L. A. Almeida, F. Jablonski, C. V. Rodrigues
We present an eclipse timing variations analysis of the post-common envelope binary NSVS 14256825, which is composed by a sdOB star and a dM star in a close orbit (P_{orb} = 0.110374 days). High-speed photometry of this system was performed between July, 2010 and August, 2012. Ten new mid-eclipse times of NSVS 14256825 were analyzed together with all available eclipse times in the literature. We revisited the O--C diagram using a linear ephemeris and detected a clear orbital period variation. We investigated this variation on the assumption that it is a light travel time (LTT) effect. A full orbital motion analysis indicates that two LTT shifts with semi-amplitudes of ~20 s and ~5 s are superimposed on the O--C diagram and are consistent with two circumbinary bodies. The best solution provides the orbital periods, P_c = 3.49 +/- 0.21 years and P_d = 6.86 +/- 0.25 years, and the projected semi-major axes, a_c \sin I_c = 1.9 +/- 0.3 AU and a_d \sin I_d = 2.9 +/- 0.6 AU, for the circumbinary bodies. The masses of the external bodies are M_c ~2.8 M_{Jupiter} and M_d ~8.1 M_{Jupiter}, if we assume their orbits are coplanar with the close binary. Therefore NSVS 14256825 is composed by the close binary and two circumbinary planets in a 2:1 mean motion resonance. The closer planet in NSVS 14256825 has the minimum binary-planet separation among all known circumbinary planets in post-common envelope systems.
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http://arxiv.org/abs/1210.3055
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