Study of Very Short Gamma-ray Bursts Provides Evidence for Primordial Black Holes
Scientists at the University of California, Los Angeles, have reported evidence that very short gamma-ray bursts (GRBs) may be associated with the evaporation of primordial black holes, as originally proposed by cosmologist Stephen Hawking. A team of scientists led by UCLA Professor David B. Cline have studied gamma-ray bursts with durations less than 100 milliseconds, known as very short gamma-ray bursts, or VSGRBs. These bursts were detected by several different experiments, including the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-ray Observatory, the KONUS experiment, and NASA’s Swift gamma-ray burst mission. The results were presented at the GRB 2010 meeting in Annapolis, Maryland, on November 1, 2010.
In 1974 Stephen Hawking proposed that primordial black holes (PBH) made in the early universe would evaporate via the emission of “Hawking radiation.” He also stated that smaller PBHs would evaporate more quickly, so that in the time that has passed since the “Big Bang”, only PBHs of about 10^14 grams or greater would remain. Along with Bernard Carr, Hawking also proposed that PBHs will produce a burst of radiation in the final evaporation. Since the discovery of gamma-ray bursts in 1973, many scientific groups have searched for this radiation by studying gamma-ray bursts. However the uniform distribution of GRBs across the sky, coupled with the discovery of the afterglow emission used to determine the distances to many bursts has argued against the PBH interpretation, as the luminosities from the events are too high.
In this work, Prof. Cline and his colleagues argue that the VSGRBs are a distinct population which have specific characteristics consistent with what is expected from primordial black hole evaporation events. For example, in contrast to the larger sample of GRBs, the VSGRBs are not distributed uniformly in the sky. In addition, the VSGRBs do not often have afterglow radiation, and their time profiles are in agreement with the PBH evaporation model. Studies of the brightness distribution of the VSGRBs indicates that they are relatively local, compared to the cosmological distances of most GRBs.
“VSGRBs are an intriguing phenomenon which appear to differ from the GRBs that are usually studied. We think they are excellent candidates for primordial black hole evaporation events,” said Prof. Cline. “We urge further study of these exceptional events, as confirmation of the discovery of PBHs would give a whole new kind of laboratory in space to study concepts such as the nature of black holes, their formation in the early universe, and the nature of space-time near a PBH surface.”
Science Contacts:
David B. Cline
UCLA Department of Physics & Astronomy
dcline@physics.ucla.edu
+1 310-825-1673
Stanislaw Otwinowski
CERN, Geneva, Switzerland
stanislaw.otwinowski@cern.ch
+41 22 76 76450
More information:
http://www.physics.ucla.edu/hep/vsgrb/vsgrb_ichep2010.pdf
