From: Thomas WidemannTo: Leslie Young , Eliot Young , Amanda Gulbis , "James E. Elliot" , "Jay M. Pasachoff" , Mike Person , "Marc W. Buie" , Cathy Olkin , David Tholen , Richard French , Wolf Juergen , Ted Dunham , Michael Brown Cc: Bruno Sicardy Subject: Nix alert, March 4 Date: Sat, 28 Feb 2009 01:13:28 +0100 Nix alert, March 4 On March 4,13:56:01 UT, Nix might occult a V = 12.6, I = 11.5 star, an event visible in Hawaii. Time is for geocentric closest approach (C/A), note that the actual event would occur 5 minutes earlier in Hawaii. The maximum duration is about 5 s (relative velocity 15.69 km s-1). The star J2000.0 coordinates are 18 12 09.86 -17 42 03.3. We have used Dave Tholen's update position of Nix 1.5849 arcsec west and 0.8499 arcsec north of Pluto at time of the event, i.e. +9 mas (east) and -6 mas (south) to JPL Horizons ephemeris. We have also improved Pluto's offset wrt DE413, using a linear fit to astrometric reconstruction of occultations from 2005 to 2008 : Delta alpha = - 87 mas Delta delta = + 146 mas Our resulting prediction attached is close to the previous one due to compensation in Pluto's and Nix' offset corrections. It is however about 25 seconds EARLIER than previously posted, the event central time is now 13:50:37 UT (in Hawaii). Estimated error bar is ± 30 sec in time and ± 500 km N-S. A probability of about 10 percent for a positive event can be assessed. This is the best probability we can obtain considering our cumulated error bars on star position and Pluto's offset, and Dave's Nix Plutocentric ephemeris. With this in mind, we would again stress this is an unusually "bright" event combined with a rare geometry across the state of Hawaii. Even visual observations using a 12" telescope and a timing device would be useful. Beyond large facilities on Mauna Kea and Haleakala who would be willing to consider observing the event, additional observers you may contact should spread over the islands to as many different locations as possible. -Thomas
Telescope Approx. Location Cameras Contact Windward community college 16" Kaneohe, Oahu visual Dave Tholen (observer) PanSTARRS Haleakala, Maui Dave Tholen AEOS 3.67-m Haleakala, Maui Dave Tholen Faulkes Haleakala, Maui Jay Pasachoff IRTF 3.0-m Mauna Kea, Hawaii POETS Amanda Gulbis CFHT Mana Kea, Hawaii MegaCam Guide Camera Bruno Sicardy
Star Positions
Using the star positions measured by the Brazil group as the reference position, we find
Source RA Dec dra ddec errx erry -------------- -------------- ------------- ----- ------- ---- ---- Brazil 18:12:09.8612 -17:42:03.225 UCAC2_2006 18:12:09.8653 -17:42:03.229 59 -4 42 42 -------------------------------------------------------------------RA and Dec are epoch of date (where proper motion is known), equinox J2000.
Brazil - Brazilian astrometric group that Bruno Sicardy and co. are working with.
UCAC2-2006: the position remeasured with the UCAC2 telescope in 2006, provided by Norbert Zacharias. This catalog is available here .
10 arcmin FOV | 5 arcmin FOV | 2 arcmin FOV |