PN Tc 1 MUSE imaging spectroscopy

The spectrum of the central star was extracted and fitted by a 31000K model atmosphere and is of type O7.5I(f). The image of optical extinction from H Balmer line ratios is highly structured, and shows an annulus, which is adjacent to the core, of low extinction, with values lower than the line-of-sight interstellar extinction. Instrumental effects to account for this anomalously low extinction area were investigated and intrinsic effects from the scattering properties of the nebular dust; neither can entirely explain the low-extinction region and the most likely cause is a local non-standard dust reddening law.

This low extinction region additionally shows an anomalously high HeI 7281/6678{AA} line ratio, possibly caused by a contaminating line, but none have been conclusively identified; its origin remains unresolved. Spectra over extended regions were also analysed and distinct enhancement of the continuum above the expected nebular continuum (as also seen in some other PNe observed with MUSE) was found. The annulus of low extinction occurs outside the region of strongest fullerene emission, in the zone where N_e_ declines and T_e_ rises.

A change in dust properties linked to conditions in this transition region between the higher density core nebula and lower density halo is deduced.