Short-period pulsating hot-subdwarf stars observed by TESS

I. Southern ecliptic hemisphere^⋆

¹ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
e-mail: andysbaran@gmail.com
² Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, USA
³ Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, 19C Allée du 6 Août, 4000 Liège, Belgium
⁴ Recogito AS, Storgaten 72, 8200 Fauske, Norway
⁵ South African Astronomical Observatory, Observatory 7935, South Africa
⁶ Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
⁷ IRAP, CNRS, UPS, CNES, Université de Toulouse, 14 av. Edouard Belin, 31400 Toulouse, France
⁸ Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65 Ondřejov, Czech Republic
⁹ Astroserver.org, Fő tér 1, 8533 Malomsok, Hungary
¹⁰ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
¹¹ Department of Physics and Astronomy, Aarhus University, NyMunkegade 120, 8000 Aarhus C, Denmark
¹² Department of Physics and Astronomy, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa

Received: 5 September 2022
Accepted: 19 October 2022

Abstract

We present results of a Transiting Exoplanet Survey Satellite (TESS) search for short-period pulsations in compact stellar objects observed in years 1 and 3 of the TESS mission, during which the southern ecliptic hemisphere was targeted. We describe the TESS data used and the details of the search method. For many of the targets, we use unpublished spectroscopic observations to classify the objects. From the TESS photometry, we clearly identify 43 short-period hot-subdwarf pulsators, including 32 sdB stars, eight sdOB stars, two sdO stars, and, significantly, one He-sdOB star, which is the first of this kind to show short-period pulsations. Eight stars show signals at both low and high frequencies, and are therefore “hybrid” pulsators. We report the list of prewhitened frequencies and we show the amplitude spectra calculated from the TESS data. We make an attempt to identify possible multiplets caused by stellar rotation, and we select four candidates with rotation periods between 1 and 12.9 days. The most interesting targets discovered in this survey should be observed throughout the remainder of the TESS mission and from the ground. Asteroseismic investigations of these data sets will be invaluable in revealing the interior structure of these stars and will boost our understanding of their evolutionary history. We find three additional new variable stars but their spectral and variability types remain to be constrained.