Volume 376, Number 2, September II 2001
|Page(s)||672 - 685|
|Section||Celestial mechanics and astrometry|
|Published online||15 September 2001|
Detailed phase function of comet 28P/Neujmin 1 *
European Southern Observatory, Casilla 19001, Santiago, Chile
2 Institut d'Astrophysique de Marseille, Traverse du Siphon, 13376 Marseille Cedex 12, France
3 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
4 Osservatorio Astronomico di Torino, Strada Osservatorio 20, 100025 Pino Torinese (TO), Italy
Corresponding author: C. Delahodde, firstname.lastname@example.org
Accepted: 10 July 2001
In 2000, comet 28P/Neujmin 1 was an ideal candidate for a phase function study: during its April opposition it reached a phase angle of α = 0.8°, and previous observations at similar heliocentric distances ( AU) indicated that the comet was likely to be inactive. We observed this comet using ESO's NTT and 2.2m telescopes at La Silla, on 6 epochs from April to August 2000, covering α = 0.8-8°. These data were combined with a large set of data from 1985 to 1997. In order to disentangle the rotation effects from the phase effects, we obtained complete rotation coverage at opposition, providing us with a lightcurve template. We have obtained an improved rotation period of hrs, with a full amplitude of mag, which yields an axis ratio lower limit of 1.51 ± 0.07. For each subsequent epochs, we have obtained enough rotation coverage to re-synchronize the lightcurve fragments with the template, and determine the magnitude change caused by the phase function. The average colours of the nucleus, , and , are similar with those of D-type asteroids and other comet nuclei. The phase function obtained for the nucleus has a linear slope of mag deg-1, less steep than that of the mean C-type asteroids.
Key words: comets: general / comets: individual: P/Neujmin 1 / techniques: photometric
© ESO, 2001
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