The Discovery and Characterization of an Ultracompact Hot Subdwarf and Brown Dwarf Binary System

Abstract

Stellar binary systems are astronomical objects made of two stars gravitationally bound to each other. In some of these systems, the stars are so close that they interact with each other and affect the formation and evolution of one another. As a result, understanding these objects can provide insight into various stellar processes and astrophysical phenomena. In my project, I focused on studying a type of ultra-compact binary system called an HW Vir class binary – which is comprised of a hot sub dwarf and a brown dwarf. Because HW Vir systems can only be produced through the common envelope effect (CEE), understanding their physical parameters allows us to better understand the limitations of the CEE. For example, by studying binaries with the lowest mass companion that have survived the CEE, it allows us to draw conclusions about the lower bound on the companion mass that is able to survive envelope ejection. In my thesis, I outline the methods I used to search for these binary systems and model the lightcurve of ZTFJ2203+4824, a 78-minute orbital period HW Vir class binary that I discovered.