We present the results of optical/IR observations obtained in the period June-October 1998. Images in the Gunn-z band were serendipitously taken just 3 days after the giant burst that took place on 27 Aug 1998. .

In this paper we review various organizational issues encountered when GRANTECAN, the Spanish organization responsible for the construction and operation of the GTC telescope, evolved from the construction phase of a large telescope facility into the phase of scientific operation. GRANTECAN now operates and further develops the 10.4m segmented

We critically review the basic assumptions of the standard model for the synthesis of the X-ray background (XRB) in the light of new data from ultradeep surveys by Chandra and XMM, resolving major parts of it. Important constraints come in particular from the observed redshift distributions of faint hard X-ray sources - showing large excesses at

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A Camera Barrel, located in the OSIRIS imager/spectrograph for the Gran Telescopio Canarias (GTC), is described in this article. The barrel design has been developed by the Institute for Astronomy of the University of Mexico (IA-UNAM), in collaboration with the Institute for Astrophysics of Canarias (IAC), Spain. The barrel is being manufactured by

OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) was the optical Day One instrument for the 10.4m Spanish telescope GTC. It is installed at the Observatorio del Roque de Los Muchachos (La Palma, Spain). This instrument has been operational since March-2009 and covers from 360 to 1000 nm. OSIRIS observing modes include