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Description
In here we study the stellar content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the spectral types of 11466 stars. Nine planet host stars have already been identified in these fields. The determination of the spectral types of thousands of stars of which CoRoT obtained high-precision light-curves also opens up a large variety of other research projects. For our study, we used spectra obtained with the multi-object spectrograph AAOmega and derived the spectral types by using template spectra with well known parameters. We find that 34.8+/-0.7% of the stars observed by CoRoT in these fields are F-dwarfs, 15.1+/-0.5% G-dwarfs, and 5.0+/-0.3% K-dwarfs. We conclude that the apparent lack of exoplanets of K- and M-stars is explained by the relatively small number of these stars in the observed sample. We also show that the apparently large number of planets orbiting F-stars is also explained by the large number of such stars in these fields. Given the number of F-stars, we would have expected to find even more planet orbiting F-stars. Our study also shows that the difference between the sample of stars that CoRoT observes and a sample of randomly selected stars is relatively small, and that the yield of CoRoT is the detection one hot Jupiter amongst 2100+/-700 stars. We finally conclude that transit search programs can be used in order to study the relation between the frequency of planets and the mass of the host stars, and that the results obtained so far are in general agreement with those of radial velocity programs.
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