Outburst activity in comets: II. A multi-band photometric monitoring of comet 29p/Schwassmann-Wachmann 1

TL;DR

This study monitored comet 29P/Schwassmann-Wachmann 1 over two years, revealing that large particle ejections trigger outbursts, which are followed by sublimation and fragmentation, with a periodicity of about 50 days.

Contribution

It provides detailed multi-band photometric evidence linking large particle ejection to outburst mechanisms and identifies a consistent 50-day periodicity in activity.

Findings

Massive ejection of large particles triggers outbursts.

Sublimation and fragmentation increase dust density during outbursts.

Outburst frequency is approximately 7.4 per year.

Abstract

We have carried out a continuous multi-band photometric monitoring of the nuclear activity of comet 29P/Schwassmann-Wachmann 1 from 2008 to 2010. Our main aim has been to study the outburst mechanism on the basis of a follow-up of the photometric variations associated with the release of dust. We used a standardized method to obtain the 10 arc-sec nucleus photometry in the V, R, and I filters of the Johnson-Kron-Cousins system, being accurately calibrated with standard Landolt stars. Production of dust in the R and I bands during the 2010 Feb. 3 outburst has been also computed. We conclude that the massive ejection of large (optically-thin) particles from the surface at the time of the outburst is the triggering mechanism to produce the outburst. Ulterior sublimation of these ice-rich dust particles during the following days induces fragmentation, generating micrometer-sized grains that increase the dust spatial density to produce the outburst in the optical range due to scattering of sun light. The material leaving the nucleus adopts a fan-like dust feature, formed by micrometer-sized particles that are decaying in brightness as it evolved outwards. By analyzing the photometric signal measured in a standardized 10-arcsec aperture using the Phase Dispersion Minimization technique we have found a clear periodicity of 50 days. Remarkably, this value is also consistent with an outburst frequency of 7.4 outbursts/year deduced from the number of outbursts noticed during the effective observing time.