Electronic Telegram No. 4041
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


URSID METEORS 2014
     P. Brown, Western University, reports that a significant outburst of
Ursid meteors was detected by the Canadian Meteor Orbit Radar (CMOR) between
Dec. 22d23h15m and 23d00h45m UT (activity full-width at half-maximum).  The
apparent activity maximum occurred at Dec. 23d00h UT (solar longitude 270.85
+/- 0.03 deg, equinox 2000.0).  A total of 85 Ursid orbits were measured in
this 1.5-hour period from a mean geocentric radiant of R.A. = 221 deg, Decl.
= 75 deg (equinox 2000.0) with geocentric velocity 32 km/s.  The strength of
this outburst was the highest among all Ursid outbursts detected by CMOR from
2002 to 2014, having an estimated peak ZHR in excess of 50.  The shower was
not rich in overdense echoes.  The timing of this peak is a reasonable match
to the prediction by J. Vaubaillon of Dec. 23d00h40m UT for encounter with
material released by comet 8P/Tuttle in 1392 AD.

     P. Jenniskens, SETI Institute, confirms detecting elevated Ursid meteor
shower rates following the earth's crossing of the 1405 AD ejecta of comet
8P/Tuttle (cf. Jenniskens et al. 2002, Icarus 159, 197).  During routine
low-light-level video triangulations with NASA's Cameras for Allsky Meteor
Surveillance (CAMS) project in California, 20 Ursid orbits were measured on
Dec. 23 between 1h32m (end of civil twilight) and 4h00m UT, radiating from a
compact geocentric radiant at R.A. = 220.6 +/- 1.5 deg, Decl. = +76.0 +/- 0.7
deg, with velocity V_g = 32.9 +/- 0.2 km/s.  The remainder of the night
(until 14h30m UT) saw only fifteen other Ursids.  This was the tail of the
meteor outburst reported by Brown (see above).  Radio-forward-meteor-scatter
observations by I. Yrjola (Kuusankoski, Finland) show elevated rates in this
same period.  The predicted peak time was Dec. 22d23h38m UT, in good agreement,
but peak rates were higher than expected.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 January 1                   (CBET 4041)              Daniel W. E. Green