White dwarf masses in intermediate polars
Abstract
We present results of white dwarf (WD) mass measurements in a sampleof intermediate polars (IPs) observed by Suzaku and NuSTAR. A noveltwo-parameter grid of accretion-column spectra accounting for thefinite magnetosphere size was used for this aim. The grid parametersare the WD mass, ranging between 0.3 - 1.4 solar masses, and thenormalized magnetospheric radius R_{rm m}/R_{rm WD} ranging between 1.5 -1000. The fit to the hard X-ray spectrum of some IPs gives a strip onthe WD mass - R_{rm m} plane, and a lower limit of the WD mass could befound assuming that the magnetospheric radius equals the radius ofcorotation. Assuming additionally that the break frequency in thepower spectra of IPs corresponds to the Keplerian frequency at themagnetosphere allows then to estimate the WD mass and themagnetospheric radius simultaneously. This new method was tested usingEX Hya, and allowed to obtain the WD mass in GK Per. We also showedthat the magnetospheric radius in that IP increased from 2.8pm0.2 tosim4.3 R_{rm WD} when its luminosity decreased from the maximum to quiescenceduring the outburst. This method was used for all available IPsobserved by Suzaku and NuSTAR. Obtained WD masses are compared withmasses published by other authors including those obtained withoptical methods.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E3288S