Photometric observations of distant active comets

Free access article

Issue		A&A Volume 374, Number 2, August I 2001


Page(s)		712 - 718
Section		The solar system
DOI		http://dx.doi.org/10.1051/0004-6361:20010715

A&A 374, 712-718 (2001)
DOI: 10.1051/0004-6361:20010715

Photometric observations of distant active comets

Gy. M. Szabó¹, B. Csák^{1, 2}, K. Sárneczky³ and L. L. Kiss¹

¹ Department of Experimental Physics & Astronomical Observatory, University of Szeged, 6720 Szeged, Dóm tér 9, Hungary
² Department of Optics & Quantum Electronics & Astronomical Observatory, University of Szeged, POB 406, 6701 Szeged, Hungary
³ Department of Physical Geography, ELTE University, 1088 Budapest, Ludovika tér 2, Hungary

(Received 21 September 2000 / Accepted 17 April 2001 )

Abstract
We present CCD $VR_{\rm C}$ observations of 6 distant comets located at heliocentric distances of 3.4-7.2 AU. Time-series data were obtained on three nights in July, 2000 covering 16 hours. Each comet was observed after the perihelion, when a lower activity was expected. Contrary to expectation, we found well-defined circular comae and extended tails visible out to a few (3-5) arcmin. We detected a quasi-cyclic light variation of C/1999 J2, while C/1999 N4 showed some hints of a more complex variation. C/2000 K1 was constant to $\pm0.04$ mag during the observing run. The standard V and $R_{\rm C}$ data were used to estimate nuclear diameters, while the colour indices implied a slighly reddish ( $V-R=0\fm68$ , C/2000 K1), a neutral ( $V-R=0\fm47$ , C/1999 N4) and a slightly bluish ( $V-R=0\fm25$ , C/1999 J2) coma. Simple fits of the surface brightness distributions are also presented enabling order of magnitude estimates of nuclear radii. Beside the time-series observations, further single-shot observations of three faint comets are briefly described.

Key words: solar system -- comets: individual: C/1999 J2, C/1999 N4, C/2000 K1

Offprint request: L. L. Kiss, l.kiss@physx.u-szeged.hu

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