Cumulative light curves of gamma-ray bursts and relaxation systems

The cumulative light curves of a large sample of gamma-ray bursts (GRBs) were obtained by summing the BATSE counts. The smoothed profiles are much simpler than the complex and erratic running light curves that are normally used. For most GRBs the slope of the cumulative light curve (S) is approximately constant over a large fraction of the burst. The bursts are modelled as relaxation systems that continuously accumulate energy in the reservoir and discontinuously release it. The slope is a measure of the cumulative power output of the central engine. A plot of S versus peak flux in 64ms (P64ms) shows a very good correlation over a wide range for both short and long GRBs. No relationship was found between S and GRBs with known redshift. The standard slope (S'), which is representative of the power output per unit time, is correlated separately with P64ms for both sub-classes indicating more powerful outbursts for the short GRBs. S' is also anticorrelated with GRB duration. These results imply that GRBs are powered by accretion into a black hole.Comment: 4 pages, 2 figures. Accepted for publication in Astronomy and Astrophysics Letter

GeV gamma-ray astronomy telescopes with high angular resolution

Gamma-ray telescopes flown on satellites have poor angular resolution with typical point source error circles of a few square degrees. It is shown that a major improvement in angular resolution for the detection of gamma-rays in the GeV region can be obtained with a single crystal as converter. The electron produced by a gamma ray incident at a small angle to a major crystal axis or plane is captured into channeling and radiates gamma rays. The channeling radiation and the electron-positron pair can be detected and yield point source locations with a precision of 5 arcseconds at 10 GeV. This is an improvement of three orders of magnitude on the angular precision of telescopes sensitive to gamma-rays above 50 MeV flown on Satellites

Temporal properties of short and long gamma-ray bursts

A temporal analysis was performed on a sample of 100 bright short GRBs with T90 < 2s from the BATSE Current Catalog along with a similar analysis on 319 long bright GRBs with T90 > 2s from the same catalog. The short GRBs were denoised using a median filter and the long GRBs were denoised using a wavelet method. Both samples were subjected to an automated pulse selection algorithm to objectively determine the effects of neighbouring pulses. The rise times, fall times, FWHM, pulse amplitudes and areas were measured and their frequency distributions are presented. The time intervals between pulses were also measured. The frequency distributions of the pulse properties were found to be similar and consistent with lognormal distributions for both the short and long GRBs. The time intervals between the pulses and the pulse amplitudes of neighbouring pulses were found to be correlated with each other. The same emission mechanism can account for the two sub-classes of GRBs.Comment: 3 pages, 8 figures; Proceedings of "Gamma-Ray Burst and Afterglow Astronomy 2001", Woods Hol

Temporal properties of the short gamma-ray bursts

A temporal analysis has been performed on a sample of 100 bright gamma-ray bursts (GRBs) with T90<2s from the BATSE current catalog. The GRBs were denoised using a median filter and subjected to an automated pulse selection algorithm as an objective way of idenitifing the effects of neighbouring pulses. The rise times, fall times, FWHM, pulse amplitudes and areas were measured and the frequency distributions are presented here. All are consistent with lognormal distributions. The distribution of the time intervals between pulses is not random but consistent with a lognormal distribution. The time intervals between pulses and pulse amplitudes are highly correlated with each other. These results are in excellent agreement with a similar analysis that revealed lognormal distributions for pulse properties and correlated time intervals between pulses in bright GRBs with T90>2s. The two sub-classes of GRBs appear to have the same emission mechanism which is probably caused by internal shocks. They may not have the same progenitors because of the generic nature of the fireball model.Comment: 4 pages, 7 figure

Terrapene carolina

Number of Pages: 13Integrative BiologyGeological Science