DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD
It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a liter...
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| Format: | Article |
| Language: | en_US |
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Institute of Physics Publishing
2014
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| Online Access: | http://hdl.handle.net/1721.1/88425 https://orcid.org/0000-0001-7727-1640 https://orcid.org/0000-0002-2139-7145 |
| _version_ | 1826210850852044800 |
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| author | Frebel, Anna L. Casey, Andrew R. Jacobson, Heather Yu, QinQin |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Frebel, Anna L. Casey, Andrew R. Jacobson, Heather Yu, QinQin |
| author_sort | Frebel, Anna L. |
| collection | MIT |
| description | It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a literature sample with –3.3 < [Fe/H] < –2.5. Excitation temperatures were determined from Fe I line abundances in high-resolution optical spectra in the wavelength range of ~3700-~7000 Å, although shorter wavelength ranges, up to 4750-6800 Å, can also be employed, and compared with photometric literature temperatures. Our adjustment scheme increases the temperatures up to several hundred degrees for cool red giants, while leaving the near-main-sequence stars mostly unchanged. Hence, it brings the excitation temperatures in good agreement with photometrically derived values. The modified temperature also influences other stellar parameters, as the Fe I-Fe II ionization balance is simultaneously used to determine the surface gravity, while also forcing no abundance trend on the absorption line strengths to obtain the microturbulent velocity. As a result of increasing the temperature, the often too low gravities and too high microturbulent velocities in red giants become higher and lower, respectively. Our adjustment scheme thus continues to build on the advantage of deriving temperatures from spectroscopy alone, independent of reddening, while at the same time producing stellar chemical abundances that are more straightforwardly comparable to studies based on photometrically derived temperatures. Hence, our method may prove beneficial for comparing different studies in the literature as well as the many high-resolution stellar spectroscopic surveys that are or will be carried out in the next few years. |
| first_indexed | 2024-09-23T14:56:25Z |
| format | Article |
| id | mit-1721.1/88425 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:56:25Z |
| publishDate | 2014 |
| publisher | Institute of Physics Publishing |
| record_format | dspace |
| spelling | mit-1721.1/884252022-10-01T23:29:32Z DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD Frebel, Anna L. Casey, Andrew R. Jacobson, Heather Yu, QinQin Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research Frebel, Anna L. Casey, Andrew R. Jacobson, Heather Yu, Qinsi It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a literature sample with –3.3 < [Fe/H] < –2.5. Excitation temperatures were determined from Fe I line abundances in high-resolution optical spectra in the wavelength range of ~3700-~7000 Å, although shorter wavelength ranges, up to 4750-6800 Å, can also be employed, and compared with photometric literature temperatures. Our adjustment scheme increases the temperatures up to several hundred degrees for cool red giants, while leaving the near-main-sequence stars mostly unchanged. Hence, it brings the excitation temperatures in good agreement with photometrically derived values. The modified temperature also influences other stellar parameters, as the Fe I-Fe II ionization balance is simultaneously used to determine the surface gravity, while also forcing no abundance trend on the absorption line strengths to obtain the microturbulent velocity. As a result of increasing the temperature, the often too low gravities and too high microturbulent velocities in red giants become higher and lower, respectively. Our adjustment scheme thus continues to build on the advantage of deriving temperatures from spectroscopy alone, independent of reddening, while at the same time producing stellar chemical abundances that are more straightforwardly comparable to studies based on photometrically derived temperatures. Hence, our method may prove beneficial for comparing different studies in the literature as well as the many high-resolution stellar spectroscopic surveys that are or will be carried out in the next few years. Australian Research Council (Laureate Fellowship 0992131) Massachusetts Institute of Technology. Undergraduate Research Opportunities Program Australia. Department of Education (Australian Prime Minister’s Endeavour Award Research Fellowship) 2014-07-17T18:13:08Z 2014-07-17T18:13:08Z 2013-05 Article http://purl.org/eprint/type/JournalArticle 0004-637X 1538-4357 http://hdl.handle.net/1721.1/88425 Frebel, Anna, Andrew R. Casey, Heather R. Jacobson, and Qinsi Yu. “DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD.” The Astrophysical Journal 769, no. 1 (May 20, 2013): 57. https://orcid.org/0000-0001-7727-1640 https://orcid.org/0000-0002-2139-7145 en_US http://dx.doi.org/10.1088/0004-637x/769/1/57 Astrophysical Journal Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Institute of Physics Publishing arXiv |
| spellingShingle | Frebel, Anna L. Casey, Andrew R. Jacobson, Heather Yu, QinQin DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title | DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title_full | DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title_fullStr | DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title_full_unstemmed | DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title_short | DERIVING STELLAR EFFECTIVE TEMPERATURES OF METAL-POOR STARS WITH THE EXCITATION POTENTIAL METHOD |
| title_sort | deriving stellar effective temperatures of metal poor stars with the excitation potential method |
| url | http://hdl.handle.net/1721.1/88425 https://orcid.org/0000-0001-7727-1640 https://orcid.org/0000-0002-2139-7145 |
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