\emph{In-situ} determination of astro-comb calibrator lines to better than 10 cm s$^{-1}$

TL;DR

This paper presents an in-situ method to accurately determine and correct systematic spectral shifts in astro-comb calibrators caused by Fabry-Pérot cavity dispersion, enabling wavelength calibration better than 10 cm/s for high-precision astrophysical spectroscopy.

Contribution

The paper introduces a practical in-situ technique to measure and correct systematic shifts in astro-comb lines due to cavity dispersion, improving calibration accuracy for astrophysical spectrographs.

Findings

Achieved calibration accuracy better than 10 cm/s.

Demonstrated in-situ measurement of systematic spectral shifts.

Applicable at telescope-based spectrographs for improved RV detection.

Abstract

Improved wavelength calibrators for high-resolution astrophysical spectrographs will be essential for precision radial velocity (RV) detection of Earth-like exoplanets and direct observation of cosmological deceleration. The astro-comb is a combination of an octave-spanning femtosecond laser frequency comb and a Fabry-P\'erot cavity used to achieve calibrator line spacings that can be resolved by an astrophysical spectrograph. Systematic spectral shifts associated with the cavity can be 0.1-1 MHz, corresponding to RV errors of 10-100 cm/s, due to the dispersive properties of the cavity mirrors over broad spectral widths. Although these systematic shifts are very stable, their correction is crucial to high accuracy astrophysical spectroscopy. Here, we demonstrate an \emph{in-situ} technique to determine the systematic shifts of astro-comb lines due to finite Fabry-P\'erot cavity dispersion. The technique is practical for implementation at a telescope-based spectrograph to enable wavelength calibration accuracy better than 10 cm/s.