Electronic Telegram No. 5604 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 Q2 = P/2015 X9 = P/2020 O5 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala, HI, USA, on Aug. 23 (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".1-1".2 seeing show a very condensed head of size 1".3 (full-width- at-half-maximum) with a clear straight tail > 16" long in p.a. 240 degrees. The last two observations tabulated below were taken with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala. 2025 UT R.A. (2000) Decl. Mag. Aug. 23.47965 1 13 04.41 +30 28 39.3 21.4 23.49172 1 13 04.50 +30 28 45.2 21.3 23.50376 1 13 04.56 +30 28 50.6 21.6 23.51586 1 13 04.62 +30 28 56.6 21.5 23.59368 1 13 05.10 +30 29 33.5 22.1 23.59433 1 13 05.09 +30 29 33.7 21.7 Weryk and R. Wainscoat obtained three 60-s gri-band follow-up images with the 3.6-m Canada-France-Hawaii Telescope on Aug. 24.5 UT (queue observers L. Wells; queue coordinator V. Khatu) in 0".8-0".9 seeing; an image stack shows a very condensed head of size 1".1 (FWHM) with a tail > 40" long in p.a. 240 degrees. Three additional 60-s CFHT images obtained by them on Aug. 28.4 (queue observer J. Silva) shows a similar appearance. Two 600-s follow-up images obtained by J. Fairlamb on Aug. 31.5 with the University of Hawaii 2.2-m telescope in 1".4 seeing shows a very condensed head of size 2".0 (FWHM) and a straight tail about 40" long toward p.a. 240 degrees. Weryk then identified numerous apparently asteroidal Pan-STARRS1 images of the comet going back to 2015 Dec. 12.5 UT, when it was at mag 22.4-22.6. On 2016 Jan. 3.4, it was at mag 23.1-24.3. On 2020 July 30.6, it was at mag 22.3-23.4. On 2020 Nov. 16.4, it was at mag 22.1-22.2. On 2020 Dec. 7.3, it was at mag 22.8-23.3. On 2020 Dec. 10.4, it was at mag 22.0-22.9. On 2020 Dec. 15.4, it was at mag 21.3-22.3. On Pan-STARRS2 images taken on 2024 July 6.3, it was at mag 23.5-24.2. On Pan-STARRS2 images taken on 2025 Aug. 6.55- 6.56, it was at mag 22.4-22.5. On Pan-STARRS2 images taken on 2025 Aug. 8.5, it was at mag 21.6-23.1. The available astrometry appears on MPEC 2025-R67. The following orbital elements by S. Nakano (Central Bureau) are from 54 observations spanning 2015 Dec. 12-2025 Aug. 31 (mean residual 0".2). There are no close approaches to major planets. Epoch = 2004 Aug. 23.0 TT T = 2004 Sept. 1.67652 TT Peri. = 81.34890 e = 0.2437992 Node = 271.32914 2000.0 q = 2.2719820 AU Incl. = 14.78307 a = 3.0044694 AU n = 0.18925720 P = 5.21 years Epoch = 2009 Nov. 25.0 TT T = 2009 Nov. 13.22644 TT Peri. = 80.86463 e = 0.2440193 Node = 271.29303 2000.0 q = 2.2717419 AU Incl. = 14.77422 a = 3.0050265 AU n = 0.18920457 P = 5.21 years Epoch = 2015 Jan. 18.0 TT T = 2015 Jan. 29.11666 TT Peri. = 80.87112 e = 0.2421778 Node = 271.24807 2000.0 q = 2.2786546 AU Incl. = 14.77037 a = 3.0068458 AU n = 0.18903288 P = 5.21 years Epoch = 2020 Apr. 21.0 TT T = 2020 Apr. 17.58164 TT Peri. = 80.85907 e = 0.2378679 Node = 271.08032 2000.0 q = 2.2933649 AU Incl. = 14.78843 a = 3.0091434 AU n = 0.18881641 P = 5.22 years Epoch = 2025 July 24.0 TT T = 2025 July 11.01017 TT Peri. = 81.21664 e = 0.2373145 Node = 271.02810 2000.0 q = 2.2959671 AU Incl. = 14.78526 a = 3.0103719 AU n = 0.18870085 P = 5.22 years Epoch = 2030 Oct. 26.0 TT T = 2030 Oct. 12.14803 TT Peri. = 83.22614 e = 0.2378903 Node = 270.34644 2000.0 q = 2.2947558 AU Incl. = 14.75475 a = 3.0110569 AU n = 0.18863646 P = 5.22 years Epoch = 2035 Dec. 19.0 TT T = 2036 Jan. 4.09408 TT Peri. = 83.49746 e = 0.2389386 Node = 270.30374 2000.0 q = 2.2901755 AU Incl. = 14.75874 a = 3.0091863 AU n = 0.18881238 P = 5.22 years Epoch = 2041 Mar. 22.0 TT T = 2041 Mar. 21.49057 TT Peri. = 83.20412 e = 0.2433527 Node = 270.20468 2000.0 q = 2.2741439 AU Incl. = 14.76014 a = 3.0055533 AU n = 0.18915482 P = 5.21 years Epoch = 2046 June 24.0 TT T = 2046 June 4.51593 TT Peri. = 83.04170 e = 0.2450049 Node = 270.16328 2000.0 q = 2.2690642 AU Incl. = 14.76041 a = 3.0054024 AU n = 0.18916907 P = 5.21 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 17.0 and 2.5n = 7.5 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 07 06 15 55.20 -26 05.7 2.094 2.928 137.7 13.5 22.1 2024 07 26 15 53.06 -24 12.4 2.259 2.879 118.0 18.1 22.2 2024 08 15 16 00.81 -22 58.7 2.467 2.831 100.4 20.6 22.4 2024 09 04 16 16.95 -22 19.3 2.689 2.783 84.7 21.2 22.5 2024 09 24 16 39.76 -21 59.9 2.903 2.735 70.4 20.2 22.6 2024 10 14 17 07.75 -21 44.6 3.095 2.687 57.1 18.2 22.7 2024 11 03 17 39.72 -21 19.3 3.253 2.641 44.6 15.3 22.7 2024 11 23 18 14.62 -20 32.0 3.371 2.595 32.7 11.9 22.7 2024 12 13 18 51.48 -19 14.1 3.443 2.552 21.3 8.1 22.7 2025 01 02 19 29.40 -17 20.1 3.469 2.510 10.8 4.2 22.7 2025 01 22 20 07.60 -14 47.8 3.449 2.471 5.4 2.1 22.6 2025 02 11 20 45.47 -11 38.1 3.386 2.435 13.1 5.3 22.5 2025 03 03 21 22.53 -07 54.6 3.285 2.402 22.9 9.2 22.4 2025 03 23 21 58.48 -03 42.7 3.149 2.373 32.8 13.1 22.3 2025 04 12 22 33.13 +00 51.2 2.987 2.348 42.6 16.8 22.2 2025 05 02 23 06.30 +05 39.6 2.802 2.328 52.4 20.1 22.0 2025 05 22 23 37.73 +10 34.9 2.602 2.312 62.3 22.8 21.8 2025 06 11 00 06.93 +15 29.0 2.391 2.302 72.6 24.9 21.6 2025 07 01 00 32.99 +20 13.2 2.175 2.297 83.6 26.1 21.4 2025 07 21 00 54.37 +24 37.0 1.962 2.297 95.6 26.1 21.2 2025 08 10 01 08.74 +28 25.8 1.762 2.302 109.1 24.6 20.9 2025 08 30 01 13.34 +31 15.3 1.587 2.312 124.3 21.1 20.7 2025 09 19 01 06.68 +32 27.8 1.461 2.328 140.9 15.8 20.6 2025 10 09 00 52.05 +31 28.2 1.406 2.348 154.6 10.5 20.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 September 9 (CBET 5604) Daniel W. E. Green