AAVSO: American Association of Variable Star Observers

Measuring the Masses of White Dwarfs with X-rays: A NuSTAR Legacy Survey (Abstract)

Volume 49 number 1 (2021)

Aarran Shaw
University of Alberta, Canada; aarrans@unr.edu

Abstract

(Abstract only) Magnetic cataclysmic variables are binary systems consisting of a white dwarf accreting matter from a normal, Sun-like star. The magnetic field of the white dwarf is strong enough to disrupt the accretion flow, forcing material along the magnetic field lines on to the poles of the dense star, where it forms an extremely hot shock just above its surface. The temperature of this shock is directly related to the white dwarf mass, and can be measured by studying the hard X-ray spectrum. This method is complimentary to optical radial velocity measurements, which depend on the (often not very well-known) binary inclination. With the 2012 launch of NASA’s NuSTAR X-ray telescope, the hard X-ray spectrum has become much more accessible to astronomers. We present here the results from a NuSTAR Legacy survey of 19 magnetic cataclysmic variables, measuring their spectra and deriving the masses of their white dwarfs. We present the mass distribution and draw comparison with the masses of other classes of white dwarfs, commenting on the consequences our results may have on theories of accretion and novae in CVs.