Re: "Gamma Rays of Doom"

[Andrew Karam <karam.1@osu.edu>]

Dear Doug -

A supernova at a distance of 170 light years is expected to produce a
radiation dose of about 100-300 rads (1-3 Gy), primarily from gamma
radiation and protons and one at 1700 light years would give a dose of
about 1-3 rads (0.01-0.03 Gy).  I am not sure about the muon dose, but the
protons could reasonably be expected to interact in the atmosphere,
creating neutrons and cosmogenic radionuclides such as H-3, C-14, and
others that are created all the time under normal circumstances.

I am not sure how much energy is released by neutron star mergers, but I
understand it is considerably greater than that released by supernovae.
They may also release a much different mix of particles, although this,
too, is conjecture.  We would expect to see supernovae at a distance of
1700 lyrs about once every 500 K years but neutron star mergers would
happen much less frequently.

Bottom line is that I think the numbers, while high, may not be
unreasonable, but we have to keep in mind that these things don't happen
every day.  We have one or two supernovae each century in the Milky Way,
and neutron star mergers are much less common.  I'll run this by some of my
astronomer friends and see what they can add.

Andy

The opinions expressed above are well-reasoned and insightful.  Needless to
say, they are not those of my employer. (with apologies to Michael Feldman)		

Andrew Karam, MS, CHP					(614) 292-1284 (phone)
The Ohio State University 					(614) 292-7002 (fax)
Office of Radiation Safety					"The mind is not a vessel to
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(karam.1@osu.edu)