2009A&A...503..533S


Query : 2009A&A...503..533S

2009A&A...503..533S - Astronomy and Astrophysics, volume 503, 533-540 (2009/8-4)

Statistical equilibrium of silicon in the atmospheres of metal-poor stars.

SHI J.R., GEHREN T., MASHONKINA L. and ZHAO G.

Abstract (from CDS):

The statistical equilibrium of neutral and ionized silicon in the atmospheres of metal-poor stars is discussed. Non-local thermodynamic equilibrium effects (NLTE) are investigated and the silicon abundances in metal-poor stars determined. We have used high resolution, high signal to noise ratio spectra from the UVES spectragraph at the ESO VLT telescope. Line formation calculations of SiI and SiII in the atmospheres of metal-poor stars are presented for atomic models of silicon including 174 terms and 1132 line transitions. Recent improved calculations of SiI and SiII photoionization cross-sections are taken into account, and the influence of the free-free quasi-molecular absorption in the Lyα wing is investigated by comparing theoretical and observed fluxes of metal-poor stars. All abundance results are derived from LTE and NLTE statistical equilibrium calculations and spectrum synthesis methods. It is found that the extreme ultraviolet radiation is very important for metal-poor stars, especially for the high temperature, very metal-poor stars. The radiative bound-free cross-sections also play a very important role for these stars. NLTE effects for Si are found to be important for metal-poor stars, in particular for warm metal-poor stars. It is found that these effects depend on the temperature. For warm metal-poor stars, the NLTE abundance correction reaches ∼0.2dex relative to standard LTE calculations. Our results indicate that Si is overabundant for metal-poor stars.

Abstract Copyright:

Journal keyword(s): line: formation - line: profiles - stars: abundances - stars: late-type - Galaxy: evolution

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 HD 29907 SB* 04 38 22.3989572020 -65 24 57.594232229   10.52 9.91     F8V 98 0
2 HD 31128 PM* 04 52 09.9097086888 -27 03 50.940147636   9.55 9.14     F3/5Vw 141 0
3 HD 34328 Pe* 05 13 05.2760918664 -59 38 44.265435029   9.95 9.5     G0wA8V 130 0
4 HD 59392 Pe* 07 28 03.2212916981 -38 00 41.278587469   10.17 9.7     F0V 92 0
5 HD 74000 Pe* 08 40 50.8036114756 -16 20 42.516208237 9.84 10.09 9.66     F2 270 0
6 HD 84937 Pe* 09 48 56.0992891997 +13 44 39.326709913 8.49 8.68 8.32 7.97 7.70 F8Vm-5 795 0
7 HD 298986 PM* 10 17 14.8774744591 -52 29 18.694800089   10.46 10.03   9.48 F5 86 0
8 HD 97320 Pe* 11 11 00.7344001848 -65 25 37.745815656   9.769 9.269     F3V 145 0
9 HD 102200 Pe* 11 45 34.2345453384 -46 03 46.386995400   9.13 8.76     F2V 114 0
10 BD-04 3208 PM* 12 07 15.0721580835 -05 44 01.612773628   10.40 9.99     A7 147 0
11 Wolf 1492 Pe* 13 40 02.4921849768 -00 02 18.750053436 11.601 11.832 11.451 11.184 10.892 sdF0: 284 0
12 HD 122196 PM* 14 01 02.1249985961 -38 03 03.313496920   9.19 8.75     F0(V)w 118 0
13 HD 122563 Pe* 14 02 31.8455084952 +09 41 09.944391876 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 854 0
14 HD 140283 Pe* 15 43 03.0971190219 -10 56 00.595693188 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 938 0
15 * alf Lyr dS* 18 36 56.33635 +38 47 01.2802 0.03 0.03 0.03 0.07 0.10 A0Va 2687 1

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