2011A&A...529A..60M


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.03CEST23:19:33

2011A&A...529A..60M - Astronomy and Astrophysics, volume 529A, 60-60 (2011/5-1)

Horizontal branch evolution, metallicity, and sdB stars.

MICHAUD G., RICHER J. and RICHARD O.

Abstract (from CDS):

Abundance anomalies have been observed in field sdB stars and in nearly all horizontal branch (HB) stars of globular clusters with Teff>11000K, whatever be the cluster metallicity. We aim to determine the abundance variations that are expected in sdB stars and in HB stars of metallicities Z ≥10–4 and investigate what the observed abundances teach us about hydrodynamical processes competing with atomic diffusion. Complete stellar evolution models, including the effects of atomic diffusion and radiative acceleration, have been computed from the zero age main-sequence for metallicities of Z0= 0.0001, 0.001, 0.004 and 0.02. On the HB the masses were selected to cover the Teff interval from 7000 to 37000K. Some 60 evolutionary HB models were calculated. The calculations of surface abundance anomalies during the horizontal branch depend on one parameter, the surface mixed mass. For sdB stars with Teff<37000K and for HB stars with Teff>11000K in all observed clusters, independent of metallicity, we found that most observed abundance anomalies (even up to ∼x200) were compatible, within error bars, with expected abundances. A mixed mass of ∼10–7M was determined by comparison with observations. Observations of globular cluster HB stars with Teff>11000K and of sdB stars with Teff<37000K suggest that most observed abundance anomalies can be explained by element separation driven by radiative acceleration occuring at a mass fraction of ∼10–7M. Mass loss or turbulence appear to limit the separation between 10–7M and the surface.

Abstract Copyright:

Journal keyword(s): stars: evolution - stars: horizontal-branch - stars: abundances - stars: Population II - subdwarfs

Simbad objects: 16

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Number of rows : 16

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 288 GlC 00 52 45.24 -26 34 57.4   10 8.13     ~ 918 0
2 Feige 11 HS* 01 04 21.6744758331 +04 13 37.051396308 10.847 11.826 12.065 12.183 12.324 sdB2VIHe4 110 0
3 M 79 GlC 05 24 10.59 -24 31 27.3   9.21 8.16     ~ 716 0
4 IRAS 09110-6439 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1244 0
5 NGC 2898 LIN 09 29 46.3424000489 +02 03 51.681254739   14.8       ~ 21 0
6 Feige 48 HS* 11 47 14.4977747924 +61 15 31.790488292   13.12 13.28     sdB 111 0
7 M 68 GlC 12 39 27.98 -26 44 38.6   10.26 7.96     ~ 876 0
8 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2265 0
9 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1676 0
10 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2006 0
11 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 1904 0
12 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1806 0
13 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 2907 0
14 NGC 7078 119 * ~ ~   16.78 16.80     ~ 7 0
15 NGC 7078 276 * ~ ~   16.67 16.68     ~ 7 0
16 Cl* NGC 6205 WF 4-3085 * ~ ~     16.23     ~ 5 0

    Equat.    Gal    SGal    Ecl

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2020.07.03-23:19:33

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