The potential of the dynamical asteroseismology, the research area that builds upon the synergies between the asteroseismology and binary stars research fields, is discussed in this manuscript. We ...touch upon the following topics: i) the mass discrepancy observed in intermediate-to high-mass main-sequence and evolved binaries as well as in the low mass systems that are still in the pre-main sequence phase of their evolution; ii) the rotationally induced mixing in high-mass stars, in particular how the most recent theoretical predictions and spectroscopic findings compare to the results of asteroseismic investigations; iii) internal gravity waves and their potential role in the evolution of binary star systems and surface nitrogen enrichment in high-mass stars; iv) the tidal evolution theory, in particular how its predictions of spin-orbit synchronisation and orbital circularisation compare to the present-day high-quality observations; v) the tidally-induced pulsations and their role in the angular momentum transport within binary star systems; vi) the scaling relations between fundamental and seismic properties of stars across the entire HR-diagram.
In this context, the recent report1 of an approximately 70-solar-mass (M®) black hole in the galactic binary system LB-1 challenges conventional theories of massive-star evolution, stellar winds and ...core-collapse supernovae, thus requiring a more exotic scenario to explain the existence and properties of this system2,3. ...we used a barycentre method as well as a bisector method using an identical mask as that in Liu et al.1, to estimate the apparent radial-velocity shift resulting from the combined Ha profile, obtaining similar results using both methods. ...there is no evidence for a large mass ratio, and hence also no evidence for a large absolute mass of a black hole. Data availability The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. https://doi.org/10.1038/s41586-020-2216-x Received: 6 December 2019 Accepted: 27 February 2020 Published online: 29 April 2020 Acknowledgements We acknowledge support from the Fonds Wetenschappelijk Onderzoek (FWO, Research Foundation Flanders) under project IDs G0F8H6N, G0B3818N, 12ZY520N, G0H5416N and GST-D6267-I002519N, and from the Onderzoeksraad (Research Council), KU Leuven under project IDs C16/17/007, C16/18/005 and C14/17/082.
Abstract
The fifth iteration of the Sloan Digital Sky Survey is set to obtain optical and near-infrared spectra of ∼5 million stars of all ages and masses throughout the Milky Way. As a part of these ...efforts, APOGEE and BOSS Young Star Survey (ABYSS) will observe ∼10
5
stars with ages <30 Myr that have been selected using a set of homogeneous selection functions that make use of different tracers of youth. The ABYSS targeting strategy we describe in this paper is aimed to provide the largest spectroscopic census of young stars to date. It consists of eight different types of selection criteria that take the position on the H-R diagram, infrared excess, variability, as well as the position in phase space in consideration. The resulting catalog of ∼200,000 sources (of which a half are expected to be observed) provides representative coverage of the young Galaxy, including both nearby diffuse associations as well as more distant massive complexes, reaching toward the inner Galaxy and the Galactic center.
We present a review of the latest results of studies of the class of mass-accreting pulsating components of semi-detached eclipsing binaries known as oEA stars. The application of the techniques of ...asteroseismology to this class of stars unlocks new pathways for gaining a deeper understanding of the short-term evolution and magnetic activity of binary stars. We report the discovery of 49 new pulsating components of eclipsing binaries, based on data from NASA’s TESS space telescope. Recent observational results on the pulsation characteristics of these stars are summarized. The effects of the interaction of the magnetic and spot activity of the Roche-lobe-filling component of a system with the pulsations of the mass-accreting component are discussed.
The evolved slowly pulsating B star 18 Peg Irrgang, Andreas; De Cat, Peter; Tkachenko, Andrew
EPJ Web of Conferences,
01/2017, Volume:
152
Conference Proceeding, Journal Article
Peer reviewed
Open access
The predicted width of the upper main sequence in stellar evolution models depends on the empirical calibration of the convective overshooting parameter. Despite decades of discussions, its precise ...value is still unknown and further observational constraints are required to gauge it. Irrgang et al. (1) showed that the B3 III giant 18 Peg is one of the most evolved members of the class of slowly pulsating B (SPB) stars and, thus, bears tremendous potential to derive a tight lower limit for the width of the upper main sequence. In addition, 18 Peg turns out to be part of a single-lined spectroscopic binary system with an eccentric, more than 6-year orbit. The orbital solution, in combination with the absence of additional signatures of the secondary component in the spectroscopic data and the spectral energy distribution, lead to the conclusion that all the observations of 18 Peg are fully compatible with the assumption that the secondary component is either a main-sequence star with a mass of 1-4 M⊙ or a neutron star.
The interior physics of stars is currently not well constrained for early-type stars. This is particularly pertinent for multiple systems, as binary interaction becomes more prevalent for more ...massive stars, which strongly affects their evolution. High-precision photometry from the Transiting Exoplanet Survey Satellite (TESS) mission offers the opportunity to remedy the dearth of observations of pulsating stars that show evidence of binary interaction, specifically pulsating mass-accreting components of semi-detached Algol-type eclipsing binary (oEA) systems. We present the TESS light curve of the circular eclipsing binary system U Gru (TIC 147201138), which shows evidence of free heat-driven pressure modes and a series of tidally perturbed pressure modes. We highlight the asteroseismic potential of studying pulsating stars in binary systems, and demonstrate how tidal asteroseismology can be applied to infer the influence of binary interaction on stellar structure.
Asteroseismology gives us the opportunity to look inside stars and determine their internal properties, such as the radius and mass of the convective core. Based on these observations, estimations ...can be made for the amount of the convective boundary mixing and envelope mixing of such stars and for the shape of the mixing profile in the envelope. However, these results are not typically included in stellar evolution models. We aim to investigate the impact of varying convective boundary mixing and envelope mixing in a range based on asteroseismic modelling in stellar models up to the core collapse, both for the stellar structure and for the nucleosynthetic yields. In this first study, we focus on the pre-explosive evolution and we evolved the models to the final phases of carbon burning. This set of models is the first to implement envelope mixing based on internal gravity waves for the entire evolution of the star. We used the MESA stellar evolution code to simulate stellar models with an initial mass of 20 from zero-age main sequence up to a central core temperature of 109 K, which corresponds to the final phases of carbon burning. We varied the convective boundary mixing, implemented as `step-overshoot', with the overshoot parameter ( ) in the range 0.05 - 0.4. We varied the amount of envelope mixing ( ) in the range 0-6 with a mixing profile based on internal gravity waves. To study the nucleosynthesis taking place in these stars in great detail, we used a large nuclear network of 212 isotopes from 1H to 66Zn. Enhanced mixing according to the asteroseismology of main-sequence stars, both at the convective core boundary and in the envelope, has significant effects on the nucleosynthetic wind yields. This is especially the case for and whose wind yields increase by ten orders of magnitude compared to those of the models without enhance envelope mixing. Our evolutionary models beyond the main sequence diverge in yields from models based on rotational mixing, having longer helium-burning lifetimes and lighter helium-depleted cores. We find that the asteroseismic ranges of internal mixing calibrated from core hydrogen-burning stars lead to similar wind yields as those resulting from the theory of rotational mixing. Adopting the seismic mixing levels beyond the main sequence, we find earlier transitions to radiative carbon burning compared to models based on rotational mixing because they have lower envelope mixing in that phase. This influences the compactness and the occurrence of shell mergers, which may affect the supernova properties and explosive nucleosynthesis.
It has been known for several decades that transport of chemical elements is induced by the process of microscopic atomic diffusion. Yet the effect of atomic diffusion, including radiative ...levitation, has hardly been studied in the context of gravity-mode pulsations of core hydrogen burning stars. In this paper we study the difference in the properties of such modes for models with and without atomic diffusion. We perform asteroseismic modeling of two slowly rotating A- and F-type pulsators, KIC 11145123 ( ) and KIC 9751996 ( ), respectively, based on the periods of individual gravity modes. For both stars, we find models whose g-mode periods are in very good agreement with the Kepler asteroseismic data, keeping in mind that the theoretical/numerical precision of present-day stellar evolution models is typically about two orders of magnitude lower than the measurement errors. Using the Akaike Information Criterion, we have made a comparison between our best models with and without diffusion and found very strong evidence for signatures of atomic diffusion in the pulsations of KIC 11145123. In the case of KIC 9751996 the models with atomic diffusion are not able to explain the data as well as the models without it. Furthermore, we compare the observed surface abundances with those predicted by the best-fitting models. The observed abundances are inconclusive for KIC 9751996, while those of KIC 11145123 from the literature can better be explained by a model with atomic diffusion.
Context . Eclipsing spectroscopic double-lined binaries are the prime source of precise and accurate measurements of masses and radii of stars. These measurements provide a stringent test for models ...of stellar evolution that are consistently reported to contain major shortcomings. Aims . The mass discrepancy observed for eclipsing spectroscopic double-lined binaries is one of the manifestations of the shortcomings in stellar evolution models. The problem reflects the inability of the models to accurately predict the effective temperature and surface gravity or luminosity of a star for a given mass. Our ultimate goal is to provide an observational mapping of the mass discrepancy and to propose a recipe for its solution. Methods . We initiated a spectroscopic monitoring campaign of 573 candidate eclipsing binaries classified as such based on their TESS light curves. In this work, we present a sub-sample of 83 systems for which orbital phase-resolved spectroscopy has been obtained and subsequently analysed with the methods of least-squares deconvolution and spectral disentangling. In addition, we employed TESS space-based light curves to provide photometric classification of the systems according to the type of their intrinsic variability. Results . We confirmed 69 systems as being either spectroscopic binaries or higher-order multiple systems. We classified twelve stars as single, and we found two more objects that cannot be decisively classified as intrinsically variable single or binary stars. Moreover, 20 eclipsing binaries were found to contain at least one component that exhibits stellar oscillations. Spectroscopic orbital elements were obtained with the spectral disentangling method and reported for all systems classified as either SB1 or SB2. The sample presented in this work contains both detached and semi-detached systems and covers a range in the effective temperature and mass of the star of T eff ∊ 7000,30 000 K and M ∊ 1.5, 15 M ⊙ , respectively. Conclusions . Based on a comparison of our own results with those published in the literature for well-studied systems, we conclude that there is an appreciable capability of the spectral disentangling method to deliver precise and accurate spectroscopic orbital elements from as few as six to eight orbital phase-resolved spectroscopic observations. Orbital solutions obtained this way are accurate enough to deliver age estimates with an accuracy of 10% or better for intermediate-mass F-type stars, an important resource for the calibration of stellar evolution models for future space-based missions, such as PLATO. Finally, despite the small size relative to the 573 systems that we will ultimately monitor spectroscopically, the sample presented in this work is already suitable to kick off observational mapping of the mass discrepancy in eclipsing binaries.
We set out to determine stellar labels from low-resolution survey spectra of hot stars, specifically OBA stars with
T
eff
≳ 7500 K. This fills a gap in the scientific analysis of large spectroscopic ...stellar surveys such as LAMOST, which offers spectra for millions of stars at
R ~
1800 and covers 3800 Å ≤
λ ≤
9000 Å. We first explore the theoretical information content of such spectra to determine stellar labels via the Cramér-Rao bound. We show that in the limit of perfect model spectra and observed spectra with signal-to-noise ratio ~50–100, precise estimates are possible for a wide range of stellar labels: not only the effective temperature,
T
eff
, surface gravity, log
g
, and projected rotation velocity,
v
sin
i
, but also the micro-turbulence velocity,
v
mic
, helium abundance,
N
He
/
N
tot
, and the elemental abundances C/H, N/H, O/H, Si/H, S/H, and Fe/H. Our analysis illustrates that the temperature regime of
T
eff
~ 9500 K is challenging as the dominant Balmer and Paschen line strengths vary little with
T
eff
. We implement the simultaneous fitting of these 11 stellar labels to LAMOST hot-star spectra using the Payne approach, drawing on Kurucz’s ATLAS12/SYNTHE local thermodynamic equilibrium spectra as the underlying models. We then obtain stellar parameter estimates for a sample of about 330 000 hot stars with LAMOST spectra, an increase by about two orders of magnitude in sample size. Among them, about 260 000 have good
Gaia
parallaxes (
ω/σ
ω
>
5), and their luminosities imply that ≳95% of them are luminous stars, mostly on the main sequence; the rest are evolved lower luminosity stars, such as hot subdwarfs and white dwarfs. We show that the fidelity of the results, particularly for the abundance estimates, is limited by the systematics of the underlying models as they do not account for nonlocal thermodynamic equilibrium effects. Finally, we show the detailed distribution of
v
sin
i
of stars with 8000–15 000 K, illustrating that it extends to a sharp cutoff at the critical rotation velocity,
v
crit
, across a wide range of temperatures.
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