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# Program information file
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PROGRAM_ID           2024B027
PROGRAM_TITLE        Stellar occultations by the trans-Neptunian object Quaoar and the Centaur Chiron
PROGRAM_INV1         Amanda Sickafoose
PROGRAM_INV2         Carlos Zuluaga
PROGRAM_INV3         Michael Person
PROGRAM_INV4         Stephen Levine
PROGRAM_INV5          
PROGRAM_SCICAT       Centaurs / TNOs / KBOs
PROGRAM_ABSTRACT_BEG
Stellar occultations are one of the most accurate ground-based methods to measure sizes, shapes, atmospheres, and rings of distant bodies in the Solar System. The capabilities of MORIS+SpeX, combined with Hawaii's unique geographic location, have proven successful for observing stellar occultations by such objects. We propose for 8 hours to observe two predicted stellar occultations, one each by the large TNO [50000] Quaoar and the Centaur [2060] Chiron. A system of two inhomogeneous rings has recently been proposed around Quaoar, detected by only a handful of observations. Even more recent stellar occultations by Chiron indicate that the previously-proposed two-ring system is instead surrounding material that is evolving. Successful observations would characterize the locations and optical depths of rings/surrounding material in the current epoch, detect changes since the last observed occultations, and provide insight into possible activity processes

The UT mid-times for the predicted Quaoar and Chiron events are on August 11 and September 17, respectively. We request 4 hours for each event, to observe [i] at high cadence for +/-20 min centered on the predicted and [ii] long-exposure, calibration frames before and after, when the star and object are well separated.  MORIS will be run with no filter at the fastest cadence that allows for a light-curve signal-to-noise of at least a few tens: for these targets, the resulting integration times are 0.06 sec and 1 sec for the respective events. SpeX will be employed to obtain simultaneous K-band image for both events. Visible data are used to constrain object sizes and atmospheres, as well as the extent and structure of surrounding material. Multi-color data provide an additional level of characterization, through providing insight into [i] particle sizes in atmospheric haze or surrounding material and [ii] nucleus shapes, through central-flash modeling.
PROGRAM_ABSTRACT_END