GCN Circular 6017

L. Amati (INAF/IASF Bologna), F. Frontera (Univ. Ferrara and INAF/IASF 
Bologna), C. Guidorzi (Univ. Milano Bicocca and INAF/OAB), E. Montanari 
(Univ. Ferrara and ITA "Calvi") report:

"Based on the correlation between power-law photon index and peak energy 
of GRB spectra measured by Swift/BAT in 15-150 keV (Zhang et al. 2006, 
astro-ph/0612238, and Sakamoto et al., ApJ, submitted), the photon index 
of 1.57+/-0.12 measured by BAT for GRB 070110 (Cummings et al, GCN 6007
Not found
 
 
) 
corresponds to a peak energy Ep of ~110+/-50 keV. From this spectral 
information and the reported 15-150 keV fluence of (1.6+/-0.1)x10^-6 
erg/cm2 (GCN 6007
Not found
 
 
), by assuming a Band spectral shape and by taking into 
account the redshift of 2.352 (Jaunsen et al., GCN 6010
Not found
 
 
), it is then 
possible to estimate the values of the intrinsic peak energy, Ep,i ~ 
370+/-170 keV, and of the isotropic equivalent radiated energy in the 
1-10000 keV cosmological rest frame, Eiso ~ (5.5+/1.5)x10^52 erg (the 
uncertainties on Ep,i and Eiso take approximately into account the 
measurements errors, the scatter of the photon index - peak energy 
correlation and the dependence of Eiso on the values assumed for alpha and 
beta in the Band spectral model).

These values are consistent within 2 sigma with the Ep,i-Eiso correlation.

If, conservatively, we assume a Band model with alpha equal to the power-law 
spectral index measured by BAT and beta = -2.3, we find that GRB 070110 is 
consistent with the Ep,i-Eiso correlation within 2 sigma for a measured Ep up 
to ~170 keV (E0 ~400 keV), and within 3 sigma for a measured Ep up to ~280 keV 
(E0 ~650 keV). These values of E0 are well above the upper bound of the BAT 
energy band used for spectral analysis (150 keV).

Thus, we conclude that, despite the very peculiar behaviour shown by its 
X-ray afterglow after ~20 ks from the burst onset (Krimm et al., 
GCN_Report 26.2), GRB 070110 seems to be a common long event from the 
point of its position in the Ep,i-Eiso plane. This, together with the 
standard behaviour of the early afterglow light curve (steep decay, flat 
decay) could indicate that the emission mechanisms / environment 
originating the prompt emission are not necessarily linked to those 
producing the LATE afterglow emission."

This message may be cited.