Electronic Telegram No. 5016
Central Bureau for Astronomical Telegrams
Mailing address:  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


PERSEID METEOR SHOWER OUTBURST 2021
     P. Jenniskens, SETI Institute and NASA Ames Research Center, reports that
CAMS video-based meteoroid orbit survey networks in the United States detected
an outburst of Perseids between 6h and 11h UT on Aug. 14.  This outburst was not
anticipted from known 109P/Swift-Tuttle dust trail encounters.  Early results
from the new CAMS Texas network (coordinated by W. Cooney and including D.
Selle, F. Cyrway, and J. Brewer) in mostly clear skies and the CAMS
California network (P. Jenniskens, D. Samuels, J. Albers, E. Egland, B.
Grigsby, and J. Wray) in clear skies show an activity profile with peak
Zenith Hourly Rate (ZHR) 130 +/- 20 meteors/hr on top of normal ZHR = 40
Perseids/hr in average annual activity (cf. URL http://cams.seti.org/FDL/ for
date of August 14).  The full-width-at-half-maximum of the fitted Lorentzian
profile is 0.08 +/- 0.01 degrees solar longitude.  The peak occurred at solar
longitude 141.474 +/- 0.005 degrees (equinox J2000.0), corresponding to 8h.2
UT.  The combined magnitude distribution index was 3.59 +/- 0.36, compared to
2.94 +/- 0.04 for the annual component in other years at this solar longitude.
     P. Martin, visually observing from Ottawa, Canada, reports "multiple
Perseids per minute with many bursts, sometimes 3-4 in a second", starting
at 6h UT; he observed until 9h UT under clear skies with limiting stellar
magnitude 6.7.  From his 5-minute interval counts, K. Miskotte of the Dutch
Meteor Society calculated a peak ZHR of 210 +/- 20 meteors/hr at solar
longitude 141.474 +/- 0.005 deg.
     This also confirms radio forward-scatter meteor observations posted by
H. Ogawa of the International Project for Radio Meteor Observation (cf. URL
https://www.iprmo.org/flash/perseids-2021.html), in which 49 observers in
fourteen countries saw the detection count increase above normal levels
after 6h.4 UT (141.40 deg solar longitude) and peak at about 8h.8 UT (141.49
deg) at a level three times the Perseid peak level, before declining to normal
levels at 12h.5 UT (141.65 deg solar longitude).  Combined ZHRs peaked around
ZHR = 210 meteors/hr (cf. website URL
http://www5f.biglobe.ne.jp/~hro/Flash/2021/PER/index-e.htm).


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2021 CBAT
2021 August 14                   (CBET 5016)              Daniel W. E. Green