We present early results from the first near-IR imaging of the weak X-ray sources discovered in the recent Chandra/ACIS-I survey towards the Galactic Centre (GC) (Wang et al. 2002). These ~800 discrete sources, which contribute significantly to the GC X-ray emission, represent an important and previously unknown population within the Galaxy. From our VLT observations we will identify likely IR counterparts to a sample of the hardest sources, which are most likely X-ray binaries. With these data we can place constraints on the nature of the discrete weak X-ray source population of the GC. Once the data analysis is complete we will discuss our results in the context of binary population synthesis models.

Photon counting detector technology allows high time resolution spectroscopy on sources such as pulsars and cataclysmic variables. Here we report on first observing trials on Cvs in a high time resolution mode undertaken with the MIC photon counting detector (Fordham et al. 2000) on the 2.1m telescope at San Pedro Martir Observatory.

Hero I use the MHD code, FLASH, from the University of Chicago ASCI Center for Astrophysical Thermonuclear Flashes, to simulate initial two-dimensional simple models of accretion streams in magnetic CVs. These models explore the evolution of inflowing material for two white dwarf masses; 0.5M⊙ and 0.9M⊙. It is seen that a discontinuity forms at a height of 6.1 X 108 cm above the white dwarf ‘surface’ for MWD = 0.5M⊙ and at 1.6 X 109 cm for MWD = 0.9M⊙. These models will be developed further with the ultimate goal of completing a three-dimensional model of magnetic accretion onto a WD surface.

We photometrically observed the 2003 superoutburst of GO Com, which is a candidate for WZ Sge-type dwarf novae (WZ). However, the obtained light curve is atypical of both types: a plateau stage is too short for SU UMa-type dwarf novae (SU) while the amplitude of the superoutburst is too small for WZ. In order to explain this behavior, it might be taken into account that the mass accretion onto the white dwarf is efficient during quiescence.

The masses of compact object (black hole, neutron star) binaries depend strongly on the parameters describing stellar evolution. Such masses or their functions can be measured using gravitational waves or through microlensing searches. We analyze an example of the varying common envelope efficiency and show the dependence of distributions of the measured chirp masses in gravitational waves mass ratios through microlensing taking into account the relevant selection effects.

Cataclysmic Variables (CVs) are close binaries containing a white dwarf primary and a Rochelobe filling red dwarf secondary. In magnetic CVs (MCVs) the white dwarfs have magnetic fields that are sufficiently strong (106 – 108 Gauss) to direct the accretion flow onto the surface of the primary. MCVs are divided into the lower field intermediate polars (IPs) and the higher field polars. Typically, IPs have accretion disks that are disrupted in the center and magnetically channelled flow onto the poles. Polars are diskless, an accretion stream flowing from the inner Lagrangian point impacts directly onto one or both magnetic poles. In addition, polars tend to have white dwarfs which rotate in synchronism with the binary orbit, while IPs have white dwarfs which rotate faster than the binary period. There are a few rare exceptions to this characterization, such as the slightly asynchronous polars and the stream-fed IPs.

We present optical spectroscopy for several old nova candidates that hitherto lacked such observations. V842 Cen, V630 Sgr, XX Tau, CQ Vel, and V840 Oph show typical CV spectra, but V529 Ori is probably misclassified.

V630 Sgr is an eclipsing system with an orbital period of 2.83 h. In spite of the high inclination, the emission lines are not, double-peaked at the resolution of 1 mm.

We present preliminary results of new spectroscopic observations of dwarf nova BZ UMa in quiescence. Fifty medium resolution spectra allow us to reproduce the radial velocity curve from the Hα emission line. We confirm that BZ UMa shows extremely unusual emission lines profiles, Unlike the classical single or the double-peaked profiles usually observed in spectra of dwarf novae, emission lines of BZ UMa consist of at least five peaks.

Medium resolution spectroscopy of nova-like cataclysmic variable UX UMA was performed using the 6-m telescope SAO RAS in April 1999. Obtained spectra cover the total orbital period including eclipse phases and allow us to reproduce the radial velocity curve. The radial-velocity variations of the Hβ emission line are found to have semi-amplitude of about 100 km/s.

We report follow-up observations of the new pre-cataclysmic variable HS 2237+8154, identified from the Hamburg Quasar Survey. The orbital period derived from ellipsoidal modulation observed in the iR-band as well as from the Hα radial velocity variation is orb = 178.10 ± 0.08 min. We briefly discuss the evolutionary state of this system.