SOPHIE velocimetry ofKeplertransit candidates XI. Kepler-412 system: probing the properties of a new inflated hot Jupiter

Abstract

Context. Hot Jupiters are still a fascinating exoplanet population that presents a diversity we are still far from understanding. Highprecision photometric observations combined with radial velocity measurements give us a unique opportunity to constrain their properties better, on both their internal structure and their atmospheric bulk properties. Aims. We initiated a follow-up program of Kepler-released planet candidates with the goal of confirming the planetary nature of a number of them through radial velocity measurements. For those that successfully passed the radial velocity screening, we furthermore performed a detailed exploration of their properties to characterize the systems. As a byproduct, these systematic observations allow us to consolidate the exoplanets' occurrence rate. Methods. We performed a complete analysis of the Kepler-412 system, listed as planet candidate KOI-202 in the Kepler catalog, by combining the Kepler observations from Q1 to Q15, to ground-based spectroscopic observations that allowed us to derive radial velocity measurements, together with the host-star parameters and properties. We also analyzed the light curve to derive the star's rotation period and the phase function of the planet, including the secondary eclipse. Results. We secured the planetary nature of Kepler-412b. We found the planet has a mass of 0.939 ± 0.085 M Jup and a radius of 1.325 ± 0.043 R Jup , which makes it a member of the bloated giant subgroup. It orbits its G3 V host star in 1.72 days. The system has an isochronal age of 5.1 Gyr, consistent with its moderate stellar activity as observed in the Kepler light curve and the rotation of the star of 17.2 ± 1.6 days. From the detected secondary we derived the day-side temperature as a function of the geometric albedo. We estimated that the geometrical albedo A g should be between 0.094 ± 0.015 and 0.013 +0.017 −0.013 and the brightness of the day side 2380 ± 40 K. The measured night-side flux corresponds to a night-side brightness temperature of 2154 ± 83 K, much greater than what is expected for a planet with homogeneous heat redistribution. From the comparison to star and planet evolution models, we found that dissipation should operate in the deep interior of the planet. This modeling also shows that despite its inflated radius, the planet presents a noticeable amount of heavy elements, which accounts for a mass fraction of 0.11 ± 0.04.

Robust Transiting Exoplanet Radii in the Presence of Starspots from Ingress and Egress Durations

“…We place priors on M and R as described in Section 5.1.4. The results are shown in Figure 14; we find p 0 = R p /R = 0.0926 +0.0095 −0.0089 corresponding to R p = 1.16 ± 0.11R J -consistent with the literature value (R p /R = 0.1058 ± 0.0023, Deleuil et al 2014). We measure p 0 ≈ p 1 .…”

Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS

“…Firstly, we proceeded as described in Deleuil et al (2012Deleuil et al ( , 2014. The single 1D spectrum was carefully normalised.…”

Characterization of the four new transiting planets KOI-188b, KOI-195b, KOI-192b, and KOI-830b

“…Finally, we investigated the bulk composition of the four planets using CEPAM (e.g., Guillot 2010). Planetary evolution models have been built following the method used in, e.g., Deleuil et al (2014). The planets are assumed to be made of a central rocky core surrounded by a solar-composition envelope, but because they are irradiated giant planets, we also considered the cases where we dissipate a fraction (1%) of the incoming stellar flux deep in the layers of the planet (for more details see, e.g., Guillot & Havel 2011;Almenara et al 2013).…”

“…Since 2010 we have been conducting radial-velocity followup of KOIs with the SOPHIE spectrograph at the Observatoire (Santerne et al 2011a(Santerne et al , 2011bBonomo et al 2012;Deleuil et al 2014), as well as more massive companions and false positives Bouchy et al 2011;Santerne et al 2012;Díaz et al 2013;Moutou et al 2013).…”