J/ApJ/865/129 Abundance analysis of HD 222925 (Roederer+, 2018)
The R-Process Alliance: a comprehensive abundance analysis of HD 222925, a
metal-poor star with an extreme r-process enhancement of [Eu/H]=-0.14.
Roederer I.U., Sakari C.M., Placco V.M., Beers T.C., Ezzeddine R.,
Frebel A., Hansen T.T.
<Astrophys. J., 865, 129 (2018)>
=2018ApJ...865..129R 2018ApJ...865..129R
ADC_Keywords: Abundances; Stars, metal-deficient; Equivalent widths;
Stars, horizontal branch; Optical
Keywords: nuclear reactions, nucleosynthesis, abundances ; stars: abundances ;
stars: individual (HD 222925)
Abstract:
We present a detailed abundance analysis of the bright (V=9.02),
metal-poor ([Fe/H]=-1.47±0.08) field red horizontal-branch star
HD222925, which was observed as part of an ongoing survey by the
R-Process Alliance. We calculate stellar parameters and derive
abundances for 46 elements based on 901 lines examined in a
high-resolution optical spectrum obtained using the Magellan Inamori
Kyocera Echelle spectrograph. We detect 28 elements with 38≤Z≤90;
their abundance pattern is a close match to the solar r-process
component. The distinguishing characteristic of HD222925 is an extreme
enhancement of r-process elements ([Eu/Fe]=+1.33±0.08,
[Ba/Eu]=-0.78±0.10) in a moderately metal-poor star, so the
abundance of r-process elements is the highest ([Eu/H]=-0.14±0.09)
in any known r-process-enhanced star. The abundance ratios among
lighter (Z≤30) elements are typical for metal-poor stars, indicating
that production of these elements was dominated by normal Type II
supernovae, with no discernible contributions from Type Ia supernovae
or asymptotic giant branch stars. The chemical and kinematic
properties of HD 222925 suggest it formed in a low-mass dwarf galaxy,
which was enriched by a high-yield r-process event before being
disrupted by interaction with the Milky Way.
Description:
We observed HD 222925 on 2017 September 26 using the Magellan Inamori
Kyocera Echelle spectrograph (MIKE) mounted at the f/11 focus on the
east Nasmyth platform of the Landon Clay (Magellan II) Telescope at
Las Campanas Observatory, Chile. A pair of 50s observations.
We reobserved HD 222925 with MIKE on 2017 September 28 with a series
of 300 and 600s exposures, totaling 115 minutes. This setup yielded a
spectral resolving power R∼68000 on the blue spectrograph
(λ≲5000Å) and R∼61000 on the red spectrograph.
Our measured heliocentric RV, -38.9±0.6km/s, agrees with that
measured by Navarrete+ (2015, J/ApJ/808/103), -38.64±0.36km/s, and
the RV reported by the second data release (DR2) of the Gaia mission
(Katz+ 2019A&A...622A.205K 2019A&A...622A.205K and Lindegren+ 2018A&A...616A...2L 2018A&A...616A...2L ;
see I/345), -37.93±0.28km/s.
Objects:
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RA (ICRS) DE Designation(s) (RV_km/s)
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23 45 17.61 -61 54 42.8 HD 222925 = TYC 9127-939-1 (RV=-38.9)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 41 901 Lines, atomic data, EWs, and abundances
refs.dat 161 49 References
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
III/279 : RAVE 5th data release (Kunder+, 2017)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/435/373 : Broadening of Fe II lines by H collisions (Barklem+, 2005)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/ApJS/167/292 : Laboratory transitions for Gd II (Den Hartog+, 2006)
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 2006)
J/ApJS/162/227 : Transition probabilities for SmII (Lawler+, 2006)
J/AJ/132/85 : Equivalent width of 33 metal-poor RHB (Preston+, 2006)
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/465/271 : Oxygen abundances in nearby stars (Ramirez+, 2007)
J/ApJ/667/1267 : CrI transition probabilities (Sobeck+, 2007)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/ApJS/182/51 : Transitions of rare earth elements (Lawler+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/AJ/140/1694 : Abundances of non-variable red & blue HB stars (For+, 2010)
J/ApJ/724/975 : Heavy elements abund. of metal-poor stars (Roederer+, 2010)
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/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/MNRAS/427/343 : Infrared excesses of Hipparcos stars (McDonald+, 2012)
J/ApJ/750/76 : R-process peaks elements in HD 160617 (Roederer+, 2012)
J/ApJ/775/L27 : Abundances in a metal-poor RGB star (Johnson+, 2013)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJ/794/58 : Metal-poor stars in the Galaxy thick disk (Beers+, 2014)
J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014)
J/ApJS/215/23 : FeI radiative lifetimes (Den Hartog+, 2014)
J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)
J/ApJS/215/20 : Vanadium log(gf) & transition probabilities (Lawler+, 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/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJ/797/13 : Abundances of bright metal-poor stars (Schlaufman+, 2014)
J/ApJS/214/18 : VII log(gf) values, and V abundance in HD 84937 (Wood+ 2014)
J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)
J/A+A/577/A9 : Sc, V, Mn, and Co in Milky Way stars (Battistini+, 2015)
J/A+A/581/A138 : Photom. variability in magnetic CP stars (Bernhard+, 2015)
J/ApJ/807/171 : SkyMapper metal-poor star spectroscopy (Jacobson+, 2015)
J/ApJS/220/13 : Co I transition probabilities (Lawler+, 2015)
J/ApJ/808/103 : Kapteyn moving group star abundances (Navarrete+, 2015)
J/A+A/586/A49 : r- & s- process elements in the MW disk (Battistini+, 2016)
J/ApJ/830/93 : Abundances of Ret II brightest red giant members (Ji+, 2016)
J/ApJ/817/53 : Fe-group abundance analysis in HD84937 (Sneden+, 2016)
J/ApJ/819/53 : Magellan/M2FS spectroscopy of Tuc 2 & Grus 1 (Walker+, 2016)
J/ApJ/847/142 : Ultra-metal-poor stars LTE & NLTE abund. (Ezzeddine+, 2017)
J/ApJ/838/44 : Abundances of TucIII brightest members (Hansen+, 2017)
J/A+A/607/A91 : CS 29497-004 abundances (Hill+, 2017)
J/ApJS/228/10 : Transitions for 183 lines of Cr II (Lawler+, 2017)
J/ApJ/844/18 : RAVE J203843.2-002333 high-res. spectroscopy (Placco+, 2017)
J/AJ/155/240 : A spectroscopic survey of field RHB stars (Afsar+, 2018)
J/ApJ/862/174 : Spectroscopy obs. of RAVE J094921.8-161722 (Gull+, 2018)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/ApJ/857/2 : Abundances in 6 metal-poor stars (Roederer+, 2018)
J/ApJ/860/125 : Six warm metal-poor stars iron abundances (Roederer+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Ion Species
6- 12 F7.2 0.1nm lambda [3351.2/8220.4] Wavelength in Angstroms
14- 17 F4.2 eV ExPot [0/6.3] Excitation potential
19- 23 F5.2 [-] log(gf) [-5.7/0.9] log of degeneracy times
oscillator strength
25- 26 I2 --- r_log(gf) [1/49] Reference for log of degeneracy
times oscillator strength
(see refs.dat file)
28- 32 F5.1 0.1pm EW [0.9/139]? Equivalent width
in milli Angstroms
34- 34 A1 --- l_log(eps) Limit on log epsilon abundance
35- 41 F7.3 [-] log(eps) [-0.5/6.814] log epsilon abundance
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode of the reference
24- 45 A22 --- Auth Author's name(s)
47-161 A115 --- Comm Comment
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Sep-2019