Demonstration of On-Sky Calibration of Astronomical Spectra using a 25 GHz near-IR Laser Frequency Comb

TL;DR

This paper demonstrates the on-sky calibration of astronomical spectra using a 25 GHz near-infrared laser frequency comb, achieving high radial velocity precision for stellar observations.

Contribution

It introduces a stabilized 25 GHz laser frequency comb for on-sky calibration, enabling precise radial velocity measurements in the near-infrared.

Findings

Achieved ~10 m/s radial velocity precision.

Deployed the comb at the Hobby-Eberly telescope.

Calibrated spectra over multiple nights and orders.

Abstract

We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of \sim10 m/s (\sim6 MHz) was achieved from the comb-calibrated spectra.