J/ApJ/850/179 2MASS J15111324-2130030 metal-poor star abundances (Casey+, 2017)
The universality of the rapid neutron-capture process revealed by a possible
disrupted dwarf galaxy star.
Casey A.R., Schlaufman K.C.
<Astrophys. J., 850, 179 (2017)>
=2017ApJ...850..179C 2017ApJ...850..179C
ADC_Keywords: Abundances; Equivalent widths; Stars, metal-deficient;
Spectra, optical
Keywords: galaxies: dwarf ; Galaxy: halo ; Galaxy: kinematics and dynamics ;
stars: abundances ; stars: Population II ; stars: Population III
Abstract:
The rapid neutron-capture or r-process is thought to produce the
majority of the heavy elements (Z>30) in extremely metal-poor stars.
The same process is also responsible for a significant fraction of the
heavy elements in the Sun. This universality of the r-process is one
of its characteristic features, as well as one of the most important
clues to its astrophysical origin. We report the discovery of an
extremely metal-poor field giant with [Sr,Ba/H]~-6.0 and
[Sr,Ba/Fe]~-3.0, the lowest abundances of strontium and barium
relative to iron ever observed. Despite its low abundances, the star
2MASS J151113.24-213003.0 has [Sr/Ba]=-0.11±0.14, therefore its
neutron-capture abundances are consistent with the main solar
r-process pattern that has [Sr/Ba]=-0.25. It has been suggested that
extremely low neutron-capture abundances are a characteristic of dwarf
galaxies, and we find that this star is on a highly eccentric orbit
with an apocenter ≳100kpc that lies in the disk of satellites in the
halo of the Milky Way. We show that other extremely metal-poor stars
with low [Sr,Ba/H] and [Sr,Ba/Fe] plus solar [Sr/Ba] tend to have
orbits with large apocenters, consistent with a dwarf galaxy origin
for this class of object. The nucleosynthesis event that produced the
neutron-capture elements in 2MASS J151113.24-213003.0 must produce
both strontium and barium together in the solar ratio. We exclude
contributions from the s-process in intermediate-mass asymptotic giant
branch or fast-rotating massive metal-poor stars, pair-instability
supernovae, the weak r-process, and neutron-star mergers. We argue
that the event was a Pop III or extreme Pop II core-collapse supernova
explosion.
Description:
We initially observed 2MASS J151113.24-213003.0 on 22 June 2014 using
the Magellan Inamori Kyocera Echelle (MIKE) spectrograph (R∼28000) on
the Magellan Clay Telescope at Las Campanas Observatory.
We observed 2MASS J151113.24-213003.0 with MIKE a second time during
the evening twilight of 2015 August 1. The analysis presented here is
based on those observations (R∼83000 in the blue and R∼65000 in the red).
Objects:
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RA (ICRS) DE Designation(s)
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15 11 13.24 -21 30 03.1 J151113.24-213003.0 = 2MASS J15111324-2130030
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 51 384 Individual line abundances of 2MASS J151113.24-213003.0
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/317 : The PPMXL Catalog (Roeser+ 2010)
I/320 : SPM 4.0 Catalog (Girard+, 2011)
I/339 : Hot Stuff for One Year (HSOY) (Altmann+, 2017)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/A+A/501/519 : Extremely metal-poor turnoff stars (Bonifacio+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)
J/ApJ/711/573 : Abundances in a halo stellar stream (Roederer+, 2010)
J/ApJ/749/77 : MW halo. III. Statistical abundances (Schlaufman+, 2012)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/771/67 : Abundances for 97 metal-poor stars. II. (Ishigaki+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)
J/A+A/571/A47 : Linelist of CH in stellar atmospheres (Masseron+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/797/13 : Abundances of bright metal-poor stars (Schlaufman+, 2014)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda [3566.3/7800.3] Wavelength in Angstroms
9- 14 A6 --- Species Species identifier
16- 20 F5.3 eV ExPot [0/9.2]? Lower excitation potential
22- 22 A1 --- Flag [s] s: Abundance derived by spectral synthesis
24- 29 F6.3 [-] log(gf) [-5.7/0.7]? Log oscillator strength
31- 35 F5.1 10-13m EW [4/203.7]? Equivalent width of Species (1)
37- 39 F3.1 10-13m E_EW [0.6/8.3]? Upper limit uncertainty in EW (1)
41- 43 F3.1 10-13m e_EW [0.8/6.1]? Lower limit uncertainty in EW (1)
45- 45 A1 --- l_log(X) Limit flag on log(X)
47- 51 F5.2 [Sun] log(X) [-3.7/7] Log abundance
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Note (1): In milli-Angstroms.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Jul-2018