Electronic Telegram No. 5153 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/2019 G4 (PANSTARRS) An apparently asteroidal object that was originally discovered in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala, Hawaii, on 2019 Apr. 9 (and given the designation A/2019 G4 on MPEC 2019-H32, based on the highly elliptical orbit), has been found by S. Deen (Simi Valley, CA, USA) to show cometary appearance in publicly available DECam CCD images taken on 2018 July 24.97 UT with the 4-m Cerro Tololo reflector; in CCD images taken by K. J. Meech (University of Hawaii) with the 3.6-m Canada- France-Hawaii Telescope at Mauna Kea on 2019 Oct. 24 and 27 (magnitude 22-23) and on 2020 Jan. 30 (mag 22.2-22.4), Feb. 26 (mag 22.6-22.7), May 21 (mag 24.2), and Nov. 11 (mag 23.7-24.0); and in images taken by Meech on 2019 Dec. 28 and on 2020 Feb. 1 with the 8.1-m "Gemini North" telescope at Mauna Kea. The discovery observations are tabulated below. 2019 UT R.A. (2000) Decl. Mag. Apr. 9.24593 10 17 02.37 -29 14 36.6 21.4 9.25625 10 17 01.88 -29 14 28.7 21.3 9.26658 10 17 01.38 -29 14 21.1 21.5 Deen notes that the DECam images are poor (but the comet seems to be "somewhat hazy" with no clear tail), but has provided the CFHT images showing clear cometary activity -- showing a very condensed coma with a small but definite coma and a broad, diffuse dust tail. CFHT images on 2019 Oct. 24.6 UT show a slightly condensed 2" coma and a 5"-long tail in p.a. 150 degrees, while 2019 Oct. 27.6 images show a condensed 2" coma and a 5"-long tail in p.a. 140 degrees. The CFHT images from 2019 Nov. 29.64 show a slightly condensed 2" coma and no obvious tail. The CFHT images from 2020 Jan. 30.5 show a slightly diffuse 1".5 coma and a broad 7"-long tail in p.a. 140 degrees. Meech adds that the 2019 Oct. 24 images were obtained in poor seeing and at high airmass, but that other images show the comet to be active (including especially the 2020 Jan. 30 images). Deen reports that the "Gemini North" images on 2019 Dec. 28 show a slightly diffuse coma of size 2" with a broad tail 5" long in p.a. 130 deg, while those on 2020 Feb. 1 show a 2".5 coma and a tail 6" long in p.a. 140 deg. The following new astrometry by Deen was not included on MPEC 2022-P69. 2019 UT R.A. (2000) Decl. Mag. Observer Nov. 29.63507 10 32 13.59 -13 05 05.2 21.6 Meech 29.63764 10 32 13.56 -13 05 05.1 21.7 " Dec. 28.59503 10 21 54.97 -12 19 09.4 21.7 " 28.60035 10 21 54.80 -12 19 08.6 21.7 " 2020 UT R.A. (2000) Decl. Mag. Observer Feb. 1.42029 9 58 21.47 - 9 39 08.0 21.4 Meech 1.42681 9 58 21.18 - 9 39 05.5 21.3 " 1.43337 9 58 20.85 - 9 39 02.9 21.4 " The following orbital elements by S. Nakano (Central Bureau) are from 38 observations spanning 2018 July 24-2020 Nov. 11 (mean residual 0".3), with corresponding "original" and "future" values of 1/a (with respect to the solar-system barycenter) being +0.000084 and +0.000170 AU**-1 (+/- 0.000001 AU**-1), respectively. The comet passed 6.94 AU from Neptune on 2006 Apr. 28 UT. Epoch = 2018 Aug. 30.0 TT T = 2018 Sept.15.16175 TT Peri. = 287.83453 e = 0.9996351 Node = 130.47576 2000.0 q = 5.8580177 AU Incl. = 138.37557 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 August 6 (CBET 5153) Daniel W. E. Green