Seminars at FGG

"Searching for extrasolar planets around cool stars with GIANO"

Speaker: S.Benatti/I. Carleo (INAF-Oss. di Padova)

Date and time: 2015-03-09 11:30

Among the cool stars, M-dwarfs are becoming increasingly popular among the current programs aimed at searches for extrasolar planets. They are by far the most numerous class of stars in the Galaxy so that any reliable estimate of the global frequency of planets can not be derived excluding them. Even more crucially, the habitable zone is located close to the star for low-mass stars thanks to their low luminosity. Planet-search radial velocity surveys at optical range cannot be performed for the the late M, the most numerous class of M-dwarfs, because they are too faint at that wavelengths. The late-M are instead bright in the near infrared (NIR), the working range of GIANO, the new IR spectrograph available at the TNG, able to provide accurate radial velocity measurements. Actually no other IR instruments have the GIANO's capability to cover the entire NIR wavelength range. Furthermore the impact of stellar activity that often is quite strong for M-dwarfs is greatly reduced in the NIR with respect to the optical. We have developed an ensemble of IDL procedures to measure high precision radial velocities on GIANO spectra acquired during the Science Verification run, using the telluric lines as wavelength reference. The method is applied to various targets with different spectral type, from a K0V to an M8 star. Mainly depending on H magnitude we reached different dispersions: for a H magnitude of about 5 we obtain an rms scatter of ~10 m/s, while for a H magnitude of about 9 the standard deviation goes up to ~100 m/s.

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