TY - JOUR
T1 - The binary fraction of planetary nebula central stars - II. A larger sample and improved technique for the infrared excess search
AU - Douchin, Dimitri
AU - De Marco, Orsola
AU - Frew, D. J.
AU - Jacoby, G. H.
AU - Jasniewicz, G.
AU - Fitzgerald, M.
AU - Passy, Jean Claude
AU - Harmer, D.
AU - Hillwig, Todd
AU - Moe, Maxwell
PY - 2015/4/21
Y1 - 2015/4/21
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84942133635&partnerID=8YFLogxK
U2 - 10.1093/mnras/stu2700
DO - 10.1093/mnras/stu2700
M3 - Article
AN - SCOPUS:84942133635
VL - 448
SP - 3132
EP - 3155
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
SN - 1745-3925
IS - 4
ER -