Small Apparent Outburst of Comet 123P/West-Hartley
ATel #12380; Michael S. P. Kelley (U. Maryland), Tim Lister (Las Cumbres Observatory), Dennis Bodewits (Auburn), on behalf of the Zwicky Transient Facility Collaboration and the Cometary Outburst Follow-Up Team
on 11 Jan 2019; 17:23 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Michael Kelley (msk@astro.umd.edu)
Subjects: Optical, Comet, Solar System Object, Transient
We report a small apparent outburst of comet 123P/West-Hartley, discovered in the course of our Zwicky Transient Facility (ZTF) survey of comets. Comet 123P had been steadily brightening at a rate of about -0.05 mag/day since the end of November 2018. ZTF photometry shows a sudden increase in brightness, from r = 14.6 to 14.2 mag over a 24-hr period between 2019 Jan. 09 and 10 UTC. We observed the comet with a Las Cumbres Observatory 0.4-m telescope at Tenerife, and confirmed the apparent outburst. Photometry is tabulated below, calibrated to the PanSTARRS photometry system. The comet brightness was measured using circular apertures with a projected radius of 10,000 km. An examination of the ZTF images shows the increased brightness has a point-source like morphology, consistent with a sudden increase in cometary activity. Follow-up photometry and imaging is encouraged to determine if this small change is a persistent increase in brightness or a short-lived event.
This work makes use of observations from the LCOGT network operated by Las Cumbres Observatory. It is also based on observations obtained with the Samuel Oschin Telescope 48-inch at the Palomar Observatory as part of the Zwicky Transient Facility project. Major funding has been provided by the U.S National Science Foundation under Grant No. AST-1440341 and by the ZTF partner institutions: the California Institute of Technology, the Oskar Klein Centre, the Weizmann Institute of Science, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron, the University of Wisconsin-Milwaukee, and the TANGO Program of the University System of Taiwan.
Date Telescope rh Delta phase rho r unc
UTC (MPC site code) AU AU deg arcsec mag mag
--------------- --------------- ----- ----- ----- ------ ----- ----
2018-11-04.5504 ZTF (I41) 2.247 2.182 25.8 6.3 16.91
2018-11-26.4702 ZTF (I41) 2.198 1.905 26.6 7.2 16.40
2018-12-03.5462 ZTF (I41) 2.185 1.820 26.6 7.6 15.99
2018-12-16.5170 ZTF (I41) 2.164 1.671 25.9 8.3 15.83
2018-12-29.4618 ZTF (I41) 2.148 1.536 24.5 9.0 15.30
2019-01-09.4518 ZTF (I41) 2.137 1.433 22.6 9.6 14.62
2019-01-10.4442 ZTF (I41) 2.137 1.425 22.4 9.7 14.23
2019-01-11.0645 TFN 0.4m (Z21) 2.136 1.419 22.3 9.7 14.17 0.02
