2015A&A...573A..92G

Query : 2015A&A...573A..92G

2015A&A...573A..92G - Astronomy and Astrophysics, volume 573A, 92-92 (2015/1-1)

The Na-O anticorrelation in horizontal branch stars. V. NGC 6723.

GRATTON R.G., LUCATELLO S., SOLLIMA A., CARRETTA E., BRAGAGLIA A., MOMANY Y., D'ORAZI V., SALARIS M., CASSISI S. and STETSON P.B.

Abstract (from CDS):

We used FLAMES+GIRAFFE (Medusa mode) at the VLT to obtain moderately high resolution spectra for 30 red horizontal branch (RHB) stars, 4 RR Lyrae variables, and 17 blue horizontal branch (BHB) stars in the low-concentration, moderately metal-rich globular cluster NGC 6723 ([Fe/H]=-1.22±0.08 from our present sample). The spectra were optimized to derive O and Na abundances. In addition, we obtained abundances for other elements, including N, Fe, Mg, Ca, Ni, and Ba. We used these data to discuss the evidence of a connection between the distribution of stars along the horizontal branch (HB) and the multiple populations that are typically present in globular clusters. We found that all RHB and most (13 out of 17) BHB stars are O-rich, Na-poor, and N-poor; these stars probably belong to the first stellar generation in this cluster. Only the four warmest observed stars are (moderately) O-poor, Na-rich, and N-rich, and they probably belong to the second generation. While our sample is not fully representative of the whole HB population in NGC 6723, our data suggest that in this cluster only HB stars warmer than ∼9000K, that is one fourth of the total, belong to the second generation, if at all. Since in many other clusters this fraction is about two thirds, we conclude that the fraction of first/second generation in globular clusters may be strongly variable. In addition, the wide range in colour of chemically homogeneous first-generation HB stars requires a considerable spread in mass loss (>0.10M☉). The reason for this spread is yet to be understood. Finally, we found a high Ba abundance, with a statistically significant radial abundance gradient.

Abstract Copyright: ∼

Journal keyword(s): stars: abundances - stars: Population II - globular clusters: general - globular clusters: individual: NGC 6723 - stars: evolution

VizieR on-line data: <Available at CDS (J/A+A/573/A92): table2.dat table3.dat table5.dat table7.dat table8.dat>

Nomenclature: Tables 2-3,5,7-8): [GLS2015] NNNNN N=51 among (Nos 32170-77469).

Simbad objects: 75

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Number of rows : 75
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3916 0
2 NGC 288 GlC 00 52 45.24 -26 34 57.4   10 8.13     ~ 1041 0
3 NAME Fornax Dwarf Spheroidal G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1743 1
4 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7065 0
5 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1429 0
6 M 79 GlC 05 24 10.59 -24 31 27.3     8.16     ~ 817 0
7 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1419 0
8 M 68 GlC 12 39 27.98 -26 44 38.6     7.96     ~ 997 0
9 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2478 0
10 M 5 GlC 15 18 33.22 +02 04 51.7     5.95     ~ 1977 0
11 M 80 GlC 16 17 02.41 -22 58 33.9           ~ 715 0
12 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1849 0
13 M 107 GlC 16 32 31.86 -13 03 13.6           ~ 786 0
14 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2192 0
15 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2115 0
16 NGC 6388 GlC 17 36 17.461 -44 44 08.34           ~ 913 1
17 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1975 0
18 M 22 GlC 18 36 23.94 -23 54 17.1           ~ 1378 0
19 2MASS J18591261-3637319 HB* 18 59 12.6260501808 -36 37 31.938845232   16.141 15.474     ~ 1 0
20 2MASS J18591595-3637229 HB* 18 59 15.9541609224 -36 37 22.979622432   16.116 15.467     ~ 1 0
21 2MASS J18591688-3635471 HB* 18 59 16.8921345744 -36 35 47.100810948   16.122 15.526     ~ 1 0
22 2MASS J18591900-3640284 HB* 18 59 19.0065227664 -36 40 28.445063376   15.515 15.508     ~ 1 0
23 2MASS J18591936-3637373 HB* 18 59 19.3656996168 -36 37 37.287435864   15.553 15.459     ~ 1 0
24 2MASS J18592053-3636150 HB* 18 59 20.5335790224 -36 36 15.042052872   15.618 15.401     ~ 1 0
25 2MASS J18592481-3637111 HB* 18 59 24.8136626712 -36 37 11.144358876   16.059 15.473     ~ 1 0
26 [GLS2015] 42553 HB* 18 59 25.506 -36 34 09.36   16.100 15.488     ~ 1 0
27 2MASS J18592575-3634244 HB* 18 59 25.7572031208 -36 34 24.325180356   16.055 15.447     ~ 1 0
28 2MASS J18592618-3636507 HB* 18 59 26.1806467728 -36 36 50.648497596   16.067 15.479     ~ 1 0
29 2MASS J18592696-3640011 HB* 18 59 26.9616391152 -36 40 01.067144448   16.155 15.530     ~ 1 0
30 [GLS2015] 44646 HB* 18 59 27.11 -36 38 11.3   15.557 15.483     ~ 1 0
31 Cl* NGC 6723 SAW V22 RR* 18 59 27.3864329634 -36 37 17.372328209   15.848 15.511     ~ 4 0
32 2MASS J18592792-3639339 HB* 18 59 27.9225905448 -36 39 33.901472664   15.552 15.419     ~ 1 0
33 [GLS2015] 46519 HB* 18 59 28.370 -36 38 14.43   16.069 15.456     ~ 1 0
34 [GLS2015] 47863 HB* 18 59 29.3270631216 -36 35 44.155383108   15.509 15.444     ~ 1 0
35 [GLS2015] 48268 HB* 18 59 29.684 -36 36 44.08   15.548 15.410     ~ 1 0
36 Cl* NGC 6723 SAW V32 RR* 18 59 29.8656047304 -36 39 27.143483004   15.672 15.403     ~ 4 0
37 [GLS2015] 48528 HB* 18 59 29.9040085608 -36 39 57.878217108   16.122 15.508     ~ 1 0
38 [GLS2015] 49317 HB* 18 59 30.5305078008 -36 36 22.710665304   16.076 15.466     ~ 1 0
39 [GLS2015] 49440 HB* 18 59 30.66 -36 36 50.8   15.551 15.387     ~ 1 0
40 2MASS J18593228-3636091 HB* 18 59 32.2801318248 -36 36 09.127598580   16.044 15.445     ~ 1 0
41 2MASS J18593256-3635376 HB* 18 59 32.5681622832 -36 35 37.637200104   16.073 15.495     ~ 1 0
42 NGC 6723 GlC 18 59 33.15 -36 37 56.1           ~ 500 0
43 [GLS2015] 54070 HB* 18 59 33.9890961312 -36 39 13.422634992   15.628 15.440     ~ 1 0
44 [GLS2015] 54670 HB* 18 59 34.3480829760 -36 39 26.548875900   15.642 15.488     ~ 1 0
45 [GLS2015] 54960 HB* 18 59 34.53 -36 38 52.4   16.126 15.501     ~ 1 0
46 [GLS2015] 55259 HB* 18 59 34.6852943472 -36 39 45.122023152   15.664 15.471     ~ 1 0
47 [GLS2015] 56265 HB* 18 59 35.30 -36 39 05.7   16.162 15.503     ~ 1 0
48 2MASS J18593537-3640221 HB* 18 59 35.3800885824 -36 40 22.177011576   15.639 15.575     ~ 1 0
49 [GLS2015] 58421 HB* 18 59 36.6084453888 -36 40 36.681580920   16.158 15.506     ~ 1 0
50 2MASS J18593664-3633251 HB* 18 59 36.6406831656 -36 33 25.198962264   16.112 15.509     ~ 1 0
51 [GLS2015] 58978 HB* 18 59 36.98 -36 36 37.0   16.122 15.465     ~ 1 0
52 Cl* NGC 6723 SAW V12 RR* 18 59 37.08 -36 38 36.5   15.921 15.535     ~ 4 0
53 [GLS2015] 61280 HB* 18 59 38.50 -36 36 14.3   15.613 15.391     ~ 1 0
54 [GLS2015] 61405 HB* 18 59 38.60 -36 39 09.8   16.153 15.490     ~ 1 0
55 2MASS J18593897-3638543 HB* 18 59 38.9705449944 -36 38 54.339187632   16.113 15.496     ~ 1 0
56 2MASS J18594018-3634555 HB* 18 59 40.1835757608 -36 34 55.546863204   16.149 15.462     ~ 1 0
57 [GLS2015] 63763 HB* 18 59 40.279 -36 37 30.45   15.559 15.447     ~ 1 0
58 2MASS J18594152-3637190 HB* 18 59 41.5279502352 -36 37 19.142754960   16.138 15.493     ~ 1 0
59 2MASS J18594156-3638300 HB* 18 59 41.5605534432 -36 38 30.025826412   16.185 15.537     ~ 1 0
60 2MASS J18594201-3635577 HB* 18 59 42.0120268944 -36 35 57.730823052   16.111 15.522     ~ 1 0
61 2MASS J18594272-3636269 HB* 18 59 42.7183914720 -36 36 27.011105784   16.156 15.477     ~ 1 0
62 2MASS J18594347-3638250 HB* 18 59 43.4733668928 -36 38 25.043193528   16.165 15.544     ~ 1 0
63 [GLS2015] 68073 RR* 18 59 44.2249850688 -36 34 04.130410008           ~ 1 0
64 [GLS2015] 68779 HB* 18 59 45.036 -36 37 31.10   15.694 15.531     ~ 1 0
65 2MASS J18594829-3636560 HB* 18 59 48.3014634984 -36 36 56.024600436   16.179 15.535     ~ 1 0
66 2MASS J18594893-3637164 HB* 18 59 48.9420839976 -36 37 16.314817728   15.646 15.449     ~ 1 0
67 2MASS J18594955-3636393 HB* 18 59 49.5554110632 -36 36 39.352926708   16.155 15.560     ~ 1 0
68 2MASS J18595660-3637118 HB* 18 59 56.6050417008 -36 37 11.909675244   16.197 15.560     ~ 1 0
69 [GLS2015] 75716 HB* 18 59 56.639 -36 35 58.44   16.214 15.533     ~ 1 0
70 2MASS J19000079-3633070 HB* 19 00 00.7949851584 -36 33 07.049535696   15.684 15.538     ~ 1 0
71 NGC 6752 GlC 19 10 52.11 -59 59 04.4           ~ 2000 0
72 M 55 GlC 19 39 59.71 -30 57 53.1     6.49     ~ 853 0
73 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3139 0
74 NAME Local Group GrG ~ ~           ~ 8389 0
75 NAME Galactic Bulge reg ~ ~           ~ 4299 0

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