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HE 1327-2326, AN UN...
HE 1327-2326, AN UNEVOLVED STAR WITH [Fe/H] <-5.0. III. DOES ITS ATMOSPHERE REFLECT ITS NATAL COMPOSITION?
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- Korn, A. J. (författare)
- Uppsala universitet,Institutionen för fysik och astronomi
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Richard, O (författare)
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Mashonkina, L (författare)
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Bessell, S (författare)
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Frebel, A (författare)
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Aoki, W (författare)
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(creator_code:org_t)
- 2009
- 2009
- Engelska.
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 698:1, s. 410-416
- Relaterad länk:
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Based on spectroscopic constraints derived from nonlocal thermodynamic equilibrium line formation, we explore the likely range of stellar parameters (T-eff and log g) for the hyper-metal-poor (HMP) star HE 1327-2326. Combining the constraints from Balmer line profiles and the Ca I/II ionization equilibrium, a subgiant stage of evolution is indicated. This result is further supported by spectrophotometric observations of the Balmer jump. If a higher T-eff value was used (as favored by some photometric calibrations), the spectroscopic analysis would indicate a turnoff-point stage of evolution. Using a stellar-structure code that treats the effects of atomic diffusion throughout the star in detail, we evolve a low-mass model star to reach the Hertzsprung-Russell-diagram position of HE 1327-2326 after roughly 13 Gyr. While the surface abundances are modified significantly (by more than 1 dex for the case of uninhibited diffusion), such corrections cannot resolve the discrepancy between the abundance inferred from the nondetection of the Li I resonance line at 6707 angstrom and the Wilkinson Microwave Anisotropy Probe based primordial lithium abundance. As there are numerous processes that can destroy lithium, any cosmological interpretation of a lower-than-expected lithium abundance at the lowest metallicities will have to await sample sizes of unevolved HMP stars that are 1 order of magnitude larger. The situation remains equally inconclusive concerning atomic-diffusion corrections. Here, attempts have to be made to better constrain internal mixing processes, both observationally and by means of sophisticated modeling. With constraints on additional mixing processes taken from a recent globular-cluster study, the likeliest scenario is that HE 1327-2326's surface abundances have undergone mild depletion (of order 0.2 dex).
Ämnesord
- NATURVETENSKAP -- Fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences (hsv//eng)
Nyckelord
- diffusion
- stars: abundances
- stars: evolution
- stars: fundamental parameters
- stars: individual (HE 1327-2326)
- stars: Population II
- Physics
- Fysik
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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