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Title: THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS

Abstract

We present results derived from the first multi-chord stellar occultations by the transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, and from a single-chord occultation observed on 2012 October 15. If the timing of the five chords obtained in 2011 were correct, then Quaoar would possess topographic features (crater or mountain) that would be too large for a body of this mass. An alternative model consists in applying time shifts to some chords to account for possible timing errors. Satisfactory elliptical fits to the chords are then possible, yielding an equivalent radius R{sub equiv} = 555 {+-} 2.5 km and geometric visual albedo p{sub V} = 0.109 {+-} 0.007. Assuming that Quaoar is a Maclaurin spheroid with an indeterminate polar aspect angle, we derive a true oblateness of {epsilon}= 0.087{sup +0.0268}{sub -0.0175}, an equatorial radius of 569{sup +24}{sub -17} km, and a density of 1.99 {+-} 0.46 g cm{sup -3}. The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial orbit. Finally, we detect no global atmosphere around Quaoar, considering a pressure upper limit of about 20 nbar for a pure methane atmosphere.

Authors:
; ;  [1]; ; ;  [2]; ;  [3]; ; ;  [4];  [5];  [6]; ;  [7];  [8];  [9];  [10];  [11];
  1. Observatorio Nacional, Rio de Janeiro (Brazil)
  2. Observatoire de Paris, LESIA, F-92195 Meudon (France)
  3. Instituto de Astrofisica de Andalucia-CSIC, E-18080 Granada (Spain)
  4. Observatorio Astronomico Los Molinos, Montevideo U-12400 (Uruguay)
  5. Observatorio do Valongo/UFRJ, Rio de Janeiro (Brazil)
  6. Observatoire de Geneve, Sauverny (Switzerland)
  7. Observatoire de Paris, IMCCE, F-75014 Paris (France)
  8. San Pedro de Atacama Celestial Explorations, San Pedro de Atacama (Chile)
  9. Universidade Estadual de Ponta Grossa, Ponta Grossa (Brazil)
  10. Universidade Federal de Santa Catarina, Florianopolis (Brazil)
  11. Unidad de Astronomia, Universidad de Antofagasta, Antofagasta (Chile)
Publication Date:
OSTI Identifier:
22140281
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 773; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALBEDO; DENSITY; ECLIPSE; MASS; METHANE; ORBITS; PLANETS; SATELLITE ATMOSPHERES; SATELLITES; SPHEROIDS; STARS; U QUARKS

Citation Formats

Braga-Ribas, F., Vieira-Martins, R., Camargo, J. I. B., Sicardy, B., Lellouch, E., Lecacheux, J., Ortiz, J. L., Morales, N., Tancredi, G., Roland, S., Bruzzone, S., Assafin, M., Behrend, R., Vachier, F., Colas, F., Maury, A., Emilio, M., Amorim, A., Unda-Sanzana, E., Almeida, L. A., E-mail: ribas@on.br, and others, and. THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS. United States: N. p., 2013. Web. doi:10.1088/0004-637X/773/1/26.
Braga-Ribas, F., Vieira-Martins, R., Camargo, J. I. B., Sicardy, B., Lellouch, E., Lecacheux, J., Ortiz, J. L., Morales, N., Tancredi, G., Roland, S., Bruzzone, S., Assafin, M., Behrend, R., Vachier, F., Colas, F., Maury, A., Emilio, M., Amorim, A., Unda-Sanzana, E., Almeida, L. A., E-mail: ribas@on.br, & others, and. THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS. United States. https://doi.org/10.1088/0004-637X/773/1/26
Braga-Ribas, F., Vieira-Martins, R., Camargo, J. I. B., Sicardy, B., Lellouch, E., Lecacheux, J., Ortiz, J. L., Morales, N., Tancredi, G., Roland, S., Bruzzone, S., Assafin, M., Behrend, R., Vachier, F., Colas, F., Maury, A., Emilio, M., Amorim, A., Unda-Sanzana, E., Almeida, L. A., E-mail: ribas@on.br, and others, and. 2013. "THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS". United States. https://doi.org/10.1088/0004-637X/773/1/26.
@article{osti_22140281,
title = {THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS},
author = {Braga-Ribas, F. and Vieira-Martins, R. and Camargo, J. I. B. and Sicardy, B. and Lellouch, E. and Lecacheux, J. and Ortiz, J. L. and Morales, N. and Tancredi, G. and Roland, S. and Bruzzone, S. and Assafin, M. and Behrend, R. and Vachier, F. and Colas, F. and Maury, A. and Emilio, M. and Amorim, A. and Unda-Sanzana, E. and Almeida, L. A., E-mail: ribas@on.br and others, and},
abstractNote = {We present results derived from the first multi-chord stellar occultations by the transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, and from a single-chord occultation observed on 2012 October 15. If the timing of the five chords obtained in 2011 were correct, then Quaoar would possess topographic features (crater or mountain) that would be too large for a body of this mass. An alternative model consists in applying time shifts to some chords to account for possible timing errors. Satisfactory elliptical fits to the chords are then possible, yielding an equivalent radius R{sub equiv} = 555 {+-} 2.5 km and geometric visual albedo p{sub V} = 0.109 {+-} 0.007. Assuming that Quaoar is a Maclaurin spheroid with an indeterminate polar aspect angle, we derive a true oblateness of {epsilon}= 0.087{sup +0.0268}{sub -0.0175}, an equatorial radius of 569{sup +24}{sub -17} km, and a density of 1.99 {+-} 0.46 g cm{sup -3}. The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial orbit. Finally, we detect no global atmosphere around Quaoar, considering a pressure upper limit of about 20 nbar for a pure methane atmosphere.},
doi = {10.1088/0004-637X/773/1/26},
url = {https://www.osti.gov/biblio/22140281}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 773,
place = {United States},
year = {Sat Aug 10 00:00:00 EDT 2013},
month = {Sat Aug 10 00:00:00 EDT 2013}
}