2009A&A...504..511H


Query : 2009A&A...504..511H

2009A&A...504..511H - Astronomy and Astrophysics, volume 504, 511-524 (2009/9-3)

The Hamburg/ESO R-process enhanced star survey (HERES). IV. Detailed abundance analysis and age dating of the strongly r-process enhanced stars CS 29491-069 and He 1219-0312.

HAYEK W., WIESENDAHL U., CHRISTLIEB N., ERIKSSON K., KORN A.J., BARKLEM P.S., HILL V., BEERS T.C., FAROUQI K., PFEIFFER B. and KRATZ K.-L.

Abstract (from CDS):

We report on a detailed abundance analysis of two strongly r-process enhanced, very metal-poor stars newly discovered in the HERES project, CS 29491-069 ([Fe/H]=-2.51, [r/Fe]=+1.1) and HE 1219-0312 ([Fe/H]=-2.96, [r/Fe]=+1.5). The analysis is based on high-quality VLT/UVES spectra and MARCS model atmospheres. We detect lines of 15 heavy elements in the spectrum of CS 29491-069, and 18 in HE 1219-0312; in both cases including the ThII 4019Å line. The heavy-element abundance patterns of these two stars are mostly well-matched to scaled solar residual abundances not formed by the s-process. We also compare the observed pattern with recent high-entropy wind (HEW) calculations, which assume core-collapse supernovae of massive stars as the astrophysical environment for the r-process, and find good agreement for most lanthanides. The abundance ratios of the lighter elements strontium, yttrium, and zirconium, which are presumably not formed by the main r-process, are reproduced well by the model. Radioactive dating for CS 29491-069 with the observed thorium and rare-earth element abundance pairs results in an average age of 9.5Gyr, when based on solar r-process residuals, and 17.6Gyr, when using HEW model predictions. Chronometry seems to fail in the case of HE 1219-0312, resulting in a negative age due to its high thorium abundance. HE 1219-0312 could therefore exhibit an overabundance of the heaviest elements, which is sometimes called an ``actinide boost''.

Abstract Copyright:

Journal keyword(s): stars: abundances - nuclear reactions, nucleosynthesis, abundances - Galaxy: halo - Galaxy: abundances - Galaxy: evolution

Simbad objects: 10

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Number of rows : 10
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 ~ 51 0
2 BPS CS 22183-0031 Pe* 01 09 05.0900915136 -04 43 21.343580436   14.24 13.62 13.178 12.724 ~ 43 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 276 0
4 HE 1219-0312 Pe* 12 21 34.1430245160 -03 28 39.636260184     15.940   15.043 ~ 38 0
5 HD 122563 Pe* 14 02 31.8455084952 +09 41 09.944391876 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 811 0
6 BPS CS 30306-0132 Pe* 15 14 18.9191634456 +07 27 02.680959780   13.62 12.73 12.421 11.948 ~ 33 0
7 HE 1523-0901 Pe* 15 26 01.0697532504 -09 11 38.885639784   12.37 11.50 10.476 9.863 CEMP 71 0
8 BD+17 3248 HB* 17 28 14.4690179544 +17 30 35.847574776   10.02 9.34     KIIvw 212 0
9 BPS CS 22892-0052 Pe* 22 17 01.6558764360 -16 39 27.051026544   14.03 13.20 13.06 12.19 KIIvw 433 0
10 BPS CS 29491-0069 Pe* 22 31 02.1859040712 -32 38 36.526573572   13.72 13.09 12.654 12.175 ~ 31 0

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2023.01.27-22:41:26

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