We report the results of a time-resolved eclipse mapping of the dwarf nova IP Pegasi during the decline of its May 1993 outburst from HST/FOS fast spectroscopy covering 3 eclipses in the spectral range 1100 – 2500 Å.

The general behaviour of AG DRA was studied in the context of the long-term photometry and radial velocity analysis.

AG DRA is a symbiotic binary with quiescent and active stages; the latter may be explainable by increased thermonuclear burning of a white dwarf accreting from the wind of the cool component.

In our previous studies a second period in addition to the orbital period of 549.7 days has been found for AG DRA. Such a period of about 350 days was indicated in our study using photometry (Friedjung et al. 1998, Petrík et al. 1998)as well as radial velocities (Gális et al. 1999 Friedjung et al. 2003).

Studies of binary evolution have, until recently, neglected thermal timescale mass transfer (TTMT). Recent work has suggested that this previously poorly studied area is crucial in the understanding of systems across the compact binary spectrum. We use the state-of-the-art binary population synthesis code BiSEPS (Willems and Kolb, 2002, MNRAS 337 1004-1016). However, the present treatment of TTMT is incomplete due to the nonlinear behaviour of stars in their departure from gravothermal ‘equilibrium’. Here we show work that should update the ultrafast stellar evolution algorithms within BiSEPS to make it the first pseudo-analytic code that can follow TTMT properly. We have generated fits to a set of over 300 Case B TTMT sequences with a range of intermediate-mass donors. These fits produce very good first approximations to both HR diagrams and mass-transfer rates (see figures 1 and 2), which we later hope to improve and extend. They are already a significant improvement over the previous fits.

WZ Sge- is the prototype of a subclass of dwarf novae with an extremely long recurrence period. In addition, it exhibits rapid oscillations at 27.87 s and 28.96 s. We present our preliminary analysis of XMM-Newton and optical observations taken in 2003 May, almost 2 years after the 2001 outburst.

We present the results of time-series photometry for a sample of candidate pre-cataclysmic variables.

The observations were conducted on 2002-09-17 to 22, 2002-10-16 to 22, 2003-04-08 to 11, 2003-05-13 to 16, and 2003-06-18 to 21, at the 90 cm telescope at CTIO, Chile, using a 2kx2k CCD and a Johnson R filter. Additionally, data for the three targets LBQS 1144+0111, LBQS 1232+1335, and LBQS 1327—0242, were obtained in service mode at the 1.3 m CTIO telescope with ANDICAM. The latter observations consisted in a series of ~2 h runs for each object on five consecutive nights, also in R.

AA DOR, is an eclipsing, close, post common-envelope binary (PCEB) consisting of a sdOB primary star and an unseen secondary with an extraordinary small mass (M2 ≈ 0.066M⊙) formally a brown dwarf (see Rauch 2004 for details). In a spectral analysis of AA DOR, Rauch (2000) determined Teff = 42 kK and log g — 5.2 (cgs). The determination of the components' masses by comparison of these results with evolutionary models of Driebe et al. (1998) shows a discrepancy to masses derived from radial-velocity and the eclipse curves (Hilditch et al. 2003) log g = 5.5 would be necessary in order to achieve an intersection at M1 ≈ 0.330M⊙.

We report results of simulation to evaluate the ability of the eclipse mapping method to reproduce the spatial distribution of flickering in cataclysmic variables stars.

Flickering is a fast intrinsic brightness scintilation occurring on time scales from seconds to minutes with amplitudes of 0.01 - 1 mag. Flickering is observed in all sources believed to be powered by accretion is considered a fundamental signature of accretion. Nevertheless, it is one of the least undestood aspects of the accretion process.

We combine HST and ground-based parallaxes for cataclysmic variables (CVs) to examine their outburst energetics, as well as the nature of their secondary stars. Harrison et al. (2004) have recently published parallaxes for WZ Sge, YZ Cnc, and RU Peg, and have reanalyzed the HST parallaxes for U Gem, SS Aur, and SS Cyg. Combined with existing HST parallaxes for RW Tri (MeArthur et al. 1999), TV Col (MeArthur et al. 2001), EX Hya and V1223 Sgr (Beuermann et al. 2004a,b), ten high-quality parallaxes are available to constrain the various types of outbursts of CVs. In addition, Thorstensen (2003) has published ground-based parallaxes for fourteen CV systems.

We have recently completed an infrared (K-band) spectroscopic survey of two dozen cataclysmic variables. The systems range in orbital period from Рorb = 1-35 hr (EF Eri), to Рorb = 11.0 hr (V442 Cen). We detect the secondary star in every system.

Nearly all of the CVs in which we can clearly see the secondary have weak CO features. Most show evidence for enhanced levels of 13CO. In addition, we see apparent enhancements and/or deficits of such species as sodium, calcium, titanium, magnesium, silicon, and iron. In addition, we find a few lines that we have been unable to identify (such as the strong feature we call “cataclysmicum” at 2.2767 μm seen in the spectrum of EF Eri, and two other very short period CVs).

We use simultaneous multi-wavelength BVRI-JHK photometric observations of cataclysmic variables (CVs) to determine the inclination angles of the systems, together with phase-resolved spectroscopy to calculate the K2 and vsini. We then calculate the masses of the system components. We are using these data to construct mass-radius diagrams of the secondaries in an effort to resolve some of the debate over their evolutionary history.

We present initial results of a survey of the FUV spectra of disk-accreting cataclysmic variables obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).

FUSE covers the 905 - 1188 Å range at spectral resolutions ≃0.1 Å. To date, FUSE has observed more than 65 cataclysmic variables (CVs). Publicly-available data include observations of 11 dwarf novae (DN), 15 non-magnetic novalikes (NLs), 7 intermediate polars and DQ Her stars, at least 15 polars, and 4 super-soft X-ray binaries.

The Hubble Space Telescope observations showed that some nova outbursts may not produce smooth shells of gas, but thousands of gaseous blobs. In the case of T Pyx the blobs are distributed in eight concentric circles around the exploding star, producing a pattern similar to tree rings. We explore here the formation of the tree rings by hydrodynamical simulations.

The Faint Sky Variability Survey (FSVS) is aimed at rinding photometrically and astrometrically variable objects. The main goal is to get a better understanding of binary evolution. This survey consists of 78 fields, which covers a total area of 21 deg2 in the sky and it is sensitive for objects in the magnitude range of 17 < V < 24. (For a description see Groot et al. 2003).

A better understanding of the AM CVn population is crucial to constrain their candidacy as SN Ia progenitors, to test binary evolution (in particular the common-envelope phase), and to predict their observable gravitational radiation signature. An AM CVn dedicated search in the Sloan Digital Sky Survey-DRl resulted in the discovery of SDSS J124058.03-015919.2, a new AM CVn candidate previously identified as a DB white dwarf in the 2dF quasar survey.

Models for AM CVn discs are usually constructed under the assumption of a steady state. Nevertheless, many of these systems have unstable discs. We have constructed models for the spectral evolution of such discs using a disc instability code (Cannizzo 1984) and detailed calculations of the vertical disc structure assuming hydrostatic equilibrium following El-Khoury and Wickramasinghe (2000).

Evolutionary calculations indicate that there should be no peculiar abundances on the companion star resulting from the common envelope epoch if accretion efficiencies are low. Indeed, we find no evidence for peculiar abundances from archival ASCA data, although uncertainties are high. We find that a single-temperature plasma model does not fit the data. Two-temperature models with decoupled elemental abundances suggest that Fe is underabundant compared to the Hyades photospheric mean. In the absence of a measurement of photospheric Ne abundance in the cluster, we find Ne is overabundant compared to the solar photospheric value. This is indicative of the inverse first ionization potential effect. Differences between coronal and photospheric abundances are believed to result from the fractionation of ionized and neutral material in the upper atmosphere of the star. Care must be taken to include this effect when inferring photospheric abundances from X-ray data (e.g., Sarna 2004).

Using the disc instability model (DIM) and a simple but reasonable model for the X-ray, extreme UV, UV and optical emission we investigate the multi-wavelength properties of dwarf novae. We discuss the predictions of the model in the context of the observationally best studied systems, i.e. SS Cyg and VW Hyi. We use the version of the DIM described in Buat-Ménard et al. (2001). The local spectrum of the emission from the disc is assumed to be given by Kurucz (1993,VizieR On-line Data Catalog). We also take into account emission from the (irradiated) secondary, the white dwarf, the hot spot, and the boundary layer.

The dependence of the N III 4641/4635 line ratio on the electron density is presented. It is shown that this ratio may be an important diagnostic tool in cataclysmic variables.

Pérez-Tijerina, Bohigas & Machorro (2001) used the Chianti code and database developed by the U.S. Nautical Observatory (Landi, 200) in order to find density and temperature sensitive line ratios in the conditions occuring in plasmas produced in pulsed laser deposition experiments for thin film deposition, i.e., around 1018 cm 3 and 104 K. Level populations are determined considering only radiative decay and collisional excitation and de-excitation.

Our time-series photometric observations of a short outburst of HT Cam in 2001 strongly suggest that disk instabilities occurred during the outburst.

HT Cam is a cataclysmic variable identified as the optical counterpart of the hard X-ray source RX J0757.0+6306, discovered during the ROSAT All-Sky Survey. Tovmassian et al. (1998) suggested that this object is an intermediate polar with a shortest orbital period of 80.92min and a spin period of 8.52min. However, the existence of dwarf nova-like outbursts and the short orbital period allowed an alternative interpretation that it may be an SU UMa-type dwarf nova or WZ Sge-type stars (Tovmassian et al. 1998).

We numerically simulate the surface flow of a gas-supplying companion star in a semi-detached binary system and construct the Doppler map. Our numerical results indicate an eddy configuration composed of a Heddy, a L1-eddy, and a L2-eddy associated with high/low pressures on the surface of the companion star. We find that the formation of these eddies can be explained in terms of the astrostrophic wind. We apply our calculations to the Galactic supersoft X-ray source RX J0019.8+2156. This object is very attractive for the present study since the observed Doppler map might reflect the surface flow on the companion star. We have constructed the Doppler map of RX J0019.8+2156 and compare it with observations.