We present results from a spectroscopic survey designed to uncover AM Canum Venaticorum (AM CVn) binaries hidden in the photometric database of the Sloan Digital Sky Survey (SDSS). The discovery of only 7 new AM CVns in the observed part of our sample suggests a lower space density than previously predicted. Based on the complete g≤19 sample, we calculate an observed space...
The SW Sex stars are a class of cataclysmic variables, originally identified because they shared a number of enigmatic properties – most notably, single-peaked emission lines instead of the double-peaked lines one would expect from their high-inclination accretion discs. We present high-time-resolution spectrophotometry of the eclipsing nova-like variables SW Sex and DW UMa, two...
Several authors have shown that precise measurements of transit time variations of exoplanets can be sensitive to other planetary bodies, such as exo-moons. In addition, the transit timing variations of the exoplanets closest to their host stars can provide tests of tidal dissipation theory. These studies, however, have not considered the effect of the host star. There is a large...
Using high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of the eclipsing post-common envelope binary QS Vir, we detect material along the line of sight to the white dwarf at orbital phase ϕ= 0.16. We ascribe this to a stellar prominence originating from the M dwarf secondary star which passes in front of the white dwarf at this phase. This creates sharp...
We present high-speed spectroscopic observations of the intermediate polar (IP) DQ Herculis. Doppler tomography of two He i lines reveals a spiral density structure in the accretion disc around the white dwarf (WD) primary. The spirals look very similar to the spirals seen in dwarf novae during outburst. DQ Her is the first well-established IP in which spirals are seen, which are...
STARLINK distribution Hawaiki and later releases. The STARLINK Software Group homepage can be found at http://starlink.jach.hawaii.edu/starlink. 2 MOLLY was written by T. R. Marsh and is available at http
T. R. Marsh 1 G. Nelemans 0 0 Department of Astrophysics, Radboud University Nijmegen , Nijmegen , the Netherlands 1 Department of Physics, University of Warwick , Coventry CV4 7AL A B S T R A C T
We present spin-resolved spectroscopy of the accreting white dwarf binary V455 And. With a suggested spin period of only 67 s, it has one of the fastest spinning white dwarfs known. To study the spectral variability on the spin period of the white dwarf, we observed V455 And with 2 s integration times, which is significantly shorter than the spin rate of the white dwarf. To...
If recurrent novae are progenitors of Type Ia supernovae, their white dwarfs must have masses close to the Chandrasekhar limit. The most reliable means of determining white dwarf masses in recurrent novae is dynamically, via radial-velocity and rotational-broadening measurements of the companion star. Such measurements require the system to be both eclipsing and to show...
Subdwarf B (sdB) stars are hot, subluminous stars which are thought to be core-helium burning with thin hydrogen envelopes. The mechanism by which these stars lose their envelopes has been controversial, but it has been argued that binary star interaction is the main cause. Over the past decade we have conducted a radial-velocity study of a large sample of sdB stars, and have...
We present time-resolved optical spectroscopy of the dwarf nova GW Librae during its rare 2007 April superoutburst and compare these with quiescent epochs. The data provide the first opportunity to track the evolution of the principal spectral features. In the early stages of the outburst, the optically thick disc dominates the optical and the line components show clear orbital...
I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focusing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If...
shown in Table 1 and Fig. 2. 1 http://starlink.jach.hawaii.edu/starlink. PAMELA has been included since the ‘Hawaiki’ release. 2 MOLLY was written by T. R. Marsh and is available at http://www.warwick
We report on the search for optical bursts from J1819−1458, a member of the recently discovered rotating radio transients (RRATs). J1819−1458 exhibits 3-ms bursts with a peak flux of f1.4 GHzν= 3.6 Jy every ∼3.4 min, implying that it is visible for only ∼1 s per day at radio wavelengths. Assuming that the optical light behaves in a similar manner, the most-sensitive way of...
We have discovered a pulsating DA white dwarf at the lower end of the temperature range 45 000–30 000 K where a few helium atmosphere white dwarfs are known. There are now three such pulsators known, suggesting that a new class of theoretically predicted pulsating white dwarf stars exists. We name them the hot DAV stars. From high-speed photometric observations with the ULTRACAM...
We present high time-resolution multicolour optical observations of the quiescent X-ray transients GRS 1124–684 (=GU Mus) and Cen X-4 (=V822 Cen) obtained with ULTRACAM. Superimposed on the secondary stars' ellipsoidal modulation in both objects are large flares on time-scales of 30–60 min as well as several distinct rapid flares on time-scales of a few minutes, most of which...
The dwarf nova U Gem is unique in having a direct measurement of the K velocity of its white dwarf from Hubble Space Telescope (HST) spectra (K1= 107 ± 2 km s−1 from Long et al.). We present high-resolution optical spectra of U Gem in quiescence taken to test the accuracy to which the HST value can be recovered from optical data. We find that, even with data of very high signal...
Aims. The main goal of this project is to search for p-mode oscillations in a selected sample of DA white dwarfs near the blue edge of the DAV (g-mode) instability strip, where the p-modes should be excited following theoretical models.Methods. A set of high quality time-series data on nine targets has been obtained in 3 photometric bands (Sloan u′, g′, r′) using ULTRACAM at the...
We present 25 new eclipse times of the white dwarf binary NN Ser taken with the high-speed camera ULTRACAM on the William Herschel Telescope and New Technology Telescope, the RISE camera on the Liverpool Telescope and HAWK-I on the Very Large Telescope to test the two-planet model proposed to explain variations in its eclipse times measured over the last 25 yr. The planetary...
