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Title: METAL DEPLETION AND WARM H{sub 2} IN THE BROWN DWARF 2M1207 ACCRETION DISK

Abstract

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{approx} 17,000-18,000) obtained in the 1150-1750 A and 2770-2830 A bandpasses reveal H{sub 2} emission excited by H I Ly{alpha} photons, several ionization states of carbon (C I-C IV), and hot gas emission lines of He II and N V (T {approx} 10{sup 4}-10{sup 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{sub 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{sub hole} {approx} 3R{sub *}), and constrain the physical conditions of the warm molecular phase of the disk (T(H{sub 2})more » {approx} 2500-4000 K). A second, most likely unresolved H{sub 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{sub 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{sub 2} emission from a warm layer in their disks, such as the well-studied TW Hya and DF Tau systems.« less

Authors:
; ;  [1];  [2]
  1. Center for Astrophysics and Space Astronomy, 389 UCB, University of Colorado, Boulder, CO 80309 (United States)
  2. JILA, University of Colorado and NIST, Boulder, CO 80309-0440 (United States)
Publication Date:
OSTI Identifier:
21448717
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 715; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/715/1/596; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; CARBON; DWARF STARS; EMISSION; FAR ULTRAVIOLET RADIATION; HYDROGEN; IONIZATION; LUMINOSITY; MASS; METALS; PHOTONS; T TAURI STARS; TELESCOPES; BINARY STARS; BOSONS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ELEMENTS; ERUPTIVE VARIABLE STARS; MASSLESS PARTICLES; NONMETALS; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; RADIATIONS; STARS; ULTRAVIOLET RADIATION; VARIABLE STARS

Citation Formats

France, Kevin, Brown, Alexander, Beland, Stephane, Linsky, Jeffrey L, and Froning, Cynthia S., E-mail: kevin.france@colorado.ed. METAL DEPLETION AND WARM H{sub 2} IN THE BROWN DWARF 2M1207 ACCRETION DISK. United States: N. p., 2010. Web. doi:10.1088/0004-637X/715/1/596.
France, Kevin, Brown, Alexander, Beland, Stephane, Linsky, Jeffrey L, & Froning, Cynthia S., E-mail: kevin.france@colorado.ed. METAL DEPLETION AND WARM H{sub 2} IN THE BROWN DWARF 2M1207 ACCRETION DISK. United States. doi:10.1088/0004-637X/715/1/596.
France, Kevin, Brown, Alexander, Beland, Stephane, Linsky, Jeffrey L, and Froning, Cynthia S., E-mail: kevin.france@colorado.ed. Thu . "METAL DEPLETION AND WARM H{sub 2} IN THE BROWN DWARF 2M1207 ACCRETION DISK". United States. doi:10.1088/0004-637X/715/1/596.
@article{osti_21448717,
title = {METAL DEPLETION AND WARM H{sub 2} IN THE BROWN DWARF 2M1207 ACCRETION DISK},
author = {France, Kevin and Brown, Alexander and Beland, Stephane and Linsky, Jeffrey L and Froning, Cynthia S., E-mail: kevin.france@colorado.ed},
abstractNote = {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{approx} 17,000-18,000) obtained in the 1150-1750 A and 2770-2830 A bandpasses reveal H{sub 2} emission excited by H I Ly{alpha} photons, several ionization states of carbon (C I-C IV), and hot gas emission lines of He II and N V (T {approx} 10{sup 4}-10{sup 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{sub 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{sub hole} {approx} 3R{sub *}), and constrain the physical conditions of the warm molecular phase of the disk (T(H{sub 2}) {approx} 2500-4000 K). A second, most likely unresolved H{sub 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{sub 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{sub 2} emission from a warm layer in their disks, such as the well-studied TW Hya and DF Tau systems.},
doi = {10.1088/0004-637X/715/1/596},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 715,
place = {United States},
year = {2010},
month = {5}
}