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Title: The Chemical Composition of Extreme-velocity Stars*

Abstract

Abstract Little is known about the origin of the fastest stars in the Galaxy. Our understanding of the chemical evolution history of the Milky Way and surrounding dwarf galaxies allows us to use the chemical composition of a star to investigate its origin and to say whether it was formed in situ or was accreted. However, the fastest stars, the hypervelocity stars, are young and massive and their chemical composition has not yet been analyzed. Though it is difficult to analyze the chemical composition of a massive young star, we are well versed in the analysis of late-type stars. We have used high-resolution ARCES/3.5 m Apache Point Observatory, MIKE/Magellan spectra to study the chemical details of 15 late-type hypervelocity star candidates. With Gaia EDR3 astrometry and spectroscopically determined radial velocities we found total velocities with a range of 274–520 km s −1 and mean value of 381 km s −1 . Therefore, our sample stars are not fast enough to be classified as hypervelocity stars, and are what is known as extreme-velocity stars. Our sample has a wide iron abundance range of −2.5 ≤ [Fe/H] ≤ −0.9. Their chemistry indicates that at least 50% of them are accreted extragalactic stars,more » with iron-peak elements consistent with prior enrichment by sub-Chandrasekhar mass Type Ia supernovae. Without indication of binary companions, their chemical abundances and orbital parameters indicate that they are the accelerated tidal debris of disrupted dwarf galaxies.« less

Authors:
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Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1866632
Grant/Contract Number:  
NA0003843
Resource Type:
Published Article
Journal Name:
The Astronomical Journal
Additional Journal Information:
Journal Name: The Astronomical Journal Journal Volume: 163 Journal Issue: 6; Journal ID: ISSN 0004-6256
Publisher:
American Astronomical Society
Country of Publication:
United States
Language:
English

Citation Formats

Reggiani, Henrique, Ji, Alexander P., Schlaufman, Kevin C., Frebel, Anna, Necib, Lina, Nelson, Tyler, Hawkins, Keith, and Galarza, Jhon Yana. The Chemical Composition of Extreme-velocity Stars* †. United States: N. p., 2022. Web. doi:10.3847/1538-3881/ac62d9.
Reggiani, Henrique, Ji, Alexander P., Schlaufman, Kevin C., Frebel, Anna, Necib, Lina, Nelson, Tyler, Hawkins, Keith, & Galarza, Jhon Yana. The Chemical Composition of Extreme-velocity Stars* †. United States. https://doi.org/10.3847/1538-3881/ac62d9
Reggiani, Henrique, Ji, Alexander P., Schlaufman, Kevin C., Frebel, Anna, Necib, Lina, Nelson, Tyler, Hawkins, Keith, and Galarza, Jhon Yana. Fri . "The Chemical Composition of Extreme-velocity Stars* †". United States. https://doi.org/10.3847/1538-3881/ac62d9.
@article{osti_1866632,
title = {The Chemical Composition of Extreme-velocity Stars* †},
author = {Reggiani, Henrique and Ji, Alexander P. and Schlaufman, Kevin C. and Frebel, Anna and Necib, Lina and Nelson, Tyler and Hawkins, Keith and Galarza, Jhon Yana},
abstractNote = {Abstract Little is known about the origin of the fastest stars in the Galaxy. Our understanding of the chemical evolution history of the Milky Way and surrounding dwarf galaxies allows us to use the chemical composition of a star to investigate its origin and to say whether it was formed in situ or was accreted. However, the fastest stars, the hypervelocity stars, are young and massive and their chemical composition has not yet been analyzed. Though it is difficult to analyze the chemical composition of a massive young star, we are well versed in the analysis of late-type stars. We have used high-resolution ARCES/3.5 m Apache Point Observatory, MIKE/Magellan spectra to study the chemical details of 15 late-type hypervelocity star candidates. With Gaia EDR3 astrometry and spectroscopically determined radial velocities we found total velocities with a range of 274–520 km s −1 and mean value of 381 km s −1 . Therefore, our sample stars are not fast enough to be classified as hypervelocity stars, and are what is known as extreme-velocity stars. Our sample has a wide iron abundance range of −2.5 ≤ [Fe/H] ≤ −0.9. Their chemistry indicates that at least 50% of them are accreted extragalactic stars, with iron-peak elements consistent with prior enrichment by sub-Chandrasekhar mass Type Ia supernovae. Without indication of binary companions, their chemical abundances and orbital parameters indicate that they are the accelerated tidal debris of disrupted dwarf galaxies.},
doi = {10.3847/1538-3881/ac62d9},
journal = {The Astronomical Journal},
number = 6,
volume = 163,
place = {United States},
year = {2022},
month = {5}
}

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