0 Assigned ID: 767 ----- Attempting Submission 1 (Fri Mar 06 20:57:02 GMT 2020) ----- 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. PI-Sion has leading expertise in the structure and evolution of accreting white dwarfs in interacting binaries as well as the physical processes and evolution of single white dwarfs. He has been PI on numerous successful HST proposals beginning in Cycle 2 throught Cycle 25 and is the lead author or co-author on 84 HST refereed publications in major journals. He has extensive experience in the modeling of UV spectra of cataclysmic variables with accretion disks and white dwarf phtotospheres, starting with the launch of HST. He also has extensive experience with quasi-static evolutionary simulations of accreting white dwarfs. Co-I Godon has a long expertise in the modeling of accretion disks in cataclysmic variables and in the last years he has extended his ultraviolet spectroscopic analysis of disks and white dwarfs into the optical band. He has a long expertise in the use and application of the suite of code TLUSTY to generate stellar spectra and accretion disk spectra. Over the years he has provided many attempts to confront CV spectra with disk models and by doing so he has advanced this important topic. He is the author or co-author on 44 HST publications and has expertise with HST STIS and COS spectra and their analysis. He has also expertise on accretion disk boundary layers. Stellar Physics and Stellar Types 0 Regular false false true false false SUPPORTED