The intermediate polar cataclysmic variable GK Persei 120 years after the nova explosion: a first dynamical mass study

Abstract

We present a complete dynamical study of the intermediate polar and dwarf nova cataclysmic variable GK Per (Nova Persei 1901) based on a multi-site optical spectroscopy and $R$-band photometry campaign. The radial velocity curve of the evolved donor star has a semi-amplitude $K_2=126.4\pm 0.9\mathrm{km}{\mathrm{s}}^{-1}$ and an orbital period $P=1.996872\pm 0.000009\mathrm{d}$. We refine the projected rotational velocity of the donor star to $v_{\mathrm{rot}}\sin i=52\pm 2\mathrm{km}{\mathrm{s}}^{-1}$ which, together with $K_2$, provides a donor star to white dwarf mass ratio $q=M_2/M_1=0.38\pm 0.03$. We also determine the orbital inclination of the system by modelling the phase-folded ellipsoidal light curve and obtain $i=67^{\circ }\pm 5^{\circ }$. The resulting dynamical masses are $M_1=1.03_{-0.11}^{+0.16}{\mathrm{M}}_{\odot }$ and $M_2=0.39_{-0.06}^{+0.07}{\mathrm{M}}_{\odot }$ at $68$ per cent confidence level. The white dwarf dynamical mass is compared with estimates obtained by modelling the decline light curve of the $1901$ nova event and X-ray spectroscopy. The best matching mass estimates come from the nova light curve models and an X-ray data analysis that uses the ratio between the Alfvén radius in quiescence and during dwarf nova outburst.

15 pages, 6 figures, 8 tables, accepted for publication in MNRAS