Identification of a Group III CEMP-no Star in the Dwarf Spheroidal Galaxy Canes Venatici I
| Autor: | Young Sun Lee, Vinicius M. Placco, Devin D. Whitten, Jinmi Yoon, Timothy C. Beers, Thomas Masseron |
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| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
Milky Way Population FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences 0103 physical sciences Canes Venatici Satellite galaxy Astrophysics::Solar and Stellar Astrophysics Spectral resolution education 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics education.field_of_study Astronomy and Astrophysics Dwarf spheroidal galaxy Stars Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Halo Astrophysics::Earth and Planetary Astrophysics |
| DOI: | 10.48550/arxiv.1910.10038 |
| Popis: | CEMP-no stars, a subclass of carbon-enhanced metal-poor (CEMP) stars, are one of the most significant stellar populations in Galactic Archaeology, because they dominate the low end of the metallicity distribution function, providing information on the early star-formation and chemical-evolution history of the Milky Way and its satellite galaxies. Here we present an analysis of medium-resolution ($R \sim 1,800$) optical spectroscopy for a CEMP giant, SDSS J132755.56+333521.7, observed with the Large Binocular Telescope (LBT), one of the brightest ($g \sim 20.5$) members of the classical dwarf spheroidal galaxy, Canes Venatici I (CVn I). Many CEMP stars discovered to date have very cool effective temperatures ($T_{\mathrm{eff}}< 4500$ K), resulting in strong veiling by molecular carbon bands over their optical spectra at low/medium spectral resolution. We introduce a technique to mitigate the carbon-veiling problem to obtain reliable stellar parameters and validate this method with the LBT medium-resolution optical spectra of the ultra metal-poor ([Fe/H] = $-4.0$) CEMP-no dwarf, G 77-61, and seven additional very cool CEMP stars, which have published high-resolution spectroscopic parameters. We apply this technique to the LBT spectrum of SDSS J132755.56+333521.7. We find that this star is well-described with parameters $T_{\mathrm{eff}}=4530$ K, log $g=$ 0.7, [Fe/H] $ = -3.38$, and absolute carbon abundance $A$(C) = 7.23, indicating that it is likely the first Group III CEMP-no star identified in CVn I. The Group III identification of this star suggests that it is a member of the extremely metal-poor population in CVn I, which may have been accreted into its halo. 18 pages, 3 tables, 9 figures, accepted to the Astrophysical Journal (with minor revisions made after the referee's report) |
| Databáze: | OpenAIRE |
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