ON THE NATURE OF THE BLUE GIANTS IN NGC-330

Citation
Ek. Grebel et al., ON THE NATURE OF THE BLUE GIANTS IN NGC-330, Astronomy and astrophysics, 311(2), 1996, pp. 470-483
Citations number
90
Categorie Soggetti
Astronomy & Astrophysics
Journal title
ISSN journal
00046361
Volume
311
Issue
2
Year of publication
1996
Pages
470 - 483
Database
ISI
SICI code
0004-6361(1996)311:2<470:OTNOTB>2.0.ZU;2-P
Abstract
The young SMC cluster NGC 330 contains a number of blue stars that lie above the main-sequence turnoff found from our isochrone fitting and below the position of the blue supergiants. We used our own, new spect roscopy and published data on these stars to investigate their possibl e nature. Problems in interpreting the evolutionary status of the blue giants have been found in several preceding studies. In theoretical H -R diagrams, these stars lie in the rapidly traversed post main-sequen ce gap, similar to the unexpected concentration found by Fitzpatrick & Garmany (1990) in the H-R diagram of the LMC. We argue that these sta rs probably are core H burning main-sequence stars that appear as blue stragglers resulting from binary evolution as described in the simula tions of Pols & Marinus (1994) and effects of rapid rotation. Many of the blue stragglers are Be stars and likely rapid rotators. We suggest that there is evidence for the presence of blue stragglers also in NG C 1818, NGC 2004, and NGC 2100. We point out that blue stragglers may be a general phenomenon in the CMDs of young clusters in the Magellani c Clouds and discuss the implications for IMF and age determinations.