Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?

摘要: (abridged) In the frame of search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present results obtained on early F-type star Theta Cygni. Elodie Sophie at OHP were used to obtain spectra. Our dedicated radial-velocity measurement method was monitor star's radial velocities over five years. We also use complementary, high angular resolution high-contrast images taken with PUEO CFHT. show that Cygni are quasi-periodically variable, a ~150-day period. These variations not due ~0.35-Msun stellar companion detected in imaging more than 46 AU from star. The absence correlation between bisector velocity span this 7 km/s vsini star, as well other criteria indicate observed spots. amplitude seems rule out pulsations. However, observe peak periodogram same period one found periodogram, which indicates probable link these low lineshape origin. Long-period expected type our knowledge. If origin (hence new type) be confirmed long-period variations, would have several consequences both terms observational strategy data analysis. An alternative explanation variable is presence least planet few Jupiter masses orbiting less 1 AU.