A crucial test for astronomical spectrograph calibration with frequency combs

• DOI: 10.1038/s41550-020-1010-x
• Publication Date: 2020-02-10T17:04:02Z
• Authors: Rafael A. Probst; Dinko Milaković; Borja Toledo-Padrón; Gaspare Lo Curto; Gerardo Avila; Anna Brucalassi; Bruno L. Canto Ma...; Izan de Castro Leão; Massimiliano Espo...; Jonay I. González...; Frank Grupp; Theodor W. Hänsch; Hanna Kellermann; Florian Kerber; Olaf Mandel; Antonio Manescau; Eszter Pozna; Rafael Rebolo; José R. de Medeiros; Tilo Steinmetz; Alejandro Suárez ...; Thomas Udem; Josefina Urrutia; Yuanjie Wu; Luca Pasquini; Ronald Holzwarth
• Keywords: FOS: Physical sciences; Astrophysics - Instrumentation and Methods for Astrophysics; Instrumentation and Methods for Astrophysics (astro-ph.IM)

22 pages, 14 figures. View the Nature Astronomy publication under https://rdcu.be/b1tMB . Nature Astronomy article available under https://www.nature.com/articles/s41550-020-1010-x<br/>Laser frequency combs (LFCs) are well on their way to becoming the next-generation calibration sources for precision astronomical spectroscopy. This development is considered key in the hunt for low-mass rocky exoplanets around solar-type stars whose discovery with the radial-velocity method requires cm/s Doppler precision. In order to prove such precise calibration with an LFC, it must be compared to another calibrator of at least the same precision. Being the best available spectrograph calibrator, this means comparing it to a second - fully independent - LFC. This test had long been pending, but our installation of two LFCs at the ultra-stable spectrograph HARPS presented the so far unique opportunity for simultaneous calibrations with two separate LFCs. Although limited in time, the test results confirm the 1 cm/s stability that has long been anticipated by the astronomical community.<br/>