Hubble Space Telescope Near-Ultraviolet Spectroscopy Of The Bright CEMP-No Star BD+44 Degrees 493

Placco, Vinicius M.
Beers, Timothy C.
Roederer, Ian U.
Cowan, John J.
Frebel, Anna
Filler, Dan
Ivans, Inese I.
Lawler, James E.
Schatz, Hendrik
Sneden, Christopher
Journal Title
Journal ISSN
Volume Title

We present an elemental-abundance analysis, in the near-ultraviolet (NUV) spectral range, for the extremely metal-poor star BD+44 degrees 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 degrees 493, log is an element of (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 is an element of (Be) < -2.3, and lead, log is an element of (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 degrees 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.

Placco, Vinicius, Timothy Beers, Ian Roederer, John 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." arXiv preprint arXiv:1406.0538 (Jul., 2014).