First results from GAPS


The first two results from GAPS – the Global Architecture of Planetary Systems project - are going to be published in Astronomy & Astrophysics. GAPS is a large observational programme with the newly built high-resolution spectrograph HARPS-N, recently come into operation on the Telescopio Nazionale Galileo (link). GAPS is a structured, largely synergetic observational programme specifically designed to maximise the scientific return in several aspects of exo-planetary astrophysics, taking advantage of the unique capabilities provided by the union of HARPSN and TNG. GAPS results from the efforts of a lot of researchers belonging to at least ten INAF institutes, among which the TNG, to the Milan and Padova Universities and to several other European institutes.

With GAPS we’ll try to answer to some fundamental questions regarding around which kind of stars do we have to search for planets? Is the majority of existing planets, giants or earth like planets? At the end: is our Solar System an exception or is the rule? These first two results agree with what is known so far that is, for example, that there is a strong dependence of planet frequency on stellar metallicity for giant planets with strong consequences on the theories about planetary systems formation models.

The first result is on a A&A paper which aim has been to fully characterise the orbital properties of the transiting system Qatar-1, and the physical properties of the star and the planet. To do this, the GAPS team, leaded by Elvira Covino (INAF – Napoli) exploited HARPS-N high-precision radial velocity measurements, obtained during a transit, to measure the Rossiter-McLaughlin effect in the Qatar-1 system, and exploited out-of-transit measurements to re-determine the spectroscopic orbit. They founded that the system is well aligned and so they could definitely ruled out any significant orbital eccentricity. The evolutionary status of the system has also been inferred, and the present orbital configuration and timescale for orbital decay have been discussed in terms of star-planet tidal interactions. They, finally, achieved a significant improvement in the accuracy of the orbital parameters and derived the spin-orbit alignment of the system; this information, combined with the spectroscopic determination of the host star properties, allowed them to derive the fundamental physical parameters for star and planet (masses and radii). The orbital solution for the Qatar-1 system is consistent with a circular orbit and the system. The planet is also found to be significantly more massive than previously reported and the host star is confirmed to be metal-rich and slowly rotating, though moderately active.

A second important result is on an A&A letter where it is described how the GAPS team, leaded by Silvano Desidera (INAF- Padova) have performed radial velocity monitoring of the metal-poor star HIP 11952 on 35 nights over about 150 days using HARPS-N at the TNG and HARPS at ESO 3.6m telescope. The radial velocities showed a scatter compatible with the measurement errors for such a moderately warm metal-poor star. This observations allowed then to exclude the presence of the two giant planets which were announced some months ago. This result is important considering that HIP 11952 was thought to be the most metal-poor star hosting a planetary system with giant planets, thus challenging some models of planet formation.