Two apparent outbursts of comet 81P/Wild 2
ATel #15694; Michael S. P. Kelley (University of Maryland) on behalf of the Zwicky Transient Facility Collaboration
on 19 Oct 2022; 04:43 UT
Credential Certification: Kumar Venkataramani (kumarv@caltech.edu)
We report two apparent outbursts of comet 81P/Wild 2, identified in Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP 131, a8002) images of the comet. Photometry measured in 5 arcsec radius apertures (PS1 photometric system) show two discontinuities in the comet's apparent magnitude, followed by a decay back to a nominal brightening trend. The first discontinuity occurred between 2022 Oct 05.53 and Oct 07.52 UTC, from r=14.05+/-0.02 to 13.90+/-0.02 mag. However, uncalibrated images taken at 2022 Oct 06.53 have a morphology consistent with that on Oct 05, indicating the outburst occurred between Oct 06.53 and 07.52 UTC. The second discontinuity occurred between Oct 10.54 and Oct 14.53 UTC, from r=13.96+/-0.02 to 12.98+/-0.02 mag. Both events are confirmed by inspection of the comet's morphology processed with temporal filtering, and the second event is clearly visible in the direct images as a 180-deg wide sunward fan. Accounting for a nominal brightening trend of -0.018 mag/day, the apparent outbursts had strengths of -0.13+/-0.03 and -1.05+/-0.03 mag within our photometric apertures.
Based on observations obtained with the Samuel Oschin Telescope 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, Weizmann Institute for Science, Oskar Klein Center at Stockholm University, University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, TANGO Consortium of Taiwan, University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
