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.
Bibliographical noteCopyright 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.
- Galaxy: abundances
- stars: abundances