Nature of the Eclipsing Polar 1RXS J184542.4\(+\)483134

Abstract

We have carried out a comprehensive study of the poorly investigated eclipsing polar 1RXS J184542.4\(+\)483134 with a short orbital period \(P_{\textrm{orb}}\approx 79\) min. An analysis of its long-term light curves points to a change in the position and sizes of the accretion spot as the accretion rate changes. Narrow and broad components, which are probably formed on the ballistic segment of the accretion stream and on the magnetic trajectory, respectively, are identified in the emission line profiles. An inversion of the line profiles from emission to absorption due to the obscuration of the accretion spot by the accretion stream is observed. Based on the eclipse duration and the radial velocities of the narrow line component, we impose constraints on the white dwarf mass, \(0.49\leq M_{1}/\;M_{\odot}\leq 0.89\), and the orbital inclination, \(79.7^{\circ}\leq i\leq 84.3^{\circ}\). An analysis of the cyclotron spectra points to the presence of two accretion spots with magnetic field strengths \(B_{1}=28.4^{+0.1}_{-0.2}\) MG and \(B_{2}=30{-}36\) MG. The main spot has a complex structure that apparently has a dense core and a less dense periphery emitting a spectrum with cyclotron harmonics. Polarization observations reveal a circular polarization sign reversal during the orbital period and an anticorrelation of the polarization with the brightness of the polar. Our modeling of polarization observations using the simple model of an accreting white dwarf shows that the polarization properties can be interpreted in terms of two-pole accretion with different optical depths of the accretion spots (\(\tau_{1}/\tau_{2}\sim 10\)). An analysis of the Swift/XRT observations points to a predominance of bremsstrahlung in the X-ray radiation from the system.