Modeling S Cometary Fluorescence Spectra
C. Laffont (Observatoire de Besançon), D.C. Boice (Southwest Research Institute)
We present synthetic cometary fluorescence spectra of the system of S , calculated as a function of exposure time of the molecule to the solar irradiation. The model S molecule contains 36 vibrational levels. To solve the 36 evolution equations governing the population of these levels, we used the Gear method for still differential equation systems where time constants vary by many orders of magnitude.
The initial population of the vibrational levels is obtained with a
Boltzmann temperature of about 200 K, typical of expanding gas at the
surface of a cometary nucleus in the inner solar system. We calculated
fluorescence spectra as a function of time after release of the molecule
from the nucleus, from very short times (several ns) to the steady
state (about 700 s). The synthetic S spectra obtained using this
method are compared to previous modeling efforts and to IUE spectra
of comets IRAS-Araki-Alcock and Hyakutake.