Polarimetry, photometry, and spectroscopy of comet C/2009 P1(Garradd)

TL;DR

This study provides comprehensive polarimetric, photometric, and spectroscopic observations of comet C/2009 P1(Garradd), revealing dust and gas features, molecular emissions, and polarization characteristics across two post-perihelion epochs.

Contribution

It offers detailed multi-epoch polarimetric and spectroscopic data of comet Garradd, including polarization maps, molecular emissions, and nucleus rotation period, enhancing understanding of cometary dust and gas properties.

Findings

Detected molecular emissions of C2, C3, CN, CH, NH2, CO+, H2O+

Measured polarization levels and their spatial variation

Determined the comet's nucleus rotation period as 11.1 hours

Abstract

We present the results of photometry, linear spectropolarimetry, and imaging circular polarimetry ofcomet C/2009 P1 (Garradd) performed at the 6-m telescope BTA of the Special Astrophysical Observatory(Russia) equipped by the multi-mode focal reducer SCORPIO-2. The comet was observed at two epochspost-perihelion: on February 2-14, 2012 at r=1.6 au and {\alpha}=36 {\deg}; and on April 14-21, 2012 at r=2.2 au and {\alpha}=27 deg. The spatial maps of the relative intensity and circular polarization as well as the spectral distribution of linear polarization are presented. There were two features (dust and gas tails) orientedin the solar and antisolar directions on February 2 and 14 that allowed us to determine rotation periodof the nucleus as 11.1 hours. We detected emissions of C2 , C3 , CN, CH, NH2 molecules as well as CO+ and H2O+ ions, along with a high level of the dust continuum. On February 2, the degree of linear polarization in the continuum, within the wavelength range of 0.67-0.68 {\mu}m, was about 5% in the near-nucleus region up to near 6000 km and decreased to about 3% at near 40,000 km. The left-handed (negative) circular polarization at the level approximately from -0.06% to -0.4% was observed at the distances up to 3*10^4 km from the nucleus on February 14 and April 21, respectively.