Outburst activity in comets - II. A multiband photometric monitoring of comet 29P/Schwassmann-Wachmann 1

Abstract

We have carried out a continuous multiband 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 have used a standardized method to obtain the 10‐arcsec nucleus photometry in the V, R and I filters of the Johnson–Kron–Cousins system, which are accurately calibrated with standard Landolt stars. The production of dust in the R and I bands during the 2010 February 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. The ulterior sublimation of these ice‐rich dust particles during the following days induces fragmentation, generating micrometre‐sized grains, which increase the dust spatial density to produce the outburst in the optical range as a result of the scattering of sunlight. The material leaving the nucleus adopts a fan‐like dust feature, formed by micrometre‐sized particles that decay in brightness as it evolves outwards. By analysing the photometric signal measured in a standardized 10‐arcsec aperture using the phase dispersion minimization technique, we have found a clear periodicity of 50 d. Remarkably, this value is also consistent with an outburst frequency of 7.4 outbursts per yr deduced from the number of outbursts noticed during the effective observing time.

CO Gas and Dust Outbursts from Centaur 29P/Schwassmann–Wachmann

“…Furthermore, some dust outbursts may overlap in time, which may be the case for the outburst A. Thus, as Trigo-Rodríguez et al (2010) points out, the ∼ 50 day average obtained from an observed 7 outbursts/year may not be physically tied to the actual rotation rate of the nucleus.…”

Analysis of HST WFPC2 Observations of Centaur 29P/Schwassmann–Wachmann 1 while in Outburst to Place Constraints on the Nucleus’ Rotation State

“…This continuous activity, often called its "quiescent" activity, is believed to be driven by sublimation of the supervolatile CO (Festou et al (2001); Gunnarsson et al (2002); Paganini et al (2013)) and/or from gases released during the crystallization of amorphous water ice (Jewitt (2009) ;Womack et al (2017)). (3) Additionally, it frequently, and consistently, undergoes major outbursts events in activity with estimated lower-limits for the total mass of material ejected on the order of 10 8 − 10 9 kg per outburst event (Trigo-Rodríguez et al (2010); Kossacki & Szutowicz (2013); Hosek et al (2013); Miles et al (2016); Schambeau et al (2017)). These outburst events are detected as corresponding increases in surface brightness of the coma's dust continuum features and range over several orders of magnitude, lasting from several days to a few weeks.…”

The outbursts of the comet 29P/Schwassmann‐Wachmann 1: A new approach to the old problem

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As far as outbursts activity is concerned, the 29P/Schwassmann-Wachmann 1 is the exceptional comet. This Centaur object shows quasi-regular flares with periodicities of 50 days (Trigo-Rodriguez et al 2010). In the introductory part of the presented paper the most well-known hypotheses which try to explain this cometary behaviour are reviewed.

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“…Therefore, 29P/SW1 is also a Centaur object as far as its orbit is concerned. Secondly, despite the relatively large distance from the Sun, the comet shows an unexpected outburst activity with a periodicity of, on the average, 50 days (Trigo-Rodriguez et al 2010).…”