ABSTRACT. Two identical new instruments, the Sutherland High-speed Optical Cameras (SHOC), have been developed for use on the South African Astronomical Observatory's (SAAO) 1.9, 1.0 and 0.75 m telescopes at Sutherland. The SHOC systems are fast-frame-rate, accurately-timed, high-quality, visible-wavelength imagers. Each system consists of a camera, global positioning system (GPS), control computer and peripherals. The primary component is an Andor iXon X3 888 UVB camera, utilizing a 1024 × 1024 pixel, frame-transfer, thermoelectrically-cooled, back-illuminated CCD. One of SHOC's most important features is that it can achieve frame rates of between 1 and 20 frames/s during normal operation (dependent on binning and subframing) with microsecond timing accuracy on each frame (achieved using frame-by-frame GPS triggering). Frame rates can be increased further, and fainter targets observed, by making use of SHOC's electron-multiplying (EM) modes. SHOC is therefore ideally suited to time domain astronomy where high frame rates and extremely accurate timing are critical. Here, we present details of the instrument components, characteristics measured during commissioning, science demonstrations, and development plans. Attention is specifically given to exploration of the signal-to-noise (S/N) parameter space as a function of EM and conventional modes. These results enable observers to optimize instrumental settings for their observations and clearly demonstrate the advantages and potential pitfalls of the EM modes.

The latest outburst of the recurrent nova RS Oph occurred in 2006 February. Photometric data presented here show evidence of the resumption of optical flickering, indicating re-establishment of accretion by day 241 of the outburst. Magnitude variations of up to 0.32 mag in V-band and 0.14 mag in B on timescales of 600-7000 s are detected. Over the two week observational period we also detect a 0.5 mag decline in the mean brightness, from V~11.4 to V~11.9, and record B~12.9 mag. Limits on the mass accretion rate of ~10^{-10} to 10^{-9} Msun/yr are calculated, which span the range of accretion rates modeled for direct wind accretion and Roche lobe overflow mechanisms. The current accretion rates make it difficult for thermonuclear runaway models to explain the observed recurrence interval, and this implies average accretion rates are typically higher than seen immediately post-outburst.Comment: 5 pages, 5 figures, accepted for publication in MNRA

The eruption of the recurrent nova U Scorpii on 28 January 2010 is now the all-time best observed nova event. We report 36,776 magnitudes throughout its

Using six years of spectroscopic monitoring of the luminous quasar HE 0435-4312 (z = 1.2231) with the Southern African Large Telescope, in combination with photometric data (CATALINA, OGLE, SALTICAM, and BMT), we determined a rest-frame time delay of days between the Mg ii broad-line emission and the ionizing continuum using seven different time-delay inference methods. Time-delay artifact peaks and aliases were mitigated using the bootstrap method and prior weighting probability function, as well as by analyzing unevenly sampled mock light curves. The Mg ii emission is considerably variable with a fractional variability of ∼5.4%, which is comparable to the continuum variability (∼4.8%). Because of its high luminosity (L 3000 = 1046.4 erg s−1), the source is beneficial for a further reduction of the scatter along the Mg ii-based radius–luminosity relation and its extended versions, especially when the highly accreting subsample that has an rms scatter of ∼0.2 dex is considered. This opens up the possibility of using the high-accretor Mg ii-based radius–luminosity relation for constraining cosmological parameters. With the current sample of 27 reverberation-mapped sources, the best-fit cosmological parameters (Ωm, ΩΛ) = (0.19; 0.62) are consistent with the standard cosmological model within the 1σ confidence level.

Results for the remaining zones of the Edinburgh-Cape (EC) Blue Object survey are presented. These are incomplete, but lie in that part of the South Galactic Cap between 50 • and 90 • from the Galactic plane and south of about −12. • 3 of declination. This part of the survey comprises 79 UK Schmidt Telescope fields covering about 2150 deg 2 , in which we find 536 blue objectsincluding hot subdwarfs (∼33 per cent), white dwarfs (∼30 per cent), binaries (∼12 per cent), cataclysmic variables (∼1.5 per cent) and some 'star-like' galaxies (∼12 per cent). A further 254 stars observed in the survey, mainly low-metallicity F-and G-type stars, are also listed. Low-dispersion spectroscopic classification is given for all the hot objects and UBV photometry for most of them. Either spectroscopy or photometry is listed for the cooler types.

We present UKIRT UIST spectra of Sakurai's Object (= V4334 Sgr) showing CO fundamental‐band absorption features around 4.7 μm. The line centres are at a heliocentric radial velocity of −170 ± 30 km s−1. The number and relative strengths of the lines indicate a CO gas temperature of 400 ± 100 K and a CO column density of 7+3−2× 1017 cm−2. The gas was moving away from the central star at an average speed of ∼290 ± 30 km s−1 in 2003 September. The lines appeared sometime between mid‐1999 (well after the opaque dust shell formed) and mid‐2000, and may have been somewhat more blueshifted initially than they are now. The observed CO velocity and temperature indicate the continued presence of a fast wind in the object, previously seen in the He i 1.083‐μm line beginning just prior to massive dust formation, and more recently in atomic and ionized lines. The dust continuum is consistent with a temperature of 350 ± 30 K, indicating continued cooling of the shell. The similar CO temperature suggests that the bulk of the CO absorption occurs just outside the dust continuum surface.

No abstract

We present follow-up observations of pulsating subdwarf B (sdB) stars as part of our efforts to resolve the pulsation spectra for use in asteroseismological analyses. This paper reports on multisite campaigns of the pulsating sdB stars PG 1618+563B and PG 0048+091. Data were obtained from observatories placed around the globe for coverage from all longitudes. For PG 1618+563B, our five-site campaign uncovered a dichotomy of pulsation states: Early during the campaign the amplitudes and phases (and perhaps frequencies) were quite