# Detection limits of exoplanetary atmospheres with 2-m class telescopes

## TL;DR

This paper explores the potential of 2-m class telescopes equipped with high-resolution spectrographs to detect exoplanetary atmospheres via transmission spectroscopy, especially for bright stars identified by TESS and PLATO.

## Contribution

It demonstrates the feasibility of using 2-m class telescopes for atmospheric detection of exoplanets and proposes a methodology for selecting promising targets from upcoming TESS data.

## Key findings

- Upper limit consistent with expectations for WASP-18b
- First analysis of its kind using 2-m class telescopes
- Highlights potential of smaller telescopes for exoplanet atmosphere studies

## Abstract

Transmission spectroscopy is an important technique to probe the atmospheres of exoplanets. With the advent of TESS and, in the future, of PLATO, more and more transiting planets around bright stars will be found and the observing time at large telescopes currently used to apply these techniques will not suffice. We demonstrate here that 2-m class telescopes equipped with spectrographs with high resolving power may be used for a certain number of potential targets. We obtained a time series of high-resolution FEROS spectra at the 2.2-m telescope at La Silla of the very hot Jupiter hosting planet WASP-18b and show that our upper limit is consistent with the expectations. This is the first analysis of its kind using 2-m class telescopes, and serves to highlight their potential. In this context, we then proceed to discuss the suitability of this class of telescopes for the upcoming flood of scientifically interesting targets from TESS space mission, and propose a methodology to select the most promising targets. This is of particular significance given that observing time on 2-m class telescopes is more readily available than on large 8-m class facilities.