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BackgroundThere is currently limited evidence regarding the potential complications of sphenopalatine artery ligation. The post-operative outcomes at two secondary care centres over a 10-year period were reviewed.MethodsA retrospective review was undertaken of patients undergoing emergency and elective sphenopalatine artery ligation between January 2011 and January 2021. Their demographics, peri-operative care and post-operative outcomes were recorded. The median follow-up time was 54 days (range, 0–2657 days).ResultsNinety-one patients were included. Four patients (4.4 per cent) had a septal perforation at post-operative review. Nineteen patients (20.9 per cent) had post-operative bleeding that extended their in-patient stay, with five patients (5.5 per cent) requiring revision surgery. Pre-operative non-dissolvable nasal packing was used a median of 1 time (range, 0–8 times).ConclusionFurther research on outcomes of sphenopalatine artery ligation is needed. Pre-operative non-dissolvable nasal packing, concurrent septal surgical procedures, surgical techniques, and co-morbidities such as hypertension represent potential confounding factors that could not be further assessed in this small, retrospective study.

We present results of the long-term multi-wavelength study of optical, UV and X-ray variability of the nearby changing-look (CL) Seyfert NGC 1566 observed with the Swift Observatory and the MASTER Global Robotic Network from 2007 to 2019. We started spectral observations with South African Astronomical Observatory 1.9-m telescope soon after the brightening was discovered in July 2018 and present here the data for the interval between Aug. 2018 to Sep. 2019. This paper concentrates on the remarkable post-maximum behaviour after July 2018 when all bands decreased with some fluctuations. We observed three significant re-brightenings in the post-maximum period during 17 Nov. 2018 - 10 Jan. 2019, 29 Apr. - 19 Jun. 2019 and 27 Jul.- 6 Aug. 2019. An X-ray flux minimum occurred in Mar. 2019. The UV minimum occurred about 3 months later. It was accompanied by a decrease of the Luv/Lx ratio. New post-maximum spectra covering (31 Nov. 2018 - 23 Sep. 2019) show dramatic changes compared to 2 Aug. 2018, with fading of the broad lines and [Fe X]6374 until Mar. 2019. These lines became somewhat brighter in Aug.-Sep. 2019. Effectively, two CL states were observed for this object: changing to type 1.2 and then returning to the low state as a type 1.8 Sy. We suggest that the changes are due mostly to fluctuations in the energy generation. The estimated Eddington ratios are about 0.055% for minimum in 2014 and 2.8% for maximum in 2018., Comment: 11 pages, 9 figured, accepted for publication in MNRAS

We summarize a study of optical, UV and X-ray light curves of the nearby changing look active galactic nucleus in the galaxy NGC 1566 obtained with the Neil Gehrels Swift Observatory and the MASTER Global Robotic Network over the period 2007-2019. We also report on optical spectroscopy using the South African Astronomical Observatory 1.9-m telescope between Aug. 2018 and Mar. 2019. A substantial increase in X-ray flux by 1.5 orders of mag- nitude was observed following the brightening in the UV and optical bands during the first half of 2018 year. After a maximum was reached at the beginning of July 2018, the fluxes in all bands decreased with some fluctuations. The most remarkable re-brightenings in of the light curve following the decline from the bright phase were observed at MJD range 58440-58494 and 58603-58654. The amplitude of the flux variability is strongest in the X-ray band and decreases with increasing wavelength. Low-resolution spectra (Aug 2018) reveal a dramatic strengthening of the broad emission as well as high-ionization [FeX]6374 lines. These lines were not detected so strongly in the past published spectra. The change in the type of the opti- cal spectrum was accompanied by a significant change in the X-ray spectrum. For the last optical spectra (31 Nov. 2018 – 28 Mar. 2019) we see dramatic changes compared to 2 Aug 2018, accompanied by the fading of broad emission lines and high-ionization [FeX]6374 line. Effectively, two changing look (CL) cases were observed for this object: changing to Sy1.2 type and then returning to the low state as Sy 1.8–Sy1.9 type. Some possible explanations of the observed dramatic changes are discussed.

We present a study of optical, UV and X-ray light curves of the nearby changing look active galactic nucleus in the galaxy NGC 1566 obtained with the Neil Gehrels Swift Observatory and the MASTER Global Robotic Network over the period 2007 - 2018. We also report on our optical spectroscopy at the South African Astronomical Observatory with the 1.9-m telescope on the night 2018 August 2-3. A substantial increase in X-ray flux by 1.5 orders of magnitude was observed following the brightening in the UV and optical bands during the last year. After a maximum was reached at the beginning of 2018 July the fluxes in all bands decreased with some fluctuations. The amplitude of the flux variability is strongest in the X-ray band and decreases with increasing wavelength. Low-resolution spectra reveal a dramatic strengthening of the broad emission as well as high-ionization [FeX]6374 A lines. These lines were not detected so strongly in the past published spectra. The change in the type of the optical spectrum was accompanied by a significant change in the X-ray spectrum. All these facts confirm NGC 1566 to be a changing look Seyfert galaxy., Comment: 7 pages, 5 figures

Tokamak turbulence, driven by the ion-temperature gradient and occurring in the presence of flow shear, is investigated by means of local, ion-scale, electrostatic gyrokinetic simulations (with both kinetic ions and electrons) of the conditions in the outer core of the Mega-Ampere Spherical Tokamak (MAST). A parameter scan in the local values of the ion-temperature gradient and flow shear is performed. It is demonstrated that the experimentally observed state is near the stability threshold and that this stability threshold is nonlinear: sheared turbulence is subcritical, i.e. the system is formally stable to small perturbations, but, given a large enough initial perturbation, it transitions to a turbulent state. A scenario for such a transition is proposed and supported by numerical results: close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Whereas this appears to represent a new scenario for transition to turbulence in tokamak plasmas, it is reminiscent of the behaviour of other subcritically turbulent systems, e.g. pipe flows and Keplerian magnetorotational accretion flows., 16 pages, 5 figures, accepted to Journal of Plasma Physics

We investigate the effect of varying the ion temperature gradient (ITG) and toroidal equilibrium scale sheared flow on ion-scale turbulence in the outer core of MAST by means of local gyrokinetic simulations. We show that nonlinear simulations reproduce the experimental ion heat flux and that the experimentally measured values of the ITG and the flow shear lie close to the turbulence threshold. We demonstrate that the system is subcritical in the presence of flow shear, i.e., the system is formally stable to small perturbations, but transitions to a turbulent state given a large enough initial perturbation. We propose that the transition to subcritical turbulence occurs via an intermediate state dominated by low number of coherent long-lived structures, close to threshold, which increase in number as the system is taken away from the threshold into the more strongly turbulent regime, until they fill the domain and a more conventional turbulence emerges. We show that the properties of turbulence are effectively functions of the distance to threshold, as quantified by the ion heat flux. We make quantitative comparisons of correlation lengths, times, and amplitudes between our simulations and experimental measurements using the MAST BES diagnostic. We find reasonable agreement of the correlation properties, most notably of the correlation time, for which significant discrepancies were found in previous numerical studies of MAST turbulence., 67 pages, 37 figures. Submitted to PPCF

The flow shear associated with the differential toroidal rotation of tokamak plasmas breaks an underlying symmetry of the turbulent fluctuations imposed by the up-down symmetry of the magnetic equilibrium. Using experimental Beam-Emission-Spectroscopy (BES) measurements and gyrokinetic simulations, this symmetry breaking in ion-scale turbulence in MAST is shown to manifest itself as a tilt of the spatial correlation function and a finite skew in the distribution of the fluctuating density field. The tilt is a statistical expression of the "shearing" of the turbulent structures by the mean flow. The skewness of the distribution is related to the emergence of long-lived density structures in sheared, near-marginal plasma turbulence. The extent to which these effects are pronounced is argued (with the aid of the simulations) to depend on the distance from the nonlinear stability threshold. Away from the threshold, the symmetry is effectively restored.

New results from MAST are presented that focus on validating models in order to extrapolate to future devices. Measurements during start-up experiments have shown how the bulk ion temperature rise scales with the square of the reconnecting field. During the current ramp up models are not able to correctly predict the current diffusion. Experiments have been performed looking at edge and core turbulence. At the edge detailed studies have revealed how filament characteristic are responsible for determining the near and far SOL density profiles. In the core the intrinsic rotation and electron scale turbulence have been measured. The role that the fast ion gradient has on redistributing fast ions through fishbone modes has led to a redesign of the neutral beam injector on MAST Upgrade. In H-mode the turbulence at the pedestal top has been shown to be consistent with being due to electron temperature gradient modes. A reconnection process appears to occur during ELMs and the number of filaments released determines the power profile at the divertor. Resonant magnetic perturbations can mitigate ELMs provided the edge peeling response is maximised and the core kink response minimised. The mitigation of intrinsic error fields with toroidal mode number n>1 has been shown to be important for plasma performance., 34 pages, 10 figures. This is an author-created, un-copyedited version of an article submitted for publication in Nuclear Fusion. IoP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it

The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ~ 1.3) with similar poloidal cross-section to other medium-size tokamaks. The physics programme concentrates on addressing key physics issues for the operation of ITER, design of DEMO and future spherical tokamaks by utilising high resolution diagnostic measurements closely coupled with theory and modelling to significantly advance our understanding. An empirical scaling of the energy confinement time that favours higher power, lower collisionality devices is consistent with gyrokinetic modelling of electron scale turbulence. Measurements of ion scale turbulence with beam emission spectroscopy and gyrokinetic modelling in up-down symmetric plasmas find that the symmetry of the turbulence is broken by flow shear. Near the non-linear stability threshold, flow shear tilts the density fluctuation correlation function and skews the fluctuation amplitude distribution. Results from fast particle physics studies include the observation that sawteeth are found to redistribute passing and trapped fast particles injected from neutral beam injectors in equal measure, suggesting that resonances between the m = 1 perturbation and the fast ion orbits may be playing a dominant role in the fast ion transport. Measured D–D fusion products from a neutron camera and a charged fusion product detector are 40% lower than predictions from TRANSP/NUBEAM, highlighting possible deficiencies in the guiding centre approximation. Modelling of fast ion losses in the presence of resonant magnetic perturbations (RMPs) can reproduce trends observed in experiments when the plasma response and charge-exchange losses are accounted for. Measurements with a neutral particle analyser during merging-compression start-up indicate the acceleration of ions and electrons. Transport at the plasma edge has been improved through reciprocating probe measurements that have characterised a geodesic acoustic mode at the edge of an ohmic L-mode plasma and particle-in-cell modelling has improved the interpretation of plasma potential estimates from ball-pen probes. The application of RMPs leads to a reduction in particle confinement in L-mode and H-mode and an increase in the core ionization source. The ejection of secondary filaments following type-I ELMs correlates with interactions with surfaces near the X-point. Simulations of the interaction between pairs of filaments in the scrape-off layer suggest this results in modest changes to their velocity, and in most cases can be treated as moving independently. A stochastic model of scrape-off layer profile formation based on the superposition of non-interacting filaments is in good agreement with measured time-average profiles. Transport in the divertor has been improved through fast camera imaging, indicating the presence of a quiescent region devoid of filament near the X-point, extending from the separatrix to ψ n ~ 1.02. Simulations of turbulent transport in the divertor show that the angle between the divertor leg on the curvature vector strongly influences transport into the private flux region via the interchange mechanism. Coherence imaging measurements show counter-streaming flows of impurities due to gas puffing increasing the pressure on field lines where the gas is ionised. MAST Upgrade is based on the original MAST device, with substantially improved capabilities to operate with a Super-X divertor to test extended divertor leg concepts. SOLPS-ITER modelling predicts the detachment threshold will be reduced by more than a factor of 2, in terms of upstream density, in the Super-X compared with a conventional configuration and that the radiation front movement is passively stabilised before it reaches the X-point. 1D fluid modelling reveals the key role of momentum and power loss mechanisms in governing detachment onset and evolution. Analytic modelling indicates that long legs placed at large major radius, or equivalently low at the target compared with the X-point are more amenable to external control. With MAST Upgrade experiments expected in 2019, a thorough characterisation of the sources of the intrinsic error field has been carried out and a mitigation strategy developed.

We report the detection of short period variations in the stars HD69013 and HD96237. These stars possess large overabundances of rare earth elements and global magnetic fields, thus belong to the class of chemically peculiar Ap stars of the main sequence. Pulsations were found from analysis of high time resolution spectra obtained with the ESO Very Large Telescope using a cross correlation method for wide spectral bands, from lines belonging to rare earth elements and from the H alpha core. Pulsation amplitudes reach more than 200 m/s for some lines in HD69013 with a period of 11.4 min and about 100m/s in HD96237 with periods near 13.6 min. The pulsations have also been detected in photometric observations obtained at the South African Astronomical Observatory.

We present homogeneous, standardized UBV(RI)C photometry for over 700 nearby stars selected on the basis of Hipparcos parallaxes. Additionally, we list JHK photometry for about half of these stars, as well as L photometry for 86 of the brightest. A number of stars with peculiar colours or anomalous locations in various colour–magnitude diagrams are discussed.

We present a detailed study of the pulsation of alpha Circini, the brightest of the rapidly oscillating Ap stars. We have obtained 84 days of high-precision photometry from four runs with the star tracker on the WIRE satellite. Simultaneously, we collected ground-based Johnson B observations on 16 nights at the South African Astronomical Observatory. In addition to the dominant oscillation mode at 2442 microHz, we detect two new modes that lie symmetrically around the principal mode to form a triplet. The average separation between these modes is 30.173+-0.004 microHz and they are nearly equidistant with the separations differing by only 3.9 nHz. We compare the observed frequencies with theoretical pulsation models based on constraints from the recently determined interferometric radius and effective temperature, and the recently updated Hipparcos parallax. We show that the theoretical large separations for models of alpha Cir with global parameters within the 1-sigma observational uncertainties vary between 59 and 65 microHz. This is consistent with the large separation being twice the observed value, indicating that the three main modes are of alternating even and odd degrees. The frequency differences in the triplet are significantly smaller than those predicted from our models, for all possible combinations of mode degrees, and may indicate that the effects of magnetic perturbations need to be taken into account. The WIRE light curves are modulated by a double wave with a period of 4.479 days, and a peak-to-peak amplitude of 4 mmag. This variation is due to the rotation of the star and is a new discovery, made possible by the high precision of the WIRE photometry. The rotational modulation confirms an earlier indirect determination of the rotation period., Comment: Accepted by MNRAS. The resolution of Figs. 1 and 5 has been degraded. Abstract abridged. 14 pages, 10 Figs

We have discovered that at least one component of the visual binary star HD 218994AB is a δ Sct star. The primary star of this system is a known rapidly oscillating Ap (roAp) star; therefore, it is possible that it is both an roAp star and a δ Sct star – a hybrid. There are no confirmed such hybrid roAp–δ Sct stars, and they are predicted theoretically not to exist. More probably, HD 218994B is the δ Sct star, as it is 0.54 mag fainter than the primary and also lies in the δ Sct instability strip. It then offers the potential to determine Teff and L for the primary which appears to be one of the more evolved roAp stars and an important test the theoretically calculated roAp star instability strip. In this case, the system also is important since the stars are a co-eval pair of very similar mass, yet one is a magnetic roAp star and the other is probably a non-magnetic δ Sct star with a normal spectrum. We detect a significant longitudinal magnetic field strength of 440 ± 23 G in the roAp star HD 218994A. We also present the first measurement of the longitudinal magnetic field strength for the δ Sct star HD 21190, the most-evolved Ap star known. We obtain a formally significant value of 47 ± 13 G. If confirmed, this will make HD 21190 the first magnetic δ Sct star known.

Recently, we discovered an entirely new type of variability in the upper atmospheres of rapidly oscillating Ap (roAp) stars. This manifests itself in amplitude modulation of the radial velocities that has not been previously detected in photometric studies of the same stars. To study this new variability further we obtained a full night, 8.85 h, of high time resolution (70s), high spectral resolution (R = 105 000), high signal-to-noise ratio (on average S/N ∼ 130) data with Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) for the roAp star HD 134214. We also obtained 4.2 h of new photometric data in Johnson B with the South African Astronomical Observatory (SAAO) 0.5-m telescope 2d later. HD 134214 has been known for years to be singly periodic with a relatively stable amplitude in photometry; it has the highest pulsation frequency of any roAp star of 2.949 mHz (P = 5.65 min). Our new UVES data show this principal frequency, plus five other frequencies in amplitude spectra of rare earth elements lines and the Ha line. The new frequencies are stable over the 8.85 h of observation, and the highest of them v 2 = 2.782 mHz is the same as found in data taken 2 yr earlier with UVES presented in the discovery paper. The amplitudes of the new frequencies drop faster with atmospheric depth than does the amplitude of the principal frequency, hence explaining why they are generally not seen in broad-band photometric measurements that sample on average more deeply in the atmosphere. Our new photometric measurements also detect v 2 for the first time in photometric data. Our analysis suggests that the new frequencies are associated with pulsation modes, but the nature of those modes and why they increase in amplitude with atmospheric height more strongly than the principal frequencies is not yet known.

We present homogeneous and standardized UBV(RI)C JHK photometry for over 100 M stars selected from an earlier paper on the basis of apparent photometric constancy. L photometry has been obtained for stars brighter than about L = 6. Most of the stars have a substantial number of UBV(RI)C observations and, it is hoped, will prove useful as red supplementary standards. Additionally, we list JHK photometry for nearly 300 Hipparcos red stars not selected as standards, as well as L photometry for the brightest stars.

We describe briefly the properties of the recently completed Southern African Large Telescope (SALT), along with its first light imager SALTICAM. Using this instrument, we present 4.3 hr of high speed unfiltered photometric observations of the eclipsing polar SDSSJ015543.40+002807.2 with time resolution as short as 112 ms, the highest quality observations of this kind of any polar to date. The system was observed during its high luminosity state. Two accreting poles are clearly seen in the eclipse light curve. The binary system parameters have been constrained: the white dwarf mass is at the low end of the range expected for cataclysmic variables. Correlations between the positions of the accretion regions on or near the surface of the white dwarf and the binary system parameters were established. The sizes of the accretion regions and their relative movement from eclipse to eclipse were estimated: they are typically 4-7 deg depending on the mass of the white dwarf. The potential of these observations will only fully be realised when low state data of the same kind are obtained and the contact phases of the eclipse of the white dwarf are measured.

We present results from a three-site photometric and high-resolution spectroscopic campaign on the hottest known extreme helium star V2076 Oph (HD 160641). A core programme of intensive observations covered two weeks and a much lower sampling rate extended over another two months. Despite the fact that the data seem to indicate periodicity near half a day (though the light curves are clearly not formed by a single periodicity), conventional Fourier analysis of the data fails to reveal coherent frequencies. Furthermore, we are unable to recover frequencies which were apparently clear in an earlier campaign on the star. Evidence of monotonic pulsation amplitude changes is seen at the higher frequencies from a wavelet analysis, but more data are needed before this study can be extended to lower frequencies. The application of linear stochastic differential equation (LSDE) methods indicates that the observed light variations could be a result of random variations giving the appearance of intermittent periodicity. High-resolution spectroscopic observations were obtained during the campaign and additional observations were made three years later. Complex line profile variations were observed. It is proposed that the different behaviour of the emission line studied may indicate it is associated with a stellar wind or resident circumstellar material. The frequencies that are extracted from the velocity data do not conform to those identified in the current or previous photometric campaigns.

Thirty-four new timings of maxima of the radially pulsating extreme helium (EHe) star V652 Her (=BD+13° 3224) obtained during 1996-2004 are reported. The quartic ephemeris (for the pulsation period decrease) is extended and the higher-order terms are defined more accurately. We also report 45 new timings of maxima for the closely similar star BX Cir (= LSS 3184) over the same baseline and present the first evidence that this star also shows a decreasing period. The data obtained thus far can be represented by a quadratic ephemeris - a linearly decreasing period in BX Cir - though the decrease rate (dP/dn ∼ 3.7 x 10 -10 d) is much smaller than in V652 Her.

Rand Water's chemical water quality data from 1991 to 2000 were used to assess the water quality of the Waterval River, which contributes about 111 x 106m3 of water to the Vaal River annually. Due to a biological community's ability to reflect water quality changes over time, biomonitoring was undertaken to support chemical water quality monitoring. Aspects of the riverine habitat, invertebrates and fish were investigated to give baseline information on the area. Human activities such as mining, industry, agriculture, rural and urban settlements are currently responsible for the deterioration of the ecological integrity of this river system. Habitat degradation was especially evident in the upper reaches of the Waterval River, as indicated by the South African Scoring System, version 4, Average Score Per Taxon and Biotic Integrity scores. In general, the ratings achieved were lower than those expected for the available habitat, which suggests that human activities have influenced the biotic community. By ...

We present an analysis of our extensive data-set on IRAS 08544-4431. It is the first object we discuss of our newly defined sample of stars, selected for their position in the 'RV Tauri' box in the IRAS [12]-[25], [25]-[60] two-color diagram. Moreover, our selection criteria included an observed excess in the L-band, indicative of a dusty disc. The SED of IRAS 08544-4431 shows a broad IR excess starting already at H. Our optical photometric data reveal some evidence for deep and] shallow minima in the light curve and a pulsation time-scale of around 100 days with a small amplitude (peak-to-peak amplitude in V = 0.17 mag). Our CORALIE radial velocity measurements show that IRAS 08544-4431 is a binary system with a period of 499 +/- 3 days and a mass function of 0.02 M_sun. Moreover, IRAS 08544-4431 is detected in both the CO (2-1) and (1-0) mm-wave emission lines. The triangular shape of the weak CO profile confirms that part of the circumstellar material is not freely expanding but resides probably in a dusty circumbinary disc. Our chemical abundance analysis of a high resolution spectrum of high S/N reveals that a depletion process has modified the photospheric abundances to a moderate extent ([Zn/Fe]=+0.4). All these findings confirm that the F-type IRAS 08544-4431 is another good example of a binary Post-AGB star surrounded by a dusty disc. The H-alpha P-Cygni profile shows ongoing mass-loss with a very high outflow velocity, the origin of which is not understood. The strength and velocity of the H-alpha-absorption are modulated with the orbital motion; the maxima of both quantities (+/- 400 km/s, 5 Angstrom, respectively) occur at superior conjunction., Comment: 14 pages, 13 figures

We have investigated the pulsational characteristics of the λ Bootis type star BD Phe. Detailed asteroseismological investigations have so far only been carried out for four members of this group of stars, with the number of identified frequencies in these stars ranging from four to seven. We present 30 h of UBVRI time-series photometry, together with 14 h of high-dispersion high signal-to-noise ratio spectroscopy of BD Phe. At least seven frequencies were detected. Since these are all present in independent sets of observations, we argue that the frequencies are fairly well determined despite our limited data. We present a very tentative discussion of the possible pulsation modes. Our results may be useful in the context of recently published δ Scuti pulsation models, which take into account the effects of diffusion.

We present 318 high-dispersion echelle spectra and 450 UBVRCIC observations of the pre-main-sequence star V351 Orionis. These data were obtained simultaneously over a two-week period. The star is unusual in that it no longer shows the frequent sharp fadings that occurred prior to 1986. We find features characteristic of Herbig Ae stars: Hα emission, sharp and broad Na ii absorption components and weak He i absorption. The Hα profile is strongly variable with a time-scale of 1 d and normally is an inverse P Cygni profile, but on occasions overt emission disappears altogether. The equivalent widths of the sharp Na ii absorption lines have decreased quite markedly since 1995, indicating a decrease in the column density of gas in the line of sight. We also detect very weak forbidden [O i] emission. There is no evidence for veiling of the star, but a possible 1.0-d or 0.5-d period in the equivalent widths of the lines could indicate the presence of an accretion hotspot. The star is of particular interest because it is pulsating. We detect at least two periods in the light variation and a further period from the radial velocity variations. Attempts at photometric mode identification were not successful, but from the morphology of the line profiles we can identify one mode as non-radial. In addition, we see on some nights several residual absorption subfeatures moving across the line profile from blue to red. These are almost certainly caused by one or more modes of high degree (l≈8).

We present homogeneous and standardized UBV(RI) C photometry for nearly 550 M stars selected from the Hipparcos satellite data base using the following selection criteria: lack of obvious variability (no Hipparcos variability flag); δ 1.7; and V magnitude fainter than about 7.6. Comparisons are made between the current photometry, other ground-based data sets and Hipparcos photometry. We use linear discriminant analysis to determine a luminosity segregation criterion for late-type stars, and principal component analysis to study the statistical structure of the colour indices and to calibrate absolute magnitude in terms of (V - I) for the dwarf stars. Various methods are used to determine the mean absolute magnitude of the giant stars. We find 10 dwarf stars, apparently previously unrecognized (prior to Hipparcos) as being within 25 pc, including five within 20 pc.

We present simultaneous UBVRI photometry and high-dispersion spectroscopy of the 8 Scuti star QQ Tel. At least seven periodicities are detected in the light curve, but there are likely to be many more. The line profile variations suggest that some of the observed frequencies may be due to modes of moderately high degree (l ≥ 4).

A procedure is presented to map from the spatial correlation parameters of a turbulent density field (the radial and binormal correlation lengths and wavenumbers, and the fluctuation amplitude) to correlation parameters that would be measured by a beam emission spectroscopy (BES) diagnostic. The inverse mapping is also derived, which results in resolution criteria for recovering correct correlation parameters, depending on the spatial response of the instrument quantified in terms of point-spread functions (PSFs). Thus, a procedure is presented that allows for a systematic comparison between theoretical predictions and experimental observations. This procedure is illustrated using the Mega-Ampere Spherical Tokamak BES system and the validity of the underlying assumptions is tested on fluctuating density fields generated by direct numerical simulations using the gyrokinetic code GS2. The measurement of the correlation time, by means of the cross-correlation time-delay method, is also investigated and is shown to be sensitive to the fluctuating radial component of velocity, as well as to small variations in the spatial properties of the PSFs.

We report the detection of velocity variations in the pulsating sdB star, PG 1605+072. Oscillations are detected at the same frequencies found from photometry and have amplitudes of up to 14 km/s for H$\beta$. The strongest oscillation found in previous photometric observations is not evident in our spectroscopy or photometry, and may be absent due to beating of closely spaced modes. Phase differences between spectroscopy and B magnitude photometry imply that maximum brightness occurs not long after maximum radius. We have also found evidence of variation in the observed amplitudes of five Balmer lines, with a decrease in amplitude of the strongest mode blueward from H$\beta$. This effect is not expected and a longer time-series will be needed to clarify it.

The quality of corporate governance service in the parastatal (also called public entity) and listed industrial company sectors of the South African economy was assessed. The assessment was done using newly developed service quality assessment instruments. The reliability of the findings on the quality of corporate governance service implied a 99.5% probability that the sample mean did not differ from the population mean by more than 0.2 on a seven-point scale. In both sectors the actual corporate governance service was assessed against two levels of expectation, namely the desired service level and the lowest acceptable service level. The instruments were the same except for a few adaptations to cater for the less stringently legislated listed company sector and to provide for insights gained from the first assessment. Both assessments resulted in the same four dimensions, namely 'directing and monitoring', 'board capacity', 'assurance' and 'responsiveness and reliability'. One fundamental difference was reported, namely that the listed company directors' corporate governance was in total, in all four dimensions and on all criteria assessed as between the lowest acceptable and the desired service levels. The public entity directors' corporate governance service was in total, in all four dimensions and on all criteria assessed as below the desired as well as the lowest acceptable service levels. The standard deviations as reported were such that it has to be concluded that acceptable and unacceptable corporate governance service levels are found in public entities as well as in listed companies. The assessment results are reported below graphically. Three criteria appeared on both assessments' lists often worst-assessed criteria. They were directors 'being always properly prepared for meetings', 'doing their homework thoroughly' and 'displaying impeccable integrity and honesty, for example with their own claims'.

Photometric monitoring during the period 1993--1997 has been carried out in the UBV system for the cool extreme helium stars BD+1°4381 (FQ Aqr) and BD-1°3438 (NO Ser). Periodograms of the data for both stars for each season of observation show the apparent presence of several periods but, if real, none seems to persist for more than one season. Analysis of the full data set for each star reveals no significant periodicities, although models predict that highly non-adiabatic pulsational variations should occur in hydrogen-deficient stars at these temperatures (∼ 10 000 K).

Results are reported from a multi-site photometric campaign on PG 1605+072, a member of the recently discovered class of pulsating hot subdwarfs, or EC 14026 stars. The main part of the campaign covered two weeks and produced ∼ 180 h of photoelectric photometry from the five sites involved. Periodogram analysis shows that the light curve is dominated by five frequencies in the range 1.89--2.74 mHz (periods 529--365 s) with the main frequency at 2.075 76 mHz (481.75 s), though there appear to be more than 50 frequencies identifiable down to a semi-amplitude of 0.0007 (in fractional intensity) in the range 1.74--4.84 mHz (573--206 s). Compared with other pulsating sdB stars, the low gravity (log g= 5.25) and long periods indicate that the star has evolved away from the core helium-burning horizontal branch. A preliminary model of a post-horizontal-branch star with appropriate parameters yields many pulsation periods in the range 300--600 s, but detailed mode identification is not possible at present.

International Ultraviolet Explorer low-resolution and optical moderate-resolution spectra are presented for the high galactic latitude β Cephei type star, PHL 346. Variability is identified in both the ultraviolet flux and the radial velocity with periods and phases consistent with those previously deduced from optical photometry. The similarity of both the flux and the radial velocity amplitude to those previously reported for the β Cephei variable, γ Pegasus, is striking and provides evidence for PHL 346 being a young core hydrogen burning star. A distance estimate for PHL 346 of approximately 7 kpc (corresponding to a z-distance of approximately 6 kpc) is obtained by scaling the distance of γ Pegasus obtained from Hipparcos observations.

We report the discovery of large-amplitude (∼0.25 mag) pulsations in the bright (V=12.8) sdB star, PG 1605+072. The dominant period is 480 s, but more than 20 periods were present on at least three separate occasions. Frequency analysis of the complete data set yields more than 30 periods. A few of these are harmonics or linear combinations of the strongest modes. Excluding the latter, the periods span a range of almost 400 s, which contrasts with the typical range

We report the discovery of rapid oscillations in the sdB star PG 1047+003. The oscillations are multiperiodic, with nine periods in the range 104–162 s. The optical spectrum of PG 1047+003 is consistent with that of a single sdB star. Line profile fitting yields an effective temperature of 35 000±1000 K and log g=5.9±0.1, although optical photometry and IUE spectrophotometry may indicate a cooler effective temperature. These properties demonstrate that PG 1047+003 is an EC 14026 star, a recently discovered class of sdB pulsators. Optical and infrared photometry constrains any cool companion to the sdB star to be a main-sequence star of spectral type M0 or later. With V=13.47 and a relatively rich pulsation spectrum, PG 1047+003 is an attractive target for an intensive photometric campaign to extract more periods from the light curve which, along with a suitable grid of pulsation models, will probe the interior structure of the star.

We present UBV(RI)C photometry for 80 southern red and blue stars for use as additional standards. The data are tied to the Johnson UBV and Cousins (RI)C systems and extend the range of the available stars for colour equation determination, especially in (U−B) for blue stars and (V−R) and (V−I) for red stars. Comparisons with published data are made and particularly good agreement is found with Bessell for the red (Gliese) stars.

We have obtained 87 new differential UBVRI mean light observations of the rapidly oscillating Ap star HD 6532 on 34 nights in 1987 and on 31 nights in 1994. A frequency analysis of these data, together with 43 published observations obtained on 34 nights in 1986, gives a rotation period of Prot = 1.944 973 ± 0.000 011 d, or a rotation frequency of vrot =0.514146 ± 0.000 003 d- 1 =5.950 76 ± 0.000 03 11Hz. The mean light curve shows a clear double wave which is consistent with both magnetic poles being visible over a rotation period. The U and B curves are in antiphase with the V, R and I curves. The null wavelength, therefore, lies between Band V. This improved rotation frequency is needed for future interpretation of the frequency multiplet generated by the rotational modulation of the rapid 6.9-min pulsation in this star.

Photometric data in the UBV(RI)c system have been acquired for 80 solar analog stars for which we have previously derived highly precise atmospheric parameters Teff, log g, and [Fe/H] using high resolution, high signal-to-noise ratio spectra. UBV and (RI)c data for 46 and 76 of these stars, respectively, are published for the first time. Combining our data with those from the literature, colors in the UBV(RI)c system, with ~0.01 mag precision, are now available for 112 solar analogs. Multiple linear regression is used to derive the solar colors from these photometric data and the spectroscopically derived Teff, log g, and [Fe/H] values. To minimize the impact of systematic errors in the model-dependent atmospheric parameters, we use only the data for the ten stars that most closely resemble our Sun, i.e., the solar twins, and derive the following solar colors: (B-V)=0.653+/-0.005, (U-B)=0.166+/-0.022, (V-R)=0.352+/-0.007, and (V-I)=0.702+/-0.010. These colors are consistent, within the 1 sigma errors, with those derived using the entire sample of 112 solar analogs. We also derive the solar colors using the relation between spectral line-depth ratios and observed stellar colors, i.e., with a completely model-independent approach, and without restricting the analysis to solar twins. We find: (B-V)=0.653+/-0.003, (U-B)=0.158+/-0.009, (V-R)=0.356+/-0.003, and (V-I)=0.701+/-0.003, in excellent agreement with the model-dependent analysis., ApJ, in press

S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because of their peculiar chemical composition, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust. In this paper, we present a large sample of 87 intrinsic galactic S-type AGB stars, observed at infrared wavelengths with the Spitzer Space Telescope, and supplemented with ground-based optical data. On the one hand, we derive the stellar parameters from the optical spectroscopy and photometry, using a grid of model atmospheres. On the other, we decompose the infrared spectra to quantify the flux-contributions from the different dust species. Finally, we compare the independently determined stellar parameters and dust properties. For the stars without significant dust emission, we detect a strict relation between the presence of SiS absorption in the Spitzer spectra and the C/O ratio of the stellar atmosphere. These absorption bands can thus be used as an additional diagnostic for the C/O ratio. For stars with significant dust emission, we define three groups, based on the relative contribution of certain dust species to the infrared flux. We find a strong link between group-membership and C/O ratio. We show that these groups can be explained by assuming that the dust-condensation can be cut short before silicates are produced, while the remaining free atoms and molecules can then form the observed magnesium sulfides or the carriers of the unidentified 13 and 20 micron features. Finally, we present the detection of emission features attributed to molecules and dust characteristic to C-type stars, such as molecular SiS, hydrocarbons and magnesium sulfide grains. We show that we often detect magnesium sulfides together with molecular SiS and we propose that it is formed by a reaction of SiS molecules with Mg., Comment: Accepted for publication in A&A

We have photometrically monitored nine intermediate- to high-Galactic-latitude B-type stars for β Cephei-type variability. One star, HD 204076, shows a clearly sinusoidal variation with an amplitude of ∼0.015 mag and a period of a few hours, typical of β Cephei stars. One other (HD 206144) is possibly a longer term variable at the 2 per cent level, while two objects, HD 219188 and HD 118246, may be variable at a smaller amplitude of

We obtained K-band spectro-interferometric observations of the Miras R Cnc, X Hya, W Vel, and RW Vel with a spectral resolution of 1500 using the VLTI/AMBER instrument. We obtained concurrent JHKL photometry using the the Mk II instrument at the SAAO. Our sources have wavelength-dependent visibility values that are consistent with earlier low-resolution AMBER observations of S Ori and with the predictions of dynamic model atmosphere series based on self-excited pulsation models. The wavelength-dependent UD diameters show a minimum near the near-continuum bandpass at 2.25 um. They increase by up to 30% toward the H2O band at 2.0 um and by up to 70% at the CO bandheads. The dynamic model atmosphere series show a consistent wavelength-dependence, and their parameters such as the visual phase, effective temperature, and distances are consistent with independent estimates. The closure phases have significantly wavelength-dependent non-zero values indicating deviations from point symmetry. For example, the R Cnc closure phase is 110 degr in the 2.0 um H2O band, corresponding for instance to an additional unresolved spot contributing 3% of the total flux at a separation of ~4 mas. Our observations are consistent with the predictions of the latest dynamic model atmosphere series based on self-excited pulsation models. The wavelength-dependent radius variations are interpreted as the effect of molecular layers. The wavelength-dependent closure phase values are indicative of deviations from point symmetry at all wavelengths, thus a complex non-spherical stratification of the extended atmosphere. In particular, the significant deviation from point symmetry in the H2O band is interpreted as a signature on large scales of inhomogeneities or clumps in the water vapor layer. The observed inhomogeneities might be caused by pulsation- and shock-induced chaotic motion in the extended atmosphere., 5 pages, 2 figures, accepted for publication as a Letter in Astronomy and Astrophysics