Electronic Telegram No. 698
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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ORIONID METEORS 2006
     J. M. Trigo-Rodriguez, Institute of Space Sciences, Consejo Superior
de Investigaciones Cientificas (CSIC) and Institut d'Estudis Espacials de
Catalunya, Barcelona; J. M. Madiedo, Universidad de Huelva; A. J.
Castro-Tirado, Instituto de Astrofisica de Andalucia, CSIC, Granada; P.
Pujols Grup d'Estudis Astronomics, Barcelona; and A. Sanchez report that an
increase over normal Orionid meteor rates was observed between Oct. 21.062
and 21.229 UT from two locations in Spain [Montseny (Barcelona) and La
Mayora] by the Spanish Meteor Network using all-sky CCD cameras and digital
video cameras that recorded the outburst with typical limiting meteor
magnitudes of +2 to +3.  The highest rates were recorded between Oct. 21.051
and 21.099, with maximum zenithal hourly rates (ZHR) of about 50 +/- 15
meteors/hour (12 meteors in the magnitude range -7 to +3) at Oct. 21.080
(1h55m +/- 5m; solar longitude 207.44 deg, equinox 2000.00).  A nice display
of unusually bright fireballs of magnitude -7 to -5 was recorded between
Oct. 21.104 and 21.188.
     On Oct. 21.9 UT, S. Nakano (Sumoto, Japan) reported a notable increase
in meteors, including the appearance of several meteors on his CCD frames
taken around that time for cometary astrometric purposes (field-of-view 1.1
deg x 0.74 deg), the meteors appearing to radiate from the direction of
Monoceros.  Nakano later forwarded the reports of K. Mameta and K. Sumie Kobe
(observing near Chikusa-cho, Shisou-gun, Hyogo-ken, Japan), who reported
rates of 150-350 meteors/hr during Oct. 21.75-21.83.
     P. Jenniskens, SETI Institute, writes that this outburst of Orionids
(parent comet 1P/Halley) occurred over the span Oct. 19-23, but continues
at elevated levels now.  He has received visual reports from observers
worldwide, including B. Lunsford (USA, Oct. 20.4, ZHR = 24 +/- 3 meteors/hr;
Oct. 21.4, 53 +/- 5; Oct. 22.4, 46 +/- 4), K. Youmans (USA, Oct. 21.3, ZHR =
53 +/- 5 meteors/hr), K. Miskotte (The Netherlands, Oct. 22.1, ZHR = 52 +/-
8 meteors/hr), and P. Jenniskens (USA, Oct. 23.3, ZHR = 39 +/- 5 meteors/hr).
The normal Orionid rate is ZHR = 15-25 meteors/hr.  The peak time was at
Oct. 21.55 +/- 0.05 (solar longitude 207.91 +/- 0.05 deg, equinox 2000.0),
based on radio forward meteor scatter counts by I. Yrjola (Kuusankoski,
Finland).  Further to their report above, J. M. Trigo-Rodriguez and J. M.
Madiedo report from single-station astrometry a geocentric radiant at R.A.
= 96 +/- 1 deg, Decl. +14 +/- 1 deg on Oct. 21.1 (from 12 meteors).  Many
meteors were bright (with a magnitude-distribution index, or the number
ratio of meteors in neighboring magnitude intervals, of 1.88 +/- 0.08) with
trains, some reaching mag -6.  In other years, negative-magnitude Orionids
were rare after Oct. 20.  A similarly broad outburst was observed on 1993
Oct. 18 (solar longitude 204.5 deg).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 October 26                  (CBET 698)               Daniel W. E. Green