Constraining neutral hydrogen outflow and stellar host Lyman-α reconstruction for transiting super-Earth GJ1132b
Abstract
GJ 1132b is one of the few known Earth-sized planets, and at 12pc away it is also one of the closest known transiting planets. At 20x Earth insolation, this planet is too hot to be habitable but we can use it to learn about the presence and volatile content of rocky planet atmospheres around M dwarf stars. Using Hubble STIS spectra obtained during primary transit, we search for a Lyα transit. If we were to observe a deep Lyα transit, that would indicate the presence of a large neutral hydrogen envelope flowing from GJ 1132b. On the other hand, ruling out deep absorption from neutral hydrogen may indicate that this planet is not losing large amounts of neutral hydrogen, indicating it has either retained its volatiles or lost them very early in the star's life. We do not conclusively detect a transit but report a quantitative upper limit on the effective size of the cloud. We also analyze the stellar variability and Lyα spectrum of GJ 1132, a slowly-rotating 0.18 solar mass M dwarf with previously uncharacterized UV activity. Understanding the role that UV variability plays in planetary atmospheres and volatile retention is crucial to assess atmospheric evolution and the habitability of cooler rocky planets.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23322607W