EDP Sciences
Free Access
Issue
A&A
Volume 387, Number 3, June I 2002
Page(s) 1107 - 1113
Section The solar system
DOI https://doi.org/10.1051/0004-6361:20020494


A&A 387, 1107-1113 (2002)
DOI: 10.1051/0004-6361:20020494

VLT observations of comet 46P/Wirtanen

H. Boehnhardt1, C. Delahodde1, T. Sekiguchi1, G. P. Tozzi2, R. Amestica1, O. Hainaut1, J. Spyromilio3, M. Tarenghi3, R. M. West3, R. Schulz4 and G. Schwehm4

1  European Southern Observatory ESO, Alonso de Cordova 3107, PO Box 19001, Santiago 19, Chile
    e-mail: hboehnha@eso.org;cdelahod@eso.org;tsekiguc@eso.org;ohainaut@eso.org;ramestic@eso.org
2  Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50125 Firenze, Italy
    e-mail: tozzi@arcetri.astro.it
3  European Southern Observatory ESO, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
    e-mail: jspyromi@eso.org;mtarengh@eso.org;rwest@eso.org
4  European Space Agency ESA, ESTEC, Keplerlaan, 2200 AG Noordwijk, The Netherlands
    e-mail: rschulz@estec.esa.nl;gschwehm@estec.esa.nl

(Received 4 December 2001 / Accepted 28 March 2002 )

Abstract
Comet 46P/Wirtanen, prime target of ESA's ROSETTA mission, was successfully observed at the Very Large Telescope Observatory in Chile: on 17 May 1999 with the Test Camera at the Cassegrain focus of the 8.2-m VLT Kueyen telescope and on 8 December 2001 with FORS1 at Unit Telescope 4 Yepun. May 1999: no coma was detected at heliocentric distance r = 4.98 AU. From the measured brightness in the Bessell R-filter, a mean nucleus radius of $555\pm40$ m is derived (for a geometric albedo of 0.04 and a phase darkening of 0.04 mag/deg). The nucleus signal varies during the 2.7 h observing interval and a peak-to-peak amplitude of ~0.38 mag is determined. The measured lightcurve is in agreement with a rotation period of 6-7.5 hours and a ratio of the main nucleus axes of at least 1.4. The non-detection of a coma allows one to put an approximate upper limit for Af $\rho$ of <0.45 cm (suggesting a dust production rate of 0.05 kg/s). December 2001: a weak and condensed coma seems to be present in the seeing disk of the comet at 2.9 AU inbound, causing a higher brightness than expected from the previous size estimates of the nucleus. The colour of the comet appears very red ( V-R spectral gradient ~47%/100 nm). The Af $\rho$ value of the comet was $6.5\pm2$ cm (equivalent to a dust production rate of about 1 kg/s).


Key words: comets: individual: 46P/Wirtanen -- comets: general

Offprint request: H. Boehnhardt, hboehnha@eso.org




© ESO 2002

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.