Electronic Telegram No. 2930 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; 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/2011 W3 (LOVEJOY) Terry Lovejoy, Thornlands, Qld., Australia, reports his discovery of a comet on three CCD images obtained each on Nov. 27.7 and 29.7 UT with a Celestron 8 0.20-m f/2.1 Schmidt-Cassegrain reflector (+ QHY9 camera) in the course of his normal comet-search program; the comet appears as a clearly diffuse circular object approximately 1' in diameter, with a central condensation of mag 16 and no apparent tail. Clouds affected his observations on Nov. 29, and the astrometry was severely affected by a crowded star field (Lovejoy estimating uncertainty as much as +/- 15" or more). By Dec. 1.7, Lovejoy found that the comet had brightened by perhaps a magnitude and was now well-condensed with a 1'.2 coma. Astrometric measurements of his CCD frames (those on Nov. 27 and 29 by Lovejoy, those on Dec. 1 by G. V. Williams): 2011 UT R.A. (2000) Decl. Mag. Observer Nov. 27.73470 12 47 38.8 -51 39 29 13 Lovejoy 27.74030 12 47 45.6 -51 39 33 " 27.74650 12 47 51.8 -51 39 50 " 29.72801 13 27 30.5 -52 18 25 13 " 29.72861 13 27 30.5 -52 18 24 " 29.72907 13 27 31.2 -52 18 27 " 29.72953 13 27 31.8 -52 18 30 " Dec. 1.73183 14 09 33.9 -52 00 41 12 " 1.73229 14 09 34.4 -52 00 44 " 1.73274 14 09 34.7 -52 00 44 " A. C. Gilmore and P. M. Kilmartin report that their CCD images obtained on Dec. 1.6 with the Mount John 1.0-m f/7.7 reflector show a well-condensed, circular coma of diameter approximately 1' (and a nuclear condensation of mag 16.6-17.3) with no tail visible in a 60-s exposure. After the comet was posted on the Minor Planet Center's NEOCP webpage, R. Holmes (Ashmore, IL, USA) writes that stacked CCD observations obtained by Holmes, T. Linder, and V. Hoette with a 0.41-m f/11 Ritchey-Chretien reflector at Cerro Tololo on Dec. 2.3 show a 14" round coma with a very broad 51".3 tail extending predominately in p.a. 327 deg. T. Lister (Goleta, CA, U.S.A.) finds a diffuse coma of diameter about 13" with very little central condensation on CCD images obtained with the 2.0-m f/10 "Faulkes Telescope South" at Siding Spring on Dec. 2.75. The available astrometry and the following preliminary parabolic orbital elements by G. V. Williams appear on MPEC 2011-X16. T = 2011 Dec. 16.0000 TT Peri. = 57.1427 Node = 332.0232 2000.0 q = 0.005894 AU Incl. = 135.9356 The comet appears to be a Kreutz sungrazer. The following ephemeris assumes H = 14.0 and 2.5n = 8. Note that the rate of brightness increase is highly uncertain. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2011 11 25 12 01.69 -49 43.4 0.762 0.832 55.0 76.4 13.3 2011 11 26 12 17.70 -50 33.2 0.748 0.805 53.1 78.9 13.1 2011 11 27 12 34.93 -51 15.5 0.735 0.778 51.2 81.4 13.0 2011 11 28 12 53.34 -51 48.6 0.724 0.750 49.1 84.0 12.8 2011 11 29 13 12.80 -52 10.5 0.715 0.722 46.9 86.7 12.6 2011 11 30 13 33.12 -52 19.6 0.708 0.693 44.6 89.5 12.5 2011 12 01 13 54.03 -52 14.4 0.702 0.663 42.2 92.4 12.3 2011 12 02 14 15.22 -51 53.7 0.699 0.633 39.8 95.4 12.1 2011 12 03 14 36.33 -51 17.0 0.697 0.603 37.2 98.4 12.0 2011 12 04 14 57.02 -50 24.3 0.698 0.571 34.6 101.4 11.8 2011 12 05 15 16.98 -49 16.2 0.702 0.538 31.9 104.5 11.6 2011 12 06 15 35.96 -47 53.6 0.708 0.505 29.3 107.5 11.4 2011 12 07 15 53.78 -46 18.1 0.716 0.470 26.5 110.6 11.2 2011 12 08 16 10.34 -44 31.1 0.727 0.434 23.8 113.6 10.9 2011 12 09 16 25.59 -42 34.2 0.742 0.397 21.1 116.5 10.6 2011 12 10 16 39.54 -40 28.8 0.759 0.358 18.5 119.4 10.3 2011 12 11 16 52.22 -38 15.8 0.780 0.316 15.8 122.1 10.0 2011 12 12 17 03.68 -35 55.6 0.804 0.272 13.1 124.7 9.5 2011 12 13 17 13.96 -33 27.7 0.833 0.223 10.4 127.2 8.9 2011 12 14 17 23.07 -30 48.9 0.869 0.169 7.7 129.2 8.0 2011 12 15 17 30.86 -27 50.3 0.914 0.105 4.7 130.0 6.5 2011 12 16 17 32.18 -23 05.4 0.989 0.006 0.2 40.6 -3.4 2011 12 17 17 16.52 -25 17.7 0.919 0.104 4.9 126.5 6.4 2011 12 18 17 10.86 -27 27.6 0.873 0.169 7.8 127.2 8.0 2011 12 19 17 06.90 -29 31.8 0.835 0.223 10.5 126.5 8.9 2011 12 20 17 03.78 -31 35.1 0.802 0.271 13.0 125.4 9.5 2011 12 21 17 01.19 -33 39.8 0.771 0.316 15.4 124.1 9.9 2011 12 22 16 58.98 -35 47.1 0.744 0.357 17.8 122.7 10.3 2011 12 23 16 57.06 -37 57.9 0.718 0.397 20.2 121.1 10.6 2011 12 24 16 55.36 -40 13.0 0.694 0.434 22.6 119.5 10.8 2011 12 25 16 53.85 -42 32.9 0.672 0.470 25.0 117.8 11.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 December 2 (CBET 2930) Daniel W. E. Green