HE 0107−5240, a Chemically Ancient Star. I. A Detailed Abundance Analysis
- 10 March 2004
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 603 (2) , 708-728
- https://doi.org/10.1086/381237
Abstract
We report on a detailed abundance analysis of HE 0107-5240, a halo giant with [Fe/H]NLTE = -5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized Hamburg/ESO objective-prism survey. On the basis of high-resolution VLT/UVES spectra, we derive abundances for eight elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni) and upper limits for another 12 elements. A plane-parallel LTE model atmosphere has been specifically tailored for the chemical composition of HE 0107-5240. Scenarios of the origin of the abundance pattern observed in the star are discussed. We argue that HE 0107-5240 is most likely not a post-asymptotic giant branch star and that the extremely low abundances of the iron-peak and other elements are not due to selective dust depletion. The abundance pattern of HE 0107-5240 can be explained by preenrichment from a zero-metallicity Type II supernova (SN II) of 20-25 M☉, plus either self-enrichment with C and N or production of these elements in the asymptotic giant branch phase of a formerly more massive companion, which is now a white dwarf. However, significant radial velocity variations have not been detected within the 52 days covered by our moderate- and high-resolution spectra. Alternatively, the abundance pattern can be explained by enrichment of the gas cloud from which HE 0107-5240 formed by a 25 M☉ first-generation star exploding as a subluminous SN II, as proposed by Umeda & Nomoto. We discuss consequences of the existence of HE 0107-5240 for low-mass star formation in extremely metal-poor environments and for currently ongoing and future searches for the most metal-poor stars in the Galaxy.Keywords
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This publication has 82 references indexed in Scilit:
- Kinetic equilibrium of iron in the atmospheres of cool starsAstronomy & Astrophysics, 2003
- Stellar Archaeology: A Keck Pilot Program on Extremely Metal-poor Stars from the Hamburg/ESO Survey. II. Abundance AnalysisThe Astronomical Journal, 2002
- First Stars, Very Massive Black Holes, and MetalsThe Astrophysical Journal, 2002
- The Incidence of Binaries among Very Metal-poor Carbon StarsThe Astronomical Journal, 2001
- Pair‐Instability Supernovae, Gravity Waves, and Gamma‐Ray TransientsThe Astrophysical Journal, 2001
- Stellar Iron Abundances: Non‐LTE EffectsThe Astrophysical Journal, 1999
- A search for stars of very low metal abundance. IIThe Astronomical Journal, 1992
- JHKLM photometry - Standard systems, passbands, and intrinsic colorsPublications of the Astronomical Society of the Pacific, 1988
- On the nature of the dwarf carbon star G77-61The Astrophysical Journal, 1986
- Where is Population IIIThe Astrophysical Journal, 1981