Comet 29P outbursts in 2015-2026 MPC photometry do not follow the 57.71-day period found in 2002-2014 outburst times

Miles (2016) reported that outbursts of centaur comet 29P/Schwassmann-Wachmann from 2002-2014 occur at fixed phases of a 57.71-day solar day of a slowly rotating nucleus. We made a new outburst catalogue from all magnitudes of 29P in the IAU Minor Planet Center observation archive (48,611 records from 492 stations, 2002 to August 2026). An onset is a brightening of 0.5 mag or more between consecutive nights of one station, with a matching jump at 2 or more stations. The catalogue has 43 onsets in 2002-2014 and 58 in 2015-2026; it recovers 9 of 12 published 2008-2010 outbursts and about half of all strong outbursts. Significance comes from simulations that move groups of close outbursts to random times when 2 or more stations could detect an onset. In 2002-2014 our onsets show part of the published signal (Rayleigh Z1 = 9.5 at 57.71 d, p = 0.014), but not in a free 40-80 d search (p = 0.46). In 2015-2026 there is no signal at 57.71 d (Z1 = 1.5, p = 0.55; four-harmonic p = 0.11). A phase forecast trained on 2002-2014 does worse than 95% of random phase shifts, and the best-fit fraction of test onsets that follow the training pattern is 0 (90% interval 0-0.15). Four other detector settings and periods of 57.65, 57.77 and 57.09 d give the same result. The 2015-2026 onsets have a peak at 58.46 d that we found after inspection (p = 0.015 in a 1-day window); 2002-2014 onsets show no power there, and the best period in 6-year windows moves between 54 and 59 d. The full 2002-2026 record has no significant period in 40-80 d (p = 0.39). Thus a single stable rotational clock near 57.7 d does not predict 29P outburst times in this catalogue. Limitations: heterogeneous amateur and professional magnitudes, about 55% completeness for strong outbursts, few close follow-up outbursts, and no test of the full source-longitude model. MPC records are not bundled; a retrieval script and hash are given.

29P/Schwassmann-Wachmann · comet outbursts · centaur · rotation period · periodicity test · out-of-sample forecast · Minor Planet Center · Rayleigh test · cryovolcanism