Re: Gamma Ray Bursts -- Fireballs or Cannonballs?

[EMAIL PROTECTED] (Melroy) writes:

> [EMAIL PROTECTED] (Jim Graber) wrote in message news:<[EMAIL PROTECTED]>...
>> Has anyone else been paying any attention to the fireball versus
>> cannonball dispute?
>> It seems to me the cannonball guys have some fairly strong points, but
>> no one else seems to agree.  Why is this? Is there a fatal flaw in
>> their argument? Why are fireballs so popular?
>> Inquiring minds want to know...
> 
> wasn't the cannon ball model ruled out last May? At least this is what the
> press release says:
> at least this is what I am inferring from the following press release: 
> http://www.nrao.edu/pr/2003/grb030329/
> Or am I reading too much into this?
> anyhow can some expert comment?

I don't think so. One of the implications of the "hypernova" model is that
due to relativistic effects, the gamma-ray bursts are _HIGHLY_ beamed, 
with opening angles of less than ten milliradians (about 1/2 a degree).  
We would only an "ordinary" Type Ia "supernova" unless the rotation axis of
the nascent black hole from the hypernova happens to be pointing almost
DIRECTLY at us --- in which case no significant "proper motion" would be
observed. The recent observation by Coburn and Boggs that the gamma rays
from a GRB are highly polarized (~80%), strongly supports the "hypernova"
model, and strongly disfavors the "fireball" model, which does not have 
any preferred axis along which to polarize the gamma-rays, and which
predicts polarizations of less than a few percent.


-- Gordon D. Pusch   

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