Title: Study of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic features Author: A. Dias-Oliveira, B. Sicardy, J. L. Ortiz, F. Braga-Ribas, R. Leiva, R. Vieira-Martins, G. Benedetti-Rossi, J. I. B. Camargo, M. Assafin, A. R. Gomes-Junior, T. Baug, T. Chandrasekhar, J. Desmars, R. Duffard, P. Santos-Sanz, Z. Ergang, S. Ganesh, Y. Ikari, P. Irawati, J. Jain, Z. Liying, A. Richichi, Q. Shengbang, R. Behrend, Z. Benkhaldoun, N. Brosch, A. Daassou, E. Frappa, A. Gal-Yam, R. Garcia-Lozano, M. Gillon, E. Jehin, S. Kaspi, A. Klotz, J. Lecacheux, P. Mahasena, J. Manfroid, I. Manulis, A. Maury, V. Mohan, N. Morales, E. Ofek, C. Rinner, A. Sharma, S. Sposetti, P. Tanga, A. Thirouin, F. Vachier, T. Widemann, A. Asai, Hayato Watanabe, Hiroyuki Watanabe, M. Owada, H. Yamamura, T. Hayamizu, J. Bradshaw, S. Kerr, H. Tomioka, S. Andersson, G. Dangl, T. Haymes, R. Naves, G Wortmann
We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ84, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ84's shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semi axes (470±20) x (383±10) x (245±8) km % axis ratios b/a=0.82±0.05 and c/a=0.52±0.02, can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75~h) and the amplitude of its rotation light curve, we derive a density /rho=0.87±0.01g cm^-3 a geometric albedo pV=0.097±0.009. A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003~AZ84's limb, that can be interpreted as an abrupt chasm of width ~23 km and depth >8 km or a smooth depression of width ~80 km and depth ~13 km (or an intermediate feature between those two extremes).
Kuiper Belt Object (208996) 2003 AZ84, also written as 2003 AZ84, is a plutino, like Pluto, in a 2:3 resonance with Neptune. It is very likely a dwarf planet. It was discovered on January 13, 2003 by C. Trujillo and M. Brown using the Samuel Oschin telescope in the Palomar Observatory. Light-curve-amplitude analysis shows only small deviations, suggesting that 2003 AZ84 is a spheroid with small albedo spots and hence a dwarf planet. Read more