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 $M_{1}=1.03^{+0.16}_{-0.11} , mathrm{M}_{odot}$ and $M_2 = 0.39^{+0.07}_{-0.06} , mathrm{M}_{odot}$ 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 Alfven radius in quiescence and during dwarf nova outburst.
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