3 research outputs found
Long Gamma-Ray Bursts as standard candles
As soon as it was realized that long GRBs lie at cosmological distances,
attempts have been made to use them as cosmological probes. Besides their use
as lighthouses, a task that presents mainly the technological challenge of a
rapid deep high resolution follow-up, researchers attempted to find the Holy
Grail: a way to create a standard candle from GRB observables. We discuss here
the attempts and the discovery of the Ghirlanda correlation, to date the best
method to standardize the GRB candle. Together with discussing the promises of
this method, we will underline the open issues, the required calibrations and
how to understand them and keep them under control. Even though GRB cosmology
is a field in its infancy, ongoing work and studies will clarify soon if and
how GRBs will be able to keep up to the promises.Comment: To appear in the proceedings of the 16th Annual October Astrophysics
Conference in Maryland "Gamma Ray Bursts in the Swift Era", eds. S. Holt, N.
Gehrels & J. Nouse
On the future of Gamma-Ray Burst Cosmology
With the understanding that the enigmatic Gamma-Ray Burts (GRBs) are beamed
explosions, and with the recently discovered ``Ghirlanda-relation'', the dream
of using GRBs as cosmological yardsticks may have come a few steps closer to
reality. Assuming the Ghirlanda-relation is real, we have investigated possible
constraints on cosmological parameters using a simulated future sample of a
large number of GRBs inspired by the ongoing SWIFT mission. Comparing with
constraints from a future sample of Type Ia supernovae, we find that GRBs are
not efficient in constraining the amount of dark energy or its equation of
state. The main reason for this is that very few bursts are available at low
redshifts.Comment: 5 pages, 2 figures, matches version accepted for publication in JCA