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The most recent release of the General Catalogue of Variable Stars (GCVS) (Samus et al. 2017) contains 518 different variable types, in eight different variable categories. The catalogue has now reached its 5th version available via the VizieR service and can be considered one of the primary catalogues on the subject. The Gaia Data Release 3 (DR3) contains the most extensive catalogue of variable stars over the entire sky, still it is an intermediate step towards a better understanding of the quality of data and the automated algorithms being put in place to achieve a more concise classification as the work progresses. Ongoing work to identify all variability types in Gaia requires that a complete set of variable classes is represented. We investigated the most recent variability types listed therein, and compared them to the literature used to classify variable stars in Gaia. We have come across close to 10 000 individual variables in the GCVS that are not classified as variable in Gaia DR3, which include 56 variability types – some of which are bright stars. In this investigation, we demonstrate that there are still a large number of those bright stars missing from the Gaia variable classification. Clear indications show that variables with very short (<1 d), and very long periods, were missed by Gaia DR3 Gaia (Prusti et al. 2016 and Vallenari et al. 2022). Moreover, variables with large amplitudes were also missing. We discuss our findings in some detail. [ABSTRACT FROM AUTHOR]

Context. The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ≲ 21 mag. Aims. We showcase stellar variability in the Galactic colour-absolute magnitude diagram (CaMD). We focus on pulsating, eruptive, and cataclysmic variables, as well as on stars that exhibit variability that is due to rotation and eclipses. Methods. We describe the locations of variable star classes, variable object fractions, and typical variability amplitudes throughout the CaMD and show how variability-related changes in colour and brightness induce "motions". To do this, we use 22 months of calibrated photometric, spectro-photometric, and astrometric Gaia data of stars with a significant parallax. To ensure that a large variety of variable star classes populate the CaMD, we crossmatched Gaia sources with known variable stars. We also used the statistics and variability detection modules of the Gaia variability pipeline. Corrections for interstellar extinction are not implemented in this article. Results. Gaia enables the first investigation of Galactic variable star populations in the CaMD on a similar, if not larger, scale as was previously done in the Magellanic Clouds. Although the observed colours are not corrected for reddening, distinct regions are visible in which variable stars occur. We determine variable star fractions to within the current detection thresholds of Gaia. Finally, we report the most complete description of variability-induced motion within the CaMD to date. Conclusions. Gaia enables novel insights into variability phenomena for an unprecedented number of stars, which will benefit the understanding of stellar astrophysics. The CaMD of Galactic variable stars provides crucial information on physical origins of variability in a way that has previously only been accessible for Galactic star clusters or external galaxies. Future Gaia data releases will enable significant improvements over this preview by providing longer time series, more accurate astrometry, and additional data types (time series BP and RP spectra, RVS spectra, and radial velocities), all for much larger samples of stars. [ABSTRACT FROM AUTHOR]

Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS).Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS.Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σϖ/ϖ< 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σϖ/ϖ< 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σϖ/ϖ< 0.5). The new relations were computed using multi-band (V,I,J,Ks) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and MV- [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods.Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the Hipparcos measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive.Conclusions. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. [ABSTRACT FROM AUTHOR]

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]

Alkylresorcinols (ARs) are amphiphilic phenolic lipids and their two main metabolites, 3-(3,5-dihydroxyphenyl)-propanoic acid (DHPPA) and 3,5-dihydroxybenzoic acid (DHBA), can be used as biomarkers of whole grain wheat and rye intake. The aim of this study was to develop antibodies against DHBA and DHPPA for use in ELISA analysis. Good calibration curves were obtained for ELISA using alkaline phosphatase (AP) conjugates. The highest sensitivity for DHPPA was found using a reagent combination of anti-DHPPA–BSA and DHPAA–AP in a direct ELISA (IC 50 = 1.5 μmol/L), and for DHBA using a reagent combination of anti-DHBA–OV and DHBA–AP (IC 50 = 1.3 μmol/L). Calibration was conducted in the linear range (0.3–27.4 μmol/L), with limit of detection (LOD) 0.1 μmol/L. Intra and inter CVs was in the range of 0.7–7.2% and 5.1–11.5%, respectively, for DHPPA and 1.3–9.4% and 3.5–20%, respectively, for DHBA. Mean recovery was 104% for DHPPA and 102% for DHBA. The ELISA method developed was then used for analysis of 120 urine samples from free-living men and women that had previously been analysed by gas chromatography–mass spectrometry (GC–MS). ELISA produced several-fold higher values than GC–MS. Application of high-resolution Orbitrap mass spectrometry (HR Orbitrap MS) allowed several compounds, including novel putative AR metabolites, to be identified, synthesised and confirmed as compounds with high ELISA cross-reactivity. [ABSTRACT FROM AUTHOR]

Influenza is a serious infectious disease, which is life-threatening especially in children, seniors and immunocompromised patients. In addition to vaccination, the development of new anti-influenza agents represents a crucial defence strategy to combat seasonal and pandemic influenza strains. At present most attention is paid to the development of inhibitors of influenza neuraminidase, which has been established as a key drug target for the prophylaxis and treatment of influenza infections. However, the emergence of drug-resistant influenza variants highlights the need of continuously innovative strategies for the development of new drugs with improved antiviral effects, higher safety and increased tolerability. In this review article, an analysis of publications describing anti-influenza agents indexed in the Web of Science® database has been carried out. The most important publications are presented in tables and are characterised by several key words, abstracts and references. The presented publications have been sorted according to five basic criteria: (i) review articles, (ii) design, synthesis and evaluation of new anti-influenza drugs, (iii) major classes of anti-influenza drugs, (iv) combination therapy of influenza infections and (v) influenza drug resistance. The design of this review article allows us to offer a complex overview of known antiviral agents targeting influenza viruses, facilitates easy and rapid orientation in numerous publications written on this subject, and aids the gathering of required data. [ABSTRACT FROM AUTHOR]

Influenza is a serious infectious disease, which is life-threatening especially in children, seniors and immunocompromised patients. In addition to vaccination, the development of new anti-influenza agents represents a crucial defence strategy to combat seasonal and pandemic influenza strains. At present most attention is paid to the development of inhibitors of influenza neuraminidase, which has been established as a key drug target for the prophylaxis and treatment of influenza infections. However, the emergence of drug-resistant influenza variants highlights the need of continuously innovative strategies for the development of new drugs with improved antiviral effects, higher safety and increased tolerability. In this review article, an analysis of publications describing anti-influenza agents indexed in the Web of Science® database has been carried out. The most important publications are presented in tables and are characterised by several key words, abstracts and references. The presented publications have been sorted according to five basic criteria: (i) review articles, (ii) design, synthesis and evaluation of new anti-influenza drugs, (iii) major classes of anti-influenza drugs, (iv) combination therapy of influenza infections and (v) influenza drug resistance. The design of this review article allows us to offer a complex overview of known antiviral agents targeting influenza viruses, facilitates easy and rapid orientation in numerous publications written on this subject, and aids the gathering of required data. [ABSTRACT FROM AUTHOR]

Single-domain antibody (sdAb) fragments derived from heavy-chain antibodies of camelids and cartilaginous fish represent a new generation of therapeutic agents and immunoreagents. Due to their unique characteristics, such as low molecular weight, high physical-chemical stability, good water solubility, and the ability to bind antigens inaccessible to conventional antibodies, they could potentially act as a substitute for conventional therapeutic drugs in the treatment of serious human diseases, and, moreover, could be broadly used in analyses and diagnostics. In this review article, an analysis of 826 publications oriented to heavy-chain antibodies and their sdAb fragments indexed in the Web of Science® database since 1993 has been carried out. Attention has predominantly been paid to papers published from 2010 to June 2012. Key publications are presented in tables and are characterised by descriptive words, abstracts and references. he presented publications have been sorted according to seven basic criteria: review articles and monographs, heavy-chain antibodies of camelids and sharks, production of sdAb fragments using recombinant technology, characteristic properties of sdAb fragments, application of sdAb fragments in therapy, application of sdAb fragments in diagnostic and immunoanalytical methods and other prospective uses of sdAb fragments. his review article should highlight the typical properties of heavy-chain antibodies and sdAb fragments which differentiate them from conventional antibodies and other available recombinant fragments, and also emphasize their extremely broad application potential, mainly in human disease therapy. At the same time it allows an easy and rapid orientation in numerous publications written on this subject, and facilitates the search for the required data. [ABSTRACT FROM AUTHOR]

Our goal is to assess Gaia's performance on the period recovery of short period (p< 2 hours) and small amplitude variability. To reach this goal first we collected the properties of variable stars that fit the requirements described above. Then we built a database of synthetic light-curves with short period and low amplitude variability with time sampling that follows the Gaia nominal scanning law and with noise level corresponding to the expected photometric precision of Gaia. Finally we performed period search on the synthetic light-curves to obtain period recovery statistics. This work extends our previous period recovery studies to short period variable stars which have nonstationary Fourier spectra. [ABSTRACT FROM AUTHOR]

The ESA Gaia mission will provide a multi-epoch database for a billion of objects, including variable objects that comprise stars, active galactic nuclei and asteroids. We highlight a few of Gaia's properties that will benefit the study of variable objects, and illustrate with two examples the work being done in the preparation of the data processing and object characterization. The first example relates to the analysis of the nearly simultaneous multi-band data of Gaia with the Principal Component Analysis techniques, and the second example concerns the classification of Gaia time series into variability types. The results of the ground-based processing of Gaia's variable objects data will be made available to the scientific community through the intermediate and final ESA releases throughout the mission. [ABSTRACT FROM AUTHOR]

The Gaia satellite was selected as a cornerstone mission of the European Space Agency (ESA) in 2000 October and confirmed in 2002 with a current target launch date of 2011. The Gaia mission will gather on the same observational principles as Hipparcos detailed astrometric, photometric and spectroscopic properties of about one billion sources brighter than . The nature of the measured objects ranges from near-Earth objects (NEOs) to gamma-ray burst afterglows, and encompasses virtually any kind of stars in our Galaxy. Gaia will provide multicolour (in about 20 passbands extending over the visible range) photometry with typically 250 observations distributed over 40 well-separated epochs during the 5-yr mission. The multi-epoch nature of the project will permit the detection and analysis of variable sources whose number is currently estimated in the range of several tens of millions, among the detectable sources. In this paper, we assess the performances of Gaia in analysing photometric periodic phenomena. We first quickly present the overall observational principle before discussing the implication of the scanning law in the time-sampling. Then from extensive simulations one assesses the performances in the recovery of periodic signals as a function of the period, signal-to-noise ratio and position on the sky for simple sinusoidal variability. [ABSTRACT FROM AUTHOR]

With the advent of surveys generating multi-epoch photometry and the discovery of large numbers of variable stars, the classification of these stars has to be automatic. We have developed such a classification procedure for about 1700 stars from the variable star catalogue of the All-Sky Automated Survey 1–2 (ASAS 1–2) by selecting the periodic stars and by applying an unsupervised Bayesian classifier using parameters obtained through a Fourier decomposition of the light curve. For irregular light curves we used the period and moments of the magnitude distribution for the classification. In the case of ASAS 1–2, 83 per cent of variable objects are red giants. A general relation between the period and amplitude is found for a large fraction of those stars. The selection led to 302 periodic and 1429 semiperiodic stars, which are classified in six major groups: eclipsing binaries,‘sinusoidal curves’, Cepheids, small amplitude red variables, SR and Mira stars. The type classification error level is estimated to be about 7 per cent. [ABSTRACT FROM AUTHOR]

Among over 200 000 Galactic bulge variable stars in the public domain Optical Gravitational Lensing Experiment (OGLE) catalogue, we found over 15 000 red giant variables following two well-defined period–amplitude relations. The periods are in the range , and amplitudes in the range in the I band. The variables cover a broad range of reddening-corrected colours, , and a fairly narrow range of extinction-corrected apparent magnitudes, . A subset of variables (type A) has an rms scatter of only 0.44 mag. The average magnitudes for these stars are well correlated with the Galactic longitude, and vary from for to for , clearly indicating that they are located in the Galactic bar. Most variables have several oscillation periods. [ABSTRACT FROM AUTHOR]

ABSTRACT We report a measurement of the streaming motion of the stars in the Galactic bar with the red clump giants (RCGs) using the data of the Optical Gravitational Lensing Experiment II (OGLE-II). We measure the proper motion of 46 961 stars and divide RCGs into bright and faint subsamples that on average will be closer to the near and far sides of the bar, respectively. We find that the far-side RCGs (4979 stars) have a proper motion of Δ<μ>∼ 1.5 ± 0.11 mas yr[sup -1] toward the negative l relative to the near-side RCGs (3610 stars). This result can be explained by stars in the bar rotating around the Galactic Centre in the same direction as the Sun with v[sub b]∼ 100 km s[sup -1] . In the disc star (DS) and red giant (RG) samples, we do not find significant difference between bright and faint subsamples. For those samples Δ<μ>∼ 0.3 ± 0.14 mas yr[sup -1] and ∼0.03 ± 0.14 mas yr[sup -1] , respectively. It is likely that the average proper motion of RG stars is the same as that of the Galactic Centre. The proper motion of DSs with respect to RGs is ∼3.3 mas yr[sup -1] toward positive l. This value is consistent with the expectations for a flat rotation curve and solar motion with respect to local standard of rest. RGs have proper motion approximately equal to the average of bright and faint RCGs, which implies that they are on average near the centre of the bar. This pilot project demonstrates that OGLE-II data may be used to study streaming motions of stars in the Galactic bar. We intend to extend this work to all 49 OGLE-II fields in the Galactic bulge region. [ABSTRACT FROM AUTHOR]

The difference image analysis (DIA) of the images obtained by the Optical Gravitational Lensing Experiment (OGLE-II) revealed a peculiar artefact in the sample of stars proposed as variable by Wozniak in one of the Galactic bulge fields: the occurrence of pairs of candidate variables showing anti-correlated light curves monotonic over a period of 3 yr. This effect can be understood, quantified and related to the stellar proper motions. DIA photometry supplemented with a simple model offers an effective and easy way to detect high proper motion stars in very dense stellar fields, where conventional astrometric searches are extremely inefficient. [ABSTRACT FROM AUTHOR]

Context. The Gaia Collaboration has recently reported the detection of a 33 M⊙ black hole in a wide binary system located in the solar neighbourhood. Aims. Here we explore the relationship between this black hole, known as Gaia BH3, and the nearby ED-2 halo stellar stream. Methods. We studied the orbital characteristics of the Gaia BH3 binary and present measurements of the chemical abundances of ED-2 member stars derived from high-resolution spectra obtained with the VLT. Results. We find that the Galactic orbit of the Gaia BH3 system and its metallicity are entirely consistent with being part of the ED-2 stream. The characteristics of the stream, particularly its negligible spread in metallicity and in other chemical elements, as well as its single stellar population, suggest that it originated from a disrupted star cluster of low mass. Its age is comparable to that of the globular cluster M92 that has been estimated to be as old as the Universe. Conclusions. This is the first black hole unambiguously associated with a disrupted star cluster. We infer the plausible mass range for the cluster to be relatively narrow, between 2 × 103 M⊙ and 5.2 × 104 M⊙. This implies that the black hole could have formed directly from the collapse of a massive very metal-poor star, but that the alternative scenario of binary interactions inside the cluster environment also deserves to be explored. [ABSTRACT FROM AUTHOR]

We present 97 QSO candidates in 48 Galactic bulge fields of the Optical Gravitational Lensing Experiment II (OGLE-II) covering∼11 deg2, which are selected via their variability. We extend light curves of variable objects which were detected in a 3-yr baseline in the OGLE-II variable star catalogue to fourth year. We search for objects that are faintand slowly variable over 4 yr in this catalogue by using the variogram/structure function. Finding the QSOs in such stellar-crowded and high extinction fields is challenging, but should be useful for the astrometric reference frame. Spectroscopic follow-up observations are required to confirm these QSO candidates. Follow-up observations are being prepared for four of these fields (BUL_SC1, 2, 32 and 45). Follow-up observations for other fields are strongly encouraged. The complete list and light curves of all 97 candidates are available in electronic format at. [ABSTRACT FROM AUTHOR]

The ESA space mission Gaia, planned to be launched at the end of 2013, will make astrometric, photometric and spectroscopic measurements of about 1 billion sources in our Galaxy. Amongst these sources will be numerous multiple systems. In the processing chain eclipsing binaries (EBs) will be detected and, if possible, their period and characteristics determined. Here we summarize the various steps that are foreseen to automatically classify and characterise these EBs. [ABSTRACT FROM AUTHOR]

Context. In the new era of large-scale astronomical surveys, automated methods of analysis and classification of bulk data are a fundamental tool for fast and effcient production of deliverables. This becomes ever more important as we enter the Gaia era. Aims. We investigate the potential detectability of eclipsing binaries with Gaia using a data set of all Kepler eclipsing binaries sampled with Gaia cadence and folded with the Kepler period. The performance of fitting methods is evaluated in comparison to real Kepler data parameters and a classification scheme is proposed for the potentially detectable sources based on the geometry of the light curve fits. Methods. The polynomial chain (polyfit) and two-Gaussian models are used for light curve fitting of the data set. Classification is performed with a combination of the t-distributed stochastic neighbor embedding (t-SNE) and density-based spatial clustering of applications with noise (DBSCAN) algorithms. Results. We find that ~68% of the Kepler Eclipsing Binary Catalog sources are potentially detectable by Gaia when folded with the Kepler period; we propose a classification scheme of the detectable sources based on the morphological type indicative of the light curve with subclasses that reflect the properties of the fitted model (presence and visibility of eclipses, their width, depth, etc.). [ABSTRACT FROM AUTHOR]

Context: The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims: We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods: Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results: Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions: The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs. [ABSTRACT FROM AUTHOR]

Context. Pulsating stars are windows to the physics of stars enabling us to see glimpses of their interior. Not all stars pulsate, however. On the main sequence, pulsating stars form an almost continuous sequence in brightness, except for a magnitude range between δ Scuti and slowly pulsating B stars. Against all expectations, 36 periodic variables were discovered in 2013 in this luminosity range in the open cluster NGC 3766, the origins of which was a mystery. Aims. We investigate the properties of those new variability class candidates in relation to their stellar rotation rates and stellar multiplicity. Methods. We took multi-epoch spectra over three consecutive nights using ESO's Very Large Telescope. Results. We find that the majority of the new variability class candidates are fast-rotating pulsators that obey a new period-luminosity relation. We argue that the new relation discovered here has a different physical origin to the period-luminosity relations observed for Cepheids. Conclusions. We anticipate that our discovery will boost the relatively new field of stellar pulsation in fast-rotating stars, will open new doors for asteroseismology, and will potentially offer a new tool to estimate stellar ages or cosmic distances. [ABSTRACT FROM AUTHOR]

Baade-Wesselink-type (BW) techniques enable geometric distance measurements of Cepheid variable stars in the Galaxy and the Magellanic clouds. The leading uncertainties involved concern projection factors required to translate observed radial velocities (RVs) to pulsational velocities and recently discovered modulated variability. We carried out an unprecedented observational campaign involving long-baseline interferometry (VLTI/PIONIER) and spectroscopy (Euler/Coralie) to search for modulated variability in the long-period (P ∼ 35.5 d) Cepheid l Carinae. We determine highly precise angular diameters from squared visibilities and investigate possible differences between two consecutive maximal diameters, ΔmaxΘ. We characterize the modulated variability along the line of sight using 360 high-precision RVs. Here we report tentative evidence for modulated angular variability and confirm cycle-to-cycle differences of l Carinae's RV variability. Two successive maxima yield ΔmaxΘ = 13.1 ± 0.7(stat.) μas for uniform disc models and 22.5 ± 1.4(stat.) μas (4 per cent of the total angular variation) for limb-darkened models. By comparing new RVs with 2014 RVs, we show modulation to vary in strength. Barring confirmation, our results suggest the optical continuum (traced by interferometry) to be differently affected by modulation than gas motions (traced by spectroscopy). This implies a previously unknown time dependence of projection factors, which can vary by 5 per cent between consecutive cycles of expansion and contraction. Additional interferometric data are required to confirm modulated angular diameter variations. By understanding the origin of modulated variability and monitoring its long-term behaviour, we aim to improve the accuracy of BW distances and further the understanding of stellar pulsations. [ABSTRACT FROM AUTHOR]

The Kepler space mission provided near-continuous and high-precision photometry of about 207 000 stars, which can be used for asteroseismology. However, for successful seismic modeling it is equally important to have accurate stellar physical parameters. Therefore, supplementary ground-based data are needed. We report the results of the analysis of high-resolution spectroscopic data of A- and F-type stars from the Kepler field, which were obtained with the HERMES spectrograph on the Mercator telescope. We determined spectral types, atmospheric parameters and chemical abundances for a sample of 117 stars. Hydrogen Balmer, Fe i, and Fe ii lines were used to derive effective temperatures, surface gravities, and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. The atmospheric parameters obtained were compared with those from the Kepler Input Catalogue (KIC), confirming that the KIC effective temperatures are underestimated for A stars. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The analysed sample comprises stars with approximately solar chemical abundances, as well as chemically peculiar stars of the Am, Ap, and À Boo types. The distribution of the projected rotational velocity, usin i, is typical for A and F stars and ranges from 8 to about 280 km s-1, with a mean of 134 km s-1. [ABSTRACT FROM AUTHOR]

We demonstrate the eclipsing binary detection performance of the Gaia variability analysis and processing pipeline using Hipparcos data. The automated pipeline classifies 1067 (0.9%) of the 118 204 Hipparcos sources as eclipsing binary candidates. The detection rate amounts to 89% (732 sources) in a subset of 819 visually confirmed eclipsing binaries, with the period correctly identified for 80% of them, and double or half periods obtained in 6% of the cases. [ABSTRACT FROM AUTHOR]

This paper gives a brief overview of the Gaia Research for European Astronomy Training (GREAT) network, including a description of the GREAT-ESF Research Network Programme and the GREAT Initial Training Network (GREAT-ITN). Scientific highlights from the GREAT-ITN are noted. [ABSTRACT FROM AUTHOR]

Aims. Three-dimensional (3D) maps of the Galactic interstellar matter (ISM) are a potential tool of wide use, but accurate and detailed maps are still lacking. One of the ways to construct the maps is to invert individual distance-limited ISM measurements, a method we have applied here to measurements of stellar color excess in the optical. Methods. We assembled color excess data together with the associated parallax or photometric distances to constitute a catalog of ≃23 000 sightlines for stars within 2.5 kpc. The photometric data are taken from Strömgren catalogs, the Geneva photometric database, and the Geneva-Copenhagen survey. We also included extinctions derived towards open clusters. We applied an inversion method based on a regularized Bayesian approach to this color excess dataset, a method previously used for mapping at closer distances. Results. We show the dust spatial distribution resulting from the inversion by means of planar cuts through the differential opacity 3D distribution, and by means of 2D maps of the integrated opacity from the Sun up to various distances. The mapping assigns locations to the nearby dense clouds and represents their distribution at the spatial resolution that is allowed by the dataset properties, i.e. '10 pc close to the Sun and increasing to '100 pc beyond 1 kpc. Biases toward nearby and/or weakly extincted stars make this dataset particularly appropriate to mapping the local and neighboring cavities and to locating faint, extended nearby clouds, which are both goals that are difficult or impossible with other mapping methods. The new maps reveal a '1 kpc wide empty region in the third quadrant in the continuation of the so-called CMa tunnel of the Local Cavity, a cavity that we identify as the Superbubble GSH238+00+09 detected in radio emission maps and that is found to be bounded by the Orion and Vela clouds. The maps also show an extended narrower tunnel in the opposite direction (l '≃70°) that also extends the Local Bubble further and together with it forms a conspicuous cavity bounded by the main Lup, Sco, Oph, Aql, Lac, Cep, and Tau clouds and OB associations. This chain of cavities and surrounding dense regions constitute the first computed representation of the well known Gould belt/Lindblad ring structures. Finally, almost all off-plane faint features that appear in 2D dust maps have a counterpart in the 3D maps, providing the dust distribution in nearby tenuous clouds. [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 propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the time-series of the first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude δ Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae stars. [ABSTRACT FROM AUTHOR]

Aims. Diffuse interstellar bands (DIBs) measured in stellar spectra contain information on the amount of interstellar (IS) matter that is distributed along the line-of-sight, and similarly to other absorbing species may be used to locate IS clouds. Here we present a new database of 5780.5 and 6283.8 Å DIB measurements. Those two DIBs have the advantage that they are strong and also broad enough to be detectable in cool-star spectra. We also study their correlation with the reddening. Methods. The database is based on high-resolution, high-quality spectra of early-type nearby stars located in the southern hemisphere at an average distance of 300 pc. Equivalent widths of the two DIBs were determined by means of a realistic continuum fitting and synthetic atmospheric transmissions. For all stars that possess a precise measurement of their color excess, we compare the DIBs and the extinction. Results. We find average linear relationships of the DIBS and the color excess based on ≃120 and 130 objects that agree well with those of a previous survey of ≃130 northern hemisphere stars closer than 550 pc. Because our target sky coverage is complementary, this similarity shows that there is no significant spatial dependence of the average relationship in the solar neighborhood within ≃600 pc. A noticeably different result is our higher degree of correlation of the two DIBs with the extinction, especially for the 5780 Å DIB. We demonstrate that it is simply due to the lower temperature and intrinsic luminosity of our targets. Using cooler target stars reduces the number of outliers, especially for nearby stars, confirming that the radiation field of UV bright stars has a significant influence on the DIB strength. We illustrate the potential use of 3D maps of the ISM for characterizing the DIB sites. There is some evidence that interstellar cavity boundaries are DIB-deficient, although definite conclusions will have to wait for maps with a higher resolution. Finally, we have used the cleanest data to compute updated DIB shapes. [ABSTRACT FROM AUTHOR]

Aims. We present dense grids of stellar models suitable for comparison with observable quantities measured with great precision, such as those derived from binary systems or planet-hosting stars. Methods. We computed new Geneva models without rotation at metallicities Z = 0.006, 0.01, 0.014, 0.02, 0.03, and 0.04 (i.e. [Fe/H] from -0.33 to +0.54) and with mass in small steps from 0.5 to 3.5 M☉. Great care was taken in the procedure for interpolating between tracks in order to compute isochrones. Results. Several properties of our grids are presented as a function of stellar mass and metallicity. Those include surface properties in the Hertzsprung-Russell diagram, internal properties including mean stellar density, sizes of the convective cores, and global asteroseismic properties. Conclusions. We checked our interpolation procedure and compared interpolated tracks with computed tracks. The deviations are less than 1% in radius and effective temperatures for most of the cases considered. We also checked that the present isochrones provide nice fits to four couples of observed detached binaries and to the observed sequences of the open clusters NGC 3532 and M67. Including atomic diffusion in our models with M< 1.1 M☉ leads to variations in the surface abundances that should be taken into account when comparing with observational data of stars with measured metallicities. For that purpose, iso-Zsurf lines are computed. These can be requested for download from a dedicated web page, together with tracks at masses and metallicities within the limits covered by the grids. The validity of the relations linking Z and [Fe/H] is also re-assessed in light of the surface abundance variations in low-mass stars. [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]

We present an analysis of high-resolution spectra for two pulsating Am stars in the Kepler field. The stellar parameters derived in this way are important because parameters derived from narrow-band photometry may be affected by the strong metal lines in these stars. We analyse the Kepler time series of ten known Am stars and find that six of them clearly show δ Scuti pulsations. The other four appear to be non-pulsating. We derive fundamental parameters for all known pulsating Am stars from ground-based observations and also for the Kepler Am stars to investigate the location of the instability strip for pulsating Am stars. We find that there is not much difference between the Am-star instability strip and the δ Scuti instability strip. We find that the observed location of pulsating Am stars in the HR diagram does not agree with the location predicted from diffusion calculations. [ABSTRACT FROM AUTHOR]

We have discovered both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a γ Doradus and a δ Scuti star, which makes it the first pulsating star to be a member of two classes. The analysis of our 128 h of multisite spectroscopic observations carried out over two seasons reveals that the star is a single-lined spectroscopic binary with an orbital period of 3.10575±0.00010 d and an eccentricity of 0.352±0.011. Only weak pulsational signals are found in both the radial velocity and line-profile variations, but we have succeeded in showing that the two highest-amplitude γ Doradus pulsation modes are consistent with ℓ=1 and |m|=1. These two modes dominated our 280 h of BVI[sub C] multisite photometry, also obtained over two seasons. We detected altogether ten frequencies in the light variations, one in the δ Scuti regime and nine in the γ Doradus domain. Five of the γ Doradus frequencies are exact integer multiples of the orbital frequency. This observation leads us to suspect they are tidally excited. Attempts to identify modes from the multicolour photometry failed. We performed model calculations and a stability analysis of the pulsations. The frequency range in which δ Scuti modes are excited agrees well with observations. However, our models do not show excitation of γ Doradus pulsations, although the damping is smaller in the observed range. We also investigated tidal excitation of γ Doradus modes. Some of the observed harmonics of the orbital period were found to be unstable. The observed orbital harmonics which are stable in the models can be understood as linear combinations of the unstable modes. We could not detect the secondary component of the system in infrared photometry, suggesting that it may not be a main-sequence star. Archival data of this star show that it has a strong ultraviolet (UV) excess, the origin of which is not known. The orbit of the primary is consistent with a secondary mass of M>1.04 M[sub ⊙], which is indicative of a neutron star, although a white dwarf companion is not ruled out. [ABSTRACT FROM AUTHOR]