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We present the variability processing and analysis that is foreseen for the Gaia mission within Coordination Unit 7 (CU7) of the Gaia Data Processing and Analysis Consortium (DPAC). A top level description of the tasks is given. [ABSTRACT FROM AUTHOR]

We present relative astrometry and differential photometry measurements for a sample of nearby southern orbital binaries making use of the technique of Adaptive Optics. The observations were made in December 2000, with the ADONIS camera mounted at the 3.6-m ESO telescope from La Silla Observatory, equipped with the broad-band near-infrared filters ( J -, H -, K -passbands). Our sample contains stars which do not fit very well the empirical mean mass-luminosity relation (according to our previous study), but for which accurate parallaxes (determined by the Hipparcos satellite) and high-quality orbits were available thanks to many previous efforts. We derived accurate positions and J, H, K magnitudes of the individual components of those binaries. The individual stellar components have near-infrared colour indices well grouped in those plots and are comparable to standard single stars. The data reduction procedure used for deriving those results is described in detail. It is based on a least-squares fit of Moffat-Lorentz profiles in direct imaging for well-resolved systems and on Fourier analysis for very close pairs. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

ABSTRACT We present an automated classification of stars exhibiting periodic, non-periodic and irregular light variations. The Hipparcos catalogue of unsolved variables is employed to complement the training set of periodic variables of Dubath et al. with irregular and non-periodic representatives, leading to 3881 sources in total which describe 24 variability types. The attributes employed to characterize light-curve features are selected according to their relevance for classification. Classifier models are produced with random forests and a multistage methodology based on Bayesian networks, achieving overall misclassification rates under 12 per cent. Both classifiers are applied to predict variability types for 6051 Hipparcos variables associated with uncertain or missing types in the literature. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a study on the determination of rotation periods ( P) of solar-like stars from the photometric irregular time sampling of the European Space Agency Gaia mission, currently scheduled for launch in 2013, taking into account its dependence on ecliptic coordinates. We examine the case of solar twins as well as thousands of synthetic time series of solar-like stars rotating faster than the Sun. In the case of solar twins, we assume that the Gaia unfiltered photometric passband G will mimic the variability of the total solar irradiance as measured by the Variability of solar IRradiance and Gravity Oscillations (VIRGO) experiment. For stars rotating faster than the Sun, light curves are simulated using synthetic spectra for the quiet atmosphere, the spots and the faculae combined by applying semi-empirical relationships relating the level of photospheric magnetic activity to the stellar rotation and the Gaia instrumental response. The capabilities of the Deeming, Lomb-Scargle and phase dispersion minimization methods in recovering the correct rotation periods are tested and compared. The false alarm probability is computed using Monte Carlo simulations and compared with analytical formulae. The Gaia scanning law makes the rate of correct detection of rotation periods strongly dependent on the ecliptic latitude (β). We find that for P≃ 1 d, the rate of correct detection increases with β from 20-30 per cent at β≃ 0 to a peak of 70 per cent at β= 45°; then it abruptly falls below 10 per cent at β > 45°. For P > 5 d, the rate of correct detection is quite low and for solar twins is only 5 per cent on average. [ABSTRACT FROM AUTHOR]

We present an evaluation of the performance of an automated classification of the Hipparcos periodic variable stars into 26 types. The sub-sample with the most reliable variability types available in the literature is used to train supervised algorithms to characterize the type dependencies on a number of attributes. The most useful attributes evaluated with the random forest methodology include, in decreasing order of importance, the period, the amplitude, the V− I colour index, the absolute magnitude, the residual around the folded light-curve model, the magnitude distribution skewness and the amplitude of the second harmonic of the Fourier series model relative to that of the fundamental frequency. Random forests and a multi-stage scheme involving Bayesian network and Gaussian mixture methods lead to statistically equivalent results. In standard 10-fold cross-validation (CV) experiments, the rate of correct classification is between 90 and 100 per cent, depending on the variability type. The main mis-classification cases, up to a rate of about 10 per cent, arise due to confusion between SPB and ACV blue variables and between eclipsing binaries, ellipsoidal variables and other variability types. Our training set and the predicted types for the other Hipparcos periodic stars are available online. [ABSTRACT FROM AUTHOR]

The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies, characteristic of slowly pulsating B (SPB) stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/β Cephei (β Cep) hybrids. In all cases, the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the β Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence for pulsating stars between the cool edge of the SPB and the hot edge of the δ Sct instability strips. None of the stars shows the broad features which can be attributed to stochastically excited modes as recently proposed. Among our sample of B stars are two chemically peculiar stars, one of which is a HgMn star showing rotational modulation in the light curve. [ABSTRACT FROM AUTHOR]

DG Leo is a spectroscopic triple system showing $\delta$ Scuti type photometric and spectroscopic variations. The three components have nearly equal masses but different chemical compositions in the outer layers. All three are potential pulsators. Frequency analyses of the photometric data were carried out using various methods. These global results together with those of the spectroscopic analysis permit us to discuss of the behaviour of each component with respect to pulsation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html [ABSTRACT FROM PUBLISHER]

A group of 36 normal control persons was patch-tested with glass fibers. The tested filaments had a length of about 3 to 5 mm and a diameter of 9 to 13 µm. The glass fibers were obtained from the normal production process. They were coated with cured epoxy resin. A group of 29 normal control persons was tested with the same type of fibers from which the epoxy finish had been burned off. Another group of 36 persons was patch-tested with ultrasmall glass globes with a diameter of 10 to 15 µm. Coated and uncoated glass globules were tested. On every person 5 patch tests with the same material were done. They were removed after 1, 5, 24, 48 and 72 h. On coated fiber, 12 of 36 tested people reacted with either a + or a ++ reaction. On the uncoated fibers a reaction could be noted in 10 out of 29 persons. The patch tests with coated as well as uncoated glass globules were all negative. A total of 60 biopsies was performed In those cases where + or ++ reactions were noted. The histological examination of the biopsies showed no differences between the reactions on coated and uncoated fibers. The skin reactions to glass fiber showed, besides microtraumatic changes, several histological characteristics of an eczematous reaction, like spongiosis and perivascular lymphocytic infiltration. The importance of these findings is discussed. It is emphasized that histological alterations are only one of the six points which must be taken into account when the diagnosis of eczema is considered. [ABSTRACT FROM AUTHOR]

The absolute electrophoretic mobility of red blood cells was examined before and after the addition of linoleic acid. The determinations were performed with a Zeiss cytopherometer. The blood was taken from 22 patients with multiple sclerosis in different phases of their disease. A group of 17 patients with other neurological diseases and three apparently healthy subjects served as controls. Our results show that the mobility of red blood cells was either accelerated or inhibited in the presence of linoleic acid, both in the multiple sclerosis patients as well as in the control group. The increase or inhibition of the absolute mobility was small and randomly distributed. The value of this so-called E-UFA test (erythrocyte-unsaturated fatty acid) as a specific diagnostic test for multiple sclerosis is not confirmed by our results. [ABSTRACT FROM AUTHOR]

In five baboons and 11 cats cerebral ischaemia was produced either by inflating an epidural balloon and or by ligating major arteries supplying the brain. Fifteen of the animals developed intracranial hypertension after cerebral ischaemia. If ICP were high, but still significantly lower than MABP, elevation of MABP by noradrenaline infusions was accompanied by a proportional increase of ICP. However, the increase of ICP was lower than that of MABP so that CPP was raised. CBF measured by the 133Xenon clearance technique was significantly increased by arterial hypertension in eight cases. The proportional increase of CPP and CBF by elevation of arterial blood pressure was substantially greater, the lower ICP was immediately after ischaemia. There was no effect of MABP in cases in which ICP equalled MABP. [ABSTRACT FROM AUTHOR]

We started a systematic search for periodic variable-star candidates in the EROS-2 database in the context of preparatory work for the Gaia satellite mission. The goal is to evaluate different classification tools and strategies, and to identify a large sample of variable candidates. In this paper we present the results of an assessment study of a three-step identification and classification process. In the study we took a sample of about 80,000 stars from one of the LMC EROS fields. [ABSTRACT FROM PUBLISHER]

In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.