Intrinsic properties of a complete sample of HETE-2 gamma-ray bursts. A measure of the GRB rate in the Local Universe

A. Pélangeon, J. -L. Atteia, Y. E. Nakagawa, K. Hurley, A. Yoshida, R. Vanderspek, M. Suzuki, N. Kawai, G. Pizzichini, M. Boër, J. Braga, G. Crew, T. Q. Donaghy, J. P. Dezalay, J. Doty, E. E. Fenimore, M. Galassi, C. Graziani, J. G. Jernigan, D. Q. Lamb, A. Levine, J. Manchanda, F. Martel, M. Matsuoka, J. -F. Olive, G. Prigozhin, G. R. Ricker, T. Sakamoto, Y. Shirasaki, S. Sugita, K. Takagishi, T. Tamagawa, J. Villasenor, S. E. Woosley, M. Yamauchi

Published 2008-11-20Version 1

Aims: Taking advantage of the forthcoming Catalog of the HETE-2 mission, the aim of this paper is to evaluate the main properties of HETE-2 GRBs - the E_peak, the T_90 and the E_iso - in their source frames and to derive their unbiased distribution. Methods: We first construct a complete sample containing all the bursts localized by the WXM on-board HETE-2, which are selected with a uniform criterion and whose observed parameters can be constrained. We then derive the intrinsic E_peak, T_90 and E_iso distributions using their redshift when it is available, or their pseudo-redshift otherwise. We finally compute the number of GRB (N_Vmax) within the visibility volume (V_max) of each GRB, in order to derive a weight for each detected burst accounting both for the detection significance and the star formation history of the universe. Results: The unbiased distributions obtained clearly show the predominence of X-ray flashes (XRFs) in the global GRB population. We also derive the rate of local GRBs: R0^H2 > 11 Gpc-3 yr-1, which is intermediate between the local rate obtained by considering only the high-luminosity bursts (~1 Gpc-3 yr-1) and that obtained by including the low-luminosity bursts (>200 Gpc-3 yr-1).