Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B
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2024
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| author | Kawashima, Yui Kawahara, Hajime Kasagi, Yui Ishikawa, Hiroyuki Tako Masuda, Kento Kotani, Takayuki Kudo, Tomoyuki Hirano, Teruyuki Kuzuhara, Masayuki Nugroho, Stevanus K Livingston, John Harakawa, Hiroki Nishikawa, Jun Omiya, Masashi Takarada, Takuya Tamura, Motohide Ueda, Akitoshi |
| author_facet | Kawashima, Yui Kawahara, Hajime Kasagi, Yui Ishikawa, Hiroyuki Tako Masuda, Kento Kotani, Takayuki Kudo, Tomoyuki Hirano, Teruyuki Kuzuhara, Masayuki Nugroho, Stevanus K Livingston, John Harakawa, Hiroki Nishikawa, Jun Omiya, Masashi Takarada, Takuya Tamura, Motohide Ueda, Akitoshi |
| contents | Brown dwarfs provide a unique opportunity to study atmospheres and their physical and chemical processes with high precision, especially in temperature ranges relevant to exoplanets. In this study, we performed high-resolution ($R \sim 70,000$) spectroscopy using Subaru/IRD ($Y$, $J$, $H$-bands) of the T7.0p-type object Gl 229 B, the first discovered T-type brown dwarf, which orbits an M1V host star at a separation of 33 au. We conducted atmospheric retrieval on the reduced $H$-band spectrum using the high-resolution spectrum model compatible with automatic differentiation and GPU, ExoJAX. In contrast to previous retrieval studies on medium-resolution spectra, we obtained a C/O ratio consistent with that of the host star, aligning with the expected formation process for such a massive brown dwarf. Additionally, based on the strong constraint on temperature from the high-resolution spectrum and previously measured photometric magnitude, our analysis indicates that Gl 229 B is a binary, which was also proposed by Brandt et al. (2021) and recently confirmed by Xuan et al. (2024). Finally, we validated current molecular line lists by leveraging the obtained high-resolution, high signal-to-noise ratio spectrum of this warm ($\sim 900$ K) atmosphere. This study highlights the importance of observing companion brown dwarfs as benchmark objects for establishing characterization techniques for low-mass objects and enhancing our understanding of their atmospheres, given the wealth of available information and the relative ease of observation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_11561 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B Kawashima, Yui Kawahara, Hajime Kasagi, Yui Ishikawa, Hiroyuki Tako Masuda, Kento Kotani, Takayuki Kudo, Tomoyuki Hirano, Teruyuki Kuzuhara, Masayuki Nugroho, Stevanus K Livingston, John Harakawa, Hiroki Nishikawa, Jun Omiya, Masashi Takarada, Takuya Tamura, Motohide Ueda, Akitoshi Earth and Planetary Astrophysics Solar and Stellar Astrophysics Brown dwarfs provide a unique opportunity to study atmospheres and their physical and chemical processes with high precision, especially in temperature ranges relevant to exoplanets. In this study, we performed high-resolution ($R \sim 70,000$) spectroscopy using Subaru/IRD ($Y$, $J$, $H$-bands) of the T7.0p-type object Gl 229 B, the first discovered T-type brown dwarf, which orbits an M1V host star at a separation of 33 au. We conducted atmospheric retrieval on the reduced $H$-band spectrum using the high-resolution spectrum model compatible with automatic differentiation and GPU, ExoJAX. In contrast to previous retrieval studies on medium-resolution spectra, we obtained a C/O ratio consistent with that of the host star, aligning with the expected formation process for such a massive brown dwarf. Additionally, based on the strong constraint on temperature from the high-resolution spectrum and previously measured photometric magnitude, our analysis indicates that Gl 229 B is a binary, which was also proposed by Brandt et al. (2021) and recently confirmed by Xuan et al. (2024). Finally, we validated current molecular line lists by leveraging the obtained high-resolution, high signal-to-noise ratio spectrum of this warm ($\sim 900$ K) atmosphere. This study highlights the importance of observing companion brown dwarfs as benchmark objects for establishing characterization techniques for low-mass objects and enhancing our understanding of their atmospheres, given the wealth of available information and the relative ease of observation. |
| title | Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2410.11561 |