We present multiband optical/IR photometry of V4580 Sgr, the optical counterpart of the accretion-powered millisecond pulsar SAX J1808.4-3658, taken during the 1998 X-ray outburst of the system. The optical flux is consistent with emission from an X-ray-heated accretion disk. Self-consistent modeling of the X-ray and optical emission during the

Context: Eight accreting millisecond X-ray pulsars (AMXPs) are known to date. Although these systems are well studied at high energies, very little information is available for their optical/NIR counterparts. Up to now, only two of them, SAX J1808.4-3658 and IGR J00291+5934, have a secure multi-band detection of their optical counterparts in

The two Fanaroff & Riley classes of radio galaxies are defined by radio morphology, and the distinction may arise from a combination of environmental conditions and central engine power. Several studies have suggested that powerful, FR II, radio galaxies are on average 0.5 mag fainter optically (i.e., are smaller) than weak, FR I, radio galaxies

The behavior of the light curve of 3C 345 is analyzed using all B magnitudes available in the literature, thus extending the number of points in the compiled light curve of this object by a factor of more than 50 percent and the coverage by about 7 yrs, in comparison with the light curve compiled by Kidger and Beckman (1986). In addition, a new and

OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) is the optical Day one instrument for the GTC and the only Spanish Day One instrument. With both instrument and telescope schedules matched, OSIRIS will be available as soon as the GTC is scientifically operational. In this contribution an overview of the instrument at

OTELO, (OSIRIS Tunable Emission Line Object Survey), will survey emission line objects using OSIRIS tunable filters in selected atmospheric windows relatively free of sky emission lines. Different high latitude and low extinction sky regions with enough angular separations will be observed yielding a total area of 1-2 square degrees. A 5 σ depth of