SIMBAD references

2018MNRAS.481.5098M - Mon. Not. R. Astron. Soc., 481, 5098-5122 (2018/December-3)

The Hubble Space Telescope UV legacy survey of galactic globular clusters - XVI. The helium abundance of multiple populations.

MILONE A.P., MARINO A.F., RENZINI A., D'ANTONA F., ANDERSON J., BARBUY B., BEDIN L.R., BELLINI A., BROWN T.M., CASSISI S., CORDONI G., LAGIOIA E.P., NARDIELLO D., ORTOLANI S., PIOTTO G., SARAJEDINI A., TAILO M., VAN DER MAREL R.P. and VESPERINI E.

Abstract (from CDS):

Recent work, based on data from the Hubble Space Telescope (HST ) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all the analysed clusters host two groups of first- (1G) and second-generation (2G) stars. In most GCs, both 1G and 2G stars host substellar populations with different chemical composition. We compare multiwavelength HST photometry with synthetic spectra to determine for the first time the average helium difference between the 2G and 1G stars in a large sample of 57 GCs and the maximum helium variation within each of them. We find that in all clusters 2G stars are consistent with being enhanced in helium with respect to 1G. The maximum helium variation ranges from less than 0.01 to more than 0.10 in helium mass fraction and correlates with both the cluster mass and the colour extension of the horizontal branch (HB). These findings demonstrate that the internal helium variation is one of the main (second) parameters governing the HB morphology.

Abstract Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): stars: abundances - stars: population II - globular clusters: general

Simbad objects: 59

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2020.12.01-20:54:19

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