Miracle-dz/UniFAR-FTUs huggingface dataset:
X-ray spectrum from gamma Cassiopeiae

The X-ray source gamma Cassiopeiae was observed with the X-ray astronomy satellite Tenma. A strong iron line was observed at 6.8 keV with an intensity of 280 eV equivalent width as is expected from a highly ionized plasma. The strength of the iron line at 6.8 keV and the existence of a thin thermal plasma are in conflict with models that require a neutron star as the X-ray source. From many of the X-ray binaries with a neutron star, only a weak ionized iron line (less than 50 eV at 6.7 keV) or strong reprocessed iron line (6.4 keV) has been observed with Tenma. This Letter suggests the possible existence of a degenerate dwarf as a companion for gamma Cas instead of a neutron star. The lack of luminosity from the white dwarf companion is attributed to a nonspherical mass loss from the primary. 23 references.
Near-infrared Spectral Evolution of the Type Ia Supernova 2014J in the Nebular Phase: Implications for the Progenitor System

As the closest Type Ia supernova in decades, SN 2014J provides a unique opportunity for detailed investigation into observational signatures of the progenitor system, explosion mechanism, and burning product distribution. We present a late-time near-infrared spectral series from Gemini-N at after the explosion. Following the H-band evolution probes the distribution of radioactive iron group elements, the extent of mixing, and the presence of magnetic fields in the expanding ejecta. Comparing the isolated 1.6440 μm [Fe ii] emission line with synthetic models shows consistency with a Chandrasekhar mass white dwarf of undergoing a delayed detonation. The ratio of the flux in the neighboring emission feature to the flux in the feature shows evidence of some limited mixing of stable and radioactive iron group elements in the central regions. Additionally, the evolution of the line shows an intriguing asymmetry. When measuring line width of this feature, the data show an increase in line width not seen in the evolution of the synthetic spectra, corresponding to ≈1000 km s−1, which could be caused by a localized transition to detonation producing asymmetric ionization in the ejecta. Using the difference in width between the different epochs, an asymmetric component in the central regions, corresponding to approximately the inner 2 × 10−4 of white dwarf mass suggests an off-center ignition of the initial explosion and hence of the kinematic center from the chemical center. Several additional models investigated, including a detonation and a merger, have difficulty reproducing the features seen in these spectra.
The Evolution of the Mesoscale Environment of Severe Local Storms: Preliminary Modeling Results

Abstract The development of mesoscale features in numerical model forecasts of the environment of severe local storms is examined for two of the SESAME-1979 cases. The results show that a 10-layer model with a horizontal resolution of about 100 km, simple physics and initialized with essentially synoptic-scale data, is capable of generating and maintaining mesoscale phenomena in the 0–24 h time period. These results indicate that some mesoscale phenomena are predictable for periods of time longer than the lifetime of the mesoscale feature itself. Mesoscale features produced in the forecasts of the 10–11 April and 25–26 April cases include low-level jets, mesoscale convective complexes, upper-level jet streaks, cold and warm frontogenesis, drylines, mountain waves and capping inversions (lids). The development and structure of these phenomena in the model forecast are examined in detail and the interactions among the phenomena are emphasized. The results strongly confirm the conclusions from earlier studie.
Quasinormal modes of black holes: The improved semianalytic approach

We extend the semianalytic technique of Iyer and Will for computing the complex quasinormal frequencies of black holes, $\ensuremath{\omega}$, by constructing the Pad\'e approximants of the (formal) series for ${\ensuremath{\omega}}^{2}$. It is shown that for the (so-far best documented) quasinormal frequencies of the Schwarzschild and Reissner-Nordstr\"om black holes the Pad\'e transforms ${P}_{6}^{6}$ and ${P}_{7}^{6}$ are, within the domain of applicability, always in excellent agreement with the numerical results. We argue that the method may serve as a black box with the ``potential'' $Q(x)$ as an input and the accurate quasinormal modes as the output. The generalizations and modifications of the method are briefly discussed as well as the preliminary results for other classes of black holes.
A Chandra X-ray census of the interacting binaries in old open clusters – NGC 188

We present a new X-ray study of NGC 188, one of the oldest open clusters known in our Galaxy (7 Gyr). Our observation with the Chandra X-ray Observatory is aimed at uncovering the population of close interacting binaries in NGC 188. We detect 84 sources down to a luminosity of LX ≈ 4 × 1029 erg s−1 (0.3–7 keV), of which 73 are within the half-mass radius rh. Of the 60 sources inside rh with more than 5 counts, we estimate that ∼38 are background sources. We detected 55 new sources, and confirmed 29 sources previously detected by ROSAT and/or XMM–Newton. A total of 13 sources detected are cluster members, and 7 of these are new detections: four active binaries, two blue straggler stars (BSSs), and, surprisingly, an apparently single cluster member on the main sequence (CX 33/WOCS 5639). One of the BSSs detected (CX 84/WOCS 5379) is intriguing as its X-ray luminosity cannot be explained by its currently understood configuration as a BSS/white-dwarf binary in an eccentric orbit of ∼120 d. Its X-ray detection, combined with reports of short-period optical variability, suggests the presence of a close binary, which would make this BSS system a hierarchical multiple. We also classify one source as a new cataclysmic-variable candidate; it is identified with a known short-period optical variable, whose membership to NGC 188 is unknown. We have compared the X-ray emissivity of NGC 188 with those of other old Galactic open clusters. Our findings confirm the earlier result that old open clusters have higher X-ray emissivities than other old stellar populations.
On the nature of the intermittent pulsar PSR B1931+24

PSR B1931+24 is the first intermittent radio pulsar discovered to date, characterized by a 0.8-s pulsation, which turns on and off quasi-periodically every similar to 35 d, with a duty cycle of similar to 10 per cent. Here, we present X-ray and optical observations of PSR B1931+24 performed with the Chandra X-ray Observatory and the Isaac Newton Telescope, respectively. Simultaneous monitoring from the Jodrell Bank Observatory showed that this intermittent pulsar was in the radio-on phase during our observations. We do not find any X-ray or optical counterpart to PSR B1931+24, translating into an upper limit of similar to 2 x 10(31) erg s(-1) on the X-ray luminosity, and of g' > 22.6 on the optical magnitude. If the pulsar is isolated, these limits cannot constrain the dim X-ray and optical emission expected for a pulsar of this age (similar to 1.6 Myr). We discuss the possibility that the quasi-periodic intermittent behaviour of PSR B1931+24 is a result of the presence of a low-mass companion star or gaseous planet, tight with the pulsar in an eccentric orbit. In order to constrain the parameters of this putative binary system, we re-analysed the pulsar radio timing residuals. We found that (if indeed hosted in a binary system) PSR B1931+24 should have a very low-mass companion and an orbit of low inclination.
Advanced Algorithms for the Simulation of Gauge Theories with Dynamical Fermionic Degrees of Freedom

The topic of this thesis is the numerical simulation of quantum chromodynamics including dynamical fermions. Two major problems of most simulation algorithms that deal with dynamical fermions are (i) their restriction to only two mass-degenerate quarks, and (ii) their limitation to relatively heavy masses. Realistic simulations of quantum chromodynamics, however, require the inclusion of three light dynamical fermion flavors. It is therefore highly important to develop algorithms which are efficient in this situation. This thesis is focused on the implementation and the application of a novel kind of algorithm which is expected to overcome the limitations of older schemes. This new algorithm is named Multiboson Method. It allows to simulate an arbitrary number of dynamical fermion flavors, which can in principle have different masses. It will be shown that it exhibits better scaling properties for light fermions than other methods. Therefore, it has the potential to become the method of choice. An explorative investigation of the parameter space of quantum chromodynamics with three flavors finishes this work. The results may serve as a starting point for future realistic simulations.
Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant Heliocentric Orbits

Recently, Brown et al. reported the exciting discovery of an ∼800 km radius object, (90377) Sedna, on a distant, eccentric orbit centered at ∼490 AU from the Sun. Here we undertake a first look exploring the feasibility of accreting this object and its possible cohorts between 75 AU (Sedna's perihelion distance) and 500 AU (Sedna's semimajor-axis distance) from the Sun. We find such accretion possible in a small fraction of the age of the solar system, if such objects were initially on nearly circular orbits in this region, and if the solar nebula extended outward to distances far beyond the Kuiper belt. If Sedna did form in situ, it is likely to be accompanied by a cohort of other large bodies in this distant region of the solar system.
Simulating a metallicity-dependent initial mass function: consequences for feedback and chemical abundances

Observational and theoretical arguments increasingly suggest that the initial mass function (IMF) of stars may depend systematically on environment, yet most galaxy formation models to date assume a universal IMF. Here we investigate simulations of the formation of Milky Way analogues run with an empirically derived metallicity-dependent IMF and the moving-mesh code AREPO in order to characterize the associated uncertainties. In particular, we compare a constant Chabrier and a varying metallicity-dependent IMF in cosmological, magneto-hydrodynamical zoom-in simulations of Milky Way-sized halos. We find that the non-linear effects due to IMF variations typically have a limited impact on the morphology and the star formation histories of the formed galaxies. Our results support the view that constraints on stellar-to-halo mass ratios, feedback strength, metallicity evolution and metallicity distributions are in part degenerate with the effects of a non-universal, metallicity-dependent IMF. Interestingly, the empirical relation we use between metallicity and the high mass slope of the IMF does not aid in the quenching process. It actually produces up to a factor of 2-3 more stellar mass if feedback is kept constant. Additionally, the enrichment history and the z = 0 metallicity distribution are significantly affected. In particular, the alpha enhancement pattern shows a steeper dependence on iron abundance in the metallicity-dependent model, in better agreement with observational constraints.
ON THE CLOSURE OF THE SET OF FINITE-ZONE POTENTIALS

A special class of almost-periodic potentials of the one-dimensional Schr? dinger operator is studied. These potentials are limits of finite-zone potentials. In contrast to previous work of the author in which a class of almost-periodic potentials was considered with lacunae in the spectrum having a single limit point at infinity, in this paper the case is studied where the lacunae in the spectrum also have finite limit points. There may be infinitely many of the latter.Figures: 2. Bibliography: 10 titles.
Scaling and fractal formation in persistence

The spatial distribution of unvisited/persistent sites in 1D A +A O model is studied numerically. Over length scales smaller than a cut-off (t )~tz , the set of unvisited sites is found to be a fractal. The fractal dimension df , dynamical exponent z and persistence exponent are related through z (1-df ) = . The observed values of df and z are found to be sensitive to the initial density of particles. We argue that this may be due to the existence of two competing length scales, and discuss the possibility of a crossover at late times.
A Widespread, Clumpy Starburst in the Isolated Ongoing Dwarf Galaxy Merger dm1647+21

Interactions between pairs of isolated dwarf galaxies provide a critical window into low-mass hierarchical, gas-dominated galaxy assembly and the build-up of stellar mass in low-metallicity systems. We present the first Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT/MUSE) optical integral field unit (IFU) observations of the interacting dwarf pair dm1647+21 selected from the TiNy Titans survey. The Hα emission is widespread and corresponds to a total unobscured star formation rate (SFR) of 0.44 M⊙ yr−1, which is 2.7 times higher than the SFR inferred from Sloan Digital Sky Survey (SDSS) data. The implied specific SFR (sSFR) for the system is elevated by more than an order of magnitude above non-interacting dwarfs in the same mass range. This increase is dominated by the lower-mass galaxy, which has a sSFR enhancement of >50. Examining the spatially resolved maps of classic optical line diagnostics, we find that the interstellar medium (ISM) excitation can be fully explained by star formation. The velocity field of the ionized gas is not consistent with simple rotation. Dynamical simulations indicate that the irregular velocity field and the stellar structure is consistent with the identification of this system as an ongoing interaction between two dwarf galaxies. The widespread, clumpy enhancements in the star formation in this system point to important differences in the effect of mergers on dwarf galaxies, compared to massive galaxies; rather than the funneling of gas to the nucleus and giving rise to a nuclear starburst, starbursts in low-mass galaxy mergers may be triggered by large-scale ISM compression, and thus may be more distributed.
On the Equation of State for Diquark Systems and their importance in Astrophysics and Cosmology

With a view to studying diquark formation in QCD phase transition and its consequences in high energy density physics, the energy per quark for the extended scalar diquarks (ESD) as a function of density is calculated, within the framework of an effective phi four theory, for several values of the effective interaction parameter (lamda). Various equations of state for the ESD systems corresponding to the different values of lamda are obtained. The importance of the equations of state for such matter under extreme conditions of density and/or temperature is discussed and the role of the astrophysical diquarks in astrophysics and cosmological diquarks in cosmological conditions is also highlighted.
Dwarf Galaxy Discoveries from the KMTNet Supernova Program. I. The NGC 2784 Galaxy Group

We present BVI surface photometry of 31 dwarf galaxy candidates discovered in a deep image stack from the KMTNet Supernova Program of ∼30 square degrees centered on the nearby NGC 2784 galaxy group. Our final images have a 3σ surface brightness detection limit of mag arcsec−2. The faintest central surface brightness that we measure is mag arcsec−2. If these candidates are at the distance of NGC 2784, then they have absolute magnitudes greater than mag and effective radii larger than 170 pc. Their radial number density decreases exponentially with distance from the center of NGC 2784 until it flattens beyond a radius of 0.5 Mpc. We interpret the baseline density level to represent the background contamination and estimate that 22 of the 31 new candidates are dwarf members of the group. The candidate’s average color, , and Sérsic structural parameters are consistent with those parameters for the dwarf populations of other groups. We find that the central population of dwarfs is redder and brighter than the rest of the population. The measured faint-end slope of the luminosity function, , is steeper than that of the Local Group, but consistent with published results for other groups. Such comparisons are complicated by systematic differences among different studies, but will be simpler when the KMTNet survey, which will provide homogenous data for 15–20 groups, is completed.
The distance duality relation from X-ray and SZ observations of clusters

X-ray and Sunyaev-Zel'dovich data of clusters of galaxies enable to construct a test of the distance duality relation between the angular and luminosity distances. We argue that such a test on large cluster samples maybe of importance, as a consistency check, while trying to distinguish between various models accounting for the acceleration of the universe. The analysis of a data set of 18 clusters shows no significant violation of this relation for a {lambda}-Cold Dark Matter (CDM) model. The origin and amplitude of systematic effects and the possibility to increase the precision of this method are discussed.
Extremely low frequency response of magnetoelectric multilayer composites

A promising generation of extremely low frequency magnetic field sensors, based on multilayer composites (MLCs) of magnetostrictive Terfenol-D (Tb1−xDyxFe2−y) and piezoelectric Pb(Mg1∕3Nb2∕3)O3–PbTiO3, has been developed. Our MLC magnetoelectric sensor presently shows a limit in (i) working frequency of ∼5×10−3Hz; and (ii) magnetic field sensitivity of 10−7,10−9, and 10−11T for frequencies of f=10−2, 1, and 102Hz, respectively. The results open up possibilities for sensitive low frequency passive magnetic anomaly detection.
Quantum dynamics of particles in a discrete two-branes world model: Can matter particles exchange occur between branes?

In a recent paper, a model for describing the quantum dynamics of massive particles in a non-commutative two-sheeted spacetime was proposed. This model considers a universe made with two spacetime sheets embedded in a 5D bulk where the fifth dimension is restricted to only two points. It was shown that this construction has several important consequences for the quantum dynamics of massive particles. Most notably, it was demonstrated that a coupling arises between the two sheets allowing matter exchange in presence of intense magnetic vector potentials. In this paper, we show that non-commutative geometry is not absolutely necessary to obtain such a result since a more traditional approach allows one to reach a similar conclusion. The fact that two different approaches provide similar results suggests that standard matter exchange between branes might finally occur contrary to conventional belief.
Time-resolved spectroscopy of the post-AGB star HD 56126

We have investigated the report of Tamura and Takeuti that the H alpha line of the F-type post-AGB star HD56126 is variable on time-scales of minutes. To this end, HD 56126 was observed on two occasions with the William Herschel Telescope. 17 and 30 spectra (first and second runs, respectively) were taken within time-spans of 1.5 h in order to detect any short-term variations. We find that the H alpha line profile changed strongly over the two-month interval, but no evidence is found for shortterm variability. The variability Tamura and Takeuti claim to find is probably due to the low signal-to-noise ratio in their spectra.
Angular power spectrum analysis on current and future high-energy neutrino data

Astrophysical neutrino events have been measured in the last couple of years, which show an isotropic distribution, and the current discussion is their astrophysical origin. We use both isotropic and anisotropic components of the diffuse neutrino data to constrain the contribution of a broad number of extra-galactic source populations to the observed neutrino sky. We simulate up-going muon neutrino events by applying statistical distributions for the flux of extragalactic sources, and by Monte Carlo method we exploit the simulation for current and future IceCube, IceCube-Gen2 and KM3NeT exposures. We aim at constraining source populations by studying their angular patterns, for which we assess the angular power spectrum. We leave the characteristic number of sources (N★) as a free parameter, which is roughly the number of neutrino sources over which the measured intensity is divided. With existing two-year IceCube data, we can already constrain very rare, bright sources with N★≲100. This can be improved to N★≲ 104–105 with IceCube-Gen2 and KM3NeT with ten-year exposure, constraining the contribution of BL Lacs (N★=6×102). On the other hand, we can constrain weak sources with large number densities, like starburst galaxies (N★ = 107), if we measure an anisotropic neutrino sky with future observations.
Renormalization algorithms for Quantum-Many Body Systems in two and higher dimensions

We describe quantum many--body systems in terms of projected entangled--pair states, which naturally extend matrix product states to two and more dimensions. We present an algorithm to determine correlation functions in an efficient way. We use this result to build powerful numerical simulation techniques to describe the ground state, finite temperature, and evolution of spin systems in two and higher dimensions.
Close-by planets and flares in their host stars

The interaction between the magnetic fields of late-type stars and their close-by planets may produce stellar flares as observed in active binary systems. However, in spite of several claims, conclusive evidence is still lacking. We estimate the magnetic energy available in the interaction using analytical models to provide an upper bound to the expected flare energy. We investigate three different mechanisms leading to magnetic energy release. The first two can release an energy up to $(0.2-1.2) B^{2}_{0} R^{3}/\mu$, where $B_{0}$ is the surface field of the star, $R$ its radius, and $\mu$ the magnetic permeability of the plasma. They operate in young active stars whose coronae have closed magnetic field lines up to the distance of their close-by planets that can trigger the energy release. The third mechanism operates in weakly or moderately active stars having a coronal field with predominantly open field lines at the distance of their planets. The released energy is of the order of $(0.002-0.1) B^{2}_{0} R^{3}/\mu$ and depends on the ratio of the planetary to the stellar fields, thus allowing an indirect measurement of the former when the latter is known. We compute the released energy for different separations of the planet and different stellar parameters finding the conditions for the operation of the proposed mechanisms. An application to eight selected systems is presented. The computed energies and dissipation timescales are in agreement with flare observations in the eccentric system HD 17156 and in the circular systems HD 189733 and HD 179949. This kind of star-planet interaction can be unambiguously identified by the higher flaring frequency expected close to periastron in eccentric systems.
Descriptor systems in the 1990s

After briefly summarizing the growth in the theory of descriptors, or differential algebraic equations (DAEs), over the last two decades, the current challenges and potential successes are discussed. Among these major challenges facing DAE theory are: numerical software for index 3 systems; implicit Runge-Kutta code for low index problems; boundary value problem numerical codes; linearization; new numerical techniques; the initialization problem; direct control information computing; parameter identification; noisy systems; utilization of constraints; implementation for time invariant control; extra derivatives; large-scale DAEs; real-time simulation: and new types of systems. <<ETX>>