PROJECT EOS May 24, 2019

EARTHS IN OTHER SOLAR SYSTEMS

Recent Publications

On the Mass Function, Multiplicity, and Origins of Wide-Orbit Giant Planets ………………………………. Unlocking CO Depletion in PROJECT EOS Protoplanetary Disks II. Primordial C/H Predictions Inside the CO Snowline ……………………………….. Laboratory evidence for co- condensed oxygen- and carbon-rich meteoritic is part of NASA’s Nexus for stardust from nova outbursts Earths in Other Solar Systems Exoplanetary System Science program, which carries out ……………………………….. coordinated research toward to the goal of searching for and + Line Ratios Reveal N2H determining the frequency of habitable extrasolar planets with Emission Originates above the atmospheric biosignatures in the Solar neighborhood. Midplane in TW Hydrae Our interdisciplinary EOS team includes astrophysicists, ……………………………….. planetary scientists, cosmochemists, material scientists, No Clear, Direct Evidence for chemists and physicists. Multiple Protoplanets The Principal Investigator of EOS is Daniel Apai (University of Orbiting LkCa 15: LkCa 15 Arizona). The project’s lead institutions are The University of bcd are Likely Inner Disk Arizona‘s Steward Observatory and Lunar and Planetary Signals Laboratory. ……………………………….. The EOS Institutional Consortium consists of the Steward The Exoplanet Population Observatory and the Lunar and Planetary Laboratory of the Observation Simulator. II - University of Arizona, the National Optical Astronomy Population Synthesis in the Observatory, the Department of Geophysical Sciences at the Era of Kepler University of Chicago, the Planetary Science Institute, and the Catholic University of Chile. For a complete list of publications, please visit the EOS Library on the SAO/NASA Astrophysics Data System. eos-nexus.org 1 PROJECT EOS May 24, 2019

On the Mass Function, Multiplicity, and Origins of Wide-Orbit Giant Planets

Kevin Wagner, Dániel Apai, Kaitlin M. Kratter

Astrophysics - Earth and Planetary Astrophysics

A major outstanding question regarding the formation of planetary systems is whether wide-orbit giant planets form differently than close-in giant planets. We aim to establish constraints on two key parameters that are relevant for understanding the formation of wide-orbit planets: 1) the relative mass function and 2) the fraction of systems hosting multiple companions. In this study, we focus on systems with directly imaged substellar companions, and the detection limits on lower- mass bodies within these systems. First, we uniformly derive the mass probability distributions of known companions. We then combine the information contained within the detections and detection limits into a survival analysis statistical framework to estimate the underlying mass function of the parent distribution. Finally, we calculate the probability that each system may host multiple substellar companions. We find that 1) the companion mass distribution is rising steeply toward smaller masses, with a functional form of N∝ M −1.3±0.3, and consequently, 2) many of these systems likely host additional undetected sub-stellar companions. Combined, these results strongly support the notion that wide-orbit giant planets are formed predominantly via core accretion, similar to the better studied close-in giant planets. Finally, given the steep rise in the relative mass function with decreasing mass, these results suggest that future deep observations should unveil a greater number of directly imaged planets.

Fig. 1.| The cumulative mass probability distribution of directly imaged companions within 100 AU of A0-K8 stars. Overall, the slope is steeper at lower masses, reflecting a higher relative frequency of objects detected with low mass compared to objects of higher mass. The dashed lines show the pre- selected mass bins that will be utilized in the proceeding analysis. eos-nexus.org 2 PROJECT EOS May 24, 2019

Unlocking CO Depletion in Protoplanetary Disks II. Primordial C/H Predictions Inside the CO Snowline Kamber R. Schwarz, Edwin A. Bergin, L. Ilsedore Cleeves, Ke Zhang, Karin I. Öberg, Geoffrey A. Blake, Dana E. Anderson

Astrophysics - Earth and Planetary Astrophysics

CO is thought to be the main reservoir of volatile carbon in protoplanetary disks, and thus the primary initial source of carbon in the atmospheres of forming giant planets. However, recent observations of protoplanetary disks point towards low volatile carbon abundances in many systems, including at radii interior to the CO snowline. One potential explanation is that gas phase carbon is chemically reprocessed into less volatile species, which are frozen on dust grain surfaces as ice. This mechanism has the potential to change the primordial C/H ratio in the gas. However, current observations primarily probe the upper layers of the disk. It is not clear if the low volatile carbon abundances extend to the midplane, where planets form. We have run a grid of 198 chemical models, exploring how the chemical reprocessing of CO depends on disk mass, dust grain size distribution, temperature, cosmic ray and X-ray ionization rate, and initial water abundance. Building on our previous work focusing on the warm molecular layer, here we analyze the results for our grid of models in the disk midplane at 12 au. We find that either an ISM level cosmic ray ionization rate or the presence of UV photons due to a low dust surface density are needed to chemically reduce the midplane CO gas abundance by at least an order of magnitude within 1 Myr. In the majority of our models CO does not undergo substantial reprocessing by in situ chemistry and there is little change in the gas phase C/H and C/O ratios over the lifetime of the typical disk. However, in the small sub-set of disks where the disk midplane is subject to a source of ionization or photolysis, the gas phase C/O ratio increases by up to nearly 9 orders of magnitude due to conversion of CO into volatile hydrocarbons.

Figure 2. Log CO gas abundance relative to H2 in the midplane at 12 au for each model after 1 Myr. eos-nexus.org 3 PROJECT EOS May 24, 2019

Laboratory evidence for co-condensed oxygen- and carbon- rich meteoritic stardust from nova outbursts Pierre Haenecour, Jane Y. Howe, Thomas J. Zega, Sachiko Amari, Katharina Lodders, Jordi José, Kazutoshi Kaji, Takeshi Sunaoshi, Atsushi Muto

Nature Astronomy - Letters, April 29, 2019

Although their parent stars no longer exist, the isotopic and chemical compositions and microstructure of individual stardust grains identified in meteorites provide unique constraints on dust formation and thermodynamic conditions in stellar outflows1,2,3,4,5. Novae are stellar explosions that take place in the hydrogen-rich envelope accreted onto the surface of a white dwarf in a close binary system6. The energy released by a suite of nuclear processes operating in the envelope powers a thermonuclear runaway, resulting in the ejection of processed material into the interstellar medium. Spectral fitting of features observed in the infrared spectra of dust- forming novae provided evidence of the co-condensation of both carbonaceous and silicate dust in stellar outflows within 50 to 100 days after explosion. Although novae appear as prolific producers of both carbon- and oxygen-rich dust, very few presolar grains that can be attributed to novae have been found in meteorites thus far. Here, we report the identification of an oxygen- rich inclusion, composed of both silicate and oxide nanoparticles, inside a graphite spherule that originated in the ejecta of a low-mass carbon- and oxygen-rich (CO) nova. This observation establishes laboratory evidence of the co-condensation of oxygen- and carbon-rich dust in nova outbursts and is consistent with large-scale transport and mixing of materials between chemically distinct clumps in the nova ejecta.

Fig. 1: STEM data of AP-149.

a,b, Bright-field (a) and annular dark-field (b) images of LAP-149. c, EELS three-window C-K edge map of LAP-149, showing the carbon distribution. d, False-colour composite EDS elemental maps (carbon, red; oxygen, blue; silicon, green). The scale bar in a applies to all of the panels. eos-nexus.org 4 PROJECT EOS May 24, 2019

+ Line Ratios Reveal N2H Emission Originates above the Midplane in TW Hydrae

Kamber R. Schwarz, Richard Teague, Edwin A. Bergin

The Astronomical Journal Letters, Volume 876, Number 1

Line ratios for different transitions of the same molecule have long been used as a probe of gas + temperature. Here we use ALMA observations of the N2H J = 1─0 and J = 4─3 lines in the protoplanetary disk around TW Hya to derive the temperature at which these lines emit. We find an averaged temperature of 39 K with a 1σ uncertainty of 2 K for the radial range 0.″8─2″, which is significantly warmer than the expected midplane temperature beyond 0.″5 in this disk. + We conclude that the N2H emission in TW Hya is not emitting from near the midplane, but rather from higher in the disk, in a region likely bounded by processes such as photodissociation or chemical reprocessing of CO and N2 rather than freeze-out.

Figure 1. Spectra for the N2H+ J = 1–0 (top) and J = 4–3 (bottom) lines after de-projection, stacking, and averaging over a ring from 0.ʺ8 to 2ʺ. Light shading indicates the 1σ uncertainty in each channel. Vertical dashed lines show the expected location of the 1–0 hyperfine lines.

eos-nexus.org 5 PROJECT EOS May 24, 2019

No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals Thayne Currie, Christian Marois, Lucas Cieza, Gijs Mulders, Kellen Lawson, Claudio Caceres, Dary Rodriguez-Ruiz, John Wisniewski, Olivier Guyon, Timothy Brandt, N. Jeremy Kasdin, Tyler Groff, Julien Lozi, Jeffrey Chilcote, Klaus Hodapp, Nemanja Jovanovic, Frantz Martinache, Nour Skaf, Wladimir Lyra, Motohide Tamura, Ruben Asensio-Torres, Ruobing Dong, Carol Grady, Misato Fukagawa, Derek Hand, Masahiko Hayashi, Thomas Henning, Tomoyuki Kudo, Masayuki Kuzuhara, Jungmi Kwon, Michael McElwain, Taichi Uyama

Astrophysics - Earth and Planetary Astrophysics

Two studies utilizing sparse aperture masking (SAM) interferometry and Hα differential imaging have reported multiple jovian companions around the young solar-mass star, LkCa 15 (LkCa 15 bcd): the first claimed direct detection of infant, newly-formed planets ("protoplanets"). We present new near-infrared direct imaging/spectroscopy from the SCExAO system coupled with the CHARIS integral field spectrograph and multi-epoch thermal infrared imaging from Keck/NIRC2 of LkCa 15 at high Strehl ratios. These data provide the first direct imaging look at the same wavelengths and in the same locations where previous studies identified the LkCa 15 protoplanets and thus offer the first decisive test of their existence. The data do not reveal these planets. Instead, we resolve extended emission tracing a dust disk with a brightness and location comparable to that claimed for LkCa 15 bcd. Forward-models attributing this signal to orbiting planets are inconsistent with the combined SCExAO/CHARIS and Keck/NIRC2 data. An inner disk provides a more compelling explanation for the SAM detections and perhaps also the claimed Hα detection of LkCa 15 b. We conclude that there is currently no clear, direct evidence for multiple protoplanets orbiting LkCa 15, although the system likely contains at least one unseen jovian companion. To identify jovian companions around LkCa 15 from future observations, the inner disk should be detected and its effect modeled, removed, and shown to be distinguishable from planets. Protoplanet candidates identified from similar systems should likewise be clearly distinguished from disk emission through modeling.

Figure 1. LkCa 15 images from SCExAO/CHARIS (top panels) and Keck/NIRC2 (bottom panels). The data are processed using different combinations of ADI, SDI, and RDI using the A-LOCI and KLIP algorithms. All images reveal spatially-extended emission consistent with disk emission, not planets. A white dashed circle shows a radius of 0.”06. LkCa 15 bcd's positions (circled) from Sallum et al. (2015b) trace the edge of the inner disk. The vertical bars show the intensity scale in units of mJy normalized to one FWHM.

eos-nexus.org 6 PROJECT EOS May 24, 2019

The Exoplanet Population Observation Simulator. II - Population Synthesis in the Era of Kepler Gijs D. Mulders, Christoph Mordasini, Ilaria Pascucci, Fred J. Ciesla, Alexandre Emsenhuber, Dániel Apai

Astrophysics - Earth and Planetary Astrophysics

The collection of planetary system properties derived from large surveys such as Kepler provides critical constraints on planet formation and evolution. These constraints can only be applied to planet formation models, however, if the observational biases and selection effects are properly accounted for. Here we show how epos, the Exoplanet Population Observation Simulator, can be used to constrain planet formation models by comparing the Bern planet population synthesis models to the Kepler exoplanetary systems. We compile a series of diagnostics, based on occurrence rates of different classes of planets and the architectures of multi-planet systems, that can be used as benchmarks for future and current modeling efforts. Based on these diagnostics we identify physical properties and processes that would result in the Bern model more closely matching the known planetary systems. These are: moving the planet trap at the inner disk edge outward; increasing the formation efficiency of mini-Neptunes; reducing the fraction of stars that form observable planets; and increasing the relative importance of dynamical stirring with respect to orbital damping by gas. We conclude with an outlook on the composition of planets in the habitable zone, and highlight that the majority of simulated planets smaller than 1.7 Earth radii have substantial hydrogen atmospheres.

a) b)

Figure 1. Planet radii and orbital periods of planets formed in the Bern population synthesis model. The histograms on the top and side show the marginalized distributions compared to the Kepler parameteric distributions derived in Mulders et al. (2018) (red). Panel a) shows the model with 100 seed planet cores per disk and panel b) the model with one seed planet core per disk. eos-nexus.org 7