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arXiv · 1110.5840

Optimizing exoplanet transit searches around low-mass stars with inclination constraints

E. Herrero·I. Ribas·C. Jordi·E. F. Guinan·S. G. Engle
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Abstract

Aims. We investigate a method to increase the efficiency of a targeted exoplanet search with the transit technique by preselecting a subset of candidates from large catalogs of stars. Assuming spin-orbit alignment, this can be done by considering stars that have higher probability to be oriented nearly equator-on (inclination close to 90^{\circ}). Methods. We use activity-rotation velocity relations for low-mass stars with a convective envelope to study the dependence of the position in the activity-vsini diagram on the stellar axis inclination. We compose a catalog of G-, K-, M-type main sequence simulated stars using isochrones, an isotropic inclination distribution and empirical relations to obtain their rotation periods and activity indexes. Then the activity - vsini diagram is filled and statistics are applied to trace the areas containing the higher ratio of stars with inclinations above 80^{\circ}. A similar statistics is applied to stars from real catalogs with log(R'HK) and vsini data to find their probability of being equator-on. Results. We present the method used to generate the simulated star catalog and the subsequent statistics to find the highly inclined stars from real catalogs using the activity - vsini diagram. Several catalogs from the literature are analysed and a subsample of stars with the highest probability of being equator-on is presented. Conclusions. Assuming spin-orbit alignment, the efficiency of an exoplanet transit search in the resulting subsample of probably highly inclined stars is estimated to be two to three times higher than with a global search with no preselection.

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E. Herrero, I. Ribas, C. Jordi, E. F. Guinan, S. G. Engle. 2011-10-26. Optimizing exoplanet transit searches around low-mass stars with inclination constraints. https://doi.org/10.1051/0004-6361%2F201117809

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