A Search for Subdwarf B Binaries Using Pulsation Timing from TESS

Abstract Hot subdwarf B (sdB) stars are post-main-sequence stars of high temperature and gravity. Approximately 30% of sdBs exhibit stable pressure and/or gravity-mode pulsations, which can be used via the timing method to test for companion stars and determine their orbital solutions. We used short cadence data from the Transiting Exoplanet Survey Satellite (TESS) to search for previously undiscovered companions to sdBs. In this paper, we focus on searching for companions with orbital periods shorter than 13.5 days which are detectable within one sector of TESS data (about 27 days). The timing method requires that we derive pulsation frequencies in subsets of data significantly shorter than the periods we are searching for, which we set at 0.5–1.5 day. We investigated ten sdB stars with previously detected p -mode pulsations for which at least one p -mode pulsation remains detectable with a signal-to-noise ratio > 4 within data subsets of duration 0.5–1.5 day. We find that two (TIC 202354658 and TIC 69298924) of these ten sdB stars likely have white-dwarf companions and set limits on companion masses for the other eight sdB stars.