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 \(v_\mathrm{rot} \sin i = 141 \pm 3\) km s\(^{-1}\). From these and the eclipse geometry, we derive a donor-to-white-dwarf mass ratio \(q = M_2/M_1 = 0.62 \pm 0.02\), 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.