Abstract.A series of 59 moderate-resolution high signal-to-noise spectra of the pulsating helium star V652 Her covering 1.06 pulsation cycles was obtained with the William Herschel Telescope. These have been supplemented by archival ultraviolet and visual spectrophotometry and used to make a time-dependent study of the properties of V652 Her throughout the pulsation cycle. This study includes the following features: the most precise radial velocity curve for V652 Her measured so far, new software for the automatic measurement of effective temperature, surface gravity and projected rotation velocities from moderate-resolution spectra, self-consistent high-precision measurements of effective temperature and surface gravity around the pulsation cycle, a demonstration of excessive line-broadening at minimum radius and evidence for a pulsation-driven shock front, a new method for the direct measurement of the radius of a pulsating star using radial velocity and surface gravity measurements alone, new software for the automatic measurement of chemical abundances and microturbulent velocity, updated chemical abundances for V652 Her compared with previous work (Paper IV), a reanalysis of the total flux variations (cf. Paper II) in good agreement with previous work, and revised measurements of the stellar mass and radius which are similar to recent results for another pulsating helium star, BX Cir. Masses measured without reference to the ultraviolet fluxes turn out to be unphysically low (∼0.18 M ). The best estimate for the dimensions of V652 Her averaged over the pulsation cycle is given by: T eff = 22 930 ± 10 K and log g = 3.46 ± 0.05 (ionization equilibrium), T eff = 20 950 ± 70 K (total flux method), R = 2.31 ± 0.02 R , L = 919 ± 14 L , M = 0.59 ± 0.18 M and d = 1.70 ± 0.02 kpc. Two significant problems were encountered. The line-blanketed hydrogen-deficient model atmospheres used yield effective temperatures from the optical spectrum (ionization equilibrium) and visual and UV photometry (bolometric flux) that are inconsistent. Secondly, the IUE spectra are poorly distributed in phase and have low signal-to-noise. These problems may introduce systematic errors of up to 0.1 M .

We present an analysis of high-speed spectroscopy of the pulsating subdwarf B star PG 1605+072. Periodic radial motions are detected at frequencies similar to those reported for photometric variations in the star, with amplitudes of up to 6 km/s. Differences between relative strengths for given frequency peaks for our velocity data and previously measured photometry are probably a result of shifting of power between modes over time. Small differences in the detected frequencies may also indicate mode-shifting. We report the detection of line-shape variations using the moments of the cross correlation function profiles. It may be possible to use the moments to identify the star's pulsation modes.Comment: 5 pages, 6 figure

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INTEGRAL is an optical fiber unit for performing 2D spectroscopy ofextended objects at the 4.2m. William Herschel Telescope (WHT). It is mounted at the GHRIL Nasmyth focus together with newly built acquisition, guiding, and calibration units. It makes use of the specially designed fiber spectrograph WYFFOS. This system allows up to six bundles to be mounted simultaneously. It currently contains three science oriented fiber bundles, any one of which can be easily and quickly placed in the telescope beam. Their spatial resolution elements (fiber core diameters) are O".45, O".9, and 2".T, respectively. Hence, depending on the prevailing seeing conditions the instrument can be easily optimized for the scientific program. INTEGRAL was succesfully commissioned at the WilT during a six night period in July 1997. Here we will discuss its main characteristics.

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