# Mass Loss from the Exoplanet WASP-12b Inferred from $\textit{Spitzer}$ Phase Curves

## TL;DR

This study analyzes Spitzer phase curves of exoplanet WASP-12b, revealing infrared signatures of mass loss, possibly due to atmospheric escape or accretion, with implications for its orbital decay and stellar irradiation effects.

## Contribution

First detection of infrared gas emission indicating mass loss from WASP-12b using phase curve analysis, highlighting unique atmospheric escape processes in ultra-hot Jupiters.

## Key findings

- Infrared emission from stripped gas detected at 4.5 μm
- Evidence of phase offset variability at 3.6 μm
- Potential link between mass loss and orbital decay

## Abstract

The exoplanet WASP-12b is the prototype for the emerging class of ultra-hot, Jupiter-mass exoplanets. Past models have predicted---and near ultra-violet observations have shown---that this planet is losing mass. We present an analysis of two sets of 3.6 $\mu$m and 4.5 $\mu$m $\textit{Spitzer}$ phase curve observations of the system which show clear evidence of infrared radiation from gas stripped from the planet, and the gas appears to be flowing directly toward or away from the host star. This accretion signature is only seen at 4.5 $\mu$m, not at 3.6 $\mu$m, which is indicative either of CO emission at the longer wavelength or blackbody emission from cool, $\lesssim$ 600 K gas. It is unclear why WASP-12b is the only ultra-hot Jupiter to exhibit this mass loss signature, but perhaps WASP-12b's orbit is decaying as some have claimed, while the orbits of other exoplanets may be more stable; alternatively, the high energy irradiation from WASP-12A may be stronger than the other host stars. We also find evidence for phase offset variability at the level of $6.4\sigma$ ($46.2^{\circ}$) at 3.6 $\mu$m.