New Hot Subdwarf Variables from Gaia eDR3

Abstract

We present a search for new variable hot subdwarfs from Gaia eDR3 using the Zwicky Transient Facility DR9 and the 2.1 m Otto Struve Telescope at McDonald Observatory. We report the discovery of 22 HW Vir binaries, 24 reflection effect binaries, and 14 ellipsoidally modulated systems. Candidate selection for our high-speed observations was based on object location on the Gaia color-magnitude diagram and on intrinsic variability, which we estimate from the Gaia G flux uncertainties. Notable discoveries include a candidate 72 min period sdB+WD binary and two short period HW Vir binaries with periods around 67 min and 79 min, which includes the shortest-period eclipsing sdB+dM/BD discovered to date.