Mon. Not. R. Astron. Soc., 391, 639-652 (2008/December-1)
Peak energy of the prompt emission of long gamma-ray bursts versus their fluence and peak flux.
NAVA L., GHIRLANDA G., GHISELLINI G. and FIRMANI C.
Abstract (from CDS):
The spectral-energy (and luminosity) correlations in long gamma-ray bursts are being hotly debated to establish, first of all, their reality against possible selection effects. These are best studied in the observer planes, namely the peak energy Eobspeak versus the fluence F or the peak flux P. In a recent paper, we have started to investigate this problem considering all bursts with known redshift and spectral properties. Here, we consider instead all bursts with known Eobspeak, irrespective of redshift, adding to those a sample of 100 faint BATSE bursts representative of a larger population of 1000 objects. This allows us to construct a complete, fluence-limited, sample, tailored to study the selection/instrumental effects we consider. We found that the fainter BATSE bursts have smaller Eobspeak than those of bright events. As a consequence, the Eobspeak of these bursts is correlated with the fluence, though with a slope flatter than that defined by bursts with z. Selection effects, which are present, are shown not to be responsible for the existence of such a correlation. About six per cent of these bursts are surely outliers of the Epeak-Eiso correlation (updated in this paper to include 83 bursts), since they are inconsistent with it for any redshift. Eobspeak also correlates with the peak flux, with a slope similar to the Epeak-Liso correlation. In this case, there is only one sure outlier. The scatter of the Eobspeak-P correlation defined by the BATSE bursts of our sample is significantly smaller than the Eobspeak-F correlation of the same bursts, while for the bursts with known redshift the Epeak-Eiso correlation is tighter than the Epeak-Lisoone. Once a very large number of bursts with Eobspeakand redshift will be available, we thus expect that the Epeak-Liso correlation will be similar to that currently found, whereas it is very likely that the Epeak-Eiso correlation will become flatter and with a larger scatter.
© 2008 The Authors. Journal compilation © 2008 RAS
radiation mechanisms: non-thermal - gamma-rays: bursts - X-rays: general
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