Abstract. We present observations of comet C/1999 S4 (LINEAR) obtained in the period November 1999 to July 29, 2000. The observations were carried out with FoReRo (Focal Reducer Rozhen) attached to the 2-m telescope of the National Astronomical Observatory, Rozhen. Narrow-band images were taken in the CN-emission at 388 nm and in a continuum window at 443 nm. Aperture photometry applied to the images from November 1999, when the comet was at a heliocentric distance, r = 3.8 AU, shows a marginally detectable CN contribution above the continuum. In February 2000, at r = 2.8 AU, the CN coma was reliably detected by synthetic aperture photometry around the nucleus but no spatial coma morphology can be distinguished at this time. After May 30, 2000, at heliocentric distances shorter than 1.3 AU, the CN coma morphology was sufficiently evolved to allow the construction of mean profiles. We analyse these profiles with special stress on the days close to the perihelion when the comet disintegrated. The profiles are calibrated to column densities. The variation of the CN production rate with heliocentric distance is discussed.

Full-text: PDF