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IMO Shower Circular June Bootids 1998

To: meteorobs@latrade.com, meteorite-list@meteoritecentral.com, astro@store-forward.mindspring.com, Skywayinc@aol.com
Subject: IMO Shower Circular June Bootids 1998
From: GeoZay@aol.com
Date: Wed, 8 Jul 1998 08:38:51 EDT
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Below is the shower circular from Rainer Arlt of the International Meteor
Organization about the recent June Bootid activity.
George Zay
------------------------------------------------------------------------------
-----------------------
            I M O   S h o w e r   C i r c u l a r
                      JUNE BOOTIDS 1998

The first records of this meteor shower with irregular occurrence
are from 1916 when W.F. Denning and a few anonymous observers saw
an outburst of meteors from a radiant in Draco. Since then activity
was very low except for possible significant events in 1921 and
1927. Because of the uncertain radaint position, the shower is
often referred to as the June Draconids or iota-Draconids.

An outburst of activity similar to the 1916 event was observed by
amateurs from all over the world in the night of June 26-27 (western
longitudes) and June 27-28 (eastern longitudes), 1998. Just as in
the comments of Denning, the activity is reported to be of fairly
constant behaviour, in stead of exhibiting a sharp peak.

The radiant positions given by the observers scatter strongly. Most
of the reports note a 'very diffuse radiant', just like Denning's
comments about a large radiation area. According to the most
reliable positions derived from the plots of experienced meteor
observers, we adopted an average radiant position at alpha:230 deg,
delta:+49 deg.

The following observers contributed to the below ZHR graph, several
occasional observers additionally reported their impressions of the
event, giving e.g. radiant positions.

CRIST  Stefano Crivello (Italy)
GORRO  Roberto Gorelli (Italy)
HAVRO  Roberto Haver (Italy)
HASTA  Hashimoto Takema (Japan)
IZUKI  Izumi Kiyoshi (Japan)
JENPE  Peter Jenniskens (USA)
KACJA  Javor Kac (Slovenia)
KERKH  Kerr Kathryn (Australia)
KNOAN  Andre Knoefel (Germany)
KREKE  Kevin Kretsch (Ireland)
NOSKU  Kunio Nose (Japan) (video observation)
OSAKA  Osada Kazuhiro (Japan)
RASLI  Lina Rashkova (Bulgaria)
RENJU  Jurgen Rendtel (Germany)
SATKO  Koetsu Sato (Japan)
STOEN  Enrico Stomeo (Italy)
TAYMA  Mark Taylor (USA)
TRIJO  Josep M. Trigo (Spain)
VELVA  Valentin Velkov (Bulgaria)

Additionally:
P. Brown (radar), G. Carstairs, B. Ewen-Smith, D. Girling,
V. Grigore, W.K. Hocking (radar), H.G. Konig, A. Marsh,
A. Negoescu, D. Penn, L.R. Sobkoviak, P. Suetterlin,
K. Suzuki (radio), B. Vanderwark, R. Vodicka

----------------------------------
Date   UT   Sollon  #Obs  ZHR  +-
----------------------------------
06/26 2310  95.16     2    16 +-10
06/27 0730  95.464    1    11 +- 3
06/27 1020  95.603    1    90 +-20
06/27 1150  95.662    1    85 +-17
06/27 1930  95.983    3    86 +-68
06/27 2010  95.993    6    62 +-51
06/27 2040  96.014    6    56 +-32
06/27 2120  96.036    8    59 +-32
06/27 2150  96.056   14    46 +-23
06/27 2210  96.072   11    44 +-20
06/27 2240  96.093   14    55 +-24
06/27 2320  96.122   14    48 +-28
06/28 0000  96.144   14    45 +-25
06/28 0040  96.167   10    47 +-25
06/28 0100  96.187    6    35 +-14
06/28 0120  96.199    2    21 +- 4
06/28 1220  96.64     1     0       (video)
06/29 1100  97.53     6     2 +- 2
06/29 2100  97.93     1     0
----------------------------------

The ZHR is calculated with an average radiant position at
alpha:230 deg, delta:+49 deg and a population index of r:2.0.
The activity profile has no signs of a sharp peak. Highest
ZHRs were observed between 1000 and 2000 UT on June 27, from
Australia, Japan and Bulgaria (solar longitude 95.6 degres to
96.0 degrees; eq. 2000.0). The broad activity profile was also
noted by Denning in 1916.

Individual radiant positions are given below:

Plotted meteors:
----------------
GORRO     240    +50  (15deg diameter)
HAVRO     224    +50
HASTA     229    +50
OSAKA     221    +51
STOEN     220    +59  (diffuse)
Bulg.         231    +44  (VELVA, RASLI, two centers)
                234    +48

Radar observation:
------------------
Brown &
Hocking   228    +54  (both +-3 deg, quite diffuse)

Counted meteors:
----------------
Australia (G. Carstairs, D. Girling, A. Marsh, R. Vodicka)
               218    +53  (after zenithal-attraction corr.)
CRIST      234    +51  (diffuse)
EWEBE   225    +40  (Bev Ewen-Smith)
GRIVA     224    +49
KACJA     225    +45
KREKE     255    +55
TAYMA     240    +46

Radiants observed by Denning in 1916
------------------------------------
Denning   231    +54  (main)
Denning   223    +41  (one of secondary)
(from Mon. Not. Roy. Astron. Soc. 76, p. 740 and Nature 97, p. 388)

NOTE that most of the radiant positions are not corrected for
zenithal attraction which can amount to everal degrees according
to the extremely low geocentric velocity of the meteoroid stream.
------------------------------------------
Rainer Arlt & Jurgen Rendtel, 1998 July 7.

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