Stellar Occultation by the Resonant Trans-Neptunian Object (523764) 2014 WC510 Reveals a Close Binary TNO Rodrigo Leiva, Marc Buie, John Keller, Lawrence Wasserman, Jj Kavelaars, Terry Bridges, Sean Haley, Ryder Strauss, Elizabeth Wilde, Robert Weryk, et al. To cite this version: Rodrigo Leiva, Marc Buie, John Keller, Lawrence Wasserman, Jj Kavelaars, et al.. Stellar Occultation by the Resonant Trans-Neptunian Object (523764) 2014 WC510 Reveals a Close Binary TNO. The Planetary Science Journal, IOP Science, 2020, 1 (2), pp.48. 10.3847/PSJ/abb23d. hal-03256653 HAL Id: hal-03256653 https://hal.archives-ouvertes.fr/hal-03256653 Submitted on 10 Jun 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License The Planetary Science Journal, 1:48 (21pp), 2020 September https://doi.org/10.3847/PSJ/abb23d © 2020. The Author(s). Published by the American Astronomical Society. Stellar Occultation by the Resonant Trans-Neptunian Object (523764) 2014 WC510 Reveals a Close Binary TNO Rodrigo Leiva1 , Marc W. Buie1 , John M. Keller2 , Lawrence H. Wasserman3 , JJ Kavelaars4 , Terry Bridges5,6, Sean L. Haley2, Ryder Strauss2, Elizabeth Wilde2, Robert Weryk7 , Pierre Kervella8 , Robert Baker9,10, Stephen Alan Bock9, Ken Conway9,11, Juan M. Cota, Jr.9,12, James J. Estes9,13, María L. García9,12, Matthew Kehrli9,14, Andrew McCandless9,12, Keitha McCandless9,12, Edgar Self9,12, Cole Settlemire9,12, Diana J. Swanson9,14, Doug Thompson9,15, and J. A. Wise9,16 1 Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302, USA; [email protected] 2 University of Colorado Boulder, 2000 Colorado Avenue, Boulder, CO 80309, USA 3 Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA 4 National Research Council of Canada, Victoria BC V9E 2E7, Canada 5 Department of Physics and Astronomy, Okanagan College, Kelowna, BC, Canada 6 CanCON, Canadian Research and Education Collaborative Occultation Network, Canada 7 Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA 8 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon, France 9 RECON, Research and Education Collaborative Occultation Network, USA 10 Wildwood Institute for STEM Research and Development, Los Angeles, CA, USA 11 Foothills Library, 13226 S Frontage Road, Yuma, AZ 85367, USA 12 Calipatria High School Astronomy Club, 601 W Main Street, Calipatria, CA 92233, USA 13 Laughlin HS/Bullhead City, Laughlin, NV, USA 14 California Polytechnic State University, San Luis Obispo, CA 93407, USA 15 Arizona Western College, Yuma, AZ 85365, USA 16 Wildwood Institute for STEM Research and Development, 11811 W Olympic Boulevard, Los Angeles, CA 90064, USA Received 2020 May 4; revised 2020 August 18; accepted 2020 August 21; published 2020 September 28 Abstract We report on the stellar occultation by (523764) 2014 WC510 observed on 2018 December 1 UT. This occultation campaign was part of the Research and Education Collaborative Occultation Network (RECON), a network of small telescopes spread over 2000 km in western USA and Canada. Light curves from six stations revealed three groups of two or more consecutive flux drops correlated in time between adjacent stations. A Bayesian model comparison reveals that a model with a double object occulting a double star is favored over alternative models considered. For the statistically favored model, we determined that the primary component of the object has a diameter dp=181±16 km and the secondary ds=138±32 km, assuming identical geometric albedo between the two components. The two components have a projected separation of 349±26 km. Adopting an absolute magnitude for the system of HV=7.2 from the Minor Planet Center, we derive a geometric albedo of pV=5.1%±1.7%. This is the smallest resonant object with an occultation size measurement and with a detected secondary from a ground-based stellar occultation, filling a region of the size versus separation parameter space of binary objects that is largely unexplored. The results show the capabilities of the unique design of the RECON experiment sensitive to small objects and close binaries. 2014 WC510 is presently at a low galactic latitude where the high surface density of stars will provide good occultation opportunities in the upcoming years. Unified Astronomy Thesaurus concepts: Resonant Kuiper belt objects (1396); Stellar occultation (2135); Trans- Neptunian objects (1705); Bayesian statistics (1900) Supporting material: data behind figures 1. Introduction sinusoidal as that for Pluto. The orbital period is 246 yr, its heliocentric distance ranges from 28.7 to 50.8 au, and its orbital (523764) 2014 WC was discovered on 2011 by Pan- 510 inclination is 19°.8. STARRS1 (Chambers et al. 2016). The Deep Ecliptic Survey Very little is known so far about this object’s physical (DES) dynamical classification of this object is that it inhabits a fi properties. At the time of the occultation, it had an apparent mean-motion resonance with Neptune, speci cally the magnitude of V=22.1 and was 30.5 au from the Sun and + 2 ( ) 3:2e 6:3i . See Elliot et al. 2005 for details about the 29.6 au from Earth. Based on its estimated absolute magnitude DES classification system. This object is also in a Kozai secular of HV=7.2±0.3, 2014 WC510 would have a diameter of resonance with an 18° libration amplitude. In comparison, the 220 km assuming a 5% albedo, or a diameter of 90 km Kozai libration amplitude of (134340) Pluto is 24°.4. However, assuming a 30% albedo. the Kozai resonant argument for 2014 WC510 is not as cleanly Size, geometric albedo, and binarity are basic physical properties of trans-Neptunian objects (TNOs), and these are the primary observational goals of the Research and Education Original content from this work may be used under the terms ( ) of the Creative Commons Attribution 4.0 licence. Any further Collaborative Occultation Network RECON . With these distribution of this work must maintain attribution to the author(s) and the title measurements, we expect to contribute to the knowledge of of the work, journal citation and DOI. the size distribution of these objects. Additionally, the binary 1 The Planetary Science Journal, 1:48 (21pp), 2020 September Leiva et al. fraction among different dynamical classes and binary proper- can we hope to provide firm confirmation of these candidates ties such as component size ratio and inclination give us clues and determine the binary or contact binary properties. RECON about the prevalent planetesimal formation mechanism (Nes- (Buie & Keller 2016) was designed for this purpose and can vorný et al. 2019). Furthermore, binaries with known orbits can detect objects down to about 50–100 km in diameter while also provide direct measurement of the system mass and ultimately searching for multiple systems with separations of about the bulk density when combined with size measurements. 2000 km all the way down to contact binaries. Stellar occultations provide a powerful tool to support the Most stellar occultation results published so far involve large collection of these measurements. objects with relatively good signal-to-noise ratio (S/N) where An estimate for the size of TNOs can also be obtained from the standard analysis approach is to extract the times of radiometric measurements with typical uncertainties of 10%– disappearance and reappearance of the star as seen from each 20% (Moullet et al. 2011). More than a hundred objects have observer. The determination of a physical parameter such as size estimations from this technique (Kovalenko et al. 2017). size, shape, and pole position is then determined by fitting a 2D The stellar occultation technique provides more accurate or 3D shape using a minimization approach (Widemann et al. measurements of sizes and shapes, but the thermal method, 2009) or using a Bayesian approach (Brown 2013; Leiva et al. so far, is far more efficient in the collection of large numbers of 2017). The determination of disappearance and reappearance measurements, albeit of lower precision. Sizes from stellar times becomes impractical when dealing with stellar occulta- occultations are directly useful but can also provide crucial data tions where the disappearance and reappearance of the occulted / for cross-calibration of thermal measurements (Lellouch et al. star are ambiguous because of low S N, short duration of the 2017). To date, only 14 TNOs or their satellites (excluding occultation, or both. Such cases often require comparison of fl Pluto) have an accurate size and albedo published from stellar different models, including the case where the stellar ux might occultations: (134340) Pluto I Charon (satellite of Pluto; be solely explained by random noise variations in the light ) ( ) ( ) curve with no occultation at all. Sicardy et al. 2006 , 55636 2002 TX300 Elliot et al. 2010 , ( ) (136199) Eris (Sicardy et al. 2011), (136472) Makemake (Ortiz In our work, we perform two levels of Bayesian inference 1 et al. 2012), (50000) Quaoar (Braga-Ribas et al. 2013), to quantitatively compare alternative models to determine ( ) ( ) ( ) which one is favored given the data and a model for the 119951 2002 KX14 Alvarez-Candal et al. 2014 , 229762 ( ) G!kún’hòmdímà (Benedetti-Rossi et al. 2016), (136108) uncertainties in the measurements, and 2 to estimate the parameter values and uncertainties for the favored model.