73P/Schwassmann-Wachmann 3

Boehnhardt, H. et al.    A&A 341, 912-917, 1999
"The nuclei of comets 26P/Grigg-Skjellerup and 73P/Schwassmann-Wachmann 3"

CCD V and R images were obtained at large heliocentric distances to try to derive size, rotation, etc.

• SW3 observations 27--31 December 1994 (before split)
• R=3.03, delta=2.34, phase angle=15d egrees
• Images showed small coma (~12,000km) and tail in anti-solar direction so comet not totally inactive. Derived an UPPER LIMIT for the radius of 1.1km and a solar V-R color. Determined only 4% of surface active.
• R(1,1,0)=16.85; V(1,1,0)=17.33
• [R(1,1,0) is R mag at helio=1au, geo=1au, phase=0]

¤¤¤¤¤

• Used the DIRBE data and detected 4 comets, including SW3.
• Observations 22April -- 26 May, 1990
• SW3 was the faintest (by far) comet observed.
• Uniformly bright over a large number of days so no lightcurve info.
• V=10.5--9.
• Derived T=307±120 (black body would be 282)
• Unresolved point source
• R=1.07; Q_dust=120 (kg/sec); Q_gas<3e28 (mol/sec); dust/gas > 0.12; M_tail=1e10 (kg)
• Also: did not detect Encke despite it being comparable magnitude.

¤¤¤¤¤

Radio observations (Nancay) of SW3 just PRIOR to the proposed splitting date. Observations were 30 August -- 18 September and 15 October -- 1 November 1995 (splitting 24 October and 1 December according to Sekanina). 20x increase in OH production but the OH and visual production evolutions are different -- the OH increase seems to be much steeper than the visual brightness increase and the OH brightness peak occurs one month earlier than for the visual brightness. The start of the OH outburst is ~45 days PRIOR to the split. There was not a single outburst but sustained activity.

The active area derived during the outburst was 30 km² which is incompatible with the small nucleus size above or the 2km derived by Sekanina.

OH production rates are given in Table 1 and range from < 2.8e28 to 22.2e28 mol/sec.
 

¤¤¤¤¤

Fink, U. and Hicks, M. D.    ApJ 459, 729-743, 1996
"A Survey of 39 Comets Using CCD Spectroscopy"

• Based on spectra from 0.55 to 1.0 microns (so O (¹D) for H₂O).
• Observed SW3 on 28 Feb 1990 with R=1.44 Delta=0.75
• Details of fluxes given
• Haser model production rates
• Q(H₂O) = ~4.2e27 (at 1au this is Q(H₂O)=~1.0e28)
• Q(C₂) = <0.3e25
• Q(NH₂) = <0.08e25
• Q(CN) = ~1.3e25
• --> Q(H₂O)/Q(CN) = 323

Last modified 25 June 1999

Additional references or comments: anita@barolo.as.utexas.edu