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Seminars at FGG

Radial velocities from NIR spectroscopy

Speaker: Ilaria Carleo (INAF-Osservatorio di Padova)

Date and time: 2018-01-12 11:30

The near infrared (NIR) spectroscopy is becoming very important in the search for extrasolar planets. From the radial velocity (RV) data it is possible to 'see' the planetary signal, but it could be mistaken with the signal due to the stellar surface activity, especially when observing young active stars. So discriminating the origin of the signal becomes crucial: the planetary signal doesn't depend on the wavelength band, while the RV jitter due to the stellar activity is about one third lower in the NIR band respect to the visible one. For these reasons, observing active stars both in the visible and in the NIR ranges is a direct method to understand the cause of the radial velocity variations. That underlines the importance of the birth of instruments like GIARPS, aimed to have simultaneous spectra from GIANO (NIR) and HARPS-N (VIS). Here we present some results from RV analysis of a young star with NIR spectra, acquired during the commissioning run of GIANO-B at Telescopio Nazionale Galileo (La Palma, Spain), and IGRINS at the McDonald Observatory (Texas, USA). For the measurement of the RVs we use the telluric lines as wavelength reference and the Cross Correlation Function (CCF) to determine the velocity for both the star and the telluric lines. This method allows to reach a precision in RVs of about 10 m/s in the best cases (for a star with an H magnitude of about 5). We estimate a better precision (around 3 m/s) in the NIR RVs with the insertion of an absorbing cell, similar to that used for CRIRES.

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