H2-dominated Atmosphere as an Indicator of Second-generation Rocky White Dwarf Exoplanets
Abstract
Following the discovery of the first exoplanet candidate transiting a white dwarf (WD), a "white dwarf opportunity" for characterizing the atmospheres of terrestrial exoplanets around WDs is emerging. Large planet-to-star size ratios and hence large transit depths make transiting WD exoplanets favorable targets for transmission spectroscopy; conclusive detection of spectral features on an Earth-like planet transiting a close-by WD can be achieved within a medium James Webb Space Telescope program. Despite the apparently promising opportunity, however, the post-main sequence evolutionary history of a first-generation WD exoplanet has never been incorporated in atmospheric modeling. Furthermore, second-generation planets formed in WD debris disks have never been studied from a photochemical perspective. We demonstrate that transmission spectroscopy can identify a second-generation rocky WD exoplanet with a thick (~1 bar) H2-dominated atmosphere. In addition, we can infer outgassing activities of a WD exoplanet based on its transmission spectra and test photochemical runaway by studying CH4 buildup.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2022
- DOI:
- 10.3847/2041-8213/ac4788
- arXiv:
- arXiv:2201.08529
- Bibcode:
- 2022ApJ...925L..10L
- Keywords:
-
- 487;
- 498;
- 491;
- 1799;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 25 pages, 10 figures, 3 tables, accepted for publication in ApJ Letters