ray photoevaporation in metal depleted circumstellar discs P205 Zormpas Planet formation hotspots in Transition Disks P206 Bila Erosion of planetesimals through small atmospheric pressure excursions P207 Franz Dust Entrainment in Photoevaporative Winds P208 Garate Dust accretion preceding an outburst. The case of RW Aur dimmings. P209 Lenz Pebble Flux regulated Planetesimal Formation P210 Loehne How submillimetre wavelengths reflect grain size distributions in circumstellar discs P211 Ndugu Planet population synthesis : core growth via pebble accretion P212 Pawellek Clinging dust grains - Planetesimal belts are not only traced at long wavelengths P213 Sch¨afer Initial Mass Function of Planetesimals Formed by the Streaming Instability
8 Planet Formation and Evolution 2019
Posters Poster ID Presenter Title
P301 Forgacs-Dajka Application of method FAIR to identify mean motion resonances in the Kuiper belt P302 Singh Hydrodynamics around aggregating charged grains P303 Vericel Dust growth in the SPH code PHANTOM P304 Weber Size-dependent dust filtration induced by the presence of a giant planet P305 Ali-Dib Protoplanet growth stalling via dust convective overshooting P306 Baehr Formation of Cores in the Fragments of Self-Gravitating Disks P307 Elbakyan Gravitational fragmentation and formation of giant protoplanets on orbits of tens of AU P308 Bischoff Follow-up observations of YETI planet candidates P309 Moldenhauer The Influence of the Headwind on Planetary Proto-Atmospheres P310 Mugrauer Search for (sub)stellar companions of T Tauri stars in the Lupus star forming region P311 W¨ockel Echelle´ Spectroscopy and Analysis of Mascara-1b, an Extremely Hot Exoplanet Orbiting an A-star P312 Krieger Characterization of young accreting planets P401 Bogdan Constraints on Compound Chondrule Formation from Laboratory High Temperature Collisions P402 Kobsch Critical point of feldspars P403 Krause Collision experiments with hot dust related to planetesimal formation in inner disks P404 Landeck Collisions between centimeter-sized water-ice aggregates P405 Schneider Approaching Drag Instabilities in Laboratory Experiments P406 Tahir Application of Intense Ion Beams to Generate Planetary Core Conditions in the Laboratory P407 French Paramagnetic-to-diamagnetic transition in dense liquid iron and its influence on electronic transport properties P408 Bethkenhagen DFT+U equation of state for iron oxide P409 Li First principles molecular dynamics study of the supercritical state of iron P410 Preising The Band Gap and the Melting Line of Dense Helium P411 Solomatova Carbon Sequestration in the Magma Ocean Implied by Complex Carbon Polymerization P412 Soubiran Ab initio study of Iron-Nickel alloys in Super-Earths cores
9 Rostock, Feb 27 - Mar 01, 2019
Posters Poster ID Presenter Title
P501 Caracas Retracing the condensation of the Giant Impact from ab initio atomistic simulations P502 Carpenter Onset of Collective Behavior of Sedimenting Particles in the Knudsen Regime P503 D¨ollinger Touchstone for Planet Formation and Evolution - F Stars vs. K Giants P504 Brauer The radiative transfer code POLARIS P505 Klahr Ultima Thule puts constrains on planet formation P506 Kollmer Ejecta Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids (EMPANADA) P507 Kruss How Magnetic Aggregation Can Help Forming Mercurys P508 Parker Enlarging habitable zones around binary stars in hostile environments P509 Schaan Behavior of volatiles during the Giant Impact P510 S¨uli Statistics and analysis of collisional parameters computed from 2D simulations P511 Faramaz From scattered-light to millimeter emission: A global view of the Gyr-old system of HD 202628 and its eccentric debris ring P512 Flores Chemistry in envelope and disk in protostar L1527 P513 Hellard Retrieval of the fluid Love number k2 in exoplanetary transit curves P601 Alibert A new metric to quantify the similarity between planetary systems - application to dimensionality reduction using T-SNE P602 Monsch The imprint of X-ray photoevaporation on the orbital distribution of giant planets P603 Bergez-Casalou Accretion and migration of multiple giant planets in their protoplanetary disc P604 Penzlin Migration of planets in circumbinary discs P605 Regaly Type-I migration of dust accreting low-mass planets P606 Rowther The Migration of Giant Planets in Self-gravitating Discs P607 Guenther Has stellar activity an impact on the evolution of planets, or their habitability? P608 Jungmann How charges on grains increase the sticking velocity P609 Kellermann Interior structure models and fluid Love numbers of exoplanets in the super-Earth regime P610 Linder Evolution and magnitudes of low-mass planets P611 Poser Irradiated atmospheres and the core mass of hot Jupiters P612 Scheibe Thermal evolution of adiabatic Uranus and Neptune and beyond P613 Vazan Contribution of the core to the thermal evolution of sub-Neptunes
10 Planet Formation and Evolution 2019
Talks Wednesday, Feb 27
11 Rostock, Feb 27 - Mar 01, 2019
I01: Wednesday, Feb 27, 09:15-09:45 Nixon, Christopher Department of Physics and Astronomy, University of Leicester The Maximum Mass Solar Nebula
Chris Nixon, Andrew King, Jim Pringle
The initial conditions of planet forming discs are complex, and it has often been required to resort to simple setups. To understand the initial properties of planet forming discs it is necessary to look at larger scales during the time at which the central protostar is forming. Many calculations of this process lead to the conclusion that the disc mass can be a significant fraction of the central protostar mass, suggesting that disc self-gravity may play a role. Similarly, considering the mass in planets and taking a reasonable efficiency for planet formation, say 1-10%, it is also evident that the disc must have been self-gravitating at some stage. Previous simulations have demonstrated that the spiral features present in self-gravitating protoplanetary discs are capable of accumulating dust into planetesimals on near-dynamical timescales. This may populate the young disc with large planetesimals and allow the early growth of planets. Once the protostellar envelope decays and protoplanetary discs become observable, many planets may already be in place affecting what we see.
I02: Wednesday, Feb 27, 09:45-10:15 Kral, Quentin Observatoire de Paris Review of gas in debris discs
It is well-known that more than one-fourth of stars possess a planetesimal belt. The planetesimals in these belts collide and produce small debris (dust grains) that can then be readily detected. These debris discs were thought to be devoid of gas. But now, mainly thanks to ALMA, this paradigm is changing as we discover that gas is in fact common in these > 10 Myr old planetary systems with belts. The observed gas is produced in the belts and released from volatile-rich planetesimals. It’s a godsend as by detecting this gas, we can then infer the composition of planetesimals from which it was released, which is a first around main-sequence stars. I will review the gas observations we have at hand as well as the most recent models that have been developed to explain all these observations. Some of the detected gas discs are massive, which is surprising because the input rate from gas released by planetesimals doesn’t seem high enough to produce them. One could argue that the observed massive discs are from primordial origin (i.e. a remnant of the protoplanetary disc stage) but how could gas resist against photoevaporation for so long (i.e. for > 50 Myr). I will present a new theory that unravels this long-standing mystery.
12 Talks on Wednesday, Feb 27 Planet Formation and Evolution 2019
I03: Wednesday, Feb 27, 11:15-11:45 Ormel, Chris W. Anton Pannekoek Institute for Astronomy, University of Amsterdam What you don’t know about pebble accretion.
It is well-known that protoplanets and planetesimals can (in some situations) grow rapidly by sweeping up small particles, due to the combined effect of gas drag and gravity. This mechanism, known as pebble accretion, has been invoked to explain the architecture of the solar system as well as exoplanetary systems. However, there is more to pebble accretion than merely a way to grow planets big and fast. In this contribution I will touch upon a few of its other implications to planet formation.
I04: Wednesday, Feb 27, 11:45-12:15 Valencia, Diana Department of Physical & Environmental Sciences, University of Toronto Forming iron-rich and iron-poor Super-Earths
Jennifer Scora, Diana Valencia, Alessandro Morbidelli, Seth Jacobsen
With the growing number of measured mass and radius for low-mass planets, we are beginning to see trends in the population. In particular, there is a spread in the composition of planets that are thought to be rocky. Many planets are very iron-rich, while some are iron-poor. We set out to investigate if this spread in composition can be explained by the reprocessing that happens during collisions in the giant impact phase. We use an N-body code with more realistic collisions outcomes, that include debris production taken from parameterized smooth-particle hydrodynamic codes used to investigate collisions. We find that forming iron-rich planets requires an efficient collisional grinding process, and that iron-depletion can be established for very low-mass planets. Forming super-Moons of more than 5 times the mass of the Earth are problematic.
Talks on Wednesday, Feb 27 13 Rostock, Feb 27 - Mar 01, 2019
I05: Wednesday, Feb 27, 14:00-14:30 Morbidelli, Alessandro Observatoire de la Cote d’Azur Beyond the Nice model: planet instabilities commonly sculpt all sort of planetary systems
This talk will present the latest developments of the Nice model concerning the timing of the giant planet instability in the Solar System. It will then show that instabilities of planets in resonant chains have to be a quite generic outcome of the evolution of planetary systems after the removal of gas from the protoplanetary disk. Such instabilities explain the eccentricity distribution of giant planets, the observed period ratio distribution between neighboring super-Earths, and the so-called Kepler dichotomy. The instability that characterized the evolution of the Solar System was therefore not an exceptional event.
I06: Wednesday, Feb 27, 14:30-15:00 Heller, Ren´e Max Planck Institute For Solar System Research How to park a hot Jupiter at 0.05 AU around a sun-like star for billions of years
Since the discovery of Jupiter-sized planets in extremely close orbits around sun-like stars, several mechanisms have been proposed to form these ”hot Jupiters”. It has nevertheless remained difficult to understand the common hot Jupiter pile-up at 0.05 astronomical units (or 10 solar radii) from their host stars, an observation that is thought to be an imprint of the formation mechanism or mechanisms of hot Jupiters. Moreover, conventional models of tidal dissipation in sun-like stars suggests that many of the observed hot Jupiters should have fallen into their host stars by now. So why do they still exist? And finally, while hot Jupiters were the dominant type of exoplanet to be discovered initially (1995 - 2000), it turned out that only about 1% of all sun-like stars actually harbor a hot Jupiter. Why? I will present an updated picture of type II planet migration under the effect of evolving stellar tides [1]. Recent progress in the parameterization of dynamical tide in the convective envelopes of young solar-type stars suggests that tides can be sufficiently strong to stop the radial (type II) migration of a Jupiter-sized planet at several times 0.01 AU. Once the protoplanetary disk has gone, any surviving hot Jupiter can be pushed outward to about 0.05 AU, where the star’s tidal torque vanishes. As the star spins down due to magnetic braking, its corotation radius can move beyond the planet’s orbital radius on a billion year time scale, thereby initiating the tidally driven infall of the planet. The resulting orbital decay, however, is negligible due to the contraction of the highly dissipative convective envelopes in sun-like stars. I will also show how the lower pile-up efficiency around metal-poor stars might partly explain the absence of a hot Jupiter pile-up in the Kepler data. [1] https://arxiv.org/abs/1806.06601
14 Talks on Wednesday, Feb 27 Planet Formation and Evolution 2019
I07: Wednesday, Feb 27, 16:00-16:30 Helled, Ravit University of Zurich Towards a better understanding of Jupiter’s formation and internal structure
Giant planets are thought to have cores in their deep interiors, and the division into a heavy-element core and hydrogen-helium envelope is used in both formation and structure models. I will briefly discuss the standard model for giant planet formation, and will show that the primordial internal structure of giant planets depends on their formation location and growth history. I will present a new formation scenario for Jupiter that is consistent with cosmochemical constraints, and discuss the expected primordial internal structure of Jupiter from recent formation and evolution models (fuzzy core, inhomogeneous interior). Finally, I will discuss the importance of these results for interpreting the measurements of the Juno (NASA) mission, and for giant exoplanets characterization.
I08: Wednesday, Feb 27, 16:30-17:00 M´enard,Fran¸cois Institut de Plan´etologieet d’Astrophysique de Grenoble Observing the first phases of planet formation
TBD
Talks on Wednesday, Feb 27 15 Rostock, Feb 27 - Mar 01, 2019
Talks Thursday, Feb 28
16 Planet Formation and Evolution 2019
T01: Thursday, Feb 28, 08:30-08:45 Daffern-Powell, Emma University of Sheffield Creating Free-Floating Planets in Young Star Forming Regions
Emma Daffern-Powell & Richard Parker
The majority of stars form in clustered environments where close encounters with passing stars can affect planetary systems through a variety of mechanisms, including the disruption of orbits and the exchange of planets between systems. In particular, it is possible for a planet to be ejected as a result of encounters, where it may either remain as a free-floating planet or be captured by another system. In this way, encounters contribute to the observed population of free-floating planets, as well as the diverse range of orbital properties observed in exoplanets. I am using N-body simulations of star-forming regions to investigate the creation and capture of free-floating planets, as well as their corresponding orbital properties. Our simulations cover a range of initial conditions for clustered environments, including densities and dynamical states, and we use observations of exoplanets to inform our choice of the initial distributions of planetary orbits. In this talk I will present results which show that the fraction of free-floating planets created is a strong function of the initial properties of the cluster, and that planets can be captured onto extremely wide orbits that are consistent with some extreme exoplanets - many of which are good candidates for direct imaging surveys.
T02: Thursday, Feb 28, 08:45-09:00 Drazkowska, Joanna LMU Munich Planetesimal formation during protoplanetary disk buildup
J. Drazkowska and C.P. Dullemond
Dust growth in protoplanetary disks is the first step towards planet formation. Models of dust growth are typically computed on a backdrop of fully formed class II protoplanetary disk model. However, studies of the mass budget of class II disks suggest that at this stage significant portion of solids must already be locked in larger objects, such as kilometre-sized planetesimals. I will present the results of my recent work concerning dust growth and planetesimal formation during protoplanetary disk buildup and its further evolution.
Talks on Thursday, Feb 28 17 Rostock, Feb 27 - Mar 01, 2019
T03: Thursday, Feb 28, 09:00-09:15 Dullemond, Cornelis Zentrum f¨urAstronomie der Universit¨atHeidelberg The DSHARP ALMA survey of protoplanetary disks
Sean Andrews, Laura Perez, Cornelis Dullemond, Andrea Isella and the DSHARP Team
The Disk Substructures at High Angular Resolution Project (DSHARP) is an ALMA Large Programme that has imaged 20 protoplanetary disks in ALMA band 6 (1.3 mm) at a resolution of approximately 40 milliarcsecond. This resolution allows substructures to be resolved that are smaller than the pressure scale height of the disk. We find that most disks display multiple concentric dust rings, some show m=2 spiral features, and two sources show, in addition to the rings, arclike features. This talk will describe the results, as well as discuss implications for the theory of protoplanetary disks.
T04: Thursday, Feb 28, 09:15-09:30 Kobus, Julia Kiel University The potential of combining MATISSE and ALMA observations: Constraining the structure of the innermost region in protoplanetary disks
J. Kobus, S. Wolf, and R. Brunngr¨aber
To study the initial conditions of planet formation, multi-wavelength long-baseline interferometric observations are very promissing, as they trace different disk layers with spatial resolutions comparable to our own solar system. We evaluate the advantage of combining observations with MATISSE/VLTI and ALMA to constrain the radial and vertical structure of the dust in the potential planet-forming region of circumstellar disks in nearby star-forming regions. Based on a disk model with a parameterized dust density distribution, we apply 3D radiative transfer simulations to obtain ideal intensity maps. These are used to derive the corresponding wavelength-dependent visibilities one would obtain with MATISSE as well as simulated ALMA maps reconstructed with the CASA ALMA simulator. We find that with ALMA one can derive significant constraints on the disk surface density in the innermost disk region within reasonable integration times, whereas constraining the density structure with MATISSE alone is very challenging. However, the estimation of basic disk parameters can be considerably improved by combining the complementary MATISSE and ALMA observations. We also find that ALMA is sensitive to the amount of large dust grains settled to the disk midplane.
18 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T05: Thursday, Feb 28, 09:30-09:45 Ginski, Christian API Amsterdam Direct detection of a substellar companion with a disk around CS Cha
We recently used the SPHERE high resolution extreme AO imager at the VLT to observe the CS Cha system in polarized light. We resolved for the first time the circumstellar disk around CS Cha in scattered near infrared light. Surprisingly we found a very faint, but highly polarized companion outside of the disk at a projected separation of 230 au. Using archival VLT and HST data we can show that the companion is indeed gravitationally bound to the CS Cha system. We present radiative transfer models to explain the available photometry and the high degree of polarization. We find that the companion is most likely at the planet/brown dwarf boarder and is surrounded by its own, highly inclined disk. Given the body of information that is available we speculate on the formation of the object.
T06: Thursday, Feb 28, 09:45-10:00 Gonzalez, Jean-Fran¸cois Centre de Recherche Astrophysique de Lyon, France Back-reaction of dust on gas in protoplanetary discs: crucial, yet often overlooked
Gonzalez J.-F., Laibe G., Maddiston S.T.
Planets form in protoplanetary disks around young stars form the aggregation of small dust grains into larger and larger objects. The differential velocity between gas and dust in these disks causes aerodynamical drag, which drives the dust dynamics. Most studies take only into account the drag force of gas on dust but neglect its back-reaction, i.e. the drag force on dust on gas. I will show that its effects can be important on the disk structure and dust dynamics, affecting the initial stages of planet formation, as well as in the interpretation of disk observations.
Talks on Thursday, Feb 28 19 Rostock, Feb 27 - Mar 01, 2019
T07: Thursday, Feb 28, 11:00-11:15 Nordlund, Aake Niels Bohr Institute / STARPLAN, Copenhagen Rocky Planet Formation by Chondrule Accretion
Andrius Popovas, Ake˚ Nordlund, Jonathan Ramsey
We present results from recently performed nested-grid, high-resolution hydrodynamic and radiation-hydrodynamics simulations of gas and particle dynamics in the vicinity of Mars- to Earth-mass planetary embryos (arXiv:1801.07707 & 1810.07048). The simulations extend from the surface of the embryos to a few vertical disk scale heights, with a vertical dynamic range of ∼ 1.4 × 105. We include heating due to the accretion of solids, radiative energy transport, and resolved, accretion-driven 3-D convection. Convection driven by a −6 −1 nominal accretion rate of 10 M⊕ yr does not significantly alter the pebble accretion rate. The ray-tracing radiative transfer simulations show that rocky planet embryos embedded in protoplanetary disks can retain hot and light atmospheres throughout much of the evolution of the disks. Importantly, our results show that particles larger than the chondrules ubiquitously observed in meteorites are not required to explain the accretion of rocky planets such as Earth and Mars within the lifetime of the disk. We find that, due to cancellation effects, accretion rates of a given size particles are nearly independent of disk surface density. As a result, we can estimate accurate growth times for specified particle sizes. For 0.3–1 mm size particles, and assuming a dust-to-gas ratio of 1:100, the growth time from a small seed is ∼1.5 million years for an Earth mass planet at 1 AU and ∼1 million years for a Mars mass planet at 1.5 AU.
20 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T08: Thursday, Feb 28, 11:15-11:30 Lichtenberg, Tim University of Oxford Gradual desiccation of rocky protoplanets from 26Al-heating
Tim Lichtenberg, Gregor J. Golabek, Remo Burn, Michael R. Meyer, Yann Alibert, Taras V. Gerya, Christoph A. Mordasini
The formation and distribution of Earth-like planets remain poorly con- strained. However, stochasticity during accretion and the variety of exoplanet compositions favor rocky worlds covered in thick volatile ice layers as the dominant family of terrestrial analogues, deviating from the water-poor inner-Solar system planets. Here, we report the results of theoretical calculations demonstrating the power of 26Al, a short-lived radionuclide abundant in the early Solar system, to control the water content of terrestrial exoplanets by rapid dehydration of accreted planetesimals. Using numerical models of planet formation, evolution, and interior structure, we generate synthetic planet populations influenced by varying levels of 26Al-heating during accretion. We show that planet bulk water fraction and radius are anti-correlated with initial 26Al levels. This yields a system-wide correlation of bulk abundances, consistent with the lack of a clear water budget trend in the TRAPPIST-1 planets. The generic sensitivity of exoplanet observables on 26Al inferred from our models suggests two distinct classes of rocky exoplanets: high-26Al systems form small, water-depleted planets, those devoid of 26Al form ocean worlds, with the mean planet radii deviating by up to ∼10%.
Talks on Thursday, Feb 28 21 Rostock, Feb 27 - Mar 01, 2019
a Planetesimal H O retention f /f 2 H2O H2O,init 1.0 0.8 0.6 0.4 0.2 0.0
+1.0 #A
Al >90 wt% H O lost 26 2 / 0 +0.5
Al Streaming
26 instability 10
0 Solar system abundance #B at CAI formation
#C -0.5 Inefficient planetesimal dehydration Al abundance, log 26 #D -1.0 1 2 3 5 7 10 20 30 50 70 100
Planetesimal radius rplts [km] b Resulting exoplanet population
G stars 26 #A 10× Al , 50 km Median Kernel Combined: density G & M estimate 1× 26 Al , 50 km Interquartile range Separate #B 26 M stars rplts Al 0
0.3× 26 Al , 50 km #C
0.1× 26 Al , 50 km #D
0 5 10 15 20 25 30 Final bulk planet water mass fraction [wt%] (a) Water retention in planetesimals subject to a varying degree of 26Al heating. (b) Bulk planet water abundances fH2O in exoplanet populations with Mplanet = 0.1–10 MEarth and 26 fH2O > 0, formed with fixed Al0 and planetesimal radius rplts.
22 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T09: Thursday, Feb 28, 11:30-11:45 Bitsch, Bertram Max-Planck Institute for Astronomy Formation of planetary systems by pebble accretion and migration: Growth of gas giants
Bitsch, B., Izidoro, A., Raymond, S.N., Johansen, A., Morbidelli, A., Lambrechts, M., Jacobson, S.
The exact formation mechanism of giant planets is still a mystery. The only thing certain is that giant planets have to form during the gas-disc phase, as they accrete their gas from the protoplanetary disc. In the core accretion scenario, a planetary core forms first, which can then accrete gas from the protoplanetary disc. Forming cores only via planetesimal (100km sized objects) accretion can take longer than the gas disc lifetime. However, the recently developed theory of pebble accretion allowed a dramatic reduction in the core formation time-scale. This reduction of the growth time-scale depends on the amount of pebbles (mm-cm sized objects) available in the protoplanetary disc. During the growth, the planet also migrates through the protoplanetary disc, where type-I migration can lead to dramatic loses of semi-major axis of the growing planet. Even if the planet forms at several AU, it might migrate all the way to the inner disc.
We will present results of N-body simulations including pebble and gas accretion, planet migration as well as disc evolution that show the formation of different types of exoplanetary systems. We identify a pebble flux threshold below which migration dominates and moves the planetary core to the inner disk, where the pebble isolation mass is too low for the planet to accrete gas efficiently. The growth of giant planets in our model requires a threshold level of pebble flux to allow a fast enough growth of the planetary core to out compete planetary migration. An even further increase of the pebble flux allows the formation of systems of multiple gas giants. At the same time our simulations show that planetary embryos forming interior to 5 AU do not grow to gas giants, even if the migration rates are low and the pebble flux is large. The formed planets instead grow to just a few Earth masses, the mass regime of super-Earths. This stunted growth is caused by the low pebble isolation mass in the inner disc and is therefore independent of the pebble flux. Additionally we show that the long term evolution of our formed planetary systems can naturally produce systems with inner super Earths and outer gas giants as well as systems of giant planets on very eccentric orbits.
Talks on Thursday, Feb 28 23 Rostock, Feb 27 - Mar 01, 2019
T10: Thursday, Feb 28, 11:45-12:00 Stammler, Sebastian LMU Munich Planetesimal Formation in Dust Traps
Stammler, S. M.; Birnstiel, T.; Drazkowska, J.
Radial drift of dust particles is a long-standing problem in planet formation. Due to its pressure gradient, gas in protoplanetary disks is orbiting the central star with sub-Keplerian velocities. Dust particles, on the other hand, try to orbit with Keplerian velocities. They feel a headwind from the gas, lose angular momentum, and drift towards the star on short timescales. Observations of protoplanetary disks, however, show more dust around protostars than models of circumstellar disks with radially drifting dust particles would predict. As a solution to this problem pressure bumps have been proposed in the past, that can trap dust particles and prevent them from drifting towards the star. And indeed, recent high resolution observations of disks with ALMA show dust trapped in ring-like sub-structures. Dust traps, however, are also thought to be locations of planet formation by converting dust pebbles into planetesimals. But if the formation of planetesimals is too efficient, it would remove dust from observations by locking it into large bodies that are invisible to ALMA. To investigate this problem in more detail, we implemented various flavors of planetesimal formation into our dust growth and disk evolution code DustPy. We found that even under the most optimistic conditions only a few percent of the total dust mass is transformed into planetesimals.
24 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T11: Thursday, Feb 28, 12:00-12:15 Booth, Mark AIU, FSU Jena Dust and Gas in the HD 95086 Planetary System
In our efforts to understand the formation and evolution of planetary systems and how other planetary systems relate to the Solar System, some of the best systems to study are those where we have detected both a planet (or planets) and a debris disc as the interplay between the two can tell us even more about the system. In this regard, HD 95086 makes an excellent case study. This 17 Myr star hosts both a giant planet on a wide orbit and one of the brightest debris discs known. Using ALMA, we have imaged this system at millimetre wavelengths and high resolution to determine that the disc extends from roughly 100-300 AU, one of the widest discs known. We find that the location of the inner edge can be explained by the effect of the known planet but only if the eccentricity of the planet is > 0.26. We also tentatively detect a very low level of CO emission, predominantly coming from the South side of the disc. The low CO mass means that it cannot be primordial and marks this as one of only four systems which we know to have second generation gas production. In addition to the disc we also find two bright, compact sources. The origin of the brightest of these is hard to explain. Processes within the disc that can explain such a large concentration of dust (such as a forming planet, massive collision etc.) would also require or result in a concentration of CO at that location, which is not seen, meaning that it is more likely to be a background galaxy, even though the chances of such a coincident alignment are small.
Talks on Thursday, Feb 28 25 Rostock, Feb 27 - Mar 01, 2019
T12: Thursday, Feb 28, 14:00-14:15 Geiler, Fabian AIU Jena The scattered disc of HR 8799
Fabian Geiler, Alexander V. Krivov, Mark Booth, Torsten L¨ohne
HR 8799 is a young F0-type star with four directly imaged giant planets (Marois et al. 2010) and two debris belts (e.g. Su et al. 2009), one located exterior and another one interior to the region occupied by the planetary orbits. Having an architecture similar to that of our Solar System, but also revealing dissimilarities such as high masses of planets and a huge radial extent and a high mass of the outer debris belt, HR 8799 is considered to be a benchmark to test formation and evolution models of planetary systems. We demonstrate that the models of the outer disc, proposed previously to reproduce Herschel observations (Matthews et al. 2014), are inconsistent with the ALMA data (Booth et al. 2016), and vice versa. We show that a narrow planetesimal belt and a radiation pressure induced dust halo cannot account for the observed radial brightness profiles. A single, wide planetesimal disc does not reproduce the data either. Instead, we propose a two-population model, comprising a Kuiper-Belt-like structure of a low-eccentricity planetesimal population (“the classical Kuiper Belt”) and a high-eccentricity population of comets (“scattered disc”). We argue that such a structure of the exo-Kuiper belt of HR 8799 could be explained with planet migration scenarios analogous to those proposed for the Kuiper Belt of the Solar System, provided migration occurred to the planet cores before they accreted their gas envelopes.
26 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T13: Thursday, Feb 28, 14:15-14:30 Kim, Minjae Christian-Albrechts-Universit¨atzu Kiel Constraining the detectability of water ice in debris disks
Minjae Kim, Sebastian Wolf, Alexey Potapov, Harald Mutschke, and Cornelia J¨ager
Context. Given the importance of water in the development and preservation of life, identifying the distribution of water in debris disks is of central interest in the field of astrobiology. Furthermore, icy dust grains are expected to play important roles in the planet formation process. However, currently available observations only allow weak conclusions about the existence of water ice in debris disks. Aims. We investigate the feasibility to detect water ice in typical debris disk systems. We take following effects into account: sublimation of ice, dust production through planetesimal collisions, and photosputtering by UV bright stars. We consider dust mixtures consisting of amorphous ice, crystalline ice, astrosilicate, carbonaceous material, and vacuum (i.e., porous ice grains). Methods. We calculate optical properties of inhomogeneous dust mixtures using effective medium theories, e.g. Maxwell-Garnett rules. Subsequently, we generate synthetic debris disk observables, such as spectral energy distributions and spatially resolved scattered light and thermal re-emission images with our code ”Debris disks around Main-sequence Stars” (DMS; Kim et al. 2018). Results. We find that the prominent 3.07-micron ice features can be detected in future observations of debris disks with JWST (James Webb Space Telescope) and ELT (Extremely Large Telescope). The sublimation of icy dust grains, collisions between planetesimals, and photosputtering due to UV sources clearly affect the observational appearance of debris disk systems. In addition, the location of the ”snow line” is determined by the dust properties, i.e., the fractional ratio of ice, astrosilicates, or graphites for the icy-dust mixture. Finally, highly porous icy dust grains are found to be hotter than compact ones, thus affecting the inner sublimation radius of debris disk systems.
Talks on Thursday, Feb 28 27 Rostock, Feb 27 - Mar 01, 2019
T14: Thursday, Feb 28, 14:30-14:45 Musiolik, Grzegorz University of Duisburg-Essen Does water ice stick as weakly as silicates?
Grzegorz Musiolik, Gerhard Wurm
The sticking properties of water ice are important for the collisional growth in the planet forming process. We study the sticking and rolling properties of sub-mm ice spheres in a temperature range between 170 - 240 K. The critical sticking and rolling forces increase strongly between 170 K and 210 K. Within this range, the surface energy for the water ice spheres increases from 0.01 J/m2 to 1 J/m2. In application to protoplanetary disks this means that water ice beyond the snowline is not stickier than silicate dust. Its advantage for aggregation might hence be smaller than often considered in earlier works.
T15: Thursday, Feb 28, 14:45-15:00 Schr¨apler,Rainer IGeP, TU Braunschweig Collisional properties of cm-sized high-porosity ice and dust aggregates to understand early planet formation
Rainer Schr¨apler,Wolf Landeck, J¨urgenBlum
In dead zones of protoplanetary disks, it is assumed that the initially micrometer-sized particles grow by Brownian motion and differential drift. When collisional compaction sets in, drift-unduced growth becomes more efficient and the growing aggregates collect slower and therefore smaller particles. Once they have reached the mid-plane, they form a thin dense layer and gain relative velocities by the streaming instability or the onset of shear turbulence. In order to experimentally simulate this growth stage, we produced highly porous ice aggregates with cm sizes and porosities of 90%. After that, we performed collision experiments with the aggregates and determined their limit of adhesion and their coefficient of restitution, which is important for their further collisional evolution on their way to form planetesimals. Finally we developed an analytical model to calculate the sticking threshold and the restitution coefficient of our porous particles from their fundamental properties (e.g Young modulus, Poisson number, viscosity), based on the Brillantov and P¨oschel compact particle collision model. In this talk, we will present the experimental and theoretical results.
28 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T16: Thursday, Feb 28, 16:00-16:15 Steinpilz, Tobias University of Duisburg-Essen First Results from the ISS-Experiment ARISE Studying Grain Collisions
Steinpilz Tobias, Jungmann Felix, Musiolik Gregor, Kruß Max, Demirci Tunahan, Bila Tanja, Kollmer Jonathan, Teiser Jens, Wurm Gerhard
For two-month in 2018 we carried out a granular matter experiment onboard of the ISS. During this time, we collected a wealth of image-data on which the analysis is still ongoing. Here we will present our first results on collision properties of mm particles and clustering - properties which are important in early phases of planet formation.
T17: Thursday, Feb 28, 16:15-16:30 Raetz, Stefanie Institut f¨urAstronomie und Astrophysik T¨ubingen(IAAT), Sand 1, 72076 T¨ubingen, Germany Updates on the story of the young transiting planet candidate CVSO-30b
T.O.B. Schmidt, C. Briceno, R. Neuh¨auserand YETI Team
CVSO-30 is a unique young low-mass system, because, for the first time, a close-in transiting and a wide directly imaged planet candidates are found around a common host star. The inner companion, CVSO-30b, is the first possible young transiting planet orbiting a previously known weak-lined T-Tauri star. An interesting feature of the light curve (LC) of CVSO-30 is that there is an overall change in the transit shape between observing seasons. It was showed that the unusual LC shapes and their variation can be explained by a precessing planet transiting a gravity-darkened star. We monitored CVSO-30 over a period of three years with the telescopes of the ’Young Exoplanet Transit Initiative’ (YETI). In four more seasons we carried out photometric follow-up observations. We can confirm that there is a change in the shape of the transits between different observations and that the fading event even disappears and reappears. If CVSO-30b would be a giant planet on a precessing orbit, which we cannot confirm, yet, the precession period may be shorter than previously thought. An alternative explanation for CVSO-30 may be an occultation of the star by dust from a disintegrating planet. CVSO-30 seem to share some features with other examples of disintegrating planets that have been discovered. Here I will tell the story of the young transiting planet candidate CVSO-30b and present new photometric observations.
Talks on Thursday, Feb 28 29 Rostock, Feb 27 - Mar 01, 2019
T18: Thursday, Feb 28, 16:30-16:45 Nettelmann, Nadine Institute of Physics, University of Rostock Interior models of young transiting planets: the case of K2-33b and CVSO-30b
Nadine Nettelmann, Anna Julia Poser, Stefanie Raetz, Richard Bischoff, Ralph Neuh¨auser, Ronald Redmer
Modeling observed planets in young open clusters and around mature stars offers a way to learn about planet formation and evolution. Here we give an overview on our activities to infer the composition of solar system and mature extrasolar giant planets. We then focus on two young individuals, the super-Neptune K2-33b (∼5 RE, ∼10 Myr), and the hot Jupiter candidate CVSO-30b (∼1.9 RJup, < 6 Myr), where the CVSO-30 system is an observational target of the YETI collaboration. Since planets at close orbits experience strong irradiation and gravitational attraction, they may be subject to evaporation. Assuming a simple core+gaseous envelope structure, we investigate the possible past and future nature of these planets with and without energy-limited mass loss and tidal disruption. We present our work in progress on this topic.
30 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
T19: Thursday, Feb 28, 16:45-17:00 Meru, Farzana University of Warwick Is the ring inside or outside the planet?: The effect of planet migration on dust rings
Farzana Meru, Giovanni Rosotti, Richard Booth, Pooneh Nazari, Cathie Clarke
Planet migration can shape the evolution of planets in protoplanetary discs and ultimately move them towards the locations at which they are discovered. Currently we have no direct observational test to determine if a planet is migrating in a protoplanetary disc. We explore the formation and evolution of dust rings in the presence of low mass (12-60 MEarth) migrating planets. Through two dimensional hydrodynamical simulations using gas and dust we find that the importance of perturbations in the pressure profile interior and exterior to the planet varies for different particle sizes. For small sizes, the dust enhancement occurs interior to the planet whereas it is exterior to it for large particles (see Figure). We predict that if the location of an observed dust ring in the midplane significantly shifts outwards as the wavelength is increased, this would be an observational signature of a migrating planet.
Talks on Thursday, Feb 28 31 Rostock, Feb 27 - Mar 01, 2019
Small dust
planet inner dust ring
Large dust
planet outer dust ring
32 Talks on Thursday, Feb 28 Planet Formation and Evolution 2019
Talks Friday, Mar 1
33 Rostock, Feb 27 - Mar 01, 2019
T20: Friday, Mar 1, 08:30-08:45 Schlecker, Martin MPIA The Cradle of the TRAPPIST-1 Multiplanet System
Martin Schlecker, Remo Burn, Christoph Mordasini, Thomas Henning, Hubert Klahr
Planet Population Synthesis is a statistical approach that serves as a bridge between theoretical planet formation and the observed population of exoplanets. It has led to testable predictions, such as the now-confirmed minimum in the planetary mass distribution between a few Earth masses and 40 Earth masses.
In order to apply this technique to the low-mass regime of host stars, we extend our framework to the different conditions in their protoplanetary disks. Changes to the original setup include a smaller inner disk radius, a down-scaled disk mass distribution, distinct morphologies for the solid disk and the gas disk, and N-body interaction between protoplanets.
As a test case, we create a population of systems with a host star mass of 0.1 solar masses and compare it to observables of the TRAPPIST-1 multi-planet system (Gillon et al. 2017). By randomly drawing initial locations for lunar-mass planetary embryos from a log-uniform distribution between 0.02 au and 10 au, we find that many features of this unique system can be reproduced. Using the resulting mean planetary mass as a metric, we find a domain in initial disk solid mass and disk extent favorable for the formation of systems similar to TRAPPIST-1.
34 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
T21: Friday, Mar 1, 08:45-09:00 Kuiper, Rolf Institute of Astronomy and Astrophysics Modeling the Formation of super-Earth Atmospheres
Context: In the core accretion paradigm of planet formation, gas giants form a massive atmosphere in a run-away gas accretion phase once their progenitors exceed a threshold mass: the critical core mass. On the one hand, the majority of observed exo-planets, being smaller and rock/ice-dominated, never crossed this line. On the other hand, these exo-planets have accreted substantial amounts of gas from the circumstellar disk during their embedded formation epoch. Methods: We investigate the hydrodynamical and thermodynamical properties of proto-planetary atmospheres by direct numerical modeling of their formation epoch. Our studies cover one-dimensional (1D) spherically symmetric, two-dimensional (2D) axially symmetric, and three-dimensional (3D) hydrodynamical simulations with and without radiation transport. We check the feasibility of different numerical grid geometries (Cartesian vs. spherical), perform convergence studies, and scan the physical parameter space with respect to planet mass and optical depth of the surrounding. Results: In terms of hydrodynamic evolution, no clear boundary demarcates bound atmospheric gas from disk material in a 3D scenario in contrast to 1D and 2D computations. The atmospheres denote open systems where gas enters and leaves the Bondi sphere in both directions. In terms of thermodynamics, we compare the gravitational contraction of the forming atmospheres with its radiative cooling and advection of thermal energy, as well as the interplay of these processes. The coaction of radiative cooling of atmospheric gas and advection of atmospheric-disk gas prevents the proto-planets to undergo run-away gas accretion. Hence, this scenario provides a natural explanation for the preponderance of super-Earth like planets. Additionally, we will show preliminary results on the effect of headwinds on the atmospheric properties. We may also present first results on the atmospheric properties of proto-planets on eccentric orbits.
Talks on Friday, Mar 1 35 Rostock, Feb 27 - Mar 01, 2019
T22: Friday, Mar 1, 09:00-09:15 Schmidt, Tobias Hamburger Sternwarte Atmospheric fitting & formation of directly imaged planet candidates
T. Schmidt & SPHERE consortium
The SHINE survey conducted on the SPHERE high-contrast imager at VLT aims to characterize the giant planet population beyond 5 AU around 400-500 nearby stars. Now, that more than half of the observations of SHINE are performed, more and more spectrophotometric information for known and new companion candidates is collected, that can be subsequently used to extract information on planetary and sub-stellar atmospheres and how they might have formed. I will give after a short introduction to direct imaging of extrasolar planets an overview of recent SPHERE imaging results, combined with preliminary hints and implications for planet formation.
T23: Friday, Mar 1, 09:15-09:30 Picogna, Giovanni Ludwig-Maximilians-University Photoevaporation of planet-forming discs: where is the smoking gun?
Picogna, Ercolano
Photoevaporation of planet disc winds by high energy radiation from the central is thought to play an important role for the dispersal of discs and have important implications for the formation and evolution of planetary systems. Observational evidence and diagnostoc of these winds is however still challanging. In this talk I will use theoretical models and arguments for searching for the smoking gun of photoevaporation in current and forth-coming observations.
36 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
T24: Friday, Mar 1, 09:30-09:45 Flock, Mario MPIA 3D radiation MHD/HD simulations of gas and dust in protoplanetary disk
We report new results from high-resolution global 3D radiation-hydrodynamics simulations with embedded particles. For a typical T Tauri star-disk system we investigate and compare hydrodynamical and magneto-hydrodynamical instabilities. The vertical shear instability (VSI) develops into a steady state turbulence resulting into turbulent speeds of a few percent of the local sound speed at the midplane, increasing to 20%, or 100 m s−1 , in the corona. The predominantly vertical motions induced by the VSI efficiently lift particles upward. Grains 0.1 and 1 mm in size achieve scale heights greater than expected in isotropic turbulence. We conclude that while kinematic constraints from molecular line emission do not directly discriminate between magnetic and nonmagnetic disk models, the small dust scale heights measured in HL Tau and HD 163296 favor turbulent magnetic models.
T25: Friday, Mar 1, 09:45-10:00 Ataiee, Sareh T¨ubingenUniversity How much does turbulence change the pebble isolation mass for planet formation?
S. Ataiee, C. Baruteau, Y. Alibert, and W. Benz
When a planet becomes massive enough, it gradually carves a partial gap around its orbit in the protoplanetary disk. A pressure maximum can be formed outside the gap where solids that are loosely coupled to the gas, typically in the pebble size range, can be trapped. The minimum planet mass for building such a trap, which is called the pebble isolation mass (PIM), is important for two reasons: it marks the end of planetary growth by pebble accretion, and the trapped dust forms a ring that may be observed with millimetre observations. By means of 2D gas hydrodynamical simulations, we found the minimum planet mass to form a radial pressure maximum beyond the orbit of the planet, which is the necessary condition to trap pebbles. We then carried out 2D gas plus dust hydrodynamical simulations to examine how dust turbulent diffusion impacts particles trapping at the pressure maximum. From our results of gas simulations, we provide an expression for the PIM vs. disk aspect ratio and turbulent viscosity. Our gas plus dust simulations show that the effective PIM can be nearly an order of magnitude larger in high-viscosity disks because turbulence diffuse particles out of the pressure maximum. This is quantified by our semi-analytical calculation, which gives an explicit dependence of the PIM with Stokes number of particles.
Talks on Friday, Mar 1 37 Rostock, Feb 27 - Mar 01, 2019
T26: Friday, Mar 1, 10:00-10:15 Blum, Jurgen IGeP, TU Braunschweig Comet activity can only be understood if comets formed as small objects by gravoturbulent collapse
The two competing models for planetesimal formation, namely by hierarchic agglomeration and gravoturbulent collapse, predict different physical properties for the resulting planetesimals. Two of these physical properties, the heat conductivity and the tensile strength, determine whether or not a body becomes a comet when approaching the sun. In the presentation, I will outline the two formation models, their predictions, a model for the heat conduction into the interior and predictions for comet activity. It turns out that only the gravoturbulent-collapse model resulting in small planetesimals predicts comet activity.
T27: Friday, Mar 1, 11:00-11:15 Kley, Wilhelm Universit¨atT¨ubingen Particle accretion onto planets in discs with hydrodynamic turbulence
Kley, Wilhelm; Picogna, Giovanni
Planets are born in protoplanetary discs growing from very small particles to full-grown planets. In the past years, it has been recognized that the growth process can be sped-up by accreting a large number of solid, pebble-sized objects that are still present in the protoplanetary disc.It is still an open question how efficient this process is in realistic turbulent discs. In this contribution we present results on the accretion efficiency of pebbles in turbulent discs that are driven by the purely hydrodynamical vertical shear instability (VSI). We perform global three-dimensional simulations of discs with embedded planets of different masses ranging from 5 to 100 Earth masses. Embedded in the flow is a swarm of pebbles in ten size bins that move under the action of drag forces between gas and particles. For well-coupled particles with unity Stokes number we find an accretion efficiency (rate of particles accreted over particles drifting inward) of about 2% for the lower mass planets. For masses between 10 and 30 Earth masses the core reaches the pebble isolation mass and the particles are trapped at the pressure maximum just outside of the planet, shutting off further particle accretion.
38 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
T28: Friday, Mar 1, 11:15-11:30 Marleau, Gabriel-Dominique Universit¨atT¨ubingen The accretion shock in gas giant formation
In the core-accretion formation scenario of gas giants, most of the gas accreting onto a planet is processed through an accretion shock. This shock is key in setting the forming planet’s structure and thus its post-formation luminosity, with dramatic observational consequences. Processes at and ahead of the shock determine the energy balance and post-shock conditions. We use one-dimensional radiation-hydrodynamical simulations with non-equilibrium radiation transport to obtain post-shock temperatures for a large grid of parameters. We find that usually, the temperature is given by the “free-streaming” limit, while for weaker shocks the dust opacity can make the shock hotter by several 100 K. At very high accretion rates of 0.1 ME/yr, the massive opacity of the gas raises the shock temperature by up to a factor of ca. four. We compare these results to original semi-analytical work, finding excellent agreement within the assumptions. We also compute the fraction of the total accretion energy which is brought into the planet and find it is significant compared to the internal luminosity. Overall, these findings suggest that warm starts are more plausible.
Talks on Friday, Mar 1 39 Rostock, Feb 27 - Mar 01, 2019
T29: Friday, Mar 1, 11:30-11:45 Krivov, Alexander AIU/FSU Jena What do debris disks tell us about planetesimal formation mechanisms?
Alexander Krivov, Mark Booth, Aljoscha Ide, Torsten L¨ohne, Anders Johansen, J¨urgen Blum
Two basic routes for planetesimal formation have been proposed in the last few decades. One is a classical ’slow-growth’ scenario. Another one is ’particle concentration’ models, in which small pebbles are concentrated locally and then collapse gravitationally to form planetesimals. We look into possibilities to distinguish between the two scenarios from debris disk data. Both types of models make certain predictions for the timescales of planetesimal formation, as well as the size spectrum and internal structure of newly born planetesimals. We use these predictions as input to simulate both initial stirring of debris disks left after the gas dispersal and their subsequent collisional evolution. The results are compared to various samples of debris disks. We find that disks of planetesimals formed by pebble concentration get self-stirred more rapidly than in the slow-growth scenario. Yet we identify a few young debris disk systems that cannot be self-stirred and require planets as stirrers, which makes them promising candidates for planet searches. The observed debris disk brightness as a function of a system’s age is found to be consistent with both planetesimal formation scenarios. However, regardless of the assumed planetesimal formation mechanism, explaining bright debris disks in the samples uncovers an intriguing ’disk mass problem.’ To reproduce such disks by collisional simulations, a total mass of planetesimals of up to ∼1000 Earth masses is required, which exceeds the total mass of solids available in the protoplanetary progenitors of debris disks. Possible solutions to the problem are discussed.
40 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
T30: Friday, Mar 1, 11:45-12:00 Sandor, Zsolt E¨otv¨osLor´andUniversity, Budapest Formation of planets in pressure maxima of protoplanetary disks
The solid component of a protoplanetary disk may suffer a rapid drift toward the star due to the drag force arising from the ambient gas orbiting with sub-Keplerian velocity. This drag force vanishes at a pressure maximum leading to the accumulation of solid particles. On the other hand, a pressure maximum can appear near a surface density maximum of the disk’s gaseous material, which can act as planet trap. The proximity of the planet trap and the accumulation place of solids may result in a fast accretion of pebbles and planetesimals enabling the rapid formation of the solid cores of giant planets (Guilera and S´andor, 2017, A&A, 604, id.A10, 18). In our follow-up investigation the accretion of solids is studied by N-body simulations in which a Moon-mass embryo grows by accreting planetesimals in the size regime 1-100 km. These planetesimals are assumed to form by streaming instability in a narrow ring in the pressure maximum when the dust-to-gas ratio exceeds the critical value. The transport of solids and the evolution of the gas surface density is investigated by solving numerically the corresponding differential equations.
Talks on Friday, Mar 1 41 Rostock, Feb 27 - Mar 01, 2019
T31: Friday, Mar 1, 12:00-12:15 McNally, Colin Queen Mary University of London Towards a new understanding of planet migration in modern models of protoplanetary discs
Colin McNally, Richard Nelson, Sijme-Jan Paardekooper
Protoplanetary discs are believed to accrete onto their central star because of magnetic stresses. At the same time, planets form in these discs and are forced to radially migrate when subject to unbalanced torques from the disc gas. Although the basic dynamics of the discs from which planetary systems form have been well developed in the traditional model of a viscous disc, our rapidly evolving understanding of the physical conditions that prevail in protoplanetary discs dictates that the levels of turbulence found must be small. Importantly, non-ideal MHD effects largely suppress MHD instabilities, leading to an effectively low viscosity flow. Motivated by these models, we have re-examined low mass planet migration in such an environment. I will present our new understanding and overview of the range of migration phenomenology that arise, and speculate about the consequences for the problem of the formation of planetary systems and the observable signatures of planet formation.
Our models unveil the critical role of vortices in determining the migration behaviour for partial gap-opening planets. Vortices form in pressure maxima at gap edges, and prevent the disc-feedback stopping of migration for intermediate planets in low viscosity and inviscid discs, contrary to the concept of the ‘inertial limit’ or ‘disc feedback’ halting. Vortices may also form in the corotation region, dramatically modifying migration behaviour. The migration of partial gap-opening planets clearly becomes non-deterministic for sufficiently low viscosities. At moderate viscosity, a smooth disc-feedback regime is found in which migration can slow, and the migration timescale observed corresponds to migration being driven by diffusive relaxation of the gap edges. Finally I will demonstrate the particle trapping driven by structures left in inviscid discs by a migrating planet, and show that particle traps in the form of rings and vortices can persist after the planet has passed, implying that the observation of particle traps by sub-millimeter interferometers such as ALMA cannot be used to infer the current presence of an adjacent planet.
42 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
T32: Friday, Mar 1, 12:15-12:30 Pfalzner, Susanne MPIfR Stellar fly-by possibly shaped the outer solar system
S. Pfalzner, A. Bhandare, K. Vincke, P. Lacerda
The growing knowledge about the outer solar system bodies provide new challenges to our understanding of the formation and early evolution of the solar system. In contrast to the planets, the transneptunian objects (TNOs) mostly move on inclined, eccentric orbits. This implies that some process restructured the outer solar system after its formation. As some TNOs move outside the zone of influence of the planets, external processes might have played an important part in structuring the outer solar system. Here we show that a close fly-by of a neighbouring star can simultaneously produce not only many of the TNO features but also the family of Sednoids, which are otherwise difficult to explain. In the past it was estimated that such close fly-bys are rare during the relevant development stage. However, our computer simulations show that such a scenario might be much more likely than previously assumed.
Talks on Friday, Mar 1 43 Rostock, Feb 27 - Mar 01, 2019
44 Talks on Friday, Mar 1 Planet Formation and Evolution 2019
Poster Session 1 Wednesday, Feb 27, 17:00
45 Rostock, Feb 27 - Mar 01, 2019
P101 Barraza, Marcelo Max Planck Institute for Astronomy Dust traps in the protoplanetary disc MWC 758: Two vortices produced by two giant planets?
Clement Baruteau and Marcelo Barraza et. al
Resolved ALMA and VLA observations support the existence of two dust traps in the spiral-bearing protoplanetary disc around the Herbig Ae star MWC 758. By means of 2D gas+dust hydrodynamical simulations post-processed with 3D radiative transfer calculations, we show that the spirals in scattered light, the asymmetric ring and the crescent-shaped structure in the (sub)mm can be caused by two giant planets: a Jupiter-mass planet at ∼33 au (inside the spirals) and a 5-Jupiter mass planet at ∼132 au (outside the spirals). The outer planet forms a dust-trapping vortex at the inner edge of its gap (at ∼80 au), where the compact continuum emission reproduces quite well the ALMA and VLA observations if assuming moderately porous dust particles (with an internal density of 0.1 g cm−3) up to a cm in size. It also triggers several spiral arms which can account for some of the spirals or arcs observed in polarised scattered light. The inner planet also forms a vortex at the outer edge of its gap (at ∼47 au), but it decays faster than the vortex induced by the outer, more massive planet as a result of the disc’s turbulent viscosity. The loss of azimuthal trapping due to the vortex decay can reproduce the low signal and larger spread observed in VLA observations of this dust trap. Finding the thermal and kinematic signatures of both planets could verify the proposed scenario.
P102 Birnstiel, Til LMU Munich Thermal Waves in Planet Forming Disks
Til Birnstiel, Kees Dullemond, Mat´ıasG´arate
In this poster, we investigate a thermal wave instability in planet-forming disks that is triggered by illumination and shadowing. We extend previous 1+1D models toward 2D flux limited diffusion to determine the amplitude of the waves under realistic conditions. The effect of these waves on dust dynamics and on observable properties of disks is discussed.
46 Poster Blitz 1 Planet Formation and Evolution 2019
P103 Bertrang, Gesa H.-M. MPIA Line polarization: The most direct tracer of magnetic fields in disks
Numerous numerical studies suggest that magnetic fields influence the transport of dust and gas, the disk chemistry, the meteoritic composition, the migration of planetesimals within the disk, and above all the accretion of matter onto the star. In short: Magnetic fields are crucial for the evolution of planet-forming disks. However, profound observational constraints are still pending. Recent studies show that the polarized continuum emission, the classical tracer of magnetic fields, might trace other physics instead (i.e., radiation field or dust grain size). The polarization predictions for these three different origins of polarization are not clearly distinguishable. I will present simulations of the most direct tracer of magnetic fields in disks: linearly polarized line emission, and give an outlook on how to disentangle the sources of continuum polarization with ALMA.
P104 Gressel, Oliver Magneto-thermal winds launched from weakly-ionized protoplanetary disks
Protoplanetary disks accrete onto their central T Tauri star viscously through turbulence and/or via large-scale coherent magnetic stresses extracting angular momentum from the disk. When the effect of ambipolar diffusion (AD) is included, and in the presence of a vertical magnetic field, the disk remains laminar between 1-5 AU, and a magnetocentrifugal disk wind forms that provides an important mechanism for removing rotational support of the disk material. We develop global MHD simulations of PPDs that include Ohmic resistivity, AD and ultimately the Hall effect, where the time-dependent gas-phase electron and ion fractions are computed under FUV and X-ray ionization with a simplified recombination chemistry. To investigate whether the mass loading of the wind is potentially affected by the limited vertical extent of our existing simulations, we attempt to develop a model for a realistic disc atmosphere. To this end, accounting for stellar irradiation and diffuse reprocessing of radiation, we aim at improving our models towards more realistic thermodynamic properties. In a further step, accounting for simplified FUV photo chemistry, we aim to derive abundances and, using the LIME code, ultimately observational tracers of such warm atomic/molecular winds.
Poster Blitz 1 47 Rostock, Feb 27 - Mar 01, 2019
P105 Hirsh, Kieran Centre de Recherche Astrophysique de Lyon Cavity Size in Circumbinary Discs
How does the cavity size of a circumbinary disc vary with disc and binary properties? We performed a suite of smoothed particle hydrodynamics (SPH) simulations of gas-only circumbinary discs in an attempt to answer this question. We found that there exists two timescales for cavity opening. A cavity is opened rapidly on the dynamical timescale (≤ 100 binary orbits). The size of this cavity increases for more eccentric binaries and is independent of disc viscosity. After the viscous timescale is resolved (' 10 000 binary orbits) the cavity size is seen to decrease as disc viscosity increases. This implies that binary and disc properties can be inferred from observations of cavities. In future work we will add dust to our simulations to investigate how the dust disc reacts to the same changes in disc and binary properties.
P106 Brunngr¨aber, Robert CAU Kiel Self-scattering in protoplanetary disks: the polarization reversal due to Mie scattering
The investigation of polarized light of protoplanetary disks is key for constraining the dust properties, disk morphology and the embedded magnetic field. However, different polarization mechanisms and the diversity of dust grain shapes and compositions lead to ambiguities in the polarization vector orientation. The so-called self-scattering of thermal, re-emitted radiation in the infrared and mm/submm is discussed as a major source of polarized light in various ALMA observations. It is commonly assumed that the polarization pattern produced by self-scattering are concentric rings for face-on orientations. With Mie theory of scattered light and full radiative transfer simulations we show that a flip of 90◦ of the polarization vectors may occure and mimic the typical pattern of dichroic emission of dust grains magnetically aligned by a toroidal magnetic field. Furthermore, this effect of polarization reversal is a fast changing function of wavelength and grain size, and thus a powerful tool to constrain grain composition and size distribution present in protoplanetary disks. In addition, the effect may also provide unique constraints for the disk inclination, especally if the disk is seen close to face-on.
48 Poster Blitz 1 Planet Formation and Evolution 2019
P107 Jung, Manuel Hamburg Observatory From Protostellar to Protoplanetary Discs – When do planetary embryos form?
M. Jung, R. Banerjee
All protostars are surrounded by a disc-like structure or a proper Keplerian disc. Those discs are essential to understand the subsequent evolution of the protostar and are most probably the nurseries of planets, apart from being the birthplaces of binary or multiple stellar systems. Nevertheless, it is fairly unknown how the discs, and hence the protostars are decoupled from the infalling envelope and molecular clouds. Therefore we execute self-consistent simulations with radiation feedback of protostars and discs which are still embedded in an accreting envelope to track their late evolution and the first steps of planet formation. For this we employ our in-house developed hybrid characteristics radiation transfer scheme for diffuse background radiation, which is build upon FLASH. Recently this solver has been extended to include the radiation of point sources. The point sources are modelled by sink particles coupled to a star formation evolution model. Therefore these young stellar objects can irradiate the surrounding disk and envelope. We present results from cloud core collapse simulations generating low mass stellar objects with radiation feedback. If a star particle is not yet formed or its mass is still below 0.1 M , the radiation field is composed of background radiation and by compression and shock heating. A dense, thick disk is generated on the smallest scales < 50AU, which is heated by accretion shocks parallel to the disk plane. On larger scales a flared accretion disk is formed. Later in the evolution of the protostellar disk, the star particle contributes significantly to the radiation field.
Poster Blitz 1 49 Rostock, Feb 27 - Mar 01, 2019
P108 Luppe, Patricia AIU, FSU Jena The Oddity of M-Star Planetary Systems: A Debris Disk Perspective
Patricia Luppe, Alexander Krivov
In many respects, M-star planetary systems differ from systems around earlier-type stars. They seem to contain different populations of planets, as many M-stars host Earth- to Neptune-mass planets but only a few harbor gas giants. Another peculiarity is related to debris disks around these cool stars. While during the last few decades many debris disks have been found and resolved around A to K-type stars, only a handful of them have been discovered around M-stars. The reasons for their paucity remain unclear. Here we check whether the sensitivity and wavelength coverage of present-day telescopes are simply unfavorable for detection of these disks or if they are truly rare. We approach this question by looking at different Herschel surveys that have searched for debris disks around M-type stars. Assuming that M-star disks are ”similar” to those of earlier type stars in some sense (i.e., in terms of dust location, temperature, fractional luminosity, or mass), we check whether these surveys should have found them. Examining integration times and sensitivities of the instruments used, we create detection limit plots for each of these surveys. We will present and discuss the implications of these results for the ”true” incidence rates of M-star debris disks and what they may tell us about formation of M-star planetary systems.
50 Poster Blitz 1 Planet Formation and Evolution 2019
P109 Manger, Natascha Max Planck Institute for Astronomy ALMA Vortex Signatures are Potentially Created by the Vertical Shear Instability
Natascha Manger, Hubert Klahr
Many protoplanetary disks observed by ALMA show dust concentrations consistent with particle trapping in giant vortices and zonal flows. The formation and survival of vortices is of major importance for planet formation, because vortices act as particle traps and are therefore preferred locations of planetesimal formation. Recent studies showed that the vertical shear instability (VSI) is capable of generating turbulence and small vortices in protoplanetary disks with realistic radial and vertical stratification and cooling properties.
We investigate the influence of the azimuthal extent of the disk on the long-term evolution of a protoplanetary disk and the possibility of large vortices forming. To this end, we perform 3- dimensional simulations for up to 1000 local orbits using different values of ∆φ = π/4 − 2π for VSI in disks with a prescribed radial density and temperature gradient cooling on short timescales.
We find the VSI capable of forming large vortices that can exist at least several hundred orbits in simulations covering a disc with ∆φ ≥ π. This suggests the VSI to be capable to form vortices or at least to trigger vortex formation via a secondary instability, e.g. Rossby wave instability or Kelvin–Helmholtz Instability. We also present post-processed images showing the capability of those vortices to trap particles and their signs in observed disks.
Poster Blitz 1 51 Rostock, Feb 27 - Mar 01, 2019
P110 Picogna, Giovanni Universit¨ats-Sternwarte der Ludwig-Maximilians-Universit¨atM¨unchen (USM - LMU) The dispersal of planet-forming discs. A new generation of X-ray photoevaporation models.
G. Picogna, B. Ercolano, L. W¨olfer,K. Monsch
The modality of disc dispersal is thought to be of fundamental importance to planet formation and evolution, yet the responsible mechanism is still largely unconstrained. Photoevaporation from the central star is currently a promising avenue to investigate, but the models developed to date do not yet have enough predictive power for a detailed comparison with the observations. We focus on creating new and improved hydrodynamical models of wind profiles from stellar irradiation at different wavelengths (EUV, X-rays) in order to have better constraints for current and future observations. We provide several fits of the total mass-loss rate as a function of stars X-ray luminosity and stellar mass, which can be used as simple prescriptions in population synthesis models of planet formation, as well as to produce line profiles within the wind for different disc inclinations. We find that the total mass-loss rate is increased by a factor 3 with respect to previous models and the X-ray photoevaporation can explain a larger fraction of observed transition discs. Although these differences seem small, they can significantly impact planet formation and their architecture. In particular, we test whether the rapid disc dispersal can break planet resonances explaining the observed population of multi-planetary systems.
52 Poster Blitz 1 Planet Formation and Evolution 2019
P111 Rab, Christian Kapteyn Astronomical Institute - University of Groningen The gas structure of the HD 163296 planet-forming disk - Gas gaps or not?
High spatial resolution observations have revealed stunning ring and gap features in the dust emission of several planet-forming disks, indicating that such features are quite common in disks around low and intermediate mass stars. Those gaps might trace ongoing planet formation, but also alternative theories for their origin exists (e.g. ice lines). Furthermore, it is not yet clear to what extent the gas follows the dust distribution; i.e. are the dust gaps also depleted in gas? One example of such a gap/ring disk is the massive disk around the 5 Myr old Herbig Ae/Be star HD 163296. The dust disk was modelled in detail by Muro-Arena et al. (2018), using high spatial resolution ALMA and SPHERE images, which provide strong constraints for both the large and small dust grain population. On top of this azimuthally symmetric dust disk model, we model the gas structure using the 2D radiation thermo-chemical disk code ProDiMo (PROtoplanetary DIsk MOdel). We calculate besides the dust temperature also consistently the gas temperature, the chemical abundances and the resulting spectral line emission. We show the impact of dust gaps on the gas temperature and chemistry and discuss to what extent a depletion of the gas inside the dust gaps is required to explain already available CO gas observations. Furthermore, we show what kind of observations are needed to better constrain the gas density in the gaps (e.g. the gap width). Such models, combined with high-quality observational data, provide crucial information for planet formation theories and constraints for the various proposed dust gap formation models.
Poster Blitz 1 53 Rostock, Feb 27 - Mar 01, 2019
P112 Schulik, Matthaeus Lunds Observatory Accreting gas giants in 3D - New results from radiation hydrodynamics
Schulik M., Bitsch B., Lega E., Johansen A.
Gas accretion onto planetary cores is presumably a fundamental process to form gas giant planets. In its full complexity this process remains not well understood. In order to approach a better understanding of the gas accretion process, we perform radiation hydrodynamics simulations. Those simulations allow us to study the interplay of gas flows and density/temperature structures in the gaseous envelopes of accreting giant planets. We use constant as well as complex opacity functions as cooling parameters for the planetary envelopes. Analysis reveals weak differences in accretion rates but significant differences in gas flows through these envelopes when comparing simple and complex opacities. Here we present an overview of this analysis as well as some interesting results from our set of simulation runs, and address the question of how to map our results into realistic accretion rates.
P113 Rometsch, Thomas Universit¨atT¨ubingen Are transition disks formed by planetary systems?
Thomas Rometsch, Prof. Dr. Wilhelm Kley
Transition disks are protoplanetary disks showing large inner holes or very wide gaps in mm observations. Possible scenarios for their formation have been discussed in the literature including photoevaporation and presence of embedded planets. In this work, we extend previous studies and investigate the possibility of forming transition disks with more than one embedded planet. For this, we use 2D hydrodynamic simulations including radiative processes and dust dynamics. We are especially interested in possible emerging structures such as rings and spirals which might be observed in radio or scattered light images. We also measure the dependence of the accretion rate onto the central object on the properties of the planetary system.
54 Poster Blitz 1 Planet Formation and Evolution 2019
P201 Savvidou, Sofia Max-Planck-Institute for Astronomy Thermal structures of inner protoplanetary discs
Savvidou S., Bitsch B., Lambrechts M.
The thermal structure of protoplanetary discs is regulated by their dust content and the opacity that dust grains provide. Therefore it is important to investigate the effect grain growth has on the disc structure.
We use 2D hydrodynamical simulations coupled to a new opacity model that calculates the opacity as a function of temperature for a dust population taking into account the particle size, composition and abundance. We compare simulations utilizing single grain sizes to two different multi-grain size distributions at different levels of turbulence strengths, parameterized through the α-viscosity. In the first grain size distribution, the number density follows an MRN power-law. The second one begins with the same mass distribution, but takes into consideration the relative velocities for particles of different sizes and gives different slopes for the mass distribution depending on the particle sizes and their aerodynamical properties.
I will present the first results from this work and discuss how we then use the aforementioned simulations to study the thermal structure of protoplanetary discs and how it affects the evolution of the iceline. Additionally, I will discuss the implications of the iceline location to planetesimal formation and planet migration.
Poster Blitz 2 55 Rostock, Feb 27 - Mar 01, 2019
P202 Sch¨afer,Urs Hamburger Sternwarte, Universit¨atHamburg Streaming Instability and Vertical Shear Instability in Global Simulations of Protoplanetary Disks
Sch¨afer,Urs; Banerjee, Robi; Johansen, Anders
The streaming instability drives turbulence in protoplanetary disks, which can lead to strong clumping of dust grains. As these clumps can collapse and form planetesimals, the streaming instability is a promising path to form planetesimals from dust grains. We study this instability in global numerical simulations of dust and gas, including mutual drag interactions between the two species as well as both radial and vertical stellar gravity, with the largest domains to date. The domains of our two-dimensional simulations span radii from 1 au to 100 au, with their vertical dimension being determined by the gas scale height. In addition to the streaming instability, we find that in our simulations another instability plays a crucial role in driving the dust dynamics: the vertical shear instability. We investigate the dust dynamics governed by the interplay of those two instabilities.
P203 Sende, Jan AIU Jena Planets induce a size dependency in the particle distribution of evolved debris disks
J. A. Sende and T. L¨ohne
Context: Observations and evolution models suggest that planets form early in protoplanetary disks and should therefore be found in debris disks as well. Planets around stars are hard to detect, however increasingly more high-resolution images of debris disk are available. Aims: To constrain/detect possible planets, we aim to find observable features in the evolution of debris disks under the gravitational influence of possible planets. Methods: We combine the collisional evolution of particles inside a debris disk with the gravitational perturbing influence of a single planet. In addition to theoretical approximations, we investigate collisions and perturbations by integrating an example debris disk, using a modified version of our collisional code ACE. Results: We find that the distribution of orbital elements in the disk is strongly size dependent for small particles. This leads to observable differences between the big grains in the debris disk belt and the small grains in the halo: observations at different wavelengths can be used to constrain the properties of a possible planet.
56 Poster Blitz 2 Planet Formation and Evolution 2019
P204 Woelfer, Lisa Max-Planck-Institute for extraterrestrial physics (MPE) Thermal and Hydrodynamical Simulations of X-ray photoevaporation in metal depleted circumstellar discs
M.Sc. Lisa W¨olfer,Dr. Giovanni Picogna, Prof. Dr. Barbara Ercolano
Detailed knowledge of protoplanetary disc evolution and dispersal is crucial for the understanding of the formation and evolution of planetary systems. Therefore, special interest lies in the study of so-called transition discs, which show evidence for (at least) inner dust cavities and often simultaneous gas accretion onto the central star. Often seen as living on the edge of dispersal, transition discs provide a strong tool to probe various mechanisms that might matter during disc evolution. One of these mechanisms is photoevaporation which can in general explain the occurrence of transition discs. In our work we explore the possibility of X-ray photoevapora- tion, operating in discs with gas phase depletion of carbon and oxygen at outer radii, to explain most observables without the need to invoke giant planet formation. As carbon and oxygen are the main contributors to the X-ray opacity, a depletion of these gases leads to a larger penetration depths of X-ray radiation in the disc and results in higher gas temperatures and stronger photoevaporative winds. We present radiation-hydrodynamical models of discs irradiated by internal X-ray+EUV radia- tion assuming gas phase depletions of factor 3,10 and 100 in order to derive realistic mass loss rates and profiles. Our analysis yields robust temperature prescriptions and promising mass loss rates and profiles which will likely be able to explain a large fraction of the observed diversity of transition discs.
Poster Blitz 2 57 Rostock, Feb 27 - Mar 01, 2019
P205 Zormpas, Apostolos LMU, Munich Planet formation hotspots in Transition Disks
Apostolos Zormpas, Til Birnstiel
We study the growth and the dynamics of dust and planetesimals in pressure bumps. Performing 1-D simulations and adding an axisymmetric stationary pressure bump, we find the accretion rate of dust particles into the pressure bump and the size distribution of the particles entering it. Using parameterized models of planetesimal formation (Drazkowska & Dullemond 2014), we calculate how much dust is transformed into planetesimals, to study the effectiveness of planetesimal formation and the evolution of the dust-to-gas ratio in pressure bumps. Moreover, we expect to use pressure bumps with finite life time and improve upon previous works (e.g. Pinilla et al. 2012a). By comparing with observational data, we plan to constrain bump amplitudes, bump sizes and life times, initial conditions on alpha, disk mass, characteristic radius and fragmentation velocity, consistent with recent surveys of protoplanetary disks in dust continuum and with observed dust disk life times. This will allow us to investigate the efficiency of particle trapping in time-dependent pressure maxima and their possible relation to type-1 transition disks. This way, we plan to evaluate which mechanisms could be at play in forming and shaping dust traps based on their life times or amplitudes.
P206 Bila, Tetyana University of Duisburg-Essen Erosion of planetesimals through small atmospheric pressure excursions
G. Wurm, J. Teiser, T. Bila
It has been suggested that on Mars dust can be lifted due to a ∆p-effect caused by dust devils. A few Pa pressure drop should be sufficient to lift dust against gravity. If so, this effect should also be applicable to erode planetesimals in protoplanetary disks. We did set up an experiment to generate low pressure differences and indeed find that dust from layers of 100 µm thickness can be lifted against gravity starting at 2 Pa. Lift is mostly limited by cohesion and low cohesive small (proto)-planetary bodies might be eroded at protoplanetary disk conditions.
58 Poster Blitz 2 Planet Formation and Evolution 2019
P207 Franz, Raphael LMU Munich Dust Entrainment in Photoevaporative Winds
R. Franz, G. Picogna, B. Ercolano
Photoevaporation by high energy radiation from the central star is potentially a crucial mechanism for disc evolution, affecting both the gas and dust distribution. We have modelled, in 2.5D, the protoplanetary gas disk of a young T-Tauri star, irradiated by an X(EUV) spectrum, until a quasi-equilibrium state is reached. On top of this disk, we then insert dust grains of various sizes, represented by passive Lagrangian particles, starting close to the sonic surface of the disk. This allows us to determine the dust trajectories in the disc wind. To our knowledge, this is the first time that both the X-ray and EUV components of the wind have been taken into account when considering dust; besides, current models of dust entrainment mostly rely on computationally much less expensive semi-analytical approaches, for which our results may provide a valuable benchmark.
As expected, we encounter either full entrainment in the wind, pick-up and re-deposition, or infall towards the star, depending on the size and initial position of the dust grains; furthermore, we derive tentative predictions for the dust grain sizes entrained in the wind dependent on their distance from the central star, which may be used both as an input into opacity models for astrochemical disk simulations, and to better constrain observational results for gas-to-dust ratios and mass flux rates.
P208 Garate, Matias University Observatory Munich Dust accretion preceding an outburst. The case of RW Aur dimmings.
Matias Garate, Til Birnstiel, Sebastian Markus Stammler, Hans Moritz Gunther
RW Aur has presented multiple dimming events in the last decade. Observations indicate than a screen of dust in the line of sight is blocking the starlight, and that high concentrations of hot dust grains are present in the inner regions of the accretion disk. We propose a mechanism that can increase the accretion of dust through the reactivation of the turbulence in a dead zone. Our simulations show that in less than a decade the accretion of dust can increase by orders of magnitude, providing the material required to cause the dimming events. If the dimmings are caused by the dead zone reactivation mechanism, then our model also predicts a rise in the gas accretion rate for the following years.
Poster Blitz 2 59 Rostock, Feb 27 - Mar 01, 2019
P209 Lenz, Christian Max Planck Institute for Astronomy Pebble Flux regulated Planetesimal Formation
C. Lenz, T. Birnstiel, & H. Klahr
How are the building blocks of planets radially distributed in disks? How does this distribution change with time? Can we use these results in order to exclude certain disk parameters for the Solar Nebula? To answer these questions, we propose an analytic expression for a local planetesimal formation rate proportional to the instantaneous radial pebble flux. The result of planetesimals distributed over the disk can be used as initial condition for planetesimal synthesis or N-body simulations toward the formation of planetary embryos. The idea is that it needs particle traps to locally enhance the dust-to-gas ratio sufficiently that particle gas interaction (streaming instability, Kelvin-Helmholtz instability or more general turbulent diffusion) can no longer prevent planetesimal formation on small scales. The location of these traps (vortices and zonal flows) can be everywhere in the disk. They are expected to be products of magnetohydrodynamical and hydrodynamical instabilities in a disk around a young star. Their occurrence and lifetime is subject of ongoing research, thus they are implemented via free parameters similar to the alpha-ansatz for turbulent viscosity. Based on our model, we can already show that large alpha-values of 0.01 (strong turbulence) do prevent the formation of planetesimals in the inner part of the disk, arguing for lower values of 0.001 (moderate turbulence), at which planetesimals do form quickly at all places where they are needed for rocky and icy proto-planets. Planetesimal formation starts as soon as dust has grown to pebbles and the pebble flux reaches a critical value, which is after a few thousand years at 2-3 AU and after a few hundred thousand years at 20-30 AU. Planetesimal formation lasts for a few million years, after which the supply of pebbles has decreased below a critical value. Interestingly, a consequence of our model is to have the final planetesimal column density distribution to be steeper than the initial dust and gas distribution in the disk, an effect that helps to explain the discrepancy of the minimum mass solar nebula and viscous accretion disks.
60 Poster Blitz 2 Planet Formation and Evolution 2019
P210 Loehne, Torsten AIU Jena How submillimetre wavelengths reflect grain size distributions in circumstellar discs
Torsten Loehne, Harald Mutschke
The excess emission seen in spectral energy distributions (SEDs) is commonly used to infer the properties of the emitting circumstellar dust. Most notably, dust size distributions and details of the collision physics are derived from SED slopes at long wavelengths. We review the basic underlying models and approximations, showing when they are appropriate and when and how they fail. In addition, we discuss the roles of porosity and of optical properties that vary with grain temperature. We conclude that simple analytic approximations are misleading, suggest refined relations, and argue for more detailed models.
Poster Blitz 2 61 Rostock, Feb 27 - Mar 01, 2019
P211 Ndugu, Nelson Max Planck Institute for Astronomy, Heidelberg, Germany, Mbarara University, Uganda Planet population synthesis : core growth via pebble accretion
Nelson Ndugu, Bertram Bitsch, Edward Jurua
In the core accretion paradigm, the core grows first and can then, if it becomes massive enough, accrete a gaseous envelope to become a gas giant. The original planetary seeds of Moon to Mars mass can grow in the disc either via pebbles or planetesimals. Pebble accretion onto cores is mostly a faster process than accretion via planetesimals. The core accretes pebbles until the pebble isolation mass is reached, where pebble accretion stops and gas accretion can start. During the entire phase of planetary growth, planets interact with their natal protoplanetary disc and undergo orbital evolution. Low mass planets move in the fast type-I migration, while undergoing pebble accretion and slow gas contraction. Massive planets undergo slower type-II migration after carving a gap in the disc. Sampling the initial conditions of disc and planet formation and evolution, a synthetic populations of planet is computed. Planet population synthesis is a numerical tool through which planet formation theories are linked to the observed planet population. Previous planet population syntheses via core accretion utilized planetesimal accretion for the formation of the core (Ida & Lin., 2004, Ida & Lin., 2008a,b, Mordasini 2009a,b). Ndugu et al. 2017 presented the first planet population synthesis simulations utilizing pebble accretion. Additionally we investigate the influence of the outer disc structure on the giant planet formation rate and compare the results to observations. In our study, cold Jupiters mainly originate from the outer disc, while hot Jupiters form in the inner regions of the disc. Hotter outer discs result in a lower giant planet formation rate more consistent with observations in our model. Additionally our model shows that a frequency of super-Earths of 30-50%, in agreement with observations, can be achieved, if planetary seeds start closer to their host star. We additionally expand on the original work by Ndugu et al. 2017 and include more advanced recipes for type-I (e.g. dynamical corotoation torques, Paardekooper 2014) and type-II migration rates (e.g. Robert et al. 2018, Kanagawa et al. 2018) as well as gap opening and gas accretion recipes (Crida & Bitsch, 2017) to obtain populations of planets, which we also compare to observations.
62 Poster Blitz 2 Planet Formation and Evolution 2019
P212 Pawellek, Nicole Max-Planck-Institut f¨urAstronomie Clinging dust grains - Planetesimal belts are not only traced at long wavelengths
N. Pawellek, I. Pascucci, A. Moor, A. Krivov
Debris discs are dusty belts of Planetesimals around main-sequence stars, similar to comets and asteroids in the solar system. The planetesimals themselves cannot be observed directly, yet they produce detectable dust in mutual collisions. Observing this debris dust, we can try to infer properties of invisible planetesimals. Here we address the question of what is the best way to measure the location and extent of outer planetesimal belts, i.e., ”Kuiper belts” that encompass extrasolar planetary systems. A standard method is using resolved images at millimetre wavelengths, which reveal dust grains of comparable sizes. This is because smaller dust particles seen in the infrared or optical are subject to a large array of non-gravitational forces that drag them away from their birth places, and so may not closely trace the parent bodies. In this study, we examine whether imaging of debris discs at shorter, far- or even mid-infrared, wavelengths with future facilities such as the James Webb Space Telescope, which offer high resolution, would allow one to determine the spatial location of the exo-Kuiper belts with sufficient accuracy. We find that around A-type stars, where the majority of debris discs is found, and even around G-type stars discs are brightest at the location of the birth ring in both the millimetre and the mid-infrared wavelength bands. Thus, we are able to trace planetesimal belts even at shorter wavelengths.
Poster Blitz 2 63 Rostock, Feb 27 - Mar 01, 2019
P213 Sch¨afer,Urs Hamburger Sternwarte, Universit¨atHamburg Initial Mass Function of Planetesimals Formed by the Streaming Instability
Sch¨afer,Urs; Yang, Chao-Chin; Johansen, Anders
The streaming instability is a promising mechanism to overcome the barriers impeding the growth of dust grains to planetesimals by concentrating the grains into overdense filaments that undergo gravitational collapse and form planetesimals. However, the dependence of the resulting planetesimal initial mass function on the domain size of numerical simulations remains unclear. To resolve this, we conduct local shearing box simulations with the largest domain dimensions to date, allowing us to study the simultaneous formation of planetesimals in multiple well separated filaments that can only emerge within such large domains. In our simulations, planetesimals with sizes between 80 km and several hundred kilometers form. We find that their cumulative birth mass distribution at the high-mass end is well-represented by a rather shallow exponential cutoff, and that the characteristic mass scale of this cutoff correlates with the mass budget in each filament. Together with previous studies of high-resolution simulations with small box domains, our results imply that the cumulative birth mass function of planetesimals is consistent with an exponentially tapered power law with a power-law exponent of approximately -1.6 and a steepness of the exponential cutoff in the range of 0.3–0.4.
64 Poster Blitz 2 Planet Formation and Evolution 2019
P301 Forgacs-Dajka, Emese E¨otv¨osLor´andUniversity, Budapest, Hungary Application of method FAIR to identify mean motion resonances in the Kuiper belt
E. Forg´acs-Dajka and Zs. S´andor
Mean motion resonances (MMRs) play an important role in shaping the dynamics of the planetary and the Solar system bodies. MMRs in the Solar system usually occur between a planet and small bodies, e.g. the members of the Hilda group of asteroids are in a 3:2, while the Trojan asteroids are in a 1:1 MMR with Jupiter. MMRs between terrestrial planets and particular members of the asteroid family Hungaria can also be found. The existence of the Kirkwood gaps clearly indicates, the dynamical structure of the main belt is shaped by the MMRs between the asteroids and Jupiter. There are many Kuiper belt objects that are locked in various MMR with Neptune, such as the plutinos sharing their orbits with Pluto. Based on the geometrical meaning of the resonance variable, an efficient method has been introduced and described in our recent paper (Forg´acs-Dajka, S´andor& Erdi,´ 2018), by which mean motion resonances can be easily find without any a priori knowledge on them. The efficiency of this method - named FAIR - is clearly demonstrated by using known exoplanets engaged in mean motion resonances, and also some members of different families of asteroids and Kuiper belt objects being in mean motion resonances with Jupiter and Neptune, respectively. In this research we systematically apply the method FAIR to the Kuiper belt objects to identify the dynamically relevant MMRs between them and Neptune or Uranus. Our investigation may help to find possible new families of Trans Neptunian Objects in resonance with the outer gas giants.
P302 Singh, Chamkor Max-Planck Institute for Dynamics and Self-Organization Goettingen Hydrodynamics around aggregating charged grains
Chamkor Singh, Marco G. Mazza
The growth of protoplanetary dust from sub-millimeter sized particles to much larger scales is not well understood. There is considerable debate about the role of electrostatic charging of grains in the aggregation process. Additional complexity arises due to the presence of complex hydrodynamic flow that couples to the aggregating grains. We study this growth process using massively parallel molecular dynamics simulations for the granular particles in combination with the smoothed-particle-hydrodynamics for the interstitial flow. The results from a detailed cluster analysis are presented. Finally we propose an effective kinetic model for the charged grain aggregation inside interstitial flow.
Poster Blitz 3 65 Rostock, Feb 27 - Mar 01, 2019
P303 Vericel, Arnaud Centre de Recherche Astrophysique de Lyon Dust growth in the SPH code PHANTOM
Arnaud Vericel, Jean-Fran¸coisGonzalez
For the last few decades, planet formation theory has been struggling to explain how planets form from micrometer dust grains sticking together. This statement is particularly stunning since tons of exoplanets are discovered every year in the Galaxy. To better understand this formation process, one needs 3D and self-consistent numerical simulations modelling the coupled evolution of gas and dust in a protoplanetary disk. In this regard, we use the newly released Smoothed Particles Hydrodynamics (SPH) code PHANTOM (Price et al. 2018), in which we implemented a dust growth algorithm. I will present this implementation as well as how it can be useful for planet formation studies through a few examples.
P304 Weber, Philipp Niels Bohr International Academy Copenhagen Size-dependent dust filtration induced by the presence of a giant planet
Philipp Weber, Pablo Ben´ıtez-Llambay, Oliver Gressel, Martin Pessah, Leonardo Krapp, Troels Haugbølle, Daniel Wielandt, Martin Bizarro
As is well-known, the presence of a giant planet modifies the gas structure in a way, that it creates a gap in density at its orbital location. How strongly the radial motion of dust grains gets affected by this modification depends maily on the grains’ Stokes number, and therefore on their size and the local gas density. We find that for a certain disk model there is a critical particle size, above which grains are not efficiently transported through the planet’s gap and start to pile up at the outer edge of the gap. We discuss consequences of this size-dependent filtration and in case of the Solar System we propose a method to test the idea through laboratory measurements. Finally, we present first results of this exploration. The comparison of laboratory measurements with theoretical predictions of several models might give us constraints on important disk parameters in the early Solar System.
66 Poster Blitz 3 Planet Formation and Evolution 2019
P305 Ali-Dib, Mohamad IREX / University of Montreal Protoplanet growth stalling via dust convective overshooting
Mohamad Ali-Dib and Christopher Thompson
We use a new self-consistent model for the evolution of accreting protoplanets envelopes to identify a bottleneck in planet formation. In this model, pebble accreted onto the protoplanet are destroyed soon after they enter the envelope, increasing the density of very small grains, since most of the collisions are in the destructive regime leading to a small average dust size. The augmentation in grain density increases the opacity, thus pushing the convective-radiative boundary outward till it reaches the Hill radius. At this point, convective-overshooting at the Hill radius will eject the dust outside of it. These particles are lost permanently and just their ejection rate regulate the total solid mass of the envelope. We find that the mass lost rate due to dust overshooting outside of the convective Hill radius is comparable to the pebble accrete rate, thus leading to a stall in the growth, where the total mass of all elements in the envelope plateau to a low value, stalling the planet growth entirely. Ali-Dib, M. & Thompson, C. (2018)
P306 Baehr, Hans Max Planck Institute for Astronomy Formation of Cores in the Fragments of Self-Gravitating Disks
Hans Baehr, Hubert Klahr
Recent measurements of Jupiter suggest that gas giant planets have considerable solid cores. Planet formation by gravitational instability, unlike core accretion, is essentially a star formation process resulting in objects which more closely resemble stars in composition. This is further complicated by the high temperatures at the center of gas giant planets, which may inhibit the concentration of material into a core. While silicates will evaporate at temperatures around 1300 K, this does not mean solids and heavier elements cannot concentrate through aerodynamic and self-gravitational forces before the core temperature of the fragment becomes too hot. We perform high-resolution local simulations of fragmenting disks showing the sedimentation and concentration of particles at the formation of a fragment can lead to the enrichment of the planetary atmosphere if not the development of a sizable core. This indicates that all directly observed planets should have polluted/enriched atmospheres and potentially cores regardless of how they are formed.
Poster Blitz 3 67 Rostock, Feb 27 - Mar 01, 2019
P307 Elbakyan, Vardan Southern Federal University Gravitational fragmentation and formation of giant protoplanets on orbits of tens of AU
Elbakyan, Vardan G.; Vorobyov, Eduard I.
Planets form in gaseous and dusty disks around young stars. A possible scenario for giant planet formation is disk gravitational instability and fragmentation. We use high-resolution grid-based numerical hydrodynamics simulations to compute the formation and long-term evolution of gravitationally unstable protostellar disks around solar-mass stars. We show that gaseous fragments that have formed in the outer regions of a protostellar disk (> 100 AU) through disk fragmentation may later become perturbed by other fragments or disk structures, such as spiral arms, and quickly migrate toward the central star (during a few 103-104 years). During inward migration, the fragments first gain mass (up to several tens of Jupiter mass), but then quickly lose most of it through tidal torques when approaching the star. Part of the lost material can be accreted on the central star causing an FU-Ori-type luminosity outburst. This mass loss, or tidal downsizing, helps the fragments to halt their inward migration at a distance of a few tens of AU. The resulting fragments are heavily truncated both in mass and size compared to their wider-orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the central temperature in these fragments may exceed the molecular hydrogen dissociation limit (∼2000 K) and the central region of the fragment can collapse into a gas giant protoplanet. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and inward fragment migration, ushering the formation of giant protoplanets in the inner parts of protostellar disks.
68 Poster Blitz 3 Planet Formation and Evolution 2019
P308 Bischoff, Richard Astrophysical Institute and University Observatory Jena Follow-up observations of YETI planet candidates
Bischoff, Mugrauer, Neuh¨auserand the Yeti team
While most exo-planets are Gyr old, including in particular transit planets, it would be best to study planet formation and early evolution with young planets. Young transit planets have the advantage that mass and radius would be known (together with age and distance of their association). We search for young transit candidates in the Young Exoplanet Tansit Initiative with 1-meter telescopes around the world by monitoring young clusters. After CVSO 30b in the 25 Ori association, we have found 3 more candidates in the clusters IC 348, NGC 7243 and Trumpler 37. All targets are a few Myr young and showing transits in R-band. However, such dips can also be generated by other phenomena, e.g. eclipsing binary stars or grazing eclipses in the large optical PSF. This can only be excluded by follow-up observations like multi-band photometry, AO imaging in the IR and spectroscopy. In this talk we would like to present the first results of our observations of the transit planet candidates.
P309 Moldenhauer, Tobias University of T¨ubingen The Influence of the Headwind on Planetary Proto-Atmospheres
Protoplanets formed by core accretion can become massive enough to be able to accrete gas from the disk they are born in. If the planetary proto-atmosphere exceeds a critical mass, runaway gas accretion starts and the planet collapses into a gas giant. In recent years, many close-in super-Earths have been observed which raises the question on how they avoided becoming hot Jupiters. We use three-dimensional radiation-hydrodynamics to simulate the proto-atmosphere in the local frame around the planet. This work is focused on the importance of the headwind experienced by the planet due to the pressure gradient in the disk. Previously, this headwind had not been considered in simulations. Our preliminary results show that the headwind does not significantly affect the density of the proto-atmosphere. However, it strongly modifies the flow pattern of the gas outside of the Bondi sphere.
Poster Blitz 3 69 Rostock, Feb 27 - Mar 01, 2019
P310 Mugrauer, Markus Astrophysical Institute and University Observatory Jena Search for (sub)stellar companions of T Tauri stars in the Lupus star forming region
M. Mugrauer, N. Vogt, C. Ginski, R. Neuh¨auser
We have carried out a high contrast imaging search for (sub)stellar companions of young pre-main sequence stars in the Lupus star forming region. For this long-term project we have used the adaptive optics imager NACO/VLT, operated at the ESO’s Paranal observatory in Chile. Here, we will present the results of our survey. In several observing campaigns we could take deep diffraction limited IR imaging data and have detected faint co-moving companions of the observed T Tauri stars, whose astrometry (angular separations and position angles), as well as photometry could accurately be determined in all observing epochs. The co-moving companions found in our survey exhibit angular separations between about 0.1 up to a few arcsecs, which corresponds to projected separations between about 10 up to a few hundreds of au, at the average distance of our targets of about 140pc. Beside many new binary and triple star systems, whose multiplicity was revealed in our survey, also faint co-moving companions in the substellar mass regime could be detected close to some of our targets.
P311 W¨ockel, David Th¨uringerLandessternwarte Tautenburg Echelle´ Spectroscopy and Analysis of Mascara-1b, an Extremely Hot Exoplanet Orbiting an A-star
D. W¨ockel, E. W. Guenther, A. P. Hatzes
Only very little is known about close-in planets of stars with effective temperatures above 6000 K. This is very unfortunate, because such planets are highly irradiated and thus affected by atmospheric escape. Because these planets receive so much radiation from the host star, they are expected to be very hot. Planets with temperatures higher than 2000 K do not exist in our solar system, and only very few of them in other systems have been studied up to now. We thus do not know, if the albedo of these planets is as low as for close-in gas-giants of lower temperatures. It could well be, that their albedo is much higher. Because of the large rotation velocity of A-stars, the detection of planets in the spectrum is more challenging than a detection of planets of cooler stars. In order to find out the limit, we obtained 114 spectra of Mascara-1 with a S/N of about 150 with the Alfred-Jensch telescope in Tautenburg. We developed a special method to detect such planets. Using this method we could show that the detection is only limited by the signal-to-noise ratio of the spectra. Using this method, we derive an upper limit for the brightness of the planet in the optical regime of 0.1% of the stellar flux, consistent with the expectations.
70 Poster Blitz 3 Planet Formation and Evolution 2019
P312 Krieger, Anton Kiel University Characterization of young accreting planets
Anton Krieger, Sebastian Wolf
We study observational quantities which allow constraining the prevalent physical conditions in the immediate environment of protoplanets during the final stage of their formation. For this purpose we design an analytic model for a protoplanetary disk (PPD) harboring an accreting planet inside a carved gap. The process of accretion onto the planet leads to a conversion of kinetic energy of the infalling matter into radiative energy. A fraction of this energy is then radiated off the planet and serves as a heating source for its environment. Using the Monte-Carlo radiative transfer code Mol3D (Ober et al. 2015) we produce precise temperature and intensity maps assuming our description for a PPD as well as luminosities obtained by simulated planetary accretion shocks (Marleau et al. 2017). In a final step we apply the CASA simulator to obtain realistic high-angular resolution ALMA observations. By considering a wide range of parameters of protoplanetary disks, embedded planets and accretion rates we determine the observational accuracy needed to constrain selected properties of protoplanets and their environment. Eventually, we plan to evaluate the feasibility of observing PPDs and the process of accretion onto protoplanets using existing further state-of-the-art instruments (e.g., MATISSE, SPHERE) as well as future observatories/instruments (e.g., JWST, ELT).
Poster Blitz 3 71 Rostock, Feb 27 - Mar 01, 2019
Poster Session 2 Thursday, Feb 28, 17:00
72 Planet Formation and Evolution 2019
P401 Bogdan, Tabea University of Duisburg-Essen Constraints on Compound Chondrule Formation from Laboratory High Temperature Collisions
Tabea Bogdan, Jens Teiser, Maximilian Kruss, Gerhard Wurm
We carried out laboratory collision experiments with heated 1 mm glass and basalt spheres falling onto a flat glass target at about 1 m/s. Together with supporting heating experiments we found, that on a timescale of hours basalt grains form compounds only above 1400 K but fuse together completely at 1500 K. This puts constraints on compound chondrule formation and resulting particle densities in the solar nebula.
P402 Kobsch, Anais CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon Critical point of feldspars
Anais Kobsch, Razvan Caracas
It is commonly accepted that a Giant Impact between two large planetary embryos have formed a large debris disk, which subsequently led to the formation of the Earth and Moon couple upon cooling and accretion. One of the most important parameters in modeling the impact is the position of the thermodynamic boundaries. Because of experimental difficulties few studies were done on the evaporation of silicates and none on feldspars, which are the most abundant minerals in the Earth and Moon crusts. Here we work on the three feldspar end-members, KAlSi3O8, NaAlSi3O8, and CaAl2Si2O8. We use ab initio molecular dynamics to investigate the liquid/vapor equilibrium curve and to identify the position of the supercritical point. We sample numerically a wide range of temperatures and pressures: from 3000 to 7000 K and from 1.1 to 6.4 g/cm3, which cover the liquid side of the liquid-vapor dome and the position of the critical point. We identify the pressure – density – temperature conditions for the spinodal decomposition of the liquid – the point at which the liquid becomes unstable. We monitor the structure of the fluid, the atomic coordination and speciation, and compare the results obtained over the entire pressure and temperature ranges for the three end-members. Lasting voids with small clusters of atoms inside are clearly visible in the simulations at low densities, indicating a two-phases region, with gas bubble nucleation. The very first gas species formed during evaporation are identified and give new insight on the un-congruent evaporation of silicates. This research is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement n◦681818 – IMPACT). We acknowledge access to the GENCI supercomputers (Occigen and Ada) through the stl2816 series of eDARI computing grants.
Poster Blitz 4 73 Rostock, Feb 27 - Mar 01, 2019
P403 Krause, Corinna University Duisburg-Essen Collision experiments with hot dust related to planetesimal formation in inner disks
Corinna Krause, Tunahan Demirci, Jens Teiser, Gerhard Wurm
We set up and carried out novel experiments to study the slow collisions of hot dust aggregates. Particles (basalt) were heated up to 1100 K and levitated on a laser beam at low pressure. The collisions show an increasing sticking probability starting at about 900 K. In application, the size of aggregates before bouncing prevails might be shifted in the warm inner regions of disks.
P404 Landeck, Wolf Alexander IGeP, TU Braunschweig Collisions between centimeter-sized water-ice aggregates
W. A. Landeck, J. Blum
Water is one of the most abundant molecules in space. Therefore, it is interesting to investigate, how planet formation and evolution was influenced by the presence of water ice beyond the snow line.
In our experiment, we investigate collisions between centimeter-sized water-ice aggregates, which themselves are composed of micrometer-sized spherical water-ice particles, at velocities between 1 m/s and 10 m/s. The major goal of our experimental campaign is to derive the ∗ critical specific fragmentation energy QD. The first results of this investigation are that at 10 m/s, the water-ice aggregates fragment catastrophically, i.e. the largest remnant has a mass much smaller than half the original aggregate mass. In this respect, the experiments with water-ice aggregates show a similar result as those with silica aggregates (Bukhari et al. 2017). Fragmentation seems to be governed by the tensile strength of the material, because silica and water-ice possess also very similar strength values (Gundlach et al. 2018).
The results of this work will be incorporated into model calculations of debris disks as part of the Research Unit “Debris Disks in Planetary Systems”.
74 Poster Blitz 4 Planet Formation and Evolution 2019
P405 Schneider, Niclas University of Duisburg-Essen Approaching Drag Instabilities in Laboratory Experiments
Niclas Schneider, Gerhard Wurm, Jens Teiser, Hubert Klahr, Vincent Carpenter
Drag instabilities are an important particle concentration mechanism in protoplanetary disks but the idea is solely based on numerical simulations so far. We carried out first experiments to approach these mechanisms in laboratory studies. We observed a particle cloud trapped in a rotating system under Earth’s gravity. The experiment Stokes number is 0.014. For average dust-to-gas ratios up to 0.08 particles behave like individual test particles. For larger dust-to-gas ratios the motion of particles gets sensitive to particle density and interparticle distances. Overall, our experiments are a first study to get insights on the transition from undisturbed to collective particle behaviour.
P406 Tahir, Naeem GSI Darmstadt Application of Intense Ion Beams to Generate Planetary Core Conditions in the Laboratory
N.A.Tahir, A.R.Piriz, I.V.Lomonosov, A.Shutov, P.Neumayer, V.Bagnoud and S.A.Piriz
This talk discusses the possibility of employing intense particle beams to generate in the laboratory, the extreme physical conditions that exist in the planetary interiors. Detailed numerical simulations have been carried out using the beam parameters that will be available at the international Facility for Antiprotons and Ion Research (FAIR) to implode a multi-layered cylindrical target that is comprised of a high-density, high-Z shell, which encloses a sample material. Based on these simulation results, an experiment named, LAPLAS (LAboratory PLAnetary Physics), has been proposed as a part of the High-Energy-Density research program at FAIR. Using the FAIR beam parameters, several sample materials including hydrogen [1,2], water [3] and iron [4,5] have been studied. The simulation results have shown that one can generate the core conditions of gas giants like Jupiter and Saturn, icy planets like Uranus and Neptune and Earth as well as heavier rocky planets, the Super-Earths, respectively. It is hoped that these experiments will be an additional source of information to improve our understanding the planetary structure. Referances [1] N.A. Tahir et al., PRE 63 (2001) 016402. [2] N.A. Tahir et al., HEDP 2 (2006) 21. [3] N.A. Tahir et al., NJP 12 (2010) 073022. [4] N.A. Tahir et al., ApJS 232:1 (2017) September. [5] N.A. Tahir et al., ApJS 238:27 (2018) October.
Poster Blitz 4 75 Rostock, Feb 27 - Mar 01, 2019
P407 French, Martin Uni Rostock Paramagnetic-to-diamagnetic transition in dense liquid iron and its influence on electronic transport properties
Jean-Alexander Korell, Martin French, Gerd Steinle-Neumann, and Ronald Redmer
The electrical σ and thermal conductivity λ of liquid iron are calculated with spin-polarized density-functional-theory-based simulations over a significant pressure and temperature range using the Kubo-Greenwood formalism. We show that a paramagnetic state is stable in the liquid up to high temperatures at ambient pressure, and that the discrepancy between experimental results and spin-degenerate simulations for σ and λ of more than 30% are reduced to within 10% with lower values resulting from the spin-polarized simulations. Along the 3700 K isotherm, we explore the persistence of magnetic fluctuations toward high densities find indication for a continuous paramagnetic-to-diamagnetic transition near 20 - 50 GPa. This transition exerts significant influence on the physical properties of liquid iron, especially on σ and λ, and is potentially of high relevance for dynamo processes in Mercury and Mars.
76 Poster Blitz 4 Planet Formation and Evolution 2019
P408 Bethkenhagen, Mandy Institute of Physics, University of Rostock DFT+U equation of state for iron oxide
Daniel Cebulla, Mandy Bethkenhagen, Ronald Redmer
The number of detected exoplanets and the capabilities of identifying small, Earth-sized planets have grown tremendously over the last two decades. Yet many of those Earth-sized planets are only characterized in mass and radius. Therefore, interior structure models rely heavily on equations of states (EOS) for rock material to characterize the planetary properties. One particular interesting material is iron oxide, which is very challenging to treat with standard Density Functional Theory (DFT) methods. Here we investigate the DFT+U approach to obtain the correct electronic and structural properties for the FeO phases typically predicted at the high pressures within the planetary interiors. The Hubbard U is obtained self-consistently from spin-polarized DFT calculations with QUANTUM ESPRESSO [1,2] using the linear response approach [3]. The resulting optimized ground state is used as a starting point for phonon calculations within the quasi-harmonic approximation. Based on these calculations we investigate the impact of the Hubbard U on the EOS providing a step forward to incorporating more realistic rock material into interior structure models of super-Earths. REFERENCES [1] P. Gianozzi et al., ”QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials”, Journal of Physics: Condensed Matter 21, 395502 (2009). [2] P. Gianozzi et al., ”Advanced capabilities for materials modelling with QUANTUM ESPRESSO”, Journal of Physics: Condensed Matter 29, 465901 (2017). [3] M. Cococcioni and S. de Gironcoli, ”Linear response approach to the calculation of the effective interaction parameters in the LDA+U method”, Physical Review B 71, 035105 (2005).
Poster Blitz 4 77 Rostock, Feb 27 - Mar 01, 2019
P409 Li, Zhi CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon First principles molecular dynamics study of the supercritical state of iron
Zhi Li, Razvan Caracas
We investigate the behaviour of the iron cores of the bodies involved in the Giant Impact that generated the Earth-Moon couple. Due to poorly constrained equation of state and thermodynamic properties of iron in warm dense matter regime, the amount of vaporization of the two cores during impact is undetermined. We investigate the thermodynamic properties and we position the supercritical point of iron using first principles molecular dynamics simulations. Our liquid-vapour equilibrium line is in a good agreement with available experimental data. We evaluate entropy from the velocity autocorrelation function. We characterize the structural changes in the supercritical region by analysing the speciation of atoms. Our results shed new light on the amount of iron vapour produced during the Giant Impact and provide new information on the equation of state and the thermodynamic properties of iron at high temperatures that may be used in future hydrodynamic simulations. Acknowledgements: This research is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement n◦681818 – IMPACT). The simulations were performed on the GENCI supercomputers (eDARI/CINES grants x106368).
78 Poster Blitz 4 Planet Formation and Evolution 2019
P410 Preising, Martin University of Rostock The Band Gap and the Melting Line of Dense Helium
Martin Preising, Ronald Redmer
We studied the behavior of solid and liquid helium under high pressure with molecular dynamics simulations based on density functional theory (DFT-MD). Helium, as the second abundant element in nature, is important for astrophysical applications, e.g., the interior and evolution of gas giants and brown dwarfs. In particular, we calculated the melting line and examine the insulator-to-metal transition, both for extreme pressures up to the TPa region. The calculation of the melting line is a challenging topic in computational physics. Out of many approaches of different complexity and efficiency, two-phase simulations represent a very intuitive approach with high accuracy [Robert et al., Phys. Rev. E 91, 033310 (2015)]. We have implemented this method and investigated finite-size effects and other convergence issues. We found good consistency with available experiments and gave predictions for the melting line of helium up to the TPa region. Laser-driven compression experiments have shown that helium undergoes an insulator-to-metal transition with increasing density and temperature [Celliers et al., Phys. Rev. Lett. 104, 184503 (2010)]. However, the exact location and nature of this transition is not clear yet. The most recent publications on the calculation of closure of the helium band gap [Stixrude et al., Proc. Natl. Acad. Sci. USA 32, 11071 (2008) and W. Zhang et al., Sci. Rep. 7, 41885 (2017)] differ within a factor of two in density and employ different definitions of the band gap. We performed extensive convergence tests and found good agreement with the results of Zhang et al.
Poster Blitz 4 79 Rostock, Feb 27 - Mar 01, 2019
P411 Solomatova, Natalia CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon Carbon Sequestration in the Magma Ocean Implied by Complex Carbon Polymerization
Natalia V. Solomatova, Razvan Caracas, Craig E. Manning
Understanding the forms in which carbon existed in the molten early Earth is a critical step towards quantifying the carbon budget of Earth’s deep interior. Here we employ first-principles molecular dynamics to study the evolution of carbon species as a function of pressure and temperature in the molten Bulk Silicate Earth with carbon concentrations: 3.35-6.48 wt.% CO and 5.16-9.82 wt.% CO2 at 3000-5000 K. We find a wide range of carbon coordination environments, which depend strongly on the pressure, temperature and oxidation state of the melt. At low pressures, carbon is predominantly in the form of unpolymerized carbon, while at mid-mantle pressures, carbon becomes increasingly polymerized, forming complex iron-carbon polymers. Colder and more reducing conditions result in a higher degree of carbon polymerization and iron-carbon clustering. The presence of long-lived iron-carbon clusters suggests that a significant fraction of carbon in the molten Early Earth may have been extracted from the magma ocean and sequestered into the core. Acknowledgements: This research is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement n◦681818 – IMPACT). The simulations were performed on the GENCI supercomputers (eDARI/CINES grants x106368).
80 Poster Blitz 4 Planet Formation and Evolution 2019
P412 Soubiran, Fran¸cois CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon Ab initio study of Iron-Nickel alloys in Super-Earths cores
Francois Soubiran, Razvan Caracas
Iron-nickel alloys are considered the main components of Earth and Super-Earth cores, which make them crucial systems in order to comprehend the properties of these planets. While the relative nickel content is anticipated to be around 10% in the Earth, this value could differ slightly in other planets because of different host star metallicity and formation history. It is thus important to understand the properties of iron-nickel systems with various compositions in the multi-megabar regime. While pure iron is anticipated to have hexagonal close packing at high pressure, nickel is expected to have face-centered cubic packing. This means there is a structural change as the composition is modified, which can also mean a limited stability of the solid solutions of iron-nickel. We will discuss the properties of iron-nickel alloys in the megabar regime as predicted by ab initio simulations. We will examine the relative stability of different iron-nickel solid solution compositions and the interplay of the spin states. After characterizing the properties of these alloys at pressure-temperature conditions relevant for Super-Earth, we will discuss possible consequences their cores. Acknowledgements: This research is supported by the EU Marie Sklodowska-Curie Award program, grant ABISSE. The simulations were performed on the GENCI supercomputers (eDARI/CINES grants x106368).
Poster Blitz 4 81 Rostock, Feb 27 - Mar 01, 2019
P501 Caracas, Razvan CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon Retracing the condensation of the Giant Impact from ab initio atomistic simulations
We employ first-principles molecular dynamics simulations to understand the physical and chemical behavior of the molten protolunar disk, at the atomic level. We consider pyrolite as the average composition of the bulk silicate Earth. We cover the 0.75 – 7.5 g/cm3 density range and 2000 – 10000 K temperature range. This allows us to investigate the entire disk, from the interior of the molten core to the outer regions of the vaporized disk. At high density, the liquid is highly polymerized and viscous, consistent with previous studies. At low density and low temperatures, in the 2000 to 4000 K range, we capture the nucleation of bubbles. The bubbles contain a low-density gas phase rich in individual alkaline and calc-alkaline cations and SiOx groups. When volatiles are present in the system, such molecular species are the first ones to evaporate and be present in these bubbles. We interpret the bubble nucleation in terms of the liquid-vapor equilibrium. At high temperature, we identify the supercritical region characterized by one homogeneous fluid, featuring peculiar chemical speciation and short lifetimes. The nucleation of the bubbles corresponds to the spinodal instability of the melt phase in the van der Waals description of the liquid-gas equilibrium. The spinodals are reached consistently regardless of the thermodynamic path we chose to obtain the low densities. The critical curves, inferred from the spinodals, are necessary to understand the separation and degassing of volatiles during the recovery from a giant impact. As such we obtain that the largest part of the disk was in the supercritical state for a long time. We discuss the effect of a selected collection of volatiles on the structure and properties of the disk. Acknowledgements: This research is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement n◦681818 – IMPACT). The ab initio simulations were performed on the GENCI supercomputers, under eDARI/CINES grants x106368.
82 Poster Blitz 5 Planet Formation and Evolution 2019
P502 Carpenter, Vincent Max Planck Institute for Astronomy Onset of Collective Behavior of Sedimenting Particles in the Knudsen Regime
Laboratory experiments conducted by Niclas Schneider and Gerhard Wurm at the University of Duisburg-Essen, in which hollow glass beads are dropped through a rotating chamber filled with air, have observed a transition in the sedimentation behavior of particles in regions of higher local particle density: for average dust to gas ratios above 0.08, individual particles sediment faster than isolated particles, with extra speed that depends linearly on their closeness (a parameter measuring how tightly packed they are). We seek to reproduce these results in hydrodynamics simulations using the Pencil Code, both to validate the code and to allow for detailed exploration of the mechanisms triggering the onset of collective particle motion. Here we present preliminary results from ongoing two dimensional simulations, which indicate possible agreement with the experiment. Full three dimensional simulations of this version of the experiment are planned in the future, and we intend to continue collaborating with the team in Duisburg as the experiment is modified.
P503 D¨ollinger,Michaela Th¨uringerLandessternwarte Tautenburg Touchstone for Planet Formation and Evolution - F Stars vs. K Giants
Michaela D¨ollinger and Michael Hartmann
The past decades brought not only a large number of discoveries of extrasolar planets and first insights into their huge diversity but also raised a lot of new questions. The properties of intermediate-mass (IM) stars and their planets are quite different from those of solar analogs. For example, the planet occurence rate of evolved K giants seems to be higher than for the main-sequence F-type progenitors. In addition, the well-known planet-metallicity correlation for solar-like stars may not be valid for giant stars. We will deal with these issues and provide ideas of possible solutions.
Poster Blitz 5 83 Rostock, Feb 27 - Mar 01, 2019
P504 Brauer, Robert CEA Saclay The radiative transfer code POLARIS
Robert Brauer, Stefan Reissl
We present the radiative transfer (RT) code POLARIS (Reissl et al., 2016; Brauer et al., 2017b) that is able to perform a broad range of RT simulations from dust grain emission to spectral lines. Moreover, based on the magnetic field distribution of MHD simulations or analytical models, POLARIS can be used to simulate the imperfect alignment and polarized emission of non-spherical dust grains as well as the Zeeman splitting of spectral lines. In this talk, we provide an overview of POLARIS capabilities and briefly present the results of selected studies.
P505 Klahr, Hubert Max-Planck-Institut f¨urAstronomie, Heidelberg Ultima Thule puts constrains on planet formation
Hubert Klahr, Francesco Biscani
The bi-lobed structure of Ultima Thule, a primordial witness from the formation stage of our solar system, as indicated by its low eccentricity, puts constraints on a fundamental formation step of planetary building blocks, the so called planetesimals. These planetesimals form from a pebble cloud collapsing under its own weight. As the pebbles are embedded in the gaseous solar nebula, they can effectively dissipate their excess potential and kinetic energy via friction with the gas. But their angular momentum cannot be removed via friction, thus a collapsing cloud even with minimal possible angular momentum content, given by the rotation rate of the solar nebula, will quickly spin up to a centrifugally supported disk. This disk will further fragment producing a more or less hierarchical system of N >= 2 planetesimals, each individual planetesimal still spinning but slightly below the break-up velocity. Here we show that Ultima Thule can be explained by the gravitational collaps of a pebble cloud several times the current mass of Ultima Thule. A smaller cloud would not have been able to fragment sufficiently, thus the excess angular momentum would not have been able to be removed from Ultima Thule. The contact binary is then the configuration beyond which no further fragmentation is possible as the configuration can perfectly accommodate the remaining angular momentum.
84 Poster Blitz 5 Planet Formation and Evolution 2019
P506 Kollmer, Jonathan Uni Duisburg-Essen Ejecta Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids (EMPANADA)
Jonathan E. Kollmer, Tristan Emm, Riley Reid, Robert Bullard, Anna Jackson, Sean Shefferman, Ryan Boehmer, Michael Wooley, Adrienne R. Dove, Joshua E. Colwell and Karen E.Daniels
With recent sucesses in visiting asteroids and other poorly-consolidated near-earth-objects (NEOs), it has become important to safely interact with the granular materials at the surface of these objects. A particular concern is the low elastic modulus of granular materials: rubble-pile asteroids are only held together by weak gravitational and van der Waals forces. This means that both the escape velocity and the sound velocity are low compared to their values on earth. To better predict the dynamics of the granular flows resulting from surface explorations such as digging, sample-collection, anchoring, or lift-off, we develop microgravity experiments which are able to predict the circumstances under which the NEO material will remain intact or become unstable. In our EMPANADA experiment, we insert a flexible probe into a granular material under low gravity. We show that low-speed interactions reduce the effects of shock wave creation and observe that thinner diggers allow the grains to rearrange and minimize the possibility of ejecta.
P507 Kruss, Maximilian University of Duisburg-Essen How Magnetic Aggregation Can Help Forming Mercurys
Maximilian Kruss, Gerhard Wurm
Iron is a very abundant element in protoplanetary disks. Especially in the inner regions, which are threaded by strong magnetic fields, planets with an anomalously large iron core are observed, Mercury being an example from the Solar System. We carried out coagulation experiments to study the self-consistent evolution of µm sized iron aggregates toward the bouncing barrier. While without external magnetic field iron aggregates are stuck at this barrier, they build larger entities in the presence of magnetic fields due to magnetic dipole-dipole forces. This way iron-rich aggregates in the inner region of protoplanetary disks may grow to sizes where streaming instabilities set in, giving a hint at the formation of Mercury-like planets.
Poster Blitz 5 85 Rostock, Feb 27 - Mar 01, 2019
P508 Parker, Richard University of Sheffield, UK Enlarging habitable zones around binary stars in hostile environments
Richard J. Parker, Bethany A. Wootton
Most stars, and by extension planets, form in dense star-forming regions that are thought to be very hostile to young planetary systems. Dynamical interactions from passing stars and external photoevaporation from massive stars can truncate or destroy protoplanetary discs. However, most stars form in binary systems where there are usually two habitable zones (one around each star). In this talk, I will show that dense star-forming regions alter the orbits of binary stars in such a way that the habitable zones for planets in binary star systems can overlap and become enlarged. I will discuss how these results provide an interesting twist on the paradigm that star-forming regions are always detrimental to planet formation and evolution.
P509 Schaan, Renata CNRS, ENS de Lyon, Laboratoire de Geologie de Lyon Behavior of volatiles during the Giant Impact
Renata B. Schaan, Razvan Caracas
We study binary systems between oxides and water to understand the behavior of volatile during the Giant Impact. We present the project with some preliminary results. We are interested in determining the effect of volatiles on the critical point of given oxides (silica, magnesia). We analyze the behavior of the corresponding melts in the presence of water, the speciation in the supercritical state and the transport properties. For this we perform first-principles molecular dynamics simulations. Acknowledgements: This research is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement n◦681818 – IMPACT). The simulations were performed on the GENCI supercomputers (eDARI/CINES grants x106368).
86 Poster Blitz 5 Planet Formation and Evolution 2019
P510 S¨uli, Aron´ E¨otv¨osUniversity Statistics and analysis of collisional parameters computed from 2D simulations
A.´ S¨uli,R. Reg´aly
There are two favored practices to speed up N-body simulations of planet formation: (i) confine motion to 2 spatial dimensions (2D), or (ii) to artificially enlarge the physical radii of the bodies with a factor denoted by Aref . These practices increase the collision probability between objects thus shorten the formation timescale. In this work we have performed 10 simulations in 2D for each Aref = 1, 2, 3, 5, 10 values resulting in 50 simulations each containing N = 104 fully interacting bodies. For each run we have computed the probability density functions (pdf) of the impact angle, parameter, speed and energy. Our major goal was to find out the dependence of the pdfs on Aref . We found that the pdfs of the impact parameter does not depend on Aref , while those of speed and energy strongly depend. The distribution of the impact parameter is uniform. The pdf of the impact speed can be well fitted with an exponential function for all Aref . We found that the impact velocity for Aref = 1 is greater than the mutual escape velocity, hence physical collisions do not lead to pure merges, but significant fragmentation take place. The pdfs of speed shifts to lower values for Aref > 1. An analytic model is presented to describe the measured pdfs of speed.
Poster Blitz 5 87 Rostock, Feb 27 - Mar 01, 2019
P511 Faramaz, Virginie JPL-Caltech From scattered-light to millimeter emission: A global view of the Gyr-old system of HD 202628 and its eccentric debris ring
John Krist, Karl R. Stapelfeldt
We present a multi-wavelength observations of the cold eccentric debris ring surrounding the Gyr-old, solar-type star HD 202628 in scattered light with HST/STIS, at far-infrared wavelengths with Herschel/PACS and SPIRE, and at millimeter wavelengths with ALMA. Similar to the debris disk of Fomalhaut, the ring appears much narrower at millimeter wavelengths than at optical wavelengths, while its inner edge is found to be consistent between ALMA and HST data. The offset of the ring centre of symmetry from the star allows us to quantify its eccentricity to be e = 0.08 ± 0.03. This eccentric feature also reveals itself in low resolution Herschel/PACS observations, in the form of a pericenter-glow. Upper limits on the gas mass provided by ALMA data allow us to exclude gas-solid interactions as the reason for the narrowness and eccentricity of the ring, which implies the presence of a distant belt-shaping eccentric perturber in this system. From the combination of the ALMA and the Herschel photometry, we retrieve a disk grain size distribution index of ∼ −3.5, and therefore exclude in-situ formation of the inferred perturber, for which we provide new dynamical constraints. Finally, ALMA images show a source just interior to the ring. Although we cannot exclude it to be a background object at that stage, we cannot exclude either that this source is circumplanetary material surrounding the eccentric belt-shaper, in which case degeneracies between its mass and orbital parameters could be lifted, allowing us to fully characterize a mature planet on a wide orbit for the very first time.
88 Poster Blitz 5 Planet Formation and Evolution 2019
P512 Flores, Lizxandra Max Planck Institute for Astronomy Chemistry in envelope and disk in protostar L1527
Molecule formation is dynamic during the protostar collapse phase, driven by changes in temperature, density, and Ultra-Violet (UV) radiation as gas and dust flows from the envelope onto the forming protoplanetary disk. In this work, we compare two physical models, one describing the envelope as free-falling collapse and the other one includes a rotating-infalling envelope derived from an inside-out collapse. We modeled the chemistry (Karen et al. 2009) for 12CO to see how its abundance changes over time using as primary input parameters the temperature and density profile that were produced by HOCHUNK3D (Whitney et al. 2013). For each model, we aim to produce synthetic line emission maps since comparing to ALMA observations this line emission appears to trace the disk-envelope boundary. Results show that for cold regions in the disk-envelope interface, radiation field plays an important role.
P513 Hellard, Hugo DLR Berlin, TU Berlin
Retrieval of the fluid Love number k2 in exoplanetary transit curves
Hugo Hellard, Szilard Csizmadia, Sebastiano Padovan, Frank Sohl, Tilman Spohn, Heike Rauer, Doris Breuer
Direct measurements of exoplanetary mass and radius cannot be uniquely interpreted in terms of interior structure, justifying the need for an additional observable. The second degree fluid Love number, k2, is proportional to the concentration of mass towards the body’s center, hence providing valuable additional information about the internal structure. When hydrostatic equilibrium is assumed for the planetary interior, k2 is a direct function of the planetary shape. Here, we construct a self-consistent analytical 3D shape model that properly accounts for tidal and rotational deformations. We illustrate the feasibility of our method by showing that James Webb Space Telescope has the means to measure the shape of WASP-121b.
Poster Blitz 5 89 Rostock, Feb 27 - Mar 01, 2019
P601 Alibert, Yann Center for Space and Habitability, University of Bern A new metric to quantify the similarity between planetary systems - application to dimensionality reduction using T-SNE
We define a new metric to infer the similarity between two planetary systems, based on the properties of planets that belong to these systems. We then compare the similarity of planetary systems with the similarity of protoplanetary discs in which they form. We show that the new metric can help finding the underlying structure of populations of planetary systems. In addition, the similarity between planetary systems as we define in this paper is correlated with the similarity between the protoplanetary discs in which these systems form.
P602 Monsch, Kristina Universit¨ats-Sternwarte der Ludwig-Maximilians-Universit¨atM¨unchen (USM-LMU) The imprint of X-ray photoevaporation on the orbital distribution of giant planets
Kristina Monsch, Barbara Ercolano, Thomas Preibisch, Giovanni Picogna, Markus Michael Rau
Recent exoplanet surveys have highlighted the existence of an impressive diversity of planetary systems, raising the question of how systems similar to our own can form and develop. The key to explaining the diversity of planetary systems is in the understanding of the statistical trends that are emerging from the recent wealth of exoplanet data. One of these is the non-uniform distribution of the semi-major axes of gas giants. Giant planets are found to preferentially clump up at orbital radii of ∼1-2 au and finding what determines this peak is of strong interest. It has recently been suggested that this distribution may be established during the time of planetary migration in the protoplanetary disc, being halted by X-ray driven photoevaporation (Ercolano & Rosotti, 2015). We have searched for signatures of this process by correlating the X-ray luminosity of host stars with the semi-major axis distribution of their giant planets. Our statistical analysis of the observational data confirms a prominent feature that is also predicted by simulations, further strengthening the conclusion that X-ray photoevaporation may be shaping the architecture of planetary systems.
90 Poster Blitz 6 Planet Formation and Evolution 2019
P603 Bergez-Casalou, Camille MPIA Accretion and migration of multiple giant planets in their protoplanetary disc
The accretion of gas onto giant planets has a large impact on the structure of their surrounding disc. We study this influence to characterize the evolution of their mass and migration rate. We perform isothermal hydrodynamical simulations with the Fargo2D1D code where the accretion is based on recipes from the litterature (Kley 1999, Machida 2010). As we are interested into the effects of gas accretion onto the disc structure and onto the migration rates of accreting planets, we investigate the influence of the initial gas surface density and viscosity of the disc for a single accreting planet. After confirming previous results, we investigate the case of two planets accreting gas in competition. These two planets are placed in the 2:1 resonance and are initially not allowed to migrate. The planets have 20 Earth masses initially and are assumed to be in the runaway gas accretion regime. By comparing this result with the single planet case, we are able to deduce the influence of the competitive accretion. First results show a larger outer planet, as the inner region of the disc is slowly depleted in gas by the accretion of the planets and the central star.
P604 Penzlin, Anna Institut f¨urAstronomie und Astrophysik, Universit¨atT¨ubingen Migration of planets in circumbinary discs
Anna Penzlin, Daniel Thun, Wilhelm Kley
As of today there are about 10 planets detected through the Kepler space mission that orbit a binary star. In all cases the planets reside close to the instability limit, and it is believed that they migrated from a larger distance to their observed locations. In this contribution we examine this process in more detail. First, we analyse the dynamics of discs around binary stars without planets for five well known systems (Kepler-16, -34, -35, -38, -413), and show that in all cases a large inner gap is formed and that the disc becomes eccentric and precesses slowly in a prograde manner around the binary. We show how the size and eccentricity of the inner gap depends on binary and disc parameter. We then embed planets with the observed mass into the system and follow their evolution until a quasistationary state is reached. The planets stop at some distance away from the binary, and direct comparison with the observed location allows to obtain information about the conditions of their formation.
Poster Blitz 6 91 Rostock, Feb 27 - Mar 01, 2019
P605 Regaly, Zsolt Konkoly Observatory Type-I migration of dust accreting low-mass planets
Recent investigation (Benitez-Llambay et al. 2018) revealed that dust content can alter the type I migration regime of low-mass planets, nevertheless, only 1% of mass in protoplanetary disk are in dust. With our newly developed grid-based dust module in GFARGO2 GPU code, we further investigated the migration of low-mass planets that are subject to dust accretion. We found that the migration of low-mass planets can even change its direction, i.e planets can migrate outward in case of strong dust accretion. Our finding can have a major consequence on planet formation processes: i.e., planets can avoid stellar engulfment due to fast inward type I migration by strong dust accretion.
P606 Rowther, Sahl University of Warwick The Migration of Giant Planets in Self-gravitating Discs
Sahl Rowther, Farzana Meru
We present the results of the migration of giant planets in self-gravitating discs. In previous studies, the disc was modeled with a constant cooling parameter β, which meant that the turbulent fluctuations were the same in all regions of the disc. However, real self-gravitating discs are expected to be more turbulent in the outer parts of the disc than the inner region.
In this work, the value of β is varied with radius to mimic a realistic disc with varying turbulence. Multiple simulations using a 3D SPH code are done by changing the properties of β: varying the absolute level of turbulence; and how it varies with disc radius. The migration of giant planets is followed and compared to results from a constant β. This allows the effects of turbulence to be studied in a controlled manner, allowing its effects to be understood more easily. The results show whether the inner parts of the self-gravitating disc can help planets survive.
92 Poster Blitz 6 Planet Formation and Evolution 2019
P607 Guenther, Eike Wolf Th¨uringerLandessterwarte Tautenburg Has stellar activity an impact on the evolution of planets, or their habitability?
Surveys of extrasolar planets have now reached a level at which it becomes possible to detected planets of roughly the size and mass of the Earth. Particularly popular are now surveys for planets of cool, low-mass stars, because the detection of such planets in the so-called habitable zone is much easier than for solar-type stars. However, cool, low-mass stars are quite different from solar-like stars. Many of them are rather active. They emit not only a relatively large amount of radiation in X-rays but flare-events and coronal mass ejections occur quite often on them. Flares are caused by the sudden release of energy from the magnetic field of the star. During a flare the star emits a large amount of X-rays. However, not only the amount of X-ray radiation is larger, the radiation is also substantially harder than during quiescence. Coronal-mass ejections are often associated with flares. In these events plasma is ejected from the star in to space. While the X-rays from the star in quiescence does not affect the evolution and the habitability of a planets too much, the effects from flares coronal-mass ejections has not been studied in detail yet. Is it possible that such events erode the atmospheres of planets when they are young, or can they sterilize a planet in the habitable zone? To study these effects we have carried out an intensive monitoring campaign of active low-mass stars. In February of this year, we observed a giant flare event on one of our target stars: AD Leo. This star is particularly interesting, because it has been claimed that this star has a planet of 70 Earth-masses orbiting the star at a distance of 0.02 AU (one AU is the distance of the Erath to the Sun in our solar-system). Since the habitable zone of this stars is at a distance of 0.07-0.2 AU, this planet is clearly outside of it. However, since stars that have one planet, usually have more, we can ask the question what would happen to a planet which is in the habitable zone. How strong would the X-ray radiation on a planet in the habitable zone during such an event be? Could such events erode the atmosphere of a planet if they are frequent? Would they sterilize it?
Poster Blitz 6 93 Rostock, Feb 27 - Mar 01, 2019
P608 Jungmann, Felix University of Duisburg-Essen How charges on grains increase the sticking velocity
Felix Jungmann, Tobias Steinpilz, Jens Teiser, Gerhard Wurm
In drop tower experiments monodisperse, sub-mm sized glass spheres were triboelectrically charged and their collisions observed. We find that particles with high velocity (e.g. dm/s) and high charge (e.g. 10 million elementary charges) can stick to an electrode where uncharged grains do not stick. In general, the sticking velocity increases linearly with the net charge. In the experiments this is caused by the attraction of a mirror charge leading to acceleration and a larger dissipation of energy during final approach before a collision. In the electrostatic potential of the mirror charge particles get trapped. This requires non homogeneous charge distributions on the surface. In protoplanetary disks this might also enhance sticking since collisions of oppositely charged particles can be boosted by the same electrostatic attractions.
P609 Kellermann, Clemens Institute of Physics, University of Rostock Interior structure models and fluid Love numbers of exoplanets in the super-Earth regime
Clemens Kellermann, Andreas Becker and Ronald Redmer
The increasing number of discovered exoplanets provides us with new planetary classes, such as super-Earths and mini-Neptunes. In order to model their interior structure the mean density of a planet is an important input. Based on this quantity we can decide whether extensive gaseous layers or rocky mantle materials have to be considered. In this work we calculate three-layer models with one or two adiabatic outer layers of volatile material and two or one isothermal, solid inner layers consisting of magnesium oxide (MgO) or iron (Fe), respectively, as well as the resulting Love numbers k2. This quantity results from the planet’s internal density profile and, if also measured, can be used to constrain the possible layer compositions and sizes. To examine the effect of planet mass, layer sizes and surface temperature on internal structure and Love number we perform a parameter study. Furthermore, we apply the results to analyze several known exoplanets with measured densities in the regime of super-Earths and mini-Neptunes. We find that an observational constraint on k2 would be particularly useful to narrow down the planetary Fe/MgO mass ratio.
94 Poster Blitz 6 Planet Formation and Evolution 2019
P610 Linder, Esther University of Bern Evolution and magnitudes of low-mass planets
Esther Linder, Christoph Mordasini, Paul Molliere, Gabriel-Dominique Marleau, Matej Malik, Sascha P. Quanz, Michael R. Meyer
Coming instruments like NIRCam and MIRI on the JWST will be able to image low-mass planets that are too faint for current direct imaging instruments. On the theoretical side, core accretion formation models predict a significant population of distant low-mass planets at orbital distances of 10-1000 au. So far, evolutionary models predicting the planetary intrinsic luminosity as a function of time have been concentrated on gas-dominated giant planets, going down to e.g. 0.5 Jupiter masses in Baraffe et al. 2008. We extend these cooling curves to isolated lower mass planets such as Saturnian, Neptunian, and super-Earth planets (down to 5 Earth masses). The planets in our model consist of a core made of iron, silicates, and ices, surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity includes the contribution from the cooling and contraction of the core, the H/He envelope, and radiogenic decay. Different atmospheric models (AMES-Cond, petitCODE, HELIOS) are used. We validate our model by simulating the solar system gas giants as well as a 2 Jupiter mass planet and find good agreement with the literature for the luminosity. Considering a wide range of metallicities and cloud parameters magnitudes in JWST filter bands are calculated. Comparison with the JWST sensitivity limits lets us estimate the detectability of low-mass planets over time. For example, a 20 Earth mass planet in the frame of our model is visible until 10 Myr after its formation. Evolutionary models of low-mass planets: Cooling curves, magnitudes, and detectability by JWST
Poster Blitz 6 95 Rostock, Feb 27 - Mar 01, 2019
P611 Poser, Anna Julia Institute of Physics, University of Rostock Irradiated atmospheres and the core mass of hot Jupiters
Anna Julia Poser, Nadine Nettelmann, Ulrike Kramm, Ronald Redmer
Giant planets are important astrophysical objects as they shape planetary systems. We aim at understanding their formation processes and evolution scenarios of planetary systems. Basic correlations such as that between the planetary heavy element mass (MZ ) and the stellar metallicity [1,2] are key in this context. We determine the core mass Mcore of the planet as a representative of the heavy element mass by the combination of atmosphere, structure, and evolution calculations. We investigate the transition region between atmosphere and interior of irradiated, transiting planets by using different opacities, e.g. constant values or Rosseland mean opacities and their analytical fits [3], and study the influence of that choice on the derived core mass. Furthermore, we calculate atmospheric profiles with and without clouds based on a semi-analytical atmosphere model [4,5]. We find that low-opacity clouds in the upper atmosphere, i.e. P < 1 bar, have low influence on the predicted core mass. On the other hand, optically thick clouds in the lower atmosphere, i.e. P > 10 bar show strong influence on Mcore of about 30 − 50 ME for higher intrinsic temperatures Tint. In future work we may compare to different atmosphere models, such as HELIOS [6]. [1] Guillot et al. (2006), A&A 453:L21 [2] Thorngren et al. 2016), ApJ 831:64 [3] Valencia et al. (2013), ApJ 775:10 [4] Guillot (2010), A&A 520:A27 [5] Heng et al. (2012), MNRAS 420:20 [6] Malik et al. (2017), AJ 153:2
96 Poster Blitz 6 Planet Formation and Evolution 2019
P612 Scheibe, Ludwig Universit¨atRostock Thermal evolution of adiabatic Uranus and Neptune and beyond
Ludwig Scheibe, Nadine Nettelmann, Ronald Redmer
We present work in progress towards a modelling approach for the interior and evolution of giant planets. It follows the well-known method by Henyey et al. (1964) [1] for stars.
In contrast to conventional modelling assumptions for Jupiter and Saturn [2] and Uranus and Neptune [3], our goal is to go beyond the premise of adiabatic interiors, as the presence of stably stratified and thus non-adiabatic regions is indicated by some magnetic field models for the ice giants [4] and also adiabatic evolution calculations fail to reproduce Uranus’ and Neptune’s present-day luminosity [3,5]. Therefore, we solve self-consistently for the local temperature gradient, the compositional gradient and the heat flux.
Here, we present theoretical foundations and implementation of the model as well as first results consisting of adiabatic evolution models for Uranus and Neptune with different parameter options regarding solar irradiation and planetary albedo. [1] Henyey, Forbes, and Gould (1964). ApJ 139, 306 [2] Guillot (1999). Planet. Space Sci. 47, 1183 [3] Nettelmann, Helled, Fortney, and Redmer (2013). Planet. Space Sci. 77, 143 [4] Stanley and Bloxham (2004). Nature 428, 151 [5] Fortney, Ikoma, Nettelmann, Guillot, and Marley (2011). ApJ 729, 32
Poster Blitz 6 97 Rostock, Feb 27 - Mar 01, 2019
P613 Vazan, Allona Hebrew University of Jerusalem, University of Zurich Contribution of the core to the thermal evolution of sub-Neptunes
A. Vazan, C. W. Ormel, L. Noack, C. Dominik
Sub-Neptune planets are a very common type of planets. They are inferred to harbour a primordial (H/He) envelope, on top of a (rocky) core, which dominates the mass. We investigate the long-term consequences of the core properties on the planet mass-radius relation. We consider the role of various core energy sources resulting from core formation, its differentiation, its solidification (latent heat), core contraction and radioactive decay. The rocky core is modelled by three chronological phases: formation phase, magma ocean phase, and solid state phase. We show that for typical sub-Neptune planets of 2-10 Earth masses and envelope mass fractions of 0.5-10% the magma ocean phase lasts several Gyrs, much longer than for terrestrial planets. The magma ocean phase effectively erases any signs of the initial core thermodynamic state. After solidification, the reduced heat flux from the rocky core causes a significant drop in the rocky core surface temperature, but its effect on the planet radius is limited. Overall, the long term radius uncertainty by core thermal effects is up to 15% for sub-Neptune planets.
98 Poster Blitz 6