[BAA Comets] Comet 29P/S-W1 Observing Season + New outburst today

[Richard Miles]

Dear Observers,

As promised here is a first note on the subject of the 29P Observing 
Campaign for 2018/2019.

The first observation this apparition was by Jean-François Soulier (+ A. 
Maury, J.-B. de Vanssay) on 2018 04 03.388 using a remote telescope (W96, 
Chile) when the comet nucleus was magnitude 15.8r.
At that time the comet was at a solar elongation of 32.7 degrees.

The comet continues to move northwards and is now close to the celestial 
equator and so will be readily accessible to both northern and southern 
hemisphere observers. Its current elongation is 50 degrees visible in the 
morning sky and is within 0.02 AU of its perihelion of 5.7668 AU which is 
reached in March of next year given the shape of its rather circular orbit.

We have now begun intensive observations and the FIRST OUTBURST of this 
apparition was detected in a Las Cumbres Observatory images taken less than 
2 hours ago on 2018 04  24.793. This outburst appears to have an amplitude 
of 1.3 mag (measured in a 5.6" radius aperture) - see stacked image below.

Here is the most recent astrometry/.photometry:

0029P      C2018 04 22.42094 22 56 09.02 -03 00 10.2         16.36N      W89
0029P      C2018 04 22.42240 22 56 09.07 -03 00 09.2         16.27N      W89
0029P      C2018 04 22.42386 22 56 09.14 -03 00 08.8         16.26N      W89

0029P      C2018 04 22.79262 22 56 22.39 -02 58 23.7         16.39N      Q59
0029P      C2018 04 22.79418 22 56 22.44 -02 58 23.2         16.19N      Q59
0029P      C2018 04 22.79570 22 56 22.50 -02 58 24.0         16.32N      Q59

0029P      C2018 04 23.38800 22 56 43.61 -02 55 34.3         16.66N      W96
0029P      C2018 04 23.39919 22 56 44.06 -02 55 30.6         16.55N      W96
0029P      C2018 04 23.41117 22 56 44.45 -02 55 27.3         16.45N      W96

0029P      C2018 04 23.79307 22 56 58.03 -02 53 38.6         16.48N      Q58
0029P      C2018 04 23.79458 22 56 58.07 -02 53 38.2         16.55N      Q58
0029P      C2018 04 23.79610 22 56 58.13 -02 53 37.7         16.45N      Q58

0029P      C2018 04 24.79295 22 57 33.31 -02 48 55.1         15.19N      Q58
0029P      C2018 04 24.79450 22 57 33.35 -02 48 54.8         15.22N      Q58
0029P      C2018 04 24.79601 22 57 33.41 -02 48 54.3         15.20N      Q58

The present outburst occurred on 2018 04 24.29 +/-0.40, which corresponds to 
a rotational phase of the nucleus of 0.033 (adopting a 57.710 synodic 
rotation period).
Interestingly, outbursts last September and November have originated from 
virtually the same longitude on its nucleus: specifically at 0.011 phase on 
Sep 04.17 +/-0.18; and at 0.029 phase on Nov 01.97 +/-0.19. The gaps between 
these three outbursts correspond with exactly 1 and 3 rotations of the 
nucleus. All of the 9 outbursts since 2017 September have been relatively 
weak, the brightest attaining just mag 15.1r.

With this object, there is a high chance of a 'follow-up' outburst occurring 
within less than 10 days of the present one, and so observers are encouraged 
to keep a close watch on this most bizarre of comets.

Richard Miles
BAA
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