388 research outputs found
Evolution of PAH Features from Proto- to Planetary Nebulae
With the aim to investigate the overall evolution of UIR band features with
hardening of UV radiation (increase of the star's effective temperature) we
have analysed ISO spectra for 32 C-rich stars: 20 proto-planetary nebulae and
12 planetary nebulae with Wolf-Rayet central stars. In this contribution we
discuss variations in the peak position of UIR bands among analysed objects,
and demonstrate that variations in the ``7.7'' to 11.3 microns flux ratio are
correlated with the effective temperature (probably due to an increase of the
ionization state of their carriers).Comment: 4 pages, 3 figures, 1 table, to appear in the Proceedings of the
conference "Planetary Nebulae as Astronomical Tools", edited by R. Szczerba,
G. Stasi\'nska, and S. K. G\'orny, AIP Conference Proceedings, Melville, New
Yor
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