Electronic Telegram No. 5719 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 (39249) 2000 YR_88 D. Gault and P. Nosworthy, Trans-Tasman Occultation Alliance (TTOA), reports the discovery of an apparent satellite of minor planet (39249) based on an occultation of the star UCAC4 293-175482 (which has catalogued Gaia magnitudes G = 11.08 and R = 10.39) on 2026 April 10.764 UT. This main-belt asteroid had a magnitude of 19.1, which was 8.0 magnitudes fainter than the target star. Gault observed from Hawkesbury Heights, NSW, Australia, using a 30-cm telescope (+ Watec WAT-910BD video camera + GPS video time inserter). The recording showed two consecutive occultations of durations 0.22 and 1.82 s, separated by 1.3 s, corresponding to chord lengths of 1.5 and 12.8 km. The flux of the first drop fell to the level of the comparison star UCAC4 293-175333, which has catalogued magnitudes 12.2 (G) and 11.7 (R), and the flux for the second drop was to the limiting magnitude of the recording, which was approximately 13.0 (G) and 12.1 (R). The depths of the two drops (1.1 and 1.9 in G, 1.3 and 1.7 in R) are sufficiently great to exclude a double star from being the explanation for the light curve. Nosworthy observed from Hazelbrook, NSW, Australia, using a 28-cm telescope (+ Watec WAT-910BD video camera + GPS video time inserter), and did not record an occultation. The NEOWISE diameter of the asteroid is 10.6 +/- 0.8 km. Gaia DR3 magnitude measurements suggest a rotational light variation in the order of 0.30 magnitude, suggesting that the main body of the asteroid is significantly non-spherical and has been modeled (with regard to the light curve of Gault and the "miss" observation of Nosworthy) as an ellipse having an area corresponding to the NEOWISE-catalogued diameter with axes of 12.8 x 8.8 km oriented parallel to the chords, with its center located north of the chord of Gault. Fresnel modeling of the drop from the apparent satellite indicates that the chord was tangential to the limb of the apparent satellite, with the modeling suggesting the large light-level variation within that drop may not be primarily a noise variation, but might represent a limb irregularity on the order of 150 m. The modeling indicates that the minimum size of the apparent satellite is an ellipse of 2.4 x 1.4 km, with the maximum diameter for a circular body being about 6 km. The separation of the satellite was 0".0088 in p.a. 87 +/- 4 degrees, with a separation of 16.2 km. The sky-plane configuration showing the observed occultation chords is posted at http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5719_Fig1.png. Two representative models of the system, and the observed light curves with superimposed Fresnel modeled light curves, are posted at website URL http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5719_Fig2.png. The upper two diagrams show models of the system, with the left representing the assumed satellite at its minimum size and the right representing the assumed satellite with a diameter of 6 km. The light curve plots provide the observed light curves with superimposed representative Fresnel-modeled light curves. In Nosworthy's light curve, a red arrow indicates the location corresponding to the main-body event, and a blue arrow indicates the location corresponding to the apparent satellite drop. D. Herald, Trans-Tasman Occultation Alliance; and C. Weber, European Section of the IOTA, aided in the analysis; the reader is also referred to the end notes on CBET 5679. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 July 28 (CBET 5719) Daniel W. E. Green