Today, we are issuing our IAU Circular describing the moon shadows. It will read something like this:
Mutual Events of 2003 EL 61 and its Inner Satellite
Daniel Fabrycky (Harvard University), Darin Ragozzine & Michael Brown (California Institute of Technology) and Matthew Holman (Smithsonian Astrophysical Observatory)
Orbital fits to the relative astrometric positions of dwarf planet 2003 EL61 (IAUC 8577) and its inner satellite, S/2005 (2003 EL_61) 2 (IAUC 8636), have revealed a near edge-on orbit, implying likely mutual events. The orbital model was based on images from HST (WFPC2) and Keck (LGS-AO). Due to the changing orientation of the Earth-EL_61 line of sight, the orbit is moving closer to edge-on until August 2008, after which the orbit will open up again. The current distance of closest projected approach is ~500 km, nearly the same as the semi-minor axis of the triaxial primary (Rabinowitz et al. 2005, ApJ, 639, 1238), so events will likely be grazing. Shadows of the satellite and EL_61 will likely miss each other. The unocculted lightcurve has double-peaked rotational modulation of full amplitude 0.25 mag and period 3.9 hours; template lightcurves of this variation are available from Holman. The duration of the events will be between 0 and ~6 hours; ingress and egress will consist of ~0.03 magnitude changes on a timescale of ~10 minutes. Telescopes distributed in longitude are needed to follow events as the orbital period is 18.36 d. The main body is rather faint (V~17.4 mag), so high-precision photometry requires moderate (~1 m) collecting area.
Due to orbital eccentricity, events in which the main body occults the satellite are more likely to occur than events in which the satellite occults the main body. Our orbital model predicts mid-event times as follows (add or subtract up to 3 hours for ingress or egress times).
For the satellite occulting the main body:
HJD 2454617.58 +/- 0.07 = 5/31 01:50+/-1:40 UT
HJD 2454635.84 +/- 0.07
HJD 2454654.11 +/- 0.07
HJD 2454672.48 +/- 0.08
For the main body occulting the satellite:
HJD 2454625.22 +/- 0.07 = 6/07 17:10+/-1:40 UT
HJD 2454643.45 +/- 0.07
HJD 2454661.79 +/- 0.1
What does all of this mean? First, a little sadness. We missed most of the shadows by a few years. There is only a chance to observe about 3 more this year, and then not again for 130 years.
The next event is visible over Asian/Europe, but we think it is likely to just be a graze, so nothing will be clear. After that we are on to Hawaii and Japan again for June 7th.
Honestly, I think we're too late. But what a great project it will be for our great-great-great-grandkids.