Evolution of Compact Binaries and Related Objects

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Some of the most astrophysically interesting phenomena are associated with binary and multiple star systems containing degenerate and/or compact objects. They span the gamut from high energy ?-ray bursts to the most luminous explosions observed in the Universe. The properties of many of these systems can only be explained if the stars interacted by exchanging mass during their prior evolution. With the advent of gravitational wave astronomy (LIGO and LISA in the 2030s), the study of the evolution of stars in binaries, especially ultracompact binaries, has taken on a new urgency. The primary objective of the proposed research is to make significant contributions to the creation of a unified picture for the formation, evolution, and final states of various types of compact binaries and related systems. This includes an improved understanding of the inter-relationships between Cataclysmic Variables (CVs), Contact Binaries, Algol-like Binaries, Low-Mass X-ray Binaries, Millisecond Pulsars, and Type Ia Supernovae. These objectives will be carried out by using sophisticated stellar evolution codes such as MESA to determine if, for instance, CVs could have evolved from much more massive progenitor stars. By analyzing the chemical abundances observed in these systems we believe that we will be able to answer this question. We will also look for more unusual evolutionary paths that might produce one or more degenerate stars (including EL CVn-type binaries). The determination of the progenitors of Type Ia SNe is particularly problematic since astronomers treat them as "standardizable candles" and thus rely on them to determine distances and other parameters on a cosmic scale. We will revisit the Type Ia SN progenitor problem by using two hydrodynamic codes to determine which types of companion stars are admissible. We will also look at the intrinsically related problem of under-energetic events (Type Iax) to determine how much ablation of the putative companions occurs. Another major objective of our work is to discover and analyze targets that are closely related to the ones described above (as well as exoplanets) as a follow-up to large-scale surveys that are either ongoing or are imminent. This includes the analysis of data products from Kepler, K2, and especially TESS, but also from SDSS, Pan-STARRS, LSST, and the JWST. The ancillary science associated with these discoveries is ground-breaking. Our group is well poised to take advantage of the multitude of new data that will be forthcoming.