J/ApJ/844/18 RAVE J203843.2-002333 high-resolution spectroscopy (Placco+, 2017)
RAVE J203843.2-002333: the first highly R-process-enhanced star identified in
the RAVE survey.
Placco V.M., Holmbeck E.M., Frebel A., Beers T.C., Surman R.A., Ji A.P.,
Ezzeddine R., Points S.D., Kaleida C.C., Hansen T.T., Sakari C.M.,
Casey A.R.
<Astrophys. J., 844, 18 (2017)>
=2017ApJ...844...18P 2017ApJ...844...18P
ADC_Keywords: Stars, metal-deficient ; Abundances ; Equivalent widths
Keywords: galaxy: halo ; stars: abundances ; stars: atmospheres ;
stars: individual (RAVE J203843.2-002333) ; stars: Population II ;
techniques: imaging spectroscopy
Abstract:
We report the discovery of RAVE J203843.2-002333, a bright (V=12.73),
very metal-poor ([Fe/H]=-2.91), r-process-enhanced ([Eu/Fe]=+1.64 and
[Ba/Eu]=-0.81) star selected from the RAVE survey. This star was
identified as a metal-poor candidate based on its medium-resolution
(R∼1600) spectrum obtained with the KPNO/Mayall Telescope, and
followed up with high-resolution (R∼66000) spectroscopy with the
Magellan/Clay Telescope, allowing for the determination of elemental
abundances for 24 neutron-capture elements, including thorium and
uranium. RAVE J2038-0023 is only the fourth metal-poor star with a
clearly measured U abundance. The derived chemical abundance pattern
exhibits good agreement with those of other known highly r-process-
enhanced stars, and evidence suggests that it is not an actinide-boost
star. Age estimates were calculated using U/X abundance ratios,
yielding a mean age of 13.0±1.1Gyr.
Description:
Medium-resolution spectroscopic follow-up was carried out with the
Mayall 4m Telescope at Kitt Peak National Observatory. The
observations were obtained in semester 2014B, using the R-C
spectrograph covering the wavelength range [3500,6000]Å (R∼1600).
High-resolution spectroscopic data were obtained during the 2014B and
2016A semesters, using the Magellan Inamori Kyocera Echelle (MIKE)
spectrograph on the Magellan/Clay Telescope at Las Campanas Observatory.
For the 2014B run, the setup yielding a resolving power of R∼38000
(blue spectral range) and R∼30000 (red spectral range). For the 2016A
run, the resolving power was R∼66000 (coverage [∼3500,9000]Å).
Objects:
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RA (ICRS) DE Designation(s)
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20 38 43.18 -00 23 32.8 RAVEJ2038 = RAVE J203843.2-002333
22 17 01.66 -16 39 27.1 CS22892-052 = BPS CS 22892-0052
15 26 01.07 -09 11 38.9 HE1523-0901 = TYC 5594-576-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 39 344 Equivalent-width measurements for RAVE J2038-0023
table4.dat 34 115 Individual abundance measurements of
neutron-capture elements for RAVE J2038-0023
table5.dat 45 42 Final abundance estimates for RAVE J2038-0023
figure1.dat 28 13364 Selected regions of the spectrum of RAVE J2038-0023,
compared with the r-II stars HE 1523-0901 and
CS 22892-052
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See also:
III/279 : RAVE 5th data release (Kunder+, 2017)
J/AJ/90/2089 : Stars of very low metal abundance. I (Beers+, 1985)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)
J/A+A/516/A46 : HE 2327-5642 abundance analysis (Mashonkina+, 2010)
J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/794/58 : Metal-poor stars in the thick disk of the MW (Beers+, 2014)
J/ApJ/781/40 : Metal-poor stars from HES survey. II. (Placco+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/812/109 : HST & Keck spectroscopy of bright CEMP-s stars (Placco+, 2015)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Ion or molecule identifier
7- 14 F8.3 0.1nm lambda [3500.8/6979] Wavelength in Angstroms
16- 19 F4.2 eV chi [0.0/4.5] Excitation potential
21- 26 F6.3 [-] log(gf) [-5.7/0.7] Log oscillator strength
28- 33 F6.2 0.1nm EW [3/209] Equivalent Width in Angstroms
35- 39 F5.3 [Sun] logeps(x) [0/5.3] Log number abundance of Ion
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Ion or molecule identifier
7- 14 F8.3 0.1nm lambda [3472.4/6645.1] Wavelength in Angstroms
16- 20 F5.3 eV chi [0/3] Excitation potential
22- 27 F6.3 [-] log(gf) [-1.6/1.5] Log oscillator strength
29- 34 F6.3 [Sun] logeps(x) [-2.2/0.6] Log number abundance of Ion
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Ion Ion or molecule identifier
8- 12 F5.2 [Sun] logepsSun [-0.6/8.5] Log number abundance of Ion
(logε☉(X))
14- 18 F5.2 [Sun] logeps(x) [-2.2/5.8] Log number abundance of Ion
(logε(X))
20- 24 F5.2 [Sun] [X/H] [-3.5/-1.2] Average abundance
26- 30 F5.2 [Sun] [X/Fe] Elemental abundance ratio
31 A1 --- f_[X/Fe] Flag on [C/Fe] (1)
33- 36 F4.2 [Sun] sigma [0.01/0.2] Standard deviation
38- 41 F4.2 [Sun] overSig [0.1/0.2] Standard error of the mean (2)
43- 45 I3 --- N [1/202] Number of line used
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Note (1):
a: [C/Fe] = +0.23 using corrections of Placco+ (2014, J/ApJ/797/21).
Note (2): For elements where overlineσ is lower than 0.10, we adopt a
fixed value of 0.10 (see the discussion in Section 4.6 of
Placco+ 2013ApJ...770..104P 2013ApJ...770..104P).
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Byte-by-byte Description of file: figure1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- ID Stellar identifier (CS22892-052, HE1523-0901
or "RAVEJ2038")
13 A1 --- Panel [A-E] Figure 1 panel spectrum shown in
15- 22 F8.3 0.1nm lambda [4065/5190] Wavelength in Angstroms
24- 28 F5.3 --- NFlux [0.1/1.4] Normalized flux
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Mar-2018