Knowledge Bank

The Kepler field contains two distinct groups of cool evolved stars: the red giant branch (RGB) of shell hydrogen burning stars and the red clump (RC) of core helium burning stars Typically, RC stars are hotter than RGB stars and are restricted to a narrower range of intermediate luminosities. In this project, the focus is to look at unusually hot and unusually cool RGB stars, focusing on those with luminosities below the RC. I used spectroscopic data from APOGEE and Kepler asteroseismology to define the bottom edge of the red clump. Hot stars below this threshold were defined as unusually hot RGB stars. I also discovered an unusually cool RGB population. I followed this up with a systematic study of these unusual stars-- first seismically, and then further spectroscopically. We then further analyze the stellar oscillations of the hot star region by looking at their power spectra, theoretical correspondence, SIMBAD information, and seismic information to explain their behavior. The results from the hot star region correspond to a truly unusual population of stars, containing binaries, rapid rotators, and other rare types of stars.