HD189733 spectral variability

Observations have provided evidence for in-transit hydrogen H{alpha} absorption as well as variable pre-transit absorption signals. These have been interpreted in terms of a bow shock or an accretion stream that transits the host star before the planet.

We test the hypothesis of planetary related H{alpha} absorption by studying the time variability of the H{alpha} and stellar activity-sensitive calcium lines in high-resolution spectra of the planet host HD189733. In the framework of an observing campaign spanning several months, the host star was observed several times per week randomly sampling the orbital phases of the planet. We determine the equivalent width in the H{alpha}, Ca H&K and Ca IRT lines, and subtract stellar rotationally induced activity from the H{alpha} time series via its correlation with the IRT evolution.