Electronic Telegram No. 5369 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 12P/PONS-BROOKS E. Jehin, M. Vander Donckt, S. Hmiddouch, and J. Manfroid, STAR Institute, University of Liege, report that they obtained recent observations with the 0.6-m TRAPPIST-South telescope at La Silla and TRAPPIST-North telescope at Oukaimden, Morocco (cf. CBETs 4729, 4840) using broadband and cometary HB narrowband gaseous and dust continuum filters. Preliminary production rates on 2024 Feb. 25 at 10k km using a Haser model: Q(OH) = 1.54 +/- 0.43 x 10E29 molecules/s, Q(CN) = 4.37 +/- 0.28 x 10E26 molecules/s, and Q(C_2) = 7.99 +/- 0.28 x 10E26 molecules/s. The dust-production rates via proxy A(0)f(rho) were estimated by profile-fitting at 10k km and corrected for the phase angle (cf. CBET 5807): A(0)fp(RC) = 17041 +/- 275 cm; A(0)fp(BC) = 14911 +/- 568 cm. Jehin adds that the gas-production rates had been increasing steeply in the previous two weeks, and the coma shows two bright spiral CN jets. C_2 had been rising faster than other species. On Feb. 29.8 UT, an outburst of 0.9 mag was measured in all BVRI filters compared to the previous night. K. Yoshimoto, Kumage, Yamaguchi, Japan, reports the following total V magnitudes and coma diameters (obtained with a 0.20-m f/8 Ritchey-Chretien reflector + CCD in January and March, and with a 0.08-m f/4.3 refractor + CMOS camera in February): Jan. 14.41 UT, 8.7, 7'.4; 28.41, 8.4, 5'.5; 29.41, 8.0, 5'.9; Feb. 2.41, 8.0, 7'.8, 10.43, 7.4, 7'.1 (40' tail in p.a. 355 deg); 12.43, 7.0, 7'.6 (1.5-deg tail in p.a. 7 degrees); Mar. 10.43, 6.0, 9'.2. Selected visual total-magnitude and coma-diameter estimates: 2023 Nov. 8.72 UT, 11.5, 1'.1 (W. Hasubick, Buchloe, Germany, 44-cm reflector); 11.71, 8.9, 2'.6 (Hasubick); Dec. 14.81, 9.5, 5' (J. J. Gonzalez, Leon, Spain, 0.20-m reflector); 2024 Jan. 19.76, 8.1, 3.1' (V. Gonano, Udine, Italy, 10x50 binoculars); 27.72, 8.0, 5'.5 (Gonano); 28.74, 8.5, 3'.3 (Hasubick, 10-cm refractor); 30.72, 8.1, 6' (Gonano); Feb. 4.72, 7.7, 6' (Gonano); 12.39, 8.0, 4' (S. Yoshida, Ibaraki, Japan, 0.40-m f/4.5 reflector); 16.41, 7.8, 8' (Y. Nagai, Saitama, Japan, 20x100 binoculars); 17.43, 7.0, 6' (Yoshimoto, 20x100 binoculars); 19.82, 7.4, 8' (Gonano); 26.42, 6.7, 7' (Yoshimoto); 27.43, 7.2, 6' (Nagai); Mar. 1.01, 5.7, -- (S. J. O'Meara, Lexington, MA, USA, 10x50 binoculars); 2.40, 5.7, 12' (Yoshimoto, 8x42 binoculars); 5.82, 5.7, 5' (Gonzalez, 10x50 binoculars; 1.2-deg tail in p.a. 10 deg); 9.14, 5.6, -- (C. S. Morris, Fillmore, CA, USA, 10x50 binoculars); 10.44, 5.6, 14' (Yoshimoto); 11.13, 5.2, about 20' (Morris; tail about 5 degrees long); 11.83, 5.3, 5' (Gonzalez, Zamora, Spain, naked eye); 13.44, 5.8, -- (Yoshimoto); 15.44, 5.5 (Yoshimoto). The following revised orbital elements by S. Nakano (Central Bureau) are from 7681 observations spanning 1883 Sept. 6-2024 Mar. 10 (mean residual 1".6), with corresponding non-gravitational parameters A_1 = +0.30 +/- 0.00 and A_2 = -0.0263 +/- 0.0000. The previous orbit in NK 4930 (and in the ICQ's Comet Handbook 2024) shows residuals of -8" in R.A. and +8" in Decl. for the recent 2024 observations. Astrometry from around 2023 Nov. 16 and 17 are not fitting in this orbit. The comet has passed 1.62 AU from Saturn on 1957 July 29 UT. Epoch = 1884 Jan. 25.0 TT T = 1884 Jan. 26.21729 TT Peri. = 199.17783 e = 0.9550365 Node = 255.77477 2000.0 q = 0.7757415 AU Incl. = 74.04076 a = 17.2527107 AU n = 0.01375365 P = 71.66 years Epoch = 1954 May 18.0 TT T = 1954 May 22.88479 TT Peri. = 199.02853 e = 0.9548315 Node = 255.89120 2000.0 q = 0.7736660 AU Incl. = 74.17716 a = 17.1284520 AU n = 0.01390359 P = 70.89 years Epoch = 2024 May 10.0 TT T = 2024 Apr. 21.12327 TT Peri. = 198.98832 e = 0.9545913 Node = 255.85620 2000.0 q = 0.7807748 AU Incl. = 74.19169 a = 17.1943741 AU n = 0.01382371 P = 71.30 years Epoch = 2095 Aug. 26.0 TT T = 2095 Aug. 11.10082 TT Peri. = 198.89080 e = 0.9548918 Node = 255.92870 2000.0 q = 0.7836218 AU Incl. = 74.04384 a = 17.3720510 AU n = 0.01361217 P = 72.41 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 4.0 and 2.5n = 12 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 02 20 22 48.39 +37 22.5 1.753 1.341 49.5 34.1 6.7 2024 03 01 23 38.44 +35 43.7 1.690 1.211 44.9 35.3 6.1 2024 03 11 00 29.36 +32 55.8 1.647 1.086 39.7 35.7 5.5 2024 03 16 00 54.40 +31 03.6 1.632 1.028 36.9 35.5 5.2 2024 03 21 01 18.80 +28 52.6 1.622 0.972 34.0 35.0 4.9 2024 03 26 01 42.33 +26 23.8 1.615 0.921 31.2 34.1 4.6 2024 03 31 02 04.85 +23 38.5 1.612 0.876 28.6 33.0 4.3 2024 04 05 02 26.28 +20 38.8 1.610 0.838 26.2 31.8 4.1 2024 04 10 02 46.59 +17 27.1 1.609 0.809 24.3 30.6 3.9 2024 04 15 03 05.83 +14 05.9 1.608 0.789 23.0 29.8 3.8 2024 04 20 03 24.11 +10 37.8 1.606 0.781 22.6 29.7 3.7 2024 04 25 03 41.59 +07 05.6 1.602 0.784 23.2 30.3 3.8 2024 04 30 03 58.47 +03 31.7 1.596 0.799 24.6 31.7 3.8 2024 05 05 04 15.00 -00 02.2 1.588 0.824 26.8 33.5 4.0 2024 05 10 04 31.40 -03 34.8 1.578 0.858 29.5 35.4 4.2 2024 05 15 04 47.91 -07 05.4 1.568 0.900 32.6 37.2 4.4 2024 05 20 05 04.72 -10 33.6 1.559 0.949 35.9 38.7 4.7 2024 05 25 05 22.02 -13 58.9 1.552 1.002 39.4 39.9 5.0 2024 05 30 05 39.98 -17 20.7 1.547 1.059 42.9 40.6 5.2 2024 06 04 05 58.71 -20 38.1 1.546 1.120 46.3 40.9 5.5 2024 06 09 06 18.29 -23 50.0 1.551 1.182 49.7 40.9 5.8 2024 06 14 06 38.78 -26 54.7 1.561 1.246 52.9 40.5 6.1 2024 06 19 07 00.16 -29 50.0 1.578 1.311 55.8 39.9 6.4 2024 06 29 07 45.34 -35 04.8 1.634 1.443 60.8 38.0 7.0 2024 07 09 08 32.78 -39 20.7 1.721 1.576 64.4 35.6 7.5 2024 07 19 09 20.74 -42 32.4 1.838 1.709 66.5 33.0 8.1 2024 07 29 10 07.31 -44 43.8 1.982 1.840 67.0 30.5 8.7 2024 08 08 10 51.02 -46 06.5 2.148 1.970 66.1 28.1 9.2 2024 08 18 11 31.04 -46 54.0 2.332 2.098 64.1 25.7 9.7 2024 08 28 12 07.22 -47 18.4 2.527 2.225 61.3 23.5 10.2 2024 09 07 12 39.84 -47 29.1 2.728 2.349 57.7 21.3 10.6 2024 09 17 13 09.32 -47 32.5 2.932 2.472 53.6 19.1 11.1 2024 09 27 13 36.13 -47 32.4 3.134 2.593 49.2 17.0 11.4 2024 10 07 14 00.70 -47 31.6 3.331 2.712 44.6 15.0 11.8 2024 10 17 14 23.38 -47 31.1 3.518 2.829 40.0 13.1 12.2 2024 10 27 14 44.44 -47 31.7 3.694 2.945 35.7 11.4 12.5 2024 11 06 15 04.09 -47 33.7 3.856 3.059 31.8 9.8 12.8 2024 11 16 15 22.45 -47 37.3 4.000 3.171 28.9 8.7 13.0 2024 11 26 15 39.62 -47 42.5 4.127 3.282 27.4 7.9 13.3 2024 12 06 15 55.65 -47 49.3 4.233 3.391 27.6 7.7 13.5 2024 12 16 16 10.51 -47 58.0 4.319 3.499 29.8 8.0 13.7 2024 12 26 16 24.18 -48 08.4 4.383 3.606 33.6 8.7 13.9 2025 01 05 16 36.60 -48 20.9 4.426 3.711 38.8 9.5 14.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 March 15 (CBET 5369) Daniel W. E. Green