Ambiguity is shown in the context of the differential calculus of several variables and with the help of the language of category theory, a way to solve it in its most general form is offered. It is also shown that this new definition is related to other well-known definitions in the literature.

We have obtained for the first time K-band infrared spectra of the soft X-ray transient V616 Mon (=A0620-00). We determine the 2-sigma upper limit to the fraction of light arising from the accretion disc to be 27 percent. The effect this has on the binary inclination, determined from modelling the infrared ellipsoidal variations is to increase it

Using CGS4 on UKIRT, we have obtained 2.00-2.45 mu m infrared spectra of a number of low-mass X-ray binaries including Sco X-1, Sco X-2 and GX1 3+1. Sco X-1 shows emission lines only, supporting our previous conclusion that the spectral type of the evolved secondary must be earlier than G5. Emission lines are also seen in the spectrum of Sco X-2

Microvariability observations of two TeV emitting blazars have been made from the Canary Islands International Observatories since 1990. We present a small sample of typical results from the study. We find that, in contrast to the long-term light curve, Mark 501 is more active than Mark 421, suggesting that these, superficially similar objects, are

We describe a data analysis technique for helioseismology that provides a reduction in the contamination of the solar oscillation spectrum from incoherent noise. We show that the technique allows: (i) a significant improvement in the signal-to-noise ratio for the modes in the oscillation power spectrum, and (ii) the solar velocity background

A description is given of the activities of an international working group created with the aim of obtaining both photometric and astrometric observations of visual double and multiple stars with angular separations in the range of one to fifteen arcseconds, that formed part of the HIPPARCOS Input Catalogue. The scientific aims and realisations of