We successfully obtained the first optical spectra of the faint light echoes around Cassiopeia A and Tycho Brahe's supernova remnants (SNRs) with FOCAS and the Subaru Telescope. We conclude that Cas A and Tycho's SN 1572 belong to the Type IIb and normal Type Ia supernovae, respectively. Light echo spectra are important in order to obtain further insight into the supernova explosion mechanism of Tycho's SN 1572: how the Type Ia explosion actually proceeds, and whether accretion occurs from a companion or by the merging of two white dwarfs. The proximity of the SN 1572 remnant has allowed detailed studies, such as the possible identification of the binary companion, and provides a unique opportunity to test theories of the explosion mechanism and the nature of the progenitor. Future light-echo spectra, obtained in different spatial directions of SN 1572, will enable to construct a three-dimensional spectroscopic view of the explosion.

We started a systematic search for periodic variable-star candidates in the EROS-2 database in the context of preparatory work for the Gaia satellite mission. The goal is to evaluate different classification tools and strategies, and to identify a large sample of variable candidates. In this paper we present the results of an assessment study of a three-step identification and classification process. In the study we took a sample of about 80,000 stars from one of the LMC EROS fields.

We investigate the propagation of accretion-powered jets in various types of progenitor candidates of GRBs. We perform two dimensional axisymmetric simulations of relativistic hydrodynamics taking into account both the envelope collapse and the jet propagation. In our simulations, the accretion rate is estimated by the mass flux going through the inner boundary, and the jet is injected with a constant accretion-to-jet conversion efficiency η. By varying the efficiency η and opening angle θop for more than 30 models, we find that the jet can make a relativistic breakout from all types of progenitors for GRBs if a simple condition η ≳ 10−3 (θop/20°)2 is satisfied, that is consistent with analytical estimates, otherwise no explosion or some failed spherical explosions occur.

We discuss the 3D morphology, ionization structure, and kinematics of NGC 2392, the “Eskimo,” based on new and archival HST imagery and new long-slit echelle spectroscopy. High spatial resolution ionization maps of the nebula were made from HST WFPC2 imagery and compared with their velocity structure in various emission lines from echelle spectra taken with the 4m telescope at Kitt Peak. The imagery and spectra were then compared to map the kinematics of the nebula in several emission lines and decode the 3-dimensional morphology and ionization structure of the nebula, including that of C+2 from C III] 1909 Å for the first time.

We have investigated the revival of a shock wave by nuclear burning reactions at the central region of core-collapse supernovae. For this purpose, we performed hydrodynamic simulations of core collapse and bounce for 15 M⊙ progenitor model, using ZEUS-MP code in axi-symmetric coordinates. Our numerical code is equipped with a simple nuclear reaction network including 13 α nuclei form 4He to 56Ni, and accounting for energy feedback from nuclear reactions as well as neutrino heating and cooling. We found that the energy released by nuclear reactions is significantly helpful in accelerating shock waves and is able to produce energetic explosion even if the input neutrino luminosity is low.

Even though attenuation by dust strongly attenuates and reddens the UV/optical spectral energy distributions of spiral galaxies, quantifying these effects is challenging, particularly when, as is most often the case, infrared measurements of the absorbed energy are not available. We have initiated a study to model the dependence on inclination of the attenuation of light from galaxies measured in the Galaxy and Mass Assembly (GAMA) survey. We present preliminary results using SDSS galaxies in the phase-I GAMA catalogue, comparing observed attenuation-inclination relations with the predictions of the radiation transfer model of Popescu et al. (2011) to derive a statistical measurement of the mean face-on B-band optical depth of disks τfB in a sample of spiral galaxies complete to the SDSS spectroscopic r-band limit of 17.8 mag.

We have used three independent methods to determine an accurate and precise geometric center of SNR 0509-67.5, at RA=05:09:31.208, DEC=−67:31:17.48 (J2000). This supernova, which occurred approximately 400 years ago in the Large Magellanic Cloud, was confirmed to be a Type Ia by Rest et al. (2005), Rest et al. (2008) based on spectra of a light echo from the eruption. If this supernova had a single-degenerate progenitor system, we would see the “leftover” companion star within a certain distance of the remnant's center. Accounting for an offset due to enhanced ISM in the west-southwest quadrant of the remnant, we find the eruption position to be at RA=05:09:30.976, DEC=−67:31:17.90; the error circle which should contain any possible ex-companion star has a radius of 1.60″ for 99.73% (3-sigma) containment. This accounts for the proper motion of the stars, the possibility of kicks from the supernova, and asymmetries in the explosion and remnant expansion. We find no possible ex-companion stars within this ellipse, to a limiting magnitude of V=26.9: there are no red giants, which precludes symbiotic progenitors, no subgiants, which when combined with the lack of red giants precludes recurrent nova progenitors, and no main sequence stars with mass greater than 1.16 solar masses (V brighter than 22.7 mag), which precludes persistent supersoft X-ray source progenitors. Indeed, all published SD models are eliminated, so we conclude that this particular Type Ia supernova had a double-degenerate progenitor.

We have undertaken a near-infrared spectral survey of stars associated with compact mid-IR shells recently revealed by the MIPSGAL (24 μm) and GLIMPSE (8 μm) Spitzer surveys, whose morphologies are typical of circumstellar shells produced by massive evolved stars. Through spectral similarity with known Luminous Blue Variable (LBV) and Wolf-Rayet (WR) stars, a large population of candidate LBVs (cLBVs) and a smaller number of new WR stars are being discovered. This significantly increases the Galactic cLBV population and confirms that nebulae are inherent to most (if not all) objects of this class.

The standard model of Active Galactic Nuclei (AGNs) predicts that Type 2 AGNs and Type 1 AGNs only differ in the orientation of a dust torus, which does or does not allow one to observe the central region. If the model is correct, the time-scales and the amplitudes of observed temporal variations should be different between obscured and unobscured objects. In order to test this hypothesis, we started a multi-wavelength (BRIJKs) monitoring campaign of a sample of quasars of both types. Here we present the data and preliminary results of that project.

Some supernovae and gamma-ray bursts are thought to accompany a black hole formation. In the process of a black hole formation, a central core becomes hot and dense enough for hyperons and quarks to appear. In this study, we perform neutrino-radiation hydrodynamical simulations of a stellar core collapse and black hole formation taking into account such exotic components. In our computation, general relativity is fully considered under spherical symmetry. As a result, we find that the additional degrees of freedom soften the equation of state of matter and promote the black hole formation. Furthermore, their effects are detectable as a neutrino signal. We believe that the properties of hot and dense matter at extreme conditions are essential for the studies on the astrophysical black hole formation. This study will be hopefully a first step toward a physics of the central engine of gamma-ray bursts.

We present an overview and current results of an ongoing optical/NIR monitoring of seven gravitationally-lensed quasars (GLQs) with the 2-m Liverpool Robotic Telescope. The photometric data from the first seven years (2005–2011) of this programme are leading to high-quality light curves, which in turn are being used as key tools for different standard and novel studies. While brightness records of non-lensed distant quasars may contain unrecognized extrinsic variations, one can disentangle intrinsic from extrinsic signals in certain GLQs. Thus, some GLQs in our sample allow us to assess their extrinsic and intrinsic variations; we then discuss the origin of both kinds of fluctuations. We also demonstrate the usefulness of GLQ time-domain data for obtaining successful reverberation maps of the inner regions of accretion disks around distant supermassive black holes, and for estimating the redshifts of distant lensing galaxies.

With the launch of NASA's Kepler mission, stellar astrophysics in general, and the eclipsing binary star field in particular, has witnessed a surge in data quality, interpretation possibilities, and the ability to confront theoretical predictions with observations. The unprecedented data accuracy and an essentially uninterrupted observing mode of over 2000 eclipsing binaries is revolutionizing the field. Amidst all this excitement, we came to realize that our best models to describe the physical and geometric properties of binaries are not good enough. Systematic errors are evident in a large range of binary light curves, and the residuals are anything but Gaussian. This is crucial because it limits us in the precision of the attained parameters. Since eclipsing binary stars are prime targets for determining the fundamental properties of stars, including their ages and distances, the penalty for this loss of accuracy affects other areas of astrophysics as well. Here, we propose to substantially revamp our current models by applying the lessons learned while reducing, modeling, and analyzing Kepler data.

This symposium was focused on the hunt for the progenitors of Type Ia supernovae (SNe Ia). Is there a main channel for the production of SNe Ia? If so, are these elusive progenitors single degenerate or double degenerate systems? Although most participants seemed to favor the single degenerate channel, there was no general agreement on the type of binary system at play. An observational puzzle that was highlighted was the apparent paucity of supersoft sources in our Galaxy and also in external galaxies. The single degenerate channel (and as it was pointed out, quite possibly also the double degenerate channel) requires the binary system to pass through a phase of steady nuclear burning. However, the observed number of supersoft sources falls short by a factor of up to 100 in explaining the estimated birth rates of SNe Ia. Thus, are these supersoft sources somehow hidden away and radiating at different wavelengths, or are we missing some important pieces of this puzzle that may lead to the elimination of a certain class of progenitor? Another unanswered question concerns the dependence of SNe Ia luminosities on the age of their host galaxy. Several hypotheses were put forward, but none was singled out as the most likely explanation.

It is fair to say that at the end of the symposium the definitive answer to the vexed progenitor question remained well and truly wide open.

We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.

We have used deep optical, near-IR, and IR observations from VLT, Spitzer, Herschel, and LABOCA in strong lensing clusters to study distant galaxies. In searches for optical-dropout galaxies (i.e. for z ≳ 7 candidates) we have found several galaxies with very unusual SEDs characterised by a strong spectral break, presumably indicative of high-z, although the objects are detected even in the Herschel bands between 160 and 500 μm and at 870 μm. The latter indicates, from simple estimates of the bolometric luminosity and from the IR SED, that these ob jects are most likely at z ~ 2–2.5.

The resulting SEDs imply very high IR/UV ratios, indicative of very large attenuation. Despite this, the large spectral break observed between the optical and near-IR data is difficult to understand with currently know spectral templates from galaxies, EROs, SMGs, and others, both empirical and theoretical ones.

Some theoretical studies on the origin of long gamma-ray bursts (GRBs) using stellar evolution models suggest that a low metallicity environment may be a necessary condition for a GRB to occur. However, recent discoveries of high-metallicity host galaxies of some GRBs cast doubt on the requirement of low-metallicity in GRB occurrence. In this study, we predict the metallicity distribution of GRB host galaxies, assuming empirical formulations of galaxy properties. We take internal dispersion of metallicity within each galaxy into account. Assuming GRBs trace low-metallicity star formation 12+log(O/H) < 8.2, we find that ≳ 10% of GRB host galaxies may have Z > Z⊙, depending on the internal dispersion of metallicity within galaxies.

We present our analysis of the spectra of NGC 7027 taken with the PACS and SPIRE instruments of the Herschel satellite.

Processes that promote the formation of dense cold clouds in the interstellar media of galaxies are reviewed. Those that involve background stellar mass include two-fluid instabilities, spiral density wave shocking, and bar accretion. Young stellar pressures trigger gas accumulation on the periphery of cleared cavities, which often take the form of rings by the time new stars form. Stellar pressures also trigger star formation in bright-rim structures, directly squeezing the pre-existing clumps in nearby clouds and clearing out the lower density gas between them. Observations of these processes are common. How they fit into the empirical star formation laws, which relate the star formation rate primarily to the gas density, is unclear. Most likely, star formation follows directly from the formation of cold dense gas, whatever the origin of that gas. If the average pressure from the weight of the gas layer is large enough to produce a high molecular fraction in the ambient medium, then star formation should follow from a variety of processes that combine and lose their distinctive origins. Pressurized triggering might have more influence on the star formation rate in regions with low average molecular fraction. This implies, for example, that the arm/interarm ratio of star formation efficiency should be higher in the outer regions of galaxies than in the main disks.

Code ROCHE is devoted to modeling multi-dataset observations of close eclipsing binaries such as radial velocities, multi-wavelength light curves, and broadening functions. The code includes circular surface spots, eccentric orbits, asynchronous or/and differential rotation, and third light. The program makes use of synthetic spectra to compute observed UBVRIJHK magnitudes from the surface model and the parallax. The surface grid is derived from a regular icosahedron to secure more-or-less equal (triangular) surface elements with observed intensities computed from synthetic spectra for supplied passband transmission curves. The limb-darkening is automatically interpolated from the tables after each computing step. All proximity effects (tidal deformation, reflection effect, gravity darkening) are taken into account. Integration of synthetic curves is improved by adaptive phase step (important for wide eclipsing systems).

The code is still under development. It is planned to extend its capabilities towards low mass ratios and widely different radii of components to facilitate modeling of extrasolar planet transits. Another planned extension of the code will be modeling of spatially-resolved eclipsing binaries using relative visual orbits and/or interferometric visibilities.