Ranked values of the abundance discrepancy O2+ abundance discrepancy Hii regions Planetary nebulae Planetary nebulae with close binary central stars 1000 100 10 1

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This is a list of 227 literature values of the abundance discrepancy factor for O2+, which is hopefully complete. It was last updated on 9 Jan 2024. One value, for the HII region LMC N11B, is omitted as it was later found to be in error. In other cases where the same object has been analysed more than once, all measurements are shown. The data on fluxes, velocities, morphologies, sizes and distances were collected with the help of several other attendees at the WorkPLANS meeting in Leiden in February 2016. The HASH PNe database has also been of great use in compiling and maintaining this page.

Object type:

ObjectDiscrepancyTypeReferencePNGRADecDiameter (arcseconds)MorphologylogF(Hβ)I(4363)I(5007)Vexp ([OIII])Vexp ([NII])Distance (kpc)

Abundance discrepancies in close binaries

In Wesson et al. (2018), we proposed that there is a threshold period of about 1.15 days, with only the shorter period binaries showing adfs >5, and longer periods binaries having adfs <5. This plot shows adf(O2+) against binary period for the 22 objects where both are measured, with an upper limit indicated for the Necklace Nebula. adf(O2+)=5 and P=1.15 d are indicated with horizontal and vertical dashed lines.

Subsequently there have been several new detections of binary central stars in nebulae with a measured adf. NGC 2392, NGC2867 and MyCn18 have periods of 1.9, 4.54 and 18.15 days respectively, putting them in the bottom right quadrant where we would have predicted them to, based on their low adf. Meanwhile, a binary period of 1.06 days has been proposed for Abell 30, placing it in the top left quadrant, also as predicted.

However, a binary period and adf were published for Sp 3 in August 2019, and these place it far from the other nebulae in the diagram, in a region of parameter space where it is currently unique.

Abundance discrepancy against binary period O2+ abundance discrepancy Binary period (days) 0.1 1 10 100 1 10 100 1000

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Densities v. abundance discrepancies

In Wesson et al. (2018), we investigated the relations between adfs and densities. As measured by [Sii] lines, the highest adfs occur in the lowest density planetary nebulae, while in Hii regions, there is no relation. Densities measured from [Oii] lines are spuriously high in extreme-adf objects, due to recombination enhancing the line fluxes. This plot shows the [Sii] densities, with the points moving to indicate the [Oii] densities when you click on it.

Electron density against abundance discrepancy O2+ abundance discrepancy [S ii] density (cm-3) 10 100 1000 10000 1 10 100

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