A Study on White Dwarf Masses in Cataclysmic Variables Based on XMM-Newton and Suzaku Observations

The distribution of the mass of white dwarfs (WDs) is one of the fundamental questions in the field of cataclysmic variables (CVs). In this work, we make a systematical investigation on the WD masses in two subclass of CVs: intermediate polars (IPs) and non-magnetic CVs in the solar vicinity based on the flux ratios of Fe XXVI-Lyα to Fe XXV-Heα emission lines (I _7.0/I _6.7) from archival XMM-Newton and Suzaku observations. We first verify the (semi-empirical) relations between I _7.0/I _6.7, the maximum emission temperature (T _max) and the WD mass (M _WD) with the mkcflow model based on the apec description and the latest AtomDB. We then introduce a new spectral model to measure M _WD directly based on the above relations. A comparison shows that the derived M _WD is consistent with dynamically measured ones. Finally, we obtain the average WD masses of 58 CVs (including 36 IPs and 22 non-magnetic CVs), which is the largest X-ray selected sample. The average WD masses are <M _WD,IP> = 0.81 ± 0.21 M _⊙ and $\langle {M}_{\mathrm{WD},\mathrm{DN}}\rangle =0.81\pm 0.21\,{M}_{\odot }$ for IPs and non-magnetic CVs, respectively. These results are consistent with previous works.