2009A&A...499..865H


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.14CEST11:22:03

2009A&A...499..865H - Astronomy and Astrophysics, volume 499, 865-878 (2009/6-1)

A high-resolution study of isotopic composition and chemical abundances of blue horizontal branch stars in the globular clusters NGC6397 and NGC6752.

HUBRIG S., CASTELLI F., DE SILVA G., GONZALEZ J.F., MOMANY Y., NETOPIL M. and MOEHLER S.

Abstract (from CDS):

Large abundance anomalies have been previously detected in Horizontal Branch B-type stars. It has been suggested that at Teff>11000K the stellar atmospheres become susceptible to diffusion effects and thus develop surface abundances similar to those that appear in the main-sequence, chemically peculiar group of A and B-type stars. We present the first high-resolution study of isotopic anomalies and chemical abundances in six Horizontal Branch B-type stars in globular clusters NGC6397 and NGC6752 and compare them to those observed in HgMn stars. We obtained high-resolution (up to R∼115000) UVES spectra of a representative sample of six B-type stars (T183, T191, T193, B652, B2151, B2206) with sharp spectral lines (vsini≤10km/s). The stars T183 and B2151 were observed on two consecutive nights to examine potential spectrum variability. A detailed spectrum analysis was done relying on Kurucz ATLAS9 and ATLAS12 models. The spectra were analysed using the SYNTHE code to generate synthetic spectra. It is the first time an abundance analysis is performed for all elements for which spectral lines were detected in UVES spectra of Horizontal Branch B-type stars. Our study of these stars revealed no signs of He isotopic anomalies, which would produce a 3He/4He ratio different from the solar one. The isotopic anomaly of Ca is detected in all six studied stars. The chemical abundance analysis reveals an overabundance over the solar values of P, Ti, Mn, Fe, and Y and an overabundance over the cluster metallicity of Mg, Ca, and Cr. This behaviour is very similar in all six stars of both clusters with a few exceptions: the Na abundance is larger by more than 1.4dex than the cluster metallicity in B652, and by more than 0.8dex greater than the cluster metallicity in B2206; the Co abundance is 1.0dex over the solar abundance for T191, while Zr is overabundant over the solar abundance by 0.4dex in B2206. No lines of Hg or other heavy elements were observed in the spectra. Weak emission lines of TiII, similar to those frequently observed in HgMn stars have been discovered in one Horizontal Branch B-type star T191. Furthermore, we detected a radial velocity change of 0.9km/s from one night to the next for T183 and 0.4km/s for B2151. Further high-resolution observations are needed to examine whether both stars are spectroscopic binaries.

Abstract Copyright:

Journal keyword(s): Galaxy: globular clusters: individual: NGC6397, NGC6752 - stars: Population II - stars: atmospheres - stars: fundamental parameters - stars: abundances - stars: binaries: spectroscopic

CDS comments: Paragraph.2 B665 is a probable misprint for B652 (Cl* NGC 6752 BUON 652 in Simbad).

Simbad objects: 15

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Number of rows : 15

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 PHL 1434 HS* 02 41 03.9662855915 -19 00 11.591807765   12.49 12.39     sdB 14 0
2 BD+30 2431 HB* 13 38 24.7655647470 +29 21 56.006946595   9.89 10.02     B5Vp 105 0
3 * 3 Cen ** 13 51 49.60136 -32 59 38.7067           B5III+B9IV 239 0
4 HD 135485 SB* 15 15 45.2572740112 -14 41 34.522358868 7.57 8.05 8.13     B3V 107 0
5 NGC 6397 470 * 17 40 20.0605657085 -53 41 42.998234450 13.944 13.87 13.74 14.06   B8 7 0
6 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1749 1
7 [AT2000b] 191 * 17 40 56.022 -53 35 07.39 14.037 13.969 13.923     ~ 1 0
8 [AT2000b] 193 * 17 40 57.460 -53 35 32.79 14.014 13.954 13.922     ~ 1 0
9 HD 175640 * 18 56 22.6598248501 -01 47 59.505133114 5.86 6.149 6.196     B9IIIpHgMnEu 132 0
10 Cl* NGC 6752 CL 1083 * 19 10 21.2860806535 -59 51 56.006311141   15.22 15.33     B5 9 0
11 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1762 0
12 Cl* NGC 6752 BUON 2206 * 19 11 00.931 -59 57 42.22 14.202 14.459 14.532     ~ 2 0
13 Cl* NGC 6752 BUON 2151 * 19 11 01.965 -59 57 42.22 14.202 14.468 14.554     ~ 1 0
14 Cl* NGC 6752 BUON 652 * 19 11 32.6 -59 57 41 14.202 14.701 14.743     ~ 3 0
15 PHL 25 HS* 21 32 04.6240474493 -17 18 39.584989278   11.547 10.979     sdB 18 0

    Equat.    Gal    SGal    Ecl

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2019.10.14-11:22:03

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