Optical polarimetry of Comet NEAT C/2001 Q4

TL;DR

This study presents optical polarimetry observations of Comet NEAT C/2001 Q4, revealing high polarization levels and insights into its grain composition, with variations linked to cometary activity and observational geometry.

Contribution

First detailed optical polarization measurements of Comet NEAT C/2001 Q4 across multiple bands and locations, providing new insights into its dust properties and activity.

Findings

Polarization increases with wavelength at observed phase angles.

Polarization color varies with epoch, indicating activity or contamination.

Comet's dust likely consists of silicates and organics.

Abstract

Comet NEAT C/2001 Q4 was observed for linear polarization using the optical polarimeter mounted at the 1.2m telescope at Mt. Abu Observatory, during the months of May and June 2004. Observations were conducted through the International Halley Watch narrow band (continuum) and B,V,R broad band filters. During the observing run the phase angle ranged from 85.6 deg in May to 55 deg in June. As expected, polarization increases with wavelength in this phase angle range. Polarization colour in the narrow bands changes at different epochs, perhaps related to cometary activity or molecular emission contamination. The polarization was also measured in the cometary coma at different locations along a line, in the direction of the tail. As expected, we notice minor decrease in the polarization as photocenter (nucleus) is traversed while brightness decreases sharply away from it. Based on these polarization observations we infer that the comet NEAT C/2001 Q4 has high polarization and a typical grain composition- mixture of silicates and organics.