AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS

Tsuji, Takashi; Yamamura, Issei; Sorahana, Satoko

doi:10.1088/0004-637X/734/2/73

Title: AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS

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Abstract

Recent observations with the infrared astronomical satellite AKARI have shown that the CO{sub 2} bands at 4.2 {mu}m in three brown dwarfs are much stronger than expected from the unified cloudy model (UCM) based on recent solar C and O abundances. This result has been a puzzle, but we now find it is simply due to the effect of C and O abundances. We show that these strong CO{sub 2} bands can be explained with the UCMs based on the classical C and O abundances (log A{sub C} and log A{sub O}), which are about 0.2 dex larger compared to the recent values. Since three other brown dwarfs could be interpreted fairly well with the recent solar C and O abundances, we require at least two model sequences based on the different chemical compositions to interpret all the AKARI spectra. The reason is that the CO{sub 2} band is especially sensitive to C and O abundances, since the CO{sub 2} abundance depends approximately on A{sub C} A{sup 2}{sub O}-the cube of C and O abundances. For this reason, even low-resolution spectra of very cool dwarfs, especially of CO{sub 2}, cannot be understood unless a model with proper abundances is applied.more »« less

Authors:

Tsuji, Takashi ^[1]; Yamamura, Issei; Sorahana, Satoko ^[2]

Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
Institute of Space and Astronautical Science (ISAS), JAXA, Yoshino-dai 3-1-1, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

Publication Date:: Mon Jun 20 00:00:00 EDT 2011

OSTI Identifier:: 21576619

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 734; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/734/2/73; Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON; CARBON DIOXIDE; CHEMICAL COMPOSITION; ELEMENT ABUNDANCE; OXYGEN; STARS; STELLAR ATMOSPHERES; ABUNDANCE; ATMOSPHERES; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; ELEMENTS; NONMETALS; OXIDES; OXYGEN COMPOUNDS

Citation Formats


                    Tsuji, Takashi, Yamamura, Issei, and Sorahana, Satoko. AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS.  United States: N. p., 2011. 
        Web.  doi:10.1088/0004-637X/734/2/73.

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                    Tsuji, Takashi, Yamamura, Issei, & Sorahana, Satoko. AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS.  United States.  https://doi.org/10.1088/0004-637X/734/2/73

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                    Tsuji, Takashi, Yamamura, Issei, and Sorahana, Satoko. 2011.  
        "AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS".  United States.  https://doi.org/10.1088/0004-637X/734/2/73.

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@article{osti_21576619,

  title        = {AKARI OBSERVATIONS OF BROWN DWARFS. II. CO{sub 2} AS PROBE OF CARBON AND OXYGEN ABUNDANCES IN BROWN DWARFS},

  author       = {Tsuji, Takashi and Yamamura, Issei and Sorahana, Satoko},

  abstractNote = {Recent observations with the infrared astronomical satellite AKARI have shown that the CO{sub 2} bands at 4.2 {mu}m in three brown dwarfs are much stronger than expected from the unified cloudy model (UCM) based on recent solar C and O abundances. This result has been a puzzle, but we now find it is simply due to the effect of C and O abundances. We show that these strong CO{sub 2} bands can be explained with the UCMs based on the classical C and O abundances (log A{sub C} and log A{sub O}), which are about 0.2 dex larger compared to the recent values. Since three other brown dwarfs could be interpreted fairly well with the recent solar C and O abundances, we require at least two model sequences based on the different chemical compositions to interpret all the AKARI spectra. The reason is that the CO{sub 2} band is especially sensitive to C and O abundances, since the CO{sub 2} abundance depends approximately on A{sub C} A{sup 2}{sub O}-the cube of C and O abundances. For this reason, even low-resolution spectra of very cool dwarfs, especially of CO{sub 2}, cannot be understood unless a model with proper abundances is applied. For the same reason, CO{sub 2} is an excellent indicator of C and O abundances, and we can now estimate C and O abundances of brown dwarfs as follows: Three of the six brown dwarfs observed with AKARI should have high C and O abundances similar to the classical solar values (e.g., log A{sub C} = 8.60 and log A{sub O} = 8.92), but the other three may have low C and O abundances similar to the recent solar values (e.g., log A{sub C} = 8.39 and log A{sub O} = 8.69). This result implies that three of the six brown dwarfs are highly metal-rich relative to the Sun, if the recent solar C and O abundances are correct.},

  doi          = {10.1088/0004-637X/734/2/73},

  url          = {https://www.osti.gov/biblio/21576619},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 734,

  place        = {United States},

  year         = {Mon Jun 20 00:00:00 EDT 2011},

  month        = {Mon Jun 20 00:00:00 EDT 2011}

}

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