Occultation of 10th-mag. star by Hektor, the largest Trojan, 2019 August 27/28 - New 2019 August 23

This is an important Lucky Star trans-Atlantic event by a large probable contact-binary asteroid

The detailed prediction for this occultation, including small-scale maps of the path across 
southern Europe and North America, is here. It also includes finder charts of different 
scales locating the target star, TYC 5246-00764-1 at J2000 RA 23h 19m 11.2s, Dec -2 deg. 40'
31".  Note that the path will be wider (by at least 50 km both north and south) than Preston 
indicates because it is a very elongated object, about 200 by 400 km. A shape model of the 
event at the time of the occultation is here (thanks, Roger Venable), but it does not include 
probable concavities that would show its probable contact binary nature; occultation 
observations will be valuable for that. Besides being a probable contact binary, Hektor has 
a known moon, Skamandrios, approximately 12 km in diameter (it could occult the star for about 
a second) in an orbit several hundred km from Hektor, so observers throughout the USA and 
Europe are encouraged to try to observe this occultation.

The Hipparcos mission, with their Tycho catalog observations, showed that the star is double,
with component magnitudes 10.7 and 10.8, separation 0.56" in PA 192.7 deg. in 1991. But higher
resolution Gaia observations don't seem to show duplicity, writes Paolo Tanga, who has looked 
at the Gaia scan observations. So the star is likely not double, but we can't be positive of 
that, with the fairly definite Tycho observations. If the star is double, then instead of a 
4-mag. drop if an occultation occurs, it will be only about 0.7 mag. And if the star is double, 
then the small accuracy of the Gaia prediction will be out the window, and the path for one of 
the components could be much farther north (and south) of Preston's predicted path. For this 
reason, I plan to observe from Maryland, although chances for an event are small. On 2015 Oct 24,
Dave Herald recorded a lunar occultation of the star (it's X 53313 in the Occult XZ80Q catalog)
that may or may not show duplicity; Felipe Ribas doesn't think so. Here is Dave Herald's light 
curve of the 2015 occultation, from the Vizier occultation light curve archive.  The AAVSO 
APASS says the star's V mag. is 10.0, so maybe the 10.7 mag. given by Gaia refers to 
one of the components of the double??

More information about this event is in this "IOTA/Lucky Star" campaign Word file.
The Lucky Star page for the event is here. Felipe Ribas writes about this event in this Word file.

Current cloud cover forecasts for the event look poor for North America (the south Texas coast 
seems to have the best prospects, which is unusual) but very good for southern Europe.

David Dunham, 2019 August 23
e-mail:  dunham@starpower.net
cell phone:  301-526-5590