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

Journal Article · Sat Aug 10 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/773/1/26· OSTI ID:22140281

Braga-Ribas, F.; Vieira-Martins, R.; Camargo, J. I. B. ^[1]; Sicardy, B.; Lellouch, E.; Lecacheux, J. ^[2]; Ortiz, J. L.; Morales, N. ^[3]; Tancredi, G.; Roland, S.; Bruzzone, S. ^[4]; Assafin, M. ^[5]; Behrend, R. ^[6]; Vachier, F.; Colas, F. ^[7]; Maury, A. ^[8]; Emilio, M. ^[9]; Amorim, A. ^[10]; Unda-Sanzana, E. ^[11]; others, and

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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)

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.

• OSTI ID: 22140281
• Journal Information: Astrophysical Journal, Vol. 773, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ALBEDO
DENSITY
ECLIPSE
MASS
METHANE
ORBITS
PLANETS
SATELLITE ATMOSPHERES
SATELLITES
SPHEROIDS
STARS
U QUARKS