Small outburst of comet 260P/McNaught
ATel #13174; Michael S. P. Kelley (U. Maryland), Dennis Bodewits (Auburn U.), Quanzhi Ye (U. Maryland) on behalf of the Zwicky Transient Facility Collaboration
on 8 Oct 2019; 19:38 UT
Credential Certification: Michael Kelley (msk@astro.umd.edu)
We report the discovery of a small apparent outburst of comet 260P/McNaught, observed as part of the Zwicky Transient Facility survey (Bellm et al. 2019, PASP, 131, a8002). Photometry of the comet in images since 2019 Sep 24 UTC, measured with 5" radius apertures and calibrated to the PS1 catalog (Tonry et al. 2012, ApJ, 750, 99), is tabulated below. We estimate the coma color to be g-r=0.61±0.02 mag. The apparent magnitude has remained nearly constant over this time period with the given aperture size, varying -0.002 mag/day (RMS <0.01 mag). However, between 2019 Oct 04.48 and 05.35 UTC, the comet brightened from r=13.78±0.02 to 13.59±0.02 mag, and remained bright in the next four images taken through Oct 08.43 UTC. The data suggest a small outburst with a strength of at least -0.19±0.02 mag with respect to the best-fit trend. Further observations of this moderately bright comet are encouraged, in case this is followed by a larger event.
Date rh Delta Phase Filter m unc r Trend Residuals
(UTC) (au) (au) (deg) (mag) (mag) (mag) (mag) (mag)
------------- ----- ----- ----- ------ ----- ----- ----- ----- ---------
2019-09-24.41 1.426 0.568 33.6 g 14.41 0.03 13.80 13.80 -0.01
2019-09-24.42 1.426 0.568 33.6 g 14.41 0.03 13.80 13.80 -0.01
2019-09-24.50 1.426 0.568 33.5 r 13.81 0.02 13.81 13.80 0.01
2019-09-30.41 1.435 0.563 31.8 g 14.40 0.02 13.79 13.79 -0.00
2019-10-02.41 1.439 0.562 31.2 g 14.40 0.02 13.79 13.79 0.00
2019-10-03.37 1.441 0.562 30.9 r 13.79 0.02 13.79 13.78 0.01
2019-10-03.42 1.441 0.562 30.8 g 14.39 0.02 13.78 13.78 -0.00
2019-10-04.48 1.443 0.562 30.5 g 14.39 0.02 13.78 13.78 -0.00
2019-10-05.35 1.445 0.562 30.2 r 13.59 0.02 13.59 13.78 -0.19
2019-10-07.37 1.450 0.563 29.6 r 13.65 0.02 13.65 13.77 -0.12
2019-10-07.40 1.450 0.563 29.6 g 14.28 0.02 13.67 13.77 -0.11
2019-10-08.33 1.452 0.563 29.3 g 14.28 0.02 13.67 13.77 -0.10
2019-10-08.43 1.452 0.563 29.2 r 13.67 0.02 13.67 13.77 -0.10
Columns - rh, heliocentric distance; Delta, observer-comet distance; Phase, Sun-comet-observer angle; Filter, ZTF bandpass name; m, apparent magnitude through filter in 5" radius aperture; unc, uncertainty on m; r, effective r-band lightcurve after transforming g- into r-band photometry; Trend, the best-fit linear trend; and Residuals, the residuals from the fit.
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.
