RASNZ Occultation Section - Carmen Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (558) CARMEN - 2001 JUNE 19

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

The path given by Edwin Goffin runs from Sydney in New South Wales west to the head of Gulf of St. Vincent in South Australia. The path then clips the far southern tip of Western Australia. The path given by Occult lies slightly to the south and around 30 seconds later. This path passes just to the north of Canberra and just south of Adelaide and includes Albany in Western Australia.

UPDATE: 15 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 UCAC position of the target star has been used.

Summary:

This update indicates a shift of around 4 path widths to the south and 2 minutes later than that given by Goffin. This path passes just to the north of the North Island of New Zealand at 13:45:30 UT. It crosses the southern New South Wales coast just north of Bega and includes Cooma (13:50 UT). Running west, the path includes Bendigo (13:50:35 UT) and Horsham before passing into South Australia and the Great Australian Bight around Naracoorte (13:51:20 UT). The path now misses Western Australia with the closest approach to Albany at 13:54 UT.

The error tolerance includes Canberra (13:50 UT) and Melbourne (13:50:30 UT) with Adelaide near the north edge at 13:51:30 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: 19 June 2001 @ 13:50 UT
Magnitude of target star: 11.21
Magnitude drop [mag]: 2.8
Estimated maximum duration [s]: 9.1
Path description: See above.
Goffin's original chart reference: A01_0629

The Occultation Path:

Approximate width [km]: 64
Uncertainty [path widths]: 1.6 (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 5762-01940-1
Constellation: Capricornus
J2000 position [h,m,s; ^o,',"]: 20h 28m 17.927s; -13^o 03' 34.24"
Position source: UCAC 1
Estimated accuracy ["]: 0.042" (0.030", 0.030")
V mag [mag]: 11.21
Remarks:
The target star is in northwestern Capricornus. It lies only 1.9 degrees east of nu Capricorni (magnitude = 4.8).

Data for the minor planet:

Number, name: (558) Carmen
Approx. diameter [km]: 61.6
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone), AstDys
Number of used observations: 318
Number of rejected observations: 46
Time covered by the observations: 1905 02 09 - 2001 06 07
Uncertainy Ellipse ["] (major axis, minor axis, PA): 0.056", 0.049", 85°.

Data for the event:

UT date and time of least geocentric approach: 2001 June 19, 13:39.6 UT
Approx. V mag of minor planet at event [mag]: 13.89
Geocentric parallax of minor planet ["]: 4.07
Magnitude drop [mag]: 2.8
Estimated maximum duration [s]: 9.1
Apparent motion of minor planet ["/h]: 15.64
Angular distance to moon, phase of moon [deg,%]: 117, 5%
Update computed by: Steve Preston, Medina, Washington, USA. (OrbFit)

Carmen 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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