1999A&A...346..459M

Query : 1999A&A...346..459M

1999A&A...346..459M - Astronomy and Astrophysics, volume 346459-464 (1999/6-2)

Differences in the fractions of Be stars in galaxies.

MAEDER A., GREBEL E.K. and MERMILLIOD J.-C.

Abstract (from CDS):

The number ratios Be/(B+Be) of Be to B-type stars in young, well studied clusters of the Galaxy, the LMC and SMC are examined. In order to disentangle age and metallicity effects we choose clusters in the same age interval and for which reliable photometric and spectroscopic data are available. Number counts are made for various magnitude intervals, and the results are found to be stable with respect to this choice. In the magnitude interval MV=-5 to -1.4 (i.e. O9 to B3) we obtained a ratio Be/(B+Be) = 0.11, 0.19, 0.23, 0.39 for 21 clusters located in the interior of the Galaxy, the exterior of the Galaxy, the LMC and the SMC, respectively. Various hypotheses for these differences are examined. An interesting possibility is that the average rotation is faster at low metallicities as a result of star formation processes. The much higher relative N-enrichment found by Venn et al. (1998, PASP Conf. Ser. 131, 177) in A-type supergiants of the SMC, compared to galactic supergiants, also strongly supports the presence of more rotational mixing at low metallicities. We discuss whether high rotational mixing may be the source of primary nitrogen in the early chemical evolution of galaxies.

Abstract Copyright: ∼

Journal keyword(s): stars: emission-line, Be - stars: evolution - stars: rotation

CDS comments: Cluster Hodge 301 = H88 301.

Simbad objects: 24

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Number of rows : 24
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
2 NGC 330 Cl* 00 56 18.55 -72 27 45.1 9.37 9.76 9.55   8.89 ~ 445 0
3 NGC 346 Cl* 00 59 04.4000 -72 10 39.000           ~ 547 0
4 NGC 457 OpC 01 19 32.4 +58 16 40   6.97 6.4     ~ 259 2
5 M 103 OpC 01 33 21.1 +60 39 13   7.72 7.4     ~ 212 0
6 NGC 663 OpC 01 46 22.2 +61 12 53   7.78 7.1     ~ 269 0
7 NGC 869 OpC 02 18 57.0 +57 08 02           ~ 504 0
8 NGC 884 OpC 02 22 15.7 +57 08 59           ~ 503 0
9 NGC 957 OpC 02 33 25.4 +57 33 13   8.34 7.6     ~ 110 0
10 NGC 1818B Cl* 05 04 01.82 -66 26 46.1           ~ 3 0
11 NGC 1818 GlC 05 04 13.300 -66 26 05.47           ~ 279 0
12 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
13 NGC 1948 As* 05 24 20.00 -66 24 12.0   10.81 10.61     ~ 110 0
14 NGC 2004 Cl* 05 30 41.340 -67 17 21.83   9.6       ~ 281 0
15 NGC 2006 Cl* 05 31 19 -66 58.4   11.00 10.88     ~ 35 0
16 [SL63] 538 Cl* 05 31 19.600 -66 57 50.69   9.9 11.30     ~ 35 0
17 KMHK 1019 Cl* 05 31 50 -66 59.8           ~ 9 0
18 H88 301 Cl* 05 38 16 -69 04.0   11.18 10.89     ~ 80 0
19 NGC 2100 Cl* 05 42 07.200 -69 12 26.99           ~ 195 0
20 NGC 2439 OpC 07 40 46.5 -31 41 36   7.31 6.9     ~ 150 0
21 NGC 3293 OpC 10 35 50.3 -58 14 04           ~ 327 0
22 NGC 3766 OpC 11 36 13.5 -61 36 42   5.66 5.3     ~ 222 0
23 NGC 4755 OpC 12 53 39.2 -60 22 07           ~ 300 0
24 NGC 7160 OpC 21 53 44.8 +62 35 33   6.34 6.1     ~ 243 0

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