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Publication Date

2022-05-10

First Advisor

Kim Ward-Duong

Second Advisor

Kate Follette

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Astronomy

Keywords

astronomy, sub-stellar objects, brown dwarfs, brown dwarf formation, star formation

Abstract

Brown dwarfs occupy a boundary zone between stars and planets, helping to reveal the secrets of planet and star formation. It is unclear whether young brown dwarfs have similar magnetic field geometries or undergo the same magnetospheric accretion processes as young stars. The matter surrounding an accreting brown dwarf may have lower infall velocities and a larger filling factor covering the brown dwarf's surface, akin to predictions for accreting planets. Different formation scenarios would also yield different initial conditions, affecting the amount of gas and dust that can accrete onto brown dwarfs. Over the past 20 years, the young ~ 25 Mjup brown dwarf 2MASSW J1207-3932 (hereafter 2M1207), a member of the TW Hya Association, has been observed at FUV, NUV, optical, and infrared wavelengths and confirmed to be accreting material from its surrounding disk. In fact, 2M1207 is the only accreting brown dwarf that has been observed across such an expansive wavelength range. In this work, I combine multiple archival datasets to construct a broad, multi-wavelength spectral template for accreting substellar objects and measure the empirical accretion luminosity directly. I fit the observed spectrum with photospheric templates and accretion shock models to constrain the physical properties and accretion parameters for 2M1207. This study feature an unprecedented comprehensive emission line analysis for a substellar object. In addition, I investigate whether stellar and planetary scaling relationships between accretion luminosity and line emission remain valid in the substellar regime. This work allows us to more accurately estimate mass accretion rates for brown dwarfs, which will ultimately inform the mechanism of brown dwarf formation. Having such a benchmark object is important for future substellar observations.

Rights

©2022 Lillian Yushu Jiang. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

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