Abstract
We recently reported the photometric and spectroscopic detection of the primary transit of the 111-day-period, eccentric extra-solar planet HD80606 b, at Observatoire de Haute-Provence, France (Moutou et al. 2009). The whole egress of the primary transit and a section of its central part were observed, allowing the measurement of the planetary radius, and evidence for a spin-orbit misalignment through the observation of the Rossiter-McLaughlin anomaly. The ingress having not been observed for this long-duration transit, uncertainties remained in the parameters of the system. We present here a refined, combined analysis of our photometric and spectroscopic data, together with further published radial velocities, ground-based photometry, and Spitzer photometry around the secondary eclipse, as well as new photometric measurements of HD 80606 acquired at Mount Hopkins, Arizona, just before the beginning of the primary transit. Although the transit is not detected in those new data, they provide an upper limit for the transit duration, which narrows down the possible behaviour of the Rossiter-McLaughlin anomaly in the unobserved part of the transit. We analyse the whole data with a Bayesian approach using a Markov-chain Monte Carlo integration on all available information. We find R_p = 0.98 +- 0.03 R_Jup for the planetary radius, and a total primary transit duration of 11.9 +- 1.3 hours from first to fourth contact. Our analysis reinforces the hypothesis of spin-orbit misalignment in this system (alignment excluded at >95 % level), with a positive projected angle between the planetary orbital axis and the stellar rotation (median solution lambda ~ 50 degrees). As HD80606 is a component of a binary system, the peculiar orbit of its planet could result from a Kozai mechanism.
Highlights
HD 80606 is a solar-type star with a gas giant planetary companion on a highly eccentric 111-day orbit (Naef et al 2001)
By a lucky coincidence, the orbital plane is aligned with the line-of-sight, so that both the secondary eclipse and
Based on observations made with the 1.20-m and 1.93-m telescopes at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE consortium, and with a 16-inch telescope at Mt
Summary
HD 80606 is a solar-type star with a gas giant planetary companion on a highly eccentric 111-day orbit (Naef et al 2001). Based on observations made with the 1.20-m and 1.93-m telescopes at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE consortium (program 07A.PNP.CONS), and with a 16-inch telescope at Mt. Hopkins, Arizona, USA, by the MEarth team. The secondary eclipse was measured during a long photometric run with the Spitzer space telescope (Laughlin et al 2009). In Moutou et al (2009, hereafter M09), we presented our detection of the primary transit, simultaneously measured in photometry and spectroscopy with the 1.2-m and 1.93-m telescopes at Observatoire de Haute-Provence, France. The spectroscopic transit data seemed to indicate that the orbital plane of the planet was not aligned with the stellar rotation axis. Since the transit ingress was not observed, a large degree of uncertainty remained in this parameter, as well as in the latitude of the transit and radius of the host star
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