The distant activity of the Long Period Comets C/2003 01 (LINEAR) and C/2004 K1 (Catalina)

Abstract

Aims. We study the distant dust environment of two Long Period Comets: C/2003 Ol (LINEAR) (observed at rh = 7.39 AU) and C/2004 Kl (Catalina) (observed at rh = 3.43 AU). The case of C/2003 Ol is particularly interesting since the comet has a quite large perihelion heliocentric distance (rh = 6.85 AU). Methods. We analysed R-band images taken at the CAHA 2.2 m telescope to characterise the properties of the cometary dust coma. The images of both comets were also used as input into an inverse numerical model, to derive information about the dynamical parameters of coma dust grains until a time ∼500 days before the observation. Results. Both the comets appeared to be active, and of similar shape and size despite the great difference in their heliocentric distance of observation. C/2003 Ol exhibited a tail extending to at least 3.7 X 105 km. It is a very active object, since its Afp is -552 ± 36 cm. within the inner 5″. C/2004 K1 showed, a similar long tail, extending to 2.6 X 105 km. Its Afp is 539 ± 35 cm within the inner 5″. An almost constant dust grain ejection velocity between 0.5 and 0.9 m/s at 1 cm dust size has been derived for C/2003 Ol and an increase from. 0.5 to 2 m/s at 1 cm dust size for C/2004 Kl, reflecting the different volatile dragging the dust environment (probably CO for C/2003 O1 and water for C/2004 Kl). Model results allow some speculations about the comet nucleus size of C/2003 Ol (LINEAR) and its CO content: for a Qco similar in value to those observed, for other distant cometary objects, a comet radius Rn from 13 to 17 km can be inferred. © ESO 2009.