Stars, Planets, and ISM Seminar
Apr
16
2025
Apr
16
2025
Description
Synthesizing Accretion and Circumplanetary Disk Properties of a Wide-Orbit Planet with HST and JWST
Many of the details of giant planet formation and evolution remain untested as there are few observational constraints on when they assemble and grow through gas accretion. Two key observational diagnostics—ultraviolet accretion signatures and mid-infrared circumplanetary disk excess—can offer critical insight into this process, but are rarely accessible for the same system because of practical challenges related to observing in the UV and the high contrasts of close-in planets. In this talk, I will present new UV and mid-IR direct imaging observations of the wide planetary-mass companion SR 12 c, obtained with HST/WFC3-UVIS and JWST/MIRI. These data expand SR 12 c’s spectral energy distribution (SED) to span from 0.2 to 21 microns, making it the most complete SED of a young imaged giant planet to date. The UV photometry reveals a strong Balmer continuum excess, and hot hydrogen slab models are used to derive an accretion luminosity and mass accretion rate for SR 12 c. In the mid-infrared, we detect substantial thermal excess from a circumplanetary disk and search for evidence of grain growth. This snapshot of active accretion onto SR 12 c adds to the growing sample of distant planets with detailed accretion and disk constraints, which together are establishing the timescales and physical processes governing the formation of giant planets.
Location
PMA 15.216B and online
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