Query : 2010A&A...523A..10I

2010A&A...523A..10I - Astronomy and Astrophysics, volume 523, A10-10 (2010/11-2)

White-dwarf kicks and implications for barium stars.


Abstract (from CDS):

The formation mechanism of the barium stars is thought to be well understood. Barium-rich material, lost in a stellar wind from a thermally-pulsing asymptotic-giant branch star in a binary system, is accreted by its companion main-sequence star. Now, many millions of years later, the primary is an unseen white dwarf and the secondary has itself evolved into a giant which displays absorption lines of barium in its spectrum and is what we call a barium star. A similar wind-accretion mechanism is also thought to form the low-metallicity CH and carbon-enhanced metal-poor stars. Qualitatively the picture seems clear but quantitatively it is decidedly murky: several key outstanding problems remain which challenge our basic understanding of binary-star physics. Barium stars with orbital periods less than about 4000days should - according to theory - be in circular orbits because of tidal dissipation, yet they are often observed to be eccentric. Only one barium-star period longer than 104days has been published although such stars are predicted to exist in large numbers. In this paper we attempt to shed light on these problems. First, we consider the impact of kicking the white dwarf at its birth, a notion which is supported by independent evidence from studies of globular clusters. Second, we increase the amount of orbital angular momentum loss during wind mass transfer, which shrinks barium-star binaries to the required period range. We conclude with a discussion of possible physical mechanisms and implications of a kick, such as the break up of wide barium-star binaries and the limits imposed on our models by observations.

Abstract Copyright:

Journal keyword(s): stars: chemically peculiar - binaries: close - stars: AGB and post-AGB - Galaxy: stellar content - nuclear reactions, nucleosynthesis, abundances

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 BD+38 118 SB* 00 49 55.8770967288 +39 15 23.534840556   10.40 8.86     G5 23 0
2 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1513 0
3 * 56 UMa SB* 11 22 49.5779879928 +43 28 57.714470868 6.86 6.04 5.03 4.30 3.81 G8IIIa 147 0

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