RASNZ Occultation Section - Eurykleia Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (195) EURYKLEIA - 2001 JUNE 28

THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 25 JUNE.

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

The path given by Edwin Goffin crosses central Australia at local sunset to emerge from the New South Wales coastline north of Newcastle and then cross the southern central parts of the North Island of New Zealand. The path given by Occult (against the older TAC star position) lies well to south passing just to the south of Canberra and including Christchurch on the South Island of New Zealand.

UPDATE No. 2: 26 June 2001

This prediction update has been computed by Steve Preston of the Medina, Washington (state) in the United States based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station supplemented with historical data from the AstDys database. The only difference between this update and the previous one is the use of the UCAC star position with Tycho 2 proper motion data. No additional astrometry was used.

Summary:

This update lies around 1.5 path widths to the north of that given by Goffin and the previous update. The path timing is only around 15 seconds later than given by Goffin. The path crosses central Australia at local sunset to cross the New South Wales coastline around Taree (8:51 UT). After crossing the Tasman Sea, the path crosses the central area of the North Island of New Zealand including Taupo and Gisborne (8:53 UT).

The use of the more accurate UCAC star position has reduced the error band on this calculation. Brisbane now stands a better chance of seeing an occultation than Sydney although nether city are likely. In New Zealand, the area of reasonable observation chances would include Auckland, Tauranga, Whakatane and Rotarua (in order of increasing likelihood).

With the event taking place soon after sunset within Australia and the faintness of the target star only eight degrees from a first quarter moon, observers may need to make more effort than usual to identify the target field.

Additional details of this and other events are available at Steve Preston's website at http://www.oz.net/~stevepr/Asteroids/asteroid.htm

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: 28 June 2001 @ 8:52 UT
Magnitude of target star: 11.27
Magnitude drop [mag]: 3.2
Estimated maximum duration [s]: 6.1
Path description: See above.
Goffin's original chart reference: A01_0616

The Occultation Path:

Approximate width [km]: 89
Uncertainty [path widths]: 0.8 (1 sigma error band)
Map: See below
Remarks: Uncertainities are given on the basis of the nominal star position errors and the expected asteroid positional accuracy.
Circles along the path are OCCULT calculated exact centerline points !!!!

Data for the target star:

Name: TYC 4945-00514-1 = TAC -07°06886
Constellation: Virgo
J2000 position [h,m,s; ^o,',"]: 12h 34m 19.171s; -07^o 08' 04.09"
Position source: UCAC1 + Tycho 2 proper motion data
Estimated accuracy ["]: 0.042" (0.030", 0.030")
V mag [mag]: 11.27
Remarks:
The target star is in central Virgo. The star lies 1.5 degree northwest of chi Virginis (magnitude=4.6)

Data for the minor planet:

Number, name: (195) Eurykleia
Approx. diameter [km]: 89.0
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 414
Number of rejected observations: 43
Time covered by the observations: 1905 10 26 - 2001 05 26
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.017", 0.016", 138°.

Data for the event:

UT date and time of least geocentric approach: 2001 June 28, 8:48.3 UT
Approx. V mag of minor planet at event [mag]: 14.39
Geocentric parallax of minor planet ["]: 3.38
Magnitude drop [mag]: 3.2
Estimated maximum duration [s]: 6.1
Apparent motion of minor planet ["/h]: 27.73
Angular distance to moon, phase of moon [deg,%]: 8, 53%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Eurykleia Update

IMPORTANT NOTE!

Astrometric updates such as these should not be taken as definitive, but rather only as an indication of where the true track may lie relative to the original predicted track. Observers must bear in mind that later astrometry, in which the target star is measured in the same field as the asteroid, may still reveal substantial changes to the predicted track and time of the event. For this reason it is most important that observers far from the predicted track still monitor the event.

Use these links for further information:
[Planetary Occultations] [Using the Predictions]
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[Asteroid Occultation Results]

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