Paper: astro-ph/0512013
Date: Thu, 1 Dec 2005 03:28:14 GMT (229kb)

Title: Biological Effects of Gamma-Ray Bursts: Critical distances for severe
damage on the biota

Authors: Douglas Galante, Jorge Ernesto Horvath

Comments: 27 pages, 3 figure, submitted to Astrobiology
\\
We present in this work a unified, quantitative synthesis of analytical and
numerical calculations of the effects caused on an Earth-like planet by a
Gamma-Ray Burst (GRB), considering atmospheric and biological implications. The
main effects of the illumination by a GRB are classified in four distinct ones
and analyzed separately, namely the direct gamma radiation transmission, UV
flash, ozone layer depletion and cosmic rays. The effectiveness of each of
these effects is compared and lethal distances for significant biological
damage are given for each one. We find that the first three effects have
potential to cause global environmental changes and biospheric damages, even if
the source is located at great distances (perhaps up to ~ 100 kpc). Instead,
cosmic rays would only be a serious threat for very close sources. As a
concrete example of a recorded similar event, the effects of the giant flare
from SGR1806-20 of Dec 27, 2004 could cause on the biosphere are addressed. In
spite of not belonging to the so-called 'classical' GRBs, most of the
parameters of this recent flare are well-known and serve as a calibration for
our study. We find that giant flares are not a threat for life in all practical
situations on Earth, mainly because it is not as energetic, in spite of being
much more frequent than GRBs.

\\ ( http://arXiv.org/abs/astro-ph/0512013 , 229kb)