Circumbinary Planets Orbiting the Rapidly Pulsating Subdwarf B-type binary NY Vir

TL;DR

This paper reports the tentative discovery of a giant circumbinary planet orbiting the pulsating subdwarf B-type binary NY Vir, based on eclipse timing variations indicating a third body and potential additional planets.

Contribution

It presents the first evidence of a Jovian planet around a pulsating sdB binary using eclipse timing variations and suggests possible multiple planetary companions.

Findings

Detected a 7.9-year cyclic variation in eclipse timings.

Estimated a 2.3 Jupiter-mass planet at 3.3 AU from NY Vir.

Indicated potential for another Jovian planet due to long-term period changes.

Abstract

We report here the tentative discovery of a Jovian planet in orbit around the rapidly pulsating subdwarf B-type (sdB-type) eclipsing binary NY Vir. By using new determined eclipse times together with those collected from the literature, we detect that the observed-calculated (O-C) curve of NY Vir shows a small-amplitude cyclic variation with a period of 7.9\,years and a semiamplitude of 6.1\,s, while it undergoes a downward parabolic change (revealing a period decrease at a rate of $\dot{P}=-9.2\times{10^{-12}}$). The periodic variation was analyzed for the light-travel time effect via the presence of a third body. The mass of the tertiary companion was determined to be $M_3\sin{i^{\prime}}=2.3(\pm0.3)$\,$M_{Jupiter}$ when a total mass of 0.60\,$M_{\odot}$ for NY Vir is adopted. This suggests that it is most probably a giant circumbinary planet orbiting NY Vir at a distance of about 3.3 astronomical units (AU). Since the rate of period decrease can not be explained by true angular momentum loss caused by gravitational radiation or/and magnetic braking, the observed downward parabolic change in the O-C diagram may be only a part of a long-period (longer than 15 years) cyclic variation, which may reveal the presence of another Jovian planet ($\sim2.5$$M_{Jupiter}$) in the system.