# Identifying Candidate Atmospheres on Rocky M dwarf Planets via Eclipse Photometry

## TL;DR

This paper proposes a rapid infrared photometry method during secondary eclipses to identify candidate atmospheres on rocky M dwarf planets, enabling efficient atmospheric surveys with JWST.

## Contribution

It introduces a new, less observationally intensive technique using eclipse photometry to detect atmospheric heat redistribution on rocky exoplanets.

## Key findings

- JWST can detect heat redistribution with 1-2 eclipses for O(1) bar atmospheres.
- Eclipse photometry is faster than traditional spectroscopy for atmospheric detection.
- Approximately 100 hot rocky planets from TESS could be surveyed quickly for atmospheres.

## Abstract

Most rocky planets in the galaxy orbit a cool host star, and there is large uncertainty among theoretical models whether these planets can retain an atmosphere. The James Webb Space Telescope (JWST) might be able to settle this question empirically, but most proposals for doing so require large observational effort because they are based on spectroscopy. Here we show that infrared photometry of secondary eclipses could quickly identify "candidate" atmospheres, by searching for rocky planets with atmospheres thick enough that atmospheric heat transport noticeably reduces their dayside thermal emission compared to that of a bare rock. For a planet amenable to atmospheric follow-up, we find that JWST should be able to confidently detect the heat redistribution signal of an O(1) bar atmosphere with one to two eclipses. One to two eclipses is generally much less than the effort needed to infer an atmosphere via transmission or emission spectroscopy. Candidate atmospheres can be further validated via follow-up spectroscopy or phase curves. In addition, because this technique is fast it could enable a first atmospheric survey of rocky exoplanets with JWST. We estimate that the TESS mission will find ~100 planets that are too hot to be habitable but that can be quickly probed via eclipse photometry. Knowing whether hot, rocky planets around M dwarfs have atmospheres is important not only for understanding the evolution of uninhabitable worlds: if atmospheres are common on hot planets, then cooler, potentially habitable planets around M dwarfs are also likely to have atmospheres.