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AR 16152 (Archival Research)

Thu Jul 25 13:43:47 GMT 2024

Principal Investigator: Edward Sion
PI Institution: Villanova University
Investigators (xml)

Title: Accreting White Dwarfs: Their Masses, Rotational Velocities and Chemical Abundances
Cycle: 28

Abstract
Accreting white dwarfs (WDs) in cataclysmic variables (CVs) provide crucial insights about the accretion of mass and angular momentum in all types of binaries including disk accreting NSs and BHs. Accreting WDs are the critical component in the single degenerate pathway to SN Ia and along with the double degenerate merger pathway, they are the standard candles of Cosmology proving that the universe is accelerating and the existence of dark energy. A key question is whether the WD in a CV grow in mass despite the mass loss due to 1000s of nova explosions in its life time. Angular momentum loss drives CV evolution and accreting WDs offer critically needed WD masses and reliable surface temperatures to derive the most accurate accretion rates. However, the number of accreting WDs with masses, accurate rotational velocities and chemical abundances of elements is severely limited, and the only spectral region in which the WD chemical abundances can be determined is the UV because the disk dominates the optical. We propose to fill in poorly sampled regions of the parameter space (accretion rate/Teff vs orbital period) by analyzing a subset of HST archival data for 50 CVs to address the individual masses of accreting WDs in CVs. We will use the newly available Gaia DR2 distances to obtain the WD radii, and use the WD mass-radius law to derive the masses. We will derive the chemical abundances of accreted metals, evidence of metal overabundances and WD rotational velocities. The proposed archival analysis will be a significant leap ahead compared to all earlier analysis of the data and will significantly impact the picture of the evolution of all compact binaries.