Polarimetric study of 8 Kreutz comets observed by STEREO
Abstract
Few Kreutz group near-Sun comets have been analysed to date - the exception is the bright comet C/2011 W3 (Lovejoy). We present analysis of eight of the brightest Kreutz group comets observed with the wide-field Lyot coronographs of the twin STEREO spacecraft. Near-Sun comets are excellent candidates for sampling a wider range of phase angles which are usually unobservable due to geometric constraints. The twin STEREO spacecraft feature a linear polariser permanently in the optical path of their two coronographs. They perform a rapid sequence of three polarimetric images with different polariser angles at least once per hour. A bespoke method for polarimetric analysis of this coronograph data, focusing on the signal of the comet and its dust tail, has been developed. It utilises known orbital properties of the comets to recombine the image triplets and produce a phase angle curve for the cometary observations. Polarisation consistently increases with distance from comet nucleus. Concerning the phase angle curve, some comets diverge significantly from the expected behaviour.
- Publication:
-
EPSC-DPS Joint Meeting 2019
- Pub Date:
- September 2019
- Bibcode:
- 2019EPSC...13.1698N