Electronic Telegram No. 5633 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/2025 S4 = P/2015 TO_19 (LEMMON-PANSTARRS) Comet P/2015 TO_19 (cf. CBET 4151) has been recovered on CCD images obtained by John Maikner (New Ringgold, PA, USA, 0.3-m f/6.8 reflector) following a search for it; he reported Oct. 17 observations to the Minor Planet Center's NEOCP under a new-object preliminary designation when a search of the MPC database did not show it to be P/2015 TO_19. The MPC then informed him that they identified it as P/2015 TO_19, and the MPC listed it on Oct. 17 at their "Previous NEO Confirmation Page Objects" webpage. According to M. Rudenko, other observations published on MPEC 2025-V39 were then reported to the MPC under the designation "2015 TO_19" except for those by Vivian F. Carvajal (Mt. Lemmon Survey 1.5-m reflector) on Oct. 26 (independent accidental recovery). Maikner subsequently identified pre-recovery observations from images that he had obtained on Sept. 19 (when searching for P/2015 TO_19), reporting them to the MPC on Oct. 18. Maikner's recovery astrometry is tabulated below. Upon closer examination, Maikner reports that the Sept. 19 images appear to show a fan tail 12" long in p.a. 250 deg; on Oct. 17, there appears to be a 7" tail in p.a. 250 deg. 2025 UT R.A. (2000) Decl. Mag. Observer Sept.19.29534 3 10 56.65 +26 14 30.0 19.9 Maikner 19.30720 3 10 56.75 +26 14 33.7 19.7 " 19.31906 3 10 56.79 +26 14 36.1 19.8 " Oct. 17.17274 3 05 15.91 +27 08 14.4 19.4 " 17.18879 3 05 15.44 +27 08 14.8 19.4 " 17.20623 3 05 14.92 +27 08 15.1 19.4 " 17.24668 3 05 13.69 +27 08 16.2 19.5 " Regarding the recovery designation P/2025 S4, note that Pan-STARRS1 discovery A/2025 S2 was announced on MPEC 2025-T132, and Pan-STARRS2 discovery A/2025 S3 was announced on MPEC 2025-U94 (both objects having nearly parabolic orbits but not showing cometary activity). S. Deen (Simi Valley, CA, USA) writes that, after he noticed the otherwise-announced recovery of P/2015 TO_19 on the MPC's NEOCP website, he searched for additional images from the last and previous apparitions, finding some from the 2006 apparition as well as additional ones from the 2015-2016 apparition. The 2006 observations were obtained in the course of the Sloan Digital Sky Survey at Apache Point; the observations/magnitudes are, respectively, from r-, i-, and g-band images. The 2015 and 2016 observations were found on DECam images obtained with the 4-m reflector at Cerro Tololo; the last two of these were i-band images. The comet was generally quite faint in all of these images, and it did not display any obvious cometary activity. The 2006 Nov. 21 and both June 2015 observations appeared on MPEC 2025-U263, with no indication that they were found as a result of the 2025 observations. Below are Deen's measurements: 2006 UT R.A. (2000) Decl. Mag. Nov. 21.48723 7 00 53.03 +29 30 28.2 21.9 21.48806 7 00 53.02 +29 30 28.2 21.6 21.49055 7 00 52.97 +29 30 28.3 22.5 2015 UT R.A. (2000) Decl. Mag. June 19.43097 0 41 43.27 + 8 18 02.3 20.40835 0 42 35.73 + 8 25 27.9 22.8 2016 UT R.A. (2000) Decl. Mag. Dec. 28.25325 8 07 08.69 +24 43 04.9 21.5 Hidetaka Sato (Tokyo) reports re-measurement of his observations from 2016 Aug. 12 (obtained remotely at the Sierra Remote Observatory near Auberry, CA, USA), as tabulated below. 2016 UT R.A. (2000) Decl. Mag. Observer Aug. 12.48878 6 39 56.99 +27 30 15.3 Sato 12.49340 6 39 57.47 +27 30 14.8 21.4 " The residuals were -260" in R.A. and -70" in Decl. from the prediction for P/2015 TO_19 on NK 3319 (and ICQ's Comet Handbook 2025) by T. Kobayashi (Oizumi, Japan), with a corresponding correction of Delta(T) = +0.26 day. The following linked orbital elements by S. Nakano (Central Bureau) are from 93 observations spanning 2006 Nov. 21-2025 Oct. 31 (mean residual 0".4). The comet passed 0.63 AU from Jupiter on 1984 Aug. 3 and will pass 0.60 AU from Jupiter on 2028 Aug. 27 UT. Epoch = 2006 May 25.0 TT T = 2006 May 24.89688 TT Peri. = 89.16297 e = 0.3571520 Node = 321.83555 2000.0 q = 2.9456790 AU Incl. = 6.49517 a = 4.5822322 AU n = 0.10048204 P = 9.81 years Epoch = 2016 Feb. 22.0 TT T = 2016 Mar. 7.08276 TT Peri. = 89.31316 e = 0.3589126 Node = 321.64572 2000.0 q = 2.9252300 AU Incl. = 6.49966 a = 4.5629194 AU n = 0.10112066 P = 9.75 years Epoch = 2025 Nov. 21.0 TT T = 2025 Nov. 23.94467 TT Peri. = 89.43716 e = 0.3597898 Node = 321.60550 2000.0 q = 2.9110709 AU Incl. = 6.50493 a = 4.5470550 AU n = 0.10165032 P = 9.70 years Epoch = 2035 June 2.0 TT T = 2035 June 3.97271 TT Peri. = 112.81265 e = 0.3690010 Node = 292.08106 2000.0 q = 2.8901426 AU Incl. = 5.09000 a = 4.5802650 AU n = 0.10054678 P = 9.80 years Epoch = 2045 Mar. 1.0 TT T = 2045 Feb. 24.86665 TT Peri. = 113.49982 e = 0.3715462 Node = 291.76554 2000.0 q = 2.8508612 AU Incl. = 5.12628 a = 4.5363097 AU n = 0.10201171 P = 9.66 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 07 24 02 32.79 +20 58.0 3.034 3.003 78.6 19.4 20.2 2025 08 03 02 42.96 +22 07.3 2.892 2.989 85.5 19.8 20.1 2025 08 13 02 51.97 +23 11.3 2.751 2.976 92.7 19.9 20.0 2025 08 23 02 59.58 +24 09.8 2.611 2.964 100.3 19.6 19.9 2025 09 02 03 05.49 +25 01.9 2.476 2.954 108.4 18.9 19.7 2025 09 12 03 09.44 +25 46.9 2.349 2.944 116.9 17.8 19.6 2025 09 22 03 11.18 +26 23.5 2.232 2.936 125.9 16.1 19.5 2025 10 02 03 10.56 +26 50.3 2.130 2.929 135.5 13.9 19.4 2025 10 12 03 07.62 +27 05.5 2.045 2.923 145.5 11.2 19.3 2025 10 22 03 02.62 +27 07.5 1.982 2.918 155.8 8.1 19.2 2025 11 01 02 56.15 +26 55.9 1.943 2.914 165.4 4.9 19.2 2025 11 11 02 49.05 +26 31.9 1.932 2.912 170.2 3.3 19.1 2025 11 21 02 42.24 +25 58.5 1.948 2.911 164.2 5.3 19.2 2025 12 01 02 36.66 +25 20.5 1.991 2.911 154.3 8.4 19.2 2025 12 11 02 32.99 +24 43.2 2.059 2.913 143.9 11.5 19.3 2025 12 21 02 31.61 +24 11.2 2.149 2.916 133.6 14.1 19.4 2025 12 31 02 32.70 +23 47.6 2.256 2.920 123.8 16.3 19.5 2026 01 10 02 36.18 +23 33.9 2.378 2.925 114.4 17.8 19.6 2026 01 20 02 41.86 +23 30.3 2.509 2.931 105.6 18.9 19.7 2026 01 30 02 49.55 +23 35.9 2.648 2.939 97.2 19.4 19.9 2026 02 09 02 58.98 +23 49.3 2.790 2.948 89.3 19.6 20.0 2026 02 19 03 09.92 +24 08.7 2.934 2.958 81.7 19.3 20.1 2026 03 01 03 22.17 +24 32.4 3.076 2.969 74.5 18.8 20.2 2026 03 11 03 35.52 +24 58.5 3.215 2.981 67.6 17.9 20.3 2026 03 21 03 49.81 +25 25.3 3.350 2.995 60.9 16.9 20.4 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 November 6 (CBET 5633) Daniel W. E. Green