PULSATIONS IN INTERMEDIATE-MASS, MASSIVE AND/OR MULTIPLE ONLINE EVENT WORKSHOP PROGRAMME

18 – 22 JANUARY 2021 OUR SPONSORS INTRODUCTION

Most stellar systems are binaries in which oscillation frequencies in binaries will drive stars form as twins. Having a companion the development of next-generation stellar greatly impacts their evolution. Tides deform models including more precise treatments of and spin up stars, and excite oscillations, internal mixing and multidimensional effects. while cataclysmic events like mass The Royal Astronomical Society (RAS) The institute of Advanced Studies (IAS) This breakthrough international workshop This workshop has been made possible The Institute of Advanced Studies (IAS) at transfer, common envelopes, mergers and will pioneer the potential of asteroseismology thanks to the generous support of the Royal the University of Surrey sponsors workshops explosions can create exotic stellar objects in the analysis of binary stars. It will Astronomical Society, from its inception and Fellow-ships at the ‘cutting edge’ of that challenge theory. connect international experts in these as an in-person event, and through its science, engineering, social science and the Over the last few decades, asteroseismology fields at all stages of their careers, to postponement due to the Covid-19 pandemic. humanities. Through this scheme the Institute has become a major source of information forge new approaches and techniques The Royal Astronomical Society, founded in fosters interdisciplinary collaborations and about stellar interiors. The Corot, Kepler that build on the wealth of data delivered 1820, encourages and promotes the study of encourages a flow of international scholars and TESS space-missions measured by 21st-century astronomical missions astronomy, solar-system science, geophysics to visit, enjoy their stay at Surrey and leave thousands of stellar lightcurves. Their like Corot, Kepler, TESS and BRITE, and and closely related branches of science. behind excellent ideas and innovations. analysis yields stellar masses and radii advanced stellar evolution modelling. with unprecedented accuracy, but mostly ras.ac.uk ias.surrey.ac.uk Workshop Chair: in single or non-interacting stars. Stars in Dr Giovanni Mirouh, University of Surrey close binaries were, and are, neglected in stellar-oscillation studies because of their Organising committee: far more complicated evolutionary paths. Dr Robert Izzard, University of Surrey Their study requires dedicated techniques Mr David Hendriks, University of Surrey that link oscillations to binary- interaction Dr Andrea Miglio, University of Birmingham physics, and similarly complex methods Administrative support: to match models with observations. Ms Vicki Blamey, Ms Mirela Dumic and In particular, correct interpretations of Ms Joanna Moore (University of Surrey)

2 SURREY.AC.UK UNIVERSITY OF SURREY 3 PROGRAMME

DAY 1 – MONDAY 18TH JANUARY DAY 2 – TUESDAY 19TH JANUARY

(GMT) (GMT)

09.00 – 09.30 Introduction to the first PIMMS workshop –Dr Giovanni Mirouh 09.00 – 09.30 Coffee/tea time and discussion 09.30 – 10.30 Seismology of rotating stars – Dr Giovanni Mirouh Seismology of solar-type pulsators: outstanding observational results 09.30 – 10.30 – Dr Charlotte Gehan Long-period Pulsations of Intermediate-Mass Stars from 10.30 – 11.00 Planet Surveys – Ms Vera Wolthoff Seismology of coherent pulsators: what can we learn from pulsations and 10.30 – 11.30 binarity in early-type stars? – Dr Dominic Bowman 11.00 – 11.30 Binarity among Type II Cepheids – Dr Monika Jurković

11.30 – 12.30 Break 11.30 – 12.30 Break 12.30 – 13.30 Binary mass transfer – Dr Onno Pols 12.30 – 13.30 Interacting stars and asteroseismology – Dr Robert Izzard 13.30 – 14.00 Mass transfer and accretion disks – Mr David Hendriks 13.30 – 14.00 Experimental advances in explosive nuclear astrophysics – Dr Gavin Lotay 14.00 – 14.30 The post-mass transfer binary system KIC 10661783 – Mr Amadeusz Miszuda Galactic archaeology: (some) challenges posed by binary stars 14.00 – 15.00 – Dr Andrea Miglio 14.30 – 15.30 Break 15.30 – 17.00 Collaborative time for discussion 15.00 – 15.30 Break

15.30 – 17.00 Collaborative time for discussion

4 SURREY.AC.UK UNIVERSITY OF SURREY 5 PROGRAMME

DAY 3 – WEDNESDAY 20TH JANUARY DAY 4 – THURSDAY 21ST JANUARY

(GMT) (GMT)

09.00 – 09.30 Coffee/tea time and discussion 09.00 – 09.30 Coffee/tea time and discussion

Inversions in asteroseismology: dissecting the internal structure of stars Search for quiet stellar-mass black holes lurking in binary systems by 09.30 – 10.30 09.30 – 10.30 – Dr Gaël Buldgen asteroseismology from space – Prof Hiromoto Shibahashi 10.30 – 11.30 High precision measurements of eclipsing binary stars – Dr Pierre Maxted 10.30 – 11.30 Tidal forcing and dissipation in binary stars – Prof Gordon Ogilvie 11.30 – 12.30 Break 11.30 – 12.30 Break 12.30 – 13.00 Mapping pulsations in eclipsing binaries – Dr Barna Imre Bíró An eccentric binary system TYC4038-693-1 with a pulsating component A stochastic sampling method for the analysis of eclipsed pulsations 12.30 – 13.00 13.00 – 13.30 – Dr Erika Pakštienė – Mr András Bókon 13.00 – 14.00 Tidal asteroseismology: an observational perspective – Dr Zhao Guo 13.30 – 14.30 The effects of mixing on accreted material –Dr Richard Stancliffe Epsilon Cygni: a possible case of a very extreme heartbeat system 14.30 – 15.00 with a pulsating component – Dr Przemysław Walczak 14.00 – 14.30 – Mr Paul Heeren 15.00 – 15.30 Break 14.30 – 15.00 Single-sided pulsators – Prof Gerald Handler 15.30 – 17.00 Collaborative time for discussion 15.00 – 15.30 Break

15.30 – 17.00 Collaborative time for discussion

6 SURREY.AC.UK UNIVERSITY OF SURREY 7 PROGRAMME ABSTRACTS AND

DAY 5 – FRIDAY 22ND JANUARY PARTICIPANTS

MONDAY 18TH JANUARY Seismology of coherent pulsators: what can we learn from pulsations and binarity in (GMT) Seismology of solar-type pulsators: early-type stars? outstanding observational results 9.30 – 10.30 Machine learning in stellar physics – Dr Gregor Traven Dr Dominic Bowman, KU Leuven (Belgium) Dr Charlotte Gehan, Instituto de Astrofísica e Stars which possess a convective core during 10.30 – 11.00 Augmented Sliced Wasserstein Distances – Dr Yunpeng Li Ciências do Espaço, Universidade do Porto the play a critical role in (Portugal) 11.00 – 11.30 Pulsations in faint blue stars – Dr Conor Byrne stellar evolution theory. In particular, massive The last decade has witnessed the advent of 11.30 – 12.30 BREAK stars are important metal factories which ultra-high photometry space missions, with provide energy and chemical feedback to 12.30 – 13.30 Non-radial pulsations in Hot Subdwarf B Stars – CoRoT and Kepler giving birth to ensemble Dr Holly Preece their surroundings. However, current stellar asteroseismology and providing outstanding 13.30 – 14.30 Neutron stars – Dr Arnau Rios-Huguet evolution models contain large theoretical results for thousands of pulsating stars. uncertainties for these early-type stars. The 14.30 – 15.00 Concluding remarks – Prof Simon Jeffery The harvest continues with the ongoing uncertainties associated with interior rotation, TESS space mission and the future PLATO mixing and angular momentum transport mission expected to be launched by 2026. propagate throughout a star’s evolution This review will focus on solar-type pulsators, making it difficult to accurately determine with a particular emphasis on evolved masses and ages, with the situation becoming oscillating stars that offer the opportunity more complex in the case of binary systems. to study the physical conditions governing However, the high incidence rates of pulsation stellar cores through the mixed modes in their and binarity for early-type stars allow us to oscillation spectrum. I will review the theory break model degeneracies, uniquely probe behind solar-type pulsations and focus on stellar interiors, and calibrate the unknown elements of stellar structure as solar-type physics within stellar evolution models. In pulsators go through different evolutionary this review, I discuss the advances in our stages, before focusing on some of the understanding of early-type stars by means of major observational results obtained so far. asteroseismology and binarity. Asteroseismic modelling provides important constraints on ages, core masses, interior mixing,

Continued

8 SURREY.AC.UK UNIVERSITY OF SURREY 9 rotation and angular momentum transport Interacting stars and asteroseismology Experimental advances in explosive Galactic archaeology: (some) challenges for stars pulsating in coherent modes. Dr Robert Izzard, University of Surrey (UK) nuclear astrophysics posed by binary stars Furthermore, space photometry of eclipsing Models of stellar populations including Dr Gavin Lotay, University of Surrey (UK) Dr Andrea Miglio, binary systems containing a pulsating star only single stars are yesterday’s news: we Classical novae are among the most University of Birmingham (UK) facilitates binary asteroseismology, with now know that most stars more massive frequent and violent stellar explosions to In this review I will first touch upon some such systems yielding the most accurate than the are in multiple systems. Many occur in our . As such, they play of the recent advances in using large masses, radii and ages. Thanks to the of these are binaries or in higher-order a key role in determining its chemical samples of stars with asteroseismic recent Kepler and TESS space telescopes, multiples which are hierarchical so contain evolution. Recently, remarkable advances in constraints to reconstruct the assembly a wide range of diverse variability has been gravitationally bound effectively-single astronomy and meteoritics have produced history and evolution of the Milky Way. I discovered in early-type stars, which can be stars and binaries. I will review how these a wealth of observational data on these will then discuss examples on how binary exploited to constrain stellar structure and systems evolve and how their stars interact, cataclysmic astronomical events, giving us stars pose a serious threat to these evolution models for some of most massive including mass and angular momentum unprecedented insight into their properties. endeavours, and how one can identify and short-lived stars in the Universe. transfer, and stellar merging, with a focus However, a detailed understanding of this stars that had undergone interaction with on how interaction alters their evolution and latest observational data is severely hindered a companion by combining asteroseismic, hence their asteroseismological properties. by large uncertainties in the underlying astrometric, and spectroscopic data. nuclear physics processes, involving unstable nuclei, that drive such stellar scenarios.

Modern state-of-the-art accelerator facilities provide the means to resolve this issue, through their ability to recreate the conditions that occur in explosive stellar phenomena in terrestrial laboratories. In particular, it is now possible to obtain key experimental information on the rates of astrophysical processes that govern both the rate of energy release and pathway of nucleosynthesis in classical novae. In this talk, recent experimental studies of relevance for classical novae will be discussed.

10 SURREY.AC.UK UNIVERSITY OF SURREY 11 TUESDAY 19TH JANUARY Long-period Pulsations of Intermediate-Mass Binarity among Type II Cepheids Binary mass transfer Stars from Radial Velocity Planet Surveys Dr Monika Jurković, Dr Onno Pols, Seismology of rotating stars MsVera Wolthoff, ZAH-LSW Astronomical Observatory Belgrade (Serbia) Radboud University Nijmegen (Netherlands) Dr Giovanni M. Mirouh, University of Heidelberg (Germany) Type II Cepheids (T2Cs) were known to be The evolution of binary systems deviates University of Surrey (UK) Intermediate-mass (IM) stars (M>1.5Msun) are radially pulsating variable stars, with periods from that of single stars primarily owing to Rotation is ubiquitous in stars, it affects all difficult targets for radial velocity (RV) surveys from 1 to 150 days. This picture seems to be the possibility of mass transfer, giving rise stages of stellar evolution and associated while they are on the main sequence, due changing. T2Cs pulsating in a first overtone, to a wide range of phenomena including oscillations. While slowly-rotating solar-like to their hot atmospheres and fast rotation. and in the fundamental mode and first blue stragglers, barium stars, X-ray binaries, stars are well described by perturbative Therefore, the planet search has mainly overtone simultaneously were discovered in Type Ia supernovae and gravitational- treatments, rapid rotation is a notorious focused on evolved IM stars with most the Magellanic Clouds (MCs) from the Optical wave sources. Mass transfer can occur by source of complexity in so-called classical planet hosts being red giants (~100 known Gravitational Lensing Experiment (OGLE) means of two main processes, Roche-lobe pulsators. In this review, I will briefly today). However, the long-period behavior IV catalog. Type II Cepheids are divided overflow and stellar-wind mass transfer. In summarize the origin and impact of stellar of these stars is not well understood causing into subgroups according to their pulsation this talk I will give an overview of our current rotation, and present recent works that several planet candidates to be refuted period: BL Herculis (BLH), 1-4 days, W Virginis understanding of these processes: their crucially developed new approaches to after additional observations were made (WVir), 5-20 days, RV Tauri (RVT), 20-150 stability, efficiency, and consequences for the describe the internal rotation of a growing (e.g. Hatzes et al. 2018, Delgado Mena et days. Among them binary systems are found evolution of the binary . Special emphasis number of stars across the Hertzsprung- al. 2018, Reichert et al. 2019). So called in the sub-types: peculiar W Virginis (pWVir) will be on mass transfer from red giant and Russell diagram. I will focus on rapidly-rotating oscillatory convective modes (OCM), which stars (80% are in a binary systems) and RV AGB donors, which is expected to result in main-sequence stars, in which theory and have originally been proposed (Saio et al. Tauri stars. The pWVir systems OGLE-LMC- binaries with some of the least understood observations are finally converging thanks to 2015) to explain the long secondary periods T2CEP-098 and OGLE-LMC-T2CEP-211 are observed properties: intermediate-size the detection of regular patterns predicted of OGLE III giants with log(L/L_sun)>3 (and two of such binary systems from the Large (of several AU), peculiar abundances by the models. All these exciting results typical periods of several hundred days), Magellanic Cloud (LMC) that were studied in and substantial eccentricities. offer ways of exploiting the unprecedented were suggested as a possible origin for detail. The mass of the T2C in OGLE-LMC- wealth of data provided by the Corot, the signals in question. Since RVs are more T2CEP-098 was found to be 1.51± Msun, while Kepler and TESS space missions, and sensitive to low-amplitude pulsations (and in for the OGLE-LMC-T2CEP-211 the current light the way to great future advances particular to non-radial ones) than photometry, mass of the pulsating star is 0.64±0.02 Msun. with the upcoming PLATO mission. OCMs could potentially be picked up in RV This would suggest that in binary systems the planet searches for below the pulsating stars light curve resembles T2Cs, threshold. We present data from our 11 despite them having larger masses than the RV Lick survey and compare it to single T2Cs (which is ~0.5-0.6 Msun). The the expected period- relations RV Tauri sub-type of T2Cs show alternating for OCMs. Furthermore, we look at the minima and maxima in their light curves prominent scarcity of Hot and Warm Jupiters with long periods of variation. This makes (periods<90days) around IM stars and show their observation quite time consuming and that the combined effects of simple stellar challenging. From the studied RVT stars in equilibrium tides and Reimers’ mass loss the Milky Way it seems that those showing on the planetary orbits cannot reconcile a disc like distribution of dust seen in the the differences between main sequence Spectral Energy Distribution are in a binary and giant stage planet populations for stars systems. Another method to find these with M>2Msun (while for lower-mass giants, binaries is to use the light-time travel effect these planets are efficiently removed). (LITE). This was carried out for one third of T2Cs in the MCs in the OGLE-III catalog.

12 SURREY.AC.UK UNIVERSITY OF SURREY 13 Disky business: disk mass transfer The post-mass transfer binary system WEDNESDAY 20TH JANUARY High precision measurements of in Algol systems KIC 10661783 eclipsing binary stars Inversions in asteroseismology: Mr David Hendriks, University of Surrey (UK) Mr Amadeusz Miszuda Dr Pierre Maxted, Keele University (UK) dissecting the internal structure of stars It has become clear that a significant fraction (with Dr Wojciech Szewczuk, Dr Jadwiga The volume and quality of data available for Dr Gaël Buldgen, of stars has one or more companions. Stars Daszyńska-Daszkiewicz) stellar populations and exoplanet systems Observatoire de Genève (Switzerland) in a binary, or higher order, systems often University of Wroclaw (Poland) is now so good that the main obstacle to Inversion techniques are standard tools in interact by transferring mass, drastically KIC 10661783 is a detached post-Algol answering the big questions in exoplanet geophysics and helioseismology, leading altering their evolution compared to single binary system with a short . and galactic astrophysics is often the to tremendous successes. Meanwhile, their stars. The transfer of material from one star This is a double-lined eclipsing binary and missing physics in stellar models used to use in asteroseismology, although already to the other affects the mass ratio, orbital the stellar parameters of its components interpret these data. These surveys also foreseen in 1990s, was for long proscribed evolution and can even lead to the stars are determined with an accuracy below provide the tools that are needed to make as a result of the limited amount of data. merging together. This process is not always 1.5%. The main component is a delta Scuti very accurate and precise measurements The scenery changed dramatically with conservative, and in many systems we expect pulsating star. Up to now, 55 independent of stars in eclipsing binary systems. In this the CoRoT and Kepler missions, which some mass to have been lost in this process. pulsation frequencies were identified in talk I will review the theory behind making allowed the widespread use of sophisticated The transferred material does not always the 28-day Kepler light curve. We present accurate mass and radius measurements inference techniques in asteroseismic directly hit the accreting object, in certain results obtained from all available Kepler for stars in eclipsing binary systems, and investigations. In the current era of space- cases it forms an accretion disk. Accretion data which include a 769-day time interval. discuss how the analysis of carefully- based photometry missions such as TESS onto a star can affect the pulsational The Fourier analysis of the whole light curve, selected binary systems with state-of-the- and the future PLATO mission, these properties and the period of the pulsations corrected for the binary effects, reveals art techniques can be used to calibrate techniques are slowly but surely becoming of the accretion star. It is unclear whether 750 frequency peaks and those with the the next generation of stellar models. more routinely used, paving the way for disk accretion has a distinctly different effect highest amplitudes are concentrated in the more in-depth testing of stellar models. on the pulsations than direct accretion. In range of 20 - 30 c/d. In addition, we found accretion disks viscous processes within small-amplitude signals in the low-frequency I will review the current data, methodologies the disk transport the angular momentum range that can be manifestation of gravity- and physical information that can be outward and tidal interactions with the mode pulsations. Asteroseismic modelling extracted from asteroseismic data as edge of the disk are expected to transport with precisely determined fundamental well as discussing a interesting targets the excess angular momentum back into parameters allows to obtain more reliable where inversion techniques played or the binary orbit. Material at the outer edge constraints on other parameters of the may play a key role in testing the theory potentially carries a very large specific model and theory. In particular, our goal of stellar structure and evolution. angular momentum, and would some of that is to find corrections to the mean opacity material be lost from the disk before being profile to account for the whole frequency able to return its angular momentum to the range observed in the delta Scuti star. orbit, it could alter the orbital evolution, as well as estimates for the mass transfer efficiency. In this talk I will show several results of synthetic populations of Algol systems, and properties of disks in these systems. I will compare different assumptions of mass loss from these disks and show the effect that has on their further evolution.

14 SURREY.AC.UK UNIVERSITY OF SURREY 15 Mapping pulsations in eclipsing binaries A stochastic sampling method for the The effects of mixing on accreted material Binary star with a pulsating component Dr Barna Imre Bíró, Baja Observatory of the analysis of eclipsed pulsations Dr Richard Stancliffe, Hull University (UK) Dr Przemysław Walczak (with Prof Henryk University of Szeged (Hungary) Mr András Bókon, Mass transfer between binary stars is crucial Cugier), University of Wrocław (Poland) We explore the potential of eclipses in Department of Experimental Physics, to understanding a variety of classes of Studying the close binary stars evolution pose binary systems to provide information on University of Szeged (Hungary) astrophysical objects. Beyond the problems a challenge for present day astrophysicists. pulsations of their components. In particular, Pulsations in eclipsing binaries offer a unique of shifting mass from one star to another The very complicated interactions between we are interested in developing methods of opportunity to get information about the (as discussed elsewhere at this meeting) components hamper the interpretation of the analysis that use their modulating and surface surface intensity of the pulsation patterns is the issue of what happens to material observational data. Due to this, the binaries sampling effect to infer the surface patterns of themselves, with an exciting prospect of after it has been accreted. Does accreted with a pulsating component(s) are particularly the pulsations on the components of eclipsing direct mode identification in addition to material simply remain at the stellar surface, interesting since the seismic analysis binaries. Ultimately this could lead to a direct asteroseismologic analysis. One method or can it be mixed by some process into can shed light on the physical processes identification of the modes, and since the is the direct modeling of the pulsations the stellar interior? This issue is particularly occurring in the stars that undergo intensive eclipses are a purely geometric phenomenon, modulated by the eclipse phenomenon important for those of us interested in mass and angular momentum exchange. the whole procedure can stay largely (Direct Fitting, DF), using spherical studying nucleosynthesis in stars that are Here, we present an attempt to model the independent of asteroseismologic models, harmonics or as pulsation patterns. With the no longer around. In this contribution, I surface chemical abundances (H,He,C,N with only minimal assumptions involved. One overwhelmingly large number of detected will discuss the role that processes like and O) that can result from binary star method, Eclipse Mapping, takes an image pulsation frequencies obtained with space thermohaline mixing have in modifying the interactions and rotationally induced mixing reconstruction approach, requiring only observatories, however, the parameter surface compositions of low-mass stars, and of elements using MESA computing code. minimal physically feasible assumptions about space of the problems is also becoming how it complicates using their abundances Further constrains of the stellar structure the shape of the pulsation patterns (like axial too large to be tractable with conventional as probes of asymptotic giant branch of pulsating components are discussed. symmetry and periodicity across the stellar optimization methods. Therefore, I investigate nucleosynthesis. I will discuss what we think surface). Another more specific method, the application of stochastic MCMC we know, and do not know, about the mixing termed Direct Fitting, assumes generic methods to sample the parameter space, in of accreted material in carbon-enhanced spherical harmonics as eigenfunctions, and order to make the DF methods viable. The metal-poor stars. I will then discuss the also allows in principle the determination special configuration of discrete unordered possible implications for more metal-rich of the orientation of the symmetry axis of parameters (the mode numbers) requires systems, such as the barium and CH stars. the pulsations. We present our experience a special handling of them as so-called regarding the applicability of these methods category variables. I report our experience to real data, with an account of the limitations with this approach obtained during tests on and caveats that we have encountered during artificial data and application on real data these developments. We also present a (KIC 3858884), performed to examine the number of applications on systems observed capabilities and limitations of the method. by KEPLER (KIC 10661783, KIC 3858884).

16 SURREY.AC.UK UNIVERSITY OF SURREY 17 THURSDAY 21ST JANUARY Tidal forcing and dissipation in binary stars An eccentric binary system TYC4038-693-1 Tidal asteroseismology: Prof Gordon Ogilvie, with a pulsating component an observational perspective Search for quiet stellar-mass black University of Cambridge (UK) Dr Erika Pakštienė, Dr Zhao Guo, University of Cambridge (UK) holes lurking in binary systems by Many stars experience low-frequency Institute of Theoretical Physics and Astronomy, More than half of all stars reside in binaries asteroseismology from space gravitational tidal forcing by their stellar or Vilnius University (Lithuania) and tides can have a significant effect on Prof Hiromoto Shibahashi, planetary companions. The tidal response A binary star TYC4038-693-1 was discovered stellar oscillations. I will review the effect University of Tokyo (Japan) of the star generally consists of wavelike and at Moletai Astronomical Observatory from of tides on stellar oscillations from an Stars with an initial mass more than ~25Msun non-wavelike parts, with the wavelike part photometric observations with 35/50cm observational perspective, focusing primarily are thought to ultimately become black differing in character between radiative and Maksutov type telescope in 2016 (Pakstiene on intermediate and massive stars. Indirect holes. Then stellar-mass black holes should convective regions and often being sensitive et al. 2019). Since then we have collected evidence of tidal interactions is from the be ubiquitous but fewer than 20 have been to the rotation of the star. Dissipation of the additional multicolour photometric orbital synchronization/circularization of found in our Galaxy to date, all of which have tide leads to evolution of the spin and orbit observations of the system. The TESS has binary stars as well as the orbital decay been found through their X-ray emission. In on astronomical timescales. I will discuss also observed TYC4038-693-1 in the 18th and spin-orbit alignment of exoplanet host most cases these are soft X-ray transients several mechanisms of tidal dissipation sector. New photometric observations show stars. Thanks to precise measurements --- low-mass X-ray binaries whose optical and their efficiency, including recent work that the system has highly eccentric orbits. of the space missions, we are now able to counterparts are late type stars filling their on the effective viscosity of convective One of the components shows short periodic observe the manifestation of dynamical tides Roche lobes, leading to accretion onto black motions, as well as the dissipation of internal brightness variations intrinsic to d Scuti stars. unambiguously: tidally excited oscillations holes. In one case, the stellar-mass black waves by linear and nonlinear processes. Amplitude and frequency of these variations (TEOs), which are on top of the overall hole is in a high-mass X-ray binary whose vary with time. An increased gravitational heartbeat binary light curves from equilibrium optical counterpart is an early type star. Its interaction and tidal phenomena were tide. While Kepler observations offer us tens strong stellar winds are accreted by the black observed when the components moved of A, F- type heartbeat binaries with TEOs, hole, producing X-ray emission. It follows close to the periastrons. We also obtained missions such as BRITE and TESS added that X-ray-quiet stellar-mass black holes additional spectrometric observations with more OB type heartbeat binaries with TEOs. exist in wide binary systems. The discovery 165 cm telescope and high resolution Echelle The TEO amplitudes and phases can be used of black holes in the optical through their type spectrograph at Moletai Astronomical to identify the pulsation modes and constrain gravitational interactions would be a major Observatory. They allowed us to get stellar parameters. Enhance tidal dissipation scientific breakthrough. Recent space- radial velocity curves of the components, from resonance locking has been observed based photometry has made it possible to decompose their spectra and get some in a few binary systems. There has been measure phase or frequency modulation of parameters of the components. Preliminary possible evidence of tidally excited global pulsating stars to extremely high precision. analysis has shown that the components of Rossby modes and pure inertial modes in Such modulation is caused by orbital motion, the system are relatively young (~0.8 billion the convective core. New tidal phenomenon and its analysis offers the lower limit for the ) with masses between 1.55 and 1.96 includes the tidally trapped p- and f-mode as mass of the companion to the pulsating star. solar masses. As TYC4038-693-1 shows well as tidally perturbed modes in circular/ If the companions are non-luminous and if many phenomena intrinsic to binary systems, synchronized close binaries. We have entered the masses of the companions exceed the it makes this binary star a good candidate a golden era of tidal asteroseismology. mass limit for neutron stars (~3Msun), the for further analysis of the system, testing companions should be black holes. I will interaction of components in eccentric binary review the methodology, and analyses of systems, their evolution and behaviour some encouraging cases are demonstrated. of pulsating stars in such systems.

18 SURREY.AC.UK UNIVERSITY OF SURREY 19 Epsilon Cygni: a possible case of a very Single-sided pulsators FRIDAY 22ND JANUARY Augmented Sliced Wasserstein Distances extreme heartbeat system Prof Gerald Handler, Dr Yunpeng Li, University of Surrey (UK) Machine learning in stellar physics Mr Paul Heeren, ZAH-LSW Nicolaus Copernicus Astronomical Center While theoretically appealing, the application Dr Gregor Traven, Lund Observatory (Sweden) University of Heidelberg (Germany) Warsaw (Poland) of the Wasserstein distance to large-scale What is machine learning? This topic covers From a long-term RV survey of G and K giant The single-sided pulsators are a new type machine learning problems has been a vast range of applications of mathematical stars at Lick Observatory and the SONG of oscillating stars in close binary systems. hampered by its prohibitive computational algorithms on (observational) data. The telescope we have identified, among others, They appear to pulsate principally in one cost. The sliced Wasserstein distance and its astronomical community has already adopted a number of stellar binary systems that might hemisphere because their pulsation axes variants improve the computational efficiency many of such algorithms for diverse tasks harbor additional planetary companions. have been tilted into the orbital plane by the through random projection, yet they suffer that range from visualisation to classification One peculiar case is the highly eccentric tidal forces exerted by a close companion from low projection efficiency because the to understanding the basic physics. It is (e~0.93) binary system Epsilon Cygni, whose star. At the time of this writing, we have majority of projections result in trivially small obvious that with current and future facilities, RV curve shows variations with a period of discovered three of those systems in TESS values. In this talk, I will introduce a new family we are facing an explosion of data, which about 290 days that closely resemble the space photometry data as well as noticed of distance metrics, called augmented sliced calls for faster and more efficient analysis signal of a Jupiter mass planet orbiting the some related cases in the literature. Aside Wasserstein distances (ASWDs), constructed methods. This explains the popularity of evolved primary component. However, the from all pulsators being Delta Scuti stars, and by first mapping samples to higher- machine learning (ML) algorithms, however, Keplerian elements of the putative planet’s the orbital periods being shorter than two dimensional hypersurfaces parameterized it is important to understand the advantages orbit undergo strong temporal evolution, days, all those systems are different in terms by neural networks. We show that the and limitations of any novel techniques, especially during the periastron passage of their pulsational behaviour, secondary hypersurfaces can be optimized by gradient and it is also interesting to look behind of the stellar companion; also, in extensive star and Roche Lobe filling factor. We will ascent efficiently. We provide the condition the curtains into some details of how the dynamical simulations of the system no stable present an overview of those stars, as well under which the ASWD is a valid metric and actual algorithms work. We shall review a solutions could be found. Therefore, we as our initial results and work in progress. show that this can be obtained by an injective selection of utilities of ML algorithms on investigate alternative explanations for the neural network architecture. Numerical results examples of different datasets. Most will be RV signal, amongst them the possibility of demonstrate that the ASWD significantly based on stellar spectra from large all-sky the primary component being tidally excited outperforms other Wasserstein variants for surveys such as RAVE, APOGEE, GALAH, during the close periastron flybys of the stellar both synthetic and real-world problems. but we’ll also touch on other observations companion. We compare the system to known that provide insight into stellar physics, such heartbeat systems from the literature, and as photometry and asteroseismology. An even though the separation between the two important and outstanding question in the components in Epsilon Cygni is much larger context of analysis of astronomical data as compared to all other heartbeat binaries, is how to provide reliable uncertainties of due to its very high eccentricity Epsilon derived quantities, and so we will look at Cygni might fall onto the extreme edge of how different ML techniques address this the distribution of tidally excited systems. As issue. We’ll also explore some details of how many evolved stars are known to undergo e.g. dimensionality reduction or different oscillations with long periods between about kinds of neural networks work. Finally, some 200 to 1500 days, there might be oscillation recently developed methods will hopefully modes present in Epsilon Cygni that could stimulate a discussion on where the future is be excited towards long-lasting dynamical taking us in terms of ML use in astronomy. tides. A more thorough analysis of the system would require modelling the composition of the evolved primary star in combination with the tidal influence of the stellar companion.

20 SURREY.AC.UK UNIVERSITY OF SURREY 21 Pulsations in faint blue stars Non-radial pulsations in Hot Subdwarf Neutron star binaries and Dr Conor Byrne, Armagh Observatory (UK) B Stars fundamental physics and University of Warwick (UK) Dr Holly Preece, Max-Planck-Institut for Dr Arnau Rios-Huguet, Blue large-amplitude pulsators (BLAPs) are Astrophysics (Germany) University of Surrey (UK) hot, high-amplitude pulsating stars which Hot subdwarf B stars are He core burning GW170817 was the first telltale detection of have been recently discovered by both objects which have lost their H burning a neutron-star binary, a true multimessenger the OGLE survey and the Zwicky Transient envelopes through binary interactions. event appearing as a kilonova across the Facility (ZTF). It has been proposed that These stars have been predicted and electromagnetic spectrum and with a distinct these objects are low-mass pre-white dwarfs observed to have non-radial oscillations. gravitational wave signal. This extraordinary and that their pulsations are driven by the The majority of observed pulsators have event had several implications across physics, opacity of iron-group elements. To verify the gravity modes although some have pressure from cosmology to nucleosynthesis and, evolutionary status of these stars, a sequence modes. A small sample of hybrid pulsators of course, to binary stars. In this talk, I will of post-common-envelope stellar models have also been discovered which exhibit briefly review why neutron-star mergers are were computed using the MESA stellar both p and g modes. Serval sdBs have been promising and how multimessenger signals evolution code and the pulsation properties observed with Kepler, K2 and Tess which provide insights on the structure of neutron of the resultant low-mass pre-white dwarfs yield high quality lightcurves. The analysis stars. These insights complement existing were examined through non-adiabatic the lightcurves of pulsating sdB stars gives developments in radio and X-ray astronomy, analysis with the GYRE stellar oscillation insight into the interiors of He core burning that probe compact objects in different ways. I code. By accounting for the effects of atomic objects which are on their way to the white will discuss how, ultimately, these joint efforts diffusion and radiative levitation, it is shown dwarf cooling track. This talk shall give an will help us determine the equation of state of that a large region of instability exists from overview of the major results in the field. dense matter and how, with this knowledge, effective temperatures of 30,000 K up to we can probe the strong interaction. at least 50,000 K and at a wide range of surface gravities. This instability region encompasses both the OGLE pulsators and the ZTF pulsators, indicating they have a similar evolutionary history. The morphology of the instability region is found to be sensitive to assumptions made about the common envelope phase of evolution. This indicates that BLAPs may be a useful tool for developing our understanding of common envelope evolution. Estimates are made regarding the range of periods, masses, temperatures, and gravities in which further such pulsators might be observed in ongoing and future all-sky photometric surveys.

22 SURREY.AC.UK UNIVERSITY OF SURREY 23 FACULTY OF ENGINEERING AND PHYSICAL SCIENCE

University of Surrey Guildford, GU2 7XH, UK

surrey.ac.uk