ASTROMETRIC UPDATE:
OCCULTATION BY (640) BRAMBILLA - 2001 MAY 14
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[Prediction by Edwin Goffin]
[Prediction using OCCULT software]
The path given by Edwin Goffin covers the western half of Tasmania and the Melbourne metropolitan area. It then runs to the north up the spine of the Cape York Peninsula in Queensland. The path given by Occult lies around two path widths to the east running just east of Hobart in Tasmania and Traralgon in Victoria. It emerges from the Queensland coastline in the Princess Charlotte Bay area.
UPDATE: 12 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. The Tycho-2 position of the target star has been used.
Summary:
This updated path lies around four pathwidths to the east of that give by Edwin Goffin with little difference in the expected time. The path now misses Tasmania and crosses the Victorian coastline in the Orbost/Mallacoota area running north to cover much of the Australian Capital Territory (10:49:50 UT) within the eastern part of the path. Running north, the path should lie close to Dubbo before passing into Queensland where it runs along the coastline in the Ingham to Cairns area (10:54 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 14, 2001 @ 11:50 UT
- Magnitude of target star: 10.8
- Magnitude drop [mag]: 3.4
- Estimated maximum duration [s]: 11.7
- Path description: See above.
- Goffin's original chart reference: A01_0528
The Occultation Path:
- Approximate width [km]: 80
- Uncertainty [path widths]: 1.2 (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 5521-00995-1 = PPM 225179
- Constellation: Virgo
- J2000 position [h,m,s; o,',"]: 11h 57m 57.192s; -11o 21' 57.57"
- Position source: Tycho - 2
- Estimated accuracy ["]: 0.046" (0.030", 0.035")
- V mag [mag]: 10.8
- B-V [mag]: +0.690
- Remarks:
- The target star is in southwestern Virgo near the boders with Corvus and Crater. The target star lies 5.5 degrees east southeast of theta Crateris (magnitude = 4.7) and around 7.4 degrees northwest of gamma Corvi (magnitude = 2.6)
Data for the minor planet:
- Number, name: (640) Brambilla
- Approx. diameter [km]: 84
- Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone)
- Number of used observations: 68
- Number of rejected observations: 17
- Time covered by the observations: 1998 09 18 - 2001 05 06
- Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.029", 0.019", 115°.
Data for the event:
- UT date and time of least geocentric approach: 2001 May 14, 10:55.7 UT
- Approx. V mag of minor planet at event [mag]: 14.07
- Geocentric parallax of minor planet ["]: 3.79
- Magnitude drop [mag]: 3.4
- Estimated maximum duration [s]: 11.7
- Apparent motion of minor planet ["/h]: 15.45
- Angular distance to moon, phase of moon [deg,%]: 127, 59%
- Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)
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:
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