Actividad cometaria en 2060 Chiron durante un mínimo de brillo

CELLONE, S. A.; SILVA, A. M.

Tafí del Valle

Congreso; 44a. Reunión Anual AAA; 2000

AAA

A decade after its discovery in 1977 and its classification as anasteroid with the number 2060, Chiron began to show evidences ofcometary activity at ~ 13 AU from the Sun. Since then, it has been thetarget of several studies due to its particular orbital andastrophysical behavior, which are unusual both for an asteroid and for acomet. We present here results from direct CCD observations obtainedbetween 1996 and 1998 with the 2.15 m ``Jorge Sahade'' telescope (SanJuan, Argentina). Chiron's absolute magnitude was then very near itshistorical minimum; however, cometary activity was unequivocallydetected from its surface brightness profiles (SBP) as well as directlyfrom co-added images. This sets an upper limit to the nuclear brightnessof this object. Conclusions about the dynamical state of the dust comaare obtained from the analysis of the SBPs slopes, while the possiblegas emission is studied through narrow-band imaging. Integratedphotometry shows a ~ 0.08 mag decline in 1 hour in agreement with therotational light-curve of the nucleus, although its amplitude is largerthan all published values, probably due to a smaller dilution by thecoma.