2006A&A...457..569C


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.14CEST02:57:33

2006A&A...457..569C - Astronomy and Astrophysics, volume 457, 569-573 (2006/10-2)

Hot flashers and He dwarfs in galactic globulars.

CASTELLANI M., CASTELLANI V. and PRADA MORONI P.G.

Abstract (from CDS):

We revisit the evolutionary scenario for hot flasher low-mass structures, where mass loss delays the He flash till the initial phases of their white dwarf cooling sequence. Our aim has been to test the theoretical results vis-a-vis different assumptions about the efficiency of mass loss. To this purpose, we present evolutionary models covering a fine grid of masses, as obtained assuming a single episode of mass loss in a red giant model of 0.86M with Z=0.0015. We find reasonable agreement with previous evolutionary investigations, showing that for the given metallicity late hot flashers are predicted to cover the mass range M=0.4975 to M=0.4845(±0.0005)M, all models igniting the He-flash with a mass of the H-rich envelope as given by Me=0.00050±0.00002M. The ignition mechanism is discussed in some detail, showing the occurrence of a bifurcation in the evolutionary history of stellar structures at the lower-mass limit for He ignition. Below such a critical mass, the structures miss the He ignition, cooling down as a hot flasher-manque He white dwarf. We predict that these structures will cool down, reaching the luminosity logL/L=-1 in a time five times longer at the very least than the corresponding cooling time of a normal CO white dwarf. On very general grounds, one expects that old stellar clusters with a sizeable population of hot flashers should produce at least a similar amount of slow-cooling He white dwarfs. According to this result, in a cluster where 20% of red giants escape the He burning phase, one expects roughly twice as white dwarfs than in a normal cluster where all red giants undergo their He flash.

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Journal keyword(s): stars: evolution - stars: white dwarfs - stars: mass-loss

Simbad objects: 2

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Number of rows : 2

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 2808 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1285 0
2 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3088 0

    Equat.    Gal    SGal    Ecl

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2021.04.14-02:57:33

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