Overdue Return of Comet 168P/Hergenrother
ATel #12955; Quanzhi Ye (Caltech/IPAC), Michael S. P. Kelley (U. Maryland), Dennis Bodewits (Auburn U.) on behalf of the Zwicky Transient Facility Collaboration
on 24 Jul 2019; 15:07 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Quanzhi Ye (qye@caltech.edu)
We report the overdue return of comet 168P/Hergenrother. The comet should have brightened to V=14 (assuming that it follows the brightening rate of the last return in 2012, cf. http://aerith.net/comet/catalog/0168P/index.html ) to V=17 (assuming the brightening rate of the other observed returns) at the time of the writing. The Zwicky Transient Facility (ZTF) survey, operated on the 1.2-m Oschin Schmidt telescope at Palomar Observatory (Bellm et al. 2019, PASP, 131, a8002), has obtained a total of 17 images of the position of the comet between UT 2019 Jul. 3 and 21, reaching m_AB~20 to 20.5. JPL orbit solution 54 indicates a 3-sigma positional uncertainty of about 1”; the Minor Planet Center orbit is about 20 arcmin northeast of the JPL position throughout this time. Both positions plus the uncertainty ellipses are well within most ZTF images, but the comet cannot be seen, suggesting that its brightness is at least 3 magnitudes below the most conservative prediction.
168P/Hergenrother had three outbursts and generated several fragments during its previous return in 2012 (Sekanina 2014, arXiv 1409.7691). These events may have signaled a major change in the comet's activity state, or even its demise. Further observation is encouraged as the comet is approaching its perihelion passage on UT 2019 Aug. 5.
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.
