J/ApJ/870/122 Spectroscopy of low-metallicity star candidates (Placco+, 2019)
The R-Process Alliance: spectroscopic follow-up of low-metallicity star
candidates from the Best & Brightest Survey.
Placco V.M., Santucci R.M., Beers T.C., Chaname J., Sepulveda M.P.,
Coronado J., Rossi S., Lee Y.S., Starkenburg E., Youakim K., Barrientos M.,
Ezzeddine R., Frebel A., Hansen T.T., Holmbeck E.M., Ji A.P.,
Rasmussen K.C., Roederer I.U., Sakari C.M., Whitten D.D.
<Astrophys. J., 870, 122-122 (2019)>
=2019ApJ...870..122P 2019ApJ...870..122P (SIMBAD/NED BibCode)
ADC_Keywords: Abundances; Stars, carbon; Stars, population II;
Spectroscopy; Reddening; Photometry, UBV; Photometry, infrared;
Stars, metal-deficient
Keywords: Galaxy: halo; stars: abundances; stars: atmospheres; stars: carbon
stars: Population II; techniques: spectroscopic
Abstract:
We present results from an observing campaign to identify
low-metallicity stars in the Best & Brightest Survey. From
medium-resolution (R∼1200-2000) spectroscopy of 857 candidates, we
estimate the stellar atmospheric parameters (Teff, logg, and
[Fe/H]), as well as carbon and α-element abundances. We find
that 69% of the observed stars have [Fe/H]≤-1.0, 39% have
[Fe/H]≤-2.0, and 2% have [Fe/H]≤-3.0. There are also 133
carbon-enhanced metal-poor (CEMP) stars in this sample, with 97 CEMP
Group I and 36 CEMP Group II stars identified in the A(C) versus
[Fe/H] diagram. A subset of the confirmed low-metallicity stars were
followed-up with high-resolution spectroscopy, as part of the
R-process Alliance, with the goal of identifying new highly and
moderately r-process-enhanced stars. Comparison between the stellar
atmospheric parameters estimated in this work and from high-resolution
spectroscopy exhibit good agreement, confirming our expectation that
medium-resolution observing campaigns are an effective way of
selecting interesting stars for further, more targeted, efforts.
Description:
This paper reports on the medium-resolution (R∼1200-2000)
spectroscopic follow-up campaign, conducted from semesters 2015B to
2017A, of 857 low-metallicity star candidates selected from the Best &
Brightest Survey (B&B survey; e.g. Schlaufman & Casey 2014, J/ApJ/797/13).
Spectroscopic data were gathered using five telescope/instrument
setups:
Gemini North and South Telescopes: 474 stars were observed with the
twin 8.1m Gemini North (134 stars) and Gemini South (340 stars)
telescopes and the GMOS (Gemini Multi-Object Spectrographs)
instruments. In both cases, we used the B600l/mm grating (G5323 for
GMOS South and G5307 for GMOS North) and a 1,0" slit, resulting in a
wavelength coverage in the range [3200:5800]Å at resolving power
R∼2000.
ESO New Technology Telescope: 256 stars were observed with the 3.58m
New Technology Telescope (NTT), located at La Silla Observatory, part
of the European Southern Observatory. We used the EFOSC-2 (ESO Faint
Object Spectrograph and Camera v.2) instrument with Grism#7 (600gr/mm)
and a 1,0" slit, resulting in a wavelength coverage in the range
[3300:5100]Å at resolving power R∼1200.
KPNO Mayall Telescope: 73 stars were observed with the 4m Mayall
telescope, located at Kitt Peak National Observatory, using the KOSMOS
(Kitt Peak Ohio State Multi-Object Spectrograph) instrument. We used
the 600l/mm grating, the blue setting, and a 0,9" slit, resulting in a
wavelength coverage in the range [3600:6300]Å at resolving power
R∼1800.
SOAR Telescope: 54 stars were observed with the 4.1m Southern
Astrophysical Research (SOAR) telescope. The Goodman Spectrograph was
used with the 600l/mm grating, the blue setting, and a 1,0" slit,
resulting in a wavelength coverage in the range [3600:6200]Å at
resolving power R∼1500.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 857 Observing details
table2.dat 95 857 Coordinates, magnitudes, color indices, and reddening
estimates
table3.dat 66 857 *Stellar parameters and abundances from the n-SSPP
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Note on table3.dat: Stellar atmospheric parameters (Teff, logg, and [Fe/H]),
as well as carbonicity ([C/Fe]) and α-to-iron ratios
([α/Fe]), were determined using the n-SSPP (Beers+ 2014, J/ApJ/794/58
and 2017, J/ApJ/835/81), a modified version of the SEGUE Stellar
Parameter Pipeline (SSPP; Lee+ 2008AJ....136.2022L 2008AJ....136.2022L).
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
III/272 : RAVE 4th data release (Kordopatis+, 2013)
II/328 : AllWISE Data Release (Cutri+, 2013)
J/ApJ/562/528 : Teff and log(g) of low-metallicity stars (Snider+, 2001)
J/A+A/422/527 : Metal-poor star uvby-beta photometry. X. (Schuster+, 2004)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/PASP/121/117 : Fe & Ti abundances of 12 low-metallicity stars (Woolf+, 2009)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/AJ/141/90 : SEGUE stellar parameter pipeline. V. (Lee+, 2011)
J/ApJ/762/27 : Most metal-poor stars. III. 86 [Fe/H]≤-3.0 stars (Yong+, 2013)
J/ApJ/773/33 : Chem.analysis of the metal-poor subgiant BD+44493 (Ito+, 2013)
J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)
J/ApJ/794/58 : Metal-poor stars in the thick disk of the Galaxy (Beers+, 2014)
J/ApJ/797/13 : Abundances of bright metal-poor stars (Schlaufman+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
J/ApJ/833/20 : Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+, 2016)
J/A+A/608/A46 : Constraining cosmic scatter (Reggiani+, 2017)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/ApJ/850/179 : 2MASS J15111324-2130030 metal-poor star abundance (Casey+,2017)
J/AJ/155/256 : Spectro. validation of RAVE metal-poor stars (Placco+, 2018)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/ApJ/862/174 : Spectroscopy obs. of RAVE J094921.8-161722 (Gull+, 2018)
J/ApJ/868/110 : R-Process Alliance: 1st release in Galactic halo (Sakari+,2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- WISEA Star Name (JHHMMSS.ss+DDMMSS.s)
21- 30 A10 "Y/M/D" Date UTC date of observation
32- 43 A12 --- Tel Telescope
45- 51 A7 --- Inst Instrument (1)
53- 66 A14 --- PID Proposal ID
69- 72 I4 s Exp [130/1500] Exposure duration
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Note (1): Instrument as follows:
EFOSC2 = the ESO New Technology Telescope (NTT) / Faint Object Spectrograph
and Camera v.2 (256 occurrences)
GMOS-N = the Gemini-North 8.1m telescope and the Gemini Multi-Object
Spectrograph (134 occurrences)
GMOS-S = Gemini-South (340 occurrences)
Goodman = the 4.1m Southern Astrophysical Research (SOAR) telescope
(Prop. ID: 2017A-0016) / Goodman spectrograph (54 occurrences)
KOSMOS = the 4m Mayall telescope / Kitt Peak Ohio State Multi-Object
Spectrograph (73 occurrences).
See the "Description" section above for further details.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- WISEA Star Name (JHHMMSS.ss+DDMMSS.s)
21- 22 I2 h RAh Hour of Right Ascension (J2000)
24- 25 I2 min RAm Minute of Right Ascension (J2000)
27- 31 F5.2 s RAs Second of Right Ascension (J2000)
33- 33 A1 --- DE- Sign of the Declination (J2000)
34- 35 I2 deg DEd Degree of Declination (J2000)
37- 38 I2 arcmin DEm Arcminute of Declination (J2000)
40- 43 F4.1 arcsec DEs Arcsecond of Declination (J2000)
45- 51 F7.3 deg GLON [0.1/360] Galactic longitude, decimal degrees
53- 59 F7.3 deg GLAT [-84/70] Galactic latitude, decimal degrees
61- 66 F6.3 mag Vmag [12/15]? APASS V-band magnitude (2)
68- 72 F5.3 mag B-V [0.23/1.3]? APASS B-V color index (2)
74- 79 F6.3 mag Jmag [9.9/16] 2MASS J-band magnitude (3)
81- 85 F5.3 mag J-K [0.37/0.79] 2MASS J-Ks color index (3)
87- 89 A3 --- Qflg 2MASS photometric quality flag (3)
91- 95 F5.3 mag E(B-V) [0.006/4.9] Reddening estimate (4)
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Note (2): B and V magnitudes from the AAVSO Photometric All-Sky Survey, APASS;
Henden & Munari (2014CoSka..43..518H 2014CoSka..43..518H)
Note (3): J and K magnitudes and photometric quality flags from the Two Micron
All Sky Survey, 2MASS (Cutri+, 2003, II/246).
Note (4): Reddening estimates from the dust maps of
Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- WISEA Star name (JHHMMSS.ss+DDMMSS.s)
21- 24 I4 K Teff [4393/8985]? Stellar effective temperature
26- 29 F4.2 [cm/s2] logg [0.2/5]? Stellar log surface gravity
31- 35 F5.2 --- [Fe/H] [-3.7/0.11]? Stellar metallicity
37- 41 F5.2 --- [C/Fe] [-1.1/2.6]? Carbon-to-iron ratio
43- 47 F5.2 --- d[C/Fe] [0/0.77]? Carbon correction (5)
49- 53 F5.2 --- c[C/Fe] [-1.1/2.6]? Corrected carbon-to-iron ratio
55- 60 F6.2 --- A(C) [4.9/11]? Corrected absolute carbon abundance
(A(C)=log(NC/NH)+12)
62- 66 F5.2 --- [A/Fe] [-0.17/0.6]? Alpha element-to-iron ratio
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Note (5): Correction from Placco+ (2014, J/ApJ/797/21).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS] 23-Jan-2020