Comet 29P/Schwassmann-Wachmann 1 in outburst

ATel #1879; Josep M. Trigo-Rodriguez(Institute of Space Sciences, CSIC-IEEC)
on 23 Dec 2008; 13:48 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Josep M. Trigo-Rodriguez (trigo@ieec.uab.es)

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A new outburst experienced by comet 29P/Schwassmann-Wachmann 1 is reported. After the last outburst experienced by this Centaur at the end of September [for more details see IAUC 8991 ] the comet was during October progressively decreasing up to 16.0 R magnitude. During November the comet remained quiescent around 15.8R magnitude 15.8 (15.7 I) as noticed on Nov. 24.156 by D.A. Garcia-Hernandez using the IAC80 telescope, Instituto de Astrofisica de Canarias. All magnitudes are given here for a 10 arcsec standardized aperture. A. Sanchez, MPC442-Gualba Observatory, observed continuously this comet from Nov.17 until Dec. 6 exhibiting an almost stationary 15.8R magn. This behavior changed in mid-December when A. Sanchez reported a progressive increase in its magnitude from Dec. 11.190 with 15.6R magnitude until Dec. 18.185 when the comet had reached 14.8R magnitude. Interestingly the comet kept this magnitude on Dec. 19.185 as reported by same observer. Notice that this behavior is consistent with grain lifetime sublimation calculations performed by Gunnarson (2003), A&A 398, 353 who found that the lifetime of mm-sized clusters producing the micron-sized particles should be of 2 or 3 days. As expected by these calculations, about three days later, on Dec. 20.990 A. Sanchez reported the final outburst reaching 12.6 R magnitude and an almost-stellar appearance. D. Rodríguez, MPC458-Guadarrama Observatory, confirmed the same magnitude on Dec. 21.970. These results are in the typical trend reported by Trigo-Rodriguez et al. [(2008) A&A485, pp. 599-606]. In such work the outburst frequency was established in 7.3 outbursts/year, typically reaching a +13 maximum magnitude or less. During the next days, we expect that the fine dust material released from the 29P nucleus develop a bright coma. Additionally a bright fan of material extending from the nucleus would also appear as is usually reported in bright outbursts of this comet. A future follow-up of this object can be very useful in order to understand the magnitude decay as a function of the grain spatial density and the progressive sublimation.