Fwd: Large TNO occultation possible in Americas Feb. 10/11
- Begin forwarded message:
> From: David Dunham <dunham@...>[Non-text portions of this message have been removed]
> Date: February 5, 2008 11:45:17 PM MST
> Subject: Large TNO occultation possible in Americas Feb. 10/11
> Observers throughout the Americas, and even westernmost Europe,
> have a chance to observe an occultation of an 11.3-mag. star in
> Gemini by the large (maybe even 1000 km) distant trans-Neptunian
> object (TNO) 20000 Varuna on Sunday night, Feb. 10/11. Observers in
> South America are especially encouraged to try to observe this
> event since they have the highest probability for an occultation.
> The nominal path misses the Earth to the south, but the real
> uncertainties in the prediction are hard to access, as Steve
> Preston notes, so there is a chance for an event even in North
> America. Occultations of stars this bright by such large TNO's
> are quite rare, and so far, none beyond Pluto/Charon have been
> observed. Even if an occultation by Varuna doesn't occur, there
> could be an occultation by a possible satellite of Varuna.
> The closest approach time is 4:26 UT of Feb. 11 UT in South
> America, and about 4:30 UT in North America. The formal
> 1-sigma uncertainty in the time is about 5 min., but you should
> be prepared for at least a 3-sigma event; I would recommend
> monitoring/recording the star for at least 20 min. before and
> after the predicted time for your station. If an occultation
> occurs, there will be a 9-mag. drop lasting about 43 seconds
> for a central event. The star to be occulted is TYC 1913-00670-1
> at J2000 RA 7h 18m 50.1s, Dec +25 deg. 43' 19", 2.5 deg. s.s.w.
> of 5th-mag. iota Geminorum and 1.3 deg. w.n.w. of 6th-mag.
> 57 Geminorum. Detailed finder charts of different scales are
> on Steve Preston's Web site for the event at
> http://www.asteroidoccultation.com/2008_02/0211_20000_16750.htm ;
> it also has a view of the Earth as seen from Varuna that can
> be used to estimate your time of closest approach, and altitude
> above your horizon.
> Please spread word of this event; good luck with your observation!
> David Dunham, IOTA
>> ...occultation of an 11.3-mag. star...This star is somewhat fainter than this. The TASS MkIV data shows
V = 11.94 +/- 0.04. The Carlsberg meridian circle catalogue gives
Sloan r' = 11.74. The ASAS-3 database shows mean V = 11.91 +/- 0.05,
consistent with the TASS mean value (n=15 observations for TASS versus
n=11 for ASAS-3).