Electronic Telegram No. 5328 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 Y1 (GIBBS) A. R. Gibbs reports his discovery of another comet on 30-s CCD exposures obtained on Dec. 17 with the Mt. Lemmon Survey's 1.5-m reflector (discovery observations tabulated below); in great seeing conditions, there was a compact coma 5" across with a tail in p.a. 285 degrees that was involved with a field star. Four follow-up 80-s exposures taken shortly thereafter show a condensed coma 6" across with a straight, narrow, 25" tail in p.a. 290 deg. 2023 UT R.A. (2000) Decl. Mag. Observer Dec. 17.50149 11 15 19.51 +12 09 13.9 Gibbs 17.50665 11 15 19.91 +12 09 13.0 20.4 " 17.51181 11 15 20.38 +12 09 12.2 20.7 " 17.53335 11 15 22.00 +12 09 07.2 20.1 " 17.53434 11 15 22.00 +12 09 06.9 " 17.53533 11 15 22.10 +12 09 07.0 " 17.53633 11 15 22.20 +12 09 06.6 " After the comet was posted on the Minor Planet Center's PCCP webpage, R. Weryk (Department of Physics and Astronomy, University of Western Ontario) noted that four 45-s w-band survey images obtained in roughly 1".6 seeing on Dec. 17.6 UT with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala show a diffuse coma of size 2".0 (full-width-at-half-maximum) with a 5" tail in p.a. 290 degrees. Pre-discovery apparently asteoridal Pan-STARRS2 images were also found on Nov. 24.6 (mag 21.5-22.0). The available astrometry appears on MPEC 2023-Y60. The following elliptical orbital elements by S. Nakano (Central Bureau) are from 23 observations spanning 2023 Nov. 24-Dec. 19 (mean residual 0".4), with some concern about the lone Nov. 24 observations. There appear to be no close approaches to major planets. T = 2023 Nov. 29.09424 TT Peri. = 51.47507 e = 0.4173682 Node = 78.33322 2000.0 q = 2.0650734 AU Incl. = 6.34463 a = 3.5443883 AU n = 0.14770396 P = 6.67 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 16.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 12 02 10 52.81 +13 20.1 1.818 2.065 89.8 28.5 20.4 2023 12 12 11 07.83 +12 31.0 1.715 2.067 96.2 28.3 20.3 2023 12 22 11 21.00 +11 54.7 1.615 2.073 103.1 27.5 20.2 2024 01 01 11 32.01 +11 33.6 1.521 2.081 110.5 26.3 20.1 2024 01 11 11 40.49 +11 30.0 1.434 2.091 118.6 24.4 20.0 2024 01 21 11 46.07 +11 45.1 1.357 2.105 127.4 21.8 19.9 2024 01 31 11 48.51 +12 17.7 1.293 2.121 136.8 18.5 19.8 2024 02 10 11 47.73 +13 04.9 1.244 2.140 146.9 14.6 19.8 2024 02 20 11 44.00 +14 00.0 1.216 2.161 157.0 10.3 19.8 2024 03 01 11 38.07 +14 54.1 1.210 2.184 165.8 6.4 19.8 2024 03 11 11 31.00 +15 37.8 1.228 2.209 168.0 5.4 19.9 2024 03 21 11 24.10 +16 03.5 1.270 2.236 161.2 8.2 20.0 2024 03 31 11 18.56 +16 07.1 1.336 2.265 151.7 12.1 20.2 2024 04 10 11 15.13 +15 48.6 1.422 2.296 142.0 15.6 20.4 2024 04 20 11 14.24 +15 09.9 1.527 2.329 132.7 18.5 20.6 2024 04 30 11 15.87 +14 14.6 1.647 2.362 124.0 20.7 20.8 2024 05 10 11 19.82 +13 06.0 1.778 2.397 115.8 22.3 21.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 December 20 (CBET 5328) Daniel W. E. Green