Electronic Telegram No. 5064 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 U3 (ATTARD-MAURY) Alain Maury reports that Georges Attard (Mougins, France) and he have discovered another comet on images obtained on Oct. 24 (discovery astrometry tabulated below), with the object described as appearing "fuzzy" on images obtained with a 40-cm reflector at San Pedro de Atacama, Chile. The comet was spread over about five pixels, whereas nearby stars of similar brightness were spread over 3 pixels; their deepest images show a small, 6" tail in p.a. about 270 degrees. 2021 UT R.A. (2000) Decl. Mag. Observer Oct. 24.31345 6 26 47.39 -11 28 40.7 19.2 Attard 24.31935 6 26 47.06 -11 28 34.9 19.2 " 24.32513 6 26 46.73 -11 28 28.5 19.3 " After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists have reported cometary appearance to the Central Bureau. E. Guido, Castellammare di Stabia, Italy, writes that fifty-one stacked, unfiltered 60-s exposures obtained remotely by a large group of observers with a "Telescope Live" 0.61-m f/6.5 astrograph located at El Sauce, Chile, on Oct. 27.3 UT show a compact coma about 6" arcsecond in diameter and a tail 6" long in p.a. 275 degrees (the magnitude given as 18.5-19.2). Sixty stacked 60-s unfiltered exposures taken on Oct. 28.12-28.18 by E. Bryssinck, Kruibeke, Belgium, with a 0.4-m f/3.8 reflector show a central condensation with an 8" coma and a short tail about 8" long in p.a. 270 degrees; the magnitude was 18.5 as measured in an aperture of radius 5".6. L. Buzzi, Varese, Italy, writes that two-hundred-forty stacked 30-s exposures taken by A. Aletti on Oct. 29.05-29.10 with a 0.20-m f/4 reflector in good conditions but moonlight show a moderately condensed 5" coma (in 4" seeing), elongated for 6" in p.a. 90 degrees. One-hundred-twenty 60-s unfiltered exposures taken on Oct. 29.11-29.16 by J.-F. Soulier, Maisoncelles, France, with a 0.30-m f/3.8 Newtonian reflector show a coma of size about 15" and a tail about 20" long in p.a. about 270 degrees; the red magnitude was 18.7 in an aperture of radius 6".5. Sixteen stacked 60-s exposures taken remotely by H. Sato, Tokyo, Japan, on Oct. 29.5 using a 0.43-m f/6.8 astrograph located near Mayhill, NM, USA, show a strongly condensed coma 8" in diameter with a 6" tail toward p.a. 270 degrees; the magnitude was 18.6 as measured within a circular aperture. A. Valvasori, Padulle, Italy, notes that sixty-six stacked 60-s unfiltered exposures taken by E. Guido and himself on Oct. 29.9 with a 0.30-m f/4 reflector show a compact coma about 5" in diameter (and magnitude 17.4-17.8) and a tail 6" long in p.a. 270 degrees. The available astrometry appears on MPEC 2021-V21. The following preliminary elliptical orbital elements by S. Nakano (CBAT) are from 90 observations spanning 2021 Oct. 24-Nov. 1 (mean residual 0".4); they suggest that the comet passed 0.59 AU from Jupiter in 1983 October (though the orbital period is uncertain by well over a month). A search for earlier observations in archival astrometry produced nothing. T = 2021 Oct. 25.61312 TT Peri. = 335.56671 e = 0.5547090 Node = 75.09663 2000.0 q = 1.8891204 AU Incl. = 70.09281 a = 4.2424401 AU n = 0.11279257 P = 8.74 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.5 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2021 09 23 06 30.45 -17 33.5 1.762 1.913 82.7 31.3 18.5 2021 09 28 06 32.32 -16 51.0 1.695 1.907 85.9 31.6 18.4 2021 10 03 06 33.40 -16 04.8 1.625 1.901 89.5 31.8 18.3 2021 10 08 06 33.61 -15 13.5 1.554 1.896 93.4 31.7 18.2 2021 10 13 06 32.83 -14 15.5 1.482 1.893 97.6 31.5 18.1 2021 10 18 06 30.95 -13 08.8 1.410 1.890 102.2 31.0 18.0 2021 10 23 06 27.83 -11 51.2 1.339 1.889 107.2 30.2 17.9 2021 10 28 06 23.33 -10 20.3 1.269 1.889 112.7 29.0 17.8 2021 11 02 06 17.28 -08 33.2 1.202 1.890 118.7 27.4 17.7 2021 11 07 06 09.55 -06 27.1 1.139 1.893 125.3 25.3 17.6 2021 11 12 06 00.02 -03 59.2 1.081 1.896 132.5 22.7 17.4 2021 11 17 05 48.64 -01 08.0 1.032 1.901 140.2 19.4 17.4 2021 11 22 05 35.45 +02 06.4 0.993 1.906 148.5 15.7 17.3 2021 11 27 05 20.63 +05 41.1 0.965 1.913 157.1 11.6 17.2 2021 12 02 05 04.48 +09 30.1 0.951 1.921 165.4 7.4 17.2 2021 12 07 04 47.50 +13 24.7 0.951 1.930 170.7 4.7 17.2 2021 12 12 04 30.29 +17 15.1 0.966 1.940 167.8 6.1 17.3 2021 12 17 04 13.49 +20 52.3 0.996 1.951 160.3 9.8 17.4 2021 12 22 03 57.67 +24 10.1 1.039 1.963 152.0 13.6 17.5 2021 12 27 03 43.28 +27 05.6 1.093 1.975 144.0 17.0 17.7 2022 01 01 03 30.62 +29 39.1 1.158 1.989 136.4 19.9 17.8 2022 01 06 03 19.85 +31 52.5 1.231 2.004 129.3 22.3 18.0 2022 01 11 03 11.00 +33 48.7 1.310 2.019 122.8 24.2 18.1 2022 01 16 03 03.99 +35 31.1 1.394 2.036 116.7 25.6 18.3 2022 01 21 02 58.70 +37 02.3 1.482 2.053 111.1 26.6 18.5 2022 01 26 02 54.98 +38 25.0 1.572 2.071 105.9 27.2 18.6 2022 01 31 02 52.70 +39 41.0 1.664 2.090 101.1 27.6 18.8 2022 02 05 02 51.70 +40 52.0 1.756 2.109 96.5 27.7 19.0 2022 02 10 02 51.87 +41 59.4 1.849 2.129 92.2 27.6 19.1 2022 02 15 02 53.08 +43 04.1 1.941 2.149 88.2 27.3 19.3 2022 02 20 02 55.22 +44 06.6 2.032 2.171 84.4 27.0 19.4 2022 02 25 02 58.22 +45 07.6 2.122 2.192 80.8 26.5 19.5 2022 03 02 03 02.01 +46 07.5 2.210 2.215 77.3 25.9 19.7 2022 03 07 03 06.54 +47 06.6 2.296 2.237 74.1 25.2 19.8 2022 03 12 03 11.74 +48 05.0 2.380 2.261 71.0 24.6 19.9 2022 03 17 03 17.59 +49 02.9 2.461 2.284 68.1 23.8 20.0 2022 03 22 03 24.05 +50 00.3 2.540 2.308 65.3 23.1 20.2 2022 03 27 03 31.10 +50 57.3 2.616 2.333 62.7 22.3 20.3 2022 04 01 03 38.73 +51 53.7 2.689 2.358 60.2 21.6 20.4 2022 04 06 03 46.94 +52 49.7 2.760 2.383 57.8 20.8 20.5 2022 04 11 03 55.72 +53 45.2 2.827 2.408 55.7 20.1 20.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2021 CBAT 2021 November 2 (CBET 5064) Daniel W. E. Green