Tuesday, June 5, 2012

1206.0601 (A. Santerne et al.)

SOPHIE velocimetry of Kepler transit candidates VI. A false positive rate of 35% for Kepler close-in giant candidates    [PDF]

A. Santerne, R. F. Díaz, C. Moutou, F. Bouchy, G. Hébrard, J. -M. Almenara, A. S. Bonomo, M. Deleuil, N. C. Santos
The false positive probability (FPP) of Kepler transiting candidates is a key value for statistical studies of candidate properties. An investigation of the stellar population in the Kepler field by Morton & Johnson (2011) has provided an estimation for the FPP of less than 5% for most of the candidates. We report here the results of our radial velocity observations on a sample of 46 Kepler candidates with transit depth greater than 0.4%, orbital period less than 25 days and host star brighter than Kepler magnitude 14.7. We used the SOPHIE spectrograph mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to establish the nature of the transiting candidates. In this sample, we found 5 undiluted eclipsing binaries, 2 brown dwarfs, 6 diluted eclipsing binaries and 9 new transiting planets that complete the 11 already published. The remaining 13 candidates were not followed up or remain unsolved due to photon noise limitation or lack of observations. From these results we compute the FPP for Kepler close-in giant candidates to be 34.8% \pm 6.5%. We investigate the variation of FPP for giant candidates with the longer orbital periods and find that it should be up to 40% for orbital periods in-between 10 days and 200 days. We thus find a significant discrepancy with the estimation of Morton & Johnson (2011). We finally discuss the reasons of this discrepancy and the possible extension of this work towards smaller planet candidates.
View original: http://arxiv.org/abs/1206.0601

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