Measuring the masses of intermediate polars with NuSTAR
Abstract
The X-ray spectra of intermediate polars can be modelled to give a direct measurement of whitedwarf mass. However, as the characteristic temperature of the standing shock located above the surface of the white dwarf is typically >10 keV, we require telescopes capable of detecting hard X-rays. I will first discuss the fitting of accretion models to NuSTAR spectra of three intermediate polars; V709 Cas, NY Lup and V1223 Sgr in order to determine their masses. From fits to their 3-78 keV spectra, we find masses of 0.88^{+0.05}_{-0.04}, 1.16^{+0.04}_{-0.02} and 0.75±0.02 M_{⊙} for V709 Cas, NY Lup and V1223 Sgr, respectively. Our measurements are generally in agreement with those determined by previous surveys of intermediate polars, but with typically a factor ∼2 smaller uncertainties. This work has paved the way for an approved NuSTAR Legacy Survey of white dwarf masses in magnetic CVs, utilizing ∼1Ms of time to observe 25 magnetic CVs. The survey aims to constrain the mass distribution of magnetic white dwarfs in our Galaxy, which has important implications for binary evolution models and the production of type Ia supernovae. Finally, I will present the first results from the survey, which began observations in November 2017.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E3075S