J/ApJ/858/92 RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
The R-Process Alliance: First Release from the Southern Search for
r-Process-Enhanced Stars in the Galactic Halo.
Hansen T.T., Holmbeck E.M., Beers T.C., Placco V.M., Roederer I.U.,
Frebel A., Sakari C.M., Simon J.D., Thompson I.B.
<Astrophys. J. 858, 92 (2018)>
=2018ApJ...858...92H 2018ApJ...858...92H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, population II ; Stars, metal-deficient ; Abundances ;
Equivalent widths
Keywords: stars: abundances - stars: chemically peculiar - stars: Population II
Abstract:
The recent detection of a binary neutron star merger and the clear
evidence for the decay of radioactive material observed in this event
have, after 60 years of effort, provided an astrophysical site for the
rapid neutron- capture (r-) process which is responsible for the
production of the heaviest elements in our universe. However,
observations of metal-poor stars with highly-enhanced r-process
elements have revealed abundance patterns suggesting that multiple
sites may be involved. To address this issue and to advance our
understanding of the r-process, we have initiated an extensive search
for bright (V<13.5), very metal-poor ([Fe/H]←2) stars in the Milky
Way halo exhibiting strongly-enhanced r-process signatures. This paper
presents the first sample collected in the southern hemisphere using
the echelle spectrograph on du Pont 2.5m telescope at Las Campanas
Observatory. We have observed and analyzed 107 stars with
-3.13<[Fe/H]←0.79. Of those, 12 stars are strongly enhanced in heavy
r-process elements (r-II), 42 stars show moderate enhancements of
heavy r-process material (r-I), and 20 stars exhibit low abundances of
the heavy r-process elements and higher abundances of the light
r-process elements relative to the heavy ones (limited-r). This search
is more successful at finding r- process-enhanced stars compared to
previous searches, primarily due to a refined target-selection
procedure.
Description:
Complete equivalent width measurements of FeI and FeII lines for all
stars in our sample used to derive spectroscopic stellar parameters.
Also included are the derived abundances for each line.
The first dataset on this program in the southern hemisphere was
obtained during six nights in 2016 August, with the Echelle
spectrograph on the du Pont 2.5m telescope at the Las Campanas
Observatory. During this run, we obtained spectra for 107 stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 115 115 Observation log for the 107 stars
ew_all.dat 63 10688 Fe I and Fe II equivalent width measurements
(Table 3 of the paper)
table4.dat 50 107 Stellar parameters
table5.dat 81 107 Abundances
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
III/279 : RAVE 5th data release (Kunder+, 2017)
J/AJ/90/2089 : Stars of very low metal abundance. I (Beers+, 1985)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/ApJ/617/1091 : La and Eu abundances in 85 stars (Simmerer+, 2004)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/AJ/130/2804 : Carbon abundances in metal-poor stars (Rossi+, 2005)
J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)
J/ApJS/168/128 : UBVRcIc photometry of FHB and metal-poor stars (Beers+, 2007)
J/A+A/484/721 : HES survey. IV. Candidate metal-poor stars (Christlieb+, 2008)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
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/775/L27 : Chemical abundances in a metal-poor RGB star (Johnson+, 2013)
J/ApJ/794/58 : Metal-poor stars in the Galaxy thick disk (Beers+, 2014)
J/A+A/569/A43 : HE 2252-4225 abundance analysis (Mashonkina+, 2014)
J/A+A/571/A47 : Extensive CH linelist in stellar atmospheres (Masseron+, 2014)
J/AJ/148/81 : APASS BVgri photometry of RAVE stars. I. Data (Munari+, 2014)
J/ApJS/211/5 : Improved line data for the Swan system 12C13C (Ram+, 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/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
J/ApJ/807/171 : SkyMapper Survey metal-poor star spectrosc. (Jacobson+, 2015)
J/ApJ/830/93 : Abundances of Ret II brightest red giant members (Ji+, 2016)
J/AJ/151/82 : 4 brightest red giants in Ret 2 (Roederer+, 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 the brightest member of Tuc III (Hansen+, 2017)
J/ApJ/844/18 : RAVE J203843.2-002333 spectroscopy (Placco+, 2017)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS Stellar identifier (JHHMMSSss+DDMMSSs) (G1)
19- 20 I2 h RAh [0/23] Hour of Right Ascension (J2000)
22- 23 I2 min RAm Minute of Right Ascension (J2000)
25- 28 F4.1 s RAs Second of Right Ascension (J2000)
30 A1 --- DE- Sign of the Declination (J2000)
31- 32 I2 deg DEd [0/75] Degree of Declination (J2000)
34- 35 I2 arcmin DEm Arcminute of Declination (J2000)
37- 40 F4.1 arcsec DEs Arcsecond of Declination (J2000)
42- 45 F4.1 mag Vmag [9/13.6] Apparent V band magnitude
47- 57 F11.5 d MJD [57605.4/57611] Modified Julian Date
59- 62 I4 s Exp [296/4200] Exposure time
64- 65 I2 --- S/N [17/80] Signal-to-Noise at 4129A
67- 73 F7.2 km/s RVel [-278.1/432.2] Heliocentric radial velocity
75- 78 F4.2 km/s e_RVel [0.08/2.2] Uncertainty in RVel
80- 87 A8 --- r_Vmag Source of Vmag (1)
89-115 A27 --- OID Other identifier
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Note (1): Reference as follows:
RAVE DR5 = Munari et al. (2014, J/AJ/148/81).
B&B = Henden & Munari (2014CoSka..43..518H 2014CoSka..43..518H).
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Byte-by-byte Description of file: ew_all.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS identifier (JHHMMSSss+DDMMSSs) (G1)
21- 25 A5 --- Ion Atomic species (Fe I or Fe II)
30- 36 F7.2 0.1nm lambda [3878/8689] Transition wavelength
(in Angstrom units)
39- 42 F4.2 eV EP [0/5] Excitation potential
45- 49 F5.2 [-] loggf [-6/0.7] Log of oscillator strength
52- 57 F6.2 10-13m EW [1.4/217.5] Measured equivalent width
(in milli-Angstrom units)
60- 63 F4.2 [Sun] A [3.7/7.1] Derived abundance (loge)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- 2MASS Stellar identifier (JHHMMSSss+DDMMSSs)
19- 22 I4 K Teff [4250/6311] Effective temperature
24- 27 F4.2 [cm/s2] log(g) [0.1/4.6] log surface gravity
29- 33 F5.2 [Sun] [Fe/H] [-3.2/-0.7] Metallicity
35- 38 F4.2 [Sun] e_[Fe/H] [0.09/0.3] Uncertainty in [Fe/H]
40- 42 I3 --- N(FeI) [28/140] Number of Fe I lines used
44- 45 I2 --- N(FeII) [6/27] Number of Fe II lines used
47- 50 F4.2 km/s Vt [0.7/3] Microturbulent velocity
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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- 17 A17 --- 2MASS Stellar identifier (JHHMMSSss+DDMMSSs)
19- 23 F5.2 [Sun] [Fe/H]n [-3.2/-0.7] log Fe/H number abundance ratio
25 A1 --- l_[C/Fe] Limit flag on [C/Fe]
27- 31 F5.2 [Sun] [C/Fe] [-1.2/2] log C/Fe number abundance ratio
33 A1 --- l_[Sr/Fe] Limit flag on [C/Fe]
35- 39 F5.2 [Sun] [Sr/Fe] [-2.5/2] log Sr/Fe number abundance ratio
41 A1 --- l_[Ba/Fe] Limit flag on [C/Fe]
43- 47 F5.2 [Sun] [Ba/Fe] [-1.7/2.3] log Ba/Fe number abundance ratio
49 A1 --- l_[Eu/Fe] Limit flag on [C/Fe]
51- 55 F5.2 [Sun] [Eu/Fe] [-0.4/2.1] log Eu/Fe number abundance ratio
57 A1 --- l_[Ba/Eu] Limit flag on [C/Fe]
59- 63 F5.2 [Sun] [Ba/Eu] [-2.2/1]? log Ba/Eu number abundance ratio
65 A1 --- l_[Sr/Ba] Limit flag on [C/Fe]
67- 71 F5.2 [Sun] [Sr/Ba] [-1.7/1.3] log Sr/Ba number abundance ratio
73- 81 A9 --- sClass Sub classification (1)
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Note (1): sub-classification as follows:
CEMP-r = carbon-enhanced metal-poor r-process-enhanced stars (3 occurrences)
CEMP-s = stars enhanced in both C and s-process elements (4 occurrences)
r-I = moderately enhanced stars with +0.3≤[Eu/Fe]≤+1.0 (39 occurrences)
r-II = highly enhanced stars with [Eu/Fe]>+1.0
(Beers & Christlieb 2005ARA&A..43..531B 2005ARA&A..43..531B) (12 occurrences)
limited-r = Stars which exhibits low abundances of the heavy r-process
elements ([Eu/Fe]<+0.3), and higher abundances of the light
r-process elements, such as Strontium (Sr; Z=38), relative to the
heavy r-process elements ([Sr/Ba]>+0.5). These stars display the
signature of an r-process that is limited by a small number of
neutrons, with the consequence of producing primarily light
r-process elements (see review by Frebel 2018, ARNPS submitted)
(20 occurrences).
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Global notes:
Note (G1):
In table 2 and ew_all (Table 3), 3 misprints were corrected by CDS:
2MASS J19173310-6628544 is J19173310-6628545,
2MASS J20165358-0503593 is J20165357-0503592 and
2MASS J21091825-1310066 is J21091825-1310062
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History:
ew_all.dat sent by Erika Holmbeck
12-Jun-2018: Insert into VizieR
29-Mar-2019: Tables 2, 4 and 5 added from electronic version of the journal
Acknowledgements:
Erika Holmbeck, eholmbec(at)nd.edu
(End) Patricia Vannier, Emmanuelle Perret [CDS] 23-Mar-2018