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Coastal flood is often a problem on the north coast of Java. The main factor that causes it is sea level rise which is triggered by several main constituents. The main triggering constituent that has long been known is the gravitational constituent of the moon and the sun. Another main trigger constituent is high waves at the sea, especially due to bad weather. Djamaluddin et al. (2022) have found empirical evidence of astronomical constituents in increasing sea level peaks in Jakarta and Surabaya from analyses of long-term tidal data from 1984 to 2004. The most dominant astronomical parameters are the combination of moon phases at new-full moon or lunar declination, the proximity of the moon to the earth (perigee), and the sun's declination. Jakarta and Surabaya tide gauge stations are considered to represent general conditions on the north coast of Java, although there are differences in tidal characteristics. The tides in Jakarta generally have a diurnal pattern which is affected by the constituent of the moon's declination, while the tides in Surabaya generally have a semi-diurnal pattern which is affected by the constituent of the new-full moon. On the basis of this empirical evidence, a simple model of the effect of astronomical parameters on sea level rise was made. The model is prepared by periodicity superposition of declination or moon phase, lunar perigee, and sun declination. The absolute value of the minimum cycle of the declination of the moon, moon phase, and solar declination is used, because the peak of sea level rise also occurs during the minimum phase of the moon, as well as the minimum (most southern) declination of moon and sun. This simple model is quite well suited to sea level peaks in the period 1984 - 2004. Most of the coastal flood events also correspond to the peaks of variation in the model. Thus, the developed simple model can be used as a prediction of the potential coastal flooding on the north coast of Java. Of course, other triggering factors of high waves, that cannot be predicted in advance, need to be watched out for, because they act as a strengthening factor to the potential coastal flooding. [ABSTRACT FROM AUTHOR]

The fixed-time heliocentric trajectory optimization problem is considered for planar solar sail with minimum area. Necessary optimality conditions are derived, a numerical method for solving the problem is developed, and numerical examples of optimal trajectories to Mars, Venus and Mercury are presented. The dependences of the minimum area of the solar sail from the date of departure from the Earth, the time of flight and the departing hyperbolic excess of velocity are analyzed. In particular, for the rendezvous problem (approaching a target planet with zero relative velocity) with zero departing hyperbolic excess of velocity for a flight duration of 1200 days it was found that the minimum area-to-mass ratio should be about 12 m2/kg for trajectory to Venus, 23.5 m2/kg for the trajectory to Mercury and 25 m2/kg for trajectory to Mars. [ABSTRACT FROM AUTHOR]

Fritz Zwicky's hypothesis, according to which the cosmological redshift is due to galactic light losing energy to intergalactic media, without need of Universe expansion, seems to have been recently confirmed by recent mathematical, theoretical and experimental studies via measurements on Earth. But the return to a static universe would imply the inevitable prediction that the universe should collapse due to gravitational attractions among galaxies. In this paper, we present apparently for the first time a cosmological model in which the stability of the universe is achieved under the condition of admitting an equal number of matter and antimatter galaxies (as they are hypothesized in Isodual Theory of Antimatter) at such a large mutual distance for which gravitational interactions are neglectable. [ABSTRACT FROM AUTHOR]

Significant progress has been made in our understanding of the power of polarization maps in the submillimeter and millimeter in the past decade. This is made more remarkable by the dearth of new polarimetric facilities over the past 10 years and decommissioning of several long-standing instruments. In particular, we discuss recent work to establish the validity of the previously measured polarization spectrum in the submillimeter, and the enhanced analysis techniques presented in recent years for the interpretation of polarization position angle data without the need for models of the ordered field geometry. [ABSTRACT FROM AUTHOR]

We present the evolution of the radio emission from the 2.8-s pulsar of the double pulsar system PSR J0737-3039A/B. We describe the changes in the pulse profile and flux density over five years of observations, culminating in the B pulsar's radio disappearance in 2008 March. Over this time, the flux density decreased by 0.177 mJy yr-1 at the brightest orbital phases and the pulse profile evolved from a single to a double peak. Relativistic spin precession, coupled with an elliptical beam, can model the pulse profile evolution well and the reappearance is expected to happen in ∼2035 with the same part of the beam or in ∼2014 if we assume a symmetric beam shape. [ABSTRACT FROM AUTHOR]

We have computed the fate of exoplanet companions around main sequence stars to explore the frequency of planet ingestion by their host stars during the red giant branch evolution. Using published properties of exoplanetary systems combined with stellar evolution models and Zahn's theory of tidal friction, we modeled the tidal decay of the planets' orbits as their host stars evolve. Most planets currently orbiting within 2 AU of their star are expected to be ingested by the end of their stars' red giant branch ascent. Our models confirm that many transiting planets are sufficiently close to their parent star that they will be accreted during the main sequence lifetime of the star. We also find that planet accretion may play an important role in explaining the mysterious red giant rapid rotators, although appropriate planetary systems do not seem to be plentiful enough to account for all such rapid rotators. We compare our modeled rapid rotators and surviving planetary systems to their real-life counterparts and discuss the implications of this work to the broader field of exoplanets. [ABSTRACT FROM AUTHOR]

In the last decades, a lot of progress was made in spectral analysis. The quality (e.g. resolution, S/N ratio) of observed spectra has improved much and several model-atmosphere codes were developed. One of these is the 'Tübingen NLTE Model-Atmosphere Package' (TMAP), that is a highly developed program for the calculation of model atmospheres of hot, compact objects. In the framework of the German Astrophysical Virtual Observatory (GAVO), theoretical spectral energy distributions (SEDs) can be downloaded via TheoSSA. In a pilot phase, TheoSSA is based on TMAP model atmospheres. We present the current state of this VO service. [ABSTRACT FROM AUTHOR]

I report here on the current effort to provide the next generation of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS). The new catalog is based on SDSS Data Release (DR) 7 data and includes new model fits applied to both the newly-identified white dwarf stars as well as those previously found in our earlier DR1 and DR4 catalog white dwarf stars. Thew new catalog includes nearly 20,000 white dwarfs of various types and represents the results of both automated and human inspection of over 40,000 candidates. The full catalog and author list is expected to be complete in late 2010. [ABSTRACT FROM AUTHOR]

We briefly present here our first results of our ongoing efforts to produce large grids of NLTE synthetic spectra for hot subdwarf stars and pure helium accretion disks. [ABSTRACT FROM AUTHOR]

Observations of dusty discs around white dwarfs suggest a link between white dwarfs and evolved planetary systems. The population of debris discs on the main sequence is well constrained. In this work we present models that evolve this population through to the white dwarf phase. Evolved main sequence debris discs are hard to detect around whtie dwarfs. The best chances are for hot young white dwarfs, fitting nicely with the observations for the example the infrared excess at the centre of the helix [1] and 9 other planetary nebula (Chu& Bilikova-this volume), although our baseline models do not predict such a high rate of detectable discs. Evolved main sequence debris discs potentially provide the reservoir of material required to replenish the hot dusty discs obsevred within the tidal radius. [ABSTRACT FROM AUTHOR]

We present an overview of recent work that focuses on understanding the radiative feedback processes that are potentially important during Population III star formation. Specifically, we examine the effect of the Lyman-Werner (photodissociating) background on the early stages of primordial star formation, which serves to delay the onset of star formation in a given halo but never suppresses it entirely. We also examine the effect that both photodissociating and ionizing radiation in I-fronts from nearby stellar systems have on the formation of primordial protostellar clouds. Depending on the strength of the incoming radiation field and the central density of the halos, Pop III star formation can be suppressed, unaffected, or even enhanced. Understanding these and other effects is crucial to modeling Population III star formation and to building the earliest generations of galaxies in the Universe. [ABSTRACT FROM AUTHOR]

The search for the most distant galaxies is bursting with new discoveries and theoretical excitement. The topic is not only plainly interesting in itself, it also has profound implications for the study of cosmic reionization, the intergalactic medium, and cosmic enrichment. Such observations also provide a stringent benchmark for cosmological models. The following is a very concise attempt to review the present status of the field and its challenges from a theoretical perspective. [ABSTRACT FROM AUTHOR]

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z = 6. These earliest SMBHs may arise by the combination of Eddington-limited growth and mergers of stellar-mass seed BHs left behind by the first generation of metal-free stars, or by the rapid direct collapse of gas in rare special environments where the gas can avoid fragmenting into stars. In this contribution, I review these two competing scenarios. I also briefly mention some more exotic ideas and how the different models may be distinguished in the future by LISA and other instruments. [ABSTRACT FROM AUTHOR]

Observations of the explosions of Population III (Pop III) stars have the potential to teach us much about the formation and evolution of these zero-metallicity objects. To realize this potential, we must tie observed emission to an explosion model, which requires accurate light curve and spectra calculations. Here, we discuss many of the pitfalls and problems involved in such models, presenting some preliminary results from radiation-hydrodynamics simulations. [ABSTRACT FROM AUTHOR]

For the initial mass range 140

The standard cosmological model predicts that the first cosmological objects are formed when the age of the universe is a few hundred million years. Recent theoretical studies and numerical simulations consistently suggest that the first objects are very massive primordial stars. We introduce the key physics and explain why the first stars are thought to be massive, rather than to be low-mass stars. The state-of-the-art simulations include all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to very high 'stellar' densities. Evolutionary calculations of the primordial stars suggest the formation of massive blackholes in the early universe. Finally, we show the results from high-resolution simulations of star formation in a low-metallicity gas. Vigorous fragmentation is triggered in a star-forming gas cloud at a metallicity of as low as Z = 10-5Z⊙. [ABSTRACT FROM AUTHOR]

We discuss the prospects for probing the ancient universe through high-energy gamma-ray from GRBs. UV intergalactic radiation fields (IRFs) during cosmic reionization can be probed through multi-GeV spectral absorption features due to photon-photon pair production. Using different IRF models including Pop III stars and consistent with existing observations, we show that spectral cutoffs are expected in the range of 10-100 GeV at z>6. This may be observable by Fermi or future arrays such as CTA, AGIS or 5@5, providing unique and critical information on the evolving IRF, the integrated cosmic star formation rate, and possibly also the escape fraction of UV photons from galaxies. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed to explain them. [ABSTRACT FROM AUTHOR]

I review the development of the relativistic blast-wave model for GRB afterglows, in which the delayed emission is synchrotron and, possibly, inverse Compton from electrons accelerated by the forward shock that energizes the burst ambient medium or the reverse shock that crosses the incoming ejecta. This model is tested and its features constrained using afterglow observations at radio, optical, X-ray, and GeV photon energies. Modeling of the afterglow broadband emission allows the determination of the outflow's physical parameters, such as collimation and energetics, circum-burst medium density, its radial stratification, and of forward-shock microphysical parameters. The slowly-decaying radio afterglows (weeks after trigger) and the fast-decaying early optical afterglows (up to 1 ks) provide evidence for a temporary contribution from the reverse-shock. The chromatic X-ray light-curve breaks and the afterglows with well-coupled optical and X-ray light-curves and chromatic breaks suggest the existence of an outflow inner to the blast-wave, which bulk-scatters the forward-shock emission and injects energy into it. [ABSTRACT FROM AUTHOR]

Fermi LAT (Large Area Telescope) and GBM (Gamma ray Burst Monitor) observations of GRBs are briefly reviewed, keeping in mind EGRET expectations. Using γγ constraints on outflow Lorentz factors, leptonic models are pitted against hadronic models, and found to be energetically favored. Interpretation of the Fermi data on GRBs helps establish whether GRBs accelerate cosmic rays, including those reaching ≈1020 eV. [ABSTRACT FROM AUTHOR]

This work describes an elearning sequence for teaching geometry and astronomy in lower secondary school created inside the ITEMS (Improving Teacher Education in Mathematics and Science) project. It is based on results from the astronomy education research about studentsSˇ difficulties in understanding elementary astronomical observations and models. The sequence consists of a set of computer animations embedded in an elearning environment aimed at supporting students in learning about astronomy ideas that require the use of geometrical concepts and visual-spatial reasoning. [ABSTRACT FROM AUTHOR]

The bump, a manifestation of a shock wave on the descending branch or around minimum, is a very remarkable feature of certain monoperiodic RR Lyrae stars. Excellent theoretical identification, as one of the three shock waves, is given by Fokin et al. [5]. The CoRoT Space telescope supports us with incredibly high precision datasets. They allow us to carry out investigations that have never been possible before. Using a 152-day long CoRoT dataset we are able to divide it not only into shorter subsets (check for short-term variability) but into segments according to the remarkable features of the light curve. EN2_STAR_MON_0101370131 is a monoperiodic, non-Blazhko CoRoT RR Lyrae star of the first long run with a very definite bump on the lower part of the descending branch. The light curve is nicely fitted by the pulsation period and its 33 harmonics. The harmonics are highly needed to describe the descending branch. A definite question was addressed to the dataset: can we connect certain harmonics to the special features of the light curve? Our result shows that the 4th and 7th harmonics have close connection to the bump. Our observational results are compared to the results of the theoretical light curve selected from a grid of RR Lyrae models. Investigation of a radial dependence of the shock waves’ characteristic timescale needs a theoretical model with properly zoned outer layers. [ABSTRACT FROM AUTHOR]

We review the current state of Cepheid modeling and discuss its dominant deficiency, namely the use of time dependent mixing length. Notwithstanding, Cepheid modeling has achieved some excellent successes, and we mention some of the most recent ones. Discrepancies between observations and modeling appear not so much in the gross properties of single mode Cepheids, but rather when more subtle nonlinear effects are important, such as in double mode or even triple mode pulsations. Finally we discuss what we consider the most important challenges for the next decade. These are, first, the multidimensional modeling of convection in a pulsating Cepheid environment, and second, the nonlinear modeling of the nonradial pulsations, and, possibly relatedly, of the Blazhko like phenomenon, both of which recently been observed in Cepheids. [ABSTRACT FROM AUTHOR]

Solar models calibrated with the new element abundance mixture of Asplund et al. published in 2005 no longer produce good agreement with the sound speed, convection zone depth, and convection zone helium abundance inferred from solar oscillation data. Attempts to modify the input physics of the standard model, for example, by including enhanced diffusion, increased opacities, accretion, convective overshoot, or gravity waves have not restored the good agreement attained with the prior abundances. Here we present new models including early mass loss via a stronger solar wind. Early mass loss has been investigated prior to the solar abundance problem to deplete lithium and resolve the ‘faint early sun problem’. We find that mass loss modifies the core structure and deepens the convection zone, and so improves agreement with oscillation data using the new abundances; however the amount of mass loss must be small to avoid destroying all of the surface lithium, and agreement is not fully restored. We also considered the prospects for increasing solar interior opacities. In order to increase mixture opacities by the 30% required to mitigate the abundance problem, the opacities of individual elements (e.g., O, N, C, and Fe) must be revised by a factor of two to three for solar interior conditions; we are investigating the possibility of broader calculated line wings for bound-bound transitions at the relevant temperatures to enhance opacity. We find that including all of the elements in the AGS05 opacity mixture (through uranium at atomic number Z = 92) instead of only the 17 elements in the OPAL opacity mixture increases opacities by a negligible 0.2%. [ABSTRACT FROM AUTHOR]

Solar observations show that the spectra of turbulent convection and oscillations significantly change in magnetic regions, resulting in interesting phenomena, such as high-frequency “acoustic halos” around active regions. In addition, recent observations from SOHO/MDI revealed significant changes of the wave properties in inclined magnetic field regions of sunspots, which affect helioseismic inferences. We use realistic 3D radiative MHD numerical simulations to investigate properties of solar convection and excitation and propagation of oscillations in magnetic regions. A new feature of these simulations is implementation of a dynamic sub-grid turbulence model, which allows more accurate description of turbulent dissipation and wave excitation. We present the simulation results for a wide range of the field strength and inclination in the top 6 Mm layer of the convection zone. The results show interesting and unexpected effects in the dynamics and large-scale organization of the magnetoconvection (including traveling waves and shearing flows), and also changes in the excitation properties and spectrum of oscillations, suggesting an explanation of the acoustic “halos” observed above the acoustic cut-off frequency. [ABSTRACT FROM AUTHOR]

We calculate an extensive adiabatic model grid for pulsating white dwarfs with H dominated atmospheres, the ZZ Ceti stars. We developed a new approach for asteroseismology, using the relative observed amplitudes as weights, and compared the computed modes with the observed ones for the class of ZZ Ceti stars. We measure the H layer mass for 83 stars and found an average of MH/M* = 10-6.3, which is thinner than the predicted value of MH/M* = 10-4. Our results indicate that the stars lose more mass during their evolution than previously expected. [ABSTRACT FROM AUTHOR]

Double-mode Cepheid behaviour may arise either from non-resonant or resonant mode interaction. Inclusion of turbulent convection into pulsation codes by Kolláth et al. led to stable double-mode F+1O Cepheid pulsation [1]. However, our recent computations indicate that these models resulted from an incorrect neglect of negative buoyancy effects [2]. Once these effects are taken into account, only some resonant double-mode models could be found. These models do not solve the puzzle of double-mode phenomenon, as they are restricted to narrow parameter ranges. For the majority of observed double-mode Cepheids, the non-resonant mechanism has to be operational. [ABSTRACT FROM AUTHOR]

I discuss the synergies between Simbol-X and three among the major astronomical facilities that, in the next decade, will be operative in the infrared-millimeter spectral range, namely JWST, Herschel and ALMA. I first provide a brief overview of the main features and observing capabilities offered by these facilities. Then I will discuss a few research fields (mostly extragalactic) that will geatly benefit of the joint exploitation of Simbol-X and these IR-mm observatories. [ABSTRACT FROM AUTHOR]

AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the simulations with recent observations on these sources by INTEGRAL, Swift and Suzaku. Constraining reflection models for AGN with Simbol-X will help us to get a clear view of the processes and geometry near to the central engine in AGN, and will give insight to which sources are responsible for the Cosmic X-ray background at energies >20 keV. [ABSTRACT FROM AUTHOR]

The Simbol-X background simulation group is working towards a simulation based background and mass model which can be used before and during the mission. Using the Geant4 toolkit, a Monte-Carlo code to simulate the detector background of the Simbol-X focal plane instrument has been developed with the aim to optimize the design of the instrument. Achieving an overall low instrument background has direct impact on the sensitivity of Simbol-X and thus will be crucial for the success of the mission. We present results of recent simulation studies concerning the shielding of the detectors with respect to the diffuse cosmic hard X-ray background and to the cosmic-ray proton induced background. Besides estimates of the level and spectral shape of the remaining background expected in the low and high energy detector, also anti-coincidence rates and resulting detector dead time predictions are discussed. [ABSTRACT FROM AUTHOR]

After a brief discussion on the problems in constructing inflation models in supergravity, we shall discuss for illustration a concrete example where an inflaton field is identified as a right-handed sneutrino in a D-term dominated potential. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We study a phenomenological model for the continuum emission of Seyfert galaxies. In this quasi-spherical accretion scenario, the central X-ray source is constituted by a hot spherical plasma region surrounded by spherically distributed cold dense clouds. The cold material is radiatively coupled with the hot thermal plasma. Assuming energy balance, we compute the hard X-ray spectral slope ⌈ and reflection amplitude R. This simple model enables us to reproduce both the range of observed hard X-ray spectral slopes, and reflection amplitude R. It also predicts a correlation between R and ⌈ which is very close to what is observed. Wide changes in the cloud covering fraction from source to source would be reponsible for most of the observed spectral variations. Moreover, if some internal dissipation process is active in the cold clouds, obscuration effects may provide a simple explanation for the observed distributions of reflection amplitudes, spectral slopes, and UV to X-ray flux ratios. [ABSTRACT FROM AUTHOR]

Using a one-zone model, we study the gravitational fragmentation of baryonic cold streams flowing into a typical first galaxy at high redshift to predict the expected fragmentation mass scale and thus a characteristic mass of the first population of stars to form by shock fragmentation. In this simplified model, we bypass the resolution barrier in simulations of progalaxy formation and directly probe the fragmentation mass scale of accreting gas streams. We find the fragmentation mass scale to be most strongly dependent on the metallicity of the gas and the background Lyman-Werner radiation field, and that either a large cluster of solar mass fragments or one large (105 M⊙) fragment forms. [ABSTRACT FROM AUTHOR]

A long GRB is thought to occur when a massive star ends its life and thus it is expected to be accompanied by a type Ic supernova (SN) which also results from a massive star. Several nearby long GRBs are observed with type Ic SNe. However, some nearby long GRBs are observed without SNe, even though they are close enough to be able to observe the accompanied SNe (e.g., GRB060614). Within our current picture of long GRBs, long GRBs should be accompanied by SNe and these long GRBs without SNe are one of the challenges for the current theory of long GRBs. One possible reason is that the accompanied SNe were so faint that we just missed them. For example, SN 2008ha was only as bright as ∼-14 mag in the R band at maximum brightness. The explosion energy, ejecta mass, and 56Ni mass of SN 2008ha are estimated as about 1048 erg, 0.1 M⊙, and 0.003 M⊙, respectively. If such a SN is accompanied by long GRBs, we might miss it. We performed numerical calculations of hydrodynamics and radiation transport and confirmed that SN 2008ha could have been a type Ic supernova and originated from a core-collapse SN with a significant amount of fallback. This demonstrates that some type Ic SNe like SN 2008ha could be very faint because of fallback. Our results suggest that long GRBs without SNe could have been accompanied by such faint SNe with fallback and we could have just missed the accompanied SNe and the current picture of long GRBs would be consistent with long GRBs without SNe. [ABSTRACT FROM AUTHOR]

The huge optical brightness of GRB 080319B (the 'Naked Eye Burst') makes this event really challenging for models of the prompt GRB emission. In the framework of the internal shock model, we investigate a scenario where the dominant radiative process is synchrotron emission and the high optical flux is due to the dynamical properties of the relativistic outflow : if the initial Lorentz factor distribution in the jet is highly variable, many internal shocks will form within the outflow at various radii. The most violent shocks will produce the main gamma-ray component while the less violent ones will contribute at lower energy, including the optical range. [ABSTRACT FROM AUTHOR]

We present one of the most intriguing results obtained with an updated catalog of 113 early time (i.e. tpk<=1000 s) and 36 late time (i.e. tpk>=1000 s) X-ray flares detected by Swift in the afterglows of Gamma-Ray Bursts (GRB): the evolution of the width of the flares with time. This result, together with other properties investigated on early and late time flares and bright flares, provides a clear observational property that every model aiming at explaining the GRB emission has to face. [ABSTRACT FROM AUTHOR]

We present the observations of the afterglow of gamma-ray burst GRB 090102. Optical data taken by the TAROT, REM, GROND, together with publicly available data from Palomar, IAC and NOT telescopes, and X-ray data taken by the XRT instrument on board the Swift spacecraft were used. This event features an unusual light curve. In X-rays, it presents a constant decrease with no hint of temporal break from 0.005 to 6 days after the burst. In the optical, the light curve presents a flattening after 1 ks. Before this break, the optical light curve is steeper than that of the X-ray. In the optical, no further break is observed up to 10 days after the burst. We failed to explain these observations in light of the standard fireball model. Several other models, including the cannonball model were investigated. The explanation of the broad band data by any model requires some fine tuning when taking into account both optical and X-ray bands. [ABSTRACT FROM AUTHOR]

Two-jet models are introduced to explain the complex time profiles and diversities of early afterglows in the Swift era. Testing these afterglow models is important because it relates not only to the afterglow emission mechanism, but also to the activity of the central engines of gamma-ray bursts (GRBs). In this paper, we suggest a new method of testing two-jet models by using orphan afterglows of GRBs. If afterglows are actually composed of two jets, we can observe two peaks in the orphan afterglows in the optical band. Typically, the first peak appears on 104-105s and the second peak on 105-106s. Therefore, first we observe the orphan afterglow in the X-ray band, and if we follow up the afterglow in the optical band, we can observe two peaks. [ABSTRACT FROM AUTHOR]

We suggest that white dwarf pulsars can compete with neutron star pulsars for producing the excesses of cosmic ray positrons and electrons (e±) observed by the PAMELA, ATIC/PPB-BETS, Fermi and HESS experiments. A double degenerate white dwarf binary mergers into a white dwarf pulsar with rotational energy (∼1050 erg) comparable to a neutron star pulsar. The birth rate (∼1/100 yr) is also similar, providing the right energy budget. Applying the neutron star theory, we show that the white dwarf pulsars can produce e±, up to ∼10 TeV for high magnetic fields (>108 G). In contrast to the neutron star case, the adiabatic energy losses of e± are negligible since their injection continues after the nebula expansion. The long activity also enhances the nearby sources, potentially dominating the quickly cooled e± above TeV energy, detectable by the future CALET experiment. [ABSTRACT FROM AUTHOR]

We investigate the impact that the upper cutoff of the electron distribution has on the multiwavelength GRB afterglow spectra and on the corresponding X-ray light curves. We show under which conditions X-ray light curves with a plateau phase can be produced in this picture. [ABSTRACT FROM AUTHOR]

The present work focuses on the discussion of the λ Bootis nature of the multiperiodic δ Scuti star HD 192640 (29 Cyg), through a comprehensive asteroseismic modelling. Some of the most recent asteroseismic tools are used to check whether the observed low metallicity is internal, i.e., intrinsic, present throughout the star, or due to superficial processes as accretion, diffusive settling, radiative levitation, mass loss, etc. The modelling method includes: 1) effects of rotation on equilibrium models, on the adiabatic oscillation spectrum, and its influence in multicolour observables, 2) non-adiabatic stability of radial and non-radial modes, 3) inclusion of the atmosphere-pulsation interaction for a more accurate multicolour mode identification. The analysis performed reveals that the models fulfilling all the constraints are those in the middle of the Main Sequence, with sub-solar metallicity, except for some other unlikely possibilities. Therefore this study does not support the idea of the λ Bootis stars being ZAMS or Pre-MS stars interacting with their primordial cloud of gas and dust, but suggests the explanation of their nature as sub-metallic MS objects. Nevertheless, more accurate multicolour photometric observations are required for a more conclusive study using the procedure presented here, since the observational errors are too large for a definitive rejection of any of the possible explanations. [ABSTRACT FROM AUTHOR]

With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology. [ABSTRACT FROM AUTHOR]

Data on multimode Cepheids from OGLE-III catalog of the LMC Cepheids are confronted with results from model calculations. Models whose radial mode periods are consistent with observation are not always in agreement with published evolutionary models. Nonradial mode interpretation is considered for the cases of unusual period ratios. The greatest challenge for stellar pulsation theory is explanation of double-mode pulsators with period ratios near 0.6. [ABSTRACT FROM AUTHOR]

We present here our recent results obtained using the mid-infrared imaging instrument VISIR at the ESO VLT. Using a combination of short exposures and “lucky imaging,” we obtained diffraction limited (for an 8 m telescope) images of Cepheids. We detected circumstellar envelopes (CSE) both photometrically and spatially, at a fraction of an arcsecond scale. These CSE, most probably due to mass loss, represent a significant bias to distance determination using Baade-Wesselink methods and using surface brightness of interferometric method. This observational study is part of multi instruments/technics effort we are carrying over to detect and characterize CSE. [ABSTRACT FROM AUTHOR]

Based on X-ray spectra and studies of the long-term correlated behavior between radio and soft X-ray, we present a detailed evolution of Cyg X-3 through its radio and X-ray states. We comment on the nature of the hard X-ray tail and possible Simbol X contribution in constraining the models. [ABSTRACT FROM AUTHOR]