Outburst of Comet 29P/Schwassmann-Wachmann 1

ATel #12994; Quanzhi Ye (Caltech/IPAC), Michael S. P. Kelley (U. Maryland), Dennis Bodewits (Auburn U.) on behalf of the Zwicky Transient Facility Collaboration
on 7 Aug 2019; 08:21 UT
Credential Certification: Quanzhi Ye (qye@caltech.edu)

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Following the initial report by Richard Miles (British Astronomical Association) regarding an apparent outburst of comet 29P/Schwassmann-Wachmann 1 on UT 2019 Aug. 2.2 +- 0.4 (see https://groups.yahoo.com/neo/groups/comets-ml/conversations/messages/27906), here we report our measurement made using the images taken with the Zwicky Transient Facility (ZTF), operated on the 1.2-m Oschin Schmidt telescope at Palomar Observatory (Bellm et al. 2019, PASP, 131, a8002). Differencing two ZTF r-band images taken on UT 2019 Aug. 1.50 and 4.50 reveals a strong, asymmetric feature at the nucleus of the comet, suggestive of an outburst. Photometry below are measured using the ZChecker software (Kelley et al. 2019, Proc. of ADASS XXVIII, ASP Conf. Ser. 471, 305), using circular apertures with a projected radius of 20,000 km and calibrated to the Pan-STARRS photometry system. Colors are corrected assuming an empirical color correction of g-r=0.56, r-i=0.17. A i-mag of 14.50 +/- 0.02 was measured on Aug 2.44, which corresponds to r=14.67 when we apply this color correction. This implies that the event occurred between Aug 1.50 and Aug 2.44.

 
       Date UT             mag      dmag   band 
----------------------     -------     ------  ------  
2019 Aug. 1.50        16.38     0.03     r 
2019 Aug. 2.44        14.50     0.02     i 
2019 Aug. 4.50        14.99     0.02     r 
2019 Aug. 5.49        15.89     0.03     g 

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.