Electronic Telegram No. 5006 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/2021 O2 = P/2005 W3 (KOWALSKI) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the accidental recovery (identified by the Minor Planet Center) of comet P/2005 W3 (cf. IAUCs 8634, 8641) in images obtained on 2021 July 20 with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala, Hawaii; four 45-s w-band survey images taken in 1".3 seeing show a very condensed coma of size 1".7 (full-width-at-half-maximum) with a broad tail 8" long spanning p.a. 250-270 degrees. The astrometry is tabulated below. 2021 UT R.A. (2000) Decl. Mag. July 20.59892 3 26 07.23 +17 18 18.7 20.4 20.60293 3 26 07.59 +17 18 18.9 20.2 20.60692 3 26 07.92 +17 18 19.3 20.4 20.61091 3 26 08.27 +17 18 19.7 20.3 Weryk adds that he subsequently identified the comet in Pan-STARRS1 images from 2020 Aug. 19 that were in the Minor Planet Center's "isolated tracklet file", together with newly found Pan-STARRS1 observations from 2020 Sept. 6 and Dec. 6, and Pan-STARRS2 observations from 2020 Sept. 14, Oct. 6, and Nov. 8; due to the faintness of the comet in 2020, he was unable to discern if any cometary activity was present. The astrometry is tabulated below. 2020 UT R.A. (2000) Decl. Mag. Aug. 19.47367 22 05 59.28 + 7 49 40.5 22.8 19.48272 22 05 58.97 + 7 49 38.5 23.0 19.49174 22 05 58.68 + 7 49 36.6 22.6 19.50078 22 05 58.39 + 7 49 34.5 22.8 Sept. 6.26456 21 56 30.26 + 6 27 43.9 23.6 6.27634 21 56 29.87 + 6 27 40.3 22.8 14.30064 21 52 38.14 + 5 41 21.7 21.8 14.31154 21 52 37.86 + 5 41 17.4 22.3 14.32253 21 52 37.59 + 5 41 13.1 22.9 Oct. 6.25323 21 45 44.46 + 3 24 57.6 22.6 6.26556 21 45 44.35 + 3 24 53.6 22.2 Nov. 8.24405 21 49 58.35 + 0 41 39.7 22.9 8.25629 21 49 58.64 + 0 41 37.1 21.7 Dec. 6.23310 22 07 31.09 - 0 10 41.4 21.9 6.25642 22 07 32.21 - 0 10 41.9 22.6 The residuals for the recovery observations on 2021 July 20 are +12'.6 in R.A. and -0'.3 in Decl. from the prediction in NK 1348 and the ICQ's 2020 and 2021 Comet Handbooks, with a corresponding Delta-T correction of -0.97 day. The residuals for the 2020 observations were around +9'.2 in R.A. and +2'.5 in Decl. The following linked orbital elements by S. Nakano (CBAT) are from 127 observations spanning 2005-2021 (mean residual 0".6). The comet passed 1.13 AU from Saturn on 2014 July 27 UT. Nakano was unable to find any additional observations of the comet in astrometric archives. Epoch = 2005 Aug. 18.0 TT T = 2005 Aug. 23.04816 TT Peri. = 199.23472 e = 0.5304873 Node = 211.56586 2000.0 q = 3.0084320 AU Incl. = 16.77815 a = 6.4075624 AU n = 0.06076658 P = 16.22 years Epoch = 2021 Sept.23.0 TT T = 2021 Sept.20.39823 TT Peri. = 200.72890 e = 0.5433432 Node = 210.08838 2000.0 q = 2.8900856 AU Incl. = 16.42138 a = 6.3287911 AU n = 0.06190460 P = 15.92 years Epoch = 2037 Sept.19.0 TT T = 2037 Sept.11.47561 TT Peri. = 200.88085 e = 0.5440238 Node = 210.12235 2000.0 q = 2.8952715 AU Incl. = 16.39010 a = 6.3496106 AU n = 0.06160039 P = 16.00 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.5 and 2.5n = 10 for the magnitude parameters, from the 2005 apparition (even though the 2020 and 2021 Pan-STARRS astrmetric magnitudes are 1.5-2 mag fainter). Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2021 07 05 03 02.98 +16 49.3 3.413 2.947 54.8 16.4 18.9 2021 07 15 03 17.96 +17 10.6 3.291 2.933 60.8 17.6 18.8 2021 07 25 03 32.40 +17 22.3 3.165 2.922 67.0 18.7 18.7 2021 08 04 03 46.15 +17 24.0 3.035 2.912 73.4 19.5 18.6 2021 08 14 03 59.00 +17 15.1 2.903 2.904 80.0 20.1 18.4 2021 08 24 04 10.75 +16 55.4 2.771 2.897 86.9 20.4 18.3 2021 09 03 04 21.17 +16 24.6 2.639 2.893 94.1 20.4 18.2 2021 09 13 04 29.99 +15 42.8 2.512 2.891 101.8 19.9 18.1 2021 09 23 04 36.97 +14 50.3 2.390 2.890 109.9 19.1 18.0 2021 10 03 04 41.89 +13 47.9 2.277 2.892 118.5 17.7 17.9 2021 10 13 04 44.55 +12 36.9 2.176 2.895 127.6 15.8 17.8 2021 10 23 04 44.91 +11 19.7 2.091 2.900 137.1 13.5 17.7 2021 11 02 04 43.07 +09 59.2 2.026 2.907 146.8 10.8 17.7 2021 11 12 04 39.32 +08 39.8 1.984 2.917 156.1 7.9 17.6 2021 11 22 04 34.25 +07 26.2 1.967 2.927 163.4 5.5 17.6 2021 12 02 04 28.58 +06 23.3 1.978 2.940 164.5 5.2 17.7 2021 12 12 04 23.10 +05 35.1 2.017 2.955 158.4 7.1 17.7 2021 12 22 04 18.60 +05 03.8 2.082 2.971 149.4 9.7 17.8 2022 01 01 04 15.65 +04 49.6 2.170 2.989 139.7 12.3 17.9 2022 01 11 04 14.60 +04 51.3 2.278 3.008 130.2 14.5 18.1 2022 01 21 04 15.62 +05 06.2 2.404 3.029 120.9 16.2 18.2 2022 01 31 04 18.67 +05 31.4 2.542 3.052 112.1 17.4 18.4 2022 02 10 04 23.64 +06 03.8 2.689 3.076 103.7 18.2 18.5 2022 02 20 04 30.34 +06 40.6 2.843 3.101 95.7 18.5 18.7 2022 03 02 04 38.56 +07 19.3 3.000 3.128 88.1 18.5 18.8 2022 03 12 04 48.10 +07 57.7 3.158 3.156 80.8 18.1 19.0 2022 03 22 04 58.75 +08 34.2 3.316 3.186 73.9 17.5 19.1 2022 04 01 05 10.32 +09 07.2 3.470 3.216 67.1 16.6 19.3 2022 04 11 05 22.66 +09 35.7 3.619 3.248 60.7 15.6 19.4 2022 04 21 05 35.60 +09 58.7 3.762 3.280 54.4 14.4 19.5 2022 05 01 05 49.01 +10 15.6 3.898 3.314 48.3 13.1 19.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2021 CBAT 2021 July 30 (CBET 5006) Daniel W. E. Green