Giacobini-Zinner comet: Polarimetric and physical observations

The results of observations of the Giacobini-Zinner comet on 25 and 31 October 1959 are presented. The magnitude of the comet was measured photoelectrically in two spectral regions. The radius is on the order of one kilometer. The photoelectric measurements of comets 1959b and 1957c were used to measure the abundances of the CN and C2 radicals and of solid particles in the heads

Mécanisme d'excitation des bandes de Swan des comètes

Les spectres à haute résolution de la comète Mrkos (1957d) révèlent, dans ses grands traits, la structure rotationelle des bandes de Swann. Les anomalies d'intensité de certaines raies des bandes (1-0) et (2-1) s'expliquent par la présence de raies d'absorption dans le rayonnement solaire exitateur. Les bandes de Swann de C2 sont excitées par fluorescence, quoique leur niveau inférieur 3pi-u ne soit pas le niveau électronique normal de C2.The high resolution spectrograms of Comet Mrkos (1957d) reveal the essential features of the rotational structure of the Swan-bands. Intensity anomalies observed within the (1 - 0) and (2 - 1) transitions are due to the presence of absorption lines in the exciting solar radiation. It is thus proved that the Swan bands are excited by fluorescence, although their lower level 3πu is not the ground electronic state of C2

A fluorescence model of the C[SUB]3[/SUB] radical in comets

Theoretical resonance fluorescence calculations are presented of the triatomic C[SUB]3[/SUB] radical and are compared with observations of the C[SUB]3[/SUB] emission in comets Hale-Bopp and de Vico. A theoretical model of the C[SUB]3[/SUB] vibration-rotational structure in the A[SUP]1[/SUP]Pi[SUB]u[/SUB] - X[SUP]1[/SUP]Sigma[SUB]g[/SUB] [SUP]+[/SUP] electronic system is introduced. The model takes into account the detailed structure of the bending mode nu[SUB]2[/SUB] which is responsible for the emission of the 4050 à group. A total of 1959 levels are considered, with 515 levels in the ground state. The main effort is to model high-resolution spectra of the 4050 à emission in comets C/1995 O1 Hale-Bopp and 122P/1995 S1 de Vico. The agreement between observed and theoretical spectra is good for a value of the dipole moment derivative of dmu/dr ~ 2.5 Debye à [SUP]-1[/SUP]. The modeled C[SUB]3[/SUB] emission exhibits a pronounced Swings effect. Based on observations made with William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and on observations made at the McDonald Observatory, which is operated by the University of Texas at Austin, USA