Subject: Re: Gamma Ray Bursters How energetic could they be?
From: belgarath@vax1.mankato.msus.edu
Organization: Mankato State University
Nntp-Posting-Host: vax1.mankato.msus.edu
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In article <1rgvjsINNbhq@senator-bedfellow.MIT.EDU>, jfc@athena.mit.edu (John F Carr) writes:
> 
> If gamma ray bursters are extragalactic, would absorption from the
> galaxy be expected?  How transparent is the galactic core to gamma
> rays?
> 
> How much energy does a burster put out?  I know energy depends on
> distance, which is unknown.  An answer of the form _X_ ergs per
> megaparsec^2 is OK.
> 
> 
> --
>     John Carr (jfc@athena.mit.edu)
        I had to turn to one of my problem sets that I did in class for this
little problem.  I don't have a calculator, but I DO have the problem set that
we did not too long ago, so I'll use that, and hope it's what you wanted.  
This is a highly simplified problem, with a very simple burst.  Bursts are
usually more complex than this example I will use here.
        Our burst has a peak flux of 5.43E-6 ergs cm^-2 sec^-1 and a duration
of 8.95 seconds.  During the frst second of the burst, and the last 4 seconds,
its flux is half of the peak flux.  It's flux is the peak flux the rest of the
time.  Assume that the background flux is 10E-7 erg cm^-2 sec^-1.
        Then we had to find the integrated luminosity of the burst, for several
different spheres: R=.25pc(Oort Cloud Radius), R=22.5pc(at the edge of the
galaxy), R=183.5pc or the edge of the galactic corona, and lastly at a
R=8800Mpc.  
        We integrated the flux over all time to find the fluence, then used the
old standby formula:
                        Luminosity=4(pi)(r^2)Fpeak
        For a radius of .25 pc, we found an L around 10^32 erg/sec.  Pretty
energetic for close by.  for the coronal model, we found around 10^43 erg/sec.
And lastly, for the cosmological model an L=10^53. That's what you'd call
moderately energetic, I'd say.  Any suggestions about what could put out that
much energy in one second? 
                                                -jeremy



