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detection of traces of iron in the brain is useful for early diagnosis, progression and treatment monitoring of various neurologic and psychiatric diseases. iron and, in general, different tissues possessing different magnetic susceptibilities expose themselves via small spatial variations of the magnetic field during ... | magnetic susceptibility measurements from magnetic resonance imaging (mri) |
this article examines the dispersion characteristics and energy distribution in different regions of the bifurcated waveguide with vertical step discontinuities. in this research study, we have considered mathematical model of noise reduction devices, specifically analyzing the acoustic wave propagation problem in a bi... | analyzing the acoustic wave propagation characteristics in discontinuous bifurcated waveguide |
a multi-lens stereo reconstruction approach is developed to measure the free surface deformation of water waves in a wave basin. a massive of tiny granule served as the thin film floating on the free surface ensures the function of the common multi-lens stereo imaging technique in reconstructing the wave surface. the g... | multi-lens stereo reconstruction of the free surface waves in wave basin |
this paper deals with metallographic studies and ultrasonic investigations of acoustic birefringence in the base metal and heat affected zone of welded specimens of astm 1020 steel under uniaxial tension and low-cycle fatigue. we examined microstructural changes on the surface using optical microscope. it was found tha... | acoustic birefringence changes in the base metal and heat affected zone of astm 1020 steel under plastic deformation and fatigue |
it is well known that earthquakes and tsunamis couple energy into the dynamically fluid atmosphere. this energy can propagate up to the ionosphere where we can observe perturbations in the total-electron content (tec) signals measured by global navigation space systems (gnss). recent emphasis has been placed on using t... | backprojection of gnss total-electron content signals for recent large earthquakes |
damage imaging of structural components in the field of non destructive evaluations (nde) and structural health monitoring (shm) using ultrasonic waves is usually performed by conventional imaging techniques, such as delayand-sum (das), by back-propagating the recorded waveforms to identify locations and size of defect... | ultrasonic damage imaging of structural components with bulk and guided waves using match coefficients |
the band structure is a frequency/energy versus wave vector/momentum relationship that fundamentally describes the nature of wave motion in a periodic medium. it is immensely valuable for predicting and understanding the properties of electronic, photonic, and phononic materials, and is typically computed numerically. ... | fast band-structure computation for phononic and electronic waves in crystals |
recent data analyses and modeling indicate opportunities to use upper atmospheric and ionospheric observations as a supplemental source of information about earthquakes and tsunamis, through the characterization of acoustic and gravity waves, agws, generated by them (e.g., astafyeva and shults, jgr, 2018; inchin et al.... | observations and modeling of ionospheric acoustic-gravity waves as diagnostics of earthquake evolutions |
the nearshore region is an extremely dynamic system, presenting variations in its morphology over short periods of time. therefore, it is of paramount importance to monitor the seabed changes, especially in coastal and harbour areas due to its particular relevance for the safety of navigation and for coastal erosion ma... | acquisition of nearshore bathymetry using wavelets |
in laboratory studies of shear alfvén waves, control of the perpendicular wavenumber is an important tool for testing dispersion relations, particle scattering, plasma heating, etc. efficient generation (wave amplitude per unit driver current) is also desirable for the lab and spacecraft. generally, time harmonic induc... | efficient generation of variable, high k⊥, kinetic alfvén waves |
knowledge of the behavior of the ionosphere is very important for space weather services. a wide variety of ground based and satellite existing and future systems (communications, radar, surveillance, intelligence gathering, satellite operation, etc) is affected by the ionosphere. there are the needs for reliable and e... | ionospheric research for space weather service support |
a perfectly matched layer (pml) has become a widespread technique for preventing reflections from computational boundaries for electromagnetic wave propagation problems in frequency domains. especially, a pml for the helmholtz equation is well developed and applied to the finite difference method. in the currently used... | a property-dependent perfectly matched layer with a single additional layer for maxwell's equations in finite difference frequency domains |
the wave propagation in an inhomogeneous half space with a semi-cylindrical surface bump is investigated by the means of complex function method. with the origin of the coordinate system as the center, the density of the medium changes radially. to solve the helmholtz equation with variable coefficients caused by the i... | scattering of sh waves by a semi-cylindrical bump in an inhomogeneous half-space |
the intelligent reflecting surface (irs) is a two-dimensional (2d) surface with a programmable structure and is composed of many arrays. the arrays are used to supervise electromagnetic wave propagation by altering the electric and magnetic properties of the 2d surface. irs can influentially convert wireless channels t... | spectral efficiency improvement using bi-deep learning model for irs-assisted mu-miso communication system |
we present progress on a simultaneous time-advance of nimrod's fluid quantities with consistent kinetic closures obtained from a solution of the chapman-enskog-like drift kinetic equation. a semi-implicit formulation is employed to ensure numerical stability and accommodate time steps that are large compared to the com... | simultaneous advance for extended mhd with kinetic closures: verification and applications |
in the last decade, digital rock physics (drp) has become an avenue to investigate physical and mechanical properties of geomaterials. drp offers the advantage of simulating laboratory experiments on numerical samples that are obtained from analytical methods. potentially, drp could allow sparing part of the time and r... | segmentation-less digital rock physics |
anisotropy of the lowermost mantle beneath the south- to central pacific is investigated using us-array receivers and events located near the tonga-fiji subduction zones. differential splitting in three different distance ranges (65° -85° , 90° -110° and >110°) of s-scs, sks-s, sks-sdiff phases is used. by utilizing... | anisotropy beneath the southern pacific - real or apparent? |
we study the dynamics of solitary waves traveling in a one-dimensional chain of bistable elements in the presence of a local inhomogeneity (defect). numerical simulations reveal that depending upon its initial speed, an incoming solitary wave can get transmitted, captured or reflected upon interaction with the defect. ... | defect engineering of nonlinear wave propagation in bistable mechanical lattices |
optical coherence elastography (oce) is a widely investigated noninvasive technique for estimating the mechanical properties of tissue. in particular, vibrational oce methods aim to estimate the shear wave velocity generated by an external stimulus in order to calculate the elastic modulus of tissue. in this study, we ... | a comparative study of shear wave speed estimation techniques in optical coherence elastography applications |
structures consisting of three-layer shells are widely used in various fields of engineering and technology, the construction of nuclear power plants, power and chemical engineering and other areas of the national economy. the aim of the work is to study the issue of energy dissipation during natural vibrations of visc... | energy dissipation under natural vibrations of viscoelastic composite cylindrical shells |
spin wave, also known as magnon, is one kind of low energy collective excitations in quantum magnets, which has the potential of transferring information in applications. spin wave dispersions carry information about both magnon properties and the nature of the magnetic ground states. in experiments, specialized techni... | probing the goldstone spin wave excitations of an easy-plane canted-antiferromagnet |
the rhine-ruhr region is located in the state of north rhine-westphalia (nrw) in western germany. due to the transition from coal to low-carbon heat sources, potential locations in nrw must be explored regarding to their geothermal potential. the bavarian area has shown for the last 20 years, that deep geothermal energ... | establishing a 3d model for the rhine-ruhr region based on the geology and property distribution. |
solar wind models are highly dependent on global magnetic fields at the solar surface as their inner boundary condition, and the lack of global field data is a significant problem plaguing solar wind modeling. currently, only direct observations of the near-side magnetic field exist and far-side approximations are inca... | inferring the sun's far-side magnetic flux for operations using time-distance helioseismic imaging |
angwin (antarctic gravity wave imaging/instrument network) is an international airglow imager/instrument network in the antarctic, which commenced observations in 2011. it seeks to reveal characteristics of mesospheric gravity waves, and to study sources, propagation, breaking of the gravity waves over the antarctic an... | horizontal structure and propagation characteristics of mesospheric gravity waves observed by antarctic gravity wave imaging/instrument network (angwin), using a 3-d spectral analysis technique |
wave energy converters (wecs) have been increasingly installed in various coastal regions due to the higher energy density of waves than other renewable sources. regarding coastal regions' high potential, it is remarkably better to emplace multiple devices concerning a layout of the arrays with different configurations... | a multi-objective approach for location and layout optimization of wave energy converters |
recently it has been demonstrated that it is possible to detect both longitudinal and shear waves as well as measure their velocities for a non-transparent iron layer compressed in a diamond anvil cell (dac) to pressures approaching 23 gpa by using laser ultrasonics (lu) technique. these experiments were conducted in t... | combined laser ultrasonics, and raman scattering in diamond anvil cell system operating in the transmission configuration |
estimation of local seismic response plays a key role in assessing local seismic hazard and particularly in the design of shaking scenarios. modelling local seismic response involves knowing of the shear wave velocity (vs) and quality factor (qs) profiles for the site in question. the many techniques that have been dev... | high frequency attenuation of s waves in alluvial deposits of the central po plain (northern italy) |
thermographic super-resolution techniques allow the resolution of defects/inhomogeneities beyond the classical limit, which is governed by the diffusion properties of thermal wave propagation. photothermal super-resolution is based on a combination of an experimental scanning strategy and a numerical optimization which... | full-frame thermographic super-resolution with 2d-structured laser heating |
we investigate the variability of high-degree acoustic mode frequencies of the sun and surface activity over multiple solar cycles to improve our understanding of the connection between the solar interior and atmosphere. the changes in oscillation frequencies also provide a unique tool to examine the similarities and d... | variability of high-degree acoustic mode frequencies of the sun and their connection with the surface magnetic activity |
knowledge of the seabed properties in an oceanic waveguide facilitates the understanding of wave propagation in the medium and, eventually, the implementation of tasks such as target detection and localization. seabed characterization is, thus, a topic of extensive interest in the ocean acoustics research community. in... | feature selection for seabed characterization using non-linear regression and decision trees |
for decades, the low‑strain impact integrity testing using a hammer blow is well established as a method of quality assurance for various pile types. however, this method has its limitations. our research and development focuses on improving the excitation signal using a shaker system in contrast to the standard hammer... | advances in pile integrity testing |
a suite of partial coupling experiments have been devised under a coupled gcm framework to isolate the effects of the feedbacks from the change of the wind-driven ocean circulation and air-sea heat flux in the global climate response to the forcing of increasing co2. specifically, the sst response has been examined in ... | exploring the tropical response to global warming via an overriding technique |
waves are affected by sub-wavelength structures not in an explicit but in an effective way. here we present a novel homogenization technique, referred to as "discrete wave equation upscaling" (dweu), that operates on the discrete form of the wave equation. it provides the effective medium properties directly on a coars... | discrete wave equation upscaling |
mimic near-surface seismic imaging conducted in well-controlled laboratory conditions is potentially a powerful tool to study large scale wave propagations in geological media by means of upscaling. laboratory measurements are indeed particularly suited for tests of theoretical modellings and comparisons with numerical... | on the use of a laser ablation as a laboratory seismic source |
elastic wave imaging optical coherence elastography (ewi-oce) is an emerging technique that can quantify local biomechanical properties of tissues. however, long acquisition times make this technique unfeasible for clinical use. here, we demonstrate a noncontact single shot line-field oce technique using a line-field i... | single shot line-field optical coherence elastography |
in-situ fatigue damage diagnosis and prognosis is a challenging problem for both metallic and composite materials and structures. there are various uncertainties arising from material properties, component geometries, measurement noise, feature extraction techniques, and modeling errors. it is essential to manage and i... | probabilistic fatigue damage diagnostics and prognostics for metallic and composite materials |
this thesis establishes advanced theoretical-computational techniques to understand and predict the mechanical properties of structural lattice metamaterials with a focus on the effective elastic properties. first, attention is devoted to the effective stiffness of hierarchical nanolattices, which depends on lattice to... | computational modeling of the mechanics of elastic structural lattices: effects of lattice architecture and hierarchy |
in this paper, the energy flux in a pile modeled as an elastic shell, is studied theoretically and experimentally. based on this analysis, a new procedure is proposed to quantify the pile installation efficiency. this procedure is of importance for vibratory installation of the foundations of offshore wind turbines and... | energy flux analysis for quantification of vibratory pile driving efficiency |
recently we have developed a new numerical approach for pdes with constant coefficients on irregular domains and cartesian meshes. in this paper we extend it to a much more general case of pdes with variable coefficients that have a lot of applications; e.g., the modeling of functionally graded materials, the inhomogen... | a high-order numerical approach with cartesian meshes for modeling of wave propagation and heat transfer on irregular domains with inhomogeneous materials |
mantle plumes are notoriously challenging to image in seismology, due to their subtle effects on the seismic wave field, leading to controversy regarding their origin and structure. traditional approaches based on picking arrival times of phases can miss the imprint of plumes on a seismogram, as diffraction effects are... | on the detectability of mantle plumes using seismic arrays |
the body-wave propagation from remote seismic events has a near-vertical incidence beneath seismic stations that can be use to reconstruct the seismic response of the earth's structure underneath the recorders. an alternative to bring out the body-wave reflectivity at the subsurface discontinuities with no need of cont... | resolving the crustal structure with ambient noise and p wave coda: a study on the feasibility of single-station autocorrelations. |
using numerical simulations, we show that jets with features of type ii spicules can be formed due to magnetic reconnection in a scenario with magnetic resistivity. for this we model the low chromosphere-corona region assuming resistive mhd rules the dynamics of the plasma. the magnetic filed configurations we analyze ... | jet formation in solar atmosphere due to magnetic reconnection |
this paper presents a stable method for solving the kinematic boundary condition equation (kbc) in fully nonlinear potential flow (fnpf) models. the method is motivated by a total variation diminishing (tvd) approach, which makes it especially applicable to advection-dominated partial differential equations such as the... | a stable free-surface boundary solution method for fully nonlinear potential flow models |
the formosat-7/cosmic-2 (f7c2) satellite is a follow-on mission of the formosat-3/cosmic (f3c) to continuously provide gnss (global navigation satellite system) radio occultation (ro) soundings for monitoring the global climate changes and space weather. the first phase of f7c2 mission consists of 6 satellites, which w... | orbit prediction of formosat-7/cosmic-2 constellation for satellite laser ranging tracking |
experimental and modeling efforts show that small-scale gravity waves (gw) essentially affect large-scale circulations, thermal states, and dynamics from the surface to the middle atmosphere. in climate modeling and weather-forecasting applications the gravity-wave drag and its interaction with large-scale dynamics are... | observations of up- and downward propagating gravity waves in the strato- and mesosphere. |
a system of differential equations describing collinear light diffraction on a three-dimensional acoustic zug of finite length with a sinc-shaped time envelope, where linear frequency modulation is used, is obtained. the obtained solutions of differential equations allow us to describe the longitudinal and transverse d... | investigation of collinear acousto-optical diffraction of light fluxes |
the international deep propagating gravity wave experiment (deepwave) campaign was carried out in new zealand during austral winter 2014. its aim was to extensively study gravity waves from their sources in the troposphere, along their propagation through the atmosphere to the regions of dissipation at high altitudes. ... | lidar measurements of gravity waves in the middle atmosphere in southern hemisphere winter above new zealand |
this article presents a case study concerning a seismic characterization project. full-wave sonic logging was used to characterize the shallow compressional wave and shear wave velocity profiles in the site. anomalous values of the poisson's ratio derived from the velocity profiles suggested that the boreholes might ha... | indirect determination of shear wave velocity in slow formations using full-wave sonic logging technique |
remote sensing seismology is now routine for stars and the sun, through photometry or doppler measurement of the velocity of their photosphere. ionospheric remote sensing seismology has also emerged for the earth through the monitoring of total electronic content by gnss occultation or airglow, and can be considered on... | planetary and earth seismology with space geodesy: seismic requirements on performances for earth, europa, the moon and jupiter. |
we present a non-contact "frequency domain photoacoustic microscope" (fd-pam) in which photoacoustic signal is generated by an amplitude modulated continuous-wave (cw) laser and detected at the sample surface using two wave mixing (interferometer) in a photorefractive crystal (prc). the optical detection eliminates the... | frequency domain non-contact photoacoustic microscopy |
the underwater acoustic communications environment is severely band-limited, which leads to a bottleneck in data transfer. existing methods of data transfer in underwater acoustic communications applications typically rely primarily on conventional temporal and frequency modulation techniques and achieve bit rates peak... | ray tracing of long-range underwater acoustic vortex wave propagation |
the physical properties of the inner cores of the giant planets are poorly known. to date, such investigations have been limited to measuring gravitational influences from a handful of orbital probes. the most recent attempt to map the interior is via pmode (the planetary multilevel oscillations and dynamics experiment... | organizing jovian dopplergram data |
measuring temperature distribution is an important technique in the fields of meteorology, agriculture, and architecture. the acoustic probe emits sound waves from a speaker and measures the time it takes for the waves to reach a microphone, enabling the measurement of the average temperature between the speaker and th... | acoustic probe for temperature measurement suitable for operation with audio interfaces having random input/output delays |
this paper presents numerical simulations of the acoustic wave propagation phenomenon modelled via linearized euler equations. a meshless method based on collocation of the strong form of the equation system is adopted. moreover, the weighted least squares method is used for local approximation of derivatives as well a... | simulation of the acoustic wave propagation using a meshless method |
eruptive events such as coronal mass ejections (cmes) and flares can accelerate particles and generate shock waves. tracking of shock waves and predicting their arrival at the earth is an important scientific goal. space based radio observations provide us the unique opportunity to track shock waves in the inner helios... | diagnosing cme/shock wave association using the radio triangulation technique |
in this study, we present the analysis of steepened ultra-low frequency (ulf) waves in the foreshock region upstream of mars' bow shock observed by the mars atmosphere and volatile evolution (maven) spacecraft at mars. a survey of maven magnetic field and plasma measurements shows quasi-periodic gradual increases follo... | maven observations of steepened ultra-low frequency waves in the upstream martian foreshock region |
in this work, we obtain the shadow images of spherically symmetric scalar boson and proca stars using analytical fittings of numerical solutions, when illuminated by a geometrically thin accretion disk. we chose a sample of four boson and four proca stars with radii ranging from more compact configurations with r ∼9 m ... | shadows of boson and proca stars with thin accretion disks |
population iii stars ended the cosmic dark ages and began early cosmological reionization and chemical enrichment. however, in spite of their importance to the evolution of the early universe, their properties remain uncertain because of the limitations on previous numerical simulations and the lack of any observationa... | the birth mass function of population iii stars |
in this work we analyze the observational properties of incompressible relativistic fluid spheres with and without thin-shells when surrounded by thin accretion disks. we consider a set of six configurations with different combinations of the star radius r and the thin-shell radius rσ to produce solutions with neither ... | observational properties of relativistic fluid spheres with thin accretion disks |
we present the multiwavelength analysis of the tidal disruption event (tde) at 2018hyz (asassn-18zj). from follow-up optical spectroscopy, we detect the first unambiguous case of resolved double-peaked balmer emission in a tde. the distinct line profile can be well-modeled by a low eccentricity (e ≈ 0.1) accretion disk... | double-peaked balmer emission indicating prompt accretion disk formation in an x-ray faint tidal disruption event |
asassn-14li is a recently discovered tidal disruption event with an exceptionally rich data set: spectra and lightcurves in soft x-rays, uv, optical, and radio. to understand its emission properties in all these bands, we have extended our model for post-tidal disruption accretion and photon production to estimate both... | asassn-14li: a model tidal disruption event |
we determine radial velocities and mass flow rates in a sample of 54 local spiral galaxies by modeling high-resolution and high-sensitivity data of the atomic hydrogen emission line. we found that, although radial inflow motions seem to be slightly preferred over outflow motions, their magnitude is generally small. mos... | radial motions and radial gas flows in local spiral galaxies |
we use well-established observational evidence to draw conclusions about the fundamental nature of the viscosity in accretion discs. to do this, we first summarise the observational evidence for the value of the dimensionless accretion disc viscosity parameter α, defined by shakura and sunyaev (1973, 1976). we find tha... | on the physical nature of accretion disc viscosity |
we present the results of target of opportunity (too) observations made with astrosat of the newly discovered black hole binary maxi j1535-571. we detect prominent c-type quasi-periodic oscillations (qpos) of frequencies varying from 1.85 to 2.88 hz, along with distinct harmonics in all the astrosat observations. we no... | astrosat view of maxi j1535-571: broad-band spectro-temporal features |
we present and analyze a set of three-dimensional, global, general relativistic radiation magnetohydrodynamic simulations of thin, radiation-pressure-dominated accretion disks surrounding a nonrotating, stellar-mass black hole. the simulations are initialized using the shakura-sunyaev model with a mass accretion rate o... | the role of strong magnetic fields in stabilizing highly luminous thin disks |
based on well-established scaling relation for star-forming galaxies as a function of redshift, we argue that the implied growth by a large factor of their angular momentum requires that the angular momentum of the inflowing gas fuelling star formation and disc growth must also secularly increase. we then propose that ... | disc growth and quenching |
we present new reflection models specifically tailored to model the x-ray radiation reprocessed in accretion disks around neutron stars, in which the primary continuum is characterized by a single-temperature blackbody spectrum, emitted either at the surface of the star or at the boundary layer. these models differ sig... | relativistic x-ray reflection models for accreting neutron stars |
cygnus x-1 is a well-studied persistent black hole x-ray binary. recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass m, the orbital inclination i, and the source distance d, have been updated. in this work we redetermine the spin parameter using the continuum... | re-estimating the spin parameter of the black hole in cygnus x-1 |
we report on a neutron star interior composition explorer (nicer) observation of the galactic x-ray binary and stellar-mass black hole candidate, maxi j1535-571. the source was likely observed in an “intermediate” or “very high” state, with important contributions from both an accretion disk and hard x-ray corona. the ... | a nicer spectrum of maxi j1535-571: near-maximal black hole spin and potential disk warping |
we show that the bulge and the disk of the milky way (mw) at r ≲ 7 kpc are well described by a unique chemical evolution and a two-phase star formation history (sfh). we argue that the populations within this inner disk, not the entire disk, are the same, and that the outer lindblad resonance (olr) of the bar plays a k... | phylogeny of the milky way's inner disk and bulge populations: implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching |
understanding how material accretes onto the rotationally supported disk from the surrounding envelope of gas and dust in the youngest protostellar systems is important for describing how disks are formed. magnetohydrodynamic simulations of magnetized, turbulent disk formation usually show spiral-like streams of materi... | accretion flows or outflow cavities? uncovering the gas dynamics around lupus 3-mms |
the milky way's progenitor experienced several merger events that left their imprints on the stellar halo, including the gaia-sausage/enceladus. recently, it has been proposed that this event perturbed the proto-disk and gave rise to a metal-rich ([fe/h] > -1), low angular momentum (vφ < 100 km s-1) stellar popul... | the splash without a merger |
hydrodynamical simulations show that circumbinary disks become eccentric, even when the binary is circular. here we demonstrate that, in steady state, the disk's eccentricity behaves as a long-lived free mode trapped by turning points that naturally arise from a continuously truncated density profile. consequently, bot... | long-lived eccentric modes in circumbinary disks |
the hubble sequence provides a useful classification of galaxy morphology at low redshift. however, morphologies are not static, but rather evolve as the growth of structure proceeds through mergers, accretion, and secular processes. we investigate how morphological structures form and evolve in the eagle hydrodynamic ... | the star formation rate and stellar content contributions of morphological components in the eagle simulations |
we present a suite of high-resolution hydrodynamic simulations of binaries immersed in circumbinary accretion discs (cbds). for the first time, we investigate the preferential accretion rate as a function of both eccentricity eb and mass ratio qb in a densely sampled parameter space, finding that when compared with cir... | preferential accretion and circumbinary disc precession in eccentric binary systems |
we consider static neutron stars within the framework of r2 gravity. the neutron fluid is described by three different types of realistic equations of state (soft, moderately stiff, and stiff). using the observational data on the neutron star mass-radius relation, it is demonstrated that the characteristics of the obje... | anisotropic neutron stars in r2 gravity |
jet ejection by accreting black holes is a mass invariant mechanism unifying stellar and supermassive black holes (smbhs) that should also apply for intermediate-mass black holes (imbhs), which are thought to be the seeds from which smbhs form. we present the detection of an off-nuclear imbh of ∼5 × 104 m⊙ located in a... | the powerful jet of an off-nuclear intermediate-mass black hole in the spiral galaxy ngc 2276 |
flares from tidal disruption events are unique tracers of quiescent black holes at the centre of galaxies. the appearance of these flares is very sensitive to whether the star is totally or partially disrupted, and in this paper we seek to identify the critical distance of the star from the black hole (rd) that enables... | the fine line between total and partial tidal disruption events |
the stellar and neutral hydrogen (h i) mass functions at z ∼ 0 are fundamental benchmarks for current models of galaxy evolution. a natural extension of these benchmarks is the two-dimensional distribution of galaxies in the plane spanned by stellar and h i mass, which provides a more stringent test of simulations, as ... | variation of galactic cold gas reservoirs with stellar mass |
low surface brightness galactic stellar haloes provide a challenging but promising path towards unravelling the past assembly histories of individual galaxies. here, we present detailed comparisons between the stellar haloes of milky way-mass disc galaxies observed as part of the dragonfly nearby galaxies survey (dngs)... | a missing outskirts problem? comparisons between stellar haloes in the dragonfly nearby galaxies survey and the tng100 simulation |
cr boo is one of the brightest and most famous am cvn stars showing dwarf nova-type outbursts. previous studies showed different modes of outbursts in this object ranging from the one equivalent to a hydrogen-rich er uma star or wz sge star to a low-amplitude oscillating state. we for the first time identified a bona f... | genuine standstill in the am cvn star cr boo |
although the stellar halo accounts for just ∼1 per cent of the total stellar mass of the milky way, the kinematics of halo stars encode valuable information about the origins and evolution of our galaxy. it has been shown that the high transverse velocity stars in gaia dr2 reveal a double sequence in the hertzsprung-ru... | the tale of the tail - disentangling the high transverse velocity stars in gaia dr2 |
the geometry of the accretion flow in black hole x-ray binaries in the hard state, in particular the position of the disc inner edge, has been a subject of intense debate in recent years. we address this issue by performing a spectral study of simultaneous observations of cyg x-1 in the hard state by nustar and suzaku.... | analysis of nustar and suzaku observations of cyg x-1 in the hard state: evidence for a truncated disc geometry |
we present neutron star interior composition explorer (nicer) observations of the neutron star (ns) low-mass x-ray binary serpens x-1 during the early mission phase in 2017. with the high spectral sensitivity and low-energy x-ray passband of nicer, we are able to detect the fe l line complex in addition to the signatur... | detection of reflection features in the neutron star low-mass x-ray binary serpens x-1 with nicer |
we search the literature for reports on the spectral properties of neutron star low-mass x-ray binaries when they have accretion luminosities between 1034 and 1036 erg s-1, corresponding to roughly 0.01-1 per cent of the eddington accretion rate for a neutron star. we found that in this luminosity range the photon inde... | low-level accretion in neutron star x-ray binaries |
we present global 3d radiation magnetohydrodynamic simulations of accretion onto a 6.62 solar-mass black hole, with quasi-steady-state accretion rates reaching 0.016-0.9 times the critical accretion rate, which is defined as the accretion rate for powering the eddington luminosity, assuming a 10% radiative efficiency, ... | global 3d radiation magnetohydrodynamic simulations of accretion onto a stellar-mass black hole at sub- and near-critical accretion rates |
accreting stellar mass black holes (bhs) routinely exhibit type-c quasi-periodic oscillations (qpos). these are often interpreted as lense-thirring precession of the inner accretion flow, a relativistic effect whereby the spin of the bh distorts the surrounding space-time, inducing nodal precession. the best evidence f... | tomographic reflection modelling of quasi-periodic oscillations in the black hole binary h 1743-322 |
using three-dimensional general relativistic radiation-magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk (≳ {10}7 {{k}}) is truncated near the black hole. hot and less dense regions, of which the gas temperature is ≳ {10}9 {{k}} and more than 10... | formation of overheated regions and truncated disks around black holes: three-dimensional general relativistic radiation-magnetohydrodynamics simulations |
the wide, deep cavities of transition disks are often believed to have been hollowed out by nascent planetary systems. pds 70, a ∼5 myr old transition disk system in which a multi-jupiter-mass planet candidate at 22 au coexists with a ∼30 au gas and ∼60 au dust-continuum gap, provides a valuable case study for this hyp... | pds 70: a transition disk sculpted by a single planet |
hydrodynamical simulations show that a pair of spiral arms can form in the disk around a rapidly growing young star and that the arms are crucial in transporting angular momentum as the disk accretes material from the surrounding envelope1-4. here we report the detection of a pair of symmetric spiral structures in a pr... | spiral structures in an embedded protostellar disk driven by envelope accretion |
galactic dynamical structures are fossil records of the assembly histories of galaxies. by analyzing the cosmological hydrodynamical simulation tng50, we find that a dynamical structure that we call the "hot inner stellar halo", defined by stars on dynamically hot orbits with circularity λz < 0.5 at 3.5 kpc < r ≲... | mass of the dynamically hot inner stellar halo predicts the ancient accreted stellar mass |
numerical simulations have predicted that substructures such as spiral arms can be produced through a gravitationally unstable disk around high-mass young stellar objects (hmysos)1-5. recent high-resolution observations from the atacama large millimeter/submillimeter array have investigated these substructures at a spa... | new maser species tracing spiral-arm accretion flows in a high-mass young stellar object |
the origin of the disk and spheroid of galaxies has been a key open question in understanding their morphology. using the high-resolution cosmological simulation new horizon, we explore kinematically decomposed disk and spheroidal components of 144 field galaxies with masses greater than {10}9 {m}⊙at z = 0.7. the origi... | new horizon: on the origin of the stellar disk and spheroid of field galaxies at z = 0.7 |
it is widely known that giant planets have the capacity to open deep gaps in their natal gaseous protoplanetary discs. it is unclear, however, how gas accretion onto growing planets influences the shape and depth of their growing gaps. we performed isothermal hydrodynamical simulations with the fargo-2d1d code, which a... | influence of planetary gas accretion on the shape and depth of gaps in protoplanetary discs |
we present a large-scale study of stellar rotation for t tauri stars in the orion star-forming complex. we use the projected rotational velocity ( $v\sin (i)$ vsin(i) ) estimations reported by the apogee-2 collaboration as well as individual masses and ages derived from the position of the stars in the hr diagram, cons... | stellar rotation of t tauri stars in the orion star-forming complex |
we address the nature of the giant clumps in high-z galaxies that undergo violent disc instability, distinguishing between long-lived and short-lived clumps. we study the evolution of long-lived clumps during migration through the disc via an analytical model tested by simulations and confront theory with candels-hst o... | clump survival and migration in vdi galaxies: an analytical model versus simulations and observations |
we characterize the contribution from accreted material to the galactic discs of the auriga project, a set of high-resolution magnetohydrodynamic cosmological simulations of late-type galaxies performed with the moving-mesh code arepo. our goal is to explore whether a significant accreted (or ex situ) stellar component... | lessons from the auriga discs: the hunt for the milky way's ex situ disc is not yet over |
our current understanding of the curved space-time around supermassive black holes is based on actively accreting black holes, which make up only ten per cent or less of the overall population. x-ray observations of that small fraction reveal strong gravitational redshifts that indicate that many of these black holes a... | relativistic reverberation in the accretion flow of a tidal disruption event |
we extend previous studies of the tidal truncation of coplanar disks in binary systems to the more general case of noncoplanar disks. as in the prograde coplanar case, lindblad resonances play a key role in tidal truncation. we analyze the tidal torque acting on a misaligned nearly circular disk in a circular orbit bin... | tidal torques on misaligned disks in binary systems |
we present a systematic spectral-timing analysis of a fast appearance/disappearance of a type-b quasi-periodic oscillation (qpo), observed in four neutron star interior composition explorer (nicer) observations of maxi j1348-630. by comparing the spectra of the period with and without the type-b qpo, we found that the ... | nicer uncovers the transient nature of the type-b quasi-periodic oscillation in the black hole candidate maxi j1348-630 |
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