ASTROMETRIC UPDATE:
OCCULTATION BY (221) EOS - 2000 SEPTEMBER 28
THIS UPDATE REPLACES THE PREVIOUS UPDATE OF 23 SEPTEMBER.
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[Prediction by Edwin Goffin]
[Prediction using OCCULT software]
[Detailed finder chart by Jan Manek]
Goffin's path runs south through western Japan, the Philippines and central Indonesia to clip the Western Australian coastline around Exmouth. The path given by OCCULT (using the Tycho 2 star position) lies around 0.4" to the west and two minutes earlier. This path crosses western Java and misses the Australian coastline by about 350 km.
UPDATE: 27 September 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 TYC-2 position of the target star has been used.
Summary:
This update indicates a shift in the predicted path to the west of around 0.6" relative to Goffin's prediction and slightly (0.7 minute) earlier. The new path crosses central western Java running south to miss the Australian coastline by around 500 km. The closest approach to Exmouth occurs at 20:05 UT and to Perth at 20:08 UT.
THE EVENT AT ONE GLIMPSE:
- Date and approx. UT time of event: September 28, 2000 @ 20:05 UT
- Magnitude of target star: 10.7
- Magnitude drop [mag]: 2.0
- Estimated maximum duration [s]: 20.1
- Path description: See above.
- Goffin's original chart reference: A00_0911
The Occultation Path:
- Approximate width [km]: 120
- Uncertainty [path widths]: 2.0
- Uncertainty in time [s]: 45
- 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 0072-00579-1
- Constellation: Taurus
- J2000 position [h,m,s; o,',"]: 3h 50m 54.568s; +5o 26' 57.92"
- Position source: TYC 2
- Estimated accuracy ["]: 0.07" (0.05", 0.05")
- Johnson V mag [mag]: 10.67
- B-V [mag]: +0.62
- Remarks:
- The target star is in south-western Taurus. The magnitude 5.3 star 29 Tauri lies 1.4 degrees to the north-west of the target star. The magnitude 9.9 star PPM 146967 = SAO 111456 = TYC 72 1056 lies only 1.45' to the north-west of the target star and is clearly shown in the predictions given by Goffin within the circle around the target star.
To see a detailed finder chart, click here.
Data for the minor planet:
- Number, name: (221) Eos
- Approx. diameter [km]: 110
- Source of used astrometry: US Naval Observatory - Flagstaff Station (Ron Stone)
- Number of used observations: 49
- Number of rejected observations: 2
- Time covered by the observations: 1998 01 29 - 2000 09 20
- RMS residuals ["] (RA,DE): 0.08", 0.10"
- Estimated positional accuracy at epoch of event ["]: 0.09"
Data for the event:
- UT date and time of least geocentric approach: 2000 September 28, 19:56.3 UT
- Approx. V mag of minor planet at event [mag]: 12.5
- Geocentric parallax of minor planet ["]: 4.129
- Magnitude drop [mag]: 2.0
- Estimated maximum duration [s]: 20.1
- Apparent motion of minor planet ["/h]: 12.76
- Angular distance to moon, phase of moon [deg,%]: 139, 1%
- Update computed by: Jan Manek, Stefanik Observatory, Prague, Czech Republic.
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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