Imaging Polarimetry and Color of the Inner Coma of Comet Hale-Bopp(C/1995 O1)

Furusho, Reiko; Suzuki, Bunji; Yamamoto, Naotaka; Kawakita, Hideyo; Sasaki, Toshiyuki; Shimizu, Yasuhiro; Kurakami, Tomio

doi:10.1093/pasj/51.3.367

Cited by 27 publications

(21 citation statements)

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“…On polarization maps, highly polarized regions correspond to jet-like and arc features (Hadamcik et al 1997;Jockers et al 1997;Jones et al 1997;Furusho et al 1999), as previously observed for 1P/Halley (Eaton et al 1988), C/1990 K1 Levy (Renard et al 1992), C/1996 B2 Hyakutake .…”

Section: Introductionsupporting

confidence: 79%

“…The April 1997 polarization maps are in complete agreement with those of Jockers et al (1997) and Furusho et al (1999) in the visible domain. The polarization in the arcs decreases when the dust moves away from the nucleus.…”

Section: Comparison With Other Polarization Maps Of Comet Hale-boppsupporting

confidence: 68%

“…8 (data are from: Hadamcik et al 1997;Jockers et al 1997;Kiselev et al 1997;Ganesh et al 1998;Furusho et al 1999;Manset & Bastien 2000). The data may be compared to those obtained for 1P/Halley (Fig.…”

Section: Phase Curvesmentioning

confidence: 99%

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Dust evolution of comet C/1995 O1 (Hale-Bopp) by imaging polarimetric observations

Hadamcik

Levasseur-Regourd

2003

A&A

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Abstract. Comet C/1995 O1 (Hale-Bopp) has been observed over a large range of phase angles (7• -47 • ) by the imaging polarimetric method from June 1996 to April 1997. Polarization maps were obtained and long-term evolution (month) of the coma structures followed. Short-term evolution (20 min) during the April 1997 observations has allowed us to measure the period of rotation of the central arc on the polarization maps. The comparison between the polarization maps and the intensity structures confirms a greater polarization in the jets. Phase curves are obtained for different regions of the coma and compared to those obtained for the whole coma. For the region around the nucleus, the phase curve is always underneath the phase curve corresponding to the whole coma, and the polarization at phase angles smaller than 25• is negative (P min = −5%). In the jets, the phase curve is always above the whole coma phase curve, and the polarization is always positive. Whole coma phase curves are obtained with all the available data sets in different wavelengths. A comparison with other diagnostics and laboratory experiments leads us to suggest that small grains build up fluffy aggregates of high porosity; the light scattered by such aggregates is highly polarized, as observed in this active comet.

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Section: Introductionsupporting

confidence: 79%

Section: Comparison With Other Polarization Maps Of Comet Hale-boppsupporting

confidence: 68%

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Dust evolution of comet C/1995 O1 (Hale-Bopp) by imaging polarimetric observations

Hadamcik

Levasseur-Regourd

2003

A&A

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“…This might cause some change in the degree of polarization provided the sampled region is heterogeneous. The inner coma region of comets has been found to be quite heterogeneous in the spatial distribution of dust, which in turn is responsible for the spatial variation of polarization in the inner region Eaton et al 1988Eaton et al , 1991Dollfus & Suchail 1987;Jockers et al 1999;Furusho et al 1999;Kolokolova et al 2001). In the case of Comet Halley a fair degree of agreement is seen among the observations made by different groups with different aperture sizes as long as the polarization is estimated over the whole coma with a large aperture centered on the nucleus which averages out the effect of heterogeneity.…”

Section: Discussionmentioning

confidence: 99%

Polarization studies of comet C/2000 WM1 (LINEAR)

Joshi

Baliyan

Ganesh

2003

A&A

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• ) when the polarization is negative and where the data for most of the comets are rather meager. The observations during March were made when the phase angle was ∼47• . Observations were conducted through the IHW narrow band and BVR broad band filters. Based on these polarization observations we infer that the comet C/2000 WM1 belongs to high polarization class i.e. the dusty comet family.

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“…3. As the colour of the grains do not change drastically with phase angle, we set a conservative limit of 5−10% per 1000Å on the shells and 10−20% per 1000Å on the regions between the shells representing the coma based on the colour reported by Bellucci (1998), Furusho et al (1999), Kiselev & Velichko (1997) and Kolokolova et al (2001). 4.…”

Section: Observational Inputsmentioning

confidence: 99%

A photometric-dynamic model to simulate coma and jets from a comet

Vasundhara

2002

A&A

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Abstract.A model to compute the trajectories of dust grains ejected by comets to simulate intensity and polarization maps on the sky plane is presented. The model is used to constrain the silicate to organic mass ratio, porosity and size distribution of the grains in the shells and coma of comet Hale-Bopp to explain 1) the published polarizations at three continuum wavelengths at 0.6840 µm, 0.4845 µm and 0.3650 µm at different phase angles, 2) higher polarization and bluer colour of the shells compared to the coma, 3) the intensity variation and rapid decline of polarization on the sunward side and 4) higher polarization on the anti-sunward direction. The present results obtained using Mie theory in the model indicate that although it is impossible to determine the nature of the silicate (pyroxenes/olivines or amorphous/crystalline) using the present technique, the porosity, organic fraction and size distribution of the grains can be constrained. The fit to the data set indicates an ensemble of grains in which ≈60% are silicate grains with a range in silicate to organic mass ratio rm between 1 and 2 and of medium porosity <50%. A higher silicate content of rm > 8 on the shells can explain their bluer colour. A narrow size distribution between 0.08 µm−0.6 µm is inferred for 70% of the grains in the coma and shell. These small grains may not be individual grains but part of loosely bound grains in which larger grains may also be present which may control the dynamics. The narrow size distribution may therefore represent statistically the size range of individual subunits of larger highly porous aggregates of fractal dimension close to two. The polarizations in JHK bands also support the aggregate structure. Despite the availability of an extensive and wide range of data set on this comet, the inclusion of a large parameter space, lack of knowledge on the nature of organic material found in comets and use of Mie theory, which does not adequately represent the polarization phase curves of natural grains, set limitations in getting a unique solution in the present work. The results presented here are open to improvements when more realistic light scattering theories are used in the model and our understanding on the nature of the organic content of the grains improves. However, visibility of up to 8-10 shells in well exposed images implies β < 1 for these grains. As a result of this dynamical constraint which is independent of the assumptions on the scattering characteristics of the grains, the results for the dust grains in the shell may be more robust compared to that of the coma.

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Imaging Polarimetry and Color of the Inner Coma of Comet Hale-Bopp(C/1995 O1)

Cited by 27 publications

References 0 publications

Dust evolution of comet C/1995 O1 (Hale-Bopp) by imaging polarimetric observations

Dust evolution of comet C/1995 O1 (Hale-Bopp) by imaging polarimetric observations

Polarization studies of comet C/2000 WM1 (LINEAR)

A photometric-dynamic model to simulate coma and jets from a comet

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