Electronic Telegram No. 5251 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/2022 BV_9 (LEMMON) An apparently asteroidal object discovered on images obtained with the 1.5-m reflector at Mt. Lemmon on 2022 Jan. 30 (discovery observations from MPS 1551765 tabulated below) has been found to show cometary appearance in images obtained by CCD astrometrists elsewhere after it was posted to the Minor Planet Center's PCCP webpage. 2022 UT R.A. (2000) Decl. Mag. Jan. 30.12885 3 09 56.65 +31 21 57.7 20.5 30.13448 3 09 56.80 +31 21 57.4 20.5 30.14012 3 09 56.93 +31 21 56.6 20.2 30.14574 3 09 57.07 +31 21 56.1 20.4 Four unlinked sets of single-night apparently asteroidal pre-discovery observations from 2021 Feb. 6-11 (at mag 19.4-20.0) that were obtained with the Palomar 1.2-m Schmidt telescope and were present in the MPC's "isolated tracklet file" were later identified with 2022 BV_9. R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the suggestion by P. VanWylen (on the "Comets Mailing List" forum on Apr. 1, in which VanWylen noted the comet's absence from 2010-2014 archives even though it has a well-constrained orbit), after which Weryk looked through the Pan-STARRS image archive and was able to find clear cometary activity. Four 45-s w-band survey images obtained on 2022 Dec. 15.6 UT with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala show a diffuse coma of size about 3" (full-width-at-half-maximum) and mag 20.9-21.0 in 1".1 seeing with a broad tail about 5" long spanning p.a. 250-300 degrees. Four 45-s w-band survey images taken on 2023 Jan. 14.33-14.36 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala show a diffuse coma of size about 4" (FWHM) and mag 20.6-20.9 in 1".3 seeing, with a broad tail about 7" long spanning p.a. 245-315 deg. Similar images obtained with the Pan-STARRS2 telescope on 2023 Jan. 24.32-24.36 show a diffuse coma of size about 4" (FWHM) and mag mag 20.3-20.9 in 1".9 seeing, with a broad tail about 7" long spanning p.a. 250-305 deg. Nine stacked 120-s exposures taken remotely on 2023 Apr. 11.14-11.15 UT by Hidetaka Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph show a moderately condensed and elongated coma of size 8" x 10" with no tail; the magnitude was 19.6 as measured within a circular aperture of radius 6".5. Also following the suggestion by VanWylen, M. S. P. Kelley (University of Maryland) and Q.-z. Ye write that the "Zwicky Transient Facility" (ZTF) data archive was searched for observations obtained with the 1.2-m Samuel Oschin Schmidt telescope at Palomar. After correcting for heliocentric and geocentric distance, the reduced magnitudes show strong variations with time. Selected reduced r-band photometry within 5" radius apertures: 2020 Oct. 23, >/= 16.1 on 2020 Oct 23; 2021 Feb. 5, 13.8; 2021 Nov. 7, >/= 15.7; 2022 Feb. 19, 14.4; 2022 Apr. 18, 13.0; 2022 Aug. 10, 12.5; 2023 Jan. 25, 13.2. The 2020 Oct. 23 observation coincides with the object's perihelion date, and the heliocentric distance increased over the time period from 3.33 to 3.65 AU. Based on initial analysis by Kelley et al., a tail is first evident in an average of 35 images taken between 2022 Aug. 14 and 20. The tail position angles (+/- 10 deg) are within 20 degrees of the projected anti-velocity vector but disagree with the anti-sun vector by up to 140 deg. The disagreement with the anti-sun vector suggests a paucity of micrometer and sub-micrometer grains in the tail starting around 2022 December. The available astrometry appears on MPEC 2023-H240. The following orbital elements by S. Nakano (Central Bureau) are from 98 observations spanning 2021 Feb. 6-2023 Apr. 11 (mean residual 0".6). The comet passed 0.45 AU from Jupiter on 2016 Jan. 18 UT. Epoch = 2002 Oct. 13.0 TT T = 2002 Oct. 20.50428 TT Peri. = 73.38914 e = 0.1107492 Node = 1.05265 2000.0 q = 3.9915121 AU Incl. = 14.42155 a = 4.4886238 AU n = 0.10364164 P = 9.51 years Epoch = 2020 Nov. 7.0 TT T = 2020 Oct. 22.78897 TT Peri. = 15.96186 e = 0.2352810 Node = 337.29074 2000.0 q = 3.3328512 AU Incl. = 11.93459 a = 4.3582691 AU n = 0.10832608 P = 9.10 years Epoch = 2029 Dec. 10.0 TT T = 2029 Dec. 4.09896 TT Peri. = 15.94423 e = 0.2337429 Node = 337.30177 2000.0 q = 3.3521504 AU Incl. = 11.91799 a = 4.3747071 AU n = 0.10771609 P = 9.15 years Epoch = 2039 Feb. 21.0 TT T = 2039 Feb. 4.79946 TT Peri. = 16.15019 e = 0.2338751 Node = 337.16575 2000.0 q = 3.3543008 AU Incl. = 11.91542 a = 4.3782686 AU n = 0.10758469 P = 9.16 years Epoch = 2048 Mar. 25.0 TT T = 2048 Mar. 22.42255 TT Peri. = 16.20206 e = 0.2351634 Node = 337.11559 2000.0 q = 3.3327220 AU Incl. = 11.93029 a = 4.3574302 AU n = 0.10835736 P = 9.10 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 04 06 07 02.52 +30 47.1 4.630 4.702 87.9 12.3 20.7 2023 04 16 07 07.46 +30 15.8 4.800 4.719 79.3 12.1 20.8 2023 04 26 07 13.53 +29 44.0 4.966 4.735 71.0 11.6 20.9 2023 05 06 07 20.55 +29 11.5 5.125 4.752 62.9 10.9 21.0 2023 05 16 07 28.36 +28 38.2 5.274 4.768 55.1 10.0 21.0 2023 05 26 07 36.80 +28 03.8 5.410 4.784 47.5 9.0 21.1 2023 06 05 07 45.73 +27 28.1 5.533 4.800 40.0 7.8 21.2 2023 09 23 09 28.26 +19 58.0 5.669 4.963 41.6 7.7 21.3 2023 10 03 09 35.80 +19 20.1 5.569 4.977 49.4 8.8 21.3 2023 10 13 09 42.67 +18 44.9 5.455 4.990 57.5 9.7 21.3 2023 10 23 09 48.76 +18 13.4 5.327 5.003 65.9 10.5 21.2 2023 11 02 09 53.97 +17 46.3 5.190 5.016 74.5 11.0 21.2 2023 11 12 09 58.17 +17 24.2 5.046 5.029 83.4 11.3 21.1 2023 11 22 10 01.25 +17 08.0 4.898 5.042 92.7 11.3 21.1 2023 12 02 10 03.08 +16 58.0 4.752 5.054 102.3 11.0 21.0 2023 12 12 10 03.59 +16 54.7 4.611 5.066 112.3 10.4 21.0 2023 12 22 10 02.71 +16 57.9 4.480 5.078 122.6 9.4 20.9 2024 01 01 10 00.44 +17 07.3 4.365 5.090 133.3 8.1 20.9 2024 01 11 09 56.87 +17 21.8 4.271 5.102 144.3 6.5 20.8 2024 01 21 09 52.15 +17 40.0 4.201 5.113 155.5 4.6 20.8 2024 01 31 09 46.59 +17 59.9 4.160 5.124 166.7 2.5 20.8 2024 02 10 09 40.52 +18 19.5 4.150 5.135 175.7 0.8 20.8 2024 02 20 09 34.39 +18 36.7 4.173 5.146 168.7 2.2 20.8 2024 03 01 09 28.61 +18 50.0 4.226 5.156 157.6 4.2 20.8 2024 03 11 09 23.56 +18 58.0 4.308 5.166 146.6 6.1 20.9 2024 03 21 09 19.55 +19 00.3 4.415 5.176 135.8 7.7 20.9 2024 03 31 09 16.78 +18 56.6 4.544 5.186 125.3 9.0 21.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 April 29 (CBET 5251) Daniel W. E. Green