Apparent Outburst of Comet P/2014 W1 (PanSTARRS)
ATel #16220; Michael S. P. Kelley (Univ. Maryland), Tim Lister (Las Cumbres Observatory), Quanzhi Ye (Univ. Maryland) on behalf of the Zwicky Transient Facility Collaboration and the LCO Outbursting Objects Key Project
on 31 Aug 2023; 03:35 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Kumar Venkataramani (kumarv@caltech.edu)
We report an apparent outburst of comet P/2014 W1 (PanSTARRS),
identified in Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP
131, a8002) images. In data taken with ZTF on 2023 Aug 13.42 and Aug
18.38 UTC, the comet's brightness was r = 20.24 ± 0.20 and 20.28
± 0.21 mag, respectively. On 2023 Aug 29.34 UTC, the comet
brightness was measured to be r = 18.49 ± 0.08 mag. The
brightening was confirmed with data from a 1-m Las Cumbres Observatory
telescope at McDonald Observatory on 2023 Aug 30.38 UTC with r = 18.81
± 0.04 mag. All reported measurements are in the PS1 photometric
system, using 5" radius apertures. In addition to the brightening,
the comet's morphology changed from a faint compact source (coma
radius <5" in 2" seeing) to one displaying a tail (length = 14" or
21,000 km). The data show that the comet brightened by at least -1.8
± 0.2 mag between Aug 18 and 29, although ~0.2 mag of that estimate
could be attributable to geometric circumstances and changing ambient
activity as the comet approached the Sun and Earth (the heliocentric
distance decreased from 2.84 to 2.82 au, the geocentric distance from
2.22 to 2.09 au, and the phase angle from 18.3 to 16.5 deg).
Observations by Pan-STARRS and ATLAS reported to the Minor Planet
Center show that the outburst likely occurred between 2023 Aug 22.5 UT
and Aug 25.5 UT, as the brightness of the comet increased from G=20.5
mag to c=17.7 mag (aperture radii unavailable; MPEC 2023-Q150). This
is grossly consistent with the length of the tail observed by ZTF,
which suggests the outburst happened around 2023 Aug 25 based on the
Whipple (1950) model for dust speeds.
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.
This work makes use of observations from the Las Cumbres
Observatory global telescope network.
