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(meteorobs) Xi Bootids Confirmed
Xi Bootids Confirmed - G.W. Gliba
Several experienced meteor observers from around the world have confirmed
the existence of the Xi Bootid Meteor Shower. As mentioned before here, and
in the June 1997 Sky and Telescope, this minor meteor shower was suspected on
February 5/6, 1997, when I saw 14 meteors of medium speed in 2.5 hours coming
from the area near the star Xi in Bootes during the Winter Star Party in the
Florida Keys. This area of the heavens was also watched by me on the three
following nights. In a total of 7.5 hours, from the morning of February 5/6 to
the 8/9, a total of 26 meteors were seen coming from this suspected radiant in
the constellation Bootes.
Then, two years later, on the morning of January 25/26 1999, four possible
Xi Bootids were plotted, by the Canadian meteor observer Pierre Martin, from
RA 13:55 DEC +22 in 1.6 hours, which may have been the first confirmation that
the shower was an annual one, and started in late January. Pierre Martin is
a veteran meteor observer for the North American Meteor Network (NAMN), the
American Meteor Society (AMS), and the International Meteor Organization (IMO).
This year, ace meteor observer Bob Lunsford from Chula Vista, California
was out on February 1/2, and plotting meteors. Bob is the visual coordinator
of the AMS, past Secretary General of the IMO, and a member of NAMN. Also, he
is the Recorder for the Association of Lunar and Planetary Observers Meteors
Section, and is the person most responsible for the recent revival of meteor
observing in this country a decade ago. He wrote recently to the NAMN meteorobs
newsgroup: "plots revealed no less than 5 areas in or near Bootes that produced
at least 3 meteors each. Four of the five are most likely chance alignments.
The other area may be confirmation of the Xi Bootids. An area centered near
14:05 +16 produced 5 meteors with acceptable velocities." This is a bit south
of the projected Xi Bootid area, but within a few degrees of it.
On February 2/3, Kim Youmans observed meteors from Treutlen Co, Georgia and
he plotted three faint medium-speed meteors in two hours that met at: 14 hrs 08
min +12, which is also close to Xi Bootis. Then on February 4/5, in 3.25 hours,
he plotted another five dim medium speed meteors from a radiant at: 14 hrs 09
min +14 in Bootes, a few degrees southwest of Xi Bootis. His average LM was
about 6.4 magn. On the same night, meteor observer Mike Linnolt in Hawaii saw
a couple of XBO meteors in an hour.
On the suspected night of maximum, February 5/6, the numbers of Xi Bootids
reported was the highest. From Hebei, China, Jin Zhu plotted at least six, and
possibly nine Xi Bootid meteors, with a LM of 6.0 magn. from 19:00 to 21:33 UT.
Meteor observer, Javor Kac observed with Jure Zakrajsek from Mariborska koca,
Slovenia. He was able to plot at least three meteors from near Xi Bootis. Jure
Atanackov, also from Slovenia, saw several XBO meteors, but from two radiants.
He also plotted 6 others from a radiant at 14h 45m +28, northwest of the main
Xi Bootid region. Observing from Haleakala in Maui, Hawaii, Mike Linnolt saw
14 XBO meteors from 14:40 +15 in 3 hours. In one hour (1136 to 1238 UT) he saw
7 Xi Bootid meteors! Also out for the peak, was the prolific meteor observer
Kim Youmans of Georgia. In 3.07 hours Teff, with 6.5 average LM skies, he was
able to plot 10 XBO meteors from a radiant near 14hr 11min +16, which agrees
well with the location given by Lunsford and Linnolt.
At the request of Bob Lunsford, IMO president Juergen Rendtel, in Potsdam,
Germany, included the Xi Bootids into the list for the automated video meteor
camera he has. Using Rainer Arlt's "Radiant" software, on the nights February
3/4, 5/6 and 6/7, a distinct radiant was found near RA 15.26 Dec +14, assuming
a geocentric velocity of 50 km/s, based on 18 meteors. A beautiful depiction
of this new radiant is on the web at: http://aipsoe.aipdot de/~rend/feb-boo.html
This is an important confirmation observation, and probably indicates that the
various positions given for this radiant from visual observers is from scatter,
due to the inherent errors in the visual position determinations. Another good
video confirmation was made by Peter Gural, who with poor weather conditions
was able to record two Xi Bootids on Feb. 5/6 in Northern Virginia.
In his own words, Kim Youmans wrote to the meteorobs list, addressing the
location of the Xi Bootid radiant, on Feb 8th he wrote: "After re-reviewing
my plots from the weekend, I do find a somewhat sharp radiant at RA 15.25 +14
involving 8 definite candidates and 2 potential candidates, based on speed and
path length. This is roughly two degrees right of and just below the star Tau-1
Serpens. With five of the meteors, I need only a 2-degree diameter circle to
achieve the radiant. All eight definite candidates were plotted on Feb 04/05
and 05/06. I reviewed my data after receiving J. Rendtel's video-capture update
/chart this morning on the IMO list. However, when I "subtract out" the above
eight meteors, at RA 15hr 15min +14, I am still left with a radiant at roughly
RA 14hr 09min +15 involving no less than 5 definite candidates, and 2 potential
candidates based on the same speed data and path length, using plots from Feb.
03/04, 04/05 and 05/06. This is an area roughly 2-3 degrees below Arcturus."
One interpretation of the disparity between derived radiant locations for
the Xi Bootids, is that the visual plotting accuracy has a lot of scatter when
compared to the video location found by J|rgen Rendtel in Germany. Because, it
has been know for years that most manual meteor plots are not very accurate,
as illustrated by meteor experts Millman and Porter in the 1950s, and explained
in the book, Meteor Science and Engineering by D.W.R. McKinley copyright 1961.
However, there are only one or two alternate radiants, and random scatter would
dictate there be several, unless some type of subconscious bias is at play, but
some of these observers have a lot of plotting experience. So, there is still
the possibility of one or two sub-radiants to the Xi Bootids.
Recently, Trevor Pendleton has communicated to the meteorobs email list a
mention of a Xi Bootid radiant in the British Meteor Society's (BMS) Radiant
Catalogue, Supplement No 1, published by R.A. Mackenzie in 1984. This activity
is listed from Jan 31-Feb 5, with a radiant position at 218 +21. This adds to
the validity of the annual nature of this stream, and it's confirmation, even
though the maximum date of February 5/6, and later dates weren't included in
the duration estimate. The 14.5 hrs +21 position agrees well with the one that
I derived this year from the five XBO meteors that I plotted in 1.95 hours teff
on the morning of Febrauary 6th.
Although only a minor meteor shower, the Xi Bootid maximum was strong enough
to be seen from the light polluted skies of Greenbelt, Maryland! I went out on
the peak night of Feb. 5/6, not expecting to see much. However, I was taken by
surprise when, from 7 to 9 UT, I was able to plot five XBO meteors. Although
they were faint, with an average magnitude of only about 3.6, they were still
observable in the poor 5.3 LM skies. In all, no fewer than eleven experience
meteor observers saw definite activity from the Xi Bootids this year. So, it
seems to be a real new annual meteor shower discovery.
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