Revisiting FS Aurigae and its triple cataclysmic variable system hypothesis

TL;DR

This study confirms a long-term periodicity in FS Aurigae, supporting the hypothesis that it is part of a triple system with a third body causing secular perturbations, and refines the third body's estimated properties.

Contribution

The paper provides new observational evidence and improved modeling of the third body in FS Aurigae, including eccentric and inclined orbits, and updates the third body's mass estimate.

Findings

Confirmed VLPP of approximately 857 days.

Estimated third body mass of about 29 Jupiter masses.

Supported the triple system hypothesis for FS Aurigae.

Abstract

A very long term variability (VLPP), with period of 875 days, was observed in the long-term light curve of FS Aurigae in 2011. This periodicity was calculated on 6 cycles. We re-examine the periodicity with new observations over of the past 5 yrs. A total of 18 yrs of observations confirm the hypothesis of a third body perturbing in a secular way the cataclysmic variable (CV). Improvements to the model such as eccentric and inclined orbits for the third body and a binary post-Newtonian correction are considered. We confirm the VLPP of FS Aur and find the new period of 857 $\pm$ 78 days. The secular perturbations are most efficient when the mass of the third body is M=29 MJ, much less than the 50 MJ reported in 2011. We estimate the effect of the third body on the mass transfer rate and the brightness of the system. We consider alternative scenarios for the VLPP. The new data and analysis supports the hypothesis that FS Aur is a CV in a triple system.