Browsing by Author "Morgado, B. E."

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Physical properties of Centaur (60558) 174P/Echeclus from stellar occultations
    (2024) Pereira, C. L.; Braga-Ribas, F.; Sicardy, B.; Gomes-Junior, A. R.; Ortiz, J. L.; Branco, H. C.; Camargo, J. I. B.; Morgado, B. E.; Vieira-Martins, R.; Assafin, M.; Benedetti-Rossi, G.; Desmars, J.; Emilio, M.; Morales, R.; Rommel, F. L.; Hayamizu, T.; Gondou, T.; Jehin, E.; Artola, R. A.; Asai, A.; Colazo, C.; Ducrot, E.; Duffard, R.; Fabrega, J.; Fernandez-Valenzuela, E.; Gillon, M.; Horaguchi, T.; Ida, M.; Kitazaki, K.; Mammana, L. A.; Maury, A.; Melita, M.; Morales, N.; Moya-Sierralta, C.; Owada, M.; Pollock, J.; Sanchez, J. L.; Santos-Sanz, P.; Sasanuma, N.; Sebastian, D.; Triaud, A.; Uchiyama, S.; Vanzi, L.; Watanabe, H.; Yamamura, H.
    The Centaur (60558) Echeclus was discovered on 2000 March 03, orbiting between the orbits of Jupiter and Uranus. After exhibiting frequent outbursts, it also received a comet designation, 174P. If the ejected material can be a source of debris to form additional structures, studying the surroundings of an active body like Echeclus can provide clues about the formation scenarios of rings, jets, or dusty shells around small bodies. Stellar occultation is a handy technique for this kind of investigation, as it can, from Earth-based observations, detect small structures with low opacity around these objects. Stellar occultation by Echeclus was predicted and observed in 2019, 2020, and 2021. We obtain upper detection limits of rings with widths larger than 0.5km and optical depth of tau = 0.02. These values are smaller than those of Chariklo's main ring; in other words, a Chariklo-like ring would have been detected. The occultation observed in 2020 provided two positive chords used to derive the triaxial dimensions of Echeclus based on a 3D model and pole orientation available in the literature. We obtained a = 37.0 +/- 0.6km, b = 28.4 +/- 0.5km, and c = 24.9 +/- 0.4km, resulting in an area-equivalent radius of 30.0 +/- 0.5km. Using the projected limb at the occultation epoch and the available absolute magnitude (), we calculate an albedo of p(v) = 0.050 +/- 0.003. Constraints on the object's density and internal friction are also proposed.
  • No Thumbnail Available
    Item
    Refined physical parameters for Chariklo's body and rings from stellar occultations observed between 2013 and 2020
    (2021) Morgado, B. E.; Sicardy, B.; Braga-Ribas, F.; Desmars, J.; Gomes-Junior, A. R.; Berard, D.; Leiva, R.; Ortiz, J. L.; Vieira-Martins, R.; Benedetti-Rossi, G.; Santos-Sanz, P.; Camargo, J. I. B.; Duffard, R.; Rommel, F. L.; Assafin, M.; Boufleur, R. C.; Colas, F.; Kretlow, M.; Beisker, W.; Sfair, R.; Snodgrass, C.; Morales, N.; Fernandez-Valenzuela, E.; Amaral, L. S.; Amarante, A.; Artola, R. A.; Backes, M.; Bath, K. -L.; Bouley, S.; Buie, M. W.; Cacella, P.; Colazo, C. A.; Colque, J. P.; Dauvergne, J. -L.; Dominik, M.; Emilio, M.; Erickson, C.; Evans, R.; Fabrega-Polleri, J.; Garcia-Lambas, D.; Giacchini, B. L.; Hanna, W.; Herald, D.; Hesler, G.; Hinse, T. C.; Jacques, C.; Jehin, E.; Jorgensen, U. G.; Kerr, S.; Kouprianov, V.; Levine, S. E.; Linder, T.; Maley, P. D.; Machado, D. I.; Maquet, L.; Maury, A.; Melia, R.; Meza, E.; Mondon, B.; Moura, T.; Newman, J.; Payet, T.; Pereira, C. L.; Pollock, J.; Poltronieri, R. C.; Quispe-Huaynasi, F.; Reichart, D.; de Santana, T.; Schneiter, E. M.; Sieyra, M. V.; Skottfelt, J.; Soulier, J. F.; Starck, M.; Thierry, P.; Torres, P. J.; Trabuco, L. L.; Unda-Sanzana, E.; Yamashita, T. A. R.; Winter, O. C.; Zapata, A.; Zuluaga, C. A.
    Context. The Centaur (10199) Chariklo has the first ring system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow sizes and shapes to be determined with kilometre accuracy, and provide the characteristics of the occulting object and its vicinity.
  • No Thumbnail Available
    Item
    Size and Shape of Chariklo from Multi-epoch Stellar Occultations
    (2017) Leiva, R.; Sicardy, B.; Camargo, J. I. B.; Ortiz, J. -L.; Desmars, J.; Berard, D.; Lellouch, E.; Meza, E.; Kervella, P.; Snodgrass, C.; Duffard, R.; Morales, N.; Gomes-Junior, A. R.; Benedetti-Rossi, G.; Vieira-Martins, R.; Braga-Ribas, F.; Assafin, M.; Morgado, B. E.; Colas, F.; De Witt, C.; Sickafoose, A. A.; Breytenbach, H.; Dauvergne, J. -L.; Schoenau, P.; Maquet, L.; Bath, K. -L.; Bode, H. -J.; Cool, A.; Lade, B.; Kerr, S.; Herald, D.
    We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo's size and shape, and the ring reflectivity. We consider four possible models for Chariklo (sphere, Maclaurin spheroid, triaxial ellipsoid, and Jacobi ellipsoid), and we use a Bayesian approach to estimate the corresponding parameters. The spherical model has a radius R = 129 +/- 3 km. The Maclaurin model has equatorial and polar radii a = b = 143(-6)(13) km and = c 96(-4)(+14) km respectively, with density 970(-180)(+300) kg m(-3). The ellipsoidal model has semiaxes = a 148(-4)(+6) km and c = 102(-8)(+10) km Finally, the Jacobi model has semiaxes a = 157 +/- 4 km, b = 139 +/- 4 km, and c = 86 +/- 1 km, and density 796(-4)(+2) kg m(-3) Depending on the model, we obtain topographic features of 6-11 km, typical of Saturn icy satellites with similar size and density. We constrain Chariklo's geometric albedo between 3.1% (sphere) and 4.9% (ellipsoid), while the ring I/F reflectivity is less constrained between 0.6% (Jacobi) and 8.9% (sphere). The ellipsoid model explains both the optical light curve and the long-term photometry variation of the system, giving a plausible value for the geometric albedo of the ring particles of 10%-15%. The derived mass of Chariklo of 6-8 x 10(18) kg places the rings close to 3:1 resonance between the ring mean motion and Chariklo's rotation period.