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arXiv · 1808.00860

Broadband near-infrared astronomical spectrometer calibration and on-sky validation with an electro-optic laser frequency comb

Ewelina Obrzud·Monica Rainer·Avet Harutyunyan·Bruno Chazelas·Massimo Cecconi·Adriano Ghedina·Emilio Molinari·Stefan Kundermann·Steve Lecomte·Francesco Pepe·François Wildi·François Bouchy·Tobias Herr
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Abstract

The quest for extrasolar planets and their characterisation as well as studies of fundamental physics on cosmological scales rely on capabilities of high-resolution astronomical spectroscopy. A central requirement is a precise wavelength calibration of astronomical spectrographs allowing for extraction of subtle wavelength shifts from the spectra of stars and quasars. Here, we present an all-fibre, 400 nm wide near-infrared frequency comb based on electro-optic modulation with 14.5 GHz comb line spacing. Tests on the high-resolution, near-infrared spectrometer GIANO-B show a photon-noise limited calibration precision of <10 cm/s as required for Earth-like planet detection. Moreover, the presented comb provides detailed insight into particularities of the spectrograph such as detector inhomogeneities and differential spectrograph drifts. The system is validated in on-sky observations of a radial velocity standard star (HD221354) and telluric atmospheric absorption features. The advantages of the system include simplicity, robustness and turn-key operation, features that are valuable at the observation sites.

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Ewelina Obrzud, Monica Rainer, Avet Harutyunyan, Bruno Chazelas, Massimo Cecconi, Adriano Ghedina, Emilio Molinari, Stefan Kundermann, Steve Lecomte, Francesco Pepe, François Wildi, François Bouchy, Tobias Herr. 2018-08-02. Broadband near-infrared astronomical spectrometer calibration and on-sky validation with an electro-optic laser frequency comb. https://doi.org/10.1364/oe.26.034830

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