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arXiv · 1305.0265

A Double White-Dwarf Cooling Sequence in ω Centauri

A. Bellini·J. Anderson·M. Salaris·S. Cassisi·L. R. Bedin·G. Piotto·P. Bergeron
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Abstract

We have applied our empirical-PSF-based photometric techniques on a large number of calibration-related WFC3/UVIS UV-B exposures of the core of ω Cen, and found a well-defined split in the right part of the white-dwarf cooling sequence (WDCS). The redder sequence is more populated by a factor of ~2. We can explain the separation of the two sequences and their number ratio in terms of the He-normal and He-rich subpopulations that had been previously identified along the cluster main sequence. The blue WDCS is populated by the evolved stars of the He-normal component (~0.55 Msun CO-core DA objects) while the red WDCS hosts the end-products of the He-rich population (~0.46 Msun objects, ~10% CO-core and ~90% He-core WDs). The He-core WDs correspond to He-rich stars that missed the central He-ignition, and we estimate their fraction by analyzing the population ratios along the cluster horizontal branch.

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A. Bellini, J. Anderson, M. Salaris, S. Cassisi, L. R. Bedin, G. Piotto, P. Bergeron. 2013-05-03. A Double White-Dwarf Cooling Sequence in ω Centauri. https://doi.org/10.1088/2041-8205%2F769%2F2%2Fl32

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