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OATS-UNI/TS SEMINAR
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Speaker: Paolo Molaro (OATs)

Title: Detection of the Rossiter-McLaughlin effect in the 2012 June 6 Venus transit
Date: Wednesday, January 9th, 2013
Time: 11:30
Venue: Villa Bazzoni
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Abstract: Eclipsing bodies on stars produce radial velocity variations on the photospheric stellar lines known as the Rossiter-McLaughlin (RM) effect. The body occults a small area of the stellar disk and, due to the rotation of the star, the stellar line profiles are distorted according to the projected location of the body onto the stellar disk. The effect originally observed in eclipsing binaries was also shown to be produced by extrasolar planets transits by Queloz et al (2000). Here we report the detection of the RM effect in the Sun due to the Venus Transit of 6th June 2012. We used the integrated sunlight as reflected by the Moon at night-time to record part of the transit by means of the high precision HARPS spectrograph at the 3.6m La Silla ESO telescope. The observations show that the partial Venus eclipse of the solar disk in correspondence of the passage in front of the receding hemisphere produced a modulation in the radial velocity with a negative amplitude of ~ -1 m/s in agreement with the theoretical model within few cm/s. The radial velocity change is comparable to the solar jitter and more than a factor 2 smaller than previously detected in extra-solar Hot-Neptunes. This detection anticipates the study of transits of Earth-size bodies in solar type stars by means of a high resolution spectrograph attached to a 40m class telescope.
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Contact: Valentina D'Odorico (OATs)