J/ApJ/812/109 HST & Keck spectroscopy of bright CEMP-s stars (Placco+, 2015)
Hubble Space Telescope near-ultraviolet spectroscopy of bright CEMP-s stars.
Placco V.M., Beers T.C., Ivans I.I., Filler D., Imig J.A., Roederer I.U.,
Abate C., Hansen T., Cowan J.J., Frebel A., Lawler J.E., Schatz H.,
Sneden C., Sobeck J.S., Aoki W., Smith V.V., Bolte M.
<Astrophys. J., 812, 109 (2015)>
=2015ApJ...812..109P 2015ApJ...812..109P (SIMBAD/NED BibCode)
ADC_Keywords: Abundances ; Stars, halo ; Stars, metal-deficient ;
Spectra, ultraviolet ; Spectroscopy
Keywords: Galaxy: halo; stars: abundances; stars: atmospheres;
stars: individual: (HD 196944, HD 201626);
techniques: imaging spectroscopic
Abstract:
We present an elemental-abundance analysis, in the near-ultraviolet
(NUV) spectral range, for the bright carbon-enhanced metal-poor (CEMP)
stars HD 196944 (V=8.40, [Fe/H]=-2.41) and HD 201626 (V=8.16,
[Fe/H]=-1.51), based on data acquired with the Space Telescope Imaging
Spectrograph (STIS) on the Hubble Space Telescope. Both of these stars
belong to the sub-class CEMP-s, and exhibit clear over-abundances of
heavy elements associated with production by the slow neutron-capture
process. HD 196944 has been well-studied in the optical region, but we
add abundance results for six species (Ge, Nb, Mo, Lu, Pt, and Au)
that are only accessible in the NUV. In addition, we provide the first
determination of its orbital period, P=1325 days. HD 201626 has only a
limited number of abundance results based on previous optical work
--here we add five new species from the NUV, including Pb. We compare
these results with models of binary-system evolution and s-process
element production in stars on the asymptotic giant branch, with the
goal of explaining their origin and evolution. Our best-fitting models
for HD 196944 (M1,i=0.9M☉, M2,i=0.86M☉, for
[Fe/H]=-2.2), and HD 201626 (M1,i=0.9M☉, M2,i=0.76M☉
for [Fe/H]=-2.2; M1,i=1.6M☉, M2,i=0.59M☉ for
[Fe/H]=-1.5) are consistent with the current accepted scenario for the
formation of CEMP-s stars.
Description:
We studied high-resolution spectra of HD 196944 and HD 201626 from the
NUV to optical wavelengths, employing data gathered with the HST/STIS
(Program GO-12554; 2280-3070Å with R∼30000) taken on 2012 April 29
(HD 201626) and 2012 September 22 (HD 196944) and Keck/HIRES
spectrographs gathered over two observing runs: 2004 October 1
(program ID: C23H and PI: I. Ivans; 2990-5850Å with R=48000) and
2007 June 5 and 7 (program ID: U100Hb and PI: M. Bolte; 3725-7990Å
with R=103000).
Objects:
--------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
--------------------------------------------------------------
20 40 46.09 -06 47 50.7 HD196944 = HIP 102042 (P=1325)
21 09 59.27 +26 36 54.9 HD201626 = HIP 104486 (P=1465)
--------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 41 525 Derived optical abundance estimates
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/581/A22 : 67 CEMP-s stars model analysis (Abate+, 2015)
J/ApJS/216/2 : MnI hyperfine lines in 1.4-1.8um (H) band (Andersson+, 2015)
J/ApJS/215/20 : Vanadium log(gf) & transition probabilities (Lawler+, 2014)
J/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
J/ApJS/214/18 : VII log(gf) values, and V abundance in HD 84937 (Wood+ 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/MNRAS/440/1095 : Chemical analysis of CH stars (Karinkuzhi+, 2014)
J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/ApJ/762/26 : Most metal-poor stars II. Galactic halo stars (Yong+, 2013)
J/A+A/548/A34 : Carbon-enhanced metal-poor stars abundances (Allen+, 2012)
J/MNRAS/427/343 : Infrared excesses of Hipparcos stars (McDonald+, 2012)
J/MNRAS/418/284 : s-process in low-metallicity stars. II. (Bisterzo+, 2011)
J/MNRAS/412/843 : SAGA extremely metal-poor stars (Suda+, 2011)
J/ApJS/194/35 : Atomic transition probabilities of Mn (Den Hartog+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
J/A+A/509/A93 : Carbon-enhanced metal-poor stars (Masseron+, 2010)
J/ApJ/724/975 : Abundances of metal-poor stars (Roederer+, 2010)
J/MNRAS/404/1529 : s-process in low-metallicity stars (Bisterzo+, 2010)
J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010)
J/AJ/139/1051 : Carbon-enhanced metal-poor stars in the MW (Placco+, 2010)
J/ApJ/658/1203 : Nitrogen-enhanced metal-poor stars (Johnson+, 2007)
J/ApJ/658/367 : Abundances of carbon stars in Galactic halo (Komiya+, 2007)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJS/169/120 : Transition probabilities for HfII and Hf (Lawler+, 2007)
J/A+A/402/343 : [OI] lines in F-K dwarfs/giants (Takeda, 2003)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Type Analysis type (1)
4- 9 A6 --- Ion Ion or molecule identifier
11- 17 F7.2 0.1nm lambda [3360/7970.4] Wavelength in Angstroms
19- 22 F4.2 eV chi [0/8.6]? Excitation potential
24- 28 F5.2 [-] log(gf) [-9.8/0.7]? Log oscillator strength
30 A1 --- l_HD196944 Limit flag on HD196944
31- 35 F5.2 [-] HD196944 [-2/7.1]? Log number abundance of
Ion in HD 196944
37- 41 F5.2 [-] HD201626 [-0.04/8.6]? Log number abundance of
Ion in HD 201626
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Note (1): Analysis type as follows:
EW = Equivalent width analysis.
SS = Spectral synthesis analysis.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Feb-2016