The Occultation of an 11.5 Star by Trojan binary asteroid Hektor

Fri morning Feb 21, 2025 at 5:01:57am

OWc page , and LuckyStar page

 

This event is low probability. It's decently high probability if you drive to Nevada, but this event was advertised too late to try and plan for such an expedition. As it turns out, it looks to be clear and decent weather and might have been do-able as a van trip. But - too late.

However, it has a moon which is well within the possibility of seeing. Odds are still low, but we're only 1 asteroid diameter away and within the moonlet's orbit.

Alt=24, Az=272, so this is not visible from my carport. Will have to get up and drive somewhere.

Somewhere I saw something about the satellite, Skamandrios, being ~12 km dia. I think that came from https://en.wikipedia.org/wiki/624_Hektor#Satellite , which seems to have come from

[7] Marchis, F.; Durech, J.; Castillo-Rogez, J.; Vachier, F.; Cuk, M.; Berthier, J.; et al. (March 2014). "The Puzzling Mutual Orbit of the Binary Trojan Asteroid (624) Hektor". The Astrophysical Journal Letters783 (2): 6. arXiv:1402.7336Bibcode:2014ApJ...783L..37Mdoi:10.1088/2041-8205/783/2/L37S2CID 19868908.

So, as usual, the size estimate seems like it’s most likely based on albedo assumptions, for which occultation observations would be especially valuable (single chords can only really put a lower bound on size), not to mention refining Skamandrios’ orbit, which will in turn constrain estimates of system total mass.

Looking at RECON’s updated listing at
https://www.boulder.swri.edu/~buie/recon/trojans/RECON_plan.html , and event details at
https://www.boulder.swri.edu/~buie/recon/trojans/624_Hektor_20250221130547.html
the list of RECON stations for Hektor itself have been reduced to fewer sites: (Chiloquin, Klamath Falls, Cedarville); Cedarville CA is near Alturas, in the NE corner of CA.

For additional reference for event planning, see also:
https://cloud.occultwatcher.net/event/1512-624-145362-649002-T01221-1
(Tom Heisey’s signed up, 1 sigma inside the south edge of the OWC path! The OWC path is a little south of the LuckyStar path. Good luck with the twilight, Tom!),
and
https://cloud.occultwatcher.net/event/1512-624-145362-649002-T01221-1/2172520

But those don’t speak to the path of Skamandrios, other than that we think (Wikipedia again) its orbit is
Semi-major axis 623.5±10 km
Eccentricity 0.31±0.03 based on [7].
As a rough comparison, it’s ~584 km from Klamath Falls to, say, Cabrillo Observatory, so it’s worth a shot. To the north, 623 km from Klamath Falls is north of Wenachee, WA (the actual normal to the path is somewhat more- I was just snapping a line in Google Earth).
The uncertainties for Skamandrios are so large that travel for it alone don’t pencil out (pending any updated information- I need to get into Occult and see if Miriade has any advice to offer. I couldn’t figure out how to query Miriade using the web interface, though I’m sure it’s simple).

Skamandrios event duration: If Hektor is ~181 km dia, Skamandrios is ~12 km dia, and Hektor’s max duration is 10.1 sec, a maximum duration for Skamandrios might be on the order of 0.67 sec. The event combined magnitude is 11.5 m, mag drop 2.0-2.69. If my scribblings are correct, a Skamandrios event should be “well within reach” of our usual 8” apertures.
-Ted

 

         

 

Results:

Clouded out. Heavy cirrus came in. Kirk tried, maybe got something through the clouds? I ended up scrubbing the effort.