BRIEF SUMMARY:

The occultation of Beta Virginis (Zavijava) by asteroid (124) Alkeste on 2003 June 24 was the most successful minor planet occultation result ever recorded within Australasia. Some 19.5 chords were recorded across the minor planet - 9.5 from New Zealand and 10 from Western Australia, South Australia and Victoria. Many more observers attempted the event but, especially in Australia, were clouded or fogged out. Dr David Dunham, President of the International Occultation Timing Association, travelled from the U.S. to observe the event with video equipment from South Australia, while an additional video record was also obtained by David Herald. Other observers timed the event by visual means.

BRIEF RESULTS:

The event was about 4 seconds earlier than predicted. The analysis has been carried out by Dave Herald who has supplied the following plot (updated 17 August 2003). Dave writes:

I have applied PE's of at least 0.3s, and more usually 0.4 s. A longer PE was one of the results from the Pallas occultation many years ago. On the plot, "2" is the predicted North limit, "30" is the predicted South limit. As can be seen, the actual northern limit was quite a bit south of the predicted limit. However the actual southern limit was no more than about 3 km south of the predicted southern limit. This means that the central path of the occultation was only about 12km south of the predicted path - equivalent to the relative positions of the star and asteroid being less than 0.01" different from predicted. That is, the prediction was, in fact, very accurate!.

Observers appearing on the plot are:

  2(M) P Skilton, Avenel, Vic, AU
  3(M) J Eisner, Mansfield, Vic, AU
  4(M) C Rowe/J Osbourne, Culverden, NZ
  5    J Hill, Aldgate, Sth Australia
  6    S Buda, Heathcote, Vic, AU
  7    Kevin Davey, Glenelg North, SA, AU
  9    G. Blow, Balmoral Forest, NZ
 10    D Dunham, Tailem Bend, SA, AU             (Video)
 11    I Crumpton, Balmoral Station, NZ
 12    D Gault/B White, Sarsfield, Vic
 13    J Blanksby, Warracknabeal, Vic, AU
 14    D Herald, Lakes Entrance, Vic, AU
 15    R Paramor, Mt Magnet, WA, AU
 16    M Head, Hawarden, NZ
 17    L Hussey/L Fairly, Waikari, NZ
 18    P Gerbeaux, Hokitika, NZ
 19    M Finn/C Laurence, Bairnsdale,Vic, AU
 20    D Downing/O Petterson, Waipara, NZ
 21    P & B Loader, Ram Paddock Rd, NZ
 22    P Barker, Broomfield, NZ
 23    F Farrell, Aldinga, Sth Australia
 24    D Goodman, Grays Rd, NZ
 25    E Mason/P Catton, Mount Grey Rd, NZ

(M) are Miss events. (C) Clouded Out events are omitted.

A solid line on the plot, exterior to the ellipse, shows observers who could see the star throughout the event. (i.e. recorded a miss). A solid line interior to the ellipse indicates observers who recorded an occultation with a duration proportional to the indicated length of the chord. No observations were obtained from the southern side of the occultation shadow.

Additional information about the results is available on David Dunham's website at: iota.jhuapl.edu/mp124616.htm and on Alfred Kruijshoop's Alkeste website at: tufi.alphalink.com.au/astro/twomp2003.htm.

Our thanks to all the observers who contributed their time and data, and to each of the regional co-ordinators who put so much effort into organising observers in their regions. A special thanks also to those dedicated observers who travelled many hundreds of kilometres hoping to find a clear patch of sky.

Contact Graham.Blow@actrix.gen.nz for further information or to provide additional details.

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