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1. A Single-chord Stellar Occultation by the Extreme Trans-Neptunian Object (541132) Leleākūhonua

Author

Robert Weryk, Dave Herald, Naemi Fiechter, James J. Estes, Bruce Palmquist, Paola Mendoza, John Keller, Sherry Rennau, Ken Conway, Ryder Strauss, Olivia L. Ireland, Rodrigo Leiva, Emma D. Terris, Marc W. Buie, Ramsey Schar, Matthew A. MacDonald, Bruno Sicardy, Sean L. Haley, Mackenzie Dunham, J. J. Kavelaars, Robert H. Baker, Delsie McCrystal, Matthew Kehrli, Rima Givot, Joe Wise, Terry Bridges, Diana J. Swanson, Holly Werts, Elizabeth Wilde, Josselin Desmars, Bryan Dean, Jennifer N. Hayman, Erik M. Moore, Bruce Gowe, Cameron Glibbery, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
Absolute magnitude, Physics, [PHYS]Physics [physics], Chord (geometry), 010504 meteorology & atmospheric sciences, Star (game theory), Astronomy and Astrophysics, Astrophysics, Radius, Albedo, 01 natural sciences, Occultation, Space and Planetary Science, Geometric albedo, trans-Neptunian objects, 0103 physical sciences, stellar occultation, astrometry, Trans-Neptunian object, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, detached objects, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Lele\={a}k\={u}honua (also known by the provisional designation of 2015 TG387) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is $r={110}_{-10}^{+14}$ km, corresponding to a geometric albedo ${p}_{V}={0.21}_{-0.05}^{+0.03}$, for an adopted absolute magnitude of H V = 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint., Comment: 7 figures

Published
2020

2. Results from a triple chord stellar occultation and far-infrared photometry of the trans-Neptunian object (229762) 2007 UK126

Author

Jerry Bardecker, Julio Camargo, Thomas Müller, Alfred Krabbe, Jürgen Wolf, Aart M. Olsen, Dave Herald, Felipe Braga-Ribas, Jose Luis Ortiz, Karsten Schindler, Csaba Kiss, European Commission, Hungarian Scientific Research Fund, Junta de Andalucía, German Academic Exchange Service, Universities Space Research Association (US), European Space Agency, and National Research, Development and Innovation Office (Hungary)

Subjects
Rotation period, 010504 meteorology & atmospheric sciences, Kuiper belt objects: individual: (229762) 2007 UK126, FOS: Physical sciences, Astrophysics, individual: (229762) 2007 UK126 [Kuiper belt objects], Ellipse, 01 natural sciences, Occultation, Photometry (optics), Far infrared, Planet, Geometric albedo, Methods: data analysis, 0103 physical sciences, Trans-Neptunian object, data analysis [Methods], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Astronomy and Astrophysics, Radiation mechanisms: thermal, 13. Climate action, Space and Planetary Science, thermal [Radiation mechanisms], Occultations, Astrophysics - Earth and Planetary Astrophysics
Abstract

Schindler, K. et. al., Context. A stellar occultation by a trans-Neptunian object (TNO) provides an opportunity to probe the size and shape of these distant solar system bodies. In the past seven years, several occultations by TNOs have been observed, but mostly from a single location. Only very few TNOs have been sampled simultaneously from multiple locations. Sufficient data that enable a robust estimation of shadow size through an ellipse fit could only be obtained for two objects. Aims. We present the first observation of an occultation by the TNO 2007 UK126 on 15 November 2014, measured by three observers, one nearly on and two almost symmetrical to the shadow's centerline. This is the first multi-chord dataset obtained for a so-called detached object, a TNO subgroup with perihelion distances so large that the giant planets have likely not perturbed their orbits. We also revisit Herschel/PACS far-infrared data, applying a new reduction method to improve the accuracy of the measured fluxes. Combining both datasets allows us to comprehensively characterize 2007 UK126. Methods. We use error-in-variable regression to solve the non-linear problem of propagating timing errors into uncertainties of the ellipse parameters. Based on the shadow's size and a previously reported rotation period, we expect a shape of a Maclaurin spheroid and derive a geometrically plausible size range. To refine our size estimate of 2007 UK126, we model its thermal emission using a thermophysical model code. We conduct a parametric study to predict far-infrared fluxes and compare them to the Herschel/PACS measurements. Results. The favorable geometry of our occultation chords, combined with minimal dead-time imaging, and precise GPS time measurements, allow for an accurate estimation of the shadow size (best-fitting ellipse with axes 645.80 +/- 5.68 km x 597.81 +/- 12.74 km) and the visual geometric albedo (p(V) = 15.0 +/- 1.6%). By combining our analyses of the occultation and the far-infrared data, we can constrain the effective diameter of 2007 UK126 to d(eff) = 599-629 km. We conclude that subsolar surface temperatures are in the order of approximate to 50 55 K., K.S. has been supported financially by a one-year fellowship from the German Academic Exchange Service (DAAD) during his stay at NASA Ames Research Center, CA as part of his Ph.D. research. K.S. would also like to thank the Universities Space Research Association (USRA) for their support throughout his thesis. T.M., C.K. and J.L.O. have received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378. C.K. has been supported by the PECS grant # 4000109997/13/NL/KML of the Hungarian Space Office and the European Space Agency, the K-104607 grant of the Hungarian Research Fund (OTKA), and the GINOP-2.3.2-15-2016 00003 grant of the National Research, Development and Innovation Office of Hungary (NKFIH). J.L.O. acknowledges support from Proyecto de Excelencia J.A. 2012-FQM1776.

Published
2017

3. Astrometric results of observations of mutual occultations and eclipses of the Saturnian satellites in 2009

Author

D. L. Gorshanov, O. Dechambre, Ricard Casas, A. Sergeev, A. Murphy, Brian Loader, G. Dourneau, F. Colas, A. Kurenya, A. Farmakopoulos, Marcelo Assafin, V. Kozlov, Julio Camargo, J. F. Le Campion, A. Dias-Oliveira, P. Valdes Sada, D. N. da Silva Neto, V. Tsamis, X. Zhang, D. Gault, J. Lecacheux, N. V. Emelyanov, Dave Herald, Apostolos A. Christou, Felipe Braga-Ribas, A. Massalle, R. Vieira-Martins, Jean-Eudes Arlot, T. George, N. Parakhin, Maksim V. Andreev, C. Schnabel, Valery Lainey, Alexandre Roman-Lopes, M. Mc Brien, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatorio Nacional/MCT, Observatório Nacional/MCT, Observatório do Valongo, Universidade Federal do Rio de Janeiro Ladeira do Pedro Antônio, Universidade Estadual da Zona Oeste (UEZO), Universidade Estadual da Zona Oeste, M2A 2012, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), International Occulting and Timing Association (IOTA), International Occulting and Timing Association, Pulkovo Observatory, Russian Academy of Sciences [Moscow] (RAS), Canberra Astronomical Society, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)

Subjects
010504 meteorology & atmospheric sciences, planets and satellites: dynamical evolution and stability, Context (language use), Ephemeris, 01 natural sciences, Geocentric coordinates, Photometry (optics), 0103 physical sciences, occultations, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Astrometry, Position angle, Light curve, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Space and Planetary Science, astrometry, Astrophysics::Earth and Planetary Astrophysics, Right ascension, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], catalogs
Abstract

Context. The photometry of mutual occultations and eclipses of natural planetary satellites can be used to infer very accurate astrometric data. This can be achieved by processing the light curves of the satellites observed during international campaigns of photometric observations of these mutual events. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Uranian satellites made during the international campaign in 2007. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events that explicitly depends on parameters that these accurate observations should be sensitive to, including the albedos of the satellites. Our original method is applied to derive astrometric data in relative positions from photometric observations of mutual occultations and eclipses of the Uranian satellites. Results. We process the 41 light-curves obtained during the international campaign of photometric observations of the Uranian satellites in 2007. The root-mean-square (rms) of the residuals “observations minus calculations” (O‐C) with respect to theory for the best 34 observations are equal to 10.3 and 17.7 mas in right ascension and declination, respectively. For five observations only the position angle was derived. Topocentric or heliocentric angular differences for satellites pairs were obtained from 25 central instant offsets between observation and theory during the time period from May 4, 2007 to January 4, 2008. Conclusions. The rms of the residuals is from 10 to 20 mas that corresponds in situ to 10 to 20 km. These mutual event observations appear to be the most accurate astrometric ground-based observations of the major Uranian satellites to-date and should be used for dynamical purposes.

Published
2012

4. SIZE AND SHAPE FROM STELLAR OCCULTATION OBSERVATIONS OF THE DOUBLE JUPITER TROJAN PATROCLUS AND MENOETIUS

Author

Yanzhe Liu, Katherine J. Abramson, Kevin J. Walsh, William J. Merline, S. Preston, Lowell Sherrod, Theodore J. Swift, Roger Venable, Clay Sherrod, Daniel B. Caton, Marc W. Buie, Brad Timerson, Lawrence W. Taylor, William M. Owen, Mark A. Croom, David W. Dunham, Ronald Royer, Aart M. Olsen, Steve J. Conard, Harold F. Levison, Dave Herald, Catherine B. Olkin, Andrew E. Scheck, J. A. Dunford, Harry B. Abramson, P. D. Maley, Chad K. Ellington, R. Dunford, and D. Breit

Subjects
Physics, Jupiter, Rotation period, Space and Planetary Science, Trojan, Asteroid, Astronomy, Astronomy and Astrophysics, Astrometry, Position angle, Light curve, Occultation
Abstract

We present results of a stellar occultation by the Jupiter Trojan asteroid Patroclus and its nearly equal size moon, Menoetius. The geocentric mid-time of the event was 2013 October 21 06:43:02 UT. Eleven sites out of 36 successfully recorded an occultation. Seven chords across Patroclus yielded an elliptical limb fit of 124.6 by 98.2 km. There were six chords across Menoetius that yielded an elliptical limb fit of 117.2 by 93.0 km. There were three sites that got chords on both objects. At the time of the occultation we measured a separation of 664.6 km (0.247 arcsec) and a position angle for Menoetius of 2657 measured eastward from J2000 north. Combining this occultation data with previous light curve data, the axial ratios of both objects are 1.3 : 1.21 : 1, indicative of a mostly oblate ellipsoid with a slight asymmetry in its equatorial projection. The oblate shape is not an equilibrium shape for the current rotation period, but would be if it were rotating with an ~8 h period. This faster period is consistent with a pre-evolved state of the system with an orbital separation that is 50% smaller. Our best estimate of the system density is 0.88 g cm−3.

Published
2015

5. CONSTRAINTS ON CHARON'S ORBITAL ELEMENTS FROM THE DOUBLE STELLAR OCCULTATION OF 2008 JUNE 22

Author

T. Dobosz, J. G. Greenhill, Marcelo Assafin, Bruno Sicardy, D. Buckley, W. Beisker, Greg Bolt, F. Benard, V. Batista, J.-P. Teng-Chuen-Yu, François Colas, Alain Doressoundiram, C. Gruhn, J. Broughton, J. Lecacheux, S. Mathers, Julio Camargo, Roberto Vieira-Martins, D. Gault, A. Peyrot, A. H. Andrei, J. Biggs, C. De Witt, B. Lade, S. Dieters, Dave Herald, Felipe Braga-Ribas, D. N. da Silva Neto, R. Groom, Y. Boissel, E. Frappa, Thomas Widemann, S. Kerr, F. Roques, Raoul Behrend, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Craigie, Reedy Creek, Bankstown, International Occulting and Timing Association (IOTA), International Occulting and Timing Association, Astronomical Association of Queensland (AAQ), Association astronomique de la Réunion (AAR), Association astronomique de la Réunion, Euraster, International Occultation Timing Association European Section (IOTA ES), International Occultation Timing Association European Section, South African Astronomical Observatory (SAAO), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Springbok, International Amateur Sternwarte (IAS), International Amateur Sternwarte, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Perth Observatory, School of Mathematics and Physics, University of Tasmania [Hobart, Australia] (UTAS), Astronomical Society of Western Australia (ASWA), Canberra Astronomical Society, Stockport Observatory, Southern Cross Observatory, Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), Observatório Nacional/MCT, Universidade Estadual da Zona Oeste (UEZO), Universidade Estadual da Zona Oeste, Geneva Observatory, University of Geneva [Switzerland], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de Genève = University of Geneva (UNIGE)

Subjects
Physics, Orbital elements, Orbital plane, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Orbital node, Equator, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy, Astronomy and Astrophysics, Astrophysics, Ephemeris, 01 natural sciences, Pluto, True longitude, Kuiper belt objects : individual : Pluto Charon, planets and satellites : fundamental parameters, Space and Planetary Science, occultations, 0103 physical sciences, astrometry, Longitude, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

The original publication is available at http://iopscience.iop.org/1538-3881/; International audience; Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Réunion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X= + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y= + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L= 153.483 ± 0fdg071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r= 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the "TB97" solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the "T08" solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of ΔL= + 0.073 ± 0fdg071 in longitude, and Δr= + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only ΔL= 0.033 ± 0fdg071 in longitude, it exhibits a significant radial discrepancy of Δr= 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 × 10-3in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a = 19636 km, all other orbital elements remaining the same ("T08/TB97" solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution.

Published
2011

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