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Title: A data-driven approach for retrieving temperatures and abundances in brown dwarf atmospheres

Abstract

Brown dwarf spectra contain a wealth of information about their molecular abundances, temperature structure, and gravity. We present a new data driven retrieval approach, previously used in planetary atmosphere studies, to extract the molecular abundances and temperature structure from brown dwarf spectra. The approach makes few a priori physical assumptions about the state of the atmosphere. The feasibility of the approach is first demonstrated on a synthetic brown dwarf spectrum. Given typical spectral resolutions, wavelength coverage, and noise, property precisions of tens of percent can be obtained for the molecular abundances and tens to hundreds of K on the temperature profile. The technique is then applied to the well-studied brown dwarf, Gl 570D. From this spectral retrieval, the spectroscopic radius is constrained to be 0.75-0.83 R {sub J}, log (g) to be 5.13-5.46, and T {sub eff} to be between 804 and 849 K. Estimates for the range of abundances and allowed temperature profiles are also derived. The results from our retrieval approach are in agreement with the self-consistent grid modeling results of Saumon et al. This new approach will allow us to address issues of compositional differences between brown dwarfs and possibly their formation environments, disequilibrium chemistry, and missingmore » physics in current grid modeling approaches as well as a many other issues.« less

Authors:
;  [1];  [2];  [3]
  1. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  2. NASA Ames Research Center, Mail Stop 245-3, Moffett Field, CA 94035 (United States)
  3. Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)
Publication Date:
OSTI Identifier:
22365034
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 793; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ACCURACY; GRAVITATION; PLANETARY ATMOSPHERES; RADIANT HEAT TRANSFER; RESOLUTION; SIMULATION; SPECTRA; STARS; WAVELENGTHS

Citation Formats

Line, Michael R., Fortney, Jonathan J., Marley, Mark S., and Sorahana, Satoko, E-mail: mrline@ucsc.edu. A data-driven approach for retrieving temperatures and abundances in brown dwarf atmospheres. United States: N. p., 2014. Web. doi:10.1088/0004-637X/793/1/33.
Line, Michael R., Fortney, Jonathan J., Marley, Mark S., & Sorahana, Satoko, E-mail: mrline@ucsc.edu. A data-driven approach for retrieving temperatures and abundances in brown dwarf atmospheres. United States. doi:10.1088/0004-637X/793/1/33.
Line, Michael R., Fortney, Jonathan J., Marley, Mark S., and Sorahana, Satoko, E-mail: mrline@ucsc.edu. Sat . "A data-driven approach for retrieving temperatures and abundances in brown dwarf atmospheres". United States. doi:10.1088/0004-637X/793/1/33.
@article{osti_22365034,
title = {A data-driven approach for retrieving temperatures and abundances in brown dwarf atmospheres},
author = {Line, Michael R. and Fortney, Jonathan J. and Marley, Mark S. and Sorahana, Satoko, E-mail: mrline@ucsc.edu},
abstractNote = {Brown dwarf spectra contain a wealth of information about their molecular abundances, temperature structure, and gravity. We present a new data driven retrieval approach, previously used in planetary atmosphere studies, to extract the molecular abundances and temperature structure from brown dwarf spectra. The approach makes few a priori physical assumptions about the state of the atmosphere. The feasibility of the approach is first demonstrated on a synthetic brown dwarf spectrum. Given typical spectral resolutions, wavelength coverage, and noise, property precisions of tens of percent can be obtained for the molecular abundances and tens to hundreds of K on the temperature profile. The technique is then applied to the well-studied brown dwarf, Gl 570D. From this spectral retrieval, the spectroscopic radius is constrained to be 0.75-0.83 R {sub J}, log (g) to be 5.13-5.46, and T {sub eff} to be between 804 and 849 K. Estimates for the range of abundances and allowed temperature profiles are also derived. The results from our retrieval approach are in agreement with the self-consistent grid modeling results of Saumon et al. This new approach will allow us to address issues of compositional differences between brown dwarfs and possibly their formation environments, disequilibrium chemistry, and missing physics in current grid modeling approaches as well as a many other issues.},
doi = {10.1088/0004-637X/793/1/33},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 793,
place = {United States},
year = {2014},
month = {9}
}