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(meteorobs) A-T 1996 ZAYGE ...long article
THE 1996 ARIED-TRIANGULUM "SHOWER" FROM DESCANSO, CALIF.
by: George J. Zay
GeoZay@aoldot com
Sept. 14, 1996
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In mid-September of 1993, It was reported by George Gliba,
Gary Kronk and Kurt Sleeter about a possible minor shower
radiating from a the constellatons
of Aries and Triangulum (A-T). The apparent peak was set
being around September 12th. Despite a radiant has not yet been
determined. This year's moonless skies during this period
provided me with opportunity to ascertain whether this shower
was real and if so, help determine it's radiant. I was
able to observe and plot meteors on the nights of: Sept.
9/10, 10/11 and 11/12.
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INTRODUCTION. When I first read about this possible new
shower in Sky and Telescope(1), I immediately checked my
meteor plots for periods between Sept 5th thru Sept. 20th
for the years of 1992 and 1993. I did not observe on the
apparent peak nite of Sept. 12th, but have on nites
shortly before and after. From my plottings for those two
years, I've seen nothing obvious to suspect an unknown rad-
iant exists within the constellations of Aries or Trian-
gulum. From the Sky and Telescope article, it was indi-
cated that the meteors of this proposed shower
were of medium velocity(1).
In 1994, I was able to plot 1.5 hours on Sept 12/13 and re-
corded no signs of a radiant. On Sept 13/14 I observed for
8 hours and recorded only 10 general candidates. Six inter-
sected near Gamma Arietis and four at two other points in
Triangulum. On Sept 14/15, I again observed for five hours
and recorded three additional meteors from the A-T region.
After coarsely reviewing my data, I've realized that I still
had to take into consideration that some of these candidates
could have been chance alignments. Also path lengths to
radiant and velocity to radiant relationships had to be con-
sidered before any meteor can be deemed as a member. My
immediate suspicions were that some meteor observers with a
variety of plotting skills might have unknowingly made hasty
conclusions without considering various criteria for shower
determinations.
With 1995 plagued by moonlight, a serious effort for shower
determination had to wait for 1996 activity. This "shower"
was assumed to have activity from about Sept 5-15th(2). The
nights that I was able to make my observations were on
Sept 9/10, 10/11 and 11/12. I had hopes that from these
three nights I would be able to determine whether the shower
was new by providing a definitive radiant.
The remainder of this article deals with my efforts to do
just this.
2. GATHERING THE DATA. Observing from Descanso, Calif in the
USA, the data that I acquired for 1996 are as follows:
a) Sept 9/10. 51 plotted meteors during 6.61 teff hours
under clear 6.04 skies. 4h39-12h15 UT
b) Sept 10/11. 57 plotted meteors during 6.5 teff hours under
clear 6.01 skies. 4h56-12h19 UT
c) Sept 11/12. 60 plotted meteors during 6.78 teff hours under
clear 6.12 skies. 4h47-12h29 UT
On all three nights, I kept my field of view between 25 to 35
degrees from the A-T region.
On Sept 9/10, I quickly summed up my data by looking at the
plots and had tentatively noticed what appeared to be a tight
plot of five meteors that intersected at RA 32.5 deg, Dec. +33
near the constellation Triangulum. The following nite I was
looking for any repeat activity for this location but noted
only one possible meteor. This immediately caused me to inter-
pret the five meteor cluster for Sept. 9/10 as being chance
alignments and gave it no more serious attention. As to not-
ing any other intersecting groups for the nights of Sept 10/11
and 11/12, there weren't any that were obvious. I was serious-
ly looking for five or more intersects from meteors that had
the proper velocities and path lengths to radiant relationships
per observing nite.
My next plan to see if I can find any signs of an A-T radiant
was to combine the plots from all three nights.
3. MY ANALYZING PLAN. To search for
signs of a radiant was basically a series of steps that led me
thru a process of elimination. If I plotted all three nites
onto one chart without some form of systematic discrimination,
I felt that apparent results could be camouflaged and mis-
interpreted. My plan was to do the following and then plot the
remainder:
1) Since the meteors were described to be that of medium veloci-
ty(3 on the numeric scale), I decided it was prudent to eli-
minate the fastest(5 on the numeric scale) meteors right from
the start. Then,
2) Eliminate all meteors whose distance from a radiant to the
meteors beginning point was less than twice the meteor's
path length(3). Then,
3) Eliminate all meteors whose apparent velocities aren't con-
sistent with it's proximity to that of a radiant. Assu-
ming that the basic velocity as being medium when not rela-
tively close to the radiant, then I would expect to see very
slow meteors within 20 degrees of a radiant. For meteors
further away, I allowed velocities of 2,3 and 4 on the num-
eric scale(slow, medium and fast). Then,
4) Listed in IMO's calendar(4), it showed two minor showers as being
active...the delta Aurigids(DAU) and the Piscids(SPI). The
DAU's have very fast velocities which would be eli-
minated in step 1. On the other hand...the SPI's with a
slow to medium velocity appearance could be in conflict
with any proposed A-T members. The logic here is that
Piscids are a confirmed shower with activity in September.
If any meteor had the proper radiant alignment, path length
and velocities, they will be considered as Piscids and not
as possible A-T members.
5) The remaining meteors whose projected return paths brought
them outside an approximate 30 degree radius surrounding
Triangulum were also eliminated.
6) The remaining meteors will then be plotted onto one chart.
Any reasonable intersects of four or more will be labeled
and examined individually.
4.THE PROCESS OF ELIMINATION. To avoid confusion from the
plot numbers of one night to the next on the consolidated
plotting chart, I distinguished the plot numbers thusly:
1) Sept 9/10 = numbers have no additional marks.(ex.1,7,8).
2) Sept 10/11= numbers have ' symbol attached. (ex. 4',5',6').
3) Sept 11/12= numbers have " symbol attached. (ex.17", 25").
The initial accepted meteor numbers after eliminating all very
fast meteors and meteors outside the approximate 30 degree
radius surrounding Triangulum were:
a) Sept 9/10 = 1,7,8,19,24,29,33,37,38 and 48.
b) Sept 10/11= 4',5',6',8',16'42',44',49',50'and 55'.
c) Sept 11/12= 17", 18", 25", 30", 32", 34", and 46".
Total = 27 resultant plotted meteors.
Looking at the plots, I circled 10 possible "radiants"
labeled A thru J. (See accompanying BRNO Chart #1).
-----------------------------------------------------
Table 1. Apparent Radiants.
"RADIANT" METEOR NUMBERS
A = 1,4',8,8',16',17",25",30",42',48,49',50'
B = 7,24,44',46",49',55'
C = 1,7,16',33,34",37
D = 4',7,8,19,33,34",37
E = 1,17",18",42',49',50'
F = 6',8',17",25",34",42',50',55'
G = 16',18",19,32"
H = 17",24,42',44',46",49',50'
I = 29,37,44',46",48
J = 7,18",33,38,48,55'
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Table 2. Resultant Meteors per Radiant after eliminations due
to: 1)Path length to Radiant relationship. 2)Velocity to Rad-
iant relationship.
"RADIANT" METEOR NUMBERS
A = 1,8,17",25",30",42',48,49',50'
B = 24,38,49'
C = 33,37,38
D = 4',7,8,19,33,34",37
E = 18",42',49'
F = 8',17",25",34",42',50',55'
G = 18",32"
H = 24,42',49'
I = 37,44',46"
J = 18",33,38,48
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Table 3. Resultant Meteors per radiant after eliminations
due to being designated as members of the Piscid radiant.
RADIANT METEOR NUMBERS
A = 1,8,25",30",42',48,49',50'
B = 24,49'
C = 33,37
D = 4',7,8,19,33,34",37
E = 18",42',49'
F = 25",34",42',50',55'
G = 18"
H = 24,42',49'
I = 37,44',46"
J = 18",33,48
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5. INTERPRETATION. To seriously consider an area to be a
bonifide radiant, you have to look for a certain number of
intersects out of so many plots. If you didn't, it's con-
ceivable that with enough plots, any point in the sky can
be designated as a radiant. My criteria for a possible
radiant signature was arbitrarily chosen at 10 intersects/
25 meteors.
This is after the process of eliminations and if the inter-
sects are within two degreesdot before the eliminations, I
would be looking for intersects at anapproximate rate of
one per 10 meteors plotted. As you can see, no radiant
position qualifies. Radiant areas
A,D,and F are the front runners with 8,7 and 5
resultant meteors in the same respective order.
For a radiant to be nicely pronounced, I'd much prefer to
see at least 15 resultant members from a 168 meteor 3 day
sample to claim a radiant as being valid. My understanding
is that a ZHR of at least 3 is needed to elevate a weak
radiant above the sporadic background. For comparison,
during this same period I recorded 24 delta Aurigids(ZHR 6)
and 18 Piscids (ZHR 3). Both of these weak showers are
somewhat close to the A-T area and I'm sure if someone
wanted to adjust all the ZHR's due to various radiant eleva-
tions etc., the overall conclusion would not change.
For curiosity, despite my beliefs that a weak shower from
the A-T region doesn't exist, just where does those three
most active radiants reign? Here are their positions:
1) A = RA 0h42m, Dec.+33...In Andromeda not too far from M-31.
2) D = RA 0h48m, Dec.+16...In Piscis close to the Great Square.
3) F = RA 0h32m, Dec.+23...In the middle of the "V" forming
Piscis.
6.CONCLUSION. For at least 1996, I do not believe that a
visual radiant from within the A-T region was present. This is
not to say that a telescopic radiant isn't there, but since
the intial announcement was based on visual observations, I
highly doubt that a telescopic shower can be associated with
the initial observations. It is possible, however, that
visual A-T activity could be periodic or even basically a
one time event. Due to the initial announcements in 1993, I
still believe it's prudent to be attentive to possible A-T
activity near Sept. 12th for a few more years to come.
Reference:
(1) Sky and Telescope, Sept 1993,
(2) G. Kronk, Meteor Observers Mailing List. Sept. 1996
(3) IMO Handbook for Visual Meteor Observers. Chp.3.
Koschack, Koschny, Znojil. pp.89
(4) IMO handbook for visual meteor observers. edited by:
Rendtel, Arlt, McBeath. Chp.8. pp-290.