Electronic Telegram No. 5327 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/2023 X4 (HOGAN) Joshua K. Hogan, Lunar and Planetary Laboratory (LPL), University of Arizona, reports his discovery of a comet on CCD images obtained with the Mt. Lemmon Survey's 1.5-m reflector on Dec. 13 (discovery observations tabulated below). Hogan noted condensed coma of diameter 5".1 with a prominent tail visible in 30-s exposures; four stacked 30-s exposures show a possible second tail. The tail length was given as 10".9, with p.a. 2.5 and 337.3 degrees also provided without elaboration. 2023 UT R.A. (2000) Decl. Mag. Observer Dec. 13.33238 7 23 30.24 +36 35 45.2 19.8 Hogan 13.33765 7 23 30.08 +36 35 46.3 19.8 " 13.34293 7 23 29.98 +36 35 47.0 19.8 " 13.34820 7 23 29.85 +36 35 48.6 19.8 " 13.41358 7 23 28.17 +36 36 02.7 20.0 " 13.42704 7 23 27.82 +36 36 05.2 19.7 " 13.44044 7 23 27.51 +36 36 08.1 19.8 " 13.45373 7 23 27.17 +36 36 10.9 20.1 " K. Wierzchos, LPL, writes that four 30-s unfiltered exposures obtained with the Steward Observatory 1.0-m reflector at Mt. Lemmon on Dec. 13.43-13.47 UT show a condensed coma of diameter 5" with a straight 13" tail in p.a. 260 degrees. After the comet was posted to the Minor Planet Center's PCCP webpage, R. Weryk (Department of Physics and Astronomy, University of Western Ontario) found single-night images of this comet over three nights in the MPC's "isolated tracklet file": Sept. 20.6 (Pan-STARRS1 1.8-m reflector at Haleakala; mag 22.1-22.2), Oct. 16.6 (Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala; mag 21.5-22.0), and Oct. 22.4 (Mt. Lemmon Survey; mag 21.2-21.6). Weryk adds that four 45-s w-band survey images on Sept. 20 in 1".1 or better seeing show a very condensed head of size 1".5 (full-width-at- half-maximum) with a short tail about 1" long in p.a. 270 degrees. Four 45-s Pan-STARRS2 w-band survey images on Oct. 16 in 1".2 or better seeing show a very condensed head of size 1".4 (FWHM) and a short tail about 3" long towards p.a. 270 degrees. The available astrometry appears on MPEC 2023-X272. The following orbital elements by S. Nakano (Central Bureau) are from 24 observations spanning 2023 Sept. 20-Dec. 13 (mean residual 0".2). There are no close approaches to major planets. Epoch = 2024 May 10.0 TT T = 2024 May 24.85539 TT Peri. = 100.56415 e = 0.6308741 Node = 28.76244 2000.0 q = 3.6576079 AU Incl. = 11.59447 a = 9.9088347 AU n = 0.03159877 P = 31.19 years Epoch = 2055 July 27.0 TT T = 2055 Aug. 2.32123 TT Peri. = 100.79380 e = 0.6299574 Node = 28.69909 2000.0 q = 3.6520001 AU Incl. = 11.60081 a = 9.8691349 AU n = 0.03178963 P = 31.00 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 12 02 07 26.93 +35 53.8 3.062 3.862 139.2 9.6 20.1 2023 12 12 07 24.03 +36 31.0 2.963 3.840 148.9 7.6 20.0 2023 12 22 07 19.42 +37 04.7 2.890 3.819 157.8 5.6 20.0 2024 01 01 07 13.60 +37 31.6 2.845 3.800 164.1 4.1 19.9 2024 01 11 07 07.20 +37 49.0 2.827 3.781 163.6 4.2 19.9 2024 01 21 07 00.98 +37 55.4 2.839 3.764 156.9 5.9 19.9 2024 01 31 06 55.70 +37 50.5 2.878 3.748 147.8 8.1 19.9 2024 02 10 06 51.97 +37 35.7 2.941 3.733 138.0 10.2 19.9 2024 02 20 06 50.21 +37 12.8 3.025 3.720 128.3 12.0 20.0 2024 03 01 06 50.61 +36 43.9 3.125 3.707 118.9 13.5 20.0 2024 03 11 06 53.17 +36 10.6 3.239 3.696 109.9 14.6 20.1 2024 03 21 06 57.81 +35 34.2 3.362 3.687 101.2 15.4 20.2 2024 03 31 07 04.30 +34 55.4 3.490 3.679 92.9 15.7 20.2 2024 04 10 07 12.44 +34 14.3 3.620 3.672 85.0 15.8 20.3 2024 04 20 07 21.98 +33 30.8 3.750 3.666 77.5 15.5 20.4 2024 04 30 07 32.69 +32 44.9 3.877 3.662 70.3 15.0 20.5 2024 05 10 07 44.36 +31 56.0 4.000 3.659 63.3 14.3 20.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 December 14 (CBET 5327) Daniel W. E. Green