Anomalous wavelength dependence of polarization of Comet 21P/Giacobini-Zinner

Kiselev, N. N.; Jockers, K.; Rosenbush, V. K.; Velichko, F. P.; Bonev, T.; Karpov, N. V.

doi:10.1016/s0032-0633(00)00069-6

Cited by 39 publications

(46 citation statements)

References 15 publications

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“…For the bands of CN and C 2 p 90 = 0.077, while for the C 3 polarization p 90 = 0.19 is expected. For the diatomic molecules CN and C 2 the observations (Le Borgne et al 1986;Le Borgne & Crovisier 1987;Kiselev 2003) are in good agreement with the theoretical calculations. For C 3 , however, the polarization degree observed by Le Borgne et al (1986) was lower than the theoretical value.…”

Section: Aperture Resultssupporting

confidence: 71%

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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Section: Aperture Resultssupporting

confidence: 71%

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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“…It belongs to the group of comets depleted in C 2 , C 3 (A' Hearn et al 1995), and C 2 H 6 (Weaver et al 1999;Mumma et al 2000). Anomalous wavelength-dependence of polarization was also observed (Kiselev et al 2000). We, however, do not think that 21P/G-Z and Draconids are exceptional.…”

Section: Discussionmentioning

confidence: 73%

Atmospheric deceleration and light curves of Draconid meteors and implications for the structure of cometary dust

Borovička

Spurný

Koten

2007

A&A

117

124

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Aims. The observation of Draconid meteors was used to infer information on the structure, porosity, strength, and composition of the dust of comet 21P/Giacobini-Zinner. Methods. Stereoscopic video and photographic observations of six faint and one bright Draconid meteors provided meteor morphologies, heights, light curves, and atmospheric decelerations. The spectrum of the bright meteor was also obtained. We developed a simple model of meteoroid ablation and fragmentation. The model assumes that cometary meteoroids are composed of constituent grains.Results. By fitting the observed decelerations and light curves, we have found that the grain mass range was relatively narrow in all meteoroids but differed from case to case. Some meteoroids were coarse grained with grain masses 10 −9 to 10 −10 kg, others were fine grained with grain masses one order of magnitude lower. Individual mm-sized meteoroids contained tens of thousands to almost a million grains (assuming grain density close to 3000 kg m −3 ). The meteoroids were porous aggregates of grains, having porosities of about 90% and bulk densities of 300 kg m −3 . Grain separation started after the surface of the meteoroid received energy of 10 6 J m −2 . The separation continued during the first half of meteor trajectories. We call this phase erosion. The energy needed for grain erosion was 15−30× lower than the energy of vaporization. However, 30% of the largest meteoroid was resistant to thermal erosion; this part disrupted later mechanically under a very low dynamic pressure of 5 kPa. The relative abundances of Na, Mg, and Fe were nearly chondritic, but differential ablation caused preferential loss of sodium at the beginning of the trajectory.

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“…• in comet 21P/Giacobinni-Zinner (Kiselev et al 2000), a blue polarimetric color was explained by large abundance of organic materials or by large dust particles; • for comet Hale-Bopp (Kelley et al 2004), the polarimetric color was blue in the infrared although red in the optical. However, this result is uncertain due to the need to extrapolate the observations in time and phase angle; • for comet 9P/Tempel-1, a blue polarimetric color was observed right after Deep Impact (Harrington et al 2007).…”

Section: Polarizationmentioning

confidence: 98%

Evidence of Fragmenting Dust Particles From Near-Simultaneous Optical and Near-Infrared Photometry and Polarimetry of Comet 73p/Schwassmann-Wachmann 3

Jones

Stark

Woodward

et al. 2008

The Astronomical Journal

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We report imaging polarimetry of segments B and C of the Jupiter-family comet 73P/Schwassmann-Wachmann 3 in the I and H bandpasses at solar phase angles of approximately 35• and 85• . The level of polarization was typical for active comets, but larger than expected for a Jupiter-family comet. The polarimetric color was slightly red (δP /δλ = +1.2 ± 0.4) at a phase angle of ∼35• and either neutral or slightly blue at a phase angle of ∼85 • . Observations during the closest approach from 2006 May 11-13 achieved a resolution of 35 km at the nucleus. Both segments clearly depart from a 1/ρ surface brightness for the first 50-200 km from the nucleus. Simulations of radiation-driven dust dynamics can reproduce some of the observed coma morphology, but only with a wide distribution of initial dust velocities (at least a factor of 10) for a given grain radius. Grain aggregate breakup and fragmentation are able to reproduce the observed profile perpendicular to the Sun-comet axis, but fit the observations less well along this axis (into the tail). The required fragmentation is significant, with a reduction in the mean grain aggregate size by about a factor of 10. A combination of the two processes could possibly explain the surface brightness profile of the comet.

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Anomalous wavelength dependence of polarization of Comet 21P/Giacobini-Zinner

Cited by 39 publications

References 15 publications

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

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

Atmospheric deceleration and light curves of Draconid meteors and implications for the structure of cometary dust

Evidence of Fragmenting Dust Particles From Near-Simultaneous Optical and Near-Infrared Photometry and Polarimetry of Comet 73p/Schwassmann-Wachmann 3

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