Dynamical mass of the white dwarf in XY Ari: a test for intermediate polar X-ray spectral models

We present a dynamical study of the eclipsing intermediate polar XY Ari based on time-resolved near-infrared spectroscopy obtained with the EMIR spectrograph on the 10.4-m Gran Telescopio Canarias. Using main sequence template spectra taken with the same instrument setup as the target spectra, we measure a radial velocity amplitude of the late K- type donor star K-2 = 256 +/- 2 km s(-1). We also obtain the rotational broadening of its photospheric lines v(rot) sin i = 141 +/- 3 km s(-1). From these and the eclipse geometry, we derive a donor-to-white dwarf mass ratio q = M-2 /M-1 = 0.62 +/- 0.02, an orbital inclination i = 80.8 degrees +/- 0.5 degrees and dynamical masses M-1 = 1.21 +/- 0.04 M-circle dot and M-2 = 0.75 +/- 0.04 M-circle dot (1 sigma). This result places the white dwarf in XY Ari as one of the three most massive known in a cataclysmic variable. Comparison with white dwarf mass estimates from X-ray spectral studies could indicate the necessity of an improvement of the X-ray models and/or analysis techniques, as a number of X-ray white dwarf masses are in disagreement with the dynamical mass value.