A possible giant planet orbiting the cataclysmic variable LX Ser

TL;DR

This paper presents evidence for a giant planet orbiting the cataclysmic variable LX Ser, inferred from cyclic variations in eclipse timings likely caused by a third body, with implications for planetary formation in such systems.

Contribution

The study provides the first evidence suggesting a giant planet orbiting a cataclysmic variable, based on eclipse timing variations and stability analysis.

Findings

Cyclic oscillation in LX Ser's eclipse timings with a 22.8-year period.

The third body is likely a giant planet with a mass of about 7.5 Jupiter masses.

The planetary system is dynamically stable.

Abstract

LX Ser is a deeply eclipsing cataclysmic variable with an orbital period of $0.^d 1584325$. Sixty two new eclipse times were determined by our observations and the AAVSO International Data base. Combining all available eclipse times, we analyzed the O-C behavior of LX Ser. We found that the O-C diagram of LX Ser shows a sinusoidal oscillation with a period of 22.8 yr and an amplitude of 0.00035 days. Two mechanisms (i.e., the Applegate mechanism and the light travel time effect) are applied to explain the cyclic modulation. We found that the Applegate mechanism is difficult to explain the cyclic oscillation in the orbital period. Therefore, the cyclic period change is most likely to be caused by the light travel time effect due to the presence of a third body. The mass of the tertiary component was determined to be $M_3\sim7.5 M_{Jup}$. We supposed that the tertiary companion is plausible a giant planet. The stability of the giant planet was checked, and we found that the multiple system is stable.