Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: $δ$ Scuti stars seem to be characterized with seismic indexes such as the large separation ($Δν$). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power ($ν_{\rm max}$) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of $δ$ Scuti stars seem to be.
Characterizing bright $δ$ Scuti pulsators using TESS lightcurves
Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理研究所）；Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理学中心）；Institute for Astronomy, University of Hawaii（夏威夷大学天体物理研究所）
Identifying 850 delta Scuti pulsators in a narrow Gaia colour range with TESS 10-minute full-frame images
Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理研究所）；School of Physics, University of New South Wales（新南威尔士大学物理学院）；UNSW Data Science Hub, University of New South Wales（新南威尔士大学数据科学中心）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理学中心）
Revisiting bright delta Scuti stars and their period-luminosity relation with TESS and Gaia DR3
University of Pennsylvania（宾夕法尼亚大学）；Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理研究所）；Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University（奥胡斯大学物理与天文系恒星天体物理中心）；Centre for Astrophysics, University of Southern Queensland（昆士兰南部大学天体物理中心）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）
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…
Statistical analysis of asteroseismic indices and stellar parameters of TESS-observed $δ$ Scuti stars
Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文学与空间科学学院）；Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick（华威大学物理学院聚变、太空与天体物理学中心）；Institute of Geophysics, University of Tehran（德黑兰大学地球物理学研究所）；Department of Physics, Faculty of Science, University of Qom（库姆大学理学院物理系）；Instituto de Astrofísica de Andalucía - CSIC（安达卢西亚天体物理研究所-西班牙国家科研委员会）；Departamento de Física Teórica y del Cosmos, Universidad de Granada（格拉纳达大学理论与宇宙物理学系）；Ulugh Beg Astronomical Institute, Uzbekistan Academy of Sciences（乌兹别克斯坦科学院乌鲁格别克天文研究所）
Unveiling $δ$ Scuti and $γ$ Doradus Hybrid Pulsation of HD 53166 and HD 53349 Plus Rich Frequencies in HD 52788 -- Catalogs of 70552 $δ$ Sct and 8080 $γ$ Dor
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…
Metallic-line A (Am) stars are main-sequence stars of around twice the mass of the Sun that show element abundance peculiarities in their spectra. The radiative levitation and diffusive settling processes responsible for these abundance anomalies should also deplete helium from the region of the envelope that drives delta Scuti pulsations. Therefore, these stars are not expected to be delta Scuti stars, which pulsate in multiple radial and nonradial modes with periods of around 2 hours. As part of the NASA TESS Guest Investigator Program, we proposed photometric observations in 2-minute cadenc…
We present the first asteroseismic results for $δ$ Scuti and $γ$ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilise the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung-Russell diagram using Gaia DR2 data. Included within our sample are the eponymous members of two pulsator classes, $γ$ Doradus and SX Phoenicis. Our sample of pulsating intermediate-mass stars observed by TESS also allows us to confront theoretical models of pulsation driving in the classical instability strip for the fir…
Multiple regular frequency spacings in $δ$ Scuti stars from automated analysis of TESS oscillation spectra
Tata Institute of Fundamental Research（塔塔基础研究所）；Indian Institute of Astrophysics（印度天体物理研究所）；LIRA, Observatoire de Paris, Université PSL, Sorbonne Universit’e, Universit’e Paris Cit’e, CY Cergy Paris Universit’e, CNRS（拉伊尔实验室，巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，塞吉-蓬图瓦兹大学，法国国家科学研究中心）
AI Hya has been known as an eclipsing binary with a monoperiodic $δ$ Sct pulsator. We present the results from its {\it TESS} photometry observed during Sector 7. Including our five minimum epochs, the eclipse timing diagram displays the apsidal motion with a rate of $\dotω$ = 0.075$\pm$0.031 deg year$^{-1}$, which corresponds to an apsidal period of U = 4800$\pm$2000 years. The binary star model represents that the smaller, less massive primary component is 427 K hotter than the pulsating secondary, and our distance of 612$\pm$36 pc is in good agreement with the $Gaia$ distance of 644$\pm$26 …
Asteroseismology of 35 Kepler and TESS $δ$ Scuti stars near the red edge of the instability strip. The limitations of $δ$ Scuti stars for dating open clusters
TESS observations of the Pleiades cluster: a nursery for delta Scuti stars
Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理学研究所）；Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理中心）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University（奥胡斯大学物理与天文系恒星天体物理中心）；Department of Physics and Astronomy, University of North Carolina at Chapel Hill（北卡罗来纳大学教堂山分校物理与天文系）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森尼天体物理中心）
We announce the discovery of pulsations in HD 23642, the only bright eclipsing system in the Pleiades, based on light curves from the Transiting Exoplanet Survey Satellite (TESS). We measure 46 pulsation frequencies and attribute them to delta Scuti pulsations in the secondary component. We find four l=1 doublets, three of which have frequency splittings consistent with the rotation rate of the star. The dipole mode amplitude ratios are consistent with a high stellar inclination angle and the stellar rotation period agrees with the orbital period. Together, these suggest that the spin axis of …
Discovery and Characterization of Three New High-amplitude delta Scuti Stars from TESS Observations
Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Instituto de Astrofísica de Andalucía - CSIC（安达卢西亚天体物理研究所-西班牙国家研究委员会）；Ulugh Beg Astronomical Institute, Uzbekistan Academy of Sciences（乌兹别克斯坦科学院乌鲁伯格天文研究所）；Samarkand State University（撒马尔罕国立大学）
From sector 1--44 {\em TESS} observations, 19 new roAp stars, 103 ostensibly non-peculiar stars with roAp-like frequencies and 617 $δ$~Scuti stars with independent frequencies typical of roAp stars were found. Examination of all chemically peculiar stars observed by {\em TESS} resulted in the discovery of 199 Ap stars which pulsate as $δ$~Sct or $γ$~Dor variables. The fraction of pulsating Ap stars is the same as the fraction of pulsating chemically normal stars. There is no distinct separation in frequency or radial order between chemically peculiar $δ$~Sct stars and roAp stars. In fact, all …
TESS Observations of Seven Newly Identified High-amplitude $δ$ Scuti Stars
Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick（华威大学物理系聚变、太空与天体物理中心）；Institute of Geophysics, University of Tehran（德黑兰大学地球物理学研究所）；Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台光学天文重点实验室）；Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University（西安交通大学物理学院教育部非平衡合成与调控凝聚态物质重点实验室）；Ulugh Beg Astronomical Institute, Uzbekistan Academy of Sciences（乌兹别克斯坦科学院乌鲁格别克天文研究所）
Pulsating stars occupy a significant place in the H-R diagram and it was thought that all stars inside the classical instability strip should pulsate. However, recent studies showed that there are many non-pulsating stars placed inside the classical instability strip. The existence of these non-pulsating stars is still a mystery. To deeply understand the properties of these non-pulsating and pulsating stars, one needs precise fundamental stellar parameters (e.g mass). For this purpose, the eclipsing binaries are unique systems. Hence, in this study, we present the TESS data analysis of one can…
Classification of over 50000 TESS stars in sectors 1-18 has resulted in the detection of 766 pulsating main sequence B stars as well as over 5000 $δ$ Scuti, 2300 $γ$ Doradus and 114 roAp candidates. It is found that a distinct group of $β$ Cephei stars, defined as B stars with frequencies greater than 2.5 d$^{-1}$ and predicted by models, does not exist. Instead, high frequencies are to be found over the whole B-star range, eventually merging with $δ$ Scuti stars. The cool B stars pulsating in high frequencies are the Maia variables. It is shown that Maia variables are not rapidly-rotating $β$…
Early-type main-sequence pulsating stars such as \ds{} variables are one of the least explored class of targets in the search for exoplanets. Pulsation timing (PT) is an alternative technique to the most effective search methods. It exploits the light-travel-time effect (LTTE) to infer the presence of additional massive bodies around a pulsating star by measuring a periodic phase modulation of its signal. PT has been extremely successful in discovering and characterizing stellar binaries when it was applied to high-precision light curves over long temporal baselines, such as those delivered by…
IM Per is a triple star system whose eclipsing pair masses and radii are accurate to within 1 \%. The TESS light curve of the program target exhibits partial eclipses and multiple oscillations with mmag-level amplitudes. It is found that the oscillations affect eclipse timing measurements. Binary modeling of the high-quality TESS data indicates that the eclipsing components of the triple system are twin dwarfs with parameters of $M_2$/$M_1$ = 0.995, $R_2$/$R_1$ = 0.901, and $Δ$($T_{\rm eff,1}$--$T_{\rm eff,2}$) = 12 K in an eccentric ($e$ = 0.049), detached configuration. The third light of $l…
Unveiling the properties of pulsating low-mass helium-core white dwarfs through TESS asteroseismology I. First results
Universidad Nacional de La Plata（拉普拉塔国立大学）；CONICET-UNLP（阿根廷国家科学研究委员会-拉普拉塔国立大学）；City University of New York Graduate Center（纽约市立大学研究生院）；KU Leuven（荷语鲁汶大学）；Queens College, City University of New York（纽约市立大学皇后学院）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Boston University（波士顿大学）
Pulsating stars are remarkable objects for stellar astrophysics. Their pulsation frequencies allow us to probe the internal structure of stars. One of the most known groups of pulsating stars is $δ$ Scuti variables which could be used to understand the energy transfer mechanism in A-F type stars. Therefore, in the current study, we focused on the discovery of $δ$ Scuti stars. For this investigation, we followed some criteria. First, we inspected TESS database by eye and discovered some single stars that exhibit pulsation-like behaviour. Our second criterion is $T_{\rm eff}$ and $\log g$ range.…
Using TESS 20-sec cadence data, we have discovered an unusual combination of pulsating stars in what we infer to be a binary system. The binary consists of a standard $δ$ Scuti star with pulsations over the range 32-41 d$^{-1}$; this is in a likely wide orbit with a hot subdwarf B (sdB) star, which itself has a large-amplitude p-mode pulsation at 524 d$^{-1}$. We establish constraints on the period of the putative binary by using radial velocity measurements of the $δ$~Scuti star and show that any sdB companion star must orbit with a period greater than a few tens of days. Our identification o…
The $δ$ Scuti pulsator occurrence as a function of age, $T_{\rm eff}$, rotation, and metallicity
Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院悉尼天体物理研究所）；Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理中心）
Machine learning for understanding pulsating stars I: the non-linear phenomenon in δ Scuti stars
Instituto de Astrofísica de Andalucía (CSIC)（安达卢西亚天体物理研究所（西班牙科学委员会））；Embry-Riddle Aeronautical University (ERAU)（埃姆布里-里德尔航空大学）；Departament d’Astronomia i Astrofísica, Universitat de Valéncia（瓦伦西亚大学天文与天体物理系）；The Exploration Company（探索公司）
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…
$TESS$ photometric data of LS~Cam from sectors 19, 20 and 26 are analysed. The obtained power spectra from sectors 19 and 20 show multiple periodicities - orbital variations ($P_{orb} = 0.14237$ days), slightly fluctuating superorbital variation ($ P_{so} \approx 4.03$ days) and permanent negative superhump ($P_{-sh} = 0.1375$ days). In sector 26 an additional positive superhump ($P_{+sh} = 0.155$ days) is present. Using relations from literature, the mass ratio and the masses of the two components are estimated to be $q =0.24$, $M_1 = 1.26M_\odot$, and $M_2 = 0.30 M_\odot$ respectively.
F type stars are characterised by several physical processes such as different pulsation mechanisms, rotation, convection, diffusion, and magnetic fields. The rapidly rotating delta Scuti star beta Cas can be considered as a benchmark star to study the interaction of several of these effects. We investigate the pulsational and magnetic field properties of beta Cas. We also determine the star's apparent fundamental parameters and chemical abundances. Based on photometric time series obtained from three different space missions (BRITE-Constellation, SMEI, and TESS), we conduct a frequency analys…
We present the results of our survey searching for new white dwarf pulsators for observations by the TESS space telescope. We collected photometric time-series data on 14 white dwarf variable-candidates at Konkoly Observatory, and found two new bright ZZ Ceti stars, namely EGGR 120 and WD 1310+583. We performed the Fourier-analysis of the datasets. In the case of EGGR 120, which was observed on one night only, we found one significant frequency at 1332 microHz with 2.3 mmag amplitude. We successfully observed WD 1310+583 on eight nights, and determined 17 significant frequencies by the whole d…
We characterize an all-sky catalog of ${\sim} 8,400$ $δ$ Scuti variables in ASAS-SN, which includes ${\sim} 3,300$ new discoveries. Using distances from \textit{Gaia} DR2, we derive period-luminosity relationships (PLRs) for both the fundamental mode and overtone pulsators in the $W_{JK}$, $V$, Gaia DR2 $G$, $J$, $H$, $K_s$ and $W_1$ bands. We find that the overtone pulsators have a dominant overtone mode, with many sources pulsating in the second overtone or higher order modes. The fundamental mode pulsators have metallicity dependent periods, with $\log_{10} (\rm P){\sim}-1.1$ for $\rm [Fe/H…
We analyse the pulsating behaviour of TIC 308396022 observed by the TESS mission. The star is a high-amplitude $δ$ Sct star (HADS) that shows a very rich amplitude spectrum using the 3-yr light curve. Among these frequencies, the strongest peak of $f_{1}= 13.20362567(12) \rm{d^{-1}}$ is identified as the radial fundamental mode, and we also find the first and second overtones ($f_2$ and $f_3$). In the low frequency range (< 2.5 $\rm{d^{-1}}$), 22 peaks are identified to be gravity modes, which show a regular period spacing of about 2460\,s and have the angular degree $l = 1$. The period spacin…
We present a complex study of the eclipsing binary system, AB Cas. The analysis of the whole TESS light curve, corrected for the binary effects, reveals 112 significant frequency peaks with 17 independent signals. The dominant frequency $f_1 = $17.1564 d$^{-1}$ is a radial fundamental mode. The $O-C$ analysis of the times of light minima from over 92 years leads to a conclusion that due to the ongoing mass transfer the system exhibits a change of the orbital period at a rate of 0.03 s per year. In order to find evolutionary models describing the current stage of AB Cas, we perform binary evolu…
Discovery of the First Octupole Pulsation Mode in a delta Scuti Star: A Stationary l = 3 Sectoral Mode
HUN–REN–SZTE Stellar Astrophysics Research Group（匈牙利科学院-塞格德大学恒星天体物理学研究组）；Department of Physics, Kavli Institute for Astrophysics and Space Research, M.I.T.（麻省理工学院物理系卡弗里天体物理学与空间研究研究所）；Department of Astronomy, Cornell University（康奈尔大学天文学系）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）；Centre for Space Research, North-West University（西北大学太空研究中心）；Jeremiah Horrocks Institute, University of Lancashire（兰开夏大学杰里迈亚·霍克斯研究所）；Harvard University（哈佛大学）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；TAPIR, Mailcode 350-17, California Institute of Technology（加州理工学院TAPIR（邮件代码350-17））；Baja Astronomical Observatory of University of Szeged（塞格德大学巴亚天文台）；Konkoly Observatory, Research Centre for Astronomy and Earth Sciences（匈牙利科学院地球科学研究中心孔科利天文台）；ELTE Eötvös Loránd University, Gothard Astrophysical Observatory（罗兰大学哥塔德天体物理观测站）
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 …
