SGRBShort Gamma Ray Bursts
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[176] pointed out that the ratio [E.sub.peak]/[S.sub.tot] can serve as an indicator of the ratio of the energy at which most of the [gamma]-rays are radiated to the total energy and claimed that the [E.sub.peak]-[S.sub.tot] relation is a significant tool for classifying LGRBs and SGRBs. The fluence indicates the duration of the burst without providing a biased value of [T.sub.90] and [E.sub.peak]/[S.sub.tot] displays, as a spectral hardness ratio, an increased hardness for SGRBs in respect to LGRBs, in agreement with [10].
[177], with the results of time-resolved spectral analysis, computed the [E.sub.peak]-[S.sub.tot] relation for 51 LGRBs and 11 bright SGRBs observed with Fermi/GBM.
Afterwards, Amati [190] (see Figures 8(a) and 8(c)) updated the study of the [E.sub.peak]-[E.sub.iso] correlation considering a sample of 41 LGRBs/XRFs with firm values of z and [E.sub.peak], 12 GRBs with uncertain z and/or [E.sub.peak], 2 SGRBs with certain values of z and [E.sub.peak], and the subenergetic events GRB980425/SN1998bw and GRB031203/SN2003lw.
Moreover, subenergetic GRBs (980425 and possibly 031203) and SGRBs were incompatible with the [E.sub.peak]-[E.sub.iso] relation, suggesting that it can be an important tool for distinguishing different classes of GRBs.
In addition, it was pointed out that almost all Amati type bursts are LGRBs at higher energies, as opposed to non-Amati type bursts which are mostly SGRBs. An improvement to this classification procedure is that the two types of GRBs are clearly separated; hence different GRBs can be easily classified.
[228] selected 36 bright SGRBs detected by BATSE, with an [F.sub.peak] on the 64ms timescale in the 50-300 keV energy range exceeding 10 ph [cm.sup.-2] [s.sup.-1].
with r = 0.98 and P = 1.5 x [10.sup.-5], where [E.sup.*.sub.peak] (in units of 774.5 keV) is from the time-integrated spectrum, while [L.sub.peak] (in erg [s.sup.-1]) was taken as the luminosity integrated for 64 ms at the peak considering the shorter duration of SGRBs. Application of this relation to 71 bright BATSE SGRBs resulted in pseudoredshifts distributed in the range z [member of] [0.097, 2.258], with <z> = 1.05, which is apparently lower than <z> = 2.2 for LGRBs.
However, since only few SGRBs are included in the samples used, the correlations and interpretations are currently only applicable to LGRBs.
Regarding the study of SGRBs within the context of these two correlations, Tsutsui et al.
Both correlations for SGRBs indicate that they are less luminous than LGRBs, for the same [E.sub.peak], by factors [equivalent] 100 (for [E.sub.peak]-[E.sub.iso]) and [equivalent]5 (for [E.sub.peak]-[L.sub.peak]).
These correlations might also serve as discriminating factors among different GRB classes, as several of them hold different forms for SGRBs and LGRBs, hence providing insight into the generating mechanisms.
Caption: Figure 17: Observations of KNe associated with SGRBs: (a) GRB 130603B, from [395].