The rotational structure of the B-X system of sulfur dimers in the spectra of Comet Hyakutake (C/1996 B2)

We have constructed line-by-line fluorescence models for the ro-vibrational bands of the B-X system of sulfur dimers (S-2). For the first time the detailed rotational lines of the bands are clearly resolved in the high-resolution echelle spectra of Comet Hyakutake (C/1996 132), which were obtained at the Kitt Peak 4-m telescope on 26.4 March 1996 (UT). In order to construct satisfactory band models of the B-X system, we first compared the models to laboratory spectra available in literature, and then compared the models including Swings effects to the high-resolution spectra of Hyakutake. From the model fits, we derived a rotational temperature of 70 +/- 10 K, which should represent a temperature of a coma region close to the nucleus, where most of the S-2 emissions originate. We present previously proposed scenarios for the origin of S-2 in cometary comae, and compare them with our spectral analysis. (C) 2003 Elsevier Inc. All rights reserved.