1997A&A...319..109M


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.03CET10:14:17

1997A&A...319..109M - Astronomy and Astrophysics, volume 319, 109-121 (1997/3-1)

Hot HB stars in globular clusters: physical parameters and consequences for theory. III. NGC 6752 and its long blue vertical branch.

MOEHLER S., HEBER U. and RUPPRECHT G.

Abstract (from CDS):

We present spectroscopic analyses of 17 faint blue stars in the globular cluster NGC 6752, using optical and UV spectrophotometric data and intermediate resolution optical spectra. Effective temperatures, surface gravities, and helium abundances of the stars are determined and compared to theoretical predictions. All stars are helium deficient by factors ranging from 3 to more than 100, indicative of gravitational settling of helium. Stars with effective temperatures above about 20000K (sdBs) fit well to the evolutionary tracks, whereas the cooler stars show lower surface gravities than theoretically expected. This agrees with earlier findings by Moehler et al. (1995A&A...294...65M) for the faint blue stars in M 15. Deriving masses from the atmospheric parameters and the cluster distance leads to a mean mass of the sdB stars of 0.50 M and a standard deviation of about 0.043 dex, which is below the value derived of the observational errors and therefore consistent with a very narrow mass distribution. The mean mass is in good agreement with the (0.49 ± 0.02) M expected if sdB stars are extreme horizontal branch stars with a helium core of 0.48 M and an extremely thin hydrogen layer. The cooler stars however show a significantly lower mean mass of 0.30 M with a standard deviation of the mean of 0.059 dex in agreement with the findings of Moehler et al. (1995A&A...294...65M) and de Boer et al. (1995A&A...303...95D) for the BHB stars in M 15 and NGC 6397, respectively. The problems presented by the different mass distributions of BHB and sdB stars within one cluster are discussed.

Abstract Copyright:

Journal keyword(s): stars: early-type - stars: horizontal branch - stars: subdwarfs - stars: Population II - globular clusters: individual: NGC 6752

CDS comments: star 3-118 = Cl* NGC 6752 CL 3118

Simbad objects: 38

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Number of rows : 38

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 288 GlC 00 52 45.24 -26 34 57.4   10 8.13     ~ 943 0
2 HD 269696 HS* 05 31 40.3598545037 -69 53 02.158611829 9.74 10.92 11.15     sdB+dM 176 0
3 HD 128220 SB* 14 35 15.7846989338 +19 12 54.511945549   8.724 8.503     G0IIIn+sdO 110 0
4 M 5 GlC 15 18 33.22 +02 04 51.7   7.34 5.95     ~ 1805 0
5 LP 916-15 PM* 15 38 59.6477173130 -28 35 36.970418054   12.19 11.62     A 107 0
6 CD-38 10980 WD* 16 23 33.8384178546 -39 13 46.160032569 9.916 10.885 11.029 10.936 10.841 DA2 446 0
7 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 1933 0
8 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1821 1
9 M 22 GlC 18 36 23.94 -23 54 17.1   7.16 6.17     ~ 1242 0
10 Cl* NGC 6752 CL 2167 * 19 10 06.8977670248 -59 57 32.236036979   15.59 15.65     ~ 6 0
11 Cl* NGC 6752 BUON 4548 * 19 10 10.9 -59 51 31   16.46 16.60     ~ 5 0
12 Cl* NGC 6752 BUON 4009 * 19 10 22.2 -60 07 47   17.14 17.44     ~ 3 0
13 Cl* NGC 6752 BUON 3975 * 19 10 22.7 -60 03 01   16.05 16.27     ~ 2 0
14 Cl* NGC 6752 BUON 3915 * 19 10 24.2 -59 54 22   16.93 17.16     ~ 2 0
15 Cl* NGC 6752 BUON 3655 * 19 10 30.2 -59 57 27   16.257 16.425     ~ 2 0
16 Cl* NGC 6752 CL 3118 HS* 19 10 38.3604340835 -60 08 50.384107723   17.50 17.76     sdB 7 0
17 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1835 0
18 Cl* NGC 6752 BUON 2395 * 19 10 57.3 -60 03 32   16.49 16.73     ~ 2 0
19 Cl* NGC 6752 BUON 2162 * 19 11 02.0777693354 -60 03 05.775218746   17.61 17.88     ~ 3 0
20 Cl* NGC 6752 CL 2128 HS* 19 11 08.7268496688 -59 52 21.237895548   15.75 15.99     sdOB 9 0
21 Cl* NGC 6752 BUON 1628 * 19 11 11.7 -59 59 36   16.13 16.30     ~ 2 0
22 Cl* NGC 6752 BUON 1509 * 19 11 15.0 -59 54 31   15.46 15.52     ~ 2 0
23 Cl* NGC 6752 CL 1112 * 19 11 27.3 -60 03 51   17.35 17.61     ~ 3 0
24 Cl* NGC 6752 BUON 852 * 19 11 27.7575012939 -60 00 39.734136826   15.63 15.91     ~ 5 0
25 Cl* NGC 6752 CL 3781 HS* 19 11 29.7954016161 -60 02 54.934095695   16.89 17.13     sdB 7 0
26 Cl* NGC 6752 CL 602 * 19 11 37.7 -60 03 11   17.14 17.45     ~ 3 0
27 Cl* NGC 6752 CL 3675 HS* 19 11 42.0190626839 -59 56 34.549172292   16.90 17.12     sdB 6 0
28 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 2943 0
29 EGGR 264 WD* 23 19 35.3881040214 -17 05 28.468265988 13.279 14.132 14.111 14.07 14.049 DB3 111 0
30 Feige 110 HS* 23 19 58.3995050606 -05 09 56.170282845 10.360 11.45 11.50 11.970 12.145 sdO8VIIIHe5 567 1
31 Cl* NGC 6752 BUON 617 * ~ ~   17.51 17.84     ~ 1 0
32 Cl* NGC 6752 BUON 1288 * ~ ~   17.59 17.90     ~ 1 0
33 Cl* NGC 6752 BUON 2126 * ~ ~   17.08 17.28     ~ 1 0
34 Cl* NGC 6752 BUON 2454 * ~ ~   14.21 14.27     ~ 1 0
35 Cl* NGC 6752 BUON 577 * ~ ~   14.81 14.85     ~ 1 0
36 Cl* NGC 6752 BUON 4104 * ~ ~   15.20 15.20     ~ 3 0
37 Cl* NGC 6752 BUON 4380 * ~ ~   15.79 15.93     ~ 3 0
38 Cl* NGC 6752 BUON 210 * ~ ~   16.73 17.04     ~ 1 0

    Equat.    Gal    SGal    Ecl

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2021.03.03-10:14:17

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