We present the results of an intensive ultraviolet monitoring campaign on the Seyfert I galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously With the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra

This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert I galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and

We present simultaneous and continuous observations of Hα, Hβ, ion{Na}{1} D1, D2, ion{He}{1} D3 and ion{Ca}{2} H & K lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in Hα and ion{Ca}{2} H & K, Hβ and ion{He}{1} D3 and a strong filling-in

The extension of the highly successful Doppler technique into the near-infrared (0.9-2.5 μm) is opening new parameter domains for extra-solar planet searches in terms of ages and masses of the primary stars. Here we present the current status of NAHUAL, a next generation near-infrared spectrograph for the 10.4-meter Gran Telescopio Canarias (GTC)

We explore the possibility that the steepening observed shortward of 1000 Å in the energy distribution of quasars may result from absorption by dust, being either intrinsic to the quasar environment or intergalactic. We find that a dust extinction curve consisting of nanodiamonds, composed of terrestrial cubic diamonds or with surface impurities as

We present a first study of truncation of the stellar disks of spiral galaxies in the near infrared. Observations of NGC 4013, NGC 4217, NGC 6504 and NGC 5981 were made with the CAIN NIR camera on the CST in Tenerife. This wavelength range provides the best description of the phenomenon, not only because extinction effects are minimized, but also