Electronic Telegram No. 5362 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/2019 O2 (PANSTARRS) An apparently asteroidal object discovered images obtained on 2019 July 24 (discovery observations tabulated below) with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala has been found to show cometary activity as reported by observers elsewhere. The object was designated A/2019 O2 when announced on MPEC 2019-P54 due to its nearly parabolic orbit. 2019 UT R.A. (2000) Decl. Mag. July 24.52254 20 20 35.84 +75 40 48.0 20.5 24.53640 20 20 34.31 +75 40 47.9 20.7 24.55022 20 20 32.86 +75 40 47.7 20.8 24.56407 20 20 31.40 +75 40 47.3 20.6 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, writes that he searched for the comet in Pan-STARRS exposures, finding apparently stellar pre-discovery Pan-STARRS1 images of the comet as far back as 2014 Dec. 8 (at mag 21.7-22.3) and 20 (mag 22.5-22.9), as well as on 2016 Sept. 19 (mag 21.9-22.3) and Nov. 7 (mag 20.9-22.4). Weryk identified post- discovery observations that all show the comet as stellar in appearance. A single observation of the comet with a stellar appearance that was made with the 3.6-m Canada-France-Hawaii Telescope on 2011 Nov. 28 was measured and reported by S. Deen (Simi Valley, CA, USA) in 2022 at magnitude r = 22.6. The astrometry for these observations appear on MPEC 2024-E7. K. Wierzchos, Lunar and Planetary Laboratory, University of Arizona, writes that four unfiltered 30-s exposures taken on 2023 June 30.3 UT with the Mt. Lemmon 1.5-m reflector show a short, broad tail of length 6" spanning p.a. 190-270 degrees with a very condensed coma of size 3" and magnitude 19.8-19.9. The following orbital elements by S. Nakano (Central Bureau) are from 392 observations spanning 2011 Nov. 28-2023 Sept. 12 (mean residual 0".3), with corresponding "original" and "future" values of 1/a (with respect to the solar-system barycenter) being +0.017236 and +0.017271 (+/- 0.000001) AU**-1, respectively. The orbital period is around 440 years. Epoch = 2023 Apr. 6.0 TT T = 2023 Apr. 7.22843 TT Peri. = 129.63980 e = 0.8327256 Node = 48.26287 2000.0 q = 9.6827741 AU Incl. = 93.30726 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 6.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 01 11 16 10.28 +15 48.5 10.222 9.784 61.1 5.0 19.5 2024 01 21 16 12.23 +15 46.9 10.112 9.792 68.4 5.4 19.5 2024 01 31 16 13.64 +15 50.0 9.990 9.799 76.0 5.6 19.4 2024 02 10 16 14.43 +15 57.3 9.861 9.807 84.0 5.7 19.4 2024 02 20 16 14.54 +16 07.9 9.729 9.815 92.1 5.8 19.4 2024 03 01 16 13.92 +16 20.9 9.598 9.824 100.3 5.7 19.3 2024 03 11 16 12.53 +16 35.1 9.472 9.832 108.5 5.5 19.3 2024 03 21 16 10.38 +16 49.4 9.356 9.841 116.5 5.2 19.3 2024 03 31 16 07.50 +17 02.3 9.254 9.850 124.2 4.8 19.3 2024 04 10 16 03.94 +17 12.6 9.170 9.860 131.3 4.4 19.3 2024 04 20 15 59.80 +17 18.9 9.108 9.869 137.3 4.0 19.3 2024 04 30 15 55.21 +17 20.0 9.070 9.879 141.6 3.6 19.2 2024 05 10 15 50.33 +17 15.2 9.058 9.889 143.6 3.5 19.2 2024 05 20 15 45.32 +17 03.6 9.073 9.900 143.0 3.5 19.3 2024 05 30 15 40.36 +16 45.1 9.115 9.910 139.8 3.8 19.3 2024 06 09 15 35.62 +16 19.8 9.182 9.921 134.6 4.2 19.3 2024 06 19 15 31.26 +15 48.1 9.274 9.932 128.0 4.6 19.3 2024 06 29 15 27.40 +15 10.6 9.386 9.943 120.7 5.0 19.3 2024 07 09 15 24.12 +14 28.3 9.516 9.955 112.8 5.4 19.4 2024 07 19 15 21.51 +13 41.9 9.660 9.967 104.7 5.7 19.4 2024 07 29 15 19.58 +12 52.7 9.814 9.978 96.4 5.8 19.5 2024 08 08 15 18.35 +12 01.4 9.973 9.991 88.1 5.8 19.5 2024 08 18 15 17.81 +11 09.1 10.133 10.003 79.8 5.7 19.5 2024 08 28 15 17.91 +10 16.4 10.290 10.016 71.5 5.5 19.6 2024 09 07 15 18.61 +09 24.3 10.441 10.029 63.3 5.2 19.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 March 2 (CBET 5362) Daniel W. E. Green