RASNZ Occultation Section - Adria Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (143) ADRIA - 2000 AUGUST 21

THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 10 AUGUST.

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[Prediction by Edwin Goffin]

[Prediction using OCCULT software]

[Detailed finder chart by Jan Manek]

Goffin's path crosses the southern Western Australian coast around the Bunbury to Perth area. Running to the north-east across the eastern Pilbara and Great Sandy Desert, the path recrosses the coast in the Broome/Derby district. The path given by OCCULT lies around 0.3" to the north-west and about 1 minute later. It runs from just north of Kalbarri to Karratha.

UPDATE: 11 August 2000

This prediction update has been computed by Jan Manek of the Stefanik Observatory based on astrometry from Ron Stone of the US Naval Observatory - Flagstaff Station. The Hipparcos position of the target star has been used.

Summary:

This update indicates a shift in the predicted path to the north-west of around 0.2" or 2 path widths and around 0.3 of a minute later than as predicted by Edwin Goffin. The path now crosses the Western Australian coastline just to the south of Geraldton (11:38 UT) running towards the north-east. The path runs just to the east of Paraburdoo and Tom Price and emerges across the coastline again to the east of Port Hedland (11:40:40 UT). The path then crosses the eastern parts of Indonesia and crosses western Japan at low altitude (11:52 UT).

When consulting the map below, observers are urged to note that the circles near the ruled path are the actual path centreline - not the time graduated lines. !!

Since the asteroid has been at very southerly declinations for most of this year, recent observations from Flagstaff, Arizona have been made at low altitudes. This has resulted in larger than usual uncertainties in the observations and consequently this updated path. With an uncertainty of around 2.2 path widths, Perth lies on or very close to the edge of the error band with a predicted time of 11:37 UT. Exmouth lies just to the west of the error band with a predicted time of 11:39:30 UT.

THE EVENT AT ONE GLIMPSE:

Date and approx. UT time of event: August 21, 2000 @ 11:39 UT
Magnitude of target star: 9.5
Magnitude drop [mag]: 4.2
Estimated maximum duration [s]: 13.7
Path description: See above.
Goffin's original chart reference: A00_0813

The Occultation Path:

Approximate width [km]: 95
Uncertainty [path widths]: 2.2
Uncertainty in time [s]: 30
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: HIP 88299 = PPM 749319 = HD 164296 = TYC 7399 722

Constellation: Sagittarius

J2000 position [h,m,s; ^o,',"]: 18h 01m 55.263s; -34^o 08' 10.40"

Position source: Hipparcos

Estimated accuracy ["]: 0.02" (0.02", 0.01")

V mag [mag]: 9.45

B-V [mag]: +0.64

Remarks:

The target star is in far western Sagittarius near the border with Scorpius. In a very crowded field, the target star is around 1.8 degrees to the north east of the very bright open cluster Messier 7 (M7) in Scorpius. The target star does have a fairly close and faint companion - GSC 7399 278 (magnitude = 12.0) only 43" to the north-east.
To see a detailed finder chart, click here.

Data for the minor planet:

Number, name: (143) Adria
Approx. diameter [km]: 93
Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone)
Number of used observations: 51
Number of rejected observations: 3
Time covered by the observations: 1997 11 09 - 2000 08 02
RMS residuals ["] (RA,DE): 0.13", 0.18"
Estimated positional accuracy at epoch of event ["]: 0.12"
The poor accuracy of this update is due to the southerly declination of the asteroid for much of this year requiring observations (from Flagstaff, Arizona, USA) to be made at low altitudes.

Data for the event:

UT date and time of least geocentric approach: 2000 August 21, 11:37.6 UT
Approx. V mag of minor planet at event [mag]: 13.7
Geocentric parallax of minor planet ["]: 4.406
Magnitude drop [mag]: 4.2
Estimated maximum duration [s]: 13.7
Apparent motion of minor planet ["/h]: 16.94
Angular distance to moon, phase of moon [deg,%]: 129, 65%
Update computed by: Jan Manek, Stefanik Observatory, Prague, Czech Republic.

Adria 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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