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The First Stars and the Chemical Enrichment of the Universe

Title
The First Stars and the Chemical Enrichment of the Universe
Funding
ARC | Discovery Projects
Contract (GA) number
DP0342613
Start Date
2003/01/01
End Date
2005/12/31
Open Access mandate
no
Organizations
-
More information
http://purl.org/au-research/grants/arc/DP0342613

 

  • Chemical Abundance Analysis of the Extremely Metal-Poor Star HE 1300+0157

    Frebel, Anna; Norris, John E.; Aoki, Wako; Honda, Satoshi; Bessell, Michael S.; Takada-Hidai, Masahide; Beers, Timothy C.; Christlieb, Norbert (2006)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with [Fe/H]=-3.9. From a high-resolution, high-S/N Subaru/HDS spectrum we find the star to be enriched in C ([C/Fe]_1D ~ +1.4) and O ([O/Fe]_1D ~ +1.8). With the exception of these species, HE 1300+0157 exhibits an elemental abundance pattern similar to that found in many other very and extremely metal-poor stars. The Li abundance is lower than the Spite-plateau value, in agreement with expectation for its evolution...

    The new record holder for the most iron-poor star: HE 1327-2326, a dwarf or subgiant with [Fe/H]=-5.4

    Frebel, A.; Aoki, W.; Christlieb, N.; Ando, H.; Asplund, M.; Barklem, P. S.; Beers, T. C.; Eriksson, K.; Fechner, C.; Fujimoto, M. Y.; Honda, S.; Kajino, T.; Minezaki, T.; Nomoto, K.; Norris, J. E.;... (2005)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We describe the discovery of HE 1327-2326, a dwarf or subgiant with [Fe/H]}=-5.4. The star was found in a sample of bright metal-poor stars selected from the Hamburg/ESO survey. Its abundance pattern is characterized by very high C and N abundances. The detection of Sr which is overabundant by a factor of 10 as compared to iron and the Sun, suggests that neutron-capture elements had already been produced in the very early Galaxy. A puzzling Li depletion is observed in this unevolved star whic...

    The Metallicity Distribution Function of the Halo of the Milky Way

    Beers, Timothy C.; Christlieb, Norbert; Norris, John E.; Bessell, Michael S.; Wilhelm, Ronald; Prieto, Carlos Allende; Yanny, Brian; Rockosi, Constance; Newberg, Heidi Jo; Rossi, Silvia; Lee, Young Sun (2005)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We report on the distribution of metallicities, [Fe/H], for very metal-poor stars in the halo of the Galaxy. Although the primary information on the nature of the Metallicity Distribution Function (MDF) is obtained from the two major recent surveys for metal-poor stars, the HK survey of Beers and collaborators, and the Hamburg/ESO Survey of Christlieb and collaborators, we also discuss the MDF derived from the publicly available database of stellar spectra and photometry contained in the thir...

    Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I

    Beers, Timothy C.; Flynn, Chris; Rossi, Silvia; Sommer-Larsen, Jesper; Wilhelm, Ronald; Marsteller, Brian; Lee, YoungSun; De Lee, Nathan; Krugler, Julie; Deliyannis, Constantine P.; Zickgraf, Franz-Josef; Holmberg, Johan; Onehag, Anna; Eriksson, Anders; Terndrup, Donald M.;... (2006)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We report broadband UBV and/or BVRI CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the ca...

    Carbon-Enhanced Metal-Poor Stars. Osmium and Iridium Abundances in the Neutron-Capture-Enhanced Subgiants CS31062-050 and LP625-44

    Aoki, Wako; Bisterzo, Sara; Gallino, Roberto; Beers, Timothy C.; Norris, John E.; Ryan, Sean G.; Tsangarides, Stelios (2006)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We have investigated the abundances of heavy neutron-capture elements, including osmium (Os) and iridium (Ir), in the two Carbon-Enhanced Metal-Poor (CEMP) subgiants CS31062-050 and LP625-44. CS31062-050 is known to be a so-called CEMP-r/s star, which exhibits large excesses of s-process elements such as barium (Ba) and lead (Pb), as well as a significant enhancement of europium (Eu) that cannot be explained by conventional s-process production in Asymptotic Giant Branch star models. Our anal...

    Oxygen Overabundance in the Extremely Iron-Poor Star CS29498-043

    Aoki, Wako; Norris, John E.; Ryan, Sean G.; Beers, Timothy C.; Christlieb, Norbert; Tsangarides, Stelios; Ando, Hiroyasu (2004)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    An abundance analysis for the carbon-enhanced, extremely iron-poor ([Fe/H] -3.5) star CS29498-043 has been obtained using new high-resolution, high signal-to-noise spectra from the Subaru Telescope. The [O I] forbidden line at 6300A and the O I triplet feature at 7771-7776A are both clearly detected. The overabundance of oxygen is significant ([O/Fe]>2). In addition, Na, Co, and Ni abundances have been newly measured. The abundance pattern from C to Ni of this object is quite similar to that ...

    The evolution of the C/O ratio in metal-poor halo stars

    Akerman, Chris J.; Carigi, Leticia; Nissen, Poul E.; Pettini, Max; Asplund, Martin (2003)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We report new measurements of carbon and oxygen abundances in 34 F and G dwarf and subgiant stars belonging to the halo population and spanning a range of metallicity from [Fe/H] = -0.7 to -3.2 . The survey is based on observations of four permitted lines of C I near 9100 A, and the O I 7774 A triplet, all recorded at high signal-to-noise ratios with the UVES echelle spectrograph on the ESO VLT. The line equivalent widths were analysed with the 1D, LTE, MARCS model atmosphere code to deduce C...

    The Origins of Two Classes of Carbon-Enhanced, Metal-Poor Stars

    Ryan, S. G.; Aoki, W.; Norris, J. E.; Beers, T. C. (2005)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    We have compiled composition, luminosity, and binarity information for carbon-enhanced, metal-poor (CEMP) stars reported by recent studies. We divided the CEMP star sample into two classes, having high and low abundances, respectively, of the s-process elements, and consider the abundances of several isotopes, in particular 12C, 13C, and 14N, as well as the likely evolutionary stages of each star. Despite the fact that objects in both groups were selected from the same surveys (primarily the ...

    The Oxygen Abundance of HE 1327-2326

    Frebel, Anna; Christlieb, Norbert; Norris, John E.; Aoki, Wako; Asplund, Martin (2005)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    From a newly obtained VLT/UVES spectrum we have determined the oxygen abundance of HE 1327-2326, the most iron-poor star known to date. UV-OH lines yield a 1D LTE abundance of [O/Fe]_OH = 3.7 (subgiant case) and [O/Fe]_OH = 3.4 (dwarf case). Using a correction of -1.0 dex to account for 3D effects on OH line formation, the abundances are lowered to [O/Fe] = 2.8 and [O/Fe] = 2.5, respectively, which we adopt. Without 3D corrections, the UV-OH based abundance would be in disagreement with the u...

    Spectroscopic Studies of Extremely Metal-Poor Stars with the Subaru High Dispersion Spectrograph. IV. The alpha-Element-Enhanced Metal-Poor Star BS16934-002

    Aoki, Wako; Honda, Satoshi; Beers, Timothy C.; Takada-Hidai, Masahide; Iwamoto, Nobuyuki; Tominaga, Nozomu; Umeda, Hideyuki; Nomoto, Ken'ichi; Norris, John E.; Ryan, Sean G. (2007)
    Projects: ARC | The First Stars and the Chemical Enrichment of the Universe (DP0342613)
    A detailed elemental abundance analysis has been carried out for the very metal-poor ([Fe/H]=-2.7) star BS16934-002, which was identified in our previous work as a star exhibiting large overabundances of Mg and Sc. A comparison of the abundance pattern of this star with that of the well-studied metal-poor star HD122563 indicates excesses of O, Na, Mg, Al, and Sc in BS16934-002. Of particular interest, no excess of C or N is found in this object, in contrast to CS22949-037 and CS29498-043, two...
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