Electronic Telegram No. 1045
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CBAT@CFA.HARVARD.EDU (science)
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2007 AURIGID METEORS
     P. Jenniskens, SETI Institute, reports that he anticipates an Aurigid
outburst on 2007 Sept. 1d11h33m UT (cf. Jenniskens and Vaubaillon 2007,
WGN 35, 30, and EOS 88, 317).  From past Aurigid showers, Jenniskens
anticipates a shower of meteors mostly in the magnitude range -2 to +3,
with a peak rate of ZHR approximately 200 per hour during a 10-min
interval, and a duration FWHM = 25 min.  The predictions for the upcoming
Aurigid outburst are based on where the dust trail of comet C/1911 N1
(Kiess) was at the time of the very brief, limited outbursts in 1935
(Hoffmeister 1936, A.N. 258, 25; Guth 1936, A.N. 258, 27), and in 1986 and
1994 (see also the review by Jenniskens 2006, *Meteor Showers and Their
Parent Comets*, Cambridge Univ. Press, pp. 175ff).  Jenniskens and
Vaubaillon predict that the trail will be at the same distance from the
earth's orbit in 2007, adding that the position of the trail is not very
sensitive to the previous perihelion time of the comet, because the
perturbations occur on the way in, after the dust has spread at aphelion.
Hence, the overall movement of the trail over time is well determined.
     The exact position of the pattern of trail motion does reflect the
past perihelion time of the comet.  Given the distribution of dust (see
Jenniskens and Vaubaillon 2007, op.cit.), this actually puts the trails
in the earth's path in 1935, 1986, 1994, and again in 2007; assuming
a perihelion time around 2000 years ago for the comet supports these
encounters with the dust trails (the uncertainty in the perihelion time
for the comet from the available 3-month arc in 1911 is at least
several decades at its previous return, but 4 AD was assumed for this
analysis).  S. Nakano, Sumoto, Japan, writes that his own analysis of
the observations of comet C/1911 N1 yields a perihelion time in 19 BC,
confirming that the time of the predicted peak in Aurigid meteors in
2007 is not very sensitive to the time of the comet's previous perihelion
passage:  Nakano predicts that the Aurigid stream will pass closes to the
earth on Sept. 1d11h32m UT.
     A weak annual Aurigid shower has been reported by visual observers
(e.g., Dubietis and Arlt 2002, WGN 30, 22 and 168), but needs confirmation
from photographic and video techniques.


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

                         (C) Copyright 2007 CBAT
2007 August 31                   (CBET 1045)              Daniel W. E. Green