Pulse Timing Discovery of a Three-day Companion to the Hot Subdwarf BPM 36430
Abstract
Hot subdwarf B stars are core-helium-burning objects that have undergone envelope stripping, likely by a binary companion. Using high-speed photometry from the Transiting Exoplanet Survey Satellite, we have discovered the hot subdwarf BPM 36430 is a hybrid sdBVrs pulsator exhibiting several low-amplitude g-modes and a strong p-mode pulsation. The latter shows a clear, periodic variation in its pulse arrival times. Fits to this phase oscillation imply BPM 36430 orbits a barycenter approximately 10 light-seconds away once every 3.1 days. Using the CHIRON echelle spectrograph on the CTIO 1.5 m telescope, we confirm the reflex motion by detecting a radial-velocity variation with semiamplitude, period, and phase in agreement with the pulse timings. We conclude that a white dwarf companion with minimum mass of ≈0.42 M ⊙ orbits BPM 36430. Our study represents only the second time a companion orbiting a pulsating hot subdwarf or white dwarf has been detected from pulse timings and confirmed with radial velocities.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2022
- DOI:
- 10.3847/1538-4357/ac9384
- arXiv:
- arXiv:2209.09909
- Bibcode:
- 2022ApJ...939...57S
- Keywords:
-
- Binary stars;
- Stellar pulsations;
- 154;
- 1625;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 pages, 5 figures, 4 tables. Accepted for publication in the Astrophysical Journal