CCD imaging polarimetry of Comet 2P/Encke

Kiselev, N. N.; Jockers, K.; Bonev, T.

doi:10.1016/j.icarus.2003.12.012

Cited by 31 publications

(22 citation statements)

References 29 publications

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“…Rosenbush et al (2002) where dust concentration is very high but in the outer coma gas dominates which result in the steep fall in polarization value. The similar trend of strong radial dependence of polarization with increasing aperture size is also being observed for gaseous Comets C/1996 Q1 (Tabur) (Kiselev et al (2001)) and 2P/Encke (Kiselev et al (2004), Jewitt (2004). It is also observed that dusty comets do not show steep radial dependence of polarization with increasing aperture size (see, e.g., Manset & Bastien (2000)).…”

Section: Discussionsupporting

confidence: 74%

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

Roy

Das

Medhi

2015

Icarus

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Section: Discussionsupporting

confidence: 74%

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

Roy

Das

Medhi

2015

Icarus

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“…Figure 3 shows the polarization of comet 2P/Encke derived from imaging polarimetry for several square apertures and from photoelectric observations. Data from the previous paper (Kiselev et al 2004) for an area of 2000 km 2 are also included. The full line presents the phase angle dependence of polarization for resonance fluorescence according to Eq.…”

Section: Aperture Resultsmentioning

confidence: 99%

CCD imaging and aperture polarimetry of comet 2P/Encke: are there two polarimetric classes of comets?

Jockers¹,

Kiselev²,

Bonev³

et al. 2005

A&A

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Abstract. We present results of imaging and aperture polarimetry of the dust of comet 2P/Encke at phase angles [91][92][93][94][95][96][97][98][99][100][101][102][103][104][105] • , obtained during the 2003 apparition. We investigate how strongly molecular emissions transmitted by the filters used in the observations can affect the resulting polarization of cometary dust. This problem is of particular importance for so-called gasrich comets like comet 2P/Encke which has particularly strong molecular emission as compared to its dust continuum. Aperture polarimetry in the wide-band UBVR filters was performed at the 2.6-m Shain telescope and 1.25-m telescope of the Crimean Astrophysical Observatory on November 17-24. From these measurements a dust polarization of ≈8% is derived, which puts the comet in the class of comets with low polarization. The imaging observations of comet 2P/Encke were carried out at the 2-m telescope of the Bulgarian National Astronomical Observatory on November 20-22, 2003. Narrow-band filters centered on the 0-7-0 transition of the Ã 2 A 1 -X 2 B 1 electronic band system of NH 2 (662 nm) and on an adjacent red continuum at 642 nm were employed. The polarization of NH 2 averaged over the 0-7-0 vibronic transition amounts to ≈7% at phase angles close 90• , similar to the polarization of the two-atomic molecules CN and C 2 . The dust polarization however, when corrected for the effect of molecular emissions, is larger than 30%. We conclude that the division of comets into two polarimetric classes with one class having in the visual wavelength range a maximum polarization less than 20% is caused by ignoring the contribution of molecular emission and therefore is an artifact. Whether the comet displays a strong silicate feature (i.e. its dust grains are small) or not, the dust polarization is high.

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“…The existence of the polarization classes may be related to differences in the bulk properties of the dust, such as albedo, size distribution, and porosity (Levasseur-Regourd et al 1996). On the other hand, Kiselev et al (2004) underline the problem of gas contamination in polarimetric measurements with wide-band filters and consequent depolarizing effects on light scattered by dust. It is therefore possible that the trichotomy in polarization is an artefact and that the cometary dust in the coma is characterized in all cases by high values of P max .…”

Section: Introductionmentioning

confidence: 99%

Modeling of the light scattering properties of cometary dust using fractal aggregates

Bertini

Thomas

Barbieri

2006

A&A

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Aims. The nature of cometary dust is still elusive. In order to constrain the physical properties of dust in cometary coma, we modeled the observed scattering parameters, investigating different morphological and compositional effects. Methods. We used fractal aggregates as dust particles. The scattering behavior of extremely elongated dust particles, similar to those formed in micro-gravity aggregation experiments and more compact aggregates, have been studied with the discrete-dipole approximation theory. Results. Results show that particles comparable in size to the incident wavelength provide the best qualitative fits. A silicate composition gives a good fit to the polarization and the phase function, but is characterized by large albedo. Organic and mixed compositions provide low albedos but do not fit the polarization and phase function curves well. Compact particles seem to reproduce the observed parameters better, indicating a possible morphological metamorphism of dust since the time of formation. The observed different polarization classes may be explained in terms of different monomer sizes, if a cluster of spheres models are used.

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CCD imaging polarimetry of Comet 2P/Encke

Cited by 31 publications

References 29 publications

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

CCD imaging and aperture polarimetry of comet 2P/Encke: are there two polarimetric classes of comets?

Modeling of the light scattering properties of cometary dust using fractal aggregates

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