Is There a Third Component in the Intermediate Polar V405 Aur?

TL;DR

This study analyzes the spin period variability of the white dwarf in V405 Aur, suggesting possible models including a third body, and highlights the need for continued monitoring to confirm the nature of the period changes.

Contribution

It presents new timing measurements and proposes the potential presence of a third body influencing the white dwarf's spin period in V405 Aur.

Findings

Significant negative trend in the spin period ephemeris.

Possible models include a cubic ephemeris or a periodic change with a 6.2-year cycle.

Evidence suggests a third body of at least 0.09 solar masses.

Abstract

Variability of the spin period of the white dwarf in the V405 Aur (RX J0558.0+5353) system using our observations and previously published maxima timings is analyzed. As the phase light curve contains two nearly equal photometric waves, one maximum was set as a "primary" one. The ephemeris for the maxima of the "spin variability" (due to rotation of the magnetized white dwarf) for recent seasons 2010-2012 is Tmax = HJD 2455882.470614(25)+0.00631314602(46)E. This corresponds to a significant negative trend at the "O-C" diagram. Due to significant gaps in the observational data and statistical error of timings, there may be some suggestions on the spin period variability - a fast period "jump" in 2007y; secular period variations; a cubic ephemeris (which may be interpreted by a precession of the magnetic white dwarf at a time-scale of decades) or a periodic change with a period of 6.2 years and semi-amplitude of 17.2\pm1.8 sec. For the present observations, more reliable are two latter models. To distinguish between them, a continuation of monitoring is needed. The periodic variations may be interpreted by a light time effect caused by a third body of mass (M3 > 0.09M\odot), which corresponds to a low-mass star, but not to an extra-solar planet. In this case, the system belongs to a rare class of cataclysmic variables with a third body.