Arcetri Astrophysical Observatory

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GIANO opens a new window on stellar and planetary astrophysics

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The near-infrared spectral region is crucial in order to observed stars that are relatively cold, such as stars similar to or smaller than the Sun or stars in the more evolved stage of red supergiant. Observing in the near-infrared allows to study such stars also in the inner regions of our Galaxy which are highly obscured by interstellar dust and are thus hard to see in the visible light. Their chemical composition and their motion within the Galaxy give us insight into the processes of star formation also in the inner regions of our Galaxy. Analysing these properties can also reveal the presence of any planet orbiting around these stars. Spectroscopic observations with high spectral resolution in the near-infrared are necessary in order to measure and interpret these properties.

These are some of the key objectives that prompted the design and construction of GIANO, a high dispersion spectrograph sensitive to a large range of near-infrared frequencies. GIANO is a unique and complex instrument, thermally isolated from the sorrounding environment and cooled to cryogenic temperatures close to -200 degrees. The instrument is mounted at the Telescopio Nazionale Galileo in La Palma and saw its first light in July 2012. The project, entirely founded by INAF, has been carried out by a national team of scientists and engineers from the Observatories of Arcetri, Bologna and Catania and the Fundacion Galileo Galilei.

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During its commissioning in July 2012, spectra of the sky and of luminous stars have been taken with GIANO. The night sky emits mainly airglow OH lines which are useful to check the wavelength calibration of the spectra. The sky spectrum obtained with GIANO provided a more complete and detailed catalog of OH lines with respect to existing catalogs, in which the frequency and intensity of the lines are directly measured with great accuracy. The results of this study are published on Astronomy & Astrophysics 2013, Vol. 555, p.78-83: "A GIANO-TNG high-resolution infrared spectrum of the airglow emission", led by Ernesto Oliva (Project Manager of GIANO at the Observatory of Arcetri) and 21 co-authors.

GIANO also allowed to study the spectra of three luminous, young stars in the red supergiant phase, close to their final evolutionary stage of supernovae. These stars belong to a stellar cluster in a highly obscured region of the Galaxy and are only visible in the infrared light. The high-resolution spectra gathered with GIANO allowed for the first time very detailed measurements of the chemical composition of these stars, including the abundance of both light and heavy metals. The results are published on Astronomy & Astrophysics 2013 (in press): "GIANO-TNG spectroscopy of red supergiants in the young star cluster RSGC2" led by Livia Origlia (Principal Investigator) and 21 co-authots.

Edited by Anna Gallazzi and Ernesto Oliva