Electronic Telegram No. 5706 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 (134717) 2000 AO_1 W. Pieczonka, Nowa Wies, Poland; and D. Blazewicz, Klaj, Poland, and International Occultation Timing Association (IOTA), European Section, report the discovery of an apparent satellite of minor planet (134717) based on an occultation of the star TYC 0387-00276-1 (Gaia DR3 ID 4432378559821438208), which has catalogued Gaia magnitudes G = 10.89 and R = 10.46, as observed on 2026 May 10.89 UT. The main-belt asteroid was 7.8 magnitudes fainter than the star. The star is listed in the Gaia DR3 catalogue as a non-single-star having a non-linear proper motion that is compatible with an acceleration model with seven parameters. The sky-plane-configuration diagram showing the observed chords of the May 10 occultation, and the corresponding Fresnel model of the system, is posted at http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5706_Fig1.png. Pieczonka observed from Trzebuska, Poland, using a 20-cm Newtonian telescope (+ ASI 294 MM CMOS video system and a PC synchronized by Network Time Protocol) and recorded three consecutive light drops of duration 0.43, 0.06, and 0.12 s, corresponding to chord lengths of 5.7, 0.8, and 1.6 km at the minor planet, respectively, with the interval between the chords being 0.21 and 3.05 s, corresponding to 2.6 and 40.1 km. The limiting magnitude of the recording was approximately 13.0 (G), and the flux of each of the three drops was lower than that of the comparison star UCAC4 464-057287, which has catalogued magnitudes 12.7 (G) and 12.2 (R). The depth of all three drops is sufficiently great to exclude the companion inferred from the Gaia non-single- star entry from being the explanation for any of the drops in the light curve. Blazewicz observed from Klaj, Poland, using a 35-cm Dobsonian telescope (+ GPS-disciplined DVTI+CAM 430 CMOS video system) and did not detect an occultation in the recording, which had a limiting magnitude of approximately 12.8 (G). The first drop is an occultation by the main body of (134717), which has a NEOWISE catalogued diameter of 7.8 +/- 0.8 km that is used in the sky-plane plot. The plot has the main body located between the two chords, demonstrating that the location of the main body is not constrained to be on one side of the chord of Pieczonka. The third drop has four data points near the bottom of the light drop and represents the occultation by an apparent satellite. Assuming that the apparent satellite has a circular profile, its diameter is between 1.3 and 2.0 km (i.e., 1.6 +/- 0.4 km) with a separation from the main body of 0".0374 in p.a. 82.8 +/- 4.1 degrees, corresponding to a distance of 47.9 km. The second drop does not have a clear explanation. While the drop is significantly deeper than any other noise variation in the light curve during the entire 1.3-minute recording, it lasts for only two exposures such that the possibility of it being a noise event cannot be reasonably excluded. The proximity of the drop to the main body suggests that it might be a 'grazing' occultation by an elongated primary, but neither the oblateness of 0.83 +/- 0.08 given in Carry et al. (2024, A.Ap. 687, A38) nor the Gaia FPR photometry of the asteroid supports the elongated shape required for a grazing occultation. The light drop might be caused by a satellite, but the signal noise precludes a reliable determination from the Fresnel modeling, with the light drop from a small body centered on the chord not being deep enough, and the presence of a larger body located to one side of the chord raising support for a grazing occultation explanation. Accordingly, there is no attribution of this drop in the light curve to any specific cause. The observed light curve, together with the light curve modeled using the Fresnel diffraction model, can be found at the following website URL: http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5706_Fig2.png. Figures 1 and 2 and the modeled light curve include the representation of a satellite body close to the main body purely for the purpose of representing that as a possible explanation for the second drop. D. Herald and D. Gault, 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. This report was forwarded to the Central Bureau by Herald. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 June 18 (CBET 5706) Daniel W. E. Green