Electronic Telegram No. 5489 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/2015 CD_60 (LINEAR) An apparently asteroidal object with a comet-like orbit was discovered in 2015 (discovery observations tabulated below) with the 3.5-m f/1 Mercenne- Schmidt "Space Surveillance Telescope" (SST), which was then located at the White Sands Missile Range in New Mexico. The 2015 Feb. 13-14 SST observations were not officially entered into the MPC archive until 2015 Mar. 28, and the object was designated 2015 CD_60 when it was announced on MPS 595423 (dated 2015 Apr. 4). Earlier SST observations from 2015 Jan. 24 and 25 (which were linked together apparently already on 2022 Feb. 22) were later identified with 2015 CD_60 on MPS 612673 (dated 2015 June 28). On 2015 Jan. 24.1 UT, the r-band magnitude was given as 19.5-20.5, and on 2015 Jan. 25.1, the SST images yielded r = 19.9-20.9. The SST was a continuation to the LINEAR survey, which lends its name to this comet. 2015 UT R.A. (2000) Decl. Mag. Feb. 13.10665 3 19 56.49 +23 16 23.0 19.9 13.11072 3 19 56.93 +23 16 23.1 19.8 13.11487 3 19 57.35 +23 16 21.3 21.0 13.11894 3 19 57.82 +23 16 21.4 20.4 13.12396 3 19 58.26 +23 16 20.0 20.0 13.12818 3 19 58.80 +23 16 19.9 19.9 13.13239 3 19 59.28 +23 16 19.3 20.6 Apparently asteroidal "pre-discovery" images of this object were reported for two nights in late Nov. 2014 (unlinked at the time but identified with 2015 CD_60 when published on MPS 614635 on 2015 July 12) from exposures obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala, and these were apparently then found in the Minor Planet Center's "isolated tracklet file"; magnitude w = 20.2-20.3 was measured on 2014 Nov. 25.3 UT, and mag i = 20.0-20.2 was measured on 2014 Nov. 27.3. Catalina Sky Survey images of the object from 2015 Feb. 10.1 (at mag 19.3-20.3), reported in real time, were not identified either with 2015 CD_60 until MPS 614635 (2015 July 12). This object was apparently accidentally re-discovered in images obtained with the Mt. Lemmon Survey's 1.5-m reflector on 2024 Oct. 27 (discovery observations tabulated below) and reported then as an apparently asteroidal near-earth candidate. At some point after Oct. 27, this object was linked with 2015 CD_60. 2024 UT R.A. (2000) Decl. Mag. Oct. 1.43297 6 19 53.86 +33 03 53.9 21.5 1.43816 6 19 54.46 +33 03 53.0 20.7 1.44459 6 19 55.13 +33 03 51.7 21.0 1.44977 6 19 55.78 +33 03 50.2 21.6 27.43209 7 01 55.78 +30 54 10.4 20.2 27.43729 7 01 56.17 +30 54 08.8 27.44769 7 01 56.98 +30 54 04.5 After the comet was posted on the MPC's PCCP webpage in late 2024 (apparently due to the orbit appearing cometary), other astrometrists commented on the cometary appearance. A. Hale (Cloudcroft, NM, USA) writes that single 300-s CCD exposures taken on 2024 Dec. 9.0 UT with a 0.35-m Cassegrain reflector at Tenerife clearly show a small condensed coma of size 4" and a straight tail 8" long in p.a. 270 degrees. Six stacked 60-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) using a 0.43-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) on 2024 Dec. 9.54-9.55 show a strongly condensed coma 8" in diameter with a tail 15" long toward p.a. 280 deg; the magnitude was 18.6 as measured within a circular aperture of radius 5".7. Twelve additional stacked 60-s CCD exposures taken by Sato using a 0.51-m f/6.8 astrograph located also at the Utah Desert Remote Observatory on Dec. 12.5 show a strongly condensed coma 8" in diameter with a 30" tail toward p.a. 285 degrees; the magnitude was 18.4 as measured within a circular aperture of radius 4".9. Ninety-four stacked 30-s CCD exposures taken by A. Aletti (and measured by Aletti and M. Auteri) with a 0.20-m f/4 reflector at Varese, Italy, on 2024 Dec. 12.0 show a very condensed coma 4" wide with a faint, broad tail at least 15" long centered at p.a. 290 degrees. L. Buzzi (Varese, Italy) notes that seventy-four stacked 30-s CMOS images taken on 2024 Dec. 12.2 with a 0.84-m f/3.5 reflector in good conditions show a condensed coma 6" wide with a straight tail about 40" long in p.a. 285 degrees. Thirty additional stacked 60-s exposures taken by Buzzi on Dec. 30.0 show a compact coma of size 10" x 6" (mag 18.1) with a thin tail at least 85" long in p.a. 292 deg; when blinking two separate sets of images, Buzzi added that the tail might be as long as 150". Thirty-three stacked 60-s CMOS images taken by K. Yoshimoto (Kumage, Yamaguchi, Japan) using a 0.20-m f/8 Ritchey-Chretien reflector on 2024 Dec. 22.5 show a condensed coma 14" in diameter and no tail (total mag 18.0). Additional exposures by Yoshimoto on Dec. 23.5 and 24.5 show a condensed coma 14" in diameter and a faint tail 14" long in p.a. 270 deg; the total mag was 17.8 on Dec. 24.54. D. De Martin (Venezia, Italy) reports that CMOS taken on 2025 Jan. 2.8 with a 0.51-m f/6.8 CDK telescope at the Northern Skygems Observatory in Nerpio, Spain, show a condensed coma of size 5" and mag 18.1 with a straight 10" tail in p.a. 290 degrees. The available astrometry appears on MPEC 2025-A142. The following linked orbital elements by S. Nakano (Central Bureau) are from 164 observations spanning 2014 Nov. 25-2024 Dec. 26 (mean residual 0".4). These indicate that the comet passed 0.95 AU from Jupiter on 1974 Jan. 1 UT. Epoch = 2005 May 30.0 TT T = 2005 May 14.46246 TT Peri. = 178.84742 e = 0.5748394 Node = 280.04405 2000.0 q = 1.9429603 AU Incl. = 14.35598 a = 4.5699438 AU n = 0.10088760 P = 9.77 years Epoch = 2015 Apr. 8.0 TT T = 2015 Mar. 22.85895 TT Peri. = 180.00821 e = 0.5722053 Node = 279.61559 2000.0 q = 1.9658061 AU Incl. = 14.46284 a = 4.5952088 AU n = 0.10005670 P = 9.85 years Epoch = 2025 Jan. 5.0 TT T = 2024 Dec. 18.93557 TT Peri. = 179.08829 e = 0.5725576 Node = 279.22992 2000.0 q = 1.9643465 AU Incl. = 14.48253 a = 4.5955823 AU n = 0.10004451 P = 9.85 years Epoch = 2034 Oct. 5.0 TT T = 2034 Oct. 21.14567 TT Peri. = 180.47702 e = 0.5755408 Node = 278.64724 2000.0 q = 1.9337990 AU Incl. = 14.36641 a = 4.5559131 AU n = 0.10135401 P = 9.72 years Epoch = 2044 Aug. 13.0 TT T = 2044 July 26.50791 TT Peri. = 180.53618 e = 0.5741621 Node = 278.59121 2000.0 q = 1.9500274 AU Incl. = 14.32990 a = 4.5792710 AU n = 0.10057952 P = 9.80 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 12 16 07 24.64 +23 05.7 1.029 1.965 154.8 12.3 17.0 2024 12 26 07 19.00 +21 04.7 0.997 1.965 165.9 7.0 16.9 2025 01 05 07 11.70 +19 02.7 0.989 1.971 175.9 2.1 16.9 2025 01 15 07 04.45 +17 06.4 1.005 1.980 169.2 5.3 17.0 2025 01 25 06 58.76 +15 22.4 1.046 1.994 158.1 10.6 17.1 2025 02 04 06 55.74 +13 54.7 1.110 2.012 147.5 15.3 17.3 2025 02 14 06 55.94 +12 43.9 1.192 2.034 137.7 19.1 17.5 2025 02 24 06 59.36 +11 47.7 1.291 2.059 128.7 22.0 17.7 2025 03 06 07 05.72 +11 02.1 1.402 2.088 120.5 24.2 17.9 2025 03 16 07 14.62 +10 23.1 1.525 2.121 112.9 25.6 18.2 2025 03 26 07 25.56 +09 46.9 1.657 2.156 106.0 26.4 18.4 2025 04 05 07 38.15 +09 10.4 1.795 2.194 99.5 26.7 18.7 2025 04 15 07 51.99 +08 31.2 1.939 2.234 93.4 26.6 18.9 2025 04 25 08 06.75 +07 48.0 2.087 2.277 87.5 26.2 19.2 2025 05 05 08 22.19 +06 59.4 2.238 2.322 81.9 25.5 19.4 2025 05 15 08 38.06 +06 05.2 2.390 2.369 76.5 24.5 19.6 2025 05 25 08 54.21 +05 05.0 2.544 2.417 71.3 23.4 19.9 2025 06 04 09 10.50 +03 59.1 2.697 2.467 66.1 22.1 20.1 2025 06 14 09 26.82 +02 47.6 2.848 2.517 61.0 20.7 20.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 January 8 (CBET 5489) Daniel W. E. Green