X‐Ray Spectroscopic Observations of EX Hydrae and Mass Determination of the White Dwarf

Abstract

From X-ray line spectroscopy with ASCA, we have measured the temperature of the shock where the accretion flow meets the surface of the white dwarf in the intermediate polar EX Hya to be kT = 15.4+ 5.3−2.6 keV, and obtained the corresponding white dwarf mass to be 0.48+ 0.10−0.06 M☉. We have found that the abundances of silicon, sulfur, and argon are marginally consistent with solar values (1.3 ± 0.3), while that of iron is significantly smaller (0.6 ± 0.2). Our approach to mass determination is free from uncertainties in the inclination angle of the binary and thus is widely applicable to intermediate polars.