Electronic Telegram No. 5403 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 P/2024 K1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".3 seeing show a condensed coma of size 1".6 (full-width-at-half-maximum) but no tail. 2024 UT R.A. (2000) Decl. Mag. May 30.41847 16 20 39.04 -21 39 36.3 20.7 30.42560 16 20 38.78 -21 39 35.3 21.0 30.43272 16 20 38.55 -21 39 34.4 21.1 30.44033 16 20 38.27 -21 39 33.7 21.3 Weryk reports that six 60-s gri-band poor-quality follow-up images were obtained on May 31.5 UT with the 3.6-m Canada-France-Hawaii Telescope (aided by R. Wainscoat, L. Wells, and T. Burdullis) show a slightly larger image (1".8 FWHM) for the comet compared to stars. Three additional 90-s CFHT images were taken on June 1.4 that show this object to be definitely a comet; the best image in 1".0 seeing shows a very condensed head of size 1".4 (FWHM) with evidence of a broad-but-short tail 1" long spanning p.a. 240-340 deg. After the comet was posted on the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that twelve stacked 120-s CCD exposures taken remotely on June 6.6 UT with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, show a moderately condensed coma 8" in diameter with no tail; the magnitude was 19.8 as measured within a circular aperture of radius 4".3. The available astrometry appears on MPEC 2024-L114. The following preliminary orbital elements by S. Nakano (Central Bureau) are from 28 observations spanning May 30-June 10 (mean residual 0".2). A parabolic orbit shows a mean error of 1".0. There appear to be no observations in archival data, and there appear to be no close approaches to any major planets. T = 2024 May 9.99582 TT Peri. = 352.11737 e = 0.4956511 Node = 251.69581 2000.0 q = 3.4539059 AU Incl. = 1.78348 a = 6.8482478 AU n = 0.05499648 P = 17.92 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 05 10 16 31.41 -22 13.4 2.488 3.454 159.9 5.8 19.8 2024 05 20 16 26.40 -21 57.9 2.452 3.455 170.8 2.7 19.8 2024 05 30 16 20.88 -21 40.3 2.443 3.456 178.3 0.5 19.7 2024 06 09 16 15.48 -21 22.2 2.461 3.459 167.5 3.7 19.8 2024 06 19 16 10.82 -21 05.4 2.507 3.464 156.8 6.6 19.8 2024 06 29 16 07.42 -20 51.6 2.576 3.469 146.4 9.3 19.9 2024 07 09 16 05.61 -20 42.2 2.668 3.476 136.4 11.6 20.0 2024 07 19 16 05.61 -20 38.1 2.778 3.484 126.9 13.5 20.1 2024 07 29 16 07.45 -20 39.4 2.902 3.493 117.8 14.9 20.2 2024 08 08 16 11.08 -20 45.6 3.038 3.503 109.1 15.9 20.3 2024 08 18 16 16.42 -20 56.2 3.183 3.514 100.7 16.4 20.4 2024 08 28 16 23.30 -21 10.0 3.332 3.527 92.7 16.6 20.5 2024 09 07 16 31.58 -21 26.0 3.484 3.541 85.0 16.5 20.6 2024 09 17 16 41.09 -21 42.8 3.635 3.555 77.5 16.0 20.7 2024 09 27 16 51.69 -21 59.5 3.784 3.571 70.2 15.3 20.8 2024 10 07 17 03.23 -22 15.0 3.929 3.588 63.0 14.4 20.9 2024 10 17 17 15.56 -22 28.2 4.067 3.606 56.0 13.2 21.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 June 11 (CBET 5403) Daniel W. E. Green