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GCN Circular 324

VLT spectrum of GRB990510
1999-05-13T20:50:38Z (25 years ago)
Paul Vreeswijk at U of Amsterdam <>
P.M. Vreeswijk, T.J. Galama, E. Rol, B. Stappers (U. of Amsterdam),
E. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna),
J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville),
C. Kouveliotou (USRA/MSFC) and H. Boehnhardt (ESO) report on behalf of
the Amsterdam/Huntsville and BeppoSAX GRB optical follow-up teams:

Three 10-min red grism and three 10-min blue grism low resolution
spectra covering 3300-11000 Angstrom, were taken of the optical
counterpart to GRB 990510 (Vreeswijk et al.; GCN #310) with the
European Southern Observatory (ESO) VLT-UT1 telescope, starting May
11.21 UT. We identified the following ultraviolet absorption lines: 
Fe II (2344 and 2600 Angstrom), Mg II (blend of 2796 and 2803). These
lines are redshifted by z = 1.619 +- 0.002 (this may be a lower limit
to the redshift of the GRB source). On the basis of this redshift we
also find some weaker features, such as Al III (1863), Cr II/Zn II
(2062), and Mg I (2852). No strong emission lines were detected.

Assuming isotropic emission, z = 1.619, H0 = 70 km/s/Mpc and
Omega0=0.3, we find a (> 20 keV) energy output of 1.4x10^{53} ergs,
based on the BATSE fluence (Kippen et al.; GCN #322).

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