2010A&A...516A..46M


Query : 2010A&A...516A..46M

2010A&A...516A..46M - Astronomy and Astrophysics, volume 516, A46-46 (2010/6-2)

The Hamburg/ESO R-process enhanced star survey (HERES). V. Detailed abundance analysis of the r-process enhanced star HE 2327-5642.

MASHONKINA L., CHRISTLIEB N., BARKLEM P.S., HILL V., BEERS T.C. and VELICHKO A.

Abstract (from CDS):

We present a detailed abundance analysis of a strongly r-process enhanced giant star discovered in the HERES project, HE 2327-5642, for which [Fe/H]=-2.78, [r/Fe]=+0.99. We determined the stellar parameters and element abundances by analyzing the high-quality VLT/UVES spectra. The surface gravity was calculated from the non-local thermodynamic equilibrium (NLTE) ionization balance between FeI and FeII, and CaI and CaII. Accurate abundances for a total of 40 elements and for 23 neutron-capture elements beyond Sr and up to Th were determined in HE 2327-5642. For every chemical species, the dispersion in the single line measurements around the mean does not exceed 0.11dex. The heavy element abundance pattern of HE 2327-5642 is in excellent agreement with those previously derived for other strongly r-process enhanced stars, such as CS22892-052, CS31082-001, and HE1219-0312. Elements in the range from Ba to Hf match the scaled Solar r-process pattern very well. No firm conclusion can be drawn about the relationship between the fisrt neutron-capture peak elements, Sr to Pd, in HE 2327-5642 and the Solar r-process, due to the uncertainty in the Solar r-process. A clear distinction in Sr/Eu abundance ratios was found between the halo stars of different europium enhancement. The strongly r-process enhanced stars contain a low Sr/Eu abundance ratio at [Sr/Eu]=-0.92±0.13, while the stars with 0<[Eu/Fe]<1 and [Eu/Fe]<0 have 0.36dex and 0.93dex higher Sr/Eu values, respectively. Radioactive dating for HE 2327-5642 with the observed thorium and rare-earth element abundance pairs results in an average age of 13.3Gyr, when based on the high-entropy wind calculations, and 5.9Gyr, when using the Solar r-residuals. We propose that HE 2327-5642 is a radial-velocity variable based on our high-resolution spectra covering ∼4.3 years.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: atmospheres - stars: fundamental parameters - nuclear reactions, nucleosynthesis, abundances

VizieR on-line data: <Available at CDS (J/A+A/516/A46): table5.dat table8.dat refs.dat>

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 BPS CS 29497-0004 Pe* 00 28 06.9155612016 -26 03 04.269055032   14.76 14.07 13.583 13.116 ~ 50 0
2 BPS CS 22953-0003 Pe* 01 02 15.8723379360 -61 43 45.836012208   14.43 13.75 13.339 12.886 KIIvw 63 0
3 BPS CS 31082-0001 Pe* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 274 0
4 HE 1219-0312 Pe* 12 21 34.1430245160 -03 28 39.636260184     15.940   15.043 ~ 38 0
5 BD+17 3248 HB* 17 28 14.4690179544 +17 30 35.847574776   10.02 9.34     KIIvw 210 0
6 BPS CS 22892-0052 Pe* 22 17 01.6558764360 -16 39 27.051026544   14.03 13.20 13.06 12.19 KIIvw 432 0
7 BPS CS 29491-0069 Pe* 22 31 02.1859040712 -32 38 36.526573572   13.72 13.09 12.654 12.175 ~ 31 0
8 HD 221170 Pe* 23 29 28.8087143040 +30 25 57.849303180 9.43 8.74 7.66     G2IV 276 0
9 HE 2327-5642 Pe* 23 30 37.0896973176 -56 26 14.385030648   14.590 13.881 13.425 12.948 ~ 34 0

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2022.11.28-11:41:37

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