HUBBLE SPACE TELESCOPE NEAR-ULTRAVIOLET SPECTROSCOPY OF THE BRIGHT CEMP-NO STAR BD+44°493
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Placco-2014-Hubble Space Telesco.pdf
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Author(s)
Placco, Vinicius M.
Beers, Timothy C.
Roederer, Ian U.
Cowan, John J.
Filler, Dan
Ivans, Inese I.
Lawler, James E.
Schatz, Hendrik
Sneden, Christopher
Sobeck, Jennifer S.
Date Issued
June 2014
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Placco, Vinicius M., Timothy C. Beers, Ian U. Roederer, John J. Cowan, Anna Frebel, Dan Filler, Inese I. Ivans, et al. “HUBBLE SPACE TELESCOPE NEAR-ULTRAVIOLET SPECTROSCOPY OF THE BRIGHT CEMP-NO STAR BD+44°493.” The Astrophysical Journal 790, no. 1 (June 30, 2014): 34. © 2014 The American Astronomical Society
Version
Final published version
Abstract
We present an elemental-abundance analysis, in the near-ultraviolet (NUV) spectral range, for the extremely metal-poor star BD+44°493 a ninth magnitude subgiant with [Fe/H] =–3.8 and enhanced carbon, based on data acquired with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. This star is the brightest example of a class of objects that, unlike the great majority of carbon-enhanced metal-poor (CEMP) stars, does not exhibit over-abundances of heavy neutron-capture elements (CEMP-no). In this paper, we validate the abundance determinations for a number of species that were previously studied in the optical region, and obtain strong upper limits for beryllium and boron, as well as for neutron-capture elements from zirconium to platinum, many of which are not accessible from ground-based spectra. The boron upper limit we obtain for BD+44°493, log ε (B) <–0.70, the first such measurement for a CEMP star, is the lowest yet found for very and extremely metal-poor stars. In addition, we obtain even lower upper limits on the abundances of beryllium, log ε (Be) <–2.3, and lead, log ε (Pb) <–0.23 ([Pb/Fe] <+1.90), than those reported by previous analyses in the optical range. Taken together with the previously measured low abundance of lithium, the very low upper limits on Be and B suggest that BD+44°493 was formed at a very early time, and that it could well be a bona-fide second-generation star. Finally, the Pb upper limit strengthens the argument for non-s-process production of the heavy-element abundance patterns in CEMP-no stars.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1088/0004-637X/790/1/34
