RASNZ Occultation Section - Vindobona Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (231) VINDOBONA - 2001 MAY 8

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

Goffin's path crosses the Cape York peninsula in the area of Princess Charlotte Bay and the Gulf of Carpentaria around Groote Eylandt. The Occult path is virtually identical although around three minutes later.

UPDATE: 5 May 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 and AstDys sources. The Tycho-2 position of the target star has been used.

Summary:

This updated path lies around 3.5 path width to the south of that given by Edwin Goffin and around 4 minutes later. The path crosses northern Vanuatu (13:40 UT). The path then crosses the east Queensland coast in the Ingham area (13:48:30 UT), running to the north of Mount Isa (13:51 UT) and close to Tennant Creek (13:53 UT). The path then runs on to leave the Western Australian coastline in the Derby/King Sound area (13:56 UT).

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: May 8, 2001 @ 13:50 UT
Magnitude of target star: 9.92
Magnitude drop [mag]: 3.1
Estimated maximum duration [s]: 22.4
Path description: See above.
Goffin's original chart reference: A01_0508

The Occultation Path:

Approximate width [km]: 90
Uncertainty [path widths]: 0.9 (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 7379-00148-1 = PPM 748986
Constellation: Scorpius
J2000 position [h,m,s; ^o,',"]: 17h 41m 16.899s; -31^o 10' 15.90"
Position source: Tycho - 2
Estimated accuracy ["]: 0.028" (0.019", 0.021")
V mag [mag]: 9.92
B-V [mag]: +0.155
Remarks:
The target star is in north eastern Scorpius. The target star is just over a degree north-northeast of the bright open cluster Messier 6 (commonly refered to as the Butterfly Cluster).

Data for the minor planet:

Number, name: (231) Vindobona
Approx. diameter [km]: 85.1
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 287
Number of rejected observations: 36
Time covered by the observations: 1902 09 04 - 2001 04 25
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.048", 0.035", 91°.

Data for the event:

UT date and time of least geocentric approach: 2001 Mary 8, 13:33.8 UT
Approx. V mag of minor planet at event [mag]: 13.0
Geocentric parallax of minor planet ["]: 5.53
Magnitude drop [mag]: 3.1
Estimated maximum duration [s]: 22.4
Apparent motion of minor planet ["/h]: 11.87
Angular distance to moon, phase of moon [deg,%]: 28, 99%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Vindobona 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.

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