Electronic Telegram No. 1921
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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PERSEID METEORS 2009
     P. Jenniskens and L. Genovese, SETI Institute; G. Barentsen,
International Meteor Organization (IMO); and J. Vaubaillon, Institut de
Mecanique Celeste et de Calcul des Ephemerides, report that at least two
outbursts were detected on top of this year's annual Perseid shower activity.
The first outburst occurred at Aug. 12d08h06m +/- 9m UT (solar longitude
139.623 deg, equinox 2000.0) with a peak rate of ZHR = 120 +/- 30 meteors/hr
and duration FWHM = 0.5 hr (observations by W. Watson, W. Godley, R. Lunsford,
P. Kozich, and W. Stone, IMO); this event is tentatively identified as an
anticipated encounter with the 1610-A.D. ejecta of comet 109P/Swift-Tuttle,
predicted to occur at 07h16m UT (P. Jenniskens 200x, *Meteor Showers and
their Parent Comets*, p. 657).  In addition, Vaubaillon reports that dust
from 1737 ejecta was at the same location, with both 1610 and 1737 ejecta
calculated to fall just outside of the earth's orbit.
     The second outburst occurred at Aug. 13d06h09m +/- 15m UT (140.505 deg)
with a peak rate ZHR = 180 +/- 30 meteors/hr and duration FWHM = 1.0 hr
(from observations by Watson, Godley, B. McCurdy, and Stone, IMO); this
outburst was unusually rich in bright meteors and was photographed at
Fremont Peak Observatory in California.  Vaubaillon identifies this event
as an encounter with the 441-A.D. ejecta, calculated to peak at 06h06m UT.
     High rates were anticipated, too, from 1348-A.D. ejecta (predicted
encounter at 16h55m UT) and from older dust trapped in mean-motion
resonances creating a structure called the Perseid Filament (predicted
encounter at 17h00m UT).  High rates reported in China during the period
13h-19h UT, if confirmed, may have come on account of this.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2009 CBAT
2009 August 22                   (CBET 1921)              Daniel W. E. Green