Optical and X-ray Variability of the Peculiar Cataclysmic Variable FS Aur with a Magnetic and Freely Precessing White Dwarf

TL;DR

This study reports the first photometric detection of the white dwarf's precession period in FS Aur, combining optical and X-ray data to explore its variability and potential causes like third-body influences.

Contribution

It provides the first photometric evidence of the white dwarf's precession period in FS Aur and links long-term variability to possible third-body effects.

Findings

Precession period detected in photometric data, especially in (B-I) color index.

X-ray data reveal both orbital and precession periods in the light curve.

Long-term variability may be caused by eccentricity modulation due to a third body.

Abstract

We present preliminary results of long-term monitoring of the peculiar cataclysmic variable FS Aurigae conducted during the 2010-2011 observational season. The multicolor observations revealed, for the first time in photometric data, the precession period of the white dwarf, previously seen only spectroscopically. This is best seen in the (B-I) color index and reflects the spectral energy distribution variability. Analysis of X-ray observations made with Chandra and Swift, also revealed the existence of both the orbital and precession periods in the light curve. We also show that the long-term variability of FS Aur and the character of its outburst activity may be caused by variations in the mass transfer rate from the secondary star as the result of eccentricity modulation of a close binary orbit induced by the presence of a third body on a circumbinary orbit.