Electronic Telegram No. 5250 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/2010 OE_101 = P/2021 LJ_31 (WISE) An apparently asteroidal object discovered in infrared images obtained during 2010 July 25-26 (discovery observations tabulated below) with the Wide-field Infrared Survey Explorer (or WISE) earth-orbiting satellite (cf. IAUC 9118) and announced on MPEC 2010-P11, was found to show cometary appearance by CCD astrometrists in 2021 when it was again near perihelion in its 5.6-year orbit, after it was re-discovered independently at Mt. Lemmon on 2021 June 6 at mag 21.0-21.4, whence it was given the designation 2021 LJ_31 by the Minor Planet Center (cf. MPS 1446951) before it was linked by A. Doppler (cf. MPEC 2021-Q79, dated 2021 Aug. 29) to 2010 OE_101 (which notably had a fairly strong orbit from a five-month arc in 2010). The red discovery magnitude tabulated below was given based on previous correlations between WISE infrared observations and optical brightness measurements. Ground-based observations yielded mag 18-20 during Oct.-Dec. 2010. H. Sato (Tokyo, Japan) had noted that his CCD observations obtained with a 0.50-m f/6.8 reflector at Mayhill, NM, USA, on 2010 Oct. 7.3 UT showed a diameter of 5".1 (full-width-at-half-maximum) in 4".0 seeing, with the eastern side of the object's image appearing "soft" and a bit elongated; the total magnitude was then 19.6. 2010 UT R.A. (2000) Decl. Mag. July 25.02012 1 42 55.78 +25 00 49.2 19 25.15242 1 43 24.68 +25 01 24.4 25.28472 1 43 53.54 +25 01 59.5 25.41703 1 44 22.44 +25 02 33.7 25.54933 1 44 51.38 +25 03 07.2 25.68163 1 45 20.32 +25 03 40.3 25.81394 1 45 49.27 +25 04 13.1 25.94624 1 46 18.22 +25 04 45.1 26.07855 1 46 47.19 +25 05 16.8 26.21085 1 47 16.16 +25 05 48.0 K. Wierzchos, Lunar and Planetary Laboratory, University of Arizona, reported to the Minor Planet Center back in 2021 September that cometary images of 2010 OE_101 appeared in Mt. Lemmon 1.5-m reflector exposures taken on 2021 Sept. 6.36 UT showed a condensed coma of size 12" with a straight 27" tail in p.a. 215 degrees. When Wierzchos circulated his report to the cometary community, other CCD observers also then reported cometary activity to the Central Bureau and to the MPC. Eight stacked 60-s exposures taken remotely by Sato with a 0.43-m f/6.8 astrograph at Mayhill on 2021 Sept. 10.44 showed a strongly condensed coma 10" in diameter with a 15" tail toward p.a. 225 degrees; the magnitude was 17.4 as measured within a circular aperture of radius 6".3. Sato acquired ten additional stacked 60-s exposures on 2021 Oct. 2.4 with the same astrograph, showing a strongly condensed coma 10" in diameter with a 15" tail toward p.a. 220 degrees; the magnitude was 16.5 as measured within a circular aperture of radius 5".7. Seven 90-s unfiltered exposures obtained on 2021 Sept. 13.04-13.05 with a 0.4-m f/2.8 reflector by F. Kugel at Dauban, France, revealed a 24" tail in p.a. 225 degrees; the magnitude was given as 17.7-18.2. Thirty-nine stacked 60-s exposures taken by L. Buzzi (and measured by A. Aletti) with a 0.84-m f/3.5 reflector at Varese, Italy, on 2021 Sept. 13.94-13.96 show a stellar central condensation with a thin, straight tail 50" long in p.a. 214 degrees; the magnitude was measured as 17.5. K. Yoshimoto, Kumage, Yamaguchi, Japan, writes that images taken on 2021 Oct. 5.24 with a 0.43-m f/6.8 reflector show a very condensed coma 21" in diameter and of total mag 16.2 with a 20" tail in p.a. 240 deg. The available astrometry appears in unsorted form on MPEC 2023-H227. The following linked orbital elements by S. Nakano (Central Bureau) are from 736 observations spanning 2010-2022 (mean residual 0".3); these indicate no close approaches to major planets except to 0.69 AU from Jupiter in Oct. 1957. Epoch = 2005 Jan. 30.0 TT T = 2005 Feb. 8.07952 TT Peri. = 174.89436 e = 0.5716977 Node = 194.40747 2000.0 q = 1.3432585 AU Incl. = 18.42203 a = 3.1362394 AU n = 0.17745583 P = 5.55 years Epoch = 2010 Sept. 1.0 TT T = 2010 Aug. 26.66881 TT Peri. = 174.83018 e = 0.5726709 Node = 194.40130 2000.0 q = 1.3393277 AU Incl. = 18.44373 a = 3.1341831 AU n = 0.17763050 P = 5.55 years Epoch = 2016 Apr. 2.0 TT T = 2016 Mar. 15.67869 TT Peri. = 174.83096 e = 0.5711262 Node = 194.39665 2000.0 q = 1.3459397 AU Incl. = 18.41783 a = 3.1383122 AU n = 0.17728005 P = 5.56 years Epoch = 2021 Sept.23.0 TT T = 2021 Oct. 4.88726 TT Peri. = 174.73950 e = 0.5704994 Node = 194.38149 2000.0 q = 1.3490547 AU Incl. = 18.41150 a = 3.1409844 AU n = 0.17705386 P = 5.57 years Epoch = 2027 Apr. 25.0 TT T = 2027 May 3.13603 TT Peri. = 174.80728 e = 0.5692990 Node = 194.35871 2000.0 q = 1.3547555 AU Incl. = 18.39242 a = 3.1454660 AU n = 0.17667560 P = 5.58 years Epoch = 2032 Nov. 24.0 TT T = 2032 Dec. 4.35338 TT Peri. = 174.85047 e = 0.5653410 Node = 194.27138 2000.0 q = 1.3723359 AU Incl. = 18.34529 a = 3.1572703 AU n = 0.17568570 P = 5.61 years Epoch = 2038 Aug. 5.0 TT T = 2038 July 18.72204 TT Peri. = 174.94752 e = 0.5645785 Node = 194.22785 2000.0 q = 1.3761831 AU Incl. = 18.33531 a = 3.1605769 AU n = 0.17541007 P = 5.62 years 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 5250) Daniel W. E. Green