High resolution spectra of post-outburst novae show multiple components of ejected gas that are kinematically distinct. We interpret the observations in terms of episodes of enhanced mass transfer originating from the secondary star that result in the formation of discrete components of circumbinary gas and accretion onto the white dwarf (WD) that trigger nova outbursts. In this picture the concordance between absorption line velocities and emission line widths in most novae occurs as a result of the collision of the expanding nova ejecta with a larger mass of surrounding circumbinary gas. One implication of this model is that much of the accreted gas remains on the WD, leading to a secular increase in WD mass over each outburst event. Alternative scenarios to explain nova spectral evolution are possible that do not invoke circumbinary gas and a possible test of different models is proposed.

Neutron(n)-capture elements (atomic number Z > 30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe.

Using a population number synthesis code with detailed binary evolution, we calculate the distribution of the number of Type Ia supernovae as a function of time after starburst. This is done for both main progenitor scenarios (single degenerate and double degenerate), but also with various evolutionary assumptions (such as mass transfer efficiency, angular momentum loss, and common envelope description). The comparison of these theoretically predicted delay time distributions with observations in elliptical galaxies then allows us to constrain the evolutionary scenarios and parameters. From the morphological shape of the distributions, we conclude that all supernovae Ia cannot be produced through the single degenerate scenario alone, with the best match being obtained when both scenarios contribute. Within the double degenerate scenario, most systems go through a phase of quasi-conservative, stable Roche lobe overflow. We propose stellar rotation as a possible solution for the underestimation of the absolute numbers of events predicted by many theoretical population synthesis studies. A brief comparison with these other studies is made, showing good correspondence under the nontrivial condition of equivalent assumptions. We also investigate the influence of different supernova Ia progenitors and evolutionary parameters on the theoretical distribution of the iron abundance of G-type dwarfs in the Galactic disk. These stars are good indicators of the entire chemical history of the Galaxy, and their predicted metallicity distribution can also be compared to the observed ones. This again limits the number of acceptable combinations of assumptions. Supporting previous results, the best correspondence is found in the case where both the single and double degenerate scenario contribute.

Various processes can lead to non-conservative evolution in binary stars. Under conservative mass transfer, both the total mass and the orbital angular momentum of the system are conserved. Thus, the transfer of angular momentum between the orbit and the spins of the stars can represent one such effect. Stars generally lose mass and angular momentum in a stellar wind so, even with no interaction, evolution is non-conservative. Indeed, a strong wind can actually drive mass transfer. During Roche lobe overflow itself, mass transfer becomes non-conservative when the companion cannot accrete all the material transferred by the donor. In some cases, material is simply temporarily stored in an accretion disc. In others, the companion may swell up and initiate common envelope evolution. Often the transferred material carries enough angular momentum to spin the companion up to break-up, at which point it could not accrete more. We investigate how this is alleviated by non-conservative evolution.

The precision of observations using observatories in space exceeds by a factor of 100 the accuracy of the light curve and line profile synthesis methods developed decades ago. Furthermore, physical effects too small to detect using ground based observations, such as aberration and Doppler beaming, become important when observing from space.

The GDDSYN method, developed by Hendry and Mochnacki, is both accurate and efficient, and is useful in the new context of space-based observations. Using a geodesic distribution of triangular surface elements varying little in size, it provides an alternative to the Wilson-Devinney code used at the heart of PHOEBE, and is adaptable to the new physical effects which are now observable. Tests and improvements are discussed.

We present a code which can be used to simulate the light curve of a binary system harbouring a non-circular accretion disk, and show that such a system geometry can produce light curves with asymmetric minima and different heights of the maxima. We have applied this code to check for the possible existence of a non-circular accretion disk, as suggested by Smak & Plavec (1997), in the Algol-type binary KU Cyg. We compare the best solutions for two sets of multicolour light curves, obtained within circular and non-circular disk models.

V393 Scorpii is a bright Galactic Double Periodic Variable showing a long photometric cycle of ≈253 days. The ASAS V-band light curve has been disentangled into an orbital and long cycle component. The orbital light curve was modeled with two stellar components and a circumprimary accretion disk. Based on this model, and the careful choice of a template spectrum for the donor, the contribution of the donor to the line+continuum spectrum was removed at every orbital phase. The remaining residual spectra were analyzed. Notable findings are the larger line emissivity observed during the long cycle maximum that is concentrated to low velocities and the presence of discrete absorption components in the wings of the OI 7773 line, whose visibility strongly depends on the orbital phase. In addition, weak emission is observed in donor metallic absorption lines. Finally, we present the first Hα Doppler map for V 393 Scorpii. A modulated wind explains many observational features.

MY Ser is an eclipsing early-type contact system. Both components are of spectral type O6 III. Using ESO archive spectra, we show that the radial velocity of the third body, which contributes about half of the total luminosity, changed from 2006 to 2009. The line profiles of the eclipsing system have peculiar shapes and strengths; namely around conjunctions, they are affected by circumbinary matter.

Many complex organic molecules and inorganic solid-state compounds have been observed in the circumstellar shell of stars (both C-rich and O-rich) in the transition phase between Asymptotic Giant Branch (AGB) stars and Planetary Nebulae (PNe). This short (~102-104 years) phase of stellar evolution represents a wonderful laboratory for astrochemistry and provides severe constraints on any model of gas-phase and solid-state chemistry. One of the major challenges of present day astrophysics and astrochemistry is to understand the formation pathways of these complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene in the case of a C-rich chemistry and oxides and crystalline silicates in O-rich environments) in space. In this review, I present an observational review of the molecular processes in the late stages of stellar evolution with a special emphasis on the first detections of fullerenes and graphene in PNe.

V479 And is a 14.26 hour, close binary system, comprised of a G8-K0 star departing from the main sequence and a compact primary star accreting matter from the donor. The object is an X-ray source, modulated with the orbital period. This, and the presence of an intense He II line, leads us to speculate that the compact object is a magnetic white dwarf. However, we do not find strong constraints on the upper mass limit of the compact object, and we may have a neutron star in a low mass X-ray binary instead of a cataclysmic variable. The orbital period is certainly too short for the donor star to be an evolved giant star, so classifying this object as a symbiotic binary may be a big stretch; however there is an evidence that the mass transfer occurs via stellar winds, rather than through the L1 point of Roche filling secondary, a phenomenon more common for symbiotic stars.

The low surface brightness usually associated with nebulae mixing with the ISM has long been a substantial obstacle in the observation and statistical study of these interactions. Thanks to the detection capability of the INT Photometric H-alpha Survey (IPHAS), in terms of sensitivity and imaging resolution, we were able to detect and select tens of examples of candidate Planetary Nebulae apparently at different stages of interaction with the interstellar medium (PNe-ISM hereafter) following the Wareing et al. (2007) classification. A spectroscopic investigation was conducted with the San Pedro Martir 2.1m telescope (SPM) in Mexico and we present the first results involving a proper classification and analysis of our candidates. The main difficulty is visually separating PNe-ISM from other faint asymmetric nebulosities such as old HII regions, SNRs and general diffuse H-alpha structures. This investigation is a first step in a more comprehensive study of PNe-ISM as more candidates are uncovered by the IPHAS team.

The eclipsing variable stars GSC 44870347 and GSC 4513 2537 are recently discovered binary systems (Otero et al., 2006) with orbital periods 1d.99 and 6d.33 days. We carried out the photometric observations of these eclipsing binaries from 2009-2010 using a CCD-array at the Tien-Shan Observatory in Kazakstan, at the Crimea Station of the Sternberg Astronomical Institute, at the Astrokolkhoz Observatory in New Mexico (AAVSO), while the spectrophotometric observations were obtained at the Starlight Farm Observatory in Barnesville, USA.

Exoplanets orbiting rapidly rotating stars may have unusual light curve shapes. These objects transit across an oblate disk with non-isotropic surface brightness, caused by the gravitational darkening. If such asymmetries are measured, one can infer the orbital obliquity of the exoplanet and the gravity darkened star, even without the analysis of the Rossiter-McLaughlin effect or interferometry. Here we introduce KOI-13 as the first example of a transiting system with a gravity darkened star.

Using the Subaru telescope and its FOCAS spectrograph in multi-object mode, we have obtained spectra of a selection of bright PNs in two galaxies: the Virgo giant elliptical M 60 (NGC 4649), and the starburst spiral M 82. We report on individual extinctions, as determined from the Balmer decrement, and also on the intensities of [O III] 4959 and 5007 relative to Hβ.

If recurrent novae (RNe) are progenitors of Type Ia Supernovae (SNe Ia), their white dwarfs (WD) must have masses close to the Chandrasekhar limit. The most reliable means of determining WD masses in RNe is dynamically, via radial-velocity and rotational-broadening measurements of the companion star. Such measurements require the system to be both eclipsing and to show absorption features from the secondary star. The only other reliable RNe mass estimate is for U Sco, which has a WD mass of 1.55 ± 0.24 M⊙ (Thoroughgood et al. 2001).

We present new time-resolved, intermediate-resolution spectroscopy of the eclipsing RN CI Aql during quiescence. We find the mass of the WD to be 1.02 ± 0.08 M⊙ and the mass of the secondary star to be 2.41 ± 0.2 M⊙. We estimate the radius of the secondary to be 2.10 ± 0.07 R⊙. The high mass ratio of q=2.37 ± 0.15 and the high secondary star mass suggests that mass transfer occurs on a thermal timescale. We suggest that CI Aql is evolving into a supersoft x-ray source, and ultimately will explode as an SN Ia.

A sample of ~150 compact Galactic PNe has been observed with the Spitzer/IRS spectrograph to characterize their dust properties. These PNe are likely to be at the onset of the PN evolutionary phase, and are therefore ideal for probing dust evolution. The molecular emission features in these Galactic PN spectra are similar to those found in our Magellanic Cloud sample, except that we found a sizable fraction of PNe with mixed-chemistry dust which are not observed in the Clouds. We also found that the distribution among dust types depends strongly on the metallicity of the parent population, implying that the metallicity of the progenitors affects the evolution of a PN from its early stages.

The internal heat loss or cooling of a planet determines its structure and evolution. We address in a consistent fashion the coupling between the day and the night sides by means of model atmosphere calculations with heat redistribution. We assume that a strong convection leads to the same entropy on the day and night side and that the gravity is the same on both hemispheres. We argue that the core cooling rate from the two hemispheres of a strongly irradiated planet may not be the same and that the difference depends on several important parameters. If the day-night heat redistribution is very effective, or if it takes place at a large optical depth, then the day-side and the night-side cooling may be comparable. However, if the day-night heat transport is not effective, or if it takes place at a shallow optical depth, then there can be a big difference between the day-side and the night-side cooling and the night side may cool more effectively. If the stellar irradiation gets stronger e.g. due to the stellar evolution or migration, this will reduce both the day and the night side cooling. Enhanced metallicity in the atmosphere acts as a “blanket” and reduces both the day- and the night-side cooling. However, the stratosphere on the day side of the planet can enhance the day-side cooling since its opacity acts as a “shield” which screens the stellar irradiation. These results might affect the well known gravity darkening and bolometric albedo effects in interacting binaries, especially for strongly irradiated cold objects.

The main goal of this work was to find dependencies between Fourier coefficients, which were developed by light curve fitting with Fourier polynomials. The light curves were acquired from the ASAS database (All Sky Automated Survey). In this statistical research it was necessary to sort and modify these data, because light curves of eclipsing binaries are just part of a bigger database, which contains the light curves of pulsating variable stars, novas etc. It was required to phase and normalize all of our light curves, that it could be possible to use a program to fit light curves with Fourier coefficients. Thereafter, we were looking for relations between Fourier coefficients.

Galactic post-AGB stars show a large diversity in chemical compositions as well as in the kinematical and geometrical properties of their circumstellar material. The theoretical interpretation is hampered by the lack of good distances to almost all Galactic objects. We therefore initiated a large project to study systematically post-AGB stars in the Large and Small Magellanic Cloud (LMC, SMC respectively). Here we report on our preliminary results.

We propose to measure the radii of the Penn State - Toruń Planet Search (PTPS) exoplanet host star candidates using the CHARA Array. Stellar radii estimated from spectroscopic analysis are usually inaccurate due to indirect nature of the method and strong evolutionary model dependency. Also, the so-called degeneracy of stellar evolutionary tracks due to convergence of many tracks in the giant branch decreases the precision of such estimates. However, the radius of a star is a critical parameter for the calculation of stellar luminosity and mass, which are often not well known especially for giants. With well determined effective temperature (from spectroscopy) and radius, the luminosity may be calculated precisely. In turn also stellar mass may be estimated much more precisely. Therefore, direct radii measurements increase precision in the determination of planetary candidates masses and the surface temperatures of the planets.