CN, NH, and dust in the atmosphere of comet C/1999 J3 (LINEAR)

¹ Main Astronomical Observatory, Ukrainian Academy of Sciences, Kyiv, Ukraine
² Isaac Newton Institute of Chile, Kiev Branch, Ukraine
³ Max-Planck-Institute for Aeronomy, Kaltenburg-Lindau, Germany e-mail: jockers@linmpi.mpg.de

Corresponding author: P. P. Korsun, korsun@mao.kiev.ua

Received: 31 July 2001
Accepted: 24 October 2001

Abstract

Comet C/1999 J3 (LINEAR) was observed with 2 m telescope of the Pik Terskol Observatory on September 19, 1999. Narrow-band CCD images of the CN, NH₂, and dust atmospheres were recorded with the Two-Channel focal reducer of the Max-Plank-Institute for Aeronomy. The distributions of the CN and NH₂ molecules in the comet atmosphere were fitted with a Monte Carlo model. For the CN atmosphere the best agreement between observed and calculated surface profiles was reached with the CN photodissociation lifetime  s and with the parent photodissociation lifetime  s. This result indicates that HCN is the main source of the CN radicals in the atmosphere of comet C/1999 J3 (LINEAR). Regarding the NH₂ radicals, there is no doubt that NH₃ is the dominant source of this species in the comet atmosphere. The lifetimes  s for NH₂ and  s for its parent are close to theoretical calculations. The gas-production rates of CN, mol s^-1, and NH₂,  mol s^-1 have also been determined. The appearance of the comet and the obtained data show that the comet is a gaseous one. The values are 21.6 cm for the blue spectral window and 23.4 cm for the red one. The normalized spectral gradient of the cometary dust is low, 4.0% per 1000 Å. The ratio log((/Q(CN)) = -24.25 indicates a very low dust to gas ratio as well.