Long-term monitoring of comet 29P/Schwassmann–Wachmann from the Lulin Observatory

Abstract Multi-band photometric monitoring of comet 29P/Schwassmann–Wachmann 1 was conducted with the standard Johnson–Cousins filter set. Observations extended from 2018 July to 2021 December. The comet was detected to show at least 12 relatively large outbursts, during which its brightness increased by 1.5 to 5 mag as measured through a 5″ aperture. The outbursts resulted in a clear variation of the cometary brightness profile. The derived slopes of the surface brightness profiles showed a significant variation with time from a shallower slope to a steeper one at the beginning of each outburst and then slowly returning to pre-outburst values. There did not seem to be any obvious change in the color indices as the outbursts occurred. However, for the quadruple outbursts in late September of 2021, we could confidently spot a change in the color of the comet, indicating that the color indices seem to be less than the mean values, especially in the B − V term. Dust production derived by using the dust production rate parameter, Afρ, from the R-band photometry measurements shows the outburst to be accompanied by a large increasing trend. Using a simple model and the derived outflow velocity of 0.11 km s−1 from the expanding shell features, an estimated lower limit of 1.0 × 108 kg up to 2.7 × 109 kg of dust was released during the quadruple outbursts by using a specific dust size of 1 μm.