C/2002 VQ94 (LINEAR) and 29P/Schwassmann-Wachmann 1 - CO⁺ and N₂⁺ rich comets

Abstract

We investigated comets active at large heliocentric distances using observations obtained at the 6-m BTA telescope (SAO RAS, Russia). Long-slit and photometric modes of the focal reducer SCORPIO were used. Two of the comets, 29P/Schwassmann-Wachmann 1 (SW1) and C/2002 VQ94 (LINEAR) were observed to be emission rich. Detection of CO⁺ and N₂ + emissions in the comae of these comets is evidence that they were formed in the outer regions of the Solar System or in a pre-solar interstellar cloud in a low temperature environment with T ~ 25K. The ratio of N₂⁺/CO⁺ is equal to 0.011 and 0.027 for SW1 and LINEAR, respectively. Comet LINEAR is the most distant object in the Solar System (7.332 AU) for which CO⁺ and N₂⁺ are measured. The photometric maximum of the isolated CO⁺ coma in comet LINEAR is shifted by 1.4 arcsec (7.44 × 103 km) relative to the photometric maximum of the dust coma. This shift deviates from the sunward direction by 63 degrees.