Electronic Telegram No. 5349 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/2024 A2 (ATLAS) An apparently asteroidal object discovered on CCD images taken on Jan. 15 UT with a 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program has been found to show cometary appearance by CCD astrometrists elsewhere after it was posted to the Minor Planet Center's PCCP webpage. The discovery observations are tabulated below: 2024 UT R.A. (2000) Decl. Mag. Jan. 15.33554 14 52 55.63 -65 17 49.7 18.0 15.34072 14 52 55.44 -65 17 59.6 18.0 15.36106 14 52 54.89 -65 18 36.2 17.8 15.36879 14 52 54.70 -65 18 49.4 17.8 Eight stacked 30-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) on Jan. 16.35 UT with a "Deep Sky Chile" 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile, show a strongly condensed round coma 5" in diameter with no tail; the magnitude was 18.1 as measured within a circular aperture of radius 2".8. Six stacked 60-s exposures taken remotely by Sato on Feb. 10.7 with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, show a strongly condensed coma 6" in diameter and no tail; the magnitude was 17.7 as measured within a circular aperture of radius 4".9. Exposures taken remotely on Feb. 9.75 by T. Prystavski (Lyiv, Ukraine) with a 0.43-m f/6.8 corrected Dall-Kirkham telescope at Siding Spring show a very condensed head of total mag 17.7 that is slightly elongated with a possible 0'.1 tail in p.a. 40 degrees. The available astrometry appears on MPEC 2024-C180. The following two- body orbital elements by S. Nakano (Central Bureau) are from 115 observations spanning 2024 Jan. 15-Feb. 14 (mean residual 0".4). They indicate no close approaches to major planets; the orbital period has a formal error of +/- 2.1 years. T = 2024 Apr. 28.87857 TT Peri. = 295.56302 e = 0.9421865 Node = 78.16308 2000.0 q = 1.8818119 AU Incl. = 119.10889 a = 32.5497004 AU n = 0.00530742 P = 185.7 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 01 11 14 54.14 -63 12.8 2.603 2.287 60.6 22.0 18.0 2024 01 16 14 52.62 -65 37.8 2.503 2.255 64.2 23.1 17.8 2024 01 21 14 48.99 -68 15.6 2.402 2.223 67.7 24.2 17.7 2024 01 26 14 41.99 -71 06.6 2.304 2.193 71.1 25.1 17.5 2024 01 31 14 29.17 -74 10.0 2.208 2.164 74.5 26.0 17.4 2024 02 05 14 05.23 -77 22.1 2.116 2.135 77.7 26.8 17.3 2024 02 10 13 17.59 -80 30.0 2.030 2.108 80.7 27.5 17.1 2024 02 15 11 39.22 -82 51.2 1.951 2.082 83.3 28.1 17.0 2024 02 20 09 09.76 -82 50.1 1.881 2.057 85.6 28.6 16.9 2024 02 25 07 20.74 -79 57.3 1.822 2.034 87.4 29.1 16.8 2024 03 01 06 27.18 -75 32.7 1.776 2.012 88.6 29.5 16.7 2024 03 06 06 00.55 -70 26.1 1.743 1.992 89.1 29.9 16.6 2024 03 11 05 46.40 -64 58.8 1.725 1.973 88.8 30.2 16.5 2024 03 16 05 38.70 -59 23.0 1.722 1.956 87.8 30.5 16.5 2024 03 21 05 34.66 -53 48.0 1.733 1.940 86.1 30.8 16.5 2024 03 26 05 32.88 -48 21.1 1.759 1.926 83.8 31.0 16.5 2024 03 31 05 32.58 -43 07.9 1.797 1.914 81.0 31.0 16.5 2024 04 05 05 33.30 -38 12.6 1.847 1.904 77.7 30.9 16.6 2024 04 10 05 34.74 -33 37.5 1.906 1.896 74.2 30.6 16.6 2024 04 15 05 36.72 -29 23.8 1.972 1.889 70.4 30.0 16.7 2024 04 20 05 39.09 -25 31.3 2.045 1.885 66.5 29.3 16.8 2024 04 25 05 41.74 -21 59.0 2.121 1.882 62.5 28.3 16.8 2024 04 30 05 44.62 -18 45.8 2.200 1.882 58.5 27.2 16.9 2024 05 05 05 47.68 -15 50.0 2.280 1.883 54.5 25.9 17.0 2024 05 10 05 50.86 -13 09.9 2.359 1.887 50.6 24.4 17.1 2024 05 15 05 54.15 -10 44.1 2.437 1.892 46.6 22.9 17.1 2024 05 20 05 57.50 -08 31.0 2.513 1.899 42.8 21.2 17.2 2024 05 25 06 00.90 -06 29.1 2.586 1.908 39.0 19.5 17.3 2024 05 30 06 04.32 -04 37.2 2.654 1.919 35.4 17.8 17.4 2024 08 18 06 50.33 +13 58.9 2.926 2.302 43.6 17.7 18.2 2024 08 28 06 52.62 +15 54.2 2.846 2.370 52.4 19.8 18.3 2024 09 07 06 53.26 +17 56.9 2.747 2.440 61.9 21.4 18.3 2024 09 17 06 51.75 +20 11.0 2.633 2.513 72.1 22.4 18.3 2024 09 27 06 47.48 +22 40.2 2.510 2.589 83.1 22.6 18.3 2024 10 07 06 39.68 +25 27.0 2.387 2.666 94.9 21.9 18.3 2024 10 17 06 27.42 +28 31.3 2.273 2.745 107.6 20.2 18.3 2024 10 27 06 09.82 +31 47.6 2.178 2.825 121.2 17.5 18.3 2024 11 06 05 46.26 +35 02.7 2.115 2.906 135.4 13.9 18.3 2024 11 16 05 17.12 +37 56.0 2.096 2.988 149.0 9.8 18.4 2024 11 26 04 44.27 +40 05.6 2.127 3.070 159.3 6.5 18.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 February 15 (CBET 5349) Daniel W. E. Green