J/ApJ/846/23 High-resolution spectra of 9 RGB stars in NGC6681 (O'Malley+, 2017)
High-resolution spectroscopic abundances of red giant branch stars in NGC 6681.
O'Malley E.M., Knaizev A., McWilliam A., Chaboyer B.
<Astrophys. J., 846, 23 (2017)>
=2017ApJ...846...23O 2017ApJ...846...23O
ADC_Keywords: Stars, giant ; Abundances ; Spectra, optical ; Radial velocities ;
Equivalent widths
Keywords: globular clusters: individual: NGC 6681 (M70); methods: observational;
stars: abundances; stars: fundamental parameters
Abstract:
We obtain high-resolution spectra of nine red giant branch stars in
NGC 6681 and perform the first detailed abundance analysis of stars in
this cluster. We confirm cluster membership for these stars based on
consistent radial velocities of 214.5±3.7km/s and find a mean
[Fe/H]=-1.63±0.07dex and [α/Fe]=0.42±0.11dex. Additionally,
we confirm the existence of a Na-O anti-correlation in NGC 6681 and
identify two populations of stars with unique abundance trends. With
the use of HST photometry from Sarajedini+ (2007AJ....133.1658S 2007AJ....133.1658S) and
Piotto+ (2015AJ....149...91P 2015AJ....149...91P) we are able to identify these two
populations as discrete sequences in the cluster CMD. Although we
cannot confirm the nature of the polluter stars responsible for the
abundance differences in these populations, these results do help put
constraints on possible polluter candidates.
Description:
We obtained high-resolution spectra of nine RGB stars in NGC 6681 with
reasonably high signal-to-noise ratios (S/N∼100) using the Magellan
Inamori Kyocera Echelle (MIKE) double spectrograph on the 6.5m
Magellan Clay II telescope at Las Campanas Observatory (R∼58000 for
the red side 4825-9155Å and R∼70000 for the blue side
3315-5000Å) and the High Resolution Spectrograph (HRS) on the 11m
South African Large Telescope (SALT) at the South African Astronomical
Observatory. Our HRS data cover the wavelength range of 3700-5550Å
on the blue beam and 5550-8900Å on the red beam (R∼67000-74000).
With the combination of the spectroscopic abundances found in this
study and photometric data available in multiple HST filters
(Sarajedini+ 2007AJ....133.1658S 2007AJ....133.1658S ; Piotto+ 2015AJ....149...91P 2015AJ....149...91P and
Soto+ 2017AJ....153...19S 2017AJ....153...19S), we are able to form a nearly complete
picture of the nature of the multiple stellar populations in NGC 6681.
Objects:
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RA (ICRS) DE Designation(s) (HRV)
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18 43 12.76 -32 17 31.6 NGC 6681 = M 70 (HRV=214)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 87 10 Magellan and SALT observations of NGC 6681 RGBs
table2.dat 88 295 Line list for abundance analysis without
hyperfine splitting (HFS) lines
table3.dat 43 10 Comparison of photometric and spectroscopic
stellar atmosphere parameters
table4.dat 27 297 HFS-elements line list
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
III/184 : 3rd Bibliog. Cat. of Stellar Radial Vel. (Barbier-Brossat+, 1994)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/271 : Properties of Galactic Globular Clusters (Francis+, 2014)
J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)
J/A+A/356/238 : Atmospheric param. in metal-poor stars. III. (Carretta+ 2000)
J/A+A/359/347 : Reddening in open and globular clusters (Dutra+, 2000)
J/AJ/120/1841 : Abundances & Kinematics of Halo & Disk Stars (Fulbright 2000)
J/A+AS/145/451 : Nearby globular clusters photometric cat. (Rosenberg+, 2000)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/A+A/435/657 : Equivalent widths of 5 giants in 47 Tuc (Alves-Brito+, 2005)
J/AJ/131/1766 : Abundances and equivalent widths in NGC 2808 (Carretta, 2006)
J/ApJ/638/1018 : Equivalent widths for giant stars in M13 & M71 (Yong+, 2006)
J/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)
J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/A+A/520/A95 : Abundances of red giants in M54 & Sgr dSph (Carretta+, 2010)
J/A+A/533/A69 : Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)
J/A+A/534/A9 : Synthetic spectra of galactic GCs (Sbordone+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/A+A/540/A27 : Spectroscopy in Galactic globular clusters (Saviane+, 2012)
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013)
J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014)
J/ApJ/787/10 : Solar s-process contribution with GCE model (Bisterzo+, 2014)
J/A+A/572/A108 : 47 Tuc red giants chemical composition (Thygesen+, 2014)
J/MNRAS/450/815 : Red giants in NGC 5286 (Marino+, 2015)
J/AJ/149/153 : Abundances of red giants in 10 GCs (Meszaros+, 2015)
J/A+A/587/A124 : Metal-poor stars towards the Galactic bulge (Koch+, 2016)
J/A+A/589/A115 : Na and Al abundances of 1303 stars (Smiljanic+, 2016)
J/ApJ/835/152 : HST FGS-1r plx for 8 metal-poor stars (Chaboyer+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID RGB star number
7 A1 --- f_ID [b] Flag on ID (1)
9- 16 F8.4 deg RAdeg [280.7/280.9] Right ascension (J2000)
18- 25 F8.4 deg DEdeg [-32.4/-32.2] Declination (J2000)
27- 34 A8 --- Tel Telescope
36- 46 A11 "Y/M/D" Date UT date of observation
47 A1 --- --- [-]
48- 58 A11 "Y/M/D" Date2 Second date of observation if any
60- 64 I5 s Exp [3200/14000] Exposure time
66- 70 F5.1 pix-1 S/N [76.4/125.5] Signal to noise ratio measured
from rms scatter at blaze peak near 6740Å
72- 76 F5.2 mag Vmag [12.7/15.2] V-band magnitude converted from
HST F606W
78- 81 F4.2 mag V-I [1.1/1.8] V-I color index
83- 87 F5.1 km/s HRV [209.9/220] Heliocentric radial velocity
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Note (1):
b = Pristine population stars, which is discussed in more detail
in Section 4.2.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 0.1nm lambda [4399.7/7797.6] Wavelength of spectral line (1)
9- 12 F4.1 --- Ion [8/63.1] Ion identifier (G1)
14- 18 F5.3 eV EP [0/5.9] Excitation Potential
20- 26 F7.3 [-] log(gf) [-10.3/0.6] Oscillator strength
28 A1 --- Ref Reference for line (2)
30- 34 F5.1 0.1nm EW4025S [3.7/183.1]? EW of lines in 4025 (1)
36- 40 F5.1 0.1nm EW7247M [1.2/167]? EW of lines in 7247 (1)
42- 46 F5.1 0.1nm EW8125M [1.3/150.3]? EW of lines in 8125 (1)
48- 52 F5.1 0.1nm EW10683S [3.8/240.8]? EW of lines in 10683 (1)
54- 58 F5.1 0.1nm EW11719S [4.4/287.4]? EW of lines in 11719 (1)
60- 64 F5.1 0.1nm EW12591M [1.3/218.6]? EW of lines in 12591
from Magellan (1)
66- 70 F5.1 0.1nm EW12591S [2.6/217.4]? EW of lines in 12591 from SALT (1)
72- 76 F5.1 0.1nm EW12720M [1.8/188.5]? EW of lines in 12720 (1)
78- 82 F5.1 0.1nm EW30380S [3/222.6]? EW of lines in 30380 (1)
84- 88 F5.1 0.1nm EW30847M [2/159.2]? EW of lines on 30847 (1)
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Note (1): In units of Angstroms.
Note (2): Reference as follows:
a = Gratton et al. (2003, J/A+A/404/187);
b = Yong et al. (2003A&A...402..985Y 2003A&A...402..985Y);
c = Yong et al. (2005A&A...438..875Y 2005A&A...438..875Y);
d = Alevs-Brito et al. (2005, J/A+A/435/657);
e = Marino et al. (2015, J/MNRAS/450/815);
f = Koch et al. (2016, J/A+A/587/A124).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID RGB star number
7- 14 A8 --- Tel Telescope
16- 19 I4 K TeffP [3951/4676] Photometric effective temperature
21- 24 F4.2 [cm/s2] loggP [0.7/2.5] Photometric surface gravity
26- 28 F3.1 km/s VtP [2] Photometric microturbulent velocity ξ
30- 33 I4 K Teff [4150/4675] Spectroscopic effective temperature
35- 38 F4.2 [cm/s2] logg [0.6/1.6] Spectroscopic surface gravity
40- 43 F4.2 km/s Vt [1.6/3] Spectroscopic microturbulent velocity ξ
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda [4754/7417.5] Wavelength of spectral line
in units of Angstroms
10- 13 F4.1 --- Ion [21.1/63.1] Ion identifier (G1)
15- 19 F5.3 eV EP [0/4.1] Excitation Potential
21- 27 F7.4 [-] log(gf) [-5.1/0.6] Oscillator strength
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Global note:
Note (G1): Where #.0 indicates neutral, #.1 singly ionized, etc.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 11-Apr-2018