Stellar occultations by TNOs: the January 08, 2011 by (208996) 2003 AZ84 and the May 04, 2011 by (50000) Quaoar

F. BRAGA-RIVAS, B. SICARDY, J. L. ORTIZ, E. JEHIN, J, CAMARGO, M. ASSAFIN, R. BEHREND, E. UNDA-SANZANA, J. P. COLQUE, N. MORALES, G. TANCREDI, S. ROLAND, S. BRUZZONE, R. SALVO, L. ALMENARES, M. EMILIO, W. SCHOENELL, R. GIL-HUTTON, A. MILONE, Y OTROS

Nantes

Congreso; EPSC-DPS Joint Meeting 2011; 2011

Europlanet

Between February 2010 and May 2011, our group hasobserved five stellar occultations by Trans-NeptunianObjects (TNOs), giving the size and shape for some ofthe biggest TNO’s: Varuna, Eris, 2003 AZ84, Makemakeand Quaoar. Here we present two of them: theJanuary 08 stellar occultation by 2003 AZ84, and theMay 04 by Quaoar. For the event of 2003 AZ84 weobtained one positive and another negative occultationchords in Chile. We give a lower limit to the diameterof the TNO. The event of Quaoar was observedfrom 16 sites distributed in Uruguay, Argentina, Chileand Brazil. Five of them yielded positive detectionof the occultation. A preliminary analysis shows thatthe body is probably elongated and significantly biggerthan the size determined by Fraser & Brown 2010,with a diameter of 890km. Using the size determinedby the occultation, we will discuss the implications forthe body density and albedo determination. The upperlimit of the atmosphere is also studied.