title: Spectroscopic limits on the distance and energy release of GRB 990123
abstract: An optical spectrum of the afterglow from the unusually bright gamma-ray burst GRB 990123 obtained on 24.25 January 1999 universal time showed an absorption system at a redshift of z = 1.600. The absence of a hydrogen Lyman alpha forest sets an upper limit of z < 2.17, whereas ultraviolet photometry indicates an upper limit of z < 2.05. The probability of intersecting an absorption system as strong as the one observed along a random line of sight out to this z is at most a few percent, implying that GRB 990123 was probably at z = 1. 600. Currently favored cosmological parameters imply that an isotropic energy release equivalent to the rest mass of 1.8 neutron stars (4.5 x 10(54) erg) was emitted in gamma rays. Nonisotropic emission, such as intrinsic beaming, may resolve this energy problem.
authors: Nordic Optical Telescope, Apartado 474 St. Cruz de La Palma, E-38700 Canarias, Spain. Laboratorio de Astrofisica Espacial y Fisica Fundamental, Instituto Nacional de Tecnica Aeroespacial, Post Office Box 50727, E-28080 Madrid, Spain. Insti.
authors: MI
authors: Andersen
authors: AJ
authors: Castro-Tirado
authors: J
authors: Hjorth
authors: P
authors: Moller
authors: H
authors: Pedersen
authors: N
authors: Caon
authors: LM
authors: Cairos
authors: H
authors: Korhonen
authors: MR
authors: Osorio
authors: E
authors: Perez
authors: F
authors: Frontera