Forced precession models for six erratic comets
Space Research Centre, Polish Academy of Sciences, Bartycka 18A, 00-716 Warsaw, Poland
2 Institute of Theoretical Physics, University in Białystok, Lipowa 41, 15-424 Białystok, Poland
Corresponding author: M. Królikowska, firstname.lastname@example.org
Accepted: 6 December 2000
The nongravitational motion of six "erratic" short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 16P/Brooks 2, 21P/Giacobini-Zinner, 31P/Schwass mann-Wachmann 2, 32P/Comas Solá, 37P/Forbes and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force, and of maximum cometary activity with respect to perihelion time. The present precession models impose some constraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.29 (equatorial to polar radius of 1.41) is the most oblate among six investigated comets.
Key words: solar system / comets / individual / 16P/Brooks 2, 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes and 43P/Wolf-Harrington
© ESO, 2001