J/A+A/674/A180 Abundances of 6 Carina dSph CEMP stars (Hansen+, 2023)
Evidence for multiple nucleosynthetic processes from carbon-enhanced metal-poor
stars in the Carina dwarf spheroidal galaxy.
Hansen T.T., Simon J.D., Li T.S., Frebel A., Thompson I., Shectman S.
<Astron. Astrophys. 674, A180 (2023)>
=2023A&A...674A.180H 2023A&A...674A.180H (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, metal-deficient ; Abundances ;
Equivalent widths ; Optical
Keywords: stars: abundances - galaxies: dwarf - Galaxy: halo
Abstract:
Carbon Enhanced Metal-Poor (CEMP) stars ([C/Fe]>0.7) are known to
exist in large numbers at low metallicity in the Milky Way halo and
are important tracers of early Galactic chemical evolution. However,
very few such stars have been identified in the classical dwarf
spheroidal (dSph) galaxies, and detailed abundances, including
neutron-capture element abundances, have only been reported for 13
stars.
We aim to derive detailed abundances of six CEMP stars identified in
the Carina dSph and compare the abundances to CEMP stars in other dSph
galaxies and the Milky Way halo. This is the largest sample of CEMP
stars in a dSph galaxy analysed to date. Methods. 1D LTE elemental
abundances are derived via equivalent width and spectral synthesis
using high-resolution spectra of the six stars obtained with the MIKE
spectrograph at Las Campanas Observatory.
Abundances or upper limits are derived for up to 27 elements from C to
Os in the six stars. The analysis reveals one of the stars to be a
CEMP-no star with very low neutron-capture element abundances. In
contrast, the other five stars all show enhancements in
neutron-capture elements in addition to their carbon enhancement,
classifying them as CEMP-s and -r/s stars. The six stars have similar
α and iron-peak element abundances as other stars in Carina,
except for the CEMP-no star, which shows enhancement in Na, Mg, and
Si. We explore the absolute carbon abundances (A(C)) of CEMP stars in
dSph galaxies and find similar behaviour as is seen for Milky Way halo
CEMP stars, but highlight that CEMP-r/s stars primarily have very high
A(C) values. We also compare the neutron-capture element abundances of
the CEMP-r/s stars in our sample to recent i-process yields, which
provide a good match to the derived abundances.
Description:
Out of a total of 25 Carina stars observed with MagE, eight exhibited
strong C-H features, and we obtained high-resolution spectroscopy of
six of those with the MIKE spectrograph at the Magellan/Clay telescope
over two runs in 2016 December and 2019 April.
We present detailed abundances for six CEMP stars in the Carina
dSph galaxy. This is the largest sample of CEMP stars in any dSph for
which detailed abundances have been derived. Our sample is comprised
of one CEMP-no star, three (two) CEMP-s, and two (three) CEMP-r=s
stars (depending on the classification criteria).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 45 6 Observation Log for MIKE Data
table6.dat 47 149 Abundance uncertainties
tableb1.dat 56 786 Atomic data and abundances for individual lines
analysed
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Name Star ID ([FBN2016] NNNNNN in Simbad)
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 30 F4.1 arcsec DEs Declination (J2000)
32- 39 A8 --- ExpTime Total exposure time
41- 42 I2 --- SN-4500 SN@4500Å
44- 45 I2 --- SN-6500 SN@6500Å
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Name Star ID
9- 13 A5 --- Species Species identifier
16- 20 F5.2 [-] DTeff Uncertainty in loge(X) from
effective temperature
23- 27 F5.2 [-] Dlogg Uncertainty in loge(X) from gravity
30- 34 F5.2 [-] Dvt Uncertainty in loge(X) from microturbulence
37- 41 F5.2 [-] D[Fe/H] Uncertainty in loge(X) from metallicity
44- 47 F4.2 [-] e_loge(X) Statistical uncertainty in loge(X)
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Name Star ID
9- 15 F7.2 0.1nm Wave Wavelength in Angstroms
18- 21 F4.1 --- Species Species identifier
23- 26 F4.2 eV ExPot Excitation Potential
28- 32 F5.2 [-] log(gf) Log of oscillator strength
34 A1 --- n_EW [s] s for synth
35- 40 F6.2 0.1pm EW ? Equivalenth width in mili angstroms
42 A1 --- neEW [s] s for synth
43- 47 F5.2 0.1pm e_EW ? Error on Equivalenth width
in mili angstroms
49- 53 F5.2 [-] loge(X) Log epsilon abundance of element X
55- 56 I2 --- Ref Reference (1)
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Note (1): References
1 = Kramida et al. (2018, APS Meeting Abstracts, Vol. 2018, APS Division of
Atomic, Molecular and Optical Physics Meeting Abstracts, M01.004)
2 = Pehlivan Rhodin et al. (2017A&A...598A.102P 2017A&A...598A.102P)
3 = Yu & Derevianko (2018Atomic Data and Nuclear Data Tables, 119, 263)
4 = Lawler & Dakin (1989, Journal of the Optical Society of America B
Optical Physics, 6, 1457), using hfs from Kurucz & Bell
(1995, Atomic Line Data (R.L. Kurucz and B. Bell)
Kurucz CD-ROM No. 23. Cambridge, 23)
5 = Lawler et al. (2013ApJS..205...11L 2013ApJS..205...11L)
6 = Wood et al. (2013ApJS..208...27W 2013ApJS..208...27W, Cat. J/ApJS/208/27)
7 = Pickering et al. (2001ApJS..132..403P 2001ApJS..132..403P), with corrections given in
Pickering et al. (2002, ApJS, 138, 247)
8 = Sobeck et al. (2007ApJ...667.1267S 2007ApJ...667.1267S, Cat. J/ApJ/667/1267)
9 = Den Hartog et al. (2011ApJS..194...35D 2011ApJS..194...35D, Cat. J/ApJS/194/35) for both
log(gf) value and hfs
10 = O'Brian et al. (1991, Journal of the Optical Society of America B
Optical Physics, 8, 1185)
11 = Den Hartog et al. (2014ApJS..215...23D 2014ApJS..215...23D, Cat. J/ApJS/215/23)
12 = Belmonte et al. (2017ApJ...848..125B 2017ApJ...848..125B)
13 = Ruffoni et al. (2014MNRAS.441.3127R 2014MNRAS.441.3127R, Cat. J/MNRAS/441/3127)
14 = Den Hartog et al. (2019MNRAS.488.4258D 2019MNRAS.488.4258D)
15 = Melendez & Barbuy (2009A&A...497..611M 2009A&A...497..611M)
16 = Lawler et al. (2015ApJS..220...13L 2015ApJS..220...13L, Cat. J/ApJS/220/13) for log(gf)
values and HFS
17 = Wood et al. (2014ApJS..211...20W 2014ApJS..211...20W, Cat. J/ApJS/211/20)
18 = Roederer et al. (2012ApJS..203...27R 2012ApJS..203...27R)
19 = Biemont et al. (2011MNRAS.414.3350B 2011MNRAS.414.3350B)
20 = Ljung et al. (2006A&A...456.1181L 2006A&A...456.1181L)
21 = Kramida et al. (in APS Meeting Abstracts, Vol. 2018, APS Division of
Atomic, Molecular and Optical Physics Meeting Abstracts, M01.004),
using HFS/IS from McWilliam (1998AJ....115.1640M 1998AJ....115.1640M) when available;
22 = Lawler et al. (2001ApJ...556..452L 2001ApJ...556..452L), using HFS from Ivans et al.
(2006ApJ...645..613I 2006ApJ...645..613I, Cat. J/ApJ/645/613)
23 = Lawler et al. (2009ApJS..182...51L 2009ApJS..182...51L, Cat. J/ApJS/182/51)
24 = Li et al. (2007, Phys. Scr, 76, 577), using HFS from
Sneden et al. (2009ApJS..182...80S 2009ApJS..182...80S, Cat. J/ApJS/182/80);
25 = Ivarsson et al. (2001, Phys. Scr, 64, 455), using HFS from
Sneden et al. (2009ApJS..182...80S 2009ApJS..182...80S, Cat. J/ApJS/182/80)
26 = Den Hartog et al. (2003ApJS..148..543D 2003ApJS..148..543D), using HFS/IS from
Roederer et al. (2008ApJ...675..723R 2008ApJ...675..723R)
27 = Lawler et al. (2006ApJS..162..227L 2006ApJS..162..227L, Cat. J/ApJS/162/227), using HFS/IS
from Roederer et al. (2008ApJ...675..723R 2008ApJ...675..723R)
28 = Lawler et al. (2001ApJ...563.1075L 2001ApJ...563.1075L), using HFS/IS from
Ivans et al. (2006ApJ...645..613I 2006ApJ...645..613I, Cat. J/ApJ/645/613)
29 = Den Hartog et al. (2006ApJS..167..292D 2006ApJS..167..292D, Cat. J/ApJS/167/292)
30 = Lawler et al. (2001ApJS..137..341L 2001ApJS..137..341L), using HFS from
Lawler et al. (2001ApJS..137..351L 2001ApJS..137..351L)
31 = Wickliffe et al. (2000, J. Quant. Spectr. Rad. Transf., 66, 363)
32 = Lawler et al. (2009ApJS..182...51L 2009ApJS..182...51L, Cat. J/ApJS/182/51)
for log gf values and HFS
33 = Quinet et al. (2006A&A...448.1207Q 2006A&A...448.1207Q)
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Acknowledgements:
Terese Thidemann Hansen, thidemannhansen(at)gmail.com
(End) Patricia Vannier [CDS] 11-May-2023