Astrophys. J., 704, 1405-1432 (2009/October-3)
Testing the Epeak-Eiso relation for GRBs detected by Swift and Suzaku-WAM.
KRIMM H.A., YAMAOKA K., SUGITA S., OHNO M., SAKAMOTO T., BARTHELMY S.D., GEHRELS N., HARA R., NORRIS J.P., OHMORI N., ONDA K., SATO G., TANAKA H., TASHIRO M. and YAMAUCHI M.
Abstract (from CDS):
One of the most prominent, yet controversial associations derived from the ensemble of prompt-phase observations of gamma-ray bursts (GRBs) is the apparent correlation in the source frame between the peak energy (Epeak) of the νF(ν) spectrum and the isotropic radiated energy, Eiso. Since most GRBs have Epeak above the energy range (15-150 keV) of the Burst Alert Telescope (BAT) on Swift, determining accurate Epeak values for large numbers of Swift bursts has been difficult. However, by combining data from Swift/BAT and the Suzaku Wide-band All-Sky Monitor (WAM), which covers the energy range from 50 to 5000 keV, for bursts which are simultaneously detected, one can accurately fit Epeak and Eisoand test the relationship between them for the Swift sample. Between the launch of Suzaku in 2005 July and the end of 2009 April, there were 48 GRBs that triggered both Swift/BAT and WAM, and an additional 48 bursts that triggered Swift and were detected by WAM, but did not trigger. A BAT-WAM team has cross-calibrated the two instruments using GRBs, and we are now able to perform joint fits on these bursts to determine their spectral parameters. For those bursts with spectroscopic redshifts, we can also calculate the isotropic energy. Here, we present the results of joint Swift/BAT-Suzaku/WAM spectral fits for 91 of the bursts detected by the two instruments. We show that the distribution of spectral fit parameters is consistent with distributions from earlier missions and confirm that Swift bursts are consistent with earlier reported relationships between Epeak and isotropic energy. We show through time-resolved spectroscopy that individual burst pulses are also consistent with this relationship.
gamma rays: bursts
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<Available at CDS (J/ApJ/704/1405): table1.dat table2.dat table3.dat table4.dat table5.dat refs.dat>
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