Electronic Telegram No. 1115
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


LEONID METEORS 2007
     Following an earlier prediction by E. Lyytinen and T. van Flandern (2000,
EMP 82-83, 149), P. Jenniskens (SETI Institute) notes that the earth should
encounter the 1932 dust trail of comet 55P/Tempel-Tuttle on Nov. 18d23h03m UT,
according to J. Vaubaillon (California Institute of Technology).  Meteors
would radiate from R.A. = 154.0 deg, Decl. = +21.4 deg, at a geocentric speed
of 70.9 km/s, according to I. Sato (Tokyo, Japan).  M. Maslov (Novosibirsk,
Russia) calculates a peak time of Nov. 18d23h05m, a shower width of FWHM about
5 hr, and a peak rate of ZHR about 60/hr, mostly due to small meteoroids.
E. Lyytinen (Helsinki, Finland) predicts the peak time to be earlier at
Nov. 18d22h36m.  This outburst will be best seen from China, India, and parts
of Russia.  The trail encounter is similar to that of 2006, when the 1932
dust trail was also encountered far from the position of the comet (cf. CBET
767).
     In a paper submitted to Icarus, Jenniskens and co-authors report an
unexpected lack of frail meteoroids in this remote part of the trail.  Based
on the magnitude distrubtion index, peak activity, and width of the 2006
Leonid shower, they anticipate for 2007 a narrow peak FWHM of about 0.68 hr,
with a peak rate of ZHR about 32/hr, and a magnitude distribution index of
chi about 2.6.  This outburst will occur on top of older (and wider) annual
shower and filament components with peak rates of ZHR = 10-20 Leonids per hr.
The 3-day-wide-FWHM annual shower will peak on Nov. 17d23h, and the 0.8-day-
wide filament of relatively bright meteors (chi about 2.1) probably a day
later.  If the filament component returns again, it may well dominate the
flux of bright meteors (i.e., those brighter than mag 3).  In 2006, the
1932-dust-trail meteors stand out well from these Leonid shower backgrounds.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2007 CBAT
2007 November 3                  (CBET 1115)              Daniel W. E. Green