Physical properties and mini-outburst of 64P/Swift-Gehrels

Abstract

Aims. We present secular multiwavelength broadband photometry, spanning over 93 days, performed at the Yaoan High Precision Telescope on comet 64P/Swift-Gehrels in its 2018–2019 apparition. Our aim is to study its dust activity, coma properties, and the accidentally discovered mini-outburst. Methods. We used aperture photometry to measure the Afρ value and correct the back-scattering effect based on phase angle. We deployed azimuthally averaged image enhancement methods to identify the coma morphology and the outburst. Secular color measurement was also conducted on the comet. Results. We identified a −0.5 mag mini-outburst around January 3, 2019, with coma morphology study showing an obvious dust jet feature strengthened during the outburst. The maximum A(0)fρ value of 64P/Swift-Gehrels recorded is 313 cm at the top of the fitted curve and 334 cm at the outburst event. Both volatile-driven pressure mechanisms and nonvolatile-driven mechanisms could be the major explanation for the outburst. We obtain a mean color B − V = 0.68 ± 0.03 and V − R = 0.08 ± 0.01. The B − V color is similar to the mean value for Jupiter Family comets, but the V − R color turns out to be bluest among all the recorded short-period comets. The cause of this anomaly remains unknown.