Detection of the helium flash gap in the integrated (U - B) versus (B - V) diagram for 624 Large Magellanic Cloud clusters

BICA, EDUARDO; CLARIA OLMEDO, JUAN JOSÉ; DOTTORI, HORACIO; SANTOS JR, JOÂO F.C.; PIATTI, ANDRÉS E.

ASTROPHYSICAL JOURNAL

Año: 1991 vol. 381 p. 51 - 53

0004-637X

The number of Large Magellanic Cloud clusters with integrated UBV photometry has been increased by more than a factor of 4, now totaling 624 objects. A gap in the cluster distribution through the color-color diagram appears in the region of the equivalent SWB type IV. The amplitude of the gap is about 0.1 mag in both colors. The turnoff ages of a few clusters near the gap edges perfectly fit theoretical predictions of a red giant branch phase transition. This jump is due to the first appearance of stars suffering the helium flash, which form a bright and populous red giant branch that persists that the subsequent cluster evolution. As an additional result, evidence is found that Hodge 7 (SL 735) might be a classical globular cluster.