MULTICOLOR NTT CCD PHOTOMETRY OF THE POST-CORE-COLLAPSE GLOBULAR-CLUSTER M30

Citation
G. Alcaino et al., MULTICOLOR NTT CCD PHOTOMETRY OF THE POST-CORE-COLLAPSE GLOBULAR-CLUSTER M30, The Astronomical journal, 115(4), 1998, pp. 1492-1499
Citations number
44
Categorie Soggetti
Astronomy & Astrophysics
Journal title
ISSN journal
00046256
Volume
115
Issue
4
Year of publication
1998
Pages
1492 - 1499
Database
ISI
SICI code
0004-6256(1998)115:4<1492:MNCPOT>2.0.ZU;2-Z
Abstract
We have carried out multicolor (UBVI) CCD photometry for more than 140 0 stars (13.5 < V < 21.5) in a 6' x 6' field of the globular cluster M 30. We find the main-sequence turnoff at V-TO, = 18.65 +/- 0.05, (B-V) (TO) = 0.46 +/- 0.03, (V-l)(TO) = 0.62 +/- 0.04, and (B-I)(TO) = 1.08 +/- 0.05 (errors include uncertainties of the photometric zero points) . From a comparison of the two-color (U-B)-(B-V) diagram for the clust er with the similar diagram for NGC 6397, a reddening value E(B-V) = 0 .078 +/- 0.043 is derived for M30. We have analyzed the positions of m ain-sequence stars, subgiants, and giants in the (U-B)-(B-V) diagram a nd revealed some deviations from theoretical predictions and some diff erences compared with NGC 6397. Our comparison of the color-magnitude diagram with isochrones shows that the cluster is approximately as old as NGC 6397. The isochrone fit is not quite consistent when using dif ferent color indexes. We have also found some deviations from the obse rved shape of the main sequence for existing theoretical isochrones. T he upper limit for binary population in the studied cluster field (inc luding visual double stars) is estimated as similar to 5% at r similar to 6' from the cluster's center.