[AAVSO-HEN] GRB 060121 : pseudo-z = 1.9 ( intermediate-duration burst)

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  6498
SUBJECT: GRB 060121 : pseudo-z = 1.9  ('intermediate-duration' burst)
DATE:    07/06/11 08:00:09 GMT
FROM:    Alexandre Pelangeon at LATT,OMP,Toulouse  <alexandre.pelangeon at ast.obs-mip.fr>

A. Pelangeon & J-L. Atteia (LATT-OMP) report:

We have used the spectral parameters of GRB 060121 detected by 
HETE-2/FREGATE
and localized by the WXM (Arimoto et al., GCNC 4550) and by the SXC
(Prighozin et al., GCNC 4551) to compute the spectral pseudo-redshift(**)
of this burst.

We find a pseudo-redshift pz = 1.92 ± 0.35

This value is in agreement with the lowest of the two values derived
by de Ugarte-Postigo et al. for the photometric redshift
of the host-galaxy: z = 1.7 ± 0.4, and z = 4.6 ± 0.5 (ApJ, 2006, 648, L83)

This pseudo-redshift relies on the assumption that GRB 060121 follows
the Amati relation. Hence we caution that if GRB 060121 is a short burst,
as suggested by Donaghy et al. (astro-ph/0605570), this pseudo-redshift
is not reliable.


(**) cf. http://www.ast.obs-mip.fr/grb/pz