Electronic Telegram No. 5326 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 X3 (PANSTARRS) Yudish Ramanjooloo, Institute for Astronomy, University of Hawaii, reports the discovery of another comet in images obtained on Dec. 7 with the Pan-STARRS1 and Pan-STARRS2 1.8-m Ritchey-Chretien reflectors at Haleakala (discovery observations tabulated below). Three 45-s w-band Pan-STARRS2 exposures (the first three tabulated below) taken in seeing around 1".3 show a very diffuse coma of size 2".1 (full-width-at-half-maximum) with a very faint tail about 3" long toward p.a. 240 degrees. 2023 UT R.A. (2000) Decl. Mag. Dec. 7.35062 4 50 53.69 +23 54 21.4 21.1 7.36297 4 50 53.10 +23 54 21.4 21.0 7.37545 4 50 52.47 +23 54 21.4 21.0 7.49363 4 50 46.75 +23 54 22.1 20.9 7.49427 4 50 46.71 +23 54 22.1 21.0 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, adds that eight 45-s Pan-STARRS2 w-band survey images taken on Dec. 10.32- 10.36 UT in variable seeing (around 1".5) show a very condensed head of size 1".9 (FWHM) with an obvious 5" tail toward p.a. 260 degrees. After the comet was posted to the Minor Planet Center's PCCP webpage, other CCD astrometrists have commented on the object's appearance. F. D. Romanov (Yuzhno-Morskoy, Nakhodka, Russia) writes that fifteen stacked 60-s exposures taken remotely on Dec. 9.0 UT with the 2.0-m f/10 Ritchey-Chretien reflector (+ Sloan r' filter) at La Palma show a compact 6" coma with no tail (magnitude near 20.7). Twelve stacked 120-s exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) on Dec. 10.4 with a 0.43-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) show only a stellar appearance; the magnitude was 21.4 as measured within a circular aperture of radius 3".8. The available astrometry appears on MPEC 2023-X269; included are pre- discovery single-night apparently asteroidal observations from the 2.25-m Bok telescope at Kitt Peak on Nov. 11.4 UT (observer K. Wierzchos; mag 21.3) and from Pan-STARRS1 on Dec. 4.34-4.36 (mag 21.5-21.6) that were in the MPC's "isolated tracklet file", as well as additional Pan-STARRS2 observations on Oct. 22.5 (mag 21.7-22.2) and additional Pan-STARRS1 observations on Oct. 26.5 (mag 21.5-22.0). The following two-body elliptical orbital elements by S. Nakano (Central Bureau) are from 49 observations spanning 2023 Oct. 22-Dec. 11 (mean residual 0".2). These indicate that the comet passed 0.26 AU from Jupiter on 2021 July 25 UT. T = 2024 Apr. 22.79554 TT Peri. = 41.01108 e = 0.2876701 Node = 62.01617 2000.0 q = 3.0286940 AU Incl. = 4.48439 a = 4.2518134 AU n = 0.11241979 P = 8.77 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 15.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 12 02 04 55.04 +23 53.5 2.138 3.120 173.9 1.9 20.6 2023 12 12 04 47.27 +23 54.5 2.127 3.108 173.9 1.9 20.6 2023 12 22 04 39.89 +23 53.5 2.146 3.097 162.1 5.6 20.6 2024 01 01 04 33.77 +23 52.0 2.192 3.087 150.6 9.0 20.6 2024 01 11 04 29.56 +23 51.9 2.262 3.077 139.5 12.0 20.7 2024 01 21 04 27.67 +23 54.7 2.353 3.068 128.9 14.5 20.8 2024 01 31 04 28.26 +24 01.3 2.461 3.060 118.9 16.4 20.8 2024 02 10 04 31.27 +24 11.8 2.580 3.053 109.4 17.7 20.9 2024 02 20 04 36.57 +24 25.6 2.707 3.047 100.6 18.6 21.0 2024 03 01 04 43.93 +24 41.9 2.838 3.042 92.2 19.0 21.1 2024 03 11 04 53.12 +24 59.4 2.970 3.037 84.3 19.0 21.2 2024 03 21 05 03.90 +25 16.7 3.102 3.034 76.8 18.6 21.3 2024 03 31 05 16.04 +25 32.6 3.230 3.031 69.7 18.0 21.4 2024 04 10 05 29.34 +25 45.9 3.353 3.029 62.8 17.1 21.5 2024 04 20 05 43.62 +25 55.4 3.469 3.029 56.3 16.0 21.6 2024 04 30 05 58.70 +26 00.2 3.577 3.029 49.9 14.7 21.6 2024 05 10 06 14.42 +25 59.6 3.677 3.030 43.8 13.3 21.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 December 13 (CBET 5326) Daniel W. E. Green