J/ApJ/898/40 2MASS J15213995-3538094 abundances from high-res. sp. (Cain+, 2020)
The r-process alliance: a very metal-poor, extremely r-process-enhanced star
with [Eu/Fe]=+2.2, and the class of r-III stars.
Cain M., Frebel A., Ji A.P., Placco V.M., Ezzeddine R., Roederer I.U.,
Hattori K., Beers T.C., Melendez J., Hansen T.T., Sakari C.M.
<Astrophys. J., 898, 40-40 (2020)>
=2020ApJ...898...40C 2020ApJ...898...40C (SIMBAD/NED BibCode)
ADC_Keywords: Abundances; Equivalent widths; Stars, metal-deficient;
Spectra, optical
Keywords: Milky Way stellar halo; Nucleosynthesis; Stellar abundances
Population II stars
Abstract:
We report the discovery of J1521-3538, a bright (V=12.2), very
metal-poor ([Fe/H]=-2.8) strongly r-process-enhanced field horizontal
branch star, based on a high-resolution, high signal-to-noise
Magellan/MIKE spectrum. J1521-3538 shows the largest r-process element
overabundance in any known r-process-enhanced star, with [Eu/Fe]=+2.2,
and its chemical abundances of 22 neutron-capture elements closely
match the scaled solar r-process pattern. J1521-3538 is also one of
few known carbon-enhanced metal-poor stars with r-process enhancement
(CEMP-r stars), as found after correcting the measured C abundance for
the star's evolutionary status. We propose to extend the existing
classification of moderately enhanced (+0.3≤[Eu/Fe]≤+1.0) r-I and
strongly r-process enhanced ([Eu/Fe]>+1.0) r-II stars to include an
r-III class, for r-process stars such as J1521-3538, with [Eu/Fe]>+2.0
and [Ba/Eu]<-0.5, or ≥100 times the solar ratio of europium to
iron. Using cosmochronometry, we estimate J1521-3538 to be 12.5±5Gyr
and 8.9±5Gyr, using two different sets of initial production ratios.
These ages are based on measurements of the Th line at 4019Å and
other r-process element abundances. This is broadly consistent with
the old age of a low-mass, metal-poor field red horizontal branch
star. J1521-3538 likely originated in a low-mass dwarf galaxy that was
later accreted by the Milky Way, as evidenced by its highly eccentric
orbit.
Description:
The 2MASS J15213995-3538094 very metal-poor red horizontal branch star
was followed-up with medium-resolution (R∼2000) spectroscopy using the
ESO New Technology Telescope (EFOSC-2; semester 2014A) and the Gemini
South Telescope (GMOS-S; semester 2015A). Further details on the
observations, data reduction, and processing can be found in
Placco+ (2018, J/AJ/155/256).
We then observed J1521-3538 using the Magellan Clay telescope and the
MIKE spectrograph at Las Campanas Observatory on 2016 April 16 and
2017 May 6. We obtained a high-resolution spectrum with nominal
resolving power of R∼35000 in the blue, and R∼28000 in the red
wavelength regime (Total wavelength range: ∼3500Å to ∼9000Å).
Objects:
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RA (ICRS) DE Designation(s)
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15 21 39.95 -35 38 09.3 2MASS J15213995-3538094 = TYC 7325-920-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 41 462 Line list and derived abundances for
2MASS J15213995-3538094
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See also:
III/279 : RAVE 5th data release (Kunder+, 2017)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
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/132/137 : Abundances of extremely metal-poor carbon stars (Cohen+, 2006)
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 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/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJ/679/1549 : Spec. of metal-poor star CS 17435-00532 (Roederer+, 2008)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
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/A+A/548/A42 : Average spectrum of HD140283 (Siqueira Mello+ 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 Galaxy thick disk (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/A+A/571/A47 : Extensive linelist of CH in stellar atm. (Masseron+, 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/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
J/A+A/571/A40 : Abundances in 2 extremely metal-poor stars (Spite+, 2014)
J/ApJ/814/121 : CASH project. III. The CEMP star HE0414-0343 (Hollek+, 2015)
J/ApJ/807/171 : SkyMapper Survey metal-poor star spec. (Jacobson+, 2015)
J/ApJ/798/110 : Equivalent widths of LAMOST metal-poor stars (Li+, 2015)
J/ApJ/812/109 : HST & Keck spectroscopy of bright CEMP-s stars (Placco+, 2015)
J/A+A/574/A129 : The First CEMP star in the Sculptor dSph (Skuladottir+, 2015)
J/ApJ/830/93 : Abundances of Ret II brightest red giant members (Ji+, 2016)
J/ApJ/817/53 : Fe-group elemental abundances in HD84937 (Sneden+, 2016)
J/ApJ/819/53 : Magellan/M2FS spec. of Tucana 2 & Grus 1 (Walker+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/ApJ/850/179 : 2MASS J15111324-2130030 metal-poor star abund. (Casey+, 2017)
J/ApJ/847/142 : Ultra-metal-poor stars LTE & NLTE abund. (Ezzeddine+, 2017)
J/A+A/607/A91 : CS 29497-004 abundances (Hill+, 2017)
J/ApJ/844/18 : RAVE J203843.2-002333 high-resolution spec. (Placco+, 2017)
J/A+A/612/A90 : Inelastic Fe+H collision data (Barklem, 2018)
J/ApJ/864/43 : Abund. of 3 bright extremely metal-poor giants (Cain+, 2018)
J/A+A/618/A141 : H-atom collisions NLTE corrections (Ezzeddine+, 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/AJ/155/256 : Spec. validation of RAVE metal-poor stars (Placco+, 2018)
J/AJ/156/179 : Highly r-process-enhanced stars kinematics (Roederer+, 2018)
J/ApJ/865/129 : Abundance analysis of HD 222925 (Roederer+, 2018)
J/ApJ/874/148 : Metal-poor star RAVE J093730.5-062655 abund. (Sakari+, 2019)
J/ApJ/891/39 : LAMOST DR3 very metal-poor stars of Gal. halo (Yuan+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Element identifier
7- 13 F7.2 0.1nm lambda [3398.94/8688.62] Wavelength; Angstroms
15- 19 F5.2 eV ExPot [-0.6/4.47]? Excitation potential
21- 25 F5.2 [-] log(gf) [-3.9/2.94]? log oscillator strength
27- 31 F5.1 10-13m EW [2.4/133]? Equivalent width; milli-Angstroms
33- 33 A1 --- f_EW [s] Indicates a synthesis line
35- 35 A1 --- l_logAbd Limit flag on logAbd
37- 41 F5.2 [-] logAbd [-0.83/6.2] log derived abundance
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Nov-2021