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Chiron surprises us once again

Presentation #322.11 in the session Comets (Poster)

Published onOct 23, 2023
Chiron surprises us once again

A bright 12.7-mag star was slowly occulted by Chiron on 2022 December 15. We could accurately predict the shadow path on Earth and observe the event, with positive results from two sites. The occultation by the solid body was not detected from the Kottamia Astronomical Observatory in Egypt, but we found three extinction features in the light curve that had symmetrical counterparts with respect to the central time of the occultation. From the Wise observatory in Israel we detected the occultation caused by the main body and several extinction features surrounding the body. When all the secondary features are plotted in the sky plane we find that they can be caused by a broad ~580 km disk with concentrations at radii of 325 ± 16 km and 423 ± 11 km surrounding Chiron. At least one of these structures appears to be outside the Roche limit. The ecliptic coordinates of the pole of the disk are in agreement with the ring pole coordinates proposed in Ortiz et al. (2015) within error bars. But we found considerable more extinction around Chiron than in the past. We also show our own long-term photometry indicating that Chiron had suffered a brightness outburst of at least 0.6 mag sometime between March and September 2021, and that Chiron was still somewhat brighter at the occultation date than at its nominal pre-outburst phase. The outermost extinction features might be consistent with a bound or temporarily bound structure associated with the brightness increase. But the nature of the brightness outburst is unclear, and it is also unclear whether the dust or ice released in the outburst could be feeding a putative ring structure or if it emanated from it.

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