The Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae, allowing the detection of tiny periodic light curve variations, a possible signature of binarity. With this precision free from the observational gaps dictated by weather and lunar cycles, we are able to detect companions at much larger separations and with much smaller radii than ever before. We have been awarded observing time to obtain light-curves of the central stars of the six confirmed and possible planetary nebulae in the Kepler field, including the newly discovered object Kn 61, at cadences of both 30 min and 1 min. Of these six objects, we could confirm for three a periodic variability consistent with binarity. Two others are variables, but the initial data set presents only weak periodicities. For the central star of Kn 61, Kepler data will be available in the near future.

We present preliminary results of the first near-infrared variability study of the Arches cluster, using adaptive optics data from NIRI/Gemini and NACO/VLT. The goal is to discover eclipsing binaries in this young (2.5 ± 0.5 Myr), dense, massive cluster for which we will determine accurate fundamental parameters with subsequent spectroscopy. Given that the Arches cluster contains more than 200 Wolf-Rayet and O-type stars, it provides a rare opportunity to determine parameters for some of the most massive stars in the Galaxy.

We investigated the ionization structure of symbiotic binaries during their active phases. We found that a neutral disk-like zone around the hot star can be created as a result of its enhanced wind and fast, 200 - 300 km s−1, rotation. Calculated column densities of the neutral hydrogen atoms throughout the neutral zone and emission measures of the ionized part of the wind from the hot star are in a good agreement with those derived from observations.

cmfgen is an atmosphere code developed to model the spectra of a variety of objects – O stars, Wolf-Rayet stars, luminous blue variables, A and B stars, central stars of planetary nebula, and supernovae. The principal computational aim of cmfgen is to determine the temperature and ionization structure of the atmosphere, and the atomic level populations. Toward this end, we have developed several different radiative transfer modules that (a) solve the transfer equation for spherical geometry in the comoving frame, (b) solve the static transfer equation in the plane parallel approximation without, or with, a vertical velocity field, (c) solve the static transfer code for a spherical atmosphere allowing for all relativistic terms, (d) solve the time-dependent spherical transfer equation to first order in v/c for a homologous expansion, and (e) solve the time-dependent spherical transfer equation allowing for all relativistic terms. To achieve consistency between the radiation field, temperature structure, and level populations we use a linearization technique. Line blanketing is accurately treated while complex photoionization cross-sections, containing numerous resonances, can also be handled. Spectra, for comparison with observation, are computed using cmf_flux. Several other auxiliary programs have also been developed – these include diagnostic tools as well as programs that allow the effect on spectra of rotation and departures from spherical geometry to be investigated. In this presentation we will briefly describe cmfgen and auxiliary codes.

During the transition from an AGB star to a planetary nebula, a large number of low/intermediate initial mass stars loses its spherical symmetry. The process responsible for that change of morphology is, so far, not well understood. The candidates responsible for shaping these objects are (i) a companion to the star (binary/heavy planet) and its tidal forces, (ii) disk interaction and (iii) magnetic fields - or a combination of these. In particular a binary induced magnetic field is a promising option. To study this we observed the polarization of H2O masers in the known binary pre-Planetary Nebula (pPN) OH231.8+4.2. Our results show a magnetic field B || of ~45 mG is present in the H2O maser region of this pPN.

The remnants of Type Ia supernovae (SNe Ia) can provide important clues about their progenitor histories. We discuss two well-observed supernova remnants (SNRs) that are believed to have resulted from SNe Ia, and use various tools to shed light on the possible progenitor histories. We find that Kepler's SNR is consistent with a symbiotic binary progenitor consisting of a white dwarf and an AGB star. Our hydrosimulations can reproduce the observed kinematic and morphological properties. For Tycho's remnant we use the characteristics of the X-ray spectrum and kinematics to show that the ejecta has likely interacted with dense circumstellar gas.

The differentially rotating convective envelope is an indispensable element of the magnetic dynamo working in RS CVn-systems. Tidal coupling is responsible for maintaining fast rotation, and also the observed high level of magnetic activity. In this work, we compare the physical properties of two well known RS CVn-type binaries, that is the long-period system σ Gem and the ellipsoidal variable ζ And. For the comparison, we use the results obtained from processing time-series Doppler images. We also aim at understanding how differential rotation could be affected by tidal forces in such close binaries.

There is at present no viable theory whereby a single star with M MS < 2.3 ± 0.3 M⊙ can sustain a PN-forming superwind with Ṁ > 3×10−5 M⊙ yr−1 at the tip of the AGB that can eject the last ~0.3 M⊙ of envelope mass. We propose that a binary companion can not only result in non-spherical PN, but more importantly provide the AGB mass loss rate enhancement that is required to create a visible PN. We provide an overview of our binary population synthesis calculations of the PN formation rates from common envelope (CE) interactions, CE mergers with substellar companions, tidally synchronized systems that avoid CE, gravitationally focused winds, and double degenerate systems. The predicted number of Galactic PN with radii < 0.9 pc shaped and created by a binary companion is 8,100±2,300 which is (71±20)% of the observationally-estimated total. We demonstrate that the observed close central star of PN binary fraction of 15–20% is consistent with our overall binary fraction, considering we predict two binary populations with period distributions centred at log P(days) ~0 and 4. Finally, we discuss the impact of binarity on the PN luminosity function, central star mass distribution, chemical abundances, morphologies, etc., and why these distributions predicted in the binary scenario are close to observations while the single star paradigm produces distributions which are measurably discrepant.

To date, there are several reported exoplanet detections within binary star systems. These findings are based on radial velocity data for the target star. However, the companion star could in turn have a companion of which we are not aware. We describe how this hidden binary system affects the radial velocity of the target star, mimicking a planet in some circumstances We also explain what can be done in practice in order to distinguish between these two effects.

New Hubble images of the reflection nebula CRL 2688 from 0.6 to 1.6μm reveal significant variations of color and opacity in the distribution of scattered starlight. We have constructed a detailed radiation-transfer model consisting principally of an optically thick equatorial disk-like structure; bipolar lobes with density enhancements along the polar axis and at the base of lobes; an optically thin extended envelope containing spherical density-enhanced shells to mimic the outer rings of CRL 2688; and a pair of near-stellar caps that collimate and redden the dispersing starlight near its source. Our model nicely reproduces all of the basic features detected in the HST images, including the famous searchlights and arcs, as well as the measured spectral energy distribution (“SED”) of CRL 2688. Assuming a distance of 420 pc we estimate the light originates in a giant star with a temperature T ~ 7000 K and a luminosity L = 5500 ± 1100 L ⊙.

We report spectrophotometric observations made with SOFIA/FORCAST on 2011 June 2 UT. Optical measurements have previously shown that the abundance discrepancy factor (adf) varies with position in several high-adf PNe, and is highest close to the central star. The very low electron temperature inclusions postulated to explain the abundance discrepancy, must be cooled predominantly by fine structure IR lines. These SOFIA data will map mid-IR FS lines (and our related Herschel program will add several far-IR FS lines) in the bright, well-characterized, high-adf PN NGC 7009. We will compare these IR results with FS optical line measurements in order to correlate ratios of IR to optical fluxes with position, and thus correlate with where the adf peaks.

We present an analysis of high precision V light curves (LC) for 18 local Type Ia supernovae (SNe Ia) as obtained with the same telescope and setup at the Las Campanas Observatory (LCO). This homogeneity provides an intrinsic accuracy of a few hundredths of a magnitude with respect to individual LCs and between different objects. Based on the single degenerate (SD) scenario, we identify patterns which have been predicted by model calculations as signatures of the progenitor and accretion rate which change the explosion energy and the amount of electron capture, respectively. Using these templates as principle components and the overdetermined system of SNe pairs, we reconstruct the properties of progenitors and progenitor systems. All LCO SNe Ia follow the brightness decline relation except 2001ay. After subtraction of the two components, the remaining scatter is reduced to ≈0.01m−0.03m. SNe Ia seem to originate from progenitors with main-sequence masses MMS > 3 M⊙ with the exception of two subluminous SNe Ia with MMS < 2 M⊙. The component analysis indicates a wide range of accretion rates in the progenitor systems closing the gap to accretion induced collapses (AIC). SN1991t-like objects show differences in decline rate (dm15) but no tracers of our secondary parameters. This may point to a different origin such as the double degenerate or pulsating delayed detonation scenarios. SN2001ay does not follow the decline relation. It can be understood in the framework of C-rich white dwarfs (WDs), and this group may produce an anti-Phillips relation. We suggest that this may be a result of a common envelope phase and mixing during central He burning as in SN1987A.

Having surveyed ≈ 10% of the sky, we have identified more than 130 PN candidates by surveying multicolour Digitized Sky Survey (DSS), Sloan Digitized Sky Survey (SDSS), and combined [O III], Hα and [S II] images. In a first imaging and spectroscopy campaign, 51 objects were identified as true and probable PNe. This work presents an additional 17 probable or possible PNe identified since that study. The majority of these candidates are situated at Galactic latitudes |b| > 5^, with the exception of seven objects located closer to the Galactic plane. Using the techniques described here that do not require any new survey data, we anticipate that many more PNe are waiting to be found, perhaps as many as 90.

Up to now, more than 500 extra-solar planets have been discovered. Many of these extrasolar systems consist of one star and only one giant planet. However, recently more and more different types of systems have become known, including also extrasolar planets in binaries. In our study, we will concentrate on such systems, since a large percentage of all G-M stars are expected to be part of binary or multiple stellar systems. Therefore, these kinds of systems are worthy of investigation in detail. In particular, we will concentrate on planets in P-Type motion, where the planet orbits around both stars. During the last few years, four such systems (NN Ser, HW Vir, HU Aqr and DP Leo) have been discovered. In our study, we performed dynamical studies for three multi-planetary systems in binaries (NN Ser, HW Vir, HU Aqr), and compared simulated eclipse timing variations (ETV) to current observational data.

The stability of planetary motion in the binary system α Cen A–B is studied. Lyapunov spectra of the motion of the system with a single massive planet are computed on a fine grid of the initial data, and, by means of statistical analysis of the obtained data arrays, chaotic domains are identified in the “pericentric distance — eccentricity” initial data space for the planetary orbit. Association with the initial data domains for the orbits exhibiting close encounters with central stars and for the orbits exhibiting long-term escape is investigated.

There is broad agreement that the stars which explode as Type Ia supernovae are white dwarfs. They have accreted material in a binary system until they are near the Chandrasekhar mass and detonate/deflagrate. The two main scenarios for this accretion process are merging with a companion white dwarf (double degenerate scenario), or accretion from a main-sequence to red giant donor (single degenerate scenario). The donor star survives post-explosion and would provide substantial evidence for the single degenerate scenario, if found. Our team is analyzing stars in close proximity to Galactic Type Ia remnants to find surviving donor stars. In my talk I will introduce the different progenitor systems and the expected state for a donor star today. I will outline our search using high resolution spectroscopy and will present updated results.