Insights Into Stellar Evolution and Beyond from Hot Subluminous Stars

Over the past ten years, the European Space Agency’s Gaia mission has uncovered nearly 100,000 stars located between the tip of the white dwarf cooling sequence and main sequence in the H-R diagram. Collectively referred to as hot subluminous stars, several types of objects have evolutionary tracks passing through or near this location, including pre-extremely low mass white dwarfs, core He-fusing hot subdwarf stars, post-blue horizontal branch stars, cataclysmic variables, subdwarf A stars, and more. Some neutron star spider binaries can even exhibit similar colors and luminosities due to the effects of irradiation on their cool companions. Essentially all hot subluminous stars share one common trait: binary interactions are necessary for their formation. Here I will present several research projects that leverage this fact to gain insights into stellar evolution, Roche lobe overflow processes, common envelope ejection, and other interesting astrophysical phenomena. The broader impacts of this work touch on gravitational wave physics, Type 1a supernovae, the impact of late-stage stellar evolution on exoplanets, and more. I will end by briefly discussing plans for developing low-cost, low-resolution spectrographs to assist in these studies and follow-up observations of transients generated by Argus, LSST, and other photometric surveys.