The duration distribution of Swift Gamma-Ray Bursts

Decades ago two classes of gamma-ray bursts were identified and delineated as having durations shorter and longer than about 2 s. Subsequently indications also supported the existence of a third class. Using maximum likelihood estimation we analyze the duration distribution of 888 Swift BAT bursts observed before October 2015. Fitting three log-normal functions to the duration distribution of the bursts provides a better fit than two log-normal distributions, with 99.9999% significance. Similarly to earlier results, we found that a fourth component is not needed. The relative frequencies of the distribution of the groups are 8% for short, 35% for intermediate and 57% for long bursts which correspond to our previous results. We analyse the redshift distribution for the 269 GRBs of the 888 GRBs with known redshift. We find no evidence for the previously suggested difference between the long and intermediate GRBs' redshift distribution. The observed redshift distribution of the 20 short GRBs differs with high significance from the distributions of the other groups.Comment: accepte

Analysis of the BATSE Continuous MER data

The CGRO/BATSE database includes many types of data such as the 16-channel continuous background or medium energy resolution burst data (CONT and MER data types). We have calculated some four hundred burst's medium energy resolution spectra and Principal Component Analysis has been applied. We found five components can describe GRBs' spectra.Comment: 4 pages, 2 figures, accepted in Nuovo Ciment

Comparing the observed properties of the GRBs detected by the Fermi and Swift satellites

We studied the distribution of the GRBs, observed by the Fermi satellite, in the multidimensional parameter space consisting of the duration, Fluence, Peak flux and Peak energy (if it was available). About 10% of the Fermi bursts was observed also by the Swift satellite. We did not find significant differences between the Peak flux and Peak energy of GRBs observed and not observed also by the Swift satellite. In contrast, those GRBs detected also by the Swift satellite had significantly greater Fluence and duration. We did a similar study for the GRBs detected by the Swift satellite. About 30% percent of these bursts was also measured by the Fermi satellite. We found a significant difference in the Fluence, Peak flux and Photon index but none in duration. These differences may be accounted for the different construction and observing strategy of the Fermi and Swift satellites.Comment: 7th Huntsville Gamma-Ray Burst Symposium, GRB 2013: paper 5 in eConf Proceedings C130414

Advanced Very High Resolution Radiometer (AVHRR) data evaluation for use in monitoring vegetation. Volume 1: Channels 1 and 2

Data from the National Oceanic and Atmospheric Administration satellite system (NOAA-6 satellite) were analyzed to study their nonmeteorological uses. A file of charts, graphs, and tables was created form the products generated. It was found that the most useful data lie between pixel numbers 400 and 2000 on a given scan line. The analysis of the generated products indicates that the Gray-McCrary Index can discern vegetation and associated daily and seasonal changes. The solar zenith-angle correction used in previous studies was found to be a useful adjustment to the index. The METSAT system seems best suited for providing large-area analyses of surface features on a daily basis