Possible detection of phase changes from the non-transiting planet HD 46375b by CoRoT

摘要

Context. The present work deals with the detection of phasechanges in an exoplanetary system. HD46375 is a solar analogknown to host a non-transiting Saturn-mass exoplanet with a 3.0236 dayperiod. It was observed by the CoRoT satellite for 34 days during thefall of 2008. Aims. We attempt to identify at optical wavelengths, thechanging phases of the planet as it orbits its star. We then try toimprove the star model by means of a seismic analysis of the same lightcurve and the use of ground-based spectropolarimetric observations. Methods. The data analysis relies on the Fourier spectrum and the folding of the time series. Results. We find evidence of a sinusoidal signal compatible interms of both amplitude and phase with light reflected by the planet.Its relative amplitude is ppm, implying an albedo A=[0.16, 0.33] or a dayside visible brightness temperature K by assuming a radius and an inclination .Its orbital phase differs from that of the radial-velocity signal by at most .However, the tiny planetary signal is strongly blended by anothersignal, which we attribute to a telluric signal with a 1 day period. Weshow that this signal is suppressed, but not eliminated, when using thetime series for HD46179 from the same CoRoT run as a reference. Conclusions. This detection of reflected light from anon-transiting planet should be confirmable with a longer CoRoTobservation of the same field. In any case, it demonstrates thatnon-transiting planets can be characterized using ultra-precisephotometric lightcurves with present-day observations by CoRoT andKepler. The combined detection of solar-type oscillations on the sametargets (Gaulme etal. 2010a) highlights the overlap betweenexoplanetary science and asteroseismology and shows the high potentialof a mission such as Plato. Key words: planetary systems - techniques: photometric - methods: data analysis - stars: individual: HD 46375