The Turkish astronomical community has installed several telescopes during the last 10 years. We describe this work and discuss the potential of young researchers in Turkey, with the aim of fostering collaborations in the field of cataclysmic variables and related objects.

We present a preliminary analysis of known planetary nebulae (PNe) in M31 that were observed in the first year of the Panchromatic Hubble Andromeda Treasury HST Multi-cycle program. We use the properties of this sample to discuss PNe from this new multi-band survey.

Globular clusters are known to have enhanced populations of binaries with compact objects, owing to the dynamical interactions taking place in their dense stellar environments. Both the single degenerate and double degenerate Type Ia supernova progenitors are expected to be similarly enhanced with respect to the field, but the theoretical predictions are highly uncertain. Here we discuss an archival survey aimed at constraining the fraction of Type Ia supernovae that explode inside globular clusters.

TODCOR is a TwO-Dimensional CORrelation technique to measure radial velocities of the two components of a spectroscopic binary. Assuming the spectra of the two components are known, the technique correlates an observed binary spectrum against a combination of the two spectra with different shifts. TODCOR measures simultaneously the radial velocities of the two stars by finding the maximum correlation. The main use of the technique has been to turn single-lined binaries into double-lined systems. This helps to explore the binary mass-ratio distribution, especially the low-mass regime, where the secondaries are usually very faint and therefore hard to detect. The technique has been generalized to study multi-order spectra, and also triple- and quadruple-lined systems. It has several applications in studying extrasolar planets and in the future may even help to dynamically measure stellar masses of binaries through relativistc effects.

The total number of true, likely and possible planetary nebulae (PN) now known in the Milky Way is about 3000, approximately twice the number known a decade ago. The new discoveries are a legacy of the recent availability of wide-field, narrowband imaging surveys, primarily in the light of Hα. The two most important are the AAO/UKST SuperCOSMOS Hα survey SHS and the Isaac Newton photometric Hα survey IPHAS, which are responsible for most of the new discoveries. A serious problem with previous PN catalogs is that several different kinds of astrophysical objects are able to mimic PN in some of their observed properties leading to significant contamination. These objects include H~II regions and Strömgren zones around young O/B stars, reflection nebulae, Wolf-Rayet ejecta, supernova remnants, Herbig-Haro objects, young stellar objects, B[e] stars, symbiotic stars and outflows, late-type stars, cataclysmic variables, low redshift emission-line galaxies, and even image/detector flaws. PN catalogs such as the Macquarie/AAO/Strasbourg Hα Planetary Nebula catalog (MASH) have been carefully vetted to remove these mimics using the wealth of new wide-field multi-wavelength data and our 100% follow-up spectroscopy to produce a compilation of new PN discoveries of high purity. During this process significant numbers of PN mimics have been identified. The aim of this project is to compile these MASH rejects into a catalog of Miscellaneous Emission Nebulae (MEN) and to highlight the most unusual and interesting examples. A new global analysis of these MEN objects is underway before publishing the MEN catalog online categorizing objects by type together with their spectra and multi-wavelength images.

Computing the rate of Type Ia supernovae (SNe Ia) from first principles is difficult because there are large uncertainties regarding several key binary processes such as common envelope evolution, tidal interactions, and the efficiency of mass transfer. Fortunately, a range of observational parameters of binaries in intermediate stages of evolution can help us model these processes in a way that is likely to mirror the true binary evolution. We discuss how this observationally-motivated approach may have the effect of increasing the predicted rate of single degenerate progenitors of SNe Ia, while simultaneously decreasing the number of double degenerate progenitors.

We determine elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe) using direct methods and a large set of observed ions, minimizing the need for ionization correction factors. In contrast to prior studies, we find a clear separation between Type I and non-Type I PNe in these low-metallicity environments, and no evidence that the O-N nucleosynthesis cycle is active in low-mass progenitors. We find that the S/O abundance ratio is anomalously low compared to H ii regions, confirming the “sulfur anomaly” found for Galactic PNe. We also found that Ne/O is elevated in some cases, raising the possibility that Ne yields in low-mass AGB stars may be enhanced at low metallicity.

We report trigonometric parallx measurements for H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array. Based on astrometric monitoring for 1 year, we measured a trigonometric parallax of 0.89 ± 0.04 mas, corresponding to a distance of 1.12+0.05 −0.05 kpc. This is the most accurate distance to OH 231.8+4.2, and the first one based on an annual parallax measurement. The distribution and internal motions of the H2O masers are consistent with the bipolar outflow suggested in literatures.

We present high resolution long-slit spectra from the San Pedro Martir kinematic catalogue (López et al. 2012) of plantetary nebulae M1-32 and M2-42 and their modeled PV diagrams using the 3-D morpho-kinematic code SHAPE. We find high-speed collimated outflows, surrounded by a equatorial thick torus/ring. The same SHAPE model is able to fit both planetary nebulae assuming one cylindrical velocity field for the outflows and one Hubble-law for the torus/ring concluding that they may be akin objects which just appear at different projections.

Program SHELLSPEC is designed to calculate light-curves, spectra and images of interacting binaries and extrasolar planets immersed in a moving circumstellar environment which is optically thin. It solves simple radiative transfer along the line of sight in moving media. The assumptions include LTE and optional known state quantities and velocity fields in 3D. Optional (non)transparent objects such as a spot, disc, stream, jet, shell or stars may be defined (embedded) in 3D and their composite synthetic spectrum calculated. The Roche model can be used as a boundary condition for the radiative transfer. Recently, a new model of the reflection effect, dust and Mie scattering were incorporated into the code.

ϵ Aurigae is one of the most mysterious objects on the sky. Prior modeling of its light-curve assumed a dark, inclined, disk of dust with a central hole to explain the light-curve with a sharp mid-eclipse brightening. Our model consists of two geometrically thick flared disks: an internal optically thick disk and an external optically thin disk which absorbs and scatters radiation. Shallow mid-eclipse brightening may result from eclipses by nearly edge-on flared (dusty or gaseous) disks. Mid-eclipse brightening may also be due to strong forward scattering and optical properties of the dust which can have an important effect on the light-curves.

There are many similarities between interacting binary stars and transiting extrasolar planets. The reflection effect which is briefly reviewed is one of them. The exact Roche shape and temperature distributions over the surface of all currently known transiting extrasolar planets have been determined. In some cases (HAT-P-32b, WASP-12b, WASP-19b), departures from the spherical shape can reach 7-15%.

We report the optical and infrared studies of a sample of five new planetary nebulae (PNe) in the IPHAS and DSH catalogues. The PN status of these objects was confirmed by optical narrow-band imaging and low resolution spectroscopy. One object (IPHASX J195248.8+255359) is found to be a bipolar PN with faint Hα lobes and a bright core in [O iii].

We developed a self-consistent stellar-nebular model for NGC 7009. This model reproduces the available observations ranging from optical to UV. The combined approach to the modeling process produces more constraints and thus more trustworty results. After obtaining the model, we perform a comparative study of the chemical composition of He, N, O, Ne, Cl, and S in the nebula and its central star. Concluding that the stellar composition agrees with the nebular composition with t 2 ≠ 0.00.

Post-AGB stars are key objects for the study of the dramatic morphological changes of low- to intermediate-mass stars on their evolution from the Asymptotic Giant Branch (AGB) towards the planetary nebula stage. There is growing evidences that binary interaction processes may very well have a determining role in the shaping process of many objects, but so far direct evidence is still weak. We aim at a systematic study of the dust distribution around a large sample of post-AGB stars as a probe of the symmetry breaking in the nebulae around these systems. We used imaging in the mid-infrared to study the inner part of these evolved stars to probe direct emission from dusty structures in the core of post-AGB stars in order to better understand their shaping mechanisms. We imaged a sample of 93 evolved stars and nebulae in the mid-infrared using VISIR/VLT, T-Recs/Gemini South and Michelle/Gemini North. We found that all the the proto-planetary nebulae we resolved show a clear departure from spherical symmetry. 59 out of the 93 observed targets appear to be non resolved. The resolved targets can be divided in two categories. The nebulae with a dense central core, that are either bipolar and multipolar. The nebulae with no central core have an elliptical morphology. The dense central torus observed likely host binary systems which triggered fast outflows that shaped the nebulae.

Spectral energy distributions of six proto-planetary nebulae showing 21 and 30μ features were fit with models obtained from 1D radiative transfer code, taking FeO and MgS respectively are the carriers of the features. Atomic abundances of these carrier materials were derived and they are lower or comparable to their stellar photospheric values. This stregthens the possibility of these materials to become the carriers of their respective features.

We use photoionization modeling to assess the binary nature of the central stars of NGC 2392 and NGC 6026. If they are close binaries, they are potential Type Ia supernovae (SNe Ia) progenitors if the total mass exceeds the Chandrasekhar limit. We show that the nucleus of NGC 2392 likely has a hot, massive (≃1 M⊙) white dwarf companion, and a total mass of ~1.6 M⊙, making it an especially interesting system. The binary mass in NGC 6026 is less, ~1.1 M⊙. Even though its orbital period is short, it is not considered to be an SNe~Ia progenitor.

In close eclipsing binary systems, measurements of the eclipse timing variations (ETV), obtained by means of accurate light curves, may be used to find circumbinary additional objects. The presence of these objects causes the motion of the eclipsing binary with respect to the centre of mass of the entire system and it results in advances or delays in the times of eclipses due to the light time effect. The most important issue of this project is to inspect the potential of detecting low mass substellar companions to close eclipsing binaries through the timing method. For this purpose, we use the public data from Kepler and CoRoT spacecrafts, collecting the light curves for a selected sample and analyzing the observed minus calculated (O-C) times of the eclipses in the search for ETVs and characterizing them. A large amplitude of the O-C ETVs can be explained in some cases by the presence of a third body in the system.

The RV analysis tool integrates widely used methods of radial velocity determination (CCF, TODCOR, BF) in an easy to use graphical environment. No advanced knowledge of these methods is required to use it. The obtained velocities may be immediately analyzed with the same tool as it comprises flexible fitting of orbital parameters, which includes the third body influence and pulsational velocities of the components. These features together help to establish the most accurate combination of templates, spectrum range, and method. Scripting functionality is to be implemented in the future.

The spectral energy distributions (SEDs) have being simulated for 1120 systems that contain brown dwarfs with different physical parameters and protoplanetary disks that are inclined at different angles. The SED's shape dependence on disk inclination toward the observer is discussed.

We present a photometric study of the newly discovered low-mass eclipsing binary NSVS 01031772 Cam based on observations obtained at Ondřejov observatory from 2007 – 2011.

The model of a young star with a low-mass secondary component (q = M2/M1 ≤ 0.1) accreting matter from a circumbinary (CB) disc is considered. It is assumed that the orbit and the CB disc can be coplanar and non-coplanar. The model parameters were varied within the following ranges: the component mass ratioq ranged from 0.1 to 0.003, the eccentricity e varied from 0 to 0.7, the inclination of the orbit plane to the CB disc ranged from 0 to 10 degrees, and the parameter that defines the viscosity of the system was also varied. A number of hydrodynamics models of such a system have been calculated by the SPH method and then the variations of the circumstellar extinction and phase brightness curves were determined. The calculated brightness curves differ in shape and amplitude and it depends on the model parameters and the orientation of the system relative to the observer. The results were used to analyze the cyclic activity of UX Ori type stars.