Electronic Telegram No. 5441 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/2024 R1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). Three stacked 45-s w-band survey images taken in 1".2 seeing show a very condensed head of size 1".4 (full-width-at-half- maximum) with a broad tail about 10" long spanning p.a. 245-275 degrees. 2024 UT R.A. (2000) Decl. Mag. Sept. 1.55542 1 19 11.20 -18 30 05.5 21.3 1.57615 1 19 10.90 -18 30 13.3 21.2 1.58649 1 19 10.75 -18 30 17.2 21.0 Weryk also identified three pre-discovery 45-s w-band survey images taken in 1".3 seeing with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala showing the comet on Aug. 27.55-27.58 UT with a very condensed head of size 1".5 (FWHM) and a straight tail about 4" long in p.a. 250 deg. Weryk further adds that three 60-s gri-band follow-up images, which were taken on Sept. 2.4 with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (by Weryk and R. Wainscoat, with queue observer J. Silva and queue coordinator V. Khatu) in 0".7 seeing show a very condensed head of size 0".9 (FWHM) and a broad tail about 14" long spanning p.a. 245-270 deg. After the comet was posted on the Minor Planet Center's PCCP webpage, S. Deen (Simi Valley, CA, USA) identified archival images of the comet taken on June 3.4 and July 10.4 UT with the Cerro Tololo 4-m reflector (+ DECam). The two 90-s r-band images taken on June 3 show an essentially stellar head in 1".1 seeing (magnitude 21.5-21.7) with an 8"-long tail in p.a. 247 degrees. The single 500-s exposure taken with a 464-nm filter in 1".5 seeing shows a head of size 1'.8 (FWHM) and magnitude g = 21.0, though the comet's image is trailed due to the long exposure; there appears to be a tail roughly 7" long in p.a. 241 deg. Sixteen stacked 60-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) on Sept. 3.8 UT with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, show a moderately condensed coma 8" in diameter and no tail; the magnitude was 20.6 as measured within a circular aperture of radius 4".3. The available astrometry appears on MPEC 2024-R182. The following orbital elements by S. Nakano (Central Bureau) are from 21 observations spanning 2024 June 3-Sept. 4 (mean residual 0".1). These indicate that the comet passed 0.94 AU from Jupiter on 2014 Dec. 27 UT. Nakano was unable to find additional observations in archival astrometry files. Epoch = 2004 Nov. 11.0 TT T = 2004 Oct. 28.13142 TT Peri. = 224.40992 e = 0.4641514 Node = 91.54569 2000.0 q = 1.8979359 AU Incl. = 13.57638 a = 3.5419257 AU n = 0.14785803 P = 6.67 years Epoch = 2011 July 18.0 TT T = 2011 June 29.33860 TT Peri. = 224.63283 e = 0.4649663 Node = 91.45996 2000.0 q = 1.8920144 AU Incl. = 13.57584 a = 3.5362525 AU n = 0.14821398 P = 6.65 years Epoch = 2018 Jan. 2.0 TT T = 2018 Jan. 13.39786 TT Peri. = 230.37758 e = 0.4929748 Node = 85.06640 2000.0 q = 1.7497447 AU Incl. = 12.74168 a = 3.4510013 AU n = 0.15373983 P = 6.41 years Epoch = 2024 June 19.0 TT T = 2024 June 15.65887 TT Peri. = 230.57470 e = 0.4929477 Node = 84.98377 2000.0 q = 1.7497238 AU Incl. = 12.73643 a = 3.4507755 AU n = 0.15375492 P = 6.41 years Epoch = 2030 Dec. 5.0 TT T = 2030 Dec. 18.45747 TT Peri. = 232.14543 e = 0.4804990 Node = 83.88508 2000.0 q = 1.8182814 AU Incl. = 12.49305 a = 3.5000536 AU n = 0.15051924 P = 6.55 years Epoch = 2037 July 1.0 TT T = 2037 July 11.70062 TT Peri. = 232.32064 e = 0.4798147 Node = 83.79507 2000.0 q = 1.8236241 AU Incl. = 12.47787 a = 3.5057199 AU n = 0.15015446 P = 6.56 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 17.5 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 08 18 01 17.75 -16 57.4 1.021 1.841 129.8 25.0 20.2 2024 08 28 01 19.66 -18 01.2 0.998 1.871 137.3 21.5 20.2 2024 09 07 01 17.60 -19 02.0 0.989 1.903 144.8 17.8 20.3 2024 09 17 01 12.19 -19 47.9 0.997 1.939 151.3 14.4 20.4 2024 09 27 01 04.57 -20 08.2 1.023 1.978 155.1 12.3 20.5 2024 10 07 00 56.19 -19 56.2 1.070 2.019 154.6 12.3 20.7 2024 10 17 00 48.59 -19 10.3 1.138 2.062 150.0 14.0 20.9 2024 10 27 00 42.92 -17 54.7 1.226 2.107 143.1 16.4 21.2 2024 11 06 00 39.80 -16 15.9 1.333 2.154 135.4 18.9 21.5 2024 11 16 00 39.44 -14 20.9 1.456 2.202 127.4 20.9 21.7 2024 11 26 00 41.67 -12 16.1 1.594 2.251 119.5 22.4 22.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 September 8 (CBET 5441) Daniel W. E. Green