Transiting exoplanets from the CoRoT space mission

Moutou

Tsantaki

et al. 2016

A&A

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268

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While giant extrasolar planets have been studied for more than two decades now, there are still some open questions as to their dominant formation and migration processes, as well as to their atmospheric evolution in different stellar environments. In this paper, we study a sample of giant transiting exoplanets detected by the Kepler telescope with orbital periods up to 400 days. We first defined a sample of 129 giant-planet candidates that we followed up with the SOPHIE spectrograph (OHP, France) in a 6-year radial velocity campaign. This allowed us to unveil the nature of these candidates and to measure a false-positive rate of 54.6 ± 6.5% for giant-planet candidates orbiting within 400 days of period. Based on a sample of confirmed or likely planets, we then derived the occurrence rates of giant planets in different ranges of orbital periods. The overall occurrence rate of giant planets within 400 days is 4.6 ± 0.6%. We recovered, for the first time in the Kepler data, the different populations of giant planets reported by radial velocity surveys. Comparing these rates with other yields, we find that the occurrence rate of giant planets is lower only for hot Jupiters but not for the longer-period planets. We also derive a first measurement of the occurrence rate of brown dwarfs in the brown-dwarf desert with a value of 0.29 ± 0.17%. Finally, we discuss the physical properties of the giant planets in our sample. We confirm that giant planets receiving moderate irradiation are not inflated, but we find that they are on average smaller than predicted by formation and evolution models. In this regime of low-irradiated giant planets, we find a possible correlation between their bulk density and the iron abundance of the host star, which needs more detections to be confirmed.

Section: Comparison With Other False-positive Rate Estimatesmentioning

confidence: 92%

SOPHIE velocimetry ofKeplertransit candidates

Moutou

Tsantaki

et al. 2016

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268

263

“…We only used the spectral orders 12 to 38 in the cross-correlation to reduce the dispersion of the measurements produced by noisy spectral orders. Moonlight contamination was tenuous in the spectra and required a correction only for two over the eight spectra, following the method described in Hébrard et al (2008) and Bonomo et al (2010). It introduced modest corrections (7 and 20 m s −1 for both spectra).…”

Section: Centroid Analysismentioning

confidence: 99%

SOPHIE velocimetry ofKeplertransit candidates

Bonomo

Hébrard

et al. 2012

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We report the discovery of two new transiting hot Jupiters, KOI-135b and KOI-204b, which were previously identified as planetary candidates by the Kepler team, and independently confirm the planetary nature of Kepler-17b, recently announced by Désert et al. (2011, ApJS, 197, 14). Radial-velocity measurements, taken with the SOPHIE spectrograph at the Observatoire de Haute-Provence (France), and Kepler photometry (Q1 and Q2 data) were used to derive the orbital, stellar, and planetary parameters. KOI-135b and KOI-204b orbit their parent stars in ∼3.02 and 3.25 days, respectively. They have approximately the same radius, R p = 1.20 ± 0.06 R Jup and 1.24 ± 0.07 R Jup , but different masses M p = 3.23 ± 0.19 M Jup and 1.02 ± 0.07 M Jup . As a consequence, their bulk densities differ by a factor of four, ρ p = 2.33 ± 0.36 g cm −3 (KOI-135b) and 0.65 ± 0.12 g cm −3 (KOI-204b), meaning that their interior structures are different. All three planets orbit metal-rich stars with [Fe/H] ∼ 0.3 dex. Our SOPHIE spectra of Kepler-17 were used both to measure the radial-velocity variations and to determine the stellar atmospheric parameters, allowing us to refine the characterisation of the planetary system. In particular we found the radial-velocity semi-amplitude and the stellar mass to be respectively slightly smaller and larger than in Désert et al. These two quantities, however, compensate and lead to a fully consistent planetary mass. Our analysis gives M p = 2.47 ± 0.10 M Jup and R p = 1.33 ± 0.04 R Jup . We found evidence of a younger age for this planetary system, t < 1.8 Gyr, which is supported by both evolutionary tracks and gyrochronology. Finally, we confirm the detection of the optical secondary eclipse by Désert et al. and also find the brightness phase variation with the Q1 and Q2 Kepler data. The latter indicates a low redistribution of stellar heat to the night side (<16% at 1-σ), if the optical planetary occultation comes entirely from thermal flux. The geometric albedo is A g < 0.12 (1-σ).

“…Three of the spectra were significantly affected by the Moon's scattered light. Their corresponding radial velocities were corrected using the same technique as in Santerne et al (2011) and Bonomo et al (2010). Another two spectra were slightly affected by the Moon scattered light and were not corrected because the Moon light affected the measurement at the level of a few m s −1 , which is compatible with the noise added by the correction.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

SOPHIE velocimetry ofKeplertransit candidates

Bonomo

Hébrard

et al. 2011

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We report the discovery of a new hot-Jupiter, , transiting a solar-type star with an orbital period of 1.855558 days ± 0.6 s thanks to public photometric data from the Kepler space mission and new radial velocity observations obtained by the SOPHIE spectrograph mounted on the 1.93-m telescope at the Observatoire de Haute-Provence, France. The planet , with a radius of 0.89 ± 0.05 R Jup and a mass of 0.55 ± 0.09 M Jup , orbits a G6V star with R = 1.02 ± 0.03 R , M = 1.12 ± 0.07 M , [Fe/H] = 0.29 ± 0.16 dex, T eff = 5620 ± 140 K, and an age of 650 +2500 −300 Myr. KOI-196b is one of the rare close-in hot Jupiters with a radius smaller than Jupiter suggesting that it is a non-inflated planet. The high precision of the Kepler photometry permits us to detect the secondary transit with a depth of 64 +10 −12 ppm as well as the optical phase variation. We find a geometric albedo of A g = 0.30 ± 0.08, which is higher than most of the transiting hot Jupiters with a measured A g . Assuming no heat recirculation, we find a day-side temperature of T day = 1730 ± 400 K. The planet KOI-196b seems to be one of the rare hot Jupiters located in the short-period hot-Jupiter desert.