Electronic Telegram No. 5236 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 C1 = P/2016 C3 (JAHN) Jost Jahn (Amrum, Germany) has reported his discovery of a comet on images taken remotely in a regular observing program with the 60-cm ROTAT telescope of the Universitaet Tuebingen located at the Observatoire de Haute Provence. Jahn did not have time to look at the discovery images from Feb. 14 (tabulated below) until some four weeks later; when he noticed the cometary appearance (slightly diffuse with a weak 10" coma), Jahn asked that the Minor Planet Center post it to the PCCP webpage. 2023 UT R.A. (2000) Decl. Mag. Observer Feb. 14.94047 9 05 21.36 +32 42 36.3 19.1 Jahn 14.95764 9 05 20.45 +32 42 33.3 19.2 " 14.97481 9 05 19.51 +32 42 30.5 19.4 " 15.00914 9 05 17.65 +32 42 25.7 20.6 " 15.04313 9 05 15.82 +32 42 21.1 19.8 " 15.06126 9 05 14.84 +32 42 17.9 19.8 " 15.07937 9 05 13.87 +32 42 14.6 19.2 " Single-night observations were then identified in the MPC's "isolated tracklet file" that had been made on 2021 Oct. 11 with the Pan-STARRS1 1.8-m Ritchey- Chretien reflector at Haleakala (at w mag 22.6-22.9), on 2023 Feb. 19 at the XuYi station of the Purple Mountain Observatory red mag 20.2-20.3), and on 2023 Feb. 1 at Mt. Lemmon (1.5-m reflector; mag 19.8-20.0). D. Rankin, Lunar and Planetary Laboratory, University of Arizona, writes that inspection of the 2023 Feb. 1 images show a coma about 7".8 in diameter that is elongated east-west; he adds that it had faded a bit by Mar. 18.4 UT, when Mt. Lemmon images showed a coma about 8" in diameter (mag 20.5-21.0). R. Weryk, Department of Physics and Astronomy, University of Western Ontario, writes that four 45-s w-band survey images taken on 2022 Dec. 2.6 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala show the comet to be very condensed with a head 1".3 in size (full-width-at-half-maximum) in 1".2 seeing with a straight tail > 10" long toward p.a. 290 degrees. Weryk also identified pre-discovery Pan-STARRS1 images of the comet on five nights in 2016 (Feb. 10-Apr. 10), when it was at mag 22.5-24, and on 2021 Sept. 30, when it was at mag 22.7-23.0. K. Sarneczky, Konkoly Observatory, reports that he subsequently identified twelve pre-discovery 25-s unfiltered CCD images of this comet that were taken with the 0.60-m Schmidt telescope at Piszkesteto, Hungary, on 2023 Jan. 25.03; stacked images show a condensed coma 4" in diameter and a faint, straight tail about 7" long in p.a. 280 deg. Following a request by the Central Bureau, S. Deen (Simi Valley, CA, USA) reports that he identified very faint images of the comet (with no obvious cometary appearance) in publicly available data taken with the 4-m reflector (+ DECam) at Cerro Tololo on 2013 Nov. 22.1 (mag g = 24.3), 2013 Nov. 23.1 (r = 23.6), 2016 Apr. 9.1 (g = 23.3), and 2016 Apr. 10.2 (r = 22.7), as well as in three Pan-STARRS1 exposures taken on 2014 Dec. 13.5 (i = 21.5). Deen's astrometry is tabulated below. The single 2016 Feb. 10 Pan-STARRS1 position tabulated below was used for the designation P/2016 C3. 2013 UT R.A. (2000) Decl. Mag. Nov. 22.05504 23 31 44.97 - 1 25 58.3 24.3 23.08392 23 31 45.95 - 1 23 50.4 23.6 2014 UT R.A. (2000) Decl. Mag. Dec. 13.45837 5 01 31.51 +43 22 51.2 13.47168 5 01 30.69 +43 22 51.1 13.48501 5 01 29.82 +43 22 50.8 21.5 2016 UT R.A. (2000) Decl. Mag. Feb. 10.55564 12 50 06.88 - 4 28 18.3 23.9 Apr. 9.14433 12 12 40.43 - 3 59 36.7 23.3 10.15543 12 11 57.58 - 3 58 13.0 22.7 The available astrometry appears on MPEC 2023-F121. The following linked elliptical orbital elements by S. Nakano (Central Bureau) are from 53 observations spanning 2013-2023 (mean residual 0".4). There are no close approaches to major planets. Epoch = 2015 Apr. 8.0 TT T = 2015 Mar. 29.42886 TT Peri. = 104.97185 e = 0.3107893 Node = 1.86030 2000.0 q = 2.6726242 AU Incl. = 13.58998 a = 3.8778042 AU n = 0.12906999 P = 7.64 years Epoch = 2022 Oct. 28.0 TT T = 2022 Oct. 30.05411 TT Peri. = 104.77696 e = 0.3166055 Node = 1.58580 2000.0 q = 2.6341362 AU Incl. = 13.62910 a = 3.8544883 AU n = 0.13024288 P = 7.57 years Epoch = 2030 May 19.0 TT T = 2030 June 2.50113 TT Peri. = 105.04613 e = 0.3159926 Node = 1.50563 2000.0 q = 2.6401168 AU Incl. = 13.62100 a = 3.8597781 AU n = 0.12997522 P = 7.58 years Epoch = 2037 Dec. 8.0 TT T = 2037 Dec. 25.84608 TT Peri. = 104.80379 e = 0.3166777 Node = 1.44161 2000.0 q = 2.6395514 AU Incl. = 13.61844 a = 3.8628207 AU n = 0.12982169 P = 7.592 years Epoch = 2045 June 29.0 TT T = 2045 July 18.28582 TT Peri. = 104.25880 e = 0.3162858 Node = 1.40384 2000.0 q = 2.6393853 AU Incl. = 13.62759 a = 3.8603633 AU n = 0.12994567 P = 7.58 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 02 25 08 57.50 +32 06.9 1.830 2.725 148.7 10.9 19.8 2023 03 07 08 51.96 +31 14.8 1.912 2.740 139.1 13.7 19.9 2023 03 17 08 49.11 +30 10.2 2.014 2.757 129.6 16.1 20.0 2023 03 27 08 49.03 +28 56.7 2.132 2.774 120.4 18.1 20.2 2023 04 06 08 51.55 +27 37.1 2.262 2.792 111.8 19.4 20.3 2023 04 16 08 56.34 +26 13.5 2.402 2.812 103.5 20.3 20.5 2023 04 26 09 03.05 +24 46.9 2.548 2.832 95.8 20.7 20.6 2023 05 06 09 11.34 +23 17.7 2.697 2.853 88.4 20.7 20.8 2023 05 16 09 20.88 +21 46.3 2.848 2.875 81.3 20.3 20.9 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 March 24 (CBET 5236) Daniel W. E. Green