Electronic Telegram No. 5629 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 (60186) LAS CRUCES H. Pavlov, P. Nosworthy, and D. Gault, Trans-Tasman Occultation Alliance (TTOA), report the discovery of an apparent satellite of minor planet (60186) based on the occultation of the star UCAC4 314-078578 (catalogued Gaia magnitudes G = 13.3 and R = 12.4) on 2025 June 26.4706 UT. This main-belt asteroid was 5.3 magnitudes fainter than the star. Gault (chord 1) observed from Hawkesbury Heights, west of Sydney, Australia, using a 30-cm telescope (+ Watec WAT-910BD video camera) and did not record an occultation. Nosworthy (chord 2) observed from Hazelbrook, west of Sydney, Australia, using a 28-cm telescope (+ Watec WAT-910BD video camera) and recorded an occultation of duration 1.60 s, corresponding to a chord length of 14.3 km. Pavlov (chord 3) observed from St. Clair, west of Sydney, Australia, using a 35-cm telescope (+ Watec WAT-910BD video camera) and recorded an occultation of duration 0.24 s, corresponding to a chord length of 2.1 km. The light curves from the observation, with corresponding chord numbers, are posted at the following URL: http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5629_Fig1.png. The instants of closest appulse to the main body and the satellite are marked on the axis of each light curve by red and purple arrows, respectively. The flux during Gault's recording was not observed to drop (no occultation). The flux during Nosworthy's occultation dropped to the limiting magnitude of the recording (approximate mag G = 15, R = 14.3). The flux during Pavlov's occultation dropped below the level of comparison star UCAC4 314-078600 (catalogued Gaia magnitudes G = 14.2, R = 13.3) but did not reach the limiting magnitude of the recording. While the magnitude drops observed by Nosworthy and Pavlov are different, the magnitude drops considered together are too large to be explained by a double star. Using the Gaia DR3 parallax measurement (0.2343 mas) and the star's photometric radius measurement (radius_gspphot, 15.2248 solar radii) and uncertainties, the apparent diameter of the star was calculated to be 0.03 +0.00/-0.01 mas -- which is far too small for the level of the light drop being caused by either a partial or annular occultation of the star. Fresnel diffraction analysis of Pavlov's chord using a range of diameters and oblateness is consistent with a tangential graze of a body having a mean diameter of 4 km +/- 2 km. Comparison of the observed light curve and the Fresnel diffraction pattern modeled for a diameter of 4 km is posted at the following website URL: http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5629_Fig2.png. The NEOWISE-catalogue diameter of the minor planet is 13.5 +/- 1.4 km. No rotational light-curve data are available for this asteroid. Gaia DR3 G- magnitude measurements of this asteroid made on 29 dates do not indicate any significant rotational variation in magnitude. The data from Carry et al. (2024, A.Ap. 687, A38) indicate an oblateness for this asteroid of 0.81. These diameters and oblateness are used in the sky-plane configuration diagram, showing the observed occultation chords, as posted at website URL http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5629_Fig3.png. The apparent satellite is shown as circular with a diameter of 4 km, positioned on one side of the occultation chord. The mean separation of the two potential locations of the presumed satellite is 0".016 in p.a. 265 +/- 5 degrees, with a sky-plane separation of 32 km. D. Herald, TTOA; and C. Weber, European Section of the International Occultation Timing Association, aided in the analysis; and B. Anderson provided the Fresnel diffraction tool. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 November 2 (CBET 5629) Daniel W. E. Green