J/ApJ/769/40 Potassium abundance in red giants of GCs (Carretta+, 2013)
Potassium in globular cluster stars: comparing normal clusters to the peculiar
cluster NGC 2419.
Carretta E., Gratton R.G., Bragaglia A., D'Orazi V., Lucatello S.,
Sollima A., Sneden C.
<Astrophys. J., 769, 40 (2013)>
=2013ApJ...769...40C 2013ApJ...769...40C
ADC_Keywords: Abundances ; Clusters, globular ; Stars, giant ; Equivalent widths
Keywords: globular clusters: general;
globular clusters: individual (NGC 6752, NGC 6121, NGC 1904,
NGC 2419, NGC 6397, NGC 104, NGC 7099);
stars: abundances; stars: evolution; stars: Population II
Abstract:
Two independent studies recently uncovered two distinct populations
among giants in the distant, massive globular cluster (GC) NGC 2419.
One of these populations has normal magnesium (Mg) and potassium (K)
abundances for halo stars: enhanced Mg and roughly solar K. The other
population has extremely depleted Mg and very enhanced K. To better
anchor the peculiar NGC 2419 chemical composition, we have
investigated the behavior of K in a few red giant branch stars in
NGC 6752, NGC 6121, NGC 1904, and ω Cen. To verify that the high
K abundances are intrinsic and not due to some atmospheric features in
giants, we also derived K abundances in less evolved turn-off and
subgiant stars of clusters 47 Tuc, NGC 6752, NGC 6397, and NGC 7099.
We normalized the K abundance as a function of the cluster metallicity
using 21 field stars analyzed in a homogeneous manner. For all GCs of
our sample, the stars lie in the K-Mg abundance plane on the same
locus occupied by the Mg-normal population in NGC 2419 and by field
stars. This holds for both giants and less-evolved stars. At present,
NGC 2419 seems unique among GCs.
Description:
Spectra for RGB stars are mainly from our program (ESO 085.D-0.205)
devoted to the study of Al abundances for a large sample of stars in
selected GCs (see Carretta et al. 2012, J/ApJ/750/L14). We acquired
fiber-fed UVES Red Arm high-resolution (R∼43000) spectra centered at
860nm and covering the spectral range approximatively from 6730 to
10150Å. From these spectra we only derive the K abundances for
stars in NGC 6752, M 4, and NGC 1904; the abundances of the other
elements discussed in the present paper for these giants were taken
from Carretta et al. (2009, J/A+A/505/139 and 2010, J/ApJ/712/L21).
Spectra for six giants in ω Cen and for all the less-evolved
stars are from the ESO Large Program 165.L-0263 (PI: Gratton).
Descriptions of the observations can be found in Gratton et al.
(2001A&A...369...87G 2001A&A...369...87G), Pancino et al. (2002ApJ...568L.101P 2002ApJ...568L.101P), and
Carretta et al. (2004A&A...416..925C 2004A&A...416..925C, 2005A&A...433..597C 2005A&A...433..597C). The
spectra for M 30 were acquired with the same setup of the other
clusters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 77 Relevant data for stars in the 7 program clusters
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/572/A108 : 47 Tuc red giants chemical composition (Thygesen+, 2014)
J/A+A/550/A34 : Abundances of red giants in M4 and 47 Tuc (Carretta+, 2013)
J/ApJ/760/86 : Equivalent widths for 13 NGC2419 RGB stars (Cohen+, 2012)
J/ApJ/750/L14 : Abundances of red giants in NGC 6752 (Carretta+, 2012)
J/ApJ/742/37 : Abundances of six RGB stars in M22 (Roederer+, 2011)
J/ApJ/740/60 : EWs for NGC2419 and NGC7099 RGB stars (Cohen+, 2011)
J/AJ/141/81 : NGC 2419 variable star population (Di Criscienzo+, 2011)
J/A+A/527/A148 : NGC6397 red giants chemical composition (Lind+, 2011)
J/ApJ/712/L21 : Calcium abundances in 17 globular clusters (Carretta+, 2010)
J/A+A/520/A95 : Abundances of red giants in M54 and Sgr dSph (Carretta+, 2010)
J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)
J/ApJ/698/2048 : Abundances of red giants in ω Cen (Johnson+, 2009)
J/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)
J/A+A/464/927 : Abundances of red giants in NGC 6752 (Carretta+, 2007)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star designation
11- 13 A3 --- --- [NGC]
15- 18 I4 --- NGC Cluster name (GC)
20- 22 A3 --- Evol Evolutionary status: TO=turnoff, SGB=subgiant,
RGB=red giant branch.
24- 26 I3 --- S/N [21/184] Signal-to-noise ratio
28- 31 I4 K Teff [3900/6476] Temperature
33- 36 F4.2 [cm/s2] logg [0.7/4.3] log of the surface gravity
38- 42 F5.2 [Sun] [Fe/H] [-2.4/-0.4] Iron abundance
44- 47 F4.2 km/s vt [0/2] Microtubulent velocity ξ
49- 53 F5.1 10-13m EW [6/296] K line (7698) equivalent width (mÅ)
55- 59 F5.2 [Sun] [K/Fe] Potassium abundance (NLTE)
61- 65 F5.2 [Sun] [Mg/Fe] ? Magnesium abundance
67- 71 F5.2 [Sun] [Al/Fe] ? Aluminum abundance
73 A1 --- refPA Ref for atmospheric parameters (2)
75- 77 A3 --- refA Reference(s) for abundances (3)
79- 80 I2 h RAh Hour of right ascension (J2000) (4)
82- 83 I2 min RAm Minute of right ascension (J2000)
85- 90 F6.3 s RAs Second of right ascension (J2000)
92 A1 --- DE- Sign of declination (J2000) (4)
93- 94 I2 deg DEd Degree of declination (J2000) (4)
96- 97 I2 arcmin DEm Arcminute of declination (J2000)
99-104 F6.3 arcsec DEs Arcsecond of declination (J2000)
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Note (2): Reference as follows:
a = Carretta et al. (2004A&A...416..925C 2004A&A...416..925C);
b = Carretta et al. (2009, J/A+A/505/139);
c = Pancino et al. (2002ApJ...568L.101P 2002ApJ...568L.101P);
d = Gratton et al. (2001A&A...369...87G 2001A&A...369...87G);
e = unpublished/this work (<[CGB2013] NGC 7099 @{Star}> in Simbad);
f = Gratton et al. (2000, J/A+A/354/169).
Note (3): Reference as follows:
1 = Carretta et al. (2004A&A...416..925C 2004A&A...416..925C: Mg, Al);
2 = Carretta et al. (2009, J/A+A/505/139: Mg, Al);
3 = Pancino et al. (2002ApJ...568L.101P 2002ApJ...568L.101P: Fe);
4 = this work (Mg, Al);
5 = Gratton et al. (2001A&A...369...87G 2001A&A...369...87G);
6 = Carretta et al. (2005A&A...433..597C 2005A&A...433..597C)
Note (4): Coordinates sent by the author (see acknowledgement section),
added at CDS.
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Acknowledgement:
Eugenio Carretta (Bologna Observatory)
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Dec-2014