The first multichord stellar occultation by the trans-Neptunian Binary (82075) 2000 YW134

<p>Trans-Neptunian objects (TNOs) are considered remnants of the solar system formation, and the study of their physical and dynamical properties gives clues about its origin and evolution [1]. A fraction of this population of small bodies is in the form of Trans-Neptunian Binaries (TNBs), firstly discovered two decades ago [2]. Our interest in them has grown since then, as the study of their mutual orbits can lead to a better understanding of the formation and evolution of the protoplanetary disk. Besides, Trans-Neptunian Binaries offer the opportunity to determine the masses of the bodies with great accuracy, which opens the door to determine their bulk densities. On the other hand, stellar occultations permit us to obtain the sizes and shapes of TNOs with accuracies that can almost reach the precision of the measurements from a spacecraft visit. This technique also enables the detection of secondary features like atmospheres, satellites, or rings [3, 4, 5]. So the study of stellar occultations by TNBs leads to the determination of the size, shape, mass, and bulk density of these bodies with unbeatable accuracy.</p> <p>In this work, we report the first multichord stellar occultation by the TNO (82075) 2000 YW₁₃₄ and its satellite S/2005 (82075) 1, which took place on 2022 February 23rd over the Gaia EDR3 star 627356458358636544 (m_V ~ 17.1 mag). The prediction was based on the Jet Propulsion Laboratory orbit solution JPL#24 [6, 7], which was updated afterward using astrometric data from the 1.5m telescope at Observatorio de Sierra Nevada (OSN, Granada, Spain) and the 1.23m telescope at Calar Alto (CAHA, Almer&#237;a, Spain).</p> <p>Seventeen observing sites participated in the event, which resulted in seven positive chords (five on the main body and two on the satellite), eight negative chords, and two sites that could not observe due to bad weather or technical issues.</p> <p>We fitted an ellipse to the extremities of the positive chords to derive the projected equivalent diameters of the two bodies. The position of the satellite was closer to the nominal JPL ephemeris than that of the main body. On the other hand, the preliminary derived lower limit for the equivalent projected diameter of the satellite is twice the previously estimated size [8]. We are currently analyzing photometric data to combine all the observations to provide an accurate portrait of this binary system.</p> <p>&#160;</p> <p>[1] Morbidelli, A., Levison, H. F., & Gomes, R. 2008, ed. M. A. Barucci, H. Boehnhardt, D. P. Cruikshank, A. Morbidelli, R. Dotson, 275</p> <p>[2] Veillet, C. et al. 2002, Nature, Volume 416, Issue 6882, pp. 711-713</p> <p>[3] Ortiz, J. L., Sicardy, B., Braga-Ribas, F., et al. 2012, Nature, 491, 566</p> <p>[4] Braga-Ribas, F., Sicardy, B., Ortiz, J. L., et al. 2013, ApJ, 773, 26</p> <p>[5] Ortiz, J.L., Santos-Sanz, P., Sicardy, B., et al. 2017, Nature, 550, 7675, pp. 219-223</p> <p>[6] https://astro.kretlow.de/stocc/predictions/</p> <p>[7] https://astro.kretlow.de/stocc/predictions/cetno/1559/</p> <p>[8] Stephens, Denise C.; Noll, Keith S.; 2006, AJ, 131, 2, pp. 1142-1148</p>