First on-sky results of a FIOS prototype, a Fabry Perot Based Instrument for Oxygen Searches

TL;DR

This paper introduces a novel Fabry Perot Interferometer-based instrument that significantly boosts spectral resolution for exoplanet atmosphere studies, enabling detection of biosignature gases like oxygen with existing spectrographs.

Contribution

The paper presents a new high-resolution spectroscopy approach using a chained Fabry Perot array as a resolution booster for existing spectrographs, achieving R>300,000.

Findings

On-sky demonstration of a prototype reaching R=250,000-350,000

Modeling suggests an eight-arm array can exceed R=300,000

The FPI booster can be integrated with current spectrographs for enhanced resolution

Abstract

The upcoming Extremely Large Telescopes (ELTs) are expected to have the collecting area required to detect potential biosignature gases such as molecular oxygen, $\mathrm{O_2}$, in the atmosphere of terrestrial planets around nearby stars. One of the most promising detection methods is transmission spectroscopy. To maximize our capability to detect $\mathrm{O_2}$ using this method, spectral resolutions $\mathrm{R}\geq 300,000$ are required to fully resolve the absorption lines in an Earth-like exoplanet atmosphere and disentangle the signal from telluric lines. Current high-resolution spectrographs typically achieve a spectral resolution of $\mathrm{R}\sim100,000$. Increasing the resolution in seeing limited observations/instruments requires drastically larger optical components, making these instruments even more expensive and hard to fabricate and assemble. Instead, we demonstrate a new approach to high-resolution spectroscopy. We implemented an ultra-high spectral resolution booster to be coupled in front of a high-resolution spectrograph. The instrument is based on a chained Fabry Perot array which generates a hyperfine spectral profile. We present on-sky telluric observations with a lab demonstrator. Depending on the configuration, this two-arm prototype reaches a resolution of R=250,000-350,000. After carefully modeling the prototype's behavior, we propose a Fabry Perot Interferometer (FPI) design for an eight-arm array configuration aimed at ELTs capable of exceeding R=300,000. The novel FPI resolution booster can be plugged in at the front end of an existing R=100,000 spectrograph to overwrite the spectral profile with a higher resolution for exoplanet atmosphere studies.