Dynamical models of strongly irradiated gas-giant atmospheres exhibit a range of behavior, the nature of which depends on both the adopted parameters and the adopted numerical model. Discerning the correct choice of physical parameters and modeling philosophy can be difficult. Here, I present a series of wavelength-dependent transmission spectra for the giant planet HD209458b based on 3D radiative hydrodynamical models for a range of kinematic viscosities. While flow patterns and temperature distributions can vary significantly, disk-averaged phase curves mask much of this information. Transmission spectra, on the other hand, probe the day-night transition where advective contributions dominate and differences are often most pronounced. Transmission spectra illustrate noticeable changes, especially when comparing the differences between transmission spectra of eastern and western hemispheres, as might be seen during ingress and egress.

In this study, we present the preliminary light curve analysis of the contact binary SW Lac, using B, V light curves of the system spanning 2 years (2009 - 2010). During the spot modeling process, we used the information coming from the Doppler maps of the system, which was performed using the high resolution and phase dependent spectra obtained at the 2.1m Otto Struve Telescope of the McDonald Observatory, in 2009. The results showed that the spot modeling from the light curve analysis are in accordance with the Doppler maps, while the non-circular spot modeling technique is needed in order to obtain much better and reliable spot models.

Gaia, the forthcoming astrometric ESA survey, is expected to substantially improve our knowledge about the distances to galactic planetary nebulae (PNe). We present an overview of Gaia mission and focus in some aspects which are relevant for the study of PNe. In particular, we present our simulations on Gaia spectrophotometric observations obtained by means of GOG (Gaia Object Generator) for a catalogue of proto-PNe and PNe (Suárez et al. 2006) which can be used as templates to classify and study the suitability of Gaia spectrophotometry to infer physical properties of the sources.

In this work, we present the first catalogue of optically variable sources observed by the Optical Monitoring Camera (OMC), with information about the variability of more than 5000 objects and periodicity of ~ 1000 sources.

The rapid response capability of Swift, together with the daily planning of its observing schedule, make it an ideal mission for following novae in the X-ray and UV bands. A number of both classical and recurrent novae have been extensively monitored throughout their supersoft phase. We report findings from these observations, including the high-amplitude flux variation often seen at the start of the supersoft emission, the optical plateau sometimes seen for recurrent novae, the differing relationships between the X-ray and UV variability, and the turn-on and turn-off times of the supersoft emission for the Swift sample of novae.

I provide a synthetic overview of the present status of stellar models for the asymptotic giant branch phase, one of the most complex and still uncertain stages of stellar evolution. In particular I will focus on two aspects that are most relevant in the context of the planetary nebulæ progeny, namely: the chemical composition of the AGB ejecta, and the mass of the bare CO core left after the ejection of the stellar mantle at the AGB tip. Recent progress, present uncertainties, and future perspectives to constrain AGB models are briefly discussed.

We investigate the thermal response of CO WDs accreting He-rich matter directly from their companions in binary systems. Our results suggest that the He-channel cannot provide progenitors for the majority of “normal” SNe Ia.

The Heliospheric Imagers (HI) onboard the STEREO satellites are observing an abundance of background stars as they follow their respective Sun-centered orbits. These are wide-angled CCD cameras with a 20°×20° field of view, directed ~14° from the solar disk. These imagers monitor 20% of the sky over one year, providing light curves for over 500,000 stars down to 12th magnitude and brighter than 7th. We are currently analysing the photometric data from the HI-1 cameras, obtained since March 2007. Following a standard data reduction of the raw photometric images, the resultant light curves underwent a sequence of detrending procedures to minimize systematics in the data, which can contribute to red noise. A transit search was performed using the BLS algorithm, which is sensitive to the box-like shape associated with planetary transits. The resulting candidates were subjected to a number of false-alarm tests to determine the most promising candidates and these were investigated further, visually and using available catalogue data. Possible new exoplanet and binary candidates will now be submitted for follow-up photometric and spectroscopic observations to confirm their nature.

A standard planetary nebula stays more than 10 000 years in the state of a photoionized nebula. As long as the timescales of the most important ionizing processes are much smaller, the ionization state can be characterized by a static photoionization model and simulated with codes like CLOUDY (Ferland et al. 1998). When the star exhibits a late helium flash, however, its ionizing flux stops within a very short period. The star then re-appears from its opaque shell after a few years (or centuries) as a cold giant star without any hard ionizing photons. Describing the physics of such behavior requires a fully time-dependent radiative transfer model. Pollacco (1999), Kerber et al. (1999) and Lechner & Kimeswenger (2004) used data of the old nebulae around V605 Aql and V4334 Sgr to derive a model of the pre-outburst state of the CSPN in a static model. Their argument was the long recombination time scale for such thin media. With regard to these models Schönberner (2008) critically raised the question whether a significant change in the ionization state (and thus the spectrum) has to be expected after a time of up to 80 years, and whether static models are applicable at all.

We present the precise multicolour photometry of the eclipsing variable EQ Boo (P = 5d.43, V = 8m.8), which is component “A” of the visual double star ADS 9422 (F7 V+G0 V, ρ = 1.3”, Δmag = 0.7). From the analysis of these data, we can propose the existence of the fourth component with a late spectral type.

We show the influence of the Keplerian velocity shear on the line profiles of cataclysmic variable discs. The complete disc structure is taken into account. The radial disc structure follows the alpha disc approximation. Based on this assumption, the vertical structure is computed using the detailed non-LTE code AcDc. The obtained opacities and source functions are interpolated in the 2D grid, where the radiative transfer is calculated with the inclusion of the velocity field gradient.

New transit light curves of the third body in the system AV CMi have been obtained. The eclipsing pair's light curves were re-analysed with the W-D code and new absolute elements were derived for the two components. Moreover the new light curves (together with those given by Liakos & Niarchos 2010) of the third body transiting one of the components were analysed with the Photometric Software for Transits (PhoS-T). The results from both analyses are combined with the aim to study the nature of the third component.

We present new results of 3-D AMR MHD simulations focusing on two distinct aspects of PPN evolution. We first report new simulations of collimated outflows driven entirely by magnetic fields. These Poynting flux dominated “magnetic towers” hold promise for explaining key properties of PPN flows. Our simulations address magnetic tower evolution and stability. We also present results of a campaign of simulations to explore the development of accretion disks formed via wind capture. Our result focus on the limits of disk formation and the range of disk properties.

White dwarfs grow as the cores of red giants and, in particular, carbon-oxygen white dwarfs grow in asymptotic giant branch (AGB) stars. The evolution of an AGB star is a competition between growth of the core and loss of the stellar envelope, typically in a wind. It is complicated by thermal pulses driven periodically by unstable helium shell burning. Dredge up following such pulses delays core growth. The compression at the center of a cold carbon-oxygen core means that carbon ignites when it reaches a mass of 1.38 M⊙. This begins the familiar thermonuclear runaway of the Type Ia supernova (SN Ia). At higher temperatures carbon can ignite more gently and burn mostly to neon to leave a core rich in oxygen, neon and magnesium. Such cores can go on to collapse to neutron stars with a release of only neutrinos. Accepted mass-loss prescriptions for giants mean that the range of masses of single stars that leave carbon-oxygen white dwarfs is somewhere from around 1 to 8 M⊙. We investigate how unusual mass loss, perhaps brought about by interaction with a binary companion, can radically alter the single star picture. Though population syntheses treat some possibilities with various prescriptions, there is sufficient doubt over the physics, the observations, and the implementation of mass loss and binary interaction that there is scope for several more unusual progenitors of carbon-oxygen white dwarfs and hence SNe Ia.

We reanalyze a selection of the XMM-Newton RGS (Reflection Grating Spectrometer) data of two classical novae; V4743 Sgr and V2491 Cyg. The high resolution nova spectra in the X-ray wavelengths show existence of absorption features (e.g., blue shifted). Our main aim is to model the absorption components detected in the high resolution spectra independently from the assumed continuum model. We assume that there is complex absorption of interstellar, photospheric, and of collisionally and/or photoionized gas origin in the moving material along the line of sight from a nova wind or ejecta. In addition to deriving the absorption properties, we obtain CNO abundances of elements in the ejecta/nova wind.

We carefully consider numerous explanations for the sulfur abundance anomaly in planetary nebulae. No one rationale appears to be satisfactory, and we suggest that the ultimate explanation is likely to be a heretofore unidentified feature of the nebular gas which significantly impacts the sulfur ionization correction factor.

We present results from systematic Herschel/HIFI observations of molecular lines in the FIR/sub-mm from young planetary nebulae. The high spectral resolution provided by the hetorodyne spectrometer HIFI allows properly studying the line profiles, whose structure corresponds to the various kinematics of the most massive nebular components, including fast bipolar outflows and slow shells. In particular, we have studied the excitation properties of the high-velocity (dense) flows. In some cases we find typical temperatures of the fast gas over 100-200 K, though in others it remains cool, ≲30K. We argue that the thermodynamics of the molecule-rich bipolar outflows is driven by fast radiative cooling, after the passage of the shock that accelerated it.

In this review I will present recent results between 2007 and 2011 based on interferometric observations of binaries and multiple systems with the VLTI, NPOI, SUSI and CHARA instruments. I will also explain the kind of constraints an interferometer can provide in order to better understand the physics of multiple systems.

We present a unified model of the central star and the ionized gas of the planetary nebula He2-131. Preliminary values of the nebular and stellar parameters are given together with those of the chemical composition.

The preliminary results of a study of a neglected, relatively bright, short-periodic (P=0.48 d), near contact eclipsing binary BS Vulpeculae is given. We present our new complete (BVRI) light curves, and physical parameters of the system based on them, derived by the 2003 version of the Wilson–Van Hamme code.