David J. Jeffery
Department of Physics
New Mexico Tech
801 Leroy Place
Socorro, New Mexico 87801-4796
U.S.A.

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                                                   2002 August 12
Dear Koji, Ken, & Paolo:
     In my view, I don't think we need to worry 
about of Berger et al.  I don't pretend to understand
the much about radio astronomy or modeling, but it
seems to me to be poor paper based on the way they argue
for their very broad conclusions.

     A key point that strikes me right now is that
they ``wonder how secure'' (i.e., their phrase meaning they
``think wrong'') Mazzali et al.'s conclusions about total
mass and kinetic energy.  Their argument is because
(as far as I can tell) someone else's model (Matzner
& Mckee 1999) puts more kinetic
energy at v>=.3c than they can allow for that
Mazzali et al.'s conclusions are wrong.  Mazzali et al.
cut ejecta off at about .2c.  As I understand their
Figure 2b their favored model will through the
epoch they observe has a shock radius which 
is order where Mazzali et al.'s outer radius would be.
A little give between both papers and there is no conflict at all.
Mazzali et al. never claim anything for v>=.2,
and so Berger et al. criticism is spurious. 

     In regard to our jet.   As long as it is below 
than their shock radius, I don't see why it should
bother Berger et al. at all.  I did ask Edo Berger 
about whether this should be so, but in fact he managed 
not to answer this question. 
I also asked Berger if it made any difference
that fast ejecta was clump in a jet or spread in a shell.
He seemed to agree that it would be difficult to detect
a jet although his answer was a bit ambiguous (or maybe it
was my question.)
Berger did say that they could be able to detect,
asymmetry in the circumstellar medium, but not in the ejecta.
I simply have my doubts about CSM.  Berger
pointed out Weiler et al. (2001, ApJ, 562, 670) showing
that asymmetries can be picked out.
Well Weiler et al. required clumpy structure:
nothing about about large scale structure asymmetry
was discussed.
If radio can pick out large scale asymmetries in CSM
or SN ejecta, I've never heard of it:  of course,
I've not paid much attention to radio work.

     Another point they seem to miss.  They think
invoking asymmetry in the ejecta can bring about
agreement.   That seems unlikely to me.  If for
example one needs 1/100 solar masses beyond .3c
(not that Mazzali et al. do) in spherical symmetry
and that means KE(v>=.3c)=2*10**50 ergs.
This is much larger than Berger et al. can allow
for:  they  can tolerate of order 10**45 ergs only.
Saying one is looking down elongated axis and that 
accounts for the broad lines will reduce the amount 
of fast mass appreciably but not by 5 orders of magnitude.
Maybe by a factor of 10, but I'd guess less than that.
In any case, this point is moot, since no one has asked
for any ejecta at speeds greater of order .2c.

     I can well believe that radio modeling could
detect a spherical shell of relativistic ejecta
propagating in a spherical CSM.  Their claim
that geometry doesn't matter is simply unvalidated in
their paper and they reference nothing else.
Their criticism of Mazzali et al.
and Kawabata et al. is without any merit that I
can see.
                                Regards 
				David