SIMBAD references

2004A&A...420..605M - Astronomy and Astrophysics, volume 420, 605-617 (2004/6-3)

The ubiquitous nature of the horizontal branch second U-jump. A link with the Blue Hook scenario?

MOMANY Y., BEDIN L.R., CASSISI S., PIOTTO G., ORTOLANI S., RECIO-BLANCO A., DE ANGELI F. and CASTELLI F.

Abstract (from CDS):

In a previous paper we reported on a discontinuity in the extreme horizontal branch (EHB) of the Galactic globular cluster NGC 6752, which we called the second U-jump. This feature was attributed to a combination of post zero-age horizontal branch evolution and diffusion effects. In this follow-up study we analyze other EHB clusters and show that the second U-jump is a common feature among EHB clusters reaching Teff≥23000K, and that its onset in different clusters converges around Teff∼21000±3000K. We also present near-ultraviolet diagrams of ωCen and NGC 2808, the only two objects with spectroscopically confirmed ``blue hook'' stars (Teff≥35000K). We confirm predictions of a photometric discontinuity separating late from early-helium flashers. Moreover, we present empirical evidence that the second U-jump population might be mainly composed of early-helium flashers. Lastly, we revisit the discussion on the ubiquitous nature of the gaps and jumps so far identified in the blue HB tails, suggesting a possible discrete nature of the distribution in temperature of the HB stars.

Abstract Copyright:

Journal keyword(s): stars: horizontal-branch - stars: Hertzsprung-Russell (HR) and C-M diagrams - stars: Population II - Galaxy: globular clusters: general - ultraviolet: stars

Simbad objects: 24

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