Research

Many of the details of giant planet formation and evolution remain untested as there are few observational constraints on when gas giants grow through gas accretion. In my recently-submitted paper, we present new 0.2-0.7 µm UV-through-red optical imaging of the young (~2 Myr), wide-orbit planetary-mass companion SR 12 c from the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. SR 12 c exhibits strong accretion-related continuum excess blueward of ~5000 Å and clear signs of the Balmer jump at 3646 Å. Modeling this excess with hot hydrogen slab models, we derive a total accretion luminosity and a mass accretion rate. Based on its mass of ~13 M_Jup and age of 2 Myr, SR 12 c must have had a past accretion rate that was on average several orders of magnitude higher; it is now at the end stages of assembly. No accretion variability is evident over the month-long baseline of the WFC3 observations, but the Hα emission line strength decreases by 90% compared to the reported flux from five years earlier. We assemble the most complete spectral energy distribution of a young giant planet to date (above), spanning the UV through sub-mm wavelengths (0.2-880 µm). This adds SR 12 c to the small yet growing sample of planets with detailed accretion and disk constraints, which together are beginning to establish the diversity of timescales and physical processes governing the formation of giant planets.

Over the past few years, there have been a handful of detections (<10) of circumplanetary disks (CPDs), with a reported disk fraction of around 50% for long period planets. However, many of their basic properties remain poorly constrained. We have ~50 years of studies building a comprehensive understanding of circumstellar/protoplanetary disk physics and dissipation timescales, as well as accretion properties, but all of these areas are understudied in the planetary-mass regime. To remedy this, we launched a program with the goal of understanding the diversity of accretion and CPD properties across a range of ages and masses, and whether there is any correlation between accretion and disk properties. This program will place the first constraints on a population of planets and CPDs in a uniform framework. I am leading this effort for my PhD thesis work, levying our sample of UV observations from Cycle 28 HST GO 16302 and mid-IR observations from Cycle 1 JWST GO 2311.