Planets or Spots: tests and diagnostics in single and multi-planet systems

¹ Observatoire Astronomique de l'Université de Genève, 1290-Sauverny, Switzerland
² Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
³ Centro de Astronomia e Astrofísica da Universidade de Lisboa, OAL, Tapada da Ajuda, 1349-018 Lisboa, Portugal
⁴ Laboratorio de Astrofísica Espacial y Física Fundamental (LAEFF-INTA), Apdo. 78, 28691 Villanueva de la Cañada, Spain
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

Abstract

Extrasolar planet searches blossomed and prospered under the auspices of the radial velocity method. However, efficient as it is, it can misinterpret a periodic signal created by stellar phenomena as being originated from a planet. The most common of these is the presence of a cold spot, frequent in active stars. Here we review the representative cases of HD 166435, GJ 674 and TW Hya and the different methods used to pinpoint the spots' presence. We finish by underlining the importance of infrared measurements, as done in the TW Hya campaign, as a way of reducing the effect of spots on radial velocity measurements to a negligible level.