TITLE:   GCN CIRCULAR
NUMBER:  9227
SUBJECT: GRB 090423: Ep,i - Eiso correlation
DATE:    09/04/24 15:40:24 GMT
FROM:    Lorenzo Amati at INAF-IASF/Bologna  <amati@iasfbo.inaf.it>

L. Amati (INAF/IASF Bologna, Italy), F. Frontera (Univ. Ferrara and INAF/IASF 
Bologna, Italy), C. Guidorzi (Univ. Ferrara, Italy), E. Palazzi (INAF/IASF 
Bologna, Italy) report:

On the basis of the spectral parameters and fluence measured by Swift/BAT 
(Palmer et al., GCN 9204) and the redshift of ~7.5 - 8.5 suggested by 
photometry and spectroscopy of the optical counterpart (Cucchiara et al., 
GCN 9213; Olivares et al., GCN 9215; Thoene et al., GCN 9216; Perley et 
al., GCN 9217; Tanvir et al., GCN 9219; Fernandez-Soto et al., GRB 9222) 
we find that GRB 090423 is fully consistent with the Ep,i - Eiso 
correlation (Ep,i ~ 440 keV and Eiso ~10^53 erg for z = 8, assuming 
a flat LambdaCDM cosmology with H0=70 km/s/Mpc and Omega_M = 0.27).

In addition, the track of this GRB in the Ep,i - Eiso plane 
(http://www.iasfbo.inaf.it/~amati/grb090423.ps) implies a lower limit to 
the redshift of 1.4 (68% c.l.) and 0.9 (90% c.l.) in order to be 
consistent with the correlation. This further suggests that the event is 
not a local very reddened GRB.

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