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GCN Circular 9457

Subject
GRB 090529: VLT spectroscopic redshift
Date
2009-05-31T10:39:47Z (15 years ago)
From
Valerio D'Elia at INAF-OAR <delia@oa-roma.inaf.it>
D. Malesani, J. P. U. Fynbo, (DARK/NBI), V. D'Elia (INAF/OAR), 
A. de Ugarte Postigo (ESO), P. Jakobsson (U. Iceland), 
C. C. Thoene (INAF/OAB), report on behalf of a larger collaboration:

Using FORS2 on the ESO Very Large Telescope, we have obtained 
low-resolution spectra (2 x 30 min) of the optical afterglow of GRB 
090529 (Sakamoto et al., GCN 9430; Xin et al., GCN 9431) with the grism 
300V, covering the wavelength range 3500-9200 AA. In the acquisition 
image the afterglow has a magnitude of R ~ 22.60 +-0.05. The first spectrum 
was taken starting on May 31.0778 UT (1.48 days after the GRB).

In a preliminary analysis we detect strong absorption around 4416 AA
which we interpret as Lyman-alpha at a redshift of 
z = 2.63. This value is supported by the detection of several metal
absorption features, e.g., SiII 1526, CII 1335, SiII 1402 and CIV 1549, all
at the common z=2.625, which we interpret as the redshift of the GRB. 

We thank the Paranal staff for excellent support, in particular 
Thomas Szeifert, Alain Smette, and Karla Aubel. We are also grateful to Lipin Xin 
for providing us with a finding chart.



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