Electronic Telegram No. 5549 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network COMET C/2012 KA_51 An apparently asteroidal object found on CCD images taken with the 1.2-m f/2.4 Schmidt telescope at Palomar in May 2012 (during the final year of the "Palomar Transient Factory" survey (Law et al. 2009, PASP 121, 1395; Rau et al. 2009, PASP 121, 1334), with measurers listed as A. Waszczak (California Institute of Technology) and E. O. Ofek (Weizmann Institute of Science), was given the minor-planet designation 2012 KA_51 when published on MPS 434214; discovery observations tabulated below. On 2012 Oct. 11, Waszczak and Ofek reported that they found this object to show cometary appearance: the head showed a size of 6".0 (full-width-at-half-maximum) in 2".5 seeing, with no tail in 60-s exposures at 1".0/pixel resolution. 2012 UT R.A. (2000) Decl. Mag. May 22.16464 9 44 22.26 +69 38 22.5 19.0 22.27594 9 44 26.50 +69 36 38.3 18.9 22.30570 9 44 27.62 +69 36 10.2 19.2 23.21066 9 45 03.64 +69 22 08.3 18.4 23.27434 9 45 06.11 +69 21 08.9 19.1 23.30875 9 45 07.52 +69 20 36.8 18.9 24.21633 9 45 44.20 +69 06 34.6 19.1 24.26893 9 45 46.36 +69 05 45.4 19.0 24.29896 9 45 47.53 +69 05 17.3 18.7 28.19636 9 48 32.42 +68 05 23.1 18.8 28.27683 9 48 35.88 +68 04 08.4 18.9 28.31033 9 48 37.31 +68 03 37.5 18.8 No further cometary appearance was reported at that time. Eight years later, S. Deen (Simi Valley, CA, USA) found this object in numerous other CCD images that were obtained also in 2012 with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala, Hawaii. Deen has noted cometary appearance in both the archival Palomar and archival Pan-STARRS1 images. In all of the Pan- STARRS1 images (astrometry tabulated below), Deen finds that the comet appears definitely significantly fuzzier than all surrounding stars of the same brightness. On 2012 Mar. 11, z-band images show a weakly condensed coma with size 2".5 (full-width-at-half-maximum) with a somewhat-broad tail 5" long in p.a. about 140 degrees, in 1".3 seeing. On 2012 Mar. 13, i-band images show a weakly condensed coma of size 2".0 (FWHM) with a broad tail 5" long in p.a. 165 degrees, in 1".7 seeing. On 2012 Apr. 1, y-band images show only a marginal detection. On 2012 Dec. 28, r-band images show a very small, moderately condensed coma of size 1".25 (FWHM) and a thin tail 4" in p.a. 330 degrees, in 0".8 seeing. 2012 UT R.A. (2000) Decl. Mag. Mar. 11.58919 13 09 03.81 +85 54 47.3 19.3 11.59651 13 08 57.29 +85 54 46.4 19.4 13.45387 12 44 26.69 +85 51 14.0 19.0 13.46168 12 44 20.39 +85 51 12.4 19.2 Apr. 1.31590 10 10 25.67 +82 50 02.7 1.32353 10 10 24.15 +82 49 55.8 Dec. 28.63974 12 04 43.53 +42 13 02.2 21.5 28.65094 12 04 43.38 +42 13 04.0 21.6 The available astrometry appears on MPEC 2025-H88. The following orbital elements by S. Nakano (Central Bureau) are from 22 observations spanning 2012 Mar. 11-Dec. 28 (mean residual 0".2). The corresponding "original" and "future" values of 1/a are +0.001725 and +0.002036 (+/- 0.000005) AU**-1, respectively. The comet passed 3.82 AU from Jupiter on 2010 Mar. 24 UT and 6.72 AU from Uranus on 2005 July 18. Epoch = 2011 Nov. 15.0 TT T = 2011 Nov. 1.55565 TT Peri. = 94.16622 e = 0.9939802 Node = 344.84653 2000.0 q = 4.8952696 AU Incl. = 70.70697 Photometric power-law parameters H = 9.5 and 2.5n = 8 represent the comet's brightness reasonably well. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 April 30 (CBET 5549) Daniel W. E. Green