Chemical analysis of the ninth magnitude carbon-enhanced metal-poor star BD+44°493

Hiroko Ito, Wako Aoki, Timothy C. Beers, Nozomu Tominaga, Satoshi Honda, Daniela Carollo

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Abstract

We present detailed chemical abundances for the bright carbon-enhanced metal-poor (CEMP) star BD+44°493, previously reported on by Ito et al. Our measurements confirm that BD+44°493 is an extremely metal-poor ([Fe/H] =-3.8) subgiant star with excesses of carbon and oxygen. No significant excesses are found for nitrogen and neutron-capture elements (the latter of which place it in the CEMP-no class of stars). Other elements that we measure exhibit abundance patterns that are typical for non-CEMP extremely metal-poor stars. No evidence for variations of radial velocity has been found for this star. These results strongly suggest that the carbon enhancement in BD+44°493 is unlikely to have been produced by a companion asymptotic giant-branch star and transferred to the presently observed star, nor by pollution of its natal molecular cloud by rapidly-rotating, massive, mega metal-poor ([Fe/H] <-6.0) stars. A more likely possibility is that this star formed from gas polluted by the elements produced in a "faint" supernova, which underwent mixing and fallback, and only ejected small amounts of elements of metals beyond the lighter elements. The Li abundance of BD+44°493 (A(Li) = log (Li/H)+12 =1.0) is lower than the Spite plateau value, as found in other metal-poor subgiants. The upper limit on Be abundance (A(Be) = log (Be/H)+12 <-1.8) is as low as those found for stars with similarly extremely-low metallicity, indicating that the progenitors of carbon- (and oxygen-) enhanced stars are not significant sources of Be, or that Be is depleted in metal-poor subgiants with effective temperatures of ∼5400 K.

Original languageEnglish
Article number33
Pages (from-to)1-17
Number of pages17
JournalAstrophysical Journal
Volume773
Issue number1
DOIs
Publication statusPublished - 10 Aug 2013

Bibliographical note

Copyright 2013 The American Astronomical Society. Firstly published in the Astrophysical journal, 773 (1), 33, 2013, published by IOP Publishing. The original publication is available at http://www.doi.org/10.1088/0004-637X/773/1/33. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Galaxy: abundances
  • stars: abundances

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