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

Abstract

We analyzed correlations among the rest frame spectral peak energy E p , the observed frame 64ms peak isotropic luminosity L p and the isotropic energy E iso for 13 Short Gamma Ray Burst (SGRB) candidates having the measured redshift z, T obs 90 /(1 + z) < 2 sec and well determined spectral parameters. A SGRB candidate is regarded as a misguided SGRB if it is located in the 3-σ int dispersion region from the best-fit function of the E p -E iso 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 E p -E iso and E p -L p correlations exist for SGRBs. We found that E p -E iso correlation for SGRBs(E iso = 10 51.42±0.15 erg s −1 (E p /774.5 keV) 1.58±0.28 ) seems to exist with the correlation coefficeint r = 0.91 and chance probability p = 1.5 × 10 −3 . We found also that the E p -L p correlation for SGRBs(L p = 10 52.29±0.066 erg s −1 (E p /774.5 keV) 1.59±0.11 ) is tighter than E p -E iso correlation since r = 0.98 and p = 1.5 × 10 −5 . Both correlations for SGRBs are dimmer than those of LGRBs for the same E p by factors ∼100 (E p -E iso ) and ∼ 5(E p -L p ). Applying the tighter E p -L p correlation for SGRBs to 71 bright BATSE 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.

Short versus long gamma-ray bursts: a comprehensive study of energetics and prompt gamma-ray correlations

“…Despite lacking a complete knowledge of the true cosmic rate and redshift distribution, here we argue and show that short GRBs exhibit very similar prompt-emission correlations and population distribution to those of long GRBs as presented by Shahmoradi (2013b), both qualitatively and, under plausible cosmic rate assumptions, also quantitatively. This result, along with other recent works on the time-resolved and time-integrated spectral properties of SGRBs (e.g., Ghirlanda et al 2011;Shahmoradi & Nemiroff 2011;Zhang, Chen & Huang 2012;Tsutsui et al 2013;Calderone et al 2014) points towards the possibility of a unified mechanism responsible for the prompt gamma-ray emission of the two GRB classes, independently of the diverse progenitor candidates for the two GRB populations.…”

“…Recently, Zhang, Chen & Huang (2012) and Tsutsui et al (2013) used a small sample of SGRBs with measured redshift to argue for the potential existence of intrinsic hardness-brightness correlations in the population of SGRBs similar to the class of LGRBs. Nevertheless, the strength and significance of these positive correlations in the underlying population of SGRBs could not be determined in their studies due to strong selection bias and sample incompleteness in observational data.…”

Redshift Independence of the Amati and Yonetoku Relations for Gamma-Ray Bursts

“…As mentioned earlier, although many recent studies have looked at different aspects of GRB energy and luminosity relations [27][28][29], only a few have specifically considered the issue of redshift evolution of these relations.…”

Gamma-Ray Burst Prompt Correlations

“…The results point toward a universal relation between peak and * peak related to the nonthermal components. Tsutsui et al [237] analysed 13 SGRB candidates (i.e., an SGRB with * 90 < 2 s), from among which they selected 8 events considering them as secure ones. An SGRB candidate is regarded as a misguided SGRB if it is located within the 3 int dispersion region from the best-fit * peak -iso function of the correlation for LGRBs, while the others are regarded as secure SGRBs.…”