The Size, Shape, Albedo, Density, and Atmospheric Limit of Transneptunian Object (50000) Quaoar From Multi-Chord Stellar Occultations

Braga-Ribas, F.; Sicardy, B.; Ortiz, J. L.; Lellouch, E.; Tancredi, G.; Lecacheux, J.; Vieira-Martins, R.; Camargo, J. I. B.; Assafin, M.; Behrend, R.; Vachier, F.; Colas, François; Morales, N.; Maury, A.; Emílio, M.; Amorim, A.; Unda-Sanzana, E.; Roland, S.; Bruzzone, Juan Sebastián; Almeida, L. A.; Rodrigues, C. V.; Jacques, C.; Gil-Hutton, R.; Vanzi, L.; Milone, A.; Schoenell, W.; Salvo, R. De; Almenares, L.; Jehin, Emmanuël; Manfroid, Jean; Sposetti, S.; Tanga, P.; Klotz, A.; Frappa, Eric; Cacella, P.; Colque, J. P.; C., Neves,; Alvarez, Eduardo Manuel; Gillon, M.; Pimentel, E.; Giacchini, Breno L.; Roques, F.; Widemann, Thomas; Magalhaes, Victor; Thirouin, A.; Duffárd, R.; Leiva, Rodrigo; Toledo, I.; Capeche, J.; Beisker, W.; Pollock, J.; Montaña, C. E. Cedeño; Ivarsen, K.; Reichart, D.; Haislip, J.; Lacluyzé, A.

doi:10.1088/0004-637x/773/1/26

Cited by 85 publications

(61 citation statements)

References 37 publications

(70 reference statements)

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“…It appears to be a particularly fascinating object in the outer solar system with an estimated density of 1.99 ± 0.46 g cm −3 derived from the first multi-chord stellar occultations by Braga-Ribas et al (2013), which is significantly lower than the one proposed by Fraser et al (2013a), and it agrees with the determination by Fornasier et al (2013) estimated on the basis of the new Herschel far-IR data.…”

Section: Introductionsupporting

confidence: 80%

“…Braga-Ribas et al (2013) reported a preferred solution for the effective diameter of 1111 ± 5 km obtained from a multichord stellar occultation. The size of (50000) Quaoar is comparable to Pluto's moon Charon.…”

Section: Introductionmentioning

confidence: 99%

“…With their observations of Quaoar at a close passage with a background star, Fraser et al (2013b) do not find indication of an isothermal N 2 or CO atmosphere, but could not rule out the possibility of a tenuous CH 4 atmosphere. Braga-Ribas et al (2013) set an upper limit of about 20 nbar surface pressure for a global atmosphere of pure methane from multi-chord stellar occultations by Quaoar, but they did not exclude a local, denser atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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(50000) Quaoar: Surface composition variability

Barucci

Ore

Perna

et al. 2015

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Aims. The goal of this work is to investigate the composition of the surface of (50000) Quaoar and its spatial variability. Methods. We present new continuous spectra from the visible to near-IR (0.3−2.3 μm) obtained with the X-Shooter instrument at the VLT-ESO at four different epochs on the surface of Quaoar. The data represent the highest spectral resolution data ever obtained for this object and the first near-IR dataset acquired in a single exposure over the entire wavelength range. They are complemented by previously published photometric observations obtained in the near-IR (3.6, 4.5 μm) with the Spitzer Space Telescope, which provide an extra set of constraints in the model calculation. Spectral modelling was performed for the entire wavelength range by means of a code based on the Shkuratov radiative transfer formulation and of an updated value of albedo obtained from recent Herschel observations. Results. We obtained compositional information for different observed areas that can cover about 40% of the assumed rotational period of 8.84 h. Our analysis helps to prove the presence of CH 4 and C 2 H 6 , as previously reported, along with indications of the possible presence of NH 3 ·H 2 O. New evidence of N 2 is inferred from the shift in the CH 4 bands. The albedo at the two Spitzer bands suggests there may be CO diluted in N 2 , and CO 2 for one of the surface locations. Conclusions. The spectral similarities indicate the overall homogeneity of the surface composition of one hemisphere of Quaoar, while some subtle variations are apparent when modelling. The presence of NH 3 ·H 2 O would support the idea that Quaoar's surface may be relatively young.

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Section: Introductionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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(50000) Quaoar: Surface composition variability

Barucci

Ore

Perna

et al. 2015

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“…Then, we compare our results as well as our technique for deriving this information from the light curve with other methods. In fact, the density, albedo and/or sizes of both components can also be obtained from other methods, such: i) thermal or thermophysical modeling based on data obtained, for example, with the Herschel Space Observatory or the Spitzer Space Telescope Stansberry et al 2008); ii) from the mutual orbit of the binary component Brown et al 2010); iii) from direct imaging (Brown & Trujillo 2004), or iv) from stellar occultation by (B)TNOs (Sicardy et al 2011;Braga-Ribas et al 2013). However, these methods only provide some information which requires the complement of other techniques.…”

Section: Derived Properties From Light Curves Of Binary/multiple Systemsmentioning

confidence: 99%

Rotational properties of the binary and non-binary populations in the trans-Neptunian belt

Thirouin

Noll

Ortiz

et al. 2014

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We present results for the short-term variability of binary trans-Neptunian objects (BTNOs). We performed CCD photometric observations using the 3.58 m Telescopio Nazionale Galileo (TNG), the 1.5 m Sierra Nevada Observatory (OSN) telescope, and the 1.23 m Centro Astronómico Hispano Alemán (CAHA) telescope at Calar Alto Observatory. We present results based on five years of observations and report the short-term variability of six BTNOs. Our sample contains three classical objects: (174567) We also derived some physical properties from their light curves, such as density, primary and secondary sizes, and albedo. We compiled and analyzed a vast light curve database for TNOs including centaurs to determine the light-curve amplitude and spin frequency distributions for the binary and non-binary populations. The mean rotational periods, from the Maxwellian fits to the frequency distributions, are 8.63 ± 0.52 h for the entire sample, 8.37 ± 0.58 h for the sample without the binary population, and 10.11 ± 1.19 h for the binary population alone. Because the centaurs are collisionally more evolved, their rotational periods might not be so primordial. We computed a mean rotational period, from the Maxwellian fit, of 8.86 ± 0.58 h for the sample without the centaur population, and of 8.64 ± 0.67 h considering a sample without the binary and the centaur populations. According to this analysis, regular TNOs spin faster than binaries, which is compatible with the tidal interaction of the binaries. Finally, we examined possible formation models for several systems studied in this work and by our team in previous papers.

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“…We provide ephemerides of TNO/Centaurs usable with SPICE library and available at http://www.imcce.fr/~desmars/ research/tno/ The offset observations of the selected TNOs are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A96 Affiliated researcher at Observatoire de Paris/IMCCE, 77 avenue Denfert Rochereau 75014 Paris, France accuracy (Elliot et al 2010;Sicardy et al 2011;Ortiz et al 2012;Braga-Ribas et al 2013) from the resulting light curves of ground-based observers located inside the shadow path or just outside it. This level of accuracy in dimensions can only be rivaled by space missions.…”

Section: Introductionmentioning

confidence: 99%

Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations

Desmars

Camargo

Braga-Ribas

et al. 2015

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Context. The prediction of stellar occultations by trans-Neptunian objects (TNOs) and Centaurs is a difficult challenge that requires accuracy both in the occulted star position and in the object ephemeris. Until now, the most used method of prediction, involving dozens of TNOs/Centaurs, has been to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris, usually the latest public version. This offset is determined as the difference between the most recent observations of the TNO/Centaur and the reference ephemeris. This method can be successfully applied when the offset remains constant with time, i.e. when the orbit is stable enough. In this case, the prediction even holds for occultations that occur several days after the last observations. Aims. This paper presents an alternative method of prediction, based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database, as well as sets of new astrometric positions from unpublished observations. Methods. Orbits were determined through a numerical integration procedure called NIMA, in which we developed a specific weighting scheme that considers the individual precision of the observation, the number of observations performed during one night by the same observatory, and the presence of systematic errors in the positions. Results. The NIMA method was applied to 51 selected TNOs and Centaurs. For this purpose, we performed about 2900 new observations in several observatories (European South Observatory, Observatório Pico dos Dias, Pic du Midi, etc.) during the 2007-2014 period. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between July 2013 and February 2015. By comparing the NIMA and Jet Propulsion Laboratory (JPL) ephemerides, we highlight the variation in the offset between them with time, by showing that, generally, the constant offset hypothesis is not valid, even for short time scales of a few weeks. Giving examples, we show that the constant offset method cannot accurately predict 6 out of the 13 observed positive occultations that have been successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refining the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to refine the orbit of the TNO and, consequently, the future predictions. We also provide unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.

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The Size, Shape, Albedo, Density, and Atmospheric Limit of Transneptunian Object (50000) Quaoar From Multi-Chord Stellar Occultations

Cited by 85 publications

References 37 publications

(50000) Quaoar: Surface composition variability

(50000) Quaoar: Surface composition variability

Rotational properties of the binary and non-binary populations in the trans-Neptunian belt

Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations

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