Possible anti-correlations between pulsation amplitudes and the disk growth of Be stars in giant-outbursting Be X-ray binaries
Masafumi Niwano, Michael M. Fausnaugh, Ryan M. Lau, Kishalay De, Roberto Soria, George R. Ricker, Roland Vanderspek, Michael C. B. Ashley, Nicholas Earley, Matt… 展开作者
Masafumi Niwano, Michael M. Fausnaugh, Ryan M. Lau, Kishalay De, Roberto Soria, George R. Ricker, Roland Vanderspek, Michael C. B. Ashley, Nicholas Earley, Matthew J. Hankins, Mansi M. Kasliwal, Anna M. Moore, Jamie Soon, Tony Travouillon, Mahito Sasada, Ichiro Takahashi, Yoichi Yatsu, Nobuyuki Kawai
备注：
17 pages, 27 figures, 6 tables, accepted for publication in MNRAS
Be X射线双星中X射线爆发的机制仍是一个谜，而理解其星周盘对于解决质量转移问题至关重要。尤其重要的是，识别导致质量抛射并进而形成星盘的Be星活动（例如脉动）。因此，我们研究了一个包含五个Be X射线双星的样本中光学流量振荡与红外（IR）超量之间的关系。将Lomb-Scargle技术应用于凌星系外行星巡天卫星（TESS）的高频率光学光变曲线，我们在每个源中检测到周期范围为3至24小时的若干显著振荡模式。我们还利用Palomar Gattini-IR的J波段光变曲线测量了这五个源的红外超量（星盘增长的代理指标）。在五个源中的四个里，我们发现红外超量与主要流量振荡模式的振幅之间存在反相关。这一结果与非径向脉动驱动质量抛射的传统观点不一致。我们提出了另一种情景：Be星内部的温度变化导致脉动活跃状态与质量抛射活跃状态之间的转换。
英文摘要：
The mechanism of X-ray outbursts in Be X-ray binaries remains a mystery, and understanding their circumstellar disks is crucial for a solution of the mass-transfer problem. In particular, it is important to identify the Be star activities (e.g., pulsations) that cause mass ejection and, hence, disk formation. Therefore, we investigated the relationship between optical flux oscillations and the infrared (IR) excess in a sample of five Be X-ray binaries. Applying the Lomb-Scargle technique to high-cadence optical light curves from the Transiting Exoplanet Survey Satellite (TESS), we detected several significant oscillation modes in the 3 to 24 hour period range for each source. We also measured the IR excess (a proxy for disk growth) of those five sources, using J-band light curves from Palomar Gattini-IR. In four of the five sources, we found anti-correlations between the IR excess and the amplitude of the main flux oscillation modes. This result is inconsistent with the conventional idea that non-radial pulsations drive mass ejections. We propose an alternative scenario where internal temperature variations in the Be star cause transitions between pulsation-active and mass-ejection-active states.
Context: [abbreviated] Aims: Kepler data of three known Be stars are re-visited to establish their pulsational nature and assess the properties of additional, non-pulsational variations. The three program stars turned out to be one inactive Be star, one active, continuously outbursting Be star, and one Be star transiting from a non-outbursting into an outbursting phase, thus forming an excellent sample to distill properties of Be stars in the various phases of their life-cycle. Methods: [abbreviated] Results: The short-term photometric variability of Be stars must be disentangled into a stella…
The discovery of non-radial pulsations (NRP) in the Be/X binaries of the Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley 2005) provided a new approach to understand these complex systems, and, at the same time, favoured the synergy between two different fields: stellar pulsations and X-ray binaries. This breakthrough was possible thanks to the MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty et al. 2009). Our objective is to study the short-term variability of Ga…
Using BRITE photometric data for several close binary systems we address the problem of damping pulsations in close binary systems due to proximity effects. Because of small number statistics, no firm conclusion is given, but we find pulsations in three relatively close binaries. The pulsations in these binaries have, however, very low amplitudes.
There exists a special class of X-ray pulsars that exhibit very slow pulsation of $P_{\rm spin}>1000$ s in the high mass X-ray binaries (HMXBs). We have studied the temporal and spectral properties of these superslow pulsation neutron star binaries in hard X-ray bands with INTEGRAL observations. Long-term monitoring observations find spin period evolution of two sources: spin-down trend for 4U 2206+54 ($P_{\rm spin}\sim 5560$ s with $\dot{P}_{\rm spin}\sim 4.9\times 10^{-7}$ s s$^{-1}$) and long-term spin-up trend for 2S 0114+65 ($P_{\rm spin}\sim 9600$ s with $\dot{P}_{\rm spin}\sim -1\times …
Ground-based optical photometry of the counterparts of High-Mass X-ray Binaries (HMXBs) has revealed the presence of periodic modulations on timescales of ~0.3-0.5 d. More recent space-based observations Corot and TESS of OB and Be stars have shown that pulsations caused by p and g modes are common in early type stars. We have therefore undertaken a systematic search for variability in the optical counterparts of 23 HMXBs (mostly neutron star systems, but including one black hole, Cyg X-1) using TESS data primarily in 2 min cadence mode. After removing the orbital period modulation in four sys…
Classical Be stars, regardless of spectral subtype, display multiperiodic light modulations in the frequency range 0.1-12 d$^{-1}$, when observed with high-cadence and long duration. This behaviour is attributed to non-radial pulsations and/or rotation of the Be star. The main goal of this work is to investigate the fast photometric variability of the optical counterparts to Be/X-ray binaries and compare the general patterns of such variability with the Galactic population of classical Be stars. We analyzed 21 sources with TESS. High-cadence photometry with two ground-based telescopes was also…
RR Lyn is a detached eclipsing binary with a 9.95 d orbit containing two A-stars: one metallic-lined and one possibly metal-poor. We use the light curve from the TESS satellite and two sets of published radial velocity measurements to determine the properties of the system to high precision. We find masses of 1.939 +/- 0.007 and 1.510 +/- 0.003 Msun, and radii of 2.564 +/- 0.019 and 1.613 +/- 0.013 Rsun. After adjusting published effective temperatures upwards by 200 K we find a good agreement with theoretical models for a solar chemical composition and an age of 1 Gyr, and a distance slightly…
We present a method for finding binaries among pulsating stars that were observed by the Kepler Mission. We use entire four-year light curves to accurately measure the frequencies of the strongest pulsation modes, then track the pulsation phases at those frequencies in 10-d segments. This produces a series of time-delay measurements in which binarity is apparent as a periodic modulation whose amplitude gives the projected light travel time across the orbit. Fourier analysis of this time-delay curve provides the parameters of the orbit, including the period, eccentricity, angle of ascending nod…
CCD observations of 68 eclipsing binary systems, candidates for containing δ Scuti components, were obtained. Their light curves are analysed using the PERIOD04 software for possible pulsational behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to determine their geometrical and pulsational characteristics. Spectroscopic observations of WY Cet and UW Cyg were…
Using data from eROSITA, the soft X-ray instrument aboard Spectrum-Roentgen-Gamma (SRG), we report the discovery of two new hard transients, eRASSU J050810.4-660653 and eRASSt J044811.1-691318, in the Large Magellanic Cloud. We also report the detection of the Be/X-ray binary RX J0501.6-7034 in a bright state. We initiated follow-up observations to investigate the nature of the new transients and to search for X-ray pulsations coming from RX J0501.6-7034. We analysed the X-ray spectra and light curves from our XMM-Newton observations, obtained optical spectra using the South African Large Tele…
The study of pulsating stars in eclipsing binaries holds the promise of combining two different ways of measuring the physical properties of a star to obtain improved constraints on stellar theory. Gravity (g) mode pulsations such as those found in $γ$ Doradus stars can be used to probe rotational profiles, mixing and magnetic fields. Until recently few $γ$ Doradus stars in eclipsing binaries were known. We have discovered g-mode pulsations in four detached eclipsing binary systems from light curves obtained by the Transiting Exoplanet Survey Satellite (TESS) and present an analysis of their e…
Context. Thanks to the high-precision photometry from space missions such as Kepler and TESS, tidal perturbations and tilting of pulsations have been detected in more than a dozen binary systems. However, only two of these were g-mode pulsators. Aims. We aim to detect tidally perturbed g modes in additional binary systems and characterise them observationally. Methods. We perform a custom data reduction of the available Kepler and TESS photometry of a well-studied sample of 35 binary systems with gamma Doradus pulsators. For each target, we model the binary signal using a sum of 100 sine waves…
Ensemble pulsational characteristics of eclipsing binaries containing $β$ Cep stars observed by the TESS mission
University of Nigeria, Nsukka（尼日利亚恩苏卡大学）；KU Leuven（荷语鲁汶大学）；Newcastle University（纽卡斯尔大学）；Radboud University Nijmegen（奈梅亨拉德堡德大学）；Max Planck Institut für Astronomie（马克斯·普朗克天文学研究所）；Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）
We present the Dynamic Eclipse Mapping (DEM) method designed specifically to reconstruct the surface intensity patterns of non-radial stellar oscillations in eclipsing binaries. The method needs a geometric model of the binary, accepts the light curve and the detected pulsation frequencies on input, and on output yields estimates of the pulsation patterns, in form of images -- thus allowing a direct identification of the surface mode numbers$(\ell,m)$. Since it has minimal modelling requirements and can operate on photometric observations in arbitrary wavelength bands, DEM is well suited to an…
The present work contains light curve, spectroscopic and asteroseismic analyses for KIC 04851217 and KIC 10686876. These systems are detached eclipsing binaries hosting a pulsating component of delta Scuti type and have been observed with the unprecedented accuracy of the Kepler space telescope. Using ground based spectroscopic observations, the spectral types of the primary components of the systems were estimated as A6V and A5V for KIC 04851217 and KIC 10686876, respectively, with an uncertainty of one subclass. The present spectral classification together with literature radial velocities c…
Eclipsing binaries with a $δ$ Sct component are powerful tools to derive the fundamental parameters and probe the internal structure of stars. In this study, spectral analysis of 6 primary $δ$ Sct components in eclipsing binaries has been performed. Values of $T_{\rm eff}$, $v \sin i$, and metallicity for the stars have been derived from medium-resolution spectroscopy. Additionally, a revised list of $δ$ Sct stars in eclipsing binaries is presented. In this list, we have only given the $δ$ Sct stars in eclipsing binaries to show the effects of the secondary components and tidal-locking on the …
Pulsations and binarity are both common features of massive stars. The study of pulsating massive stars in eclipsing binary systems hold great potential for constraining stellar structure and evolution theory. However, prior to the all-sky Transiting Exoplanet Survey Satellite (TESS) mission, few such systems had been discovered or studied in detail. We have inspected the TESS light curves of a large number of eclipsing binaries known to contain high-mass stars, and compiled a list of 18 objects which show intrinsic variability. The light curves were modelled both to determine the physical pro…
Eclipsing binary systems with pulsating components offer a unique possibility to accurately measure the most important parameters of pulsating stars, to study their evolution, and to test the pulsation theory. I will show what we can learn about the pulsating stars from the analysis of such systems and how we can do it. Special attention will be paid to the mass, radius, p-factor, and distance determination. Although the core of the method is based on the observations of double-lined eclipsing spectroscopic binaries, with the help of the pulsation theory, it is possible to measure absolute par…
Based on 2-minute cadence TESS data from sectors 1-50, we report the results of the systematic extraction of $δ$ Scuti-type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period $P_{\rm dom}$, orbital period $P_{\rm orb}$, and effective temperature $T_{\rm eff}$. As a consequence, 216 targets are likely $δ$ Scuti stars (123 new), 11 likely $γ$ Doradus…
The results of our six year systematic observational survey on candidate eclipsing binaries with a delta Sct component are briefly presented. A new catalogue for this kind of systems as well as the properties of their delta Sct members are also presented. The comparison between the components-pulsators and the single delta Sct stars shows that both the evolution and the pulsating properties differ significantly. Finally, we introduce the new era of studying stellar pulsations using high accuracy data from Kepler mission and emphasizing the great opportunities that are now opened for a deep kno…
We report on extended photometry of two pulsating sdB stars in close binaries. For both cases, we use rotational splitting of the pulsation frequencies to show that the sdB component rotates much too slowly to be in synchronous rotation. We use a theory of tidal interaction in binary stars to place limits on the mass ratios that are independent of estimates based on the radial velocity curves. The companions have masses below 0.26 M\odot. The pulsation spectra show the signature of high-overtone g-mode pulsation. One star, KIC 11179657, has a clear sequence of g-modes with equal period spacing…
Results from a six year systematic observational survey on candidate eclipsing binaries with a $δ$ delta Sct component are presented. More than a hundred systems with component(s) of A-F spectral types were observed in the frame of this survey in order to be checked for possible pulsational behaviour. The 14% (13 cases) of the currently known such systems were discovered during this survey. Using all the available information from the literature, an updated list with all the currently known systems of this type is presented, while possible correlations between their pulsational and binarity pr…
The catalogue contains 199 confirmed cases of binary systems containing at least one pulsating component of δ Scuti type. The sample is divided into subgroups in order to describe the properties and characteristics of the δ Sct type stars in binaries according to their Roche geometry. Demographics describing quantitatively our knowledge for these systems as well as the distributions of their pulsating components in the Mass-Radius, Colour-Magnitude and Evolutionary Status-Temperature diagrams are presented and discussed. It is shown that a threshold of ~13 days of the orbital period regarding …
We substantially update the capabilities of the open-source software instrument Modules for Experiments in Stellar Astrophysics (MESA). MESA can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. New MESA capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow MESA to accurately simulate advanced burning stages needed to construct supernova progenitor models. Implicit hydrodynamics with shocks can now be …
Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suffer of the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extensio…
The survey phase of the Kepler Mission includes a number of hot subdwarf B (sdB) stars to search for nonradial pulsations. We present our analysis of two sdB stars that are found to be g-mode pulsators of the V1093 Her class. These two stars also display the distinct irradiation effect typical of sdB stars with a close M-dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear e…
Recent observation of the tidally-excited stellar oscillations in the main-sequence binary KOI-54 by the KEPLER satellite provides a unique opportunity for studying dynamical tides in eccentric binary systems. We develop a general theory of tidal excitation of oscillation modes of rotating binary stars, and apply our theory to tidally excited gravity modes (g-modes) in KOI-54. The strongest observed oscillations, which occur at 90 and 91 times the orbital frequency, are likely due to prograde m=2 modes (relative to the stellar spin axis) locked in resonance with the orbit. The remaining flux o…
Modelling ellipsoidal variables with known distances can lead to exact determination of the masses of both components, even in the absence of eclipses. We present such modelling using light and radial velocity curves of ellipsoidal red giant binaries in the LMC, where they are also known as sequence E stars. Stars were selected as likely eccentric systems on the basis of light curve shape alone. We have confirmed their eccentric nature and obtained system parameters using the Wilson-Devinney code. Most stars in our sample exhibit unequal light maxima as well as minima, a phenomenon not observe…
Existence of pulsating stars in eclipsing binaries has been known for decades. These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipsing and pulsation variations. The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy ($\leq$1\%), while the pulsations are a unique way to probe the stellar interior via oscillation frequencies. There are different types of pulsating stars existing in eclipsing binaries. One of them is the Delta Scuti variables. Currently, the known number of Delta Scuti sta…
The final evolution of stars in the mass range 70 - 140 solar masses is explored. Depending upon their mass loss history and rotation rates, these stars will end their lives as pulsational pair-instability supernovae producing a great variety of observational transients with total durations ranging from weeks to millennia and luminosities from 10$^{41}$ to over 10$^{44}$ erg s$^{-1}$. No non-rotating model radiates more than $5 \times 10^{50}$ erg of light or has a kinetic energy exceeding $5 \times 10^{51}$ erg, but greater energies are possible, in principle, in magnetar-powered explosions w…
We analyse TESS light curves for 70 southern $λ$ Boo stars to identify binaries and to determine which of them pulsate as $δ$ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 percent of $λ$ Boo stars pulsate as $δ$ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the $λ$ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 $λ$ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and $δ$ Sct pulsation. We use Petersen …
Tidal forces in eccentric binary stars known as heartbeat stars excite detectable oscillations that shed light on the processes of tidal synchronization and circularization. We examine the pulsation phases of tidally excited oscillations (TEOs) in heartbeat binary systems. The target list includes four published heartbeat binaries and four additional systems observed by {\it Kepler}. To the first order, the pulsation phases of TEOs can be explained by the geometric effect of the dominant $l=2$, $m=0$, or $\pm 2$ modes assuming pulsations are adiabatic. We found that this simple theoretical int…
For the EL CVn candidate 1SWASPJ181417.43+481117.0 (WASP 1814+48), we secured the first spectroscopic observations between 2015 April and 2021 March. Using the echelle spectra, the radial velocities (RVs) of the primary star were measured with its atmospheric parameters of $T_{\rm eff,1}=7770\pm130$ K and $v_1$$\sin$$i=47\pm6$ km s$^{-1}$. We fitted our single-lined RVs and the TESS light curve simultaneously. From the binary modeling, we determined the following fundamental parameters for each component: $M_1=1.659\pm0.048$ $M_\odot$, $R_1=1.945\pm0.027$ $R_\odot$, and $L_1=12.35\pm0.90$ $L_\…
Binary systems anchor many of the fundamental relations relied upon in asteroseismology. Masses and radii are rarely constrained better than when measured via orbital dynamics and eclipse depths. Pulsating binaries have much to offer. They are clocks, moving in space, that encode orbital motion in the Doppler-shifted pulsation frequencies. They offer twice the opportunity to obtain an asteroseismic age, which is then applicable to both stars. They enable comparative asteroseismology -- the study of two stars by their pulsation properties, whose only fundamental differences are the mass and rot…
Context. We present our findings on 18 formerly known ZZ Ceti stars observed by the TESS space telescope in 120s cadence mode during the survey observation of the southern ecliptic hemisphere. Aims. We focus on the frequency analysis of the space-based observations, comparing the results with the findings of the previous ground-based measurements. The frequencies detected by the TESS observations can serve as inputs for future asteroseismic analyses. Methods. We performed standard pre-whitening of the data sets to derive the possible pulsation frequencies of the different targets. In some case…
KIC 9851944 is a short period ($P=2.16$ days) eclipsing binary in the {\it Kepler} field of view. By combining the analysis of {\it Kepler} photometry and phase resolved spectra from Kitt Peak National Observatory and Lowell Observatory, we determine the atmospheric and physical parameters of both stars. The two components have very different radii ($2.27R_{\odot}$, $3.19R_{\odot}$) but close masses ($1.76 M_{\odot}$, $1.79M_{\odot}$) and effective temperatures ($7026$K, $6902$K), indicating different evolutionary stages. The hotter primary is still on the main sequence (MS), while the cooler …
The study of eclipsing binaries is our primary source of measured properties of normal stars, achieved through analysis of light and radial velocity curves of eclipsing systems. The study of oscillations and pulsations is increasingly vital for determining the properties of single stars, and investigating the physical phenomena active in their interiors. Combining the two methods holds the promise of establishing stringent tests of stellar evolutionary theory, and of calibrating model-dependent asteroseismology with empirically measured stellar properties. I review recent advances and outline …
The Magellanic Clouds host a large population of high-mass X-ray binary (HMXB) systems, but although the Large Magellanic Cloud (LMC) is an order of magnitude more massive than the Small Magellanic Cloud, significantly fewer HMXBs are known. We conducted a search for new HMXBs in XMM-Newton observations, which we performed to investigate supernova remnant candidates in the supergiant shells LMC5 and LMC7. The three observed fields are located in regions, which were little explored in X-rays before. We analysed the XMM-Newton data to look for sources with hard X-ray spectrum and counterparts wi…
From a set of thirteen cataclysmic binaries that were discovered in the Swift Burst Alert Telescope (BAT) survey, we conducted time-resolved optical spectroscopy and/or time-series photometry of eleven, with the goal of measuring their orbital periods and searching for spin periods. Seven of the objects in this study are new optical identifications. Orbital periods are found for seven targets, ranging from 81 minutes to 20.4 hours. PBC J0706.7+0327 is an AM Herculis star (polar) based on its emission-line variations and large amplitude photometric modulation on the same period. Swift J2341.0+7…
Context. This research paper contains light curve modelling, spectroscopy and detailed asteroseismic studies for four out of five in total semidetached eclipsing binaries with a delta Scuti component, that have been detected to date through Kepler mission, namely KIC 06669809, KIC 10581918, KIC 10619109 and KIC 11175495. Aims. The goal is to study the pulsational characteristics of the oscillating stars of the systems as well as to estimate their absolute parameters and enrich the so far poor sample of this kind of systems. Methods. Ground based spectroscopic observations provide the means to …
Measuring phase modulation in pulsating stars has proved to be a highly successful way of finding binary systems. The class of pulsating main-sequence A and F variables known as delta Scuti stars are particularly good targets for this, and the \textit{Kepler} sample of these has been almost fully exploited. However, some \textit{Kepler} $δ$ Scuti stars have incorrect temperatures in stellar properties catalogues, and were missed in previous analyses. We used an automated pulsation classification algorithm to find 93 new $δ$ Scuti pulsators among tens of thousands of F-type stars, which we then…
Measurement of at least three independent parameters, for example, mass, radius and spin frequency, of a neutron star is probably the only way to understand the nature of its supranuclear core matter. Such a measurement is extremely difficult because of various systematic uncertainties. The lack of knowledge of several system parameter values gives rise to such systematics. Low-mass X-ray binaries, which contain neutron stars, provide a number of methods to constrain the stellar parameters. Joint application of these methods has a great potential to significantly reduce the systematic uncertai…
CW Cep is an early B-type eclipsing binary with mass measurement precisions better than 1 \%. We report the discovery of pulsation signatures in the TESS time-series data of the system observed during Sectors 17 and 18. Our binary modeling indicates that the target star is a partially-eclipsing detached system with masses of 12.95 $M_\odot$ and 11.88 $M_\odot$ and radii of 5.52 $R_\odot$ and 5.09 $R_\odot$ in an eccentric orbit of $e$ = 0.0305. The distance to the eclipsing system, 928 $\pm$ 36 pc, is much more precise than the Gaia distance of 962 $\pm$ 453 pc. Applying multifrequency analyse…
Gamma Doradus stars (hereafter gamma Dor stars) are gravity-mode pulsators of spectral type A or F. Such modes probe the deep stellar interior, offering a detailed fingerprint of their structure. Four-year high-precision space-based Kepler photometry of gamma Dor stars has become available, allowing us to study these stars with unprecedented detail. We selected, analysed, and characterized a sample of 67 gamma Dor stars for which we have Kepler observations available. For all the targets in the sample we assembled high-resolution spectroscopy to confirm their F-type nature. We found fourteen b…
The two objects 1SWASP J150822.80-054236.9 and 1SWASP J160156.04+202821.6 were initially detected from their SuperWASP archived light curves as candidate eclipsing binaries with periods close to the short-period cut-off of the orbital period distribution of main sequence binaries, at ~0.2 d. Here, using INT spectroscopic data, we confirm them as double-lined spectroscopic and eclipsing binaries, in contact configuration. Following modelling of their visual light curves and radial velocity curves, we determine their component and system parameters to precisions between ~2 and 11%. The former sy…
Tidally tilted pulsators (TTPs) are an intriguing new class of oscillating stars in binary systems; in such stars, the pulsation axis coincides with the line of apsides, or semi-major axis, of the binary. All three TTPs discovered so far have been $δ$~Scuti stars. In this Letter, we report the first conclusive discovery of tidally tilted pulsations in a subdwarf B (sdB) star. HD 265435 is an sdB--white dwarf binary with a 1.65-hr period that has been identified and characterized as the nearest potential Type Ia supernova progenitor. Using TESS 20-s cadence data from Sectors 44 and 45, we show …
