Tools
Tools
Tailo, M, D'Antona, F, Milone, AP, Bellini, A, Ventura, P, Di Criscienzo, M, Cassisi, S, Piotto, G, Salaris, M, Brown, TM, Vesperini, E, Bedin, LR, Marino, AF, Nardiello, D and Anderson, J (2017) The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters - XI. The horizontal branch in NGC 6388 and NGC 6441. Monthly Notices of the Royal Astronomical Society, 465 (1). pp. 1046-1056. ISSN 0035-8711
|
Text
stw2790.pdf - Published Version Download (924kB) | Preview |
Abstract
The Hubble Space Telescope UV Legacy survey of Galactic globular clusters (GC) is characterizing many different aspects of their multiple stellar populations. The 'Grundahl-jump' (G-jump) is a discontinuity in ultraviolet brightness of blue horizontal branch (HB) stars, signalling the onset of radiative metal levitation. The HB Legacy data confirmed that the G-jump is located at the same Teff (≃11 500 K) in nearly all clusters. The only exceptions are the metal-rich clusters NGC 6388 and NGC 6441, where the G-jump occurs at Teff ≃ 13-14 000 K. We compute synthetic HB models based on new evolutionary tracks including the effect of helium diffusion, and approximately accounting for the effect of metal levitation in a stable atmosphere. Our models show that the G-jump location depends on the interplay between the time-scale of diffusion and the time-scale of the evolution in the Teff range 11 500 K≲Teff≲14 000 K. The G-jump becomes hotter than 11 500 K only for stars that have, in this Teff range, a helium mass fraction Y ≳ 0.35. Similarly high Y values are also consistent with the modelling of the HB in NGC 6388 and NGC 6441. In these clusters, we predict that a significant fraction of HB stars show helium in their spectra above 11 500 K, and full helium settling should only be found beyond the hotter G-jump. © 2016 The Authors.
| Item Type: | Article |
|---|---|
| Additional Information: | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
| Uncontrolled Keywords: | 0201 Astronomical And Space Sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | Oxford University Press |
| Date Deposited: | 11 May 2017 09:45 |
| Last Modified: | 20 Apr 2022 08:34 |
| DOI or ID number: | 10.1093/mnras/stw2790 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/6403 |
 |
View Item |