Space Forum / SETI / April 2006

Remember the claim that gamma-ray bursts can "sterilize" a galaxy?
This abstract is a bit dense but references that idea:

astro-ph/0604113
Title: Protecting Life in the Milky Way: Metals Keep the GRBs Away
Authors: K. Z. Stanek, O. Y. Gnedin, J. F. Beacom, A. P. Gould,
   J. A. Johnson, J. A. Kollmeier, M. Modjaz, M. H. Pinsonneault,
   R. Pogge, D. H. Weinberg
Comments: ApJ, submitted, 14 pages, 3 figures

The host galaxies of the four local, z<0.17, long-duration gamma-ray
bursts, each of which had an associated hypernova studied with optical
spectroscopy, are all faint and metal-poor compared to the population
of local star-forming galaxies. We quantify this statement by using a
previous analysis of star-forming galaxies (z<0.2) from the Sloan
Digital Sky Survey to estimate the fraction of local star formation as
a function of host galaxy oxygen abundance. We find that only a small
fraction (<20%) of current star formation occurs in galaxies with
oxygen abundance 12+log(O/H)<8.6, i.e., about half that of the Milky
Way. However, all four low-z GRB hosts have oxygen abundance below
this limit, in three cases very significantly so. If GRBs traced local
star formation independent of metallicity, the probability of
obtaining such low abundances for all four hosts would be P~0.15%. We
conclude that GRBs trace only low-metallicity star formation, and that
the Milky Way has been too metal rich to host long GRBs for at least
the last several billion years. This result has implications for the
potential role of GRBs in mass extinctions, for searches for recent
burst remnants in the Milky Way and other large galaxies, for
non-detections of late radio emission from local core-collapse
supernovae, and for the production of cosmic rays in the local
Universe. We also find that the isotropic energy release of these four
GRBs, E_iso, steeply decreases with increasing host oxygen abundance,
suggesting an upper metallicity limit for ``cosmological'' GRBs at
~0.15 Z_solar. (Abridged)