Electronic Telegram No. 1107
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)
URL http://www.cfa.harvard.edu/iau/cbat.html


ORIONID METEORS 2007
     Following last year's elevated rates (cf. CBET 698), P. Jenniskens,
SETI Institute, reports that the annual Orionid shower has again been
stronger and brighter than expected in 2007.  In the period 2007 Oct.
4-23, Orionid shower rates reported by the International Meteor
Organization were 80 percent higher than normal, peaking at ZHR = 45 per
hour on Oct. 22d11h UT.  Furthermore, a 1-day-wide outburst occurred with
a peak rate of ZHR = 25/hr, centered on solar longitude 208.15 +/- 0.05
deg (equinox 2000.0; Oct. 22d01h), similar to other such outbursts observed
in 1993 and 2006.  The total rate peaked at 65 +/- 3 per hour, stronger than
in 2006.  From single-station video observations, I. Yrj?l?, xxx,
Finland, measured radiant positions at R.A. = 94.7 deg, Decl. = +16.0 deg
on Oct. 21.03 (55 meteors); R.A. = 95.7 deg, Decl. = +16.0 deg on Oct. 22.04
(96 meteors); and R.A. = 96.9 deg, Decl. = +14.0 deg on Oct. 23.03 (57
meteors).  From three-station video observations, E. Lyytinen reports
mean radiants of R.A. = 94.9 deg, Decl. = +15.7 deg on Oct. 21.0;
R.A. = 95.8 deg, Decl. = +15.6 deg on Oct. 22.0; and R.A. = 96.4 deg, Decl.
= +15.9 deg on Oct. 23.0.
     J. M. Trigo-Rodriguez, Institute of Space Sciences (Consejo Superior
Investigaciones Cientificas) and Institut d'Estudis Espacials de Catalunya,
reports that J. M. Madiedo (Universidad de Huelva) measured a compact
radiant located at R.A. = 90.2 +/- 0.1 deg, Dec. = +14.8 +/- 0.1 deg on Oct.
19.1 (12 meteors).  The magnitude-distribution index was a low chi = 1.5 +/-
0.4.  The radiant was nearly identical to the ones reported for 2006
(Trigo-Rodriguez et al. 2007, MNRAS 380, 126) and 1993 (Jenniskens 2006,
*Meteor Showers and Their Parent Comets*, Cambridge University Press).  The
next night, Madiedo measured chi = 1.8 +/- 0.4 (Oct. 20.1).
      According to Jenniskens, annual Orionid shower rates should continue
to be elevated in the next two weeks, when the shower activity declines.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2007 CBAT
2007 October 25                  (CBET 1107)              Daniel W. E. Green