J/ApJ/912/52 Abundances of 22 metal-poor stars in the MW (Gull+, 2021)
R-process-rich stellar streams in the Milky Way.
Gull M., Frebel A., Hinojosa K., Roederer I.U., Ji A.P., Brauer K.
<Astrophys. J., 912, 52 (2021)>
=2021ApJ...912...52G 2021ApJ...912...52G
ADC_Keywords: Abundances; Equivalent widths; Radial velocities;
Spectra, optical; Stars, metal-deficient; Stars, halo; Milky Way
Keywords: Halo stars ; Milky Way stellar halo ; Population II stars ;
Dwarf galaxies
Abstract:
We present high-resolution Magellan/MIKE spectra of 22 bright
(9<V<13.5) metal-poor stars (-3.18<[Fe/H]<-1.37) in three different
stellar streams, the Helmi debris stream, the Helmi trail stream, and
the ω Centauri progenitor stream. We augment our Helmi debris
sample with results for 10 stars by Roederer+ (2010, J/ApJ/711/573)
for a total of 32 stars. Detailed chemical abundances of light
elements as well as heavy neutron-capture elements have been
determined for our 22 stars. All three streams contain carbon-enhanced
stars. For 13 stars, neutron-capture element lines were detectable,
and they all show signatures in agreement with the scaled solar
r-process pattern, albeit with a large spread of -0.5<[Eu/Fe]<+1.3.
Eight of these stars show an additional small s-process contribution
superposed onto their r-process pattern. This could be discerned
because of the relatively high signal-to-noise ratio of the spectra
given that the stars are close by in the halo. Our results suggest
that the progenitors of these streams experienced one or more
r-process events early on, such as a neutron star merger or another
prolific r-process source. This widely enriched these host systems
before their accretion by the Milky Way. The small s-process
contribution suggests the presence of asymptotic giant branch stars
and associated local (inhomogeneous) enrichment as part of the ongoing
chemical evolution by low-mass stars. Stars in stellar streams may
thus be a promising avenue for studying the detailed history of large
dwarf galaxies and their role in halo assembly with easily accessible
targets for high-quality spectra of many stars.
Description:
We observed 23 stars from Beers+ (B17; 2017, J/ApJ/835/81). We did not
observe one star in the B17 list of Helmi debris stream stars
(HE2215-3842), and we exclude one star (HE1120-0153) in the ω
Cen progenitor stream from further analysis given its status as a
double-lined spectroscopic binary. Of the 22 stars analyzed further,
5 are Helmi trail stars, 7 are Helmi debris stars, and 10 are
ω Cen progenitor stream stars. We note that two of the seven
debris stars had already been analyzed by Roederer+ (2010, J/ApJ/711/573),
but we carried out our own analysis based on our spectra.
Spectroscopic observations were taken over the span of nine years at
the Magellan-Clay telescope at Las Campanas Observatory as part of our
continuous follow-up of bright metal-poor stars
(Frebel+ 2006, J/ApJ/652/1585), many of which turned out to be part of
the streams investigated here. With the Magellan Inamori Kyocera
Echelle (MIKE) spectrograph, high-resolution spectra covering
∼3500Å to ∼9000Å were obtained using the 07 slit for all but
three stars, for which a 10 slit was employed. The 07 slit yields a
nominal spectral resolving power ranging from R∼28000 in the red and
R∼35000 in the blue wavelength regime. The 10 slit yields a resolving
power of R∼22000 in the red and R∼28000 in the blue wavelength regime.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 101 23 Observing details
table2.dat 203 837 Equivalent width measurements
table5.dat 52 802 Abundances
table6.dat 97 32 Ba, Eu, and C abundances and r-process
classifications
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/350/955 : Atmospheric param. in metal-poor stars. II (Gratton+, 1999)
J/ApJ/530/783 : The r-process enriched giant HD 115444 (Westin+, 2000)
J/ApJ/612/447 : Draco 119 and HD 88609 equivalent widths (Fulbright+, 2004)
J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 2006)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJ/658/1203 : Nitrogen-enhanced metal-poor stars (Johnson+, 2007)
J/AJ/134/1579 : Halo stars in solar neighborhood (Kepley+, 2007)
J/ApJ/679/1549 : Sp. of metal-poor star CS 17435-00532 (Roederer+, 2008)
J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/ApJ/698/865 : Halo streams in the SDSS-DR7 (Klement+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/A+A/520/A95 : Abundances of red giants in M54 & Sgr dSph (Carretta+, 2010)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010)
J/A+A/516/A46 : HE 2327-5642 abundance analysis (Mashonkina+, 2010)
J/ApJ/711/573 : Detailed abund. in a halo stellar stream (Roederer+, 2010)
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/A+A/534/A53 : EWs of 18 subgiant of ω Cen (Pancino+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/AJ/144/168 : Spectroscopy of Scl 1019417 and UMi 20103 (Kirby+, 2012)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/ApJ/751/102 : Equivalent widths of 9 RGB in Carina dSph (Venn+, 2012)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/794/58 : Metal-poor stars in the thick disk of the MW (Beers+, 2014)
J/ApJS/215/23 : FeI radiative lifetimes (Den Hartog+, 2014)
J/A+A/569/A43 : HE 2252-4225 abundance analysis (Mashonkina+, 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/805/189 : Highly likely members of the Sgr stream (Hyde+, 2015)
J/ApJ/807/171 : SkyMapper Survey metal-poor star sp. (Jacobson+, 2015)
J/ApJ/802/93 : Abundance analysis of 5 stars in Sculptor (Simon+, 2015)
J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)
J/AJ/151/82 : 4 brightest red giants in Ret 2 (Roederer+, 2016)
J/ApJ/817/53 : Fe-group elemental abundances in HD84937 (Sneden+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/ApJ/844/164 : HST astro-phot. analysis of NGC5139. III. (Bellini+, 2017)
J/ApJ/838/44 : Abund. of the brightest member of Tuc III (Hansen+, 2017)
J/A+A/607/A91 : CS 29497-004 abundances (Hill+, 2017)
J/ApJS/230/28 : The populations of Carina. II. Abundances (Norris+, 2017)
J/ApJ/856/142 : Abundances of metal-poor stars in Sculptor (Chiti+, 2018)
J/ApJ/862/174 : Spectroscopy obs. of RAVE J094921.8-161722 (Gull+, 2018)
J/AJ/156/179 : r-process-enhanced field stars kinematics (Roederer+, 2018)
J/ApJ/882/177 : Abundances of 4 member stars of Tucana III (Marshall+, 2019)
J/ApJ/883/84 : MIKE obs. of 2 stars in Sylgr stream (Roederer+, 2019)
J/ApJ/874/148 : RAVE J093730.5-062655 abundances (Sakari+, 2019)
J/ApJ/890/119 : Iron abundances in 3 very metal-poor stars (Cowan+, 2020)
J/AJ/160/181 : Chemical abundances in red giants with Magellan (Ji+, 2020)
J/ApJ/889/27 : Abundances of 11 stars in Carina II and III (Ji+, 2020)
J/AJ/159/254 : Metal-poor stars in NGC5139 (Johnson+, 2020)
J/ApJ/900/106 : Vanadium abundances for 255 metal-poor stars (Ou+, 2020)
J/other/Nat/583.768 : 2050 red giants CaII EWs (Wan+, 2020)
J/ApJ/891/39 : LAMOST DR3 metal-poor stars of the Gal. halo (Yuan+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Stream Stream identifier
22- 32 A11 --- Name Star identifier (G1)
34 A1 --- n_Name Note on HE1120-0153 (added by CDS) (1)
36- 37 I2 h RAh Hour of right ascension (J2000) (2)
39- 40 I2 min RAm Minute of right ascension (J2000)
42- 45 F4.1 s RAs Second of right ascension (J2000)
47 A1 --- DE- Sign of declination (J2000)
48- 49 I2 deg DEd Degree of declination (J2000) (2)
51- 52 I2 arcmin DEm Arcminute of declination (J2000) (2)
54- 57 F4.1 arcsec DEs Arcsecond of declination (J2000)
59- 68 A10 "Y/M/D" Date Date of observation (UT)
70- 72 F3.1 arcsec Slit [0.7/1] Slit
74- 75 I2 min Texp [3/30] Exposure time
77- 81 F5.2 mag Vmag [8.02/13.51] V magnitude
83- 86 F4.2 mag B-V [0.37/1.16] B-V color index
88- 90 I3 --- S/N4500 [30/350] Signal to noise 4500Å ratio
92- 94 I3 --- S/N6000 [40/500] Signal to noise 6000Å ratio
96-101 F6.1 km/s HRV [-373/387.7] Heliocentric-corrected
radial velocity (3)
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Note (1): Note as follows:
e = We exclude one star (HE 1120-0153) in the ω Cen progenitor stream
from further analysis given its status as a double-lined spectroscopic
binary. See Section 2.
Note (2): Beers+ (B17; 2017, J/ApJ/835/81) coordinates for HE0012-5643 are
00 15 17.1 -56 26 27 (J2000); not "10 56 17.9 -30 57 49.3" as given in this
table. Coordinates have been corrected here by CDS.
Note (3): Radial velocities were obtained from cross-correlating the Ca triplet
region with a template metal-poor star of similar stellar parameters.
Typical uncertainties in radial velocity measurements obtained with
MIKE are ∼1-2km/s. See Section 2.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 -- Sp Atomic species
7- 13 F7.2 0.1nm lambda [3383.76/8824.22] Rest wavelength
15- 18 F4.2 eV chi [0/5.1]? Excitation potential
20- 27 F8.2 [-] loggf [0/0.8]? Log statistical weight*oscillator
strength
29- 35 F7.1 0.1nm BM235 [4/262]? Measured equivalent width for
BM235
37- 43 F7.1 0.1nm HE0033-2141 [5/179]? Measured equivalent width for
HE0033-2141
45- 51 F7.1 0.1nm HE0050-0918 [4.8/367]? Measured equivalent width for
HE0050-0918
53- 59 F7.1 0.1nm HE1210-2729 [3.5/204]? Measured equivalent width for
HE2234-4757
61- 67 F7.1 0.1nm HE2234-4757 [4/245.2]? Measured equivalent width for
HE2234-4757
69- 75 F7.1 0.1nm BM028 [3/276.3]? Measured equivalent width for
BM028
77- 83 F7.1 0.1nm BM201 [3/258]? Measured equivalent width for
BM201
85- 91 F7.1 0.1nm BM308 [2/273]? Measured equivalent width for
BM308
93- 99 F7.1 0.1nm HE0012-5643 [1.9/91]? Measured equivalent width for
HE0012-5643
101- 107 F7.1 0.1nm HE0017-3646 [3.7/196]? Measured equivalent width for
HE0017-3646
109- 115 F7.1 0.1nm HE0048-1109 [1/136]? Measured equivalent width for
E0048-1109
117- 123 F7.1 0.1nm HE0324-0122 [3.9/240]? Measured equivalent width for
HE0324-0122
125- 131 F7.1 0.1nm BM056 [0/229]? Measured equivalent width for
BM056
133- 139 F7.1 0.1nm BM121 [3.7/291]? Measured equivalent width for
BM121
141- 147 F7.1 0.1nm HE0007-1752 [2/206]? Measured equivalent width for
HE0007-1752
149- 155 F7.1 0.1nm HE0039-0216 [1.6/123]? Measured equivalent width for
HE0039-0216
157- 163 F7.1 0.1nm HE0429-4620 [2/226.1]? Measured equivalent width for
HE0429-4620
165- 171 F7.1 0.1nm HE1401-0010 [1/128.4]? Measured equivalent width for
HE1401-0010
173- 179 F7.1 0.1nm HE2138-0314 [2/133]? Measured equivalent width for
HE2138-0314
181- 187 F7.1 0.1nm HE2315-4306 [3.8/248.4]? Measured equivalent width for
HE2315-4306
189- 195 F7.1 0.1nm HE2319-5228 [3/233]? Measured equivalent width for
HE2319-5228
197- 203 F7.1 0.1nm HE2322-6125 [6.6/220]? Measured equivalent width for
HE2322-6125
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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- 1 I1 --- Loc [1/3] Location (1)
3- 13 A11 --- Name Stellar identifier (G1)
15- 19 A5 --- Sp Species identifier
21- 21 A1 --- l_logAbd Limit flag on logAbd
23- 27 F5.2 [-] logAbd [-2.95/7.8]? log number abundance
29- 29 A1 --- l_[X/H] Limit flag on [X/H]
31- 35 F5.2 [-] [X/H] [-4.1/-0.46]? log abundance relative to hydrogen
37- 37 A1 --- l_[X/Fe] Limit flag on [X/Fe]
39- 43 F5.2 [-] [X/Fe] [-1.21/2.6]? log abundance relative to iron (2)
45- 47 I3 --- N [1/291]? Number of lines use to
derived abundances (3)
49- 52 F4.2 [-] sigma [0.06/0.3]? Uncertainty in the abundances (3)
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Note (1): Location as follows:
1 = the Helmi trail stream.
2 = the Helmi Debris Stream.
3 = the ω Cen progenitor stream.
Note (2): [X/Fe] ratios are computed with [FeI/H] abundances of the
respective stars. Solar abundances have been taken from
Asplund+ (2009ARA&A..47..481A 2009ARA&A..47..481A).
Note (3): For abundances measured from only one line, we adopt a nominal
uncertainty of 0.10dex.
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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- 20 A20 --- Stream Stream identifier
22- 33 A12 --- Name Star identifier (G1)
35- 39 F5.2 Sun [Fe/H] [-3.36/-1.37] Log of Fe/H abundance
41 A1 --- l_[Eu/Fe] Limit flag on [Eu/Fe]
43- 47 F5.2 Sun [Eu/Fe] [-0.46/1.91] Log of Eu/Fe abundance
49 A1 --- l_[Ba/Fe] Limit flag on [Ba/Fe]
51- 55 F5.2 Sun [Ba/Fe] [-1.74/0.76] Log of Ba/Fe abundance
57 A1 --- l_[Ba/Eu] Limit flag on [Ba/Eu]
59- 63 F5.2 Sun [Ba/Eu] [-1.7/0.37]? Log of Ba/Eu abundance (1)
65 A1 --- l_[C/Fe]c Limit flag on [C/Fe]c
67- 71 F5.2 --- [C/Fe]c [-0.72/1.72] lof of C/Fe corrected abundance
73- 80 A8 --- Class r-process classification
82- 84 A3 --- R10 R10 = also in Roederer+, 2010, J/ApJ/711/573
86- 97 A12 --- Comm Comment (2)
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Note (1): For reference, the pure r-process ratio is [Ba/Eu]=-0.71
(Sneden+ 2008ARA&A..46..241S 2008ARA&A..46..241S). We consider -0.8<[Ba/Eu]<-0.45 as the
range covered by a pure main r-process signature
(Frebel 2018ARNPS..68..237F 2018ARNPS..68..237F). Higher values reflect an additional
s-process contribution, provided the neutron-capture pattern
principally follows the pattern for combined r+s enrichment, as shown
in Figure 5.
Note (2): "AB" denotes actinide-boost stars. Stellar ages and other star names
are given where available.
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Global notes:
Note (G1): "BM209" in text and tables is a misprint for "BM201" (HD 128279);
corrected at CDS. The misprint comes from Beers+ 2017ApJ...835...81B 2017ApJ...835...81B
(Table 7).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Oct-2022