High Resolution Spectroscopy using Fabry Perot Intereferometer Arrays: An Application to Searches for O$_{2}$ in Exoplanetary Atmospheres

TL;DR

This paper introduces a high-resolution spectroscopy method using Fabry Perot Interferometer arrays, enabling more compact instruments for exoplanet atmosphere studies, specifically targeting molecular oxygen detection.

Contribution

It presents a novel FPI array design achieving high spectral resolution with smaller optical elements, optimized for detecting O₂ in exoplanet atmospheres, reducing observation time.

Findings

FPI arrays can reach R~3-5×10^5 resolution.

FPI arrays reduce transit observations by ~30%.

Potential for further efficiency improvements.

Abstract

We present a novel implementation for extremely high resolution spectroscopy using custom-designed Fabry Perot Interferometer (FPI) arrays. For a given telescope aperture at the seeing limited case, these arrays can achieve resolutions well in excess of ${\rm R\sim10^5}$ using optical elements orders of magnitude smaller in size than standard echelle spectrographs of similar resolution. We apply this method specifically to the search for molecular oxygen in exoplanetary atmospheres using the ${\rm O_2}$ A-band at 0.76 ${\rm \mu m}$, and show how a FPI array composed of $\sim10$ etalons with parameters optimized for this science case can record ${\rm R=3-5\,\cdot10^5}$ spectra covering the full ${\rm O_2}$ A-band. Using simulated observations of the atmosphere of a transiting nearby Earth-like planet, we show how observations with a FPI array coupled to a long-slit spectrograph can reduce the number of transit observations needed to produce a ${\rm 3\sigma}$ detection of ${\rm O_2}$ by $\sim30\%$ compared to observations with a ${\rm R=10^5}$ echelle spectrograph. This, in turn, leads to a decrease in an observing program duration of several years. The number of transits needed for a ${\rm 3\sigma}$ detection can be further reduced by increasing the efficiency of FPI arrays using dualons (an etalon with a buried reflective layer), and by coupling the FPI array to a dedicated spectrograph optimized for the ${\rm O_2}$ A-band.