J/ApJ/864/43 Abundances of 3 bright extremely metal-poor giants (Cain+, 2018)
The r-process alliance: chemical abundances for a trio of r-process-enhanced
stars --one strong, one moderate, and one mild.
Cain M., Frebel A., Gull M., Ji A.P., Placco V.M., Beers T.C., Melendez J.,
Ezzeddine R., Casey A.R., Hansen T.T., Roederer I.U., Sakari C.
<Astrophys. J., 864, 43 (2018)>
=2018ApJ...864...43C 2018ApJ...864...43C
ADC_Keywords: Spectra, optical; Abundances; Stars, giant; Stars, halo;
Equivalent widths
Keywords: Galaxy: halo ; nuclear reactions, nucleosynthesis, abundance ;
stars: abundances ; stars: Population II
Abstract:
We present detailed chemical abundances of three new bright (V∼11),
extremely metal-poor ([Fe/H]~-3.0), r-process-enhanced halo red giants
based on high-resolution, high-S/N Magellan/MIKE spectra. We measured
abundances for 20-25 neutron-capture elements in each of our stars.
J1432-4125 is among the most r-process-rich r-II stars, with
[Eu/Fe]=+1.44±0.11. J2005-3057 is an r-I star with
[Eu/Fe]=+0.94±0.07. J0858-0809 has [Eu/Fe]=+0.23±0.05 and exhibits
a carbon abundance corrected for an evolutionary status of
[C/Fe]corr=+0.76, thus adding to the small number of known
carbon-enhanced r-process stars. All three stars show remarkable
agreement with the scaled solar r-process pattern for elements above
Ba, consistent with enrichment of the birth gas cloud by a neutron
star merger. The abundances for Sr, Y, and Zr, however, deviate from
the scaled solar pattern. This indicates that more than one distinct
r-process site might be responsible for the observed neutron-capture
element abundance pattern. Thorium was detected in J1432-4125 and
J2005-3057. Age estimates for J1432-4125 and J2005-3057 were adopted
from one of two sets of initial production ratios each by assuming the
stars are old. This yielded individual ages of 12±6Gyr and
10±6Gyr, respectively.
Description:
J0858-0809 and J2005-3057 were first identified as metal-poor star
candidates in the RAVE DR5 database (Kunder+ 2017, III/279).
They were then followed up with medium-resolution spectroscopy using
the KPNO/Mayall (RC Spectrograph - semester 2014A) and Gemini South
(GMOS--semester 2015A) telescopes, respectively.
J1432-4125 was followed up with medium-resolution spectroscopy in
semester 2014A using the EFOSC-2 spectrograph at the ESO New
Technology Telescope.
The observing setup was similar for all three telescope/spectrograph
combinations (wavelength range ∼3550-5500Å, R∼2000).
We then observed J0858-0809, J1432-4125, and J2005-3057 using the
Magellan-Clay telescope and the MIKE spectrograph at Las Campanas
Observatory, on 2016 April 14 and 15. J0858-0809 was re-observed on
2016 April 17. For each star, we obtained a high-resolution spectrum
with nominal resolving power of R∼35000 in the blue and R∼28000 in the
red wavelength regime (wavelength range ∼3350-9000Å).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 199 3 Stellar parameters and observation details
(Tables 1 and 2)
table3.dat 81 824 Equivalent width and synthesis measurements for
J0858-0809, J1432-4125, and J2005-3057
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
III/279 : RAVE 5th data release (Kunder+, 2017)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
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/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/794/58 : Metal-poor stars in the Galaxy thick disk (Beers+, 2014)
J/ApJS/215/23 : FeI branching fractions (Den Hartog+, 2014)
J/A+A/571/A47 : Linelist of CH in stellar atmospheres (Masseron+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
J/ApJ/830/93 : Ret II brightest red giant member abundances (Ji+, 2016)
J/ApJ/817/53 : Fe-group abundance analysis in HD84937 (Sneden+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/ApJ/847/142 : Ultra-metal-poor stars LTE & NLTE abund. (Ezzeddine+, 2017)
J/ApJ/838/44 : Abundances of Tuc III brightest members (Hansen+, 2017)
J/A+A/607/A91 : CS 29497-004 abundances (Hill+, 2017)
J/ApJ/844/18 : RAVE J203843.2-002333 high-res. spectroscopy (Placco+, 2017)
J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)
J/A+A/612/A90 : Inelastic Fe+H collision data (Barklem, 2018)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/AJ/155/256 : Spectroscopy of RAVE metal-poor stars (Placco+, 2018)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12- 15 I4 K Teff1 [4430/4900] LTE corrected effective temperature
17- 20 F4.2 [cm/s2] logg1 [0.6/1.7] LTE corrected surface gravity
22- 25 F4.2 km/s Vt1 [1.6/2.3] LTE corrected microturbulent velocity
27- 31 F5.2 [-] [Fe/H]1 [-3.2/-2.9] LTE corrected [Fe/H]
33- 36 I4 K Teff2 [4180/4705] LTE uncorrected effective
temperature
38- 41 F4.2 [cm/s2] logg2 [0/1.2] LTE uncorrected surface gravity
43- 46 F4.2 km/s Vt2 [1.5/2.2] LTE uncorrected microturbulent
velocity
48- 52 F5.2 [-] [Fe/H]2 [-3.4/-3.1] LTE uncorrected [Fe/H]
54- 57 I4 K Teff3 [4300/4850] NLTE effective temperature
59- 62 F4.2 [cm/s2] logg3 [0.9/1.9] NLTE surface gravity
64- 67 F4.2 km/s Vt3 [1.5/2.2] NLTE microturbulent velocity
69- 73 F5.2 [-] [Fe/H]3 [-2.9/-2.8] NLTE [Fe/H]
75- 78 I4 K Teff4 [4599/5334] Effective temperature
from medium-resolution spectrum
80- 83 F4.2 [cm/s2] logg4 [0.9/2.7] Surface gravity
from medium-resolution spectrum
85- 89 F5.2 [-] [Fe/H]4 [-3.1/-2.9] [Fe/H]
from medium-resolution spectrum
91- 92 I2 h RAh Hour of right ascension (J2000)
94- 95 I2 min RAm Minute of right ascension (J2000)
97-100 F4.1 s RAs Second of right ascension (J2000)
102 A1 --- DE- Sign of declination (J2000)
103-104 I2 deg DEd Degree of declination (J2000)
106-107 I2 arcmin DEm Arcminute of declination (J2000)
109-110 I2 arcsec DEs Arcsecond of declination (J2000)
112-122 A11 "Y/M/D" Obs.date Observation date (UT)
124-131 A8 "h:m:s" Obs.time UT time of the observation
133-135 F3.1 arcsec Slit Slit
137-138 I2 min Exp Exposure time
140-144 F5.2 mag Vmag V-band magnitude
146-149 F4.2 mag B-V B-V color index
151-153 I3 --- SN4000 Signal-to-noise ratio per pixel at 4000Å (1)
155-157 I3 --- SN4500 Signal-to-noise ratio per pixel at 4500Å (1)
159-161 I3 --- SN6000 Signal-to-noise ratio per pixel at 6000Å (1)
163-168 F6.1 km/s HRV Heliocentric velocity
170-180 A11 "Y/M/D" Obs2.date Second date of observation (UT)
182-189 A8 "h:m:s" Obs2.time UT time of the second observation
191-192 I2 min Exp2 ? Exposure time of the second observation
194-199 F6.1 km/s HRV2 ? Second measure of heliocentric velocity
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Note (1): J0858-0809 was observed over two nights, so we list the S/N values
that result from the combined spectrum from both nights.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Ion Element/Ion identifier
8- 14 F7.2 0.1nm lambda [3329.4/8824.3] Wavelength; Angstrom
17- 20 F4.2 eV ExPot [0/4.5]? Excitation potential
23- 27 F5.2 [-] log(gf) [-9.9/0.8]? log oscillator strength
30- 34 F5.1 10-13m EW1 [1.8/219.4]? Equivalenth width of J0858-0809 (1)
37 A1 --- f_EW1 [s] Flag on EW1 (2)
39 A1 --- l_loge1 Limit flag on loge1
41- 45 F5.2 [-] loge1 [-3.1/6.5]? log absolute abundance of J0858-0809
48- 52 F5.1 10-13m EW2 [3.5/208.3]? Equivalenth width of J1432-4125 (1)
55 A1 --- f_EW2 [s] Flag on EW2 (2)
57 A1 --- l_loge2 Limit flag on loge2
59- 63 F5.2 [-] loge2 [-1.7/5.7]? log absolute abundance of J1432-4125
66- 70 F5.1 10-13m EW3 [2.6/250.7]? Equivalenth width of J2005-3057 (1)
73 A1 --- f_EW3 [s] Flag on EW3 (2)
75 A1 --- l_loge3 Limit flag on loge3
77- 81 F5.2 [-] loge3 [-2.2/6.6]? log absolute abundance of J2005-3057
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Note (1): In units of milli-Angstrom.
Note (2):
s = abundance was measured using a synthetic spectrum.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Aug-2019