Characterizing Accretion and Formation Mechanisms across the Brown Dwarf and Planetary Mass Regimes

Sarah Betti, Kate Follette, Kimberly Ward-Duong, Anne Peck, Beck Dacus, Jeff Bary, Gabriel-Dominique Marleau, Khalid Mohammad, Joe Palmo, Cailin Plunkett, Yuhiko Aoyama, Connor Robinson, Will Wang, Suzan Edwards

Recent discoveries of accreting brown dwarfs (BD) and exoplanets that appear to accrete at anomalously high rates have placed new importance on understanding the mechanisms that control their growth and formation. Accretion processes are well understood for stars, and substellar objects have been assumed to operate similarly; however, simulations suggest that the relation between object mass and mass accretion rate (M) is controlled by formation mechanism and that the accretion paradigm for substellar objects may also be different. I will discuss my work to disentangle systematic effects from true physical variation in substellar accretion properties using the Comprehensive Archive of Substellar and Planetary Accretion Rates (CASPAR). CASPAR consists of >1000 measured Ms from ~800 T-Tauri stars, BDs, and planetary mass companions (PMC), making it the largest compiled sample of ?s for accreting objects to-date. I systematically rederive physical and accretion properties for all objects in the database using Gaia distances, consistent ages and evolutionary models, and a single set of line-to-total accretion luminosity scaling relations. This rederivation of accretion properties decreases the M-M relation scatter by 7%, suggesting that the remaining broad scatter is attributable to physical effects such as age and variability. I will also highlight results from a 2.5 year observing campaign using SOAR/TripleSpec4.1 to measure ?s uniformly for a sample of BDs and PMCs. NIR Paβ, Paγ, and Brγ line luminosities and ratios allow us to compare my observations to accretion model predictions. As part of this survey, we detected NIR accretion lines from a protoplanet (Delorme 1 (AB)b) for the first time, and found that it accretes at a rate of 3-4x10-8 MJ/yr. Ratios of its NIR emission lines are most consistent with planetary shock accretion models, and its high M is suggestive of formation through disk fragmentation.