GJ1132b planet/stellar radius at 0.7-4.5{mu}m

We combine our WFC3 results with transit depths from TESS and archival broadband and spectroscopic observations to find a featureless spectrum across 0.7 to 4.5{mu}m. GJ1132b therefore has a high mean molecular weight atmosphere, possesses a high-altitude aerosol layer, or has effectively no atmosphere. Higher-precision observations are required in order to differentiate between these possibilities.

We explore the impact of hot and cold starspots on the observed transmission spectrum GJ1132b, quantifying the amplitude of spot-induced transit depth features. Using a simple Poisson model, we estimate spot temperature contrasts, spot covering fractions, and spot sizes for GJ1132. These limits, as well as the modeling framework, may be useful for future observations of GJ1132b or other planets transiting similarly inactive M dwarfs.