Eclipsing binaries can in principle provide additional constraints to facilitate asteroseismology of one or more pulsating components. We have identified 94 possible eclipsing binary systems in a sample of over 1800 stars observed in long cadence as part of the Kepler Guest Observer Program to search for γ Doradus and δ Scuti star candidates. We show the results of a procedure to fold the light curve to identify the potential binary period, subtract a fit to the binary light curve, and perform a Fourier analysis on the residuals to search for pulsation frequencies that may arise in one or both of the stellar components. From this sample, we have found a large variety of light curve types; about a dozen stars show frequencies consistent with δ Sct or γ Dor pulsations, or light curve features possibly produced by stellar activity (rotating spots). For several stars, the folded candidate ‘binary’ light curve resembles more closely that of an RR Lyr, Cepheid, or high-amplitude δ Sct star. We show highlights of our results and discuss the potential for asteroseismology of the most interesting objects.

We have previously calculated a number of 2D hydrodynamic simulations of convection and pulsation to full amplitude. These revealed a significantly better fit to the observed light curves near the red edge of the instability strip in the globular cluster M 3 than did previous 1D mixing length models. Here we compare those 2D results with our new 3D hydrodynamic simulations calculated with the same code. As expected, the horizontal spatial behaviour of convection in 2D and 3D is quite different, but the time dependence of the convective flux on pulsation phase is quite similar. The difference in pulsation growth rate is only about 0.1% per period, with the 3D models having more damping at each of the five effective temperatures considered. Full amplitude pulsation light curves in 2D and 3D are compared.

We studied seven β Cep stars photometrically over the past ten years. Some showed amplitude variations, some frequency changes, and others exhibited stable pulsations, with no consistent picture yet emerging. Additionally, 12 Lac appears to have a 6.7-yr binary companion.

KIC 6761539 is one of many fast rotating γ Doradus – δ Scuti hybrid pulsators. A search for possible regularities in the frequency spectrum is performed and a first stellar model is presented.

Pysca, a Python software package for automated extraction of frequencies, amplitudes and phases from non-equally sampled photometric time series, is presented.

The searches for transiting exoplanets have produced a vast amount of time-resolved photometric data of many millions of stars. One of the leading ground-based surveys is the SuperWASP project. We present the initial results of a survey of over 1.5 million A-type stars in the search for high frequency pulsations using SuperWASP photometry. We are able to detect pulsations down to the 0.5 mmag level in the broad-band photometry. This has enabled the discovery of several rapidly oscillating Ap stars and over 200 δ Scuti stars with frequencies above 50 d−1, and at least one pulsating sdB star. Such a large number of results allows us to statistically study the frequency overlap between roAp and δ Scuti stars and probe to higher frequency regimes with existing data.

We explore the stability of extremely low-mass stars (M < 0.25 M⊙) across a wide range of composition, effective temperature, and luminosity. We identify the instability boundaries associated with radial oscillations. These are a strong function of both composition and radial order (0 ≤ n ≤ 13). The classical blue edge shifts to higher effective temperature and luminosity with decreasing hydrogen abundance. Higher-order modes are more easily excited, and small islands of instability develop. Short-period oscillations have been discovered in the low-mass pre-white dwarf component of the eclipsing binary J0247–25. If its envelope is depleted in hydrogen, J0247–25B is unstable to intermediate-order p modes. Driving is by the classical κ mechanism operating in the second helium ionization zone. The observed periods, temperature and luminosity of J0247–25B require an envelope hydrogen abundance 0.2 ≤ X ≤ 0.3.

Follow-up (U)BVRI photometric observations have been carried out for 42 RR Lyrae stars in the Kepler field. The new magnitude and color information will complement the available extensive high-precision Kepler photometry and recent spectroscopic results. The photometric observations were made with the following telescopes: 1-m and 41-cm telescopes of Lulin Observatory (Taiwan), 81-cm telescope of Tenagra Observatory (Arizona, USA), 1-m telescope at the Mt. Lemmon Optical Astronomy Observatory (LOAO, Arizona, USA), 1.8-m and 15-cm telescopes at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea) and 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO, Korea). The observations span from 2010 to 2013, with ~200 to ~600 data points per light curve. Preliminary results of the Korean observations were presented at the 5th KASC workshop in Hungary. In this work, we analyze all observations. These observations permit the construction of full light curves for these RR Lyrae stars and can be used to derive multi-filter Fourier parameters.

Precision asteroseismology uses the observed effective temperature and luminosity or surface gravity in selecting evolutionary models for analysis. In the case of the primary component of μ Eri, an SPB variable, the surface gravity and luminosity can be derived from the parameters of the SB1 eclipsing system. We examine how the surface gravity and luminosity so derived help to select the evolutionary models suitable for asteroseismic analysis.

BL Her type pulsating variable stars are a subtype of Type II Cepheids, pulsating with periods in the range from 1 to 4 days. The General Catalog of Variable Stars lists 71 objects. For each star from this list, we searched for data in the publicly available photometric databases: AAVSO, ASAS, Catalina Sky Survey, INTEGRAL OMC, LINEAR, NSVS, SuperWASP. The analysis was done separately for each dataset. Here we present first results.

We present frequency analysis of the Kepler light curve of KIC 10486425, an eclipsing binary system with a pulsating component. The parameters of the binary were obtained by modelling the light curve with the Wilson-Devinney program. The residuals from this modelling were subject to Fourier analysis which allowed us to detect 120 periodic terms characteristic for γ Dor-type pulsations. The dominant frequency of these changes amounts to 1.3189 d−1.

We present a large observing project monitoring globular clusters (GC) over long time baselines, which will lead to a complete census of variable stars in those clusters down to several magnitudes below the horizontal branch (HB). The use of Lucky Imaging (LI) will allow us to obtain high-precision photometry for even faint objects, and long-term monitoring will also mean that observations are sensitive to detecting other slow transient phenomena, such as gravitational microlensing, the primary aim of this project.

We present the new, second spectroscopic telescope of Poznań Astronomical Observatory. The telescope allows automatic simultaneous spectroscopic and photometric observations and is scheduled to begin operation from Arizona in autumn 2013. Together with the telescope located in Borowiec, Poland, it will constitute a perfect instrument for nearly continuous spectroscopic observations of variable stars. With both instruments operational, the Global Astrophysical Telescope System will be established.

The definition of γ Dor stars as a new class of variable stars by Kaye et al. (1999) was based on a number of criteria, including the failure to detect any emission in the Ca II H & K lines in these stars (Kaye & Strassmeier 1998; KS98). Over the last 30 years, efforts continue to look for the blue edge of chromospheric activity. As a part of this effort, we put γ Dor stars to the test to see if magnetic fields play a non-trivial role in their variability.

We present preliminary results of the variability survey in the field of the globular cluster NGC 4833. We observed all 34 variable stars known in the cluster. In addition, we have found two new SX Phoenicis stars, one new RR Lyrae star, twelve new eclipsing systems mostly of the W Ursae Majoris type, nine new variable red giants, and ten new field-stars showing irregular variations. Properties of RR Lyrae stars indicate that NGC 4833 is an Oosterhoff's type II globular cluster.

Fourier analysis of the light curve of AC And from the HATNet database reveals the rich frequency structure of this object. Above 30 components are found down to the amplitude of 3 mmag. Several of these frequencies are not the linear combinations of the three basic components. We detect period increase in all three components that may lend support to the Population I classification of this variable.

The Kepler space telescope has proven to be a gold mine for the study of variable stars. Unfortunately, Kepler only returns a handful of pixels surrounding each star on the target list, which omits a large number of stars in the Kepler field. For the open clusters NGC 6791 and NGC 6819, Kepler also reads out larger superstamps which contain complete images of the central region of each cluster. These cluster images can potentially be used to study additional stars in the open clusters. We present preliminary results from using traditional photometric techniques to identify and analyze additional variable stars from these images.

We developed an advanced binary system model that includes stellar oscillations on one or both stars, with the goal of mode identification by fitting of the photometric light curves. The oscillations are modeled as perturbations of the local surface temperature and the local gravitational potential. In the case of tidally distorted stars, it is assumed that the pulsation axis coincides with the direction connecting the centers of the components rather than with the rotation axis. The mode identification method, originally devised by B. Bíró, is similar to eclipse mapping in that it utilizes the amplitude, phase and frequency modulation of oscillations during the eclipse; but the identification is achieved by grid-fitting of the observed light curve rather than by image reconstruction. The proposed model and the mode identification method have so far been tested on synthetic data with encouraging results.

We investigate the radial pulsation properties of massive main-sequence stars using both linear and non-linear calculations. Using 20, 40, 60 and 85 solar-mass models evolved by Meynet et al. (1994), we calculate nonlinear hydrodynamic envelope models including the effects of time-dependent convection. Many of these models are massive enough to lose a significant amount of mass as they evolve, which also reveals more helium-rich layers. This allows us to investigate the dependence of pulsation on mass, metallicity and surface helium abundance. We find that as a model loses mass, the periods become longer relative to the period predicted by the period-mean density relation (period × $\sqrt{\overline{\rho}}$ is proportional to a constant, Q) for the initial model. Increased surface helium abundance causes a dramatic decrease in the period relative to that expected from Q, while changing the metallicity had little impact on the expected periods.

We present results of a search for variable stars in the young open cluster NGC 2244. As a result we have found many eclipsing systems and pulsating stars, some of which are multiperiodic. Here we show only a few examples.