We performed a detailed spectroscopic analysis of the fullerene C _ { 60 } -containing planetary nebula ( PN ) Lin49 in the Small Magellanic Cloud using XSHOOTER at the ESO VLT and the Spitzer /IRS instruments .
We derived nebular abundances for nine elements .
We used TLUSTY to derive photospheric parameters for the central star .
Lin49 is C-rich and metal-deficient PN ( Z \sim 0.0006 ) .
The nebular abundances are in good agreement with Asymptotic Giant Branch nucleosynthesis models for stars with initial mass 1.25 M _ { \odot } and metallicity Z = 0.001 .
Using the TLUSTY synthetic spectrum of the central star to define the heating and ionising source , we constructed the photoionisation model with CLOUDY that matches the observed spectral energy distribution ( SED ) and the line fluxes in the UV to far-IR wavelength ranges simultaneously .
We could not fit the \sim 1-5 \mu m SED using a model with 0.005-0.1 \mu m-sized graphite grains and a constant hydrogen density shell owing to the prominent near-IR excess , while at other wavelengths the model fits the observed values reasonably well .
We argue that the near-IR excess might indicate either ( 1 ) the presence of very small particles in the form of small carbon clusters , small graphite sheets , or fullerene precursors , or ( 2 ) the presence of a high-density structure surrounding the central star .
We found that SMC C _ { 60 } PNe show a near-IR excess component to lesser or greater degree .
This suggests that these C _ { 60 } PNe might maintain a structure nearby their central star .