Electronic Telegram No. 5519 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 D5 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Feb. 28 with the Pan-STARRS2 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 very diffuse coma of size 2".1 (full-width-at-half-maximum) and a straight tail 6" long in p.a. 350 degrees. 2025 UT R.A. (2000) Decl. Mag. Feb. 28.54313 13 01 47.50 - 2 24 04.0 20.6 28.55398 13 01 45.96 - 2 24 20.9 20.6 28.57571 13 01 42.84 - 2 24 54.4 21.0 28.63764 13 01 33.93 - 2 26 31.2 21.9 28.63845 13 01 33.80 - 2 26 32.7 22.2 Weryk and R. Wainscoat obtained three 60-s gri-band follow-up observations on Mar. 1.44 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer J. Nagasako; queue coordinator H. Flewelling) in 0".9 seeing that show a very condensed head of size 1".2 (FWHM) and a tail about 4" long in p.a. 340 degrees. Three additional 60-s gri-band CFHT images taken on Mar. 4.5 (queue observer A. Acohido; queue coordinator V. Khatu) in 0".6-0".7 seeing show a very condensed head of size 0".9-1".0 (FWHM) with a tail about 4" long in p.a. 340 degrees. After Weryk moved the object to the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) obatined twenty-four stacked 60-s CCD exposures remotely with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, on Mar. 1.7 that show a strongly condensed coma 8" in diameter with no tail; the magnitude was 20.2 as measured within a circular aperture of radius 4".9. The available astrometry appears on MPEC 2025-E99. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 22 observations spanning Feb. 20-Mar. 4 (mean residual 0".5). There are no close approaches to major planets. T = 2025 May 13.30511 TT Peri. = 211.50335 Node = 0.73876 2000.0 q = 2.0121102 AU Incl. = 73.39093 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 17.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 02 14 13 28.00 +03 07.9 1.557 2.274 125.2 20.8 20.8 2025 02 24 13 11.64 -00 30.9 1.384 2.221 138.1 17.3 20.5 2025 03 06 12 47.84 -04 51.0 1.245 2.174 152.4 12.2 20.2 2025 03 16 12 16.49 -09 44.2 1.154 2.132 165.7 6.6 19.9 2025 03 26 11 39.64 -14 41.2 1.118 2.095 164.1 7.5 19.8 2025 04 05 11 01.71 -19 01.7 1.140 2.065 149.3 14.3 19.8 2025 04 15 10 27.72 -22 23.1 1.212 2.041 134.0 20.7 19.9 2025 04 25 10 00.66 -24 49.9 1.320 2.024 120.4 25.4 20.1 2025 05 05 09 41.18 -26 41.2 1.448 2.015 108.8 28.3 20.2 2025 05 15 09 28.40 -28 15.6 1.587 2.012 99.1 29.7 20.4 2025 05 25 09 21.01 -29 46.2 1.728 2.017 90.9 30.1 20.6 2025 06 04 09 17.85 -31 21.0 1.865 2.029 84.1 29.8 20.8 2025 06 14 09 17.95 -33 05.2 1.995 2.048 78.4 29.1 21.0 2025 06 24 09 20.61 -35 01.4 2.114 2.074 73.8 28.1 21.2 2025 07 04 09 25.34 -37 11.9 2.223 2.107 70.1 27.0 21.3 2025 07 14 09 31.77 -39 38.0 2.321 2.145 67.3 25.9 21.5 2025 07 24 09 39.69 -42 20.3 2.408 2.189 65.4 25.0 21.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 March 5 (CBET 5519) Daniel W. E. Green