UNC-CH “Chalk Talk” Astronomy Seminar

Brad Barlow, High Point University

“The Little Stars that Could: Unlocking the Potential of the Hot Subdwarf B Stars”

Despite their unassuming nature, hot subdwarf B (sdB) stars have important roles to play in our understanding of various subfields of astrophysics, including binary star evolution, exoplanets, and even cosmology. UNC’s suite of instrumentation is naturally suited for studies of these relatively bright and blue objects. SOAR/Goodman will serve as the primary instrument in the international EREBOS collaboration, which will spend the next several years studying low-mass sdB binaries and determining whether substellar objects can survive red giant engulfment. We will also use SOAR/Goodman to conduct a radial velocity survey of hot subdwarfs in the Southern hemisphere and identify massive sdB+WD binaries that might be candidate SN Ia progenitors. To address the mysteries of the long-period sdB+F/G/KV systems, we will continue monitoring their radial velocities over 5-10 years using SALT/HRS. Upcoming surveys including TESS and LSST will likely provide other interesting sdB systems for follow-up studies. All of the above observational work will inform improvements in stellar evolution codes like MESA. Finally, we will use precise eclipse timing measurements from the Evryscope and SKYNET to discover circumbinary planets, detect orbital decay due to gravitational wave emission, and measure stellar and planetary masses in a relatively model-independent way, using a variant of the Roemer delay method.