Orbital phase dependent IUE spectra of the nova like binary II Arietis

Nine low dispersion IUE spectra of the nova like binary TT Ari over its 3h17m orbital period were obtained. Four short wave spectra and five long wave spectra exhibit marked changes in line strength and continuum shape with orbital phase. The short wave spectra show the presence in absorption of C III, Lyman alpha, SiIII, NV, SiIV, CIV, HeII, AlIII, and NIV. The CIV shows a P Cygni profile on two of the spectra. Implications of these spectra for the nature of nova like variables are discussed

The boundary layer of VW Hyi in quiescence

In this letter, we suggest that the missing boundary layer luminosity of dwarf novae in quiescence is released mainly in the ultraviolet (UV) as the second component commonly identified in the far ultraviolet (FUV) as the "accretion belt". We present the well-studied SU UMa-type system VW Hyi in detail as a prototype for such a scenario. We consider detailed multiwavelength observations and in particular the recent FUSE observations of VW Hyi which confirm the presence of a second component (the "accretion belt") in the FUV spectrum of VW Hyi in quiescence. The temperature (50,000K) and rotational velocity (> 3,000km/s) of this second FUV component are entirely consistent with the optically thick region (tau = 1) located just at the outer edge of optically thin boundary layer in the simulations of Popham (1999). This second component contributes 20% of the FUV flux, therefore implying a boundary layer luminosity: $L_{BL} = 2 \times (0.2 \times L_{UV} + L_{X-ray}) = 0.6 \times L_{disc}$, while the theory (Klu\'zniak 1987) predicts, for the rotation rate of VW Hyi's WD, $L_{BL} \approx 0.77 L_{disc}$. The remaining accretion energy ($<0.1 L_{acc}$) is apparently advected into the star as expected for optically thin advection dominated boundary layers. This scenario is consistent with the recent simultaneous X-ray and UV observations of VW Hyi by (Pandel, C\'ordova & Howell 2003), from which we deduced here that the alpha viscosity parameter in the boundary layer region must be as small as $\alpha \approx 0.004$.Comment: 4 page

Visible-band and IUE observations of mu Sagittarii

H alpha and U band photometry and IUE spectra of the binary system mu Sagittarii are discussed. An estimate of mass-loss is made from the observed P Cygni profiles. There are indications of pulsation in the supergiant B8 component

White Dwarfs in Cataclysmic Variables: An Update

In this review, we summarize what is currently known about the surface temperatures of accreting white dwarfs in nonmagnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. We focus only on white dwarf surface temperatures, since in the area of chemical abundances, rotation rates, WD masses and accretion rates, relatively little has changed since our last review, pending the results of a large HST GO programinvolving 48 CVs of different CV types. The surface temperature of the white dwarf in SS Cygni is re-examined in the light of its revised distance. We also discuss new HST spectra of the recurrent nova T Pyxidis as it transitioned into quiescence following its April 2011 nova outburst

IUE observations of a hot DAO white dwarf: Implications for diffusion theory and photospheric stratification

Observations of the DAO white dwarf PG1210+533, including the first high dispersion spectrum of a hybrid H-He object of this nature were obtained by IUE. In contrast with hot DAs in the 50,000 K temperature range, PG1210+533 shows no narrow interstellar-like metal lines, in spite of an optically observed He/H abundance of 0.1. This lack of metal makes accretion from the ISM an unlikely source for the He in the PG1210+533 photosphere. A significant discovery in the high dispersion spectrum is the existence of a sharp, non-LTE like, core seen in the He II 1640 line. Such features are detected in DO white dwarfs. A small aperture SWP low dispersion observation reveals the Lyman alpha profile of PG1210+533 to be surprisingly weak and narrow. Fits of this profile using pure H models yielded a T(eff) = 56,000 K. Fits of the Balmer H gamma profile however, yield T(eff) = 42,300 K and log g = 8.5 + or - 0.5 for the same models. It is unlikely that homogeneously mixed H-He atmospheres can resolve the inconsistency between the Lyman alpha and H gamma features in this star. Stratified models involving thin H photospheres may be necessary to explain these results