Outburst of Comet 29P/Schwassmann-Wachmann 1
ATel #12871; Quanzhi Ye (Caltech/IPAC), Michael S. P. Kelley (U. Maryland), Dennis Bodewits (Auburn U.) d on behalf of the Zwicky Transient Facility Collaboration, Richard Miles (British Astronomical Association), John Drummond (Possum Observatory)
on 17 Jun 2019; 17:39 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Quanzhi Ye (qye@caltech.edu)
We report an apparent outburst of comet 29P/Schwassmann-Wachmann 1, independently discovered by Ye, Kelley and Bodewits in images taken with the Zwicky Transient Facility (ZTF) operated on the 1.2-m Oschin Schmidt telescope at Palomar Observatory (c.f. ATel 11266), and by Miles in images taken with the Las Cumbres Observatory (LCO) network. Differencing two ZTF g-band images taken on UT 2019 Jun. 9.46 and 12.45 shows a moderately strong point source component at the nucleus of the comet, suggestive of an outburst. ZTF photometry on the two images confirms a sudden increase in brightness, from g = 17.4 to 16.5 mag, measured using circular apertures with a projected radius of 20,000 km and calibrated to the Pan-STARRS photometry system. The comet was 5.77 au from the Sun and 6.16 to 6.12 au from the Earth on Jun. 9 and 12, respectively.
After Kelley posted the ZTF findings on the comets-ml mailing list, Miles communicated that himself and Drummond had independently detected the same outburst (see https://groups.yahoo.com/neo/groups/comets-ml/conversations/messages/27812). Images taken by Drummond at Possum Observatory, Patutahi, New Zealand (IAU Observatory Code E94) using a 0.41-m f/4.5 Newtonian + CCD found the object was quiescent on UT 2019 Jun. 10.75. An image scheduled by Miles on the Las Cumbres Observatory (LCO) network taken with a 1.0-m f/8.0 Ritchey-Chretien + CCD at Sutherland, South Africa (IAU Observatory Code K91) on UT 2019 Jun. 11.19 showed the inner coma had brightened by 1.0 +/-0.1 magnitude as measured in the Cousins R passband, characteristic of a sudden outburst between UT 2019 Jun. 10.97 +/- 0.18 (uncertainty derived using the definition in Miles 2016, Icarus, 272, 387, Sect 3.4).
Part of this work makes use of observations obtained with the Samuel Oschin Telescope 48-inch at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW.
