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William Herschel Telescope observations of distant comets

Lowry, S.C., Fitzsimmons, A. (2005) William Herschel Telescope observations of distant comets. Monthly Notices of the Royal Astronomical Society: Letters, 358 (2). pp. 641-650. ISSN 1745-3933. (doi:10.1111/j.1365-2966.2005.08825.x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:52317)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
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We present results from broad-band V- and R-filter observations obtained at the 4.2-m William Herschel Telescope on La Palma on 2002 July 12-14. A total of six comets were imaged, and their heliocentric distances ranged from 2.8 to 6.1 au. The comets observed were 43P/Wolf-Harrington, 129P/Shoemaker-Levy 3, 133P/Elst-Pizarro, 143P/Kowal-Mrkos, P/1998 U4 (Spahr) and P/2001 H5 (NEAT). A detailed surface brightness profile analysis indicates that three of the targeted comets (43P/Wolf-Harrington, 129P/Shoemaker-Levy 3 and P/1998 U4) were visibly active, and the remaining three comets were stellar in appearance. Further analysis shows that for the three 'stellar-like' comets the possible coma contribution to the observed flux does not exceed 12.2 per cent, and in the case of comet 143P/Kowal-Mrkos the coma contribution is expected to be as low as 1 per cent, and so the resulting photometry most likely represents that of the projected nucleus surface. Effective radii for the inactive comets range from 1.02 to 4.56 km, and the effective radius upper limits for the active comets range from 1.94 to 4.15 km. We assume an albedo and phase coefficient of 0.04 and 0.035 mag deg^-1, respectively, with the exception of comets 133P/Elst-Pizarro and 143P/Kowal-Mrkos for which phase coefficients were previously measured. These values are compared with previous measurements, and for comet 43P/Wolf-Harrington we find that the nucleus axial ratio a/b could be as large as 2.44. For the active comets we measured dust production levels in terms of the Af-rho quantity. Spectral gradients were extracted for two of the inactive comets from their measured broadband colour indices, and compared with the rest of the comet population for which (V - R) colour and spectral gradient values exist. We find a spectral gradient for 143P/Kowal-Mrkos of 9.9 ± 8.1 per cent/100 nm, which is very typical of Jupiter-family comets, the majority of which have reflectivity gradients in the range 0-13 per cent (100 nm)^-1. The spectral gradient for comet 133P/Elst-Pizarro is amongst the bluest yet measured. We measure a (V - R) colour index value of 0.14 ± 0.11 for the nucleus of 133P/Elst-Pizarro which is considerably lower than previous measurements. A possible explanation for this difference is considered. © 2005 RAS.

Item Type: Article
DOI/Identification number: 10.1111/j.1365-2966.2005.08825.x
Additional information: Unmapped bibliographic data: LA - English [Field not mapped to EPrints] J2 - Mon. Not. R. Astron. Soc. [Field not mapped to EPrints] AD - Astrophys. and Planet. Sci. Division, Department of Physics and Astronomy, Queen's University Belfast, Belfast BT7 1NN, United Kingdom [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Comets: general
Subjects: Q Science > QB Astronomy
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Stephen Lowry
Date Deposited: 08 Dec 2015 23:05 UTC
Last Modified: 16 Nov 2021 10:21 UTC
Resource URI: (The current URI for this page, for reference purposes)

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