GCN Circular 9216

C. C. Thoene (INAF-OAB), P. D'Avanzo (INAF-OAB/U. Bicocca), A.
Fernandez-Soto (IFCA-Santander), S. Campana, D. Fugazza (INAF-OAB), 
L.A. Antonelli (INAF-OAR), G. Chincarini (Univ. Bicocca), S. Covino
(INAF-OAB), V. D'Elia (INAF-OAR), A. De Ugarte-Postigo (ESO), D.
Malesani (Dark/NBI), E. Palazzi (IASF-Bo), R. Salvaterra (INAF-OAB), A.
Fiorenzano (TNG) report, on behalf of a larger collaboration:

We observed the afterglow of GRB 090423 (Krimm et al. GCN 9198
Not found
 
 
; Tanvir 
et al. GCN 9202
Not found
 
 
; Levan et al., GCN 9206
Not found
 
 
; Cucchiara et al., GCN 9209
Not found
 
 
) 
with the Italian TNG 3.6m telescope located in the Canary Islands 
(Spain). The observations were performed using the Amici grism. We took 
a 2 hrs spectrum starting around Apr 23 at 22:16 UT (about 14.35 hours 
after the burst) and covering the range 600-2700 nm with a resolution of 
R ~ 50.

A preliminary analysis of the combined spectrum shows a very weak signal 
at the position of the NIR afterglow. No signal is observed below 
observed lambda ~ 10500 Angstrom. Assuming that the lack of signal at 
bluer wavelengths is due to Ly-alpha absorption in the IGM this gives a 
redshift of z ~ 7.6 (in agreement with the estimate of Olivares et al., 
GCN 9215
Not found
 
 
). We point out that our wavelength calibration is based on an 
archival wavelength table.

We are very grateful for the excellent support of the TNG staff.

[GCN OPS NOTE(24apr09): Per author's request, the author list was revised.]