H-alpha Variability in PTFO8-8695 and the Possible Direct Detection of Emission from a 2 Million Year Old Evaporating Hot Jupiter

TL;DR

This study detects variable H-alpha emission from a young star, likely originating from a hot Jupiter exoplanet undergoing mass loss, providing potential direct evidence of such an evaporating planet.

Contribution

First direct detection attempt of H-alpha emission from a young hot Jupiter, indicating planetary origin over stellar activity or accretion.

Findings

Excess H-alpha emission moves with expected planetary velocity.

Emission likely from an extended volume around the planet.

Planet is probably losing mass via Roche lobe overflow.

Abstract

We use high time cadence, high spectral resolution optical observations to detect excess H-alpha emission from the 2 - 3 Myr old weak lined T Tauri star PTFO8-8695. This excess emission appears to move in velocity as expected if it were produced by the suspected planetary companion to this young star. The excess emission is not always present, but when it is, the predicted velocity motion is often observed. We have considered the possibility that the observed excess emission is produced by stellar activity (flares), accretion from a disk, or a planetary companion; we find the planetary companion to be the most likely explanation. If this is the case, the strength of the H-alpha line indicates that the emission comes from an extended volume around the planet, likely fed by mass loss from the planet which is expected to be overflowing its Roche lobe.