2014A&A...569A..43M


Query : 2014A&A...569A..43M

2014A&A...569A..43M - Astronomy and Astrophysics, volume 569A, 43-43 (2014/9-2)

The Hamburg/ESO R-process Enhanced Star survey (HERES). X. HE 2252-4225, one more r-process enhanced and actinide-boost halo star.

MASHONKINA L., CHRISTLIEB N. and ERIKSSON K.

Abstract (from CDS):

Studies of the r-process enhanced stars are important for understanding the nature and origin of the r-process better. We present a detailed abundance analysis of a very metal-poor giant star discovered in the HERES project, HE 2252-4225, which exhibits overabundances of the r-process elements with [r/Fe]=+0.80. We determined the stellar atmosphere parameters, Teff= 4710K, logg=1.65, and [Fe/H]=-2.63, and chemical abundances by analysing the high-quality VLT/UVES spectra. The surface gravity was calculated from the non-local thermodynamic equilibrium (NLTE) ionisation balance between FeI and FeII. Accurate abundances for a total of 38 elements, including 22 neutron-capture elements beyond Sr and up to Th, were determined in HE 2252-4225. For every chemical species, the dispersion in the single line measurements around the mean does not exceed 0.12 dex. This object is deficient in carbon, as expected for a giant star with Teff<4800K. The stellar Na-Zn abundances are well fitted by the yields of a single supernova of 14.4M. For the neutron-capture elements in the Sr-Ru, Ba-Yb, and Os-Ir regions, the abundance pattern of HE 2252-4225 is in excellent agreement with the average abundance pattern of the strongly r-process enhanced stars CS22892-052, CS31082-001, HE1219-0312, and HE1523-091. This suggests a common origin of the first, second, and third r-process peak elements in HE 2252-4225 in the classical r-process. We tested the solar r-process pattern based on the most recent s-process calculations of Bisterzo, Travaglio, Gallino, Wiescher, and Kaeppeler and found that elements in the range from Ba to Ir match it very well. No firm conclusion can be drawn about the relationship between the first neutron-capture peak elements, Sr to Ru, in HE 2252-4225 and the solar r-process, owing to the uncertainty in the solar r-process. The investigated star has an anomalously high Th/Eu abundance ratio, so that radioactive dating results in a stellar age of τ=1.5±1.5Gyr that is not expected for a very metal-poor halo star.

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/569/A43): table3.dat refs.dat>

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 BPS CS 29497-0004 Pe* 00 28 06.9155612016 -26 03 04.269055032   14.76 14.07 13.583 13.116 ~ 49 0
2 BPS CS 31082-0001 Pe* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 270 0
3 BPS CS 31079-0028 Pe* 03 01 00.6866893176 +06 16 31.808500140   13.900 13.211 12.713 12.190 ~ 25 0
4 HE 1219-0312 Pe* 12 21 34.1430245160 -03 28 39.636260184     15.940   15.043 ~ 35 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-5 800 0
6 BPS CS 30306-0132 Pe* 15 14 18.9191634456 +07 27 02.680959780   13.62 12.73 12.421 11.948 ~ 31 0
7 HE 1523-0901 Pe* 15 26 01.0697532504 -09 11 38.885639784   12.37 11.50 10.476 9.863 CEMP 68 0
8 BD+17 3248 HB* 17 28 14.4690179544 +17 30 35.847574776   10.02 9.34     KIIvw 209 0
9 BPS CS 22892-0052 Pe* 22 17 01.6558764360 -16 39 27.051026544   14.03 13.20 13.06 12.19 KIIvw 431 0
10 HE 2252-4225 Pe* 22 54 58.5673558608 -42 09 19.386504792     14.878   13.855 ~ 16 0
11 HD 221170 Pe* 23 29 28.8087143040 +30 25 57.849303180 9.43 8.74 7.66     G2IV 275 0
12 HE 2327-5642 Pe* 23 30 37.0896973176 -56 26 14.385030648   14.590 13.881 13.425 12.948 ~ 31 0
13 BPS CS 30315-0029 Pe* 23 34 26.6960486448 -26 42 14.003379828   14.56 13.64 13.092 12.518 ~ 18 0
14 LP 584-32 Pe* 23 57 18.9066974952 -00 52 47.436045024   16.366 15.636 15.141 14.673 ~ 30 0

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2022.08.12-07:50:40

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