Electronic Telegram No. 5407 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/2024 L3 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on June 7 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala; the discovery observations and additional Pan-STARRS2 observations found by Weryk from May 29 and June 2 are tabulated below. 2024 UT R.A. (2000) Decl. Mag. May 29.42910 17 05 49.71 +48 47 37.6 22.2 29.46464 17 05 47.13 +48 47 48.9 22.3 June 2.44050 17 01 00.37 +49 07 17.3 22.3 2.45296 17 00 59.47 +49 07 20.9 21.7 2.46538 17 00 58.56 +49 07 23.8 22.8 7.47828 16 54 52.15 +49 27 33.9 22.4 7.50203 16 54 50.38 +49 27 39.1 22.1 7.51390 16 54 49.56 +49 27 40.7 21.7 Weryk obtained three 90-s follow-up gri-band images with the 3.6-m Canada- France-Hawaii Telescope on June 10.26 UT (R. Wainscoat's schedule; queue observer A. Acohido; queue coordinator H. Flewelling), which show an obvious tail; the comet's diffuse head showed a size of about 1".4 (full-width-at- half-maximum) in 0".8 seeing, with a 2" tail toward p.a. 140 degrees. Three additional 90-s gri-band CFHT images taken on June 29.4 (queue coordinator T. Burdullis) in 0".9 seeing show a very condensed head of size 1".2 (FWHM) and a straight tail 6" long toward p.a. 145 degrees. Six 90-s gri-band CFHT images taken on July 8.4 (queue observer L. Wells; queue coordinator H. Flewelling) in 0".6 seeing show a very condensed head of size 1".2 (FWHM) with a straight tail 6" long in p.a. 135 deg. The available astrometry appears on MPEC 2024-N105. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 31 observations spanning 2024 May 29-July 8 (mean residual 0".3). The comet passed 1.34 AU from Saturn on 2020 Nov. 23 UT. T = 2023 Nov. 25.85264 TT Peri. = 59.19543 Node = 294.94936 2000.0 q = 6.8582245 AU Incl. = 111.58487 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 06 19 16 40.87 +49 55.4 6.657 6.990 105.0 8.1 21.9 2024 06 29 16 29.24 +49 59.8 6.723 7.003 101.9 8.2 21.9 2024 07 09 16 18.58 +49 47.7 6.801 7.017 98.1 8.2 21.9 2024 07 19 16 09.25 +49 22.0 6.888 7.031 93.9 8.3 22.0 2024 07 29 16 01.45 +48 45.8 6.980 7.045 89.5 8.3 22.0 2024 08 08 15 55.27 +48 02.3 7.076 7.061 85.0 8.2 22.0 2024 08 18 15 50.71 +47 14.7 7.172 7.076 80.5 8.1 22.1 2024 08 28 15 47.67 +46 25.7 7.265 7.093 76.2 8.0 22.1 2024 09 07 15 46.05 +45 37.8 7.352 7.110 72.2 7.8 22.1 2024 09 17 15 45.69 +44 53.0 7.431 7.127 68.7 7.5 22.2 2024 09 27 15 46.43 +44 13.3 7.500 7.145 65.6 7.3 22.2 2024 10 07 15 48.13 +43 40.0 7.557 7.163 63.3 7.2 22.2 2024 10 17 15 50.63 +43 14.5 7.602 7.182 61.7 7.0 22.3 2024 10 27 15 53.77 +42 57.8 7.632 7.202 60.9 6.9 22.3 2024 11 06 15 57.41 +42 51.0 7.649 7.222 61.1 6.9 22.3 2024 11 16 16 01.41 +42 54.9 7.651 7.243 62.2 6.9 22.3 2024 11 26 16 05.61 +43 10.0 7.641 7.264 64.1 7.0 22.3 2024 12 06 16 09.87 +43 36.8 7.618 7.285 66.8 7.1 22.3 2024 12 16 16 14.03 +44 15.7 7.584 7.307 70.0 7.3 22.3 2024 12 26 16 17.93 +45 06.7 7.543 7.330 73.8 7.4 22.3 2025 01 05 16 21.39 +46 09.6 7.495 7.353 77.9 7.5 22.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 July 9 (CBET 5407) Daniel W. E. Green