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Issue A&A
Volume 506, Number 1, October IV 2009
The CoRoT space mission: early results
Page(s) 369 - 375
Section Planets and planetary systems
DOI http://dx.doi.org/10.1051/0004-6361/200912030
Published online 04 June 2009

A&A 506, 369-375 (2009)
DOI: 10.1051/0004-6361/200912030

An analysis of the transit times of CoRoT-1b

J. L. Bean

Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
    e-mail: bean@astro.physik.uni-goettingen.de

Received 10 March 2009 / Accepted 24 April 2009

Abstract
The CoRoT satellite is expected to discover tens of new transiting exoplanets during its mission. For each of these planets there will be a resulting long, continuous sequence of transit times that can be used to search for perturbations arising from an additional planet in the system. I report the results from a study of the transit times for CoRoT-1b, which was one of the first planets discovered by CoRoT. Analysis of the pipeline-reduced CoRoT light curve yields a new determination of the physical and orbital parameters of planet and star, along with 35 individual transit times at a typical precision of 36 s. I estimate a planet-to-star radius ratio of $R_{\rm p}/R_{\star} = 0.1433$ $\pm$ 0.0010, a ratio of the planet's orbital semimajor axis to the host star radius of $a/R_{\star} = 4.751$ $\pm$ 0.045, and an orbital inclination for the planet of $i=83.88\degr$ $\pm$ $0.29\degr$. The observed transit times are consistent with CoRoT-1b having a constant period and there is no evidence of an additional planet in the system. I use the observed constancy of the transit times to set limits on the mass of a hypothetical additional planet in a nearby, stable orbit. I ascertain that the most stringent limits (4  $M_{\oplus}$ at 3$\sigma$ confidence) can be placed on planets residing in a 1:2 mean motion resonance with the transiting planet. In contrast, the data yield less stringent limits on planets near a 1:3 mean motion resonance (5  $M_{\rm Jup}$ at 3$\sigma$ confidence) than in the surrounding parameter space. In addition, I use a simulation to investigate what sensitivity to additional planets could be obtained from the analysis of data measured for a similar system during a CoRoT long run (100 sequential transit times). I find that for such a scenario, planets with masses greater than twice that of Mars (0.2  $M_{\oplus}$) in a 1:2 mean motion resonance would cause high-significance transit time deviations. Therefore, such planets could be detected or ruled out using CoRoT long run data. I conclude that CoRoT data will indeed be very useful for searching for planets with the transit timing method.


Key words: techniques: photometric -- eclipses -- stars: individual: CoRoT-1 -- planetary systems



© ESO 2009

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