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

We spatially resolved the symbiotic star CI Cam, about 6 months after its April 1998 outburst, using the IOTA stellar interferometer. We measured the diameter of the dust shell in the H and K infrared bands over a range of position angles. We will discuss the relationship between these results and other ongoing observations of CI Cam.

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