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Post Info TOPIC: NY Virginis
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Title: The Pulsating sdB+M Eclipsing System NY Virginis and its Circumbinary Planets
Author: Jae Woo Lee, Tobias Cornelius Hinse, Jae-Hyuck Youn, Wonyong Han

We searched for circumbinary planets orbiting NY Vir in historical eclipse times including our long-term CCD data. Sixty-eight times of minimum light with accuracies better than 10 s were used for the ephemeris computations. The best fit to those timings indicated that the orbital period of NY Vir has varied due to a combination of two sinusoids with periods of P3=8.2 yr and P4=27.0 yr and semi-amplitudes of K3=6.9 s and K4=27.3 s, respectively. The periodic variations most likely arise from a pair of light-time effects due to the presence of third and fourth bodies that are gravitationally bound to the eclipsing pair. We have derived the orbital parameters and the minimum masses, M3sini3 = 2.8 MJup and M4sini4 = 4.5 MJup, of both objects. A dynamical analysis suggests that the outer companion is less likely to orbit the binary on a circular orbit. Instead we show that future timing data might push its eccentricity to moderate values for which the system exhibits long-term stability. The results demonstrate that NY Vir is probably a star-planet system, which consists of a very close binary star and two giant planets. The period ratio P3/P4 suggests that a long-term gravitational interaction between them would result in capture into a nearly 3:10 mean motion resonance. When the presence of the circumbinary planets is verified and understood more comprehensively, the formation and evolution of this planetary system should be advanced greatly.

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Blobrana


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Title: Circumbinary Planets Orbiting the Rapidly Pulsating Subdwarf B-type binary NY Vir
Authors: S.-B. Qian, L.-Y. Zhu, Z.-B. Dai, E. Fernández Lajús, F.-Y. Xiang, J.-J. He

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 x {10^{-12}}). The periodic variation was analysed 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(±0.3)\, Jupiter masses when a total mass of 0.60\, Solar masses 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 (~2.5 Jupiter masses) in the system.

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