Electronic Telegram No. 2817
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


TAU HERCULIDS
     P. Jenniskens and M. Phillips, SETI Institute; R. Morales, Fremont Peak
Observatory; and B. Grigsby, Lick Observatory, report the detection of a
meteor outburst of tau Herculids on 2011 June 2 during routine low-light-level
video triangulations with NASA's Cameras for Allsky Meteor Surveillance (CAMS)
project in California between 4h00m and 12h13m UT.  During that time interval,
with intermittent clouds, three of 12 recorded meteors radiated from a compact
geocentric radiant at R.A. = 215.5 +/- 0.4 deg, Decl. = +34.0 +/- 0.6 deg,
with velocity V_g = 12.55 +/- 0.09 km/s.  The times of arrival for the tau
Herculid meteors were 6h01m, 6h33m, and 8h55m UT.  The faint (1.5-, 2.8-, and
2.0-magnitude) meteors penetrated from 92.0 +/- 0.5 km to 83.5 +/- 4.2 km.
Two had flat-topped lightcurves with an end flare.  The mean orbital elements
derived from the radiant and speed are q = 0.991 +/- 0.001 AU, 1/a = 0.352 +/-
0.007 1/AU, i = 13.60 +/- 0.15 deg, Peri. = 199.5 +/- 0.5 deg, Node = 71.303
+/- 0.06 deg (equinox 2000.0; one standard deviation).  These meteors
originated from comet 73P/Schwassmann-Wachmann.  The earth was predicted to
cross the 1952 dust ejecta of the comet at 5h45m UT (Luethen, Arlt, and
Jaeger 2001, JIMO 29, 15-28).  The predicted radiant position and speed were
R.A. = 214.2 deg, Decl. = +33.5 deg, and V_g = 12.9 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2011 CBAT
2011 September 11                (CBET 2817)              Daniel W. E. Green