2010/04/07 by Kevin France, Jeffrey L. Linsky, Jeffrey L. Linksy +4 · 1 citation
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Galaxy #Hubble space telescope #Luminosity #Outflow #Physics #RADIUS #Space Telescope Imaging Spectrograph #Spectral line #Stars #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/715/1/596
ApJ, accepted. 12 pages, 10 figures. 3 tables.
arxiv created 2010/04/07 · openalex publication_date 2010/04/30 · arxiv updated 2015/05/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present new far-ultraviolet observations of the young M8 brown dwarf 2MASS J12073346−3932539, which is surrounded by an accretion disk. The data were obtained using the Hubble Space Telescope -Cosmic Origins Spectrograph. Moderate-resolution spectra ( R ≈ 17,000–18,000) obtained in the 1150–1750 Å and 2770–2830 Å bandpasses reveal H 2 emission excited by H i Lyα photons, several ionization states of carbon (C i –C iv ), and hot gas emission lines of He ii and N v ( T ≈ 10 4 –10 5 K). Emission from some species that would be found in a typical thermal plasma at this temperature (Si ii , Si iii , Si iv , and Mg ii ) is not detected. The non-detections indicate that these refractory elements are depleted into grains, and that accretion shocks dominate the production of the hot gas observed on 2MASS J12073346−3932539. We use the observed C iv luminosity to constrain the mass accretion rate in this system. We use the kinematically broadened H 2 profile to confirm that the majority of the molecular emission arises in the disk, measure the radius of the inner hole of the disk ( R hole ≈ 3 R * ), and constrain the physical conditions of the warm molecular phase of the disk ( T (H 2 ) ≈ 2500–4000 K). A second, most likely unresolved H 2 component is identified. This feature is either near the stellar surface in the region of the accretion shock or in a molecular outflow, although the possibility that this Jovian-like emission arises on the dayside disk of a 6 M J companion (2M1207b) cannot be conclusively ruled out. In general, we find that this young brown dwarf disk system is a low-mass analog to classical T Tauri stars that are observed to produce H 2 emission from a warm layer in their disks, such as the well-studied TW Hya and DF Tau systems.