Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data
We present a new iron abundance analysis of the hyper metal-poor star HE 1327-2326, based on Fe ii lines detected in its UV spectral range for the first time. In a Cosmic Origins Spectrograph (COS) spectrum, five new Fe ii lines could be measured. A Si i line was also detected for the first time. We...
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| Format: | Article |
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American Astronomical Society
2019
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| Online Access: | https://hdl.handle.net/1721.1/121378 |
| _version_ | 1826197947645165568 |
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| author | Ezzeddine, Rana Frebel, Anna L. |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Ezzeddine, Rana Frebel, Anna L. |
| author_sort | Ezzeddine, Rana |
| collection | MIT |
| description | We present a new iron abundance analysis of the hyper metal-poor star HE 1327-2326, based on Fe ii lines detected in its UV spectral range for the first time. In a Cosmic Origins Spectrograph (COS) spectrum, five new Fe ii lines could be measured. A Si i line was also detected for the first time. We determine a 1D local thermodynamic equilibrium (LTE) Fe ii abundance of [Fe ii/H] = -5.99 ±0.25. We also investigate departures from LTE for both Fe i and Fe ii lines. Guided by 3D non-LTE (NLTE) analyses of other well-studied metal-poor stars, we identify potential "residual" 3D effects in HE 1327-2326 arising from the absence of full 3D NLTE Fe calculations. Accordingly, we employ measurements of 10 weak Fe i lines previously detected in an optical spectrum of HE 1327-2326, as no Fe i lines are detectable in our UV spectrum. Following our previous work, we adopt the 1D NLTE Fe i abundance of = -5.20 ±0.12 for HE 1327-2326. Adopting a value based on the optical Fe i rather than UV lines was heavily informed by our extensive investigation of model atmosphere and radiative transfer effects on different lines across the entire UV-optical wavelength range. An iron abundance of [Fe/H] = -5.20 ±0.12 is only 0.2 dex higher than what was used in previous studies. Accordingly, no previous conclusions regarding the nature of the star are affected. |
| first_indexed | 2024-09-23T10:56:13Z |
| format | Article |
| id | mit-1721.1/121378 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T10:56:13Z |
| publishDate | 2019 |
| publisher | American Astronomical Society |
| record_format | dspace |
| spelling | mit-1721.1/1213782022-09-27T16:04:48Z Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data Ezzeddine, Rana Frebel, Anna L. Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research We present a new iron abundance analysis of the hyper metal-poor star HE 1327-2326, based on Fe ii lines detected in its UV spectral range for the first time. In a Cosmic Origins Spectrograph (COS) spectrum, five new Fe ii lines could be measured. A Si i line was also detected for the first time. We determine a 1D local thermodynamic equilibrium (LTE) Fe ii abundance of [Fe ii/H] = -5.99 ±0.25. We also investigate departures from LTE for both Fe i and Fe ii lines. Guided by 3D non-LTE (NLTE) analyses of other well-studied metal-poor stars, we identify potential "residual" 3D effects in HE 1327-2326 arising from the absence of full 3D NLTE Fe calculations. Accordingly, we employ measurements of 10 weak Fe i lines previously detected in an optical spectrum of HE 1327-2326, as no Fe i lines are detectable in our UV spectrum. Following our previous work, we adopt the 1D NLTE Fe i abundance of = -5.20 ±0.12 for HE 1327-2326. Adopting a value based on the optical Fe i rather than UV lines was heavily informed by our extensive investigation of model atmosphere and radiative transfer effects on different lines across the entire UV-optical wavelength range. An iron abundance of [Fe/H] = -5.20 ±0.12 is only 0.2 dex higher than what was used in previous studies. Accordingly, no previous conclusions regarding the nature of the star are affected. National Science Foundation (U.S.) (Grant PHY-1430152) National Science Foundation (U.S.) (Grant AST-1255160) 2019-06-21T16:40:53Z 2019-06-21T16:40:53Z 2018-08 2018-07 2019-03-22T15:24:39Z Article http://purl.org/eprint/type/JournalArticle 1538-4357 https://hdl.handle.net/1721.1/121378 Ezzeddine, Rana and Anna Frebel. “Revisiting the Iron Abundance in the Hyper Iron-Poor Star HE 1327–2326 with UV COS/HST Data.” Astrophysical Journal 863, 2 (August 2018): 168 © 2018 American Astronomical Society http://dx.doi.org/10.3847/1538-4357/AAD3CB Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Astronomical Society The Astrophysical Journal |
| spellingShingle | Ezzeddine, Rana Frebel, Anna L. Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title | Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title_full | Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title_fullStr | Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title_full_unstemmed | Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title_short | Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327–2326 with UV COS/HAT Data |
| title_sort | revisiting the iron abundance in the hyper iron poor star he 1327 2326 with uv cos hat data |
| url | https://hdl.handle.net/1721.1/121378 |
| work_keys_str_mv | AT ezzeddinerana revisitingtheironabundanceinthehyperironpoorstarhe13272326withuvcoshatdata AT frebelannal revisitingtheironabundanceinthehyperironpoorstarhe13272326withuvcoshatdata |