The binary fraction of planetary nebula central stars - III. the promise of VPHAS+

Abstract

The majority of planetary nebulae (PNe) are not spherical, and current single-star models cannot adequately explain all the morphologies we observe. This has led to the Binary Hypothesis, which states that PNe are preferentially formed by binary systems. This hypothesis can be corroborated or disproved by comparing the estimated binary fraction of all PNe central stars (CS) to that of the supposed progenitor population. One way to quantify the rate of CS binarity is to detect near infra-red (IR) excess indicative of a low-mass main sequence companion. In this paper, a sample of known PNe within data release 2 of the ongoing VPHAS+ are investigated. We give details of the method used to calibrate VPHAS+ photometry, and present the expected colours of CS and main sequence stars within the survey. Objects were scrutinized to remove PN mimics from our sample and identify true CS. Within our final sample of 7 CS, 6 had previously either not been identified or confirmed. We detected an i band excess indicative of a low-mass companion star in 3 CS, including one known binary, leading us to to conclude that VPHAS+ provides the precise photometry required for the IR excess method presented here, and will likely improve as the survey completes and the calibration process finalised. Given the promising results from this trial sample, the entire VPHAS+ catalogue should be used to study PNe and extend the IR excesstested CS sample.

Planetary Nebulae Embryo after a Common Envelope Event

“…The ring contains most of the mass, although the entire ejecta propagates well beyond the shown domain. This shape visually resembles the images of such post-CE nebulae as NGC 6337 and Sp 1, which were found to be post-CE PNe [29,30], or Hf 38, also argued to have two central stars (see the image in [5]). This visual symmetry of the ejecta is mainly due to the symmetry of recombination outflows.…”

“…About 50 post-CE PN with central stars are known [1,3,4]; CE events could be responsible for most non-spherical PNe [5]. Even though many post-CE PN are bipolar [4], the morphology of the post-CE PN is not uniform.…”

A high-mass planetary nebula in a Galactic open cluster

“…Taken with the CS location at the PN's geometric centre, this gives high confidence that the true CS has been identified. Fitting our measured VPHAS+ u-g stellar colour to published reddening lines 34 (assuming a high temperature blackbody spectrum) we estimate a CS reddening of E(B-V)=0.28 ± 0.04 36 . This independent VPHAS+ photometric reddening estimate for this CS candidate is much more consistent, within the uncertainties, with that for the cluster and when compared to the large uncertainties for the PN reddening estimate.…”

The formation of ‘columns crowns’ by jets interacting with a circumstellar dense shell

“…The third direction of progress has been the finding that binary systems shape most, and probably all, PNe (e.g., Akras et al 2016;Ali et al 2016;Bond et al 2016;Chen et al 2016;Chiotellis et al 2016;García-Rojas et al 2016;Hillwig et al 2016;Jones et al 2016;Madappatt et al 2016;Chen et al 2017;De Marco & Izzard 2017;Hillwig et al 2017;Sowicka et al 2017;Aller et al 2018;Barker et al 2018;Bujarrabal et al 2018;Iłkiewicz et al 2018;Jones 2018;Miszalski et al 2018b, for a sample of papers from the last 3 years; for a different model see García-Segura et al 2005). In some cases there is a direct link between the presence of a binary central star and the presence of jets (e.g., Boffin et al 2012;Miszalski et al 2013Miszalski et al , 2018a, and binary AGB systems and the presence of jets launched by the companion to the AGB star (e.g., Thomas et al 2013;Gorlova et al 2015;Bollen et al 2017;Van Winckel 2017).…”