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 $K_2=256\pm 2$ km s${}^{-1}$. We also obtain the rotational broadening of its photospheric lines $v_{\mathrm{r}\mathrm{o}\mathrm{t}}\sin i=141\pm 3$ km s${}^{-1}$. From these and the eclipse geometry, we derive a donor-to-white-dwarf mass ratio $q=M_2\mathrm{/}{M}_1=0.62\pm 0.02$, an orbital inclination $i={80.8}^{\circ }\pm {0.5}^{\circ }$ and dynamical masses $M_1=1.21\pm 0.04{\mathrm{M}}_{\odot }$ and $M_2=0.75\pm 0.04{\mathrm{M}}_{\odot }$ ($1\sigma$). 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.