Small Apparent Outbursts of Comet 7P/Pons-Winnecke
ATel #14486; Michael S. P. Kelley (U. Maryland), Tim Lister (Las Cumbres Observatory), on behalf of the Zwicky Transient Facility Collaboration and LCO Outbursting Objects Key Project
on 26 Mar 2021; 19:15 UT
Credential Certification: Tim Lister (tlister@lco.global)
We report two apparent outbursts of comet 7P/Pons-Winnecke discovered in Zwicky Transient Facility (ZTF) data (Bellm et al. 2019, PASP, 131, a8002). Photometry measured in 5" radius apertures from ZTF and Las Cumbres Observatory (LCO) are listed in the table below. All data are in the PS1 magnitude system and color corrected using our estimated colors of the comet: g-r=0.53±0.07 mag, and r-i=0.30±0.11 mag. Data taken 2021 Jan 3 to 19 UTC are consistent with a bare nucleus of radius 2.20±0.07 km, assuming a 4% geometric r-band albedo and 0.035 mag/deg phase correction (cf. Snodgrass et al. 2005, A&A, 444, 287; Fernandez et al. 2013, Icarus 226, 1138). We fit the remainder of the data, taken 2021 Feb 03 to Mar 25 UTC, with a combination of the aforementioned model nucleus and a linear change in magnitude from a coma with best-fit slope -0.0746±0.0006 mag/day. Two significant r-band outliers are found: -0.38±0.12 at 2021 Feb 03.446 UTC, and -0.23±0.02 mag at 2021 Mar 19.465 UTC, as compared to the best-fit trend. We presume these to be small outbursts at the comet. The latter outburst is confirmed in LCO 1-m telescope photometry, taken as part of the LCO Outbursting Objects Key (LOOK) Project.
Observations of comet 7P are encouraged this perihelion passage in case of larger outbursts. Perihelion is on 2021 May 27 UTC (MPEC 2015-E14) and the comet will be a southern hemisphere target in the second half of 2021.
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, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
Date (UTC) Tel Filt m m unc r - Trend
-------------- --- ---- ----- ----- ---------
2021-01-03.484 ZTF r 19.60 0.21 -0.13
2021-01-03.515 ZTF i 19.15 0.20 -0.29
2021-01-03.516 ZTF i 19.25 0.22 -0.19
2021-01-05.488 ZTF r 19.72 0.21 0.03
2021-01-09.520 ZTF r 19.54 0.13 -0.06
2021-01-09.526 ZTF g 20.04 0.17 -0.09
2021-01-10.535 ZTF g 20.18 0.19 0.08
2021-01-12.504 ZTF r 19.39 0.11 -0.13
2021-01-12.528 ZTF g 20.08 0.17 0.03
2021-01-14.505 ZTF g 20.00 0.16 -0.01
2021-01-15.526 ZTF r 19.87 0.17 0.42
2021-01-15.527 ZTF r 19.64 0.14 0.19
2021-01-15.548 ZTF g 20.10 0.18 0.13
2021-01-16.482 ZTF g 19.86 0.15 -0.09
2021-01-16.505 ZTF i 19.37 0.16 0.24
2021-01-16.539 ZTF r 19.52 0.11 0.10
2021-01-17.540 ZTF r 19.44 0.10 0.04
2021-01-17.549 ZTF g 20.08 0.17 0.15
2021-01-18.541 ZTF g 20.09 0.16 0.19
2021-02-03.446 ZTF r 18.56 0.12 -0.38
2021-02-03.504 ZTF g 19.15 0.14 -0.31
2021-02-05.427 ZTF r 18.98 0.10 0.10
2021-02-05.507 ZTF i 18.62 0.08 0.04
2021-02-07.516 ZTF r 18.80 0.06 -0.01
2021-02-07.526 ZTF g 19.36 0.09 0.02
2021-02-08.477 ZTF i 18.50 0.09 0.01
2021-02-08.479 ZTF i 18.44 0.08 -0.06
2021-03-09.507 ZTF r 17.67 0.03 -0.05
2021-03-17.390 ZTF r 17.32 0.03 -0.05
2021-03-19.448 ZTF g 17.48 0.03 -0.31
2021-03-19.465 ZTF r 17.03 0.02 -0.23
2021-03-20.473 LCO r 17.05 0.02 -0.16
2021-03-22.485 ZTF r 17.11 0.03 -0.00
2021-03-22.503 ZTF r 17.09 0.02 -0.03
2021-03-23.064 LCO r 17.10 0.02 0.02
2021-03-23.381 ZTF r 17.13 0.05 0.06
2021-03-25.400 ZTF r 17.01 0.04 0.05
