Distant Jupiter family Comet P/2011 P1 (McNaught)

Abstract

The spectra and images obtained through broadband BVRc filters for Jupiter family Comet P/2011 P1 (McNaught) were analyzed. We observed the comet on November 24, 2011, when its heliocentric distance was 5.43AU. Two dimensional long slit spectra and photometric images were obtained using the focal reducer SCORPIO attached to the prime focus of the 6-m telescope BTA (SAO RAS, Russia). The spectra cover the wavelength range of 4200–7000Å. No emissions of C2 and CO+, which are expected in this wavelength region, were detected above 3σ level. An upper limit in gas production rate of C2 is expected to be 1.1×1024mols−1. The continuum shows a reddening effect with the normalized gradient of reflectivity along dispersion of 5.1±1.2% per 1000Å. The color indices (B–V)=0.89±0.09 and (V–Rc)=0.42±0.07 for the nucleus region or (B–V)=0.68±0.12 and (V–Rc)=0.39±0.10 for the coma region, which are derived from the photometric data, also evidence that the color of the cometary nucleus and dust are redder with respect to the Sun. The normalized gradients of 5.9±2.9% per 1000Å and 2.6±1.9% per 1000Å for VRc filters were obtained for the cometary nucleus and the dust coma, respectively. The estimated dust mass production rate is about 12kgs−1 for Rc filter. The dust coma like a spiral galaxy edge-on was fitted using a Monte Carlo model. Since it is expected that the particles forming the dust coma consist of “dirty” ice, Greenberg’s model was adopted to track grains with an icy component that evaporates slowly when exposed to solar radiation. The observed coma was fitted assuming two isolated active zones located at the cometocentric latitudes of −8° and −35° with outflow of the dust within the cones having half opening angles of 8° and 70°, respectively. About, 45% and 55% of the observed dust were originated from the high collimated and low collimated active zones, respectively. The spin-axis of the rotating nucleus is positioned in the comet’s orbit plane. The sizes of the dust particles were ranged from 5μm to 1mm with a power index of −3.0 for the adopted exponential dust size distribution.