DOI: 10.1007/s10509-015-2368-6

DOI: 10.1093/mnras/stu2700
27 citations
Résumé:

There is no conclusive explanation of why ˜80 per cent of planetary nebulae (PNe) are non-spherical. In the Binary Hypothesis, a binary interaction is a preferred channel to form a non-spherical PN. A fundamental step to corroborate or disprove the Binary Hypothesis is to estimate the binary fraction of central stars of PNe (CSPNe) and compare it with a prediction based on the binary fraction of the progenitor, main-sequence population. In this paper, the second in a series, we search for spatially unresolved I- and J-band flux excess in an extended sample of 34 CSPN by a refined measurement technique with a better quantification of the uncertainties. The detection rate of I- (J-)band flux excess is 32 ± 16 per cent (50 ± 24 per cent). This result is very close to what was obtained in Paper I with a smaller sample. We account conservatively for unobserved cool companions down to brown dwarf luminosities, increasing these fractions to 40 ± 20 per cent (62 ± 30 per cent). This step is very sensitive to the adopted brightness limit of our survey. Accounting for visual companions increases the binary fraction to 46 ± 23 per cent (71 ± 34 per cent). These figures are lower than in Paper I. The error bars are better quantified, but still unacceptably large. Taken at face value, the current CSPN binary fraction is in line with the main-sequence progenitor population binary fraction. However, including white dwarfs companions could increase this fraction by as much as 13 (21) per cent points.

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DOI: 10.1051/eas/1567077
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Résumé:

There is no quantitative theory to explain why a high 80% of all planetary nebulae are non-spherical. The Binary Hypothesis states that a companion to the progenitor of a central star of planetary nebula is required to shape nebulae whose shapes are not spherical or mildly elliptical, implying that many single post-AGB stars do not make a PN at all. A way to test this hypothesis is to estimate the binary fraction of central stars of planetary nebula and to compare it with that of the main sequence population. Preliminary results from the infrared excess technique indicate that the binary fraction of central stars of planetary nebula is higher than that of the main sequence, implying that PNe could preferentially form via a binary channel. I will present new results from a search of red and infrared flux excess in an extended sample of central stars of planetary nebula and compare the improved estimate of the PN binary fraction with that of main sequence stars.

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