Mon. Not. R. Astron. Soc., 431, 1398-1404 (2013/May-2)
Possible existence of the Ep-Lp and Ep-Eiso correlations for short gamma-ray bursts with a factor 5-100 dimmer than those for long gamma-ray bursts.
TSUTSUI R., YONETOKU D., NAKAMURA T., TAKAHASHI K. and MORIHARA Y.
Abstract (from CDS):
We analysed correlations among the rest-frame spectral peak energy Ep, the observed frame 64 ms peak isotropic luminosity Lp and the isotropic energy Eiso for 13 short gamma-ray burst (SGRB) candidates having the measured redshift z, Tobs90/(1 + z) < 2 s and well-determined spectral parameters. An SGRB candidate is regarded as a misguided SGRB if it is located in the 3σint dispersion region from the best-fitting function of the Ep-Eiso correlation for long GRBs (LGRBs), while the others are regarded as secure SGRBs possibly from compact star mergers. Using 8 secure SGRBs out of 13 SGRB candidates, we tested whether the Ep-Eiso and Ep-Lp correlations exist for SGRBs. We found that the Ep-Eiso correlation for SGRBs (Eiso = 1051.42 ± 0.15ergs-1(Ep/774.5keV)1.58±0.28) seems to exist with the correlation coefficient r = 0.91 and chance probability p = 1.5x10-3. We also found that the Ep-Lp correlation for SGRBs (Lp = 1052.29 ± 0.066ergs-1(Ep/774.5keV)1.59±0.11) is tighter than the Ep-Eiso correlation since r = 0.98 and p = 1.5x10-5. Both correlations for SGRBs are dimmer than those of LGRBs for the same Ep by factors ∼ 100 (Ep - Eiso) and ∼ 5(Ep - Lp). Applying the tighter Ep-Lp correlation for SGRBs to 71 bright Burst and Transient Source Experiment SGRBs, we found that pseudo-redshift z ranges from 0.097 to 2.258 with the mean <z> of 1.05. The redshifts of SGRBs apparently cluster at lower redshift than those of LGRBs (<z > ∼ 2.2), which supports the merger scenario of SGRBs.