During the wee small hours of Sunday morning, a certain occultation obsessive decided to be the first person ever to witness an event involving the 12.8 magnitude asteroid 32 Pomona. It was a pretty unlikely event – low probability and during a full moon. Fortified by red wine, he toughed it out and was rewarded by a very strange happening (insert joke here). http://www.youtube.com/watch?v=ZctDMdF52hU
Graze occultations happen every now and then and Jonathan got lucky to see this ‘double flasher’. The occultation community has got a little animated at the thought of this unusual object, and the following CBET (Central Bureau Electronic Telegram) is planned to go out to the pro observatories:
32 Pomona. David Herald (International Occultation Timing Association) reports that Jonathan Bradshaw (Samford, Queensland, Australia) recorded an unusual occultation by the asteroid 32 Pomona on 2008 August 16. The expected maximum duration of the occultation was 7.1 secs.
The video recording shows two separate occultations of equal depth each lasting 1.2 seconds, separated by 0.8 secs. Those durations convert to chord lengths at the asteroid of 15km, 10km, and 15km - for a total length of 40km. The IRAS diameter for Pomona is 86.3km A possible explanation is that the star (UCAC2 38196247) is a double star with a separation of about 0.013".
However the equal duration of the two occultations combined with the geometry of the occultation would require the PA of the components to very closely match the direction of motion of the asteroid. This, together with the equal depth of the occultations, indicates that the double star explanation is unlikely. The most likely explanation is that the asteroid is either binary (including a contact binary), or is a unitary asteroid with a significant concave region on its surface.
The video of this occultation can be viewed at: http://www.youtube.com/watch?v=ZctDMdF52hU
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