J/A+A/569/A43 HE 2252-4225 abundance analysis (Mashonkina+, 2014)
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., Eriksson K.
<Astron. Astrophys. 569, A43 (2014)>
=2014A&A...569A..43M 2014A&A...569A..43M
ADC_Keywords: Stars, giant ; Stars, metal-deficient ; Spectroscopy ;
Abundances ; Line Profiles ; Models, atmosphere
Keywords: stars: abundances - stars: atmospheres -
stars: fundamental parameters -
nuclear reactions, nucleosynthesis, abundances
Abstract:
Studies of the r-process enhanced stars are important for better
understanding the nature and origin of the r-process.
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 0.12dex. 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 CS 22892-052,
CS 31082-001, HE 1219-0312, and HE 1523-091. 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 Kappeler 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, due 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.
Description:
HE 2252-4225 was identified as a candidate metal-poor star in the
Hamburg/ESO Survey (HES), and it was included in the target list of
the Hamburg/ESO R-process-Enhanced Star survey (HERES, Christlieb et
al., Paper I, 2004A&A...428.1027C 2004A&A...428.1027C). Stellar parameters,
Teff=4708±100K, logg=1.53±0.24, and [Fe/H]=-2.83±0.12, were first
determined by Barklem et al. (Paper II. Cat. J/A+A/439/129) based on
automated abundance analysis of high-resolution "snapshot" spectra.
The photometry was taken from Beers et al. (2007, Cat.
J/ApJS/168/128). High-quality spectra of this star was acquired during
May-September 2005 with the VLT and UVES in dichroic mode. The
BLUE390+RED580 (9h total integration time) and BLUE437+RED860 (10h)
standard settings were employed to ensure a wide wavelength coverage.
Objects:
------------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------------
22 54 58.6 -42 09 19 HE 2252-4225 = 2MASS J22545856-4209193
------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 108 273 Line data and abundances from an analysis of
HE 2252-4225
refs.dat 234 70 References
--------------------------------------------------------------------------------
See also:
J/ApJS/168/128 : UBVRcIc photometry of FHB and metal-poor stars (Beers+, 2007)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/A+A/516/A46 : HE 2327-5642 abundance analysis (Mashonkina+, 2010)
J/A+A/528/A92 : HERES VI. Galactic chemical evolution of Si & C (Zhang+, 2011)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Z [3/90] Element atomic number
5- 9 A5 --- El Atom/molecule and ionization stage
11- 17 F7.2 0.1nm lambda [3404/6708] Line wavelength λ
20- 26 F7.2 0.1nm lambda2 ? Second wavelength when interval
28- 31 F4.2 eV Eexc ? Excitation energy χ
33- 37 F5.2 [-] loggf ? Adopted gf-value
39- 43 A5 --- r_loggf Reference for loggf, in refs.dat file
47- 50 F4.2 [-] epsSun Solar photosphere abundance
(scale logε(H)=12)
52 A1 --- l_eps Limit flag on eps
53- 57 F5.2 [-] eps ? LTE abundance of El (logε(H)=12)
59- 63 F5.2 [-] epsN ? NLTE abundance of El (logε(H)=12)
67- 71 F5.2 [-] [X/Fe] ? Abundance relative to iron
73- 77 F5.1 0.1pm EW ? Equivalent width (mÅ)
78- 80 A3 --- n_EW [Syn ] from synthetic spectrum
82- 87 F6.3 [rad/s/cm3] G6/NH ? van der Waals damping constant log(G6/NH)
at 10000K log(Γ6/NH)
89- 91 A3 --- Mod1 Model used (1)
94- 98 A5 --- r_Mod1 Reference for Model1, in refs.dat file
100-102 A3 --- Mod2 Second model used (1)
104-108 A5 --- r_Mod2 Reference for Model2, in refs.dat file
--------------------------------------------------------------------------------
Note (1): Models as follows:
G6 = Gamma6 (Γ6)
HFS = hyper-fine splitting
IS = isotopic structure
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ref Reference code
7- 25 A19 --- BibCode BibCode
27- 55 A29 --- Aut Author's name
56-234 A179 --- Com Comments
--------------------------------------------------------------------------------
Acknowledgements:
Lyudmila Mashonkina, lima(at)inasan.ru
References:
Christlieb et al., Paper I 2004A&A...428.1027C 2004A&A...428.1027C
Barklem et al., Paper II 2005A&A...439..129B 2005A&A...439..129B, Cat. J/A+A/439/129
Jonsell et al., Paper III 2006A&A...451..651J 2006A&A...451..651J
Hayek et al., Paper IV 2009A&A...504..511H 2009A&A...504..511H
Mashonkina et al., Paper V 2010A&A...516A..46M 2010A&A...516A..46M, Cat. J/A+A/516/A46
Zhang et al., Paper VI 2011A&A...528A..92Z 2011A&A...528A..92Z, Cat. J/A+A/528/A92
Ren et al., Paper VII 2012A&A...537A.118R 2012A&A...537A.118R
Cui et al., Paper VIII 2013A&A...558A..36C 2013A&A...558A..36C
Mashonkina & Christlieb, Paper IX 2014A&A...565A.123M 2014A&A...565A.123M
(End) Patricia Vannier [CDS] 21-Jul-2014