Miracle-dz/UniFAR-FTUs huggingface dataset:
Bulk-impurity induced noise in large-area epitaxial thin films of topological insulators

We report a detailed study on low-frequency 1/f-noise in large-area molecular-beam epitaxy grown thin (similar to 10 nm) films of topological insulators as a function of temperature, gate voltage, and magnetic field. When the Fermi energy is within the bulk valence band, the temperature dependence reveals a clear signature of generation-recombination noise in the defect states in the bulk band gap. However, when the Fermi energy is tuned to the bulk band gap, the gate voltage dependence of noise shows that the resistance fluctuations in surface transport are caused by correlated mobility-number density fluctuations due to the activated defect states present in the bulk of the topological insulator crystal with a density of D-it = 3.2 x 10(17) cm(-2) eV(-1). In the presence of the magnetic field, noise in these materials follows a parabolic dependence, which is qualitatively similar to mobility and charge-density fluctuation noise in non-degenerately doped trivial semiconductors. Our studies reveal that even in thin films of (Bi,Sb)(2)Te-3 with thickness as low as 10 nm, the internal bulk defects are the dominant source of noise. Published by AIP Publishing.
Efimov states near a Feshbach resonance and the limits of van der Waals universality at finite background scattering length

We calculate the spectrum of three-body Efimov bound states near a Feshbach resonance within a model which accounts both for the finite range of interactions and the presence of background scattering. The latter may be due to direct interactions in an open channel or a second overlapping Feshbach resonance. It is found that background scattering gives rise to substantial changes in the trimer spectrum as a function of the detuning away from a Feshbach resonance, in particular in the regime where the background channel supports Efimov states on its own. Compared to the situation with negligible background scattering, the regime where van der Waals universality applies is shifted to larger values of the resonance strength if the background scattering length is positive. For negative background scattering lengths, in turn, van der Waals universality extends to even small values of the resonance strength parameter, consistent with experimental results on Efimov states in $^{39}$K. Within a simple model, we show that short-range three-body forces do not affect van der Waals universality significantly. Repulsive three-body forces may, however, explain the observed variation between around $-8$ and $-10$ of the ratio between the scattering length where the first Efimov trimer appears and the van der Waals length.
Evidence of graphene-like electronic signature in silicene nanoribbons

We report on the electronic properties of straight, 1.6 nm wide, silicene nanoribbons on Ag(110), arranged in a one-dimensional grating with a pitch of 2 nm, whose high-resolution scanning tunneling microscopy images reveal a honeycomb geometry. Angle-resolved photoemission shows quantum confined electronic states of one-dimensional character. The silicon band dispersion along the direction of the nanoribbons suggests a behavior analogous to the Dirac cones of graphene on different substrates.
Disc-Jet coupling in the LMXB 4U1636-53 from INTEGRAL

We report on the spectral analysis results of the neutron star, atoll type, low mass X-ray Binary 4U 1636–53 observed by INTEGRAL and BeppoSAX satellites. Spectral behavior in three diﬀerent epochs corresponding to three diﬀerent spectral states has been deeply investigated. Two data set spectra show a continuum well described by one or two soft blackbody plus a Comptonized components with changes in the Comptonizing electrons and black body temperature and the accretion rates, which are typical of the spectral transitions from high to low state. In one occasion INTEGRAL spectrum shows, for ﬁrst time in this source, a hard tail dominating the emission above 30 keV. The total spectrum is ﬁtted as the sum of a Comptonized component similar to soft state and a power-law component (Γ = 2 . 76), indicating the presence of a non thermal electron distribution of velocities. In this case, a comparison with hard tails detected in soft states from neutron stars systems and some black hole binaries suggests that a similar mechanism could originate these components in both cases.
Sagittarius Tidal Debris 90 Kiloparsecs from the Galactic Center

A new overdensity of A-colored stars in distant parts of the Milky Way's stellar halo, at a dereddened Sloan Digital Sky Survey magnitude of g0 = 20.3, is presented. Identification of associated variable RR Lyrae candidates supports the claim that these are blue horizontal branch stars. The inferred distance of these stars from the Galactic center is 90 kpc, assuming that the absolute magnitude of these stars is M = 0.7 and that the Sun is 8.5 kpc from the Galactic center. The new tidal debris is within 10 kpc of the same plane as other confirmed tidal debris from the disruption of the Sagittarius dwarf galaxy and could be associated with the trailing tidal arm. Distances to the Sagittarius stream estimated from M stars are about 13% smaller than our inferred distances. The tidal debris has a width of at least 10° and is traced for more than 20° across the sky. The globular cluster NGC 2419 is located within the detected tidal debris and may also have once been associated with the Sagittarius dwarf galaxy.
Model for Relaxation Oscillations of a Luminous Accretion Disk in GRS 1915+105: Variable Inner Edge

To understand the bursting behavior of the microquasar GRS 1915+105, we calculate time evolution of a luminous, optically thick accretion disk around a stellar-mass black hole undergoing limit-cycle oscillations between the high- and low-luminosity states. Specifically, we carefully solve the behavior of the innermost part of the disk, since it produces significant number of photons during the burst and fit the theoretical spectra with the multicolor disk model. The fitting parameters are Tin (the maximum disk temperature) and Rin (the innermost radius of the disk). We find an abrupt, transient increase in Tin and a temporary decrease in Rin during a burst, which are actually observed in GRS 1915+105. The precise behavior is subject to the viscosity prescription. We prescribe the radial-azimuthal component of viscosity stress tensor to be Trφ = -αΠ(pgas/p)μ, with Π being the height-integrated pressure, α and μ being the parameters, and p and pgas being the total pressure and gas pressure on the equatorial plane, respectively. The model with μ = 0.1 can produce the overall time changes of Tin and Rin but cannot give an excellent fit to the observed amplitudes. The model with μ = 0.2, on the other hand, gives the right amplitudes, but the changes of Tin and Rin are smaller. Although precise matching is left as future work, we may conclude that the basic properties of the bursts of GRS 1915+105 can be explained by our "limit-cycle oscillation" model. It is then required that the spectral hardening factor at high luminosities should be about 3 at around the Eddington luminosity instead of less than 2 as is usually assumed.
H I versus H α – comparing the kinematic tracers in modelling the initial conditions of the Mice

We explore the effect of using different kinematic tracers (HI and H$\alpha$) on reconstructing the encounter parameters of the Mice major galaxy merger (NGC 4676A/B). We observed the Mice using the SparsePak Integral Field Unit (IFU) on the WIYN telescope, and compared the H$\alpha$ velocity map with VLA HI observations. The relatively high spectral resolution of our data (R $\approx$ 5000) allows us to resolve more than one kinematic component in the emission lines of some fibers. We separate the H$\alpha$-[N II] emission of the star-forming regions from shocks using their [N II]/H$\alpha$ line ratio and velocity dispersion. We show that the velocity of star-forming regions agree with that of the cold gas (HI), particularly, in the tidal tails of the system. We reconstruct the morphology and kinematics of these tidal tails utilizing an automated modeling method based on the Identikit software package. We quantify the goodness of fit and the uncertainties of the derived encounter parameters. Most of the initial conditions reconstructed using H$\alpha$ and HI are consistent with each other, and qualitatively agree with the results of previous works. For example, we find 210$\pm^{50}_{40}$ Myrs, and 180$\pm^{50}_{40}$ Myrs for the time since pericenter, when modeling H$\alpha$ and HI kinematics, respectively. This confirms that in some cases, H$\alpha$ kinematics can be used instead of HI kinematics for reconstructing the initial conditions of galaxy mergers, and our automated modeling method is applicable to some merging systems.
High Angular Resolution JHK Imaging of the Centers of the Metal-poor Globular Clusters NGC 5272 (M3), NGC 6205 (M13), NGC 6287, and NGC 6341 (M92)

The Canada-France-Hawaii Telescope Adaptive Optics Bonnette has been used to obtain high angular resolution JHK images of the centers of the metal-poor globular clusters NGC 5272 (M3), NGC 6205 (M13), NGC 6287, and NGC 6341 (M92). The color-magnitude diagrams (CMDs) derived from these data include the upper main sequence and most of the red giant branch and agree with published photometric measurements of bright stars in these clusters. The photometric accuracy is limited by point-spread function variations, which introduce systematic errors of a few hundredths of a magnitude near the reference star. The NGC 6287 CMDs are of particular interest, as they are free of the scatter caused by foreground stars and differential reddening that have plagued previous efforts to study the stellar content of this inner spheroid cluster. The horizontal branch (HB) of NGC 6287 contains stars spanning a broader range of temperatures than that of NGC 6341. NGC 6287 is thus the only known member of the metal-poor inner spheroid to deviate from the HB morphology versus metallicity relation defined by other clusters in the inner Galaxy. The clusters are paired according to metallicity, and the near-infrared CMDs and luminosity functions are used to investigate the relative ages within each pair. The near-infrared CMDs provide the tightest constraints on the relative ages of the classical second-parameter pair NGC 5272 and NGC 6205 and indicate that these clusters have ages that differ by no more than ±1 Gyr. These results thus support the notion that age is not the second parameter. We tentatively conclude that NGC 6287 and NGC 6341 have ages that differ by no more than ±2 Gyr. However, the near-infrared spectral energy distributions of stars in NGC 6287 appear to differ from those of stars in outer halo clusters, bringing into question the validity of this age estimate.
XMM-Newton observation of MV Lyr and the sandwiched model confirmation

We present spectral and timing analyses of simultaneous X-ray and UV observations of the VY Scl system MV Lyr taken by XMM-Newton, containing the longest continuous X-ray+UV light curve and highest signal-to-noise X-ray (EPIC) spectrum to date. The RGS spectrum displays emission lines plus continuum, confirming model approaches to be based on thermal plasma models. We test the sandwiched model based on fast variability that predicts a geometrically thick corona that surrounds an inner geometrically thin disc. The EPIC spectra are consistent with either a cooling flow model or a 2-T collisional plasma plus Fe emission lines in which the hotter component may be partially absorbed which would then originate in a central corona or a partially obscured boundary layer, respectively. The cooling flow model yields a lower mass accretion rate than expected during the bright state, suggesting an evaporated plasma with a low density, thus consistent with a corona. Timing analysis confirms the presence of a dominant break frequency around log(f/Hz) = -3 in the X-ray Power Density Spectrum (PDS) as in the optical PDS. The complex soft/hard X-ray light curve behaviour is consistent with a region close to the white dwarf where the hot component is generated. The soft component can be connected to an extended region. We find another break frequency around log(f/Hz) = -3.4 that is also detected by Kepler. We compared flares at different wavelengths and found that the peaks are simultaneous but the rise to maximum is delayed in X-rays with respect to UV.
Revealing two radio-active galactic nuclei extremely near PSR J0437-4715

Newton's gravitational constant G may vary with time at an extremely low level. The time variability of G will affect the orbital motion of a millisecond pulsar in a binary system and cause a tiny difference between the orbital period-dependent measurement of the kinematic distance and the direct measurement of the annual parallax distance. PSR J0437-4715 is the nearest millisecond pulsar and the brightest at radio wavelengths. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, we searched for compact radio sources quite close to PSR J0437-4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, we detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and separations of 13 and 45 arcsec. With a network consisting of the Long Baseline Array and the Kunming 40-m radio telescope, we found that both sources have a point-like structure and a brightness temperature of >= 10(7) K. According to these radio inputs and the absence of counterparts in other bands, we argue that they are most likely the compact radio cores of extragalactic active galactic nuclei, rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable us to achieve a sub-pc distance accuracy with in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of G in the near future.
Hubble Space Telescope Observations of Synchrotron Jets

The Hubble Space Telescope for the first time enables optical and UV images of jets to be obtained with spatial resolution comparable to radio interferometric techniques. Because synchrotron emission at these wavelengths is a diagnostic of particles several orders of magnitude higher in energy and correspondingly shorter in lifetime than those probed by radio, the sites of particle acceleration may be more readily identified in the optical and UV. Short-lifetime optical synchrotron emission in the SE inner radio lobe of M87 argues strongly for the presence of an invisible counterjet. A detailed comparison of HST and VLA images of the M87 jet shows there are very strong similarities in overall morphology, but that there are also significant differences. The optical and UV radiation is more localized within the knots than the radio emission and appears more confined toward the jet center. These differences may arise from localized shocks, sited at the optical knots with diffusion of relativistic particles away from those knots, or else they may be due to nonuniform magnetic fields and distributed acceleration processes. The UV fluxes of the knots are consistent with a single power law from optical to X-ray. Optical jets in other radio galaxies show diverse properties—the jet of PKS 0521—36 is smoothly resolved by HST while that of 3C 66B shows previously unsuspected filmentary structure. Likewise, the jet of 3C 273 shows newly observed optical filaments and an intensity distribution quite unlike that of the radio emission. Like M87, the optical jet of 3C 273 is narrower than the radio jet. The serendipitous discovery of a new optical synchrotron jet in 3C 264 suggests that optical jets may be relatively common.
Dynamical Timescale of Pre-collapse Evolution Inferred from Chemical Distribution in the Taurus Molecular Cloud-1 (TMC-1) Filament

We present observations and analyses of the low-mass star-forming region, Taurus Molecular Cloud-1 (TMC-1). CS (J = 2–1)/N2H+ (J = 1–0) and C17O (J = 2–1)/C18O (J = 2–1) were observed with the Five College Radio Astronomy Observatory and the Seoul Radio Astronomy Observatory, respectively. In addition, Spitzer infrared data and 1.2 mm continuum data observed with Max-Planck Millimetre Bolometer are used. We also perform chemical modeling to investigate the relative molecular distributions of the TMC-1 filament. Based on Spitzer observations, there is no young stellar object along the TMC-1 filament, while five Class II and one Class I young stellar objects are identified outside the filament. The comparison between column densities calculated from dust continuum and C17O 2–1 line emission shows that CO is depleted much more significantly in the ammonia peak than in the cyanopolyyne peak, while the column densities calculated from the dust continuum are similar at the two peaks. N2H+ is not depleted much in either peak. According to our chemical calculation, the differential chemical distribution in the two peaks can be explained by different timescales required to reach the same density, i.e., by different dynamical processes.
Resolved magnetic dynamo action in the simulated intracluster medium

Faraday rotation and synchrotron emission from extragalactic radio sources give evidence for the presence of magnetic fields extending over ˜ Mpc scales. However, the origin of these fields remains elusive. With new high-resolution grid simulations, we studied the growth of magnetic fields in a massive galaxy cluster that in several aspects is similar to the Coma cluster. We investigated models in which magnetic fields originate from primordial seed fields with comoving strengths of 0.1 nG at redshift z = 30. The simulations show evidence of significant magnetic field amplification. At the best spatial resolution (3.95 kpc), we are able to resolve the scale where magnetic tension balances the bending of magnetic lines by turbulence. This allows us to observe the final growth stage of the small-scale dynamo. To our knowledge, this is the first time that this is seen in cosmological simulations of the intracluster medium. Our mock observations of Faraday rotation provide a good match to observations of the Coma cluster. However, the distribution of magnetic fields shows strong departures from a simple Maxwellian distribution, suggesting that the three-dimensional structure of magnetic fields in real clusters may be significantly different than what is usually assumed when inferring magnetic field values from rotation measure observations.
Wedge Absorbers For Muon Cooling With a Test Beam At MICE

Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE beam line could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test are explored in simulation and possible experimental configurations with simulated results are presented.
Deep 3.8 Micron Observations of the Trapezium Cluster

We present deep 3.8 μm L′ imaging observations of the Trapezium cluster in Orion obtained with the ESO VLT. We use these observations to (1) search for infrared excess emission and evidence for protoplanetary disks associated with the faint, substellar population of this young cluster and (2) investigate the nature and extent of a recently discovered population of deeply embedded sources located in dense molecular gas behind the cluster. We detected 38 L′ sources with substellar luminosities. In addition, we detected 24 L′ sources that were spectroscopically classified as substellar objects in previous studies. Examining the infrared colors of all these sources, we determine an infrared excess fraction of 50% ± 20% from the JHKsL′ colors for both the luminosity-selected and spectroscopically selected substellar samples. This finding confirms the presence of infrared excess, likely due to circumstellar disks, around a significant fraction of the cluster's substellar population, consistent with the indications of earlier observations obtained at shorter (JHKs) wavelengths. Our deep L′ imaging survey also provides new information concerning the deeply embedded population of young objects located in the molecular cloud behind the cluster and revealed in an earlier L-band imaging survey of the region. In particular, our present L′ survey doubles the number of sources in the cluster region known to possess extremely red K-L colors. These objects exhibit K-L′ colors indicative of deeply buried, possibly protostellar, objects that likely mark the site of the most recent and ongoing star formation in the region. We find the surface density distribution of the deeply embedded population to follow that of the background molecular ridge and to be highly structured, consisting of a string of at least five significant subclusters. These subclusters may represent the primordial building blocks out of which the cluster was and perhaps still is being assembled. These observations may thus provide insights into the early stages of cluster formation and appear consistent with recent simulations that suggest that the Trapezium cluster may have formed from numerous but small primordial subclusters.
Fabrication of Low-Residual-Stress AlN Thin Films and Their Application to Microgenerators for Vibration Energy Harvesting

For obtaining low residual stress, AlN thin films were prepared on Si substrates with diverse bottom electrode materials of Pt/Ti, Au/Cr, Al, and Ti by the electron cyclotron resonance (ECR) deposition technology. Among them, AlN thin films deposited on the substrate with the Al bottom electrode demonstrated not only low residual stress but also high enough c-axis orientation, and thus they were utilized to fabricate microgenerators by the micromachining process for converting environmental vibration energy into electric energy. The AlN microgenerator had a resonant frequency of 1042.6 Hz and the output power was 1.42 µW at the vibration frequency and 1g acceleration.
Altimeter crossover methods for precision orbit determination and the mapping of geophysical parameters

Accurate orbit determination and the recovery of geophysical parameters are presently attempted via methodologies which use differenced height measurements at the points where the ground tracks of the altimetric satellite orbits intersect. Such 'crossover measurements' could significantly improve the earth's gravity field model. Attention is given to a novel technique employing crossover measurements from two satellites carrying altimeter instruments; this method can observe zonal harmonics of the earth's geopotential which are weakly observed through single-satellite crossovers. This dual-satellite crossover technique will be applicable to data from such future oceanographic satellites as ERS-1.
Further observations of the eclipsing X-ray burst source MXB 1659-29

An analysis is presented of data for MXB 1659-29 obtained during October 2-10, 1976 and June 6-11, 1977 using the SAS 3 X-ray Observatory (Lewin et al., 1976) and during September 8-13, 1978 using the A-1 experiment aboard HEAO 1 (Wood et al., 1984). The data confirm the 7.1 hr orbital period and provide evidence for the 15-min X-ray eclipse reported by Cominsky and Wood (1984). A total of 32 X-ray bursts are detected during the SAS 3 observations. By combining the data with previously published results, the orbital period is found to be about 0.29650474 days. 22 references.