J/A+A/571/A40 Abundances in 2 extremely metal-poor stars (Spite+, 2014)
The low Sr/Ba ratio on some extremely metal-poor stars.
Spite M., Spite F., Bonifacio P., Caffau E., Francois P., Sbordone L.
<Astron. Astrophys. 571, A40 (2014)>
=2014A&A...571A..40S 2014A&A...571A..40S
ADC_Keywords: Stars, carbon ; Equivalent widths ; Abundances
Keywords: stars: abundances - stars: Population II - Galaxy: evolution -
Galaxy: halo
Abstract:
It has been noted that, in classical extremely metal-poor (EMP) stars,
the abundance ratio of two well-observed neutroncapture elements, Sr
and Ba, is always higher than [Sr/Ba]=-0.5, which is the value of
the solar r-only process; however, a handful of EMP stars have
recently been found with a very low Sr/Ba ratio.
We try to understand the origin of this anomaly by comparing the
abundance pattern of the elements in these stars and in the classical
EMP stars.
For a rigorous comparison with previous data, four stars with very low
Sr/Ba ratios were observed and analyzed in the same way as in the
First Stars Program: analysis within LTE approximation through 1D
(hydrostatic) model atmosphere, providing homogeneous abundances of
nine neutron-capture elements.
Description:
For the two low-Sr/Ba stars CS29493-090 and HE305-4520 we give, line
by line, the main line parameters and the logarithm of the abundances
for logA(H)=12.
Objects:
------------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------------
21 59 05.77 -31 16 12.1 CS 29493-090 = HE 2156-3130
03 07 02.19 -45 09 00.7 HE 0305-4520 = 2MASS J03070219-4509006
------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
linelist.dat 58 256 Line list and abundances
--------------------------------------------------------------------------------
See also:
J/A+A/403/1105 : Extremely metal-poor giants EW (Francois+, 2003)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/ApJS/155/651 : Evolution of extremely metal-poor stars (Herwig+, 2004)
J/AJ/132/137 : Extremely metal-poor carbon stars abundances (Cohen+, 2006)
J/ApJ/658/367 : Abundances of carbon stars in Galactic halo (Komiya+, 2007)
J/A+A/490/769 : Yields from extremely metal-poor stars (Campbell+, 2008)
J/A+A/501/519 : Extremely metal-poor turnoff stars abund. (Bonifacio+, 2009)
J/MNRAS/412/843 : SAGA extremely metal-poor stars (Suda+, 2011)
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
Byte-by-byte Description of file: linelist.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.3 0.1nm lambda [3743/6457] Wavelength in Angstroms
10- 13 A4 --- Ion Species identifier
15- 19 F5.2 eV EP Excitation potential of the lower level
21- 26 F6.3 [-] loggf ? Oscillator strength
27- 29 A3 --- n_loggf [hfs ] hfs means that the hyperfine structure
was taken into account
31- 35 F5.1 0.1pm EW1 ? Equivalent width in CS29493-090
36 A1 --- n_EW1 [s] s for syn (1)
38- 43 F6.3 [-] logAb1 ? Log abundance in CS29493-090
45- 49 F5.1 0.1pm EW2 ? Equivalent width in HE305-4520
50 A1 --- n_EW2 [s] s for syn (1)
52 A1 --- l_logAb2 Limit flag on logAb2
53- 58 F6.3 [-] logAb2 ? Log abundance in HE305-4520
--------------------------------------------------------------------------------
Note (1): 's' means that the abundance was obtained from a fitting of the
observed profile
--------------------------------------------------------------------------------
Acknowledgements:
Monique Spite, monique.spite(at)obspm.fr
(End) Patricia Vannier [CDS] 04-Nov-2014