Electronic Telegram No. 5496 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/2025 A4 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Jan. 3 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). 2025 UT R.A. (2000) Decl. Mag. Jan. 3.62917 13 33 37.48 +25 58 18.9 21.0 3.64455 13 33 38.24 +25 58 20.4 21.6 3.65227 13 33 38.56 +25 58 21.5 20.9 Weryk and R. Wainscoat obtained three 40-s gri-band follow-up images on Jan. 4.64 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer L. Wells; queue coordinator H. Flewelling) in 0".9 seeing that show a condensed head of size 1".5 (full-width-at-half-maximum) with a broad 2"-long tail spanning p.a. 250-320 degrees. Weryk adds that J. Fairlamb obtained two 45-s follow-up images with the 2.2-m University of Hawaii telescope on Jan. 6.6 in 0".9 seeing that show a very condensed head of size 2".0 (FWHM); there was no obvious tail, but the comet's image partially overlaps a star. After the comet was posted to the Minor Planet Center's PCCP webpage, L. Buzzi (Varese, Italy) reported that one-hundred-forty-five 60-s stacked CMOS images obtained with a 0.84-m f/3.5 reflector on Jan. 8.15-8.20 UT at the Schiaparelli Observatory show the comet to have a softer aspect with respect to nearby stars, with a condensed coma 3" wide and a hint of a tail 3"-4" long in p.a. about 300 degrees. The available astrometry appears on MPEC 2025-B11, including pre- discovery CCD images obtained on 2024 Dec. 21.5 UT with the 1.5-m Mt. Lemmon reflector that were reported to the MPC on Jan. 13. The following two-body orbital elements by S. Nakano (Central Bureau) are from 32 observations spanning 2024 Dec. 21-2025 Jan. 16 (mean residual 0".3). T = 2025 Jan. 14.06037 TT Peri. = 102.98458 e = 0.6512767 Node = 69.86645 2000.0 q = 3.8225662 AU Incl. = 32.02872 a = 10.9616027 AU n = 0.02715770 P = 36.29 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 01 05 13 34.71 +26 00.3 3.641 3.823 93.2 14.9 20.5 2025 01 15 13 41.82 +26 20.8 3.523 3.823 100.2 14.7 20.4 2025 01 25 13 47.37 +26 51.1 3.411 3.823 107.4 14.2 20.3 2025 02 04 13 51.16 +27 29.4 3.308 3.825 114.7 13.5 20.3 2025 02 14 13 53.05 +28 12.9 3.216 3.829 121.7 12.7 20.2 2025 02 24 13 52.96 +28 57.9 3.139 3.834 128.4 11.7 20.2 2025 03 06 13 50.91 +29 39.9 3.079 3.840 134.4 10.6 20.1 2025 03 16 13 47.09 +30 13.4 3.039 3.847 139.1 9.7 20.1 2025 03 26 13 41.83 +30 33.6 3.021 3.856 141.9 9.2 20.1 2025 04 05 13 35.60 +30 36.2 3.026 3.865 142.2 9.1 20.1 2025 04 15 13 29.04 +30 18.3 3.054 3.877 140.0 9.6 20.1 2025 04 25 13 22.73 +29 39.3 3.104 3.889 135.8 10.4 20.2 2025 05 05 13 17.22 +28 40.0 3.176 3.902 130.1 11.4 20.2 2025 05 15 13 12.94 +27 22.9 3.267 3.917 123.6 12.4 20.3 2025 05 25 13 10.13 +25 51.3 3.374 3.933 116.6 13.3 20.4 2025 06 04 13 08.89 +24 08.4 3.496 3.950 109.4 14.0 20.5 2025 06 14 13 09.23 +22 17.7 3.628 3.969 102.2 14.5 20.6 2025 06 24 13 11.05 +20 21.8 3.769 3.988 95.0 14.7 20.7 2025 07 04 13 14.23 +18 22.9 3.916 4.008 87.8 14.7 20.8 2025 07 14 13 18.63 +16 23.0 4.065 4.030 80.8 14.4 20.9 2025 07 24 13 24.10 +14 23.4 4.215 4.052 73.9 13.9 21.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 January 18 (CBET 5496) Daniel W. E. Green