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(meteorobs) eta Lyrids

Dear Meteorobs folk

First of all let me note that before today I had never heard of the eta
Lyrids. However a comment from excel77d I saw in the archive lists reminded
me of a few things. Several months ago I did a lot of messing about with
comet orbits vs IAUC meteor database orbits using D criteria.  One of the
few 'new' possibilities to crop up was for comet IRAS-Iraki-Alcock, which
had six photographic meteor orbits very closely associated with it.  From
this I can guesstimate the following radiant details (which fit well with a
name like "eta Lyrids"):

RA 290 degrees, Dec 43 degrees [1950], speed = medium [Vgeo = 45 km/s], max
date = 9/10 May

[The date is a 'modal' one, the six dates were not really sufficient to
take an average from, and have asymmetric 6th May and 18th May outliers].

(Please everybody remember not to be biased by the above!)

An interesting point here is that most of these photographic meteors were
detected in 1953/4.  The orbital period of the comet is about a 1000 years.

A reference seach for 'eta Lyrids' via the NASA ADS at adsabs.harvarddot edu
revealed the following [quoted cut & paste] to be the _only_ available
reference re this stream :-

Title:          eta Lyrid Meteor Stream Associated with Comet Iras-Araki
1983 VII

 Authors:  Ohtsuka, K.

 Journal:  Origin and Evolution of Interplanetary Dust, Proceedings of IAU
Colloq. 126,
                  held in Kyoto, Japan, 27-30 August, 1990. Edited by A. C.
Levasseur-Regourd
                  and H. Hasegawa. Kluwer Academic Publishers. Also
Astrophysics and
                  Space Science Library v. 173, 1991., p.315

Literature on meteors is often hidden away in far flung and obscure texts
at the best of times. As far as I'm concerned this is no exception. Could
anyone who is lucky enough to have a copy of this work be kind enough to
give the rest of us a synopsis of the article [eg, does it note any
_visual_ detections of this stream]?

Were the eta Lyrids known of prior to 1983!?! This I'd very much like to know!

GENERAL

Given a large enough sample of meteor orbits and comet orbits most analysis
methods can find matches just through sheer coincidence.  This is
especially true for ecliptic showers and Jupiter family comets.  In this
case we have comet and meteor orbit characteristics that are not common
[how many May meteor shows near Lyra do you know?], and well away from the
ecliptic [and anthelion? I don't actually know where the antapex radiant is
at the moment!].

Visual observations of a persistent shower at such a position [no matter
how weak and minor, as long as they're real!] is an interesting and
potentially very useful addition to such information.

Another comet that came up from the data trawling at that time was Kohler
(1977XIV), though in that case the match was best with radar meteors. On
searching around I found the radiant and date details of this shower to
match very well with a shower on Gary Kronk's webpages called the September
eta Draconids.  Again, we have a high radiant, a highly inclined and pretty
uncommon orbit, and even a time of year when you'd expect such a radiant to
be more obvious in radar studes than in visual/photographic ones [there is
one potential photographic candidate].  However, all this is only
suggestive and not rigorously sorted as of yet [indeed, it may never be].

On the other end of the scale, you can find comets like Honda-Bernasconi
(1948IV) which will show good evidence of radar meteor connection via
orbital similarity in late October in Aries, and yet find absolutely no
evidence whatsoever for any suitable shower.  Thus throwing doubt on the
methodology.

Such is life.

Cheers

John

John Greaves
UK

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