Contributed Talk - Splinter Exoplanets

Thursday, 24 September 2020, 11:30   (virtual room D)

Hydrogen-line emission from accreting planets: fluxes, line shapes, and a new correlation

Gabriel-Dominique Marleau, Yuhiko Aoyama et al.
Universität Tübingen, Tsinghua University (Beijing)

In the core-accretion formation scenario of gas giant planets, most of the gas accreting onto a planet is likely processed through an accretion shock. This shock sets the forming planet's structure and thus its observable post-formation luminosity, and the radiative feedback can affect the circumplanetary and circumstellar discs thermally and chemically. Also, there has been recent direct evidence for ongoing accretion at PDS 70 b and c and Delorme 1 (AB)b, and searches with SPHERE, MUSE, MagAO-X, etc. should soon reveal more forming planets. Using the non-LTE, chemical-kinetics code of Aoyama et al. (2018), we present the first predictions of spectrally-resolved line emission from the planetary-surface accretion shock. We focus on the brightest accretion tracers: H alpha, H beta, Br gamma, etc.. In several cases, molecular absorption in the accretion flow leaves an imprint visible in the line shape at high resolution (R ~ 15'000), providing signatures of the accretion geometry. We also introduce a relation between the H alpha luminosity and the accretion luminosity appropriate for accreting planets, which can be used instead of extrapolations from the stellar regime.