Electronic Telegram No. 5276 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/2023 M2 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on June 22 (discovery observations tabulated below) with the Pan-STARRS1 1.8-m Ritchey- Chretien reflector at Haleakala, Hawaii. Three 45-s w-band survey images show a very condensed head of size 1".7 (full-width-at-half-maximum) in 1".3 seeing with a clear 6" tail in p.a. 270 degrees. 2023 UT R.A. (2000) Decl. Mag. June 22.56949 22 58 06.14 -27 55 06.1 20.3 22.57979 22 58 06.44 -27 55 09.2 20.2 22.59412 22 58 06.82 -27 55 13.7 20.2 Weryk adds that three 60-s gri-band follow-up images obtained by R. Wainscoat and himself on June 23.56 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer L. Wells; queue coordinator T. Burdullis) show this to be clearly a comet, with a very condensed coma of size 1".3 (FWHM) in 0".7 seeing and a clear, broad tail > 18" long spanning p.a. 250-285 deg. Eight additional follow-up unfiltered images obtained by J. Fairlamb with the University of Hawaii 2.2-m reflector at Mauna Kea on June 27.6 show a very condensed head of size 1".5 in 1".3 seeing, with a clear 6" tail in p.a. 260 degrees; four additional 45-s exposures by Fairlamb on June 29.6 show a very condensed coma of size 2".0 (FWHM) in 1".6 seeing and a clear tail 6" long toward p.a. 265 degrees. After the comet was posted to the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that eight stacked 120-s CCD exposures taken remotely on June 23.76 UT with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, show a strongly condensed coma 6" in diameter with a 15" tail toward p.a. 270 degrees; the magnitude was 19.4 as measured within a circular aperture of radius 4".9. The available astrometry appears on MPEC 2023-N15. The following elliptical orbital elements by S. Nakano (Central Bureau) are from 39 observations spanning June 22-July 2 (mean residual 0".2). These indicate that the comet passed 0.67 AU from Jupiter in 2012 December. T = 2023 July 17.19491 TT Peri. = 241.73531 e = 0.3691677 Node = 83.09815 2000.0 q = 3.5028733 AU Incl. = 19.68649 a = 5.5527802 AU n = 0.07532486 P = 13.08 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 06 25 22 59.17 -28 07.9 2.935 3.505 116.3 15.1 19.2 2023 07 05 23 02.48 -29 06.9 2.827 3.504 124.4 13.8 19.1 2023 07 15 23 03.91 -30 14.5 2.734 3.503 132.6 12.3 19.0 2023 07 25 23 03.39 -31 27.7 2.659 3.503 140.6 10.6 19.0 2023 08 04 23 00.99 -32 41.5 2.605 3.504 147.7 8.9 18.9 2023 08 14 22 56.95 -33 50.5 2.574 3.506 152.9 7.6 18.9 2023 08 24 22 51.67 -34 48.9 2.568 3.509 154.7 7.1 18.9 2023 09 03 22 45.77 -35 31.3 2.588 3.513 152.3 7.7 18.9 2023 09 13 22 39.93 -35 54.5 2.632 3.518 146.8 9.0 19.0 2023 09 23 22 34.84 -35 57.1 2.700 3.523 139.4 10.7 19.0 2023 10 03 22 31.09 -35 39.7 2.788 3.530 131.3 12.3 19.1 2023 10 13 22 29.03 -35 04.3 2.894 3.537 122.9 13.7 19.2 2023 10 23 22 28.88 -34 13.6 3.014 3.545 114.6 14.8 19.3 2023 11 02 22 30.65 -33 10.5 3.145 3.554 106.3 15.5 19.4 2023 11 12 22 34.22 -31 57.5 3.283 3.564 98.3 16.0 19.5 2023 11 22 22 39.44 -30 36.8 3.427 3.574 90.5 16.0 19.6 2023 12 02 22 46.09 -29 10.3 3.572 3.586 82.9 15.8 19.7 2023 12 12 22 53.97 -27 39.2 3.717 3.598 75.4 15.4 19.8 2023 12 22 23 02.87 -26 04.8 3.858 3.610 68.2 14.7 19.9 2024 01 01 23 12.61 -24 28.1 3.994 3.624 61.2 13.8 20.0 2024 01 11 23 23.02 -22 49.8 4.122 3.638 54.4 12.7 20.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 July 6 (CBET 5276) Daniel W. E. Green