2019A&A...627A..34M


Query : 2019A&A...627A..34M

2019A&A...627A..34M - Astronomy and Astrophysics, volume 627A, 34-34 (2019/7-1)

Hot UV-bright stars of galactic globular clusters.

MOEHLER S., LANDSMAN W.B., LANZ T. and MILLER BERTOLAMI M.M.

Abstract (from CDS):

Context. We have performed a census of the UV-bright population in 78 globular clusters using wide-field UV telescopes. This population includes a variety of phases of post-horizontal branch (HB) evolution, including hot post-asymptotic giant branch (AGB) stars, and post-early AGB stars. There are indications that old stellar systems like globular clusters produce fewer post-(early) AGB stars than currently predicted by evolutionary models, but observations are still scarce. Aims. We wish to derive effective temperatures, surface gravities, and helium abundances of the luminous hot UV-bright stars in these clusters to determine their evolutionary status and compare the observed numbers to predictions from evolutionary theory. Methods. We obtained FORS2 spectroscopy of eleven of these UV-selected objects (covering a range of -2.3<[Fe/H]←1.0), which we (re-)analysed together with previously observed data. We used model atmospheres of different metallicities, including super-solar ones. Where possible, we verified our atmospheric parameters using UV spectrophotometry and searched for metal lines in the optical spectra. We calculated evolutionary sequences for four metallicity regimes and used them together with information about the HB morphology of the globular clusters to estimate the expected numbers of post-AGB stars. Results. We find that metal-rich model spectra are required to analyse stars hotter than 40 000 K. Seven of the eleven new luminous UV-bright stars are post-AGB or post-early AGB stars, while two are evolving away from the HB, one is a foreground white dwarf, and another is a white dwarf merger. Taking into account published information on other hot UV-bright stars in globular clusters, we find that the number of observed hot post-AGB stars generally agrees with the predicted values, although the numbers are still low. Conclusions. Spectroscopy is clearly required to identify the evolutionary status of hot UV-bright stars. For hotter stars, metal-rich model spectra are required to reproduce their optical and UV spectra, which may affect the flux contribution of hot post-AGB stars to the UV spectra of evolved populations. While the observed numbers of post-AGB and post-early AGB stars roughly agree with the predictions, our current comparison is affected by low number statistics.

Abstract Copyright: © ESO 2019

Journal keyword(s): stars: AGB and post-AGB - globular clusters: general

VizieR on-line data: <Available at CDS (J/A+A/627/A34): stars.dat efosc2-n.dat fors2-n.dat fors2-f.dat lte.dat nlte.dat wdmodel.dat feh-10.dat feh-15.dat feh-20.dat feh-23.dat>

Simbad objects: 61

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Number of rows : 61
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 Cl* NGC 104 R 1 * 00 23 58.1989264392 -72 05 30.394828464   13.593 10.73   10.43 B8III: 18 1
2 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3723 0
3 M 32 IG 00 42 41.825 +40 51 54.61 9.51 9.03 8.08     ~ 2088 2
4 LDN 1523 DNe 05 06 13.8 +31 42 20           ~ 47 1
5 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1330 0
6 Cl* NGC 1851 PML 46 * 05 14 08.6 -40 03 01   13.205 13.260     B3III 10 0
7 Cl* NGC 2808 FCFC 4594 * 09 12 01.7 -64 47 34   16.656 16.626     ~ 4 0
8 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1332 0
9 Cl* NGC 2808 FCFC 2946 * 09 12 22.36 -64 52 37.7   17.615 17.529     ~ 3 0
10 Cl* NGC 2808 FCFC 2947 * 09 12 22.87 -64 52 37.1   17.214 17.002     ~ 3 0
11 NGC 5139 5342 * 13 25 45.4307134464 -47 24 02.070700668   15.784 15.904     ~ 9 0
12 NGC 5139 542 * 13 25 49.9577510088 -47 22 59.766928428   12.96 12.92     ~ 12 0
13 Cl* NGC 5139 BPB 149840 * 13 26 11.56 -47 30 49.2           ~ 1 0
14 Cl* NGC 5139 BPB 256747 * 13 26 13.956 -47 25 30.19           ~ 1 0
15 Cl* NGC 5139 BPB 223519 * 13 26 45.05 -47 27 09.3   13.050 13.038     ~ 4 0
16 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3231 0
17 Cl* NGC 5139 UIT 2 * 13 26 52.9 -47 29 46           ~ 3 0
18 Cl* NGC 5139 BPB 318451 * 13 27 05.0670400080 -47 21 56.677354272   16.370 16.482     ~ 3 0
19 2MASS J13272898-4722472 pA* 13 27 28.9893774528 -47 22 47.300102004   13.30 13.16     ~ 25 0
20 NGC 5139 3596 * 13 27 46.1241336936 -47 30 58.436524836   14.140 14.163     ~ 9 0
21 HD 116980 PM* 13 28 04.5332702472 -47 42 18.548039484   9.27 8.77     F8V 14 0
22 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2374 0
23 NAME vZ 1128 pA* 13 42 16.7509672392 +28 26 00.616904988   14.77 15.04 15.50   O8p 71 0
24 M 5 GlC 15 18 33.22 +02 04 51.7   7.34 5.95     ~ 1872 0
25 Cl* NGC 5904 MSB 1 AB* 15 18 34.117 +02 05 00.17   14.2150 12.2791   14.6608 ~ 27 4
26 NGC 5986 GlC 15 46 03.00 -37 47 11.1     6.92     ~ 335 0
27 Cl* NGC 5986 ABO 6 * 15 46 03.38 -37 46 43.4   12.955 12.652     ~ 5 0
28 SDSS J155610.40+254640.3 HS* 15 56 10.4080827456 +25 46 40.256731200           sdOHe 7 0
29 Cl* NGC 6121 Y 453 * 16 23 22.3070791080 -26 28 03.458049924 15.03 15.914 15.857     ~ 6 0
30 Cl* NGC 6121 MKTB 2 * 16 23 26.3 -26 31 27 15.58 16.48 16.39     ~ 2 0
31 CD-38 10980 WD* 16 23 33.8380498896 -39 13 46.161043572 9.916 10.885 11.029 10.936 10.841 DA2 462 0
32 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1758 0
33 2MASS J16413368+3626077 pA* 16 41 33.6668708904 +36 26 07.783784952   12.98 13.14     B2p 75 0
34 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2099 0
35 M 10 GlC 16 57 09.05 -04 06 01.1     4.98     ~ 741 0
36 NGC 6397 162 HS* 17 40 38.4613882368 -53 38 31.347142908   13.06 13.23     sdOp 40 1
37 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1876 1
38 V* UV Tel LP* 18 15 10.2315437112 -53 24 34.555334112           ~ 1 0
39 Cl* NGC 6656 MPF 2-682 * 18 36 22.8482 -23 55 19.343           ~ 1 0
40 Cl* NGC 6656 ZNG 7 HS* 18 36 23.0656473360 -23 52 54.955710948   14.24 14.07     sdO6 7 0
41 M 22 GlC 18 36 23.94 -23 54 17.1   7.16 6.17     ~ 1295 0
42 Cl* NGC 6712 SS C49 HS* 18 53 03.47 -08 42 30.6   16.83 16.72     sdO 6 0
43 NGC 6712 GlC 18 53 04.32 -08 42 21.5   9.85 8.69     ~ 491 0
44 2MASS J18530579-0842378 pA* 18 53 05.7911950584 -08 42 37.857839940   13.66 13.33     ~ 13 0
45 NGC 6723 409 * 18 59 24.2527581288 -36 37 55.451680572   14.47 14.64     ~ 3 0
46 NGC 6723 360 * 18 59 29.1 -36 40 49   15.36 15.61     ~ 6 0
47 NGC 6723 GlC 18 59 33.15 -36 37 56.1           ~ 465 0
48 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1894 0
49 Cl* NGC 6752 BUON 2004 * 19 11 05.1 -59 57 47   16.11 16.42     ~ 4 0
50 Cl* NGC 6752 CL 2128 HS* 19 11 08.7263730384 -59 52 21.237144060   15.75 15.99     sdOB 9 0
51 Cl* NGC 6752 BUON 852 * 19 11 27.7571902176 -60 00 39.734229096   15.63 15.91     ~ 5 0
52 M 56 GlC 19 16 35.57 +30 11 00.5   8.90       ~ 389 0
53 Cl* NGC 6779 K 393 * 19 16 41.2787566080 +30 12 48.559003812   15.26       ~ 5 0
54 NGC 7078 559 * 21 29 58.23 +12 11 42.0   14.19 14.98     ~ 24 1
55 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 3021 0
56 PN Ps 1 PN 21 29 59.38 +12 10 27.5   13.39 14.06     sdO 280 0
57 NGC 7078 996 * 21 30 06.8 +12 11 10   14.17 14.373     ~ 19 0
58 M 30 GlC 21 40 22.12 -23 10 47.5     7.10     ~ 978 0
59 BD+28 4211 HS* 21 51 11.0221915656 +28 51 50.367627468 8.922 10.25 10.58 10.656 10.831 sdO2VIIIHe5 765 0
60 Feige 110 HS* 23 19 58.3996844256 -05 09 56.171142864 10.360 11.45 11.50 11.970 12.145 sdO8VIIIHe5 596 1
61 Cl* NGC 6752 BUON 4380 * ~ ~   15.79 15.93     ~ 3 0

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2022.05.28-23:26:52

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