GRO J0422+32 (= V518 Per) is a black-hole X-ray nova which went into outburst on August 5, 1992. Since then, we have been monitoring the decay light curve of the optical counterpart using the FLWO 1.2-m telescope. Following the steep optical decay of the primary outburst in April 1993, two mini-outbursts were observed with amplitudes of ~ 4 mag and

We have obtained a spectrum of the Na D lines of the Seyfert galaxy Mrk 595 with a signal-to-noise ratio (S/N) of about 30. The importance of this sightline is that this galaxy lies in a direction close to the highest column densities of the Cohen high-velocity (HV) stream, and hence represents the best opportunity of detecting this stream in

GT2318+620 is a variable radio source exhibiting a jet-like feature on both sides of an unresolved core (Taylor et al., Nature 351, 1991), and it is possibly associated with an UHURU X-ray source. A red 20th magnitude star coincident with the radio core was identified as the optical counterpart. Based on a neutral hydrogen absorption spectrum and

The Hubble constant can be measured from the time delay between pairs of components of a multiply-imaged quasar, depending only on the mass model and the distances to the lens and background source. For a well-determined lens model, H_0 is implicitly related to the observable parameters by H_0 propto sigma_nu^2 Delta tau^{-1}, where sigma_nu is a

Hubble Space Telescope Near-Infrared Camera and Multiobject Spectrometer (NICMOS) observations of six brown dwarf candidates in the Pleiades open cluster are presented. One of them, namely CFHT-Pl-18, is clearly resolved as a binary with an angular separation of 0.33". The very low density of contaminating background stars in our images and the

We classify nontrivial deformations of the standard embedding of the Lie algebra $Vect(S^1)$ of smooth vector fields on the circle, into the Lie algebra~$PD(S^1)$ of pseudodifferential symbols on $S^1$. This approach leads to deformations of the central charge induced on $Vect(S^1)$ by the canonical central extension of $PD(S^1)$. As a result we