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gamma-ray bursts (grbs) are the brightest explosions in the universe, yet the properties of their energy sources are far from understood. very important clues, however, can be deduced by studying the afterglows of these events. we present observations of grb 130831a and its afterglow obtained with swift, chandra, and m... | grb 130831a: rise and demise of a magnetar at z = 0.5 |
we report on the observations of gamma-ray burst (grb) 190114c by the fermi gamma-ray space telescope and the neil gehrels swift observatory. the early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above... | fermi and swift observations of grb 190114c: tracing the evolution of high-energy emission from prompt to afterglow |
we present the discovery of the radio afterglow of the short $\gamma$-ray burst (grb) 210726a, localized to a galaxy at a photometric redshift of $z\sim 2.4$. while radio observations commenced $\lesssim 1~$day after the burst, no radio emission was detected until $\sim11$~days. the radio afterglow subsequently brighte... | a radio flare in the long-lived afterglow of the distant short grb 210726a: energy injection or a reverse shock from shell collisions? |
the ultrarelativistic jets responsible for prompt and afterglow emission in gamma ray bursts are presumably driven by a central engine that consists of a dense accretion disk around a spinning black hole. we consider such engine, composed of free nucleons, electron-positron pairs, helium nuclei, and cooled by neutrino ... | nucleosynthesis of heavy elements in gamma ray bursts |
since 2009 x-shooter has collected spectroscopy of over 80 gamma-ray burst afterglows with redshifts ranging from 0.05 to 6.3. thanks to its efficiency, broad wavelength coverage (3,000 to 24,800 å), and intermediate spectral resolution (r~8,000) it has become the most efficient tool for gamma-ray burst afterglow spect... | absorption features in the x-shooter grb afterglow sample |
we present a possible theoretical interpretation of the observed afterglow emission of long gamma-ray burst grb 080710. while its prompt grb emission properties are normal, the afterglow light curves in the optical and infrared bands are exceptional in two respects. one is that the observed light curves of different wa... | grb 080710: a narrow, structured jet showing a late, achromatic peak in the optical and infrared afterglow? |
a newly born millisecond magnetar is thought to be the central engine of some gamma-ray bursts (grbs), especially those that present long-lasting x-ray plateau emissions. by solving the field equations, we find that when the rotational speed of the magnetar is approaching the breakup limit, its radius r and moment of i... | the evolutionary effects of the radius and moment of inertia of rapidly rotating neutron stars |
we examine grbs with both fermi-lat and x-ray afterglow data. assuming that the 100mev (lat) emission is radiation from cooled electrons accelerated by external shocks, we show that the kinetic energy of the blast wave estimated from the 100mev flux is 50 times larger than the one estimated from the x-ray flux. this ca... | shedding light on the prompt high efficiency paradox - self consistent modeling of grb afterglows |
we analyze extragalactic extinction profiles derived through gamma-ray burst afterglows, using a dust model specifically constructed on the assumption that dust grains are not immutable but respond, time-dependently, to the local physics. such a model includes core-mantle spherical particles of mixed chemical compositi... | modeling extragalactic extinction through gamma-ray burst afterglows |
measuring grb properties in their rest-frame is crucial to understand the physics at work in gamma-ray bursts. this can only be done for grbs with known redshift. since redshifts are usually measured from the optical spectrum of the afterglow, correlations between prompt and afterglow emissions may introduce biases in ... | connecting prompt and afterglow grb emission i. investigating the impact of optical selection effects in the epi - eiso plane |
we observed gamma-ray burst (grb) 221009a using very long baseline interferomety (vlbi) with the european vlbi network (evn) and the very long baseline array (vlba), over a period spanning from 40 to 262 days after the initial grb. the high angular resolution (~mas) of our observations allowed us, for the second time e... | the expansion of the grb 221009a afterglow |
the tev observations of grb~221009a provided us with a unique opportunity to analyze the contemporaneous phase in which both prompt and afterglow emissions are seen simultaneously. to describe this initial phase of gamma-ray burst afterglows, we suggest a model for a blast wave with an intermittent energy supply. we tr... | the contemporaneous phase of grb afterglows -- application to grb~221009a |
particle-in-cell simulations have unveiled that shock-accelerated electrons do not follow a pure power-law distribution, but have an additional low-energy "thermal" part, which owns a considerable portion of the total energy of electrons. investigating the effects of these thermal electrons on gamma-ray burst (grb) aft... | probing thermal electrons in grb afterglows |
gamma-ray bursts could serve as probes to the extreme physics which power them, yet the origin of their observed prompt emission and their jet structure is still shrouded in mystery. the compton spectrometer and imager (cosi), designed to survey the gamma-ray sky at 0.2-5 mev, could demystify the physics at play throug... | observing gamma-ray bursts with the compton spectrometer and imager |
five long gamma-ray bursts (grbs) have been found to have very high energy (vhe, > 100gev) counterparts. interestingly, more than one emission mechanism has been invoked to explain the vhe counterpart from different events. as a result of this discovery, it has become apparent that we have been missing half of the e... | radio afterglows of very high energy gamma-ray bursts |
the physical mechanism of fast radio bursts (frbs) is still unknown. on 2020 april 28, a special radio burst, frb 200428, was detected and believed to be associated with the galactic magnetar sgr 1935+2154. it confirms that at least some of the frbs were generated by magnetars, although the radiation mechanism continue... | prediction for the multi-band afterglows of frb 200428 and its implication |
a large fraction of γ-ray bursts (grbs) show a plateau phase during the x-ray afterglow emission, which has a physical origin that is still debated. in this work, we select a sample of 30 grbs with simultaneous x-ray and optical data during and after the plateau phase. through a time-resolved spectral analysis of the x... | combined x-ray and optical analysis to probe the origin of the plateau emission in γ-ray burst afterglows |
the environment of a γ-ray burst has an important influence on the evolution of jet dynamics and its afterglow. here we investigate the afterglow polarizations in a stratified medium with the equal arrival time surface (eats) effect. polarizations of multiband afterglows are predicted. the effects of the parameters of ... | afterglow polarizations in a stratified medium with effect of the equal arrival time surface |
gamma-ray bursts (grbs), both long and short, are explosive events whose inner engine is generally expected to be a black hole or a highly magnetic neutron star (magnetar) accreting high-density matter. recognizing the nature of grb central engines, and in particular the formation of neutron stars (nss), is of high ast... | magnetar central engines in gamma-ray bursts follow the universal relation of accreting magnetic stars |
the use of high energy transients such as gamma ray bursts (grbs) as probes of the distant universe relies on the close collaboration between space and ground facilities. in this context, the sino-french mission svom has been designed to combine a space and a ground segment and to make the most of their synergy. on the... | cagire: a wide-field nir imager for the colibri 1.3 meter robotic telescope |
to demonstrate the magnetic energy dissipation via relativistic shocks, we carry out spherically symmetrical one-dimensional special relativistic magnetohydrodynamic simulations of highly magnetized outflows with an adaptive mesh refinement method. we first investigate the details of the dynamical energy dissipation vi... | dynamical energy dissipation of relativistic magnetic bullets |
the australia telescope compact array (atca) observed grb 220627a (fermi gbm team, gcn circ. 32278) at multiple frequencies starting at 04:00 ut on 2022 july 5 (7.3 days post-burst). we detected a radio source with a preliminary flux density of ~0.4 mjy at a central frequency of 17 ghz at ra = 13:25:28.48 dec = -32:25:... | grb 220627a: atca detection of radio counterpart |
at 19:21:43 ut, the swift burst alert telescope (bat) triggered and located grb 200205b (trigger=954519 and 954520). swift slewed to the burst after a short delay. the bat on-board calculated location is ra, dec 107.861, -56.506 which is ra(j2000) = 07h 11m 27s dec(j2000) = -56d 30' 21" with an uncertainty of 3 arcmin ... | grb 200205b: swift detection of a burst with optical counterpart |
i summarize our recent calculations on quark stars (qss), for the purpose of explaining some short gamma-ray bursts characterized by internal plateau in their early x-ray afterglow. according to the present plateau sample, the qs central engine model is demonstrated to more preferred than the original neutron star (ns)... | internal plateau in short grbs and quark stars |
nustar's focusing x-ray optics provide unprecedented sensitivity above 10 kev, enabling late-time observations of gamma-ray burst (grb) afterglows. to date nustar has observed six grbs: grb130427a, grb130925a, grb150201a, grb180720b, grb190114c, and grb190829a. while most nustar data are consistent with the power-law s... | nustar observations of gamma-ray burst afterglows |
gamma-ray bursts (grbs) are the most energetic explosions in the universe. they are collimated, ultra-relativistic outflows which are initially detected as brief flashes of gamma-rays. as the relativistic ejecta starts to interact with the circumburst medium, a pair of shocks are formed where magnetic fields are amplif... | exploring the population of grbs: robust afterglow modelling using gaussian processes |
the shock system that produces the afterglow to grbs consists of a forward- and a reverse-shock. for short grbs, observational evidence for a reverse-shock has been sparse, however, the afterglow to grb 160821b requires a reverse-shock at early times to explain the radio observations. grb 160821b is additionally accomp... | reverse shocks in short gamma-ray bursts -- the case of grb 160821b and prospects as gravitational-wave counterparts |
at 06:53:27 ut, the swift burst alert telescope (bat) triggered on a burst from the soft gamma-ray repeater swift j1555.2-5402 (trigger=1070298). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 238.836, -54.070 which is ra(j2000) = 15h 55m 21s dec(j2000) = -54d 04' 12" with an unc... | swift detection of an outburst from sgr swift j1555.2-5402 |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 211106a, collecting 5.0 ks of photon counting (pc) mode data between t0+39.2 ks and t0+58.2 ks. eight uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. ... | grb 211106a: swift-xrt observations |
we analyse the additional effect on planetary atmospheres of recently detected gamma-ray burst afterglow photons in the range up to 1 tev. for an earth-like atmosphere, we find that there is a small additional depletion in ozone versus that modeled for only prompt emission. we also find a small enhancement of muon flux... | gamma-ray bursts: not so much deadlier than we thought |
the blackcat cubesat will survey the soft x-ray sky, searching for distant gamma-ray bursts (grbs) and other transient phenomena. we present simulations of blackcat observations that illustrate the capabilities of this mission. blackcat will identify and localize bursts to sub-arcminute precision, sending rapid alerts ... | planned observations and science with the blackcat cubesat x-ray transient monitor |
we present the earliest observation and first detection of polarized millimeter emission in a γ-ray burst with alma cycle 7 band 3 (97.5 ghz) observations of grb 190114c. with observations spanning 2.2 to 5.2 hours after the burst, we detect linear polarization in the grb afterglow at 5σ, decreasing from π=(0.87±0.13)%... | alma detection of a linearly polarised reverse shock in grb 190114c |
at 13:59:34 ut, the swift burst alert telescope (bat) triggered and located grb 200829a (trigger=993768). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 251.212, +72.335 which is ra(j2000) = 16h 44m 51s dec(j2000) = +72d 20' 07" with an uncertainty of 3 arcmin (radius, 90% contai... | grb 200829a: swift detection of a burst with an optical afterglow |
we investigate the scenario of a binary system composed by a neutron star (ns) and a main sequence star which has been stripped to be a naked carbon-oxygen core (co core). at a given time, the co core collapses as the supernova (sn) explosion, the hypercritical accretion of the sn ejecta onto the companion ns induces t... | gamma-ray burst from binary star: neutron star and carbon-oxygen core |
we further observed the bright grb 211023a (fermi gbm team 2021, gcn 30958; lesage et al. 2021, gcn 30965; n. di lalla et al. 2021, gcn 30961; ursi et al. 2021, gcn 30969; and ridnaia et al. 2021, gcn 31022) with 1.3m devasthal fast optical telescope (dfot) located at devasthal observatory of aryabhatta research instit... | grb 211023a: continued 1.3m dfot optical observations and possible jet break |
neutron-star (ns) mergers provide unique environments for mass accretion, ejection, and r-process nucleosynthesis. information about the ns merger and its outcome is encoded in the observed electromagnetic (em) signatures, such as gamma ray bursts, kilonova and afterglow emissions. to boost the scientific return from t... | simulating neutron star merger remnant outflows with a two-moment neutrino scheme |
at 07:53:05 ut, the swift burst alert telescope (bat) triggered and located emission from the source 4u 1630-472 (a.k.a. swift j1633.8-4724a) (trigger=1160641). swift slewed immediately to the source. the bat on-board calculated location is ra, dec 248.508, -47.365 which is ra(j2000) = 16h 34m 02s dec(j2000) = -47d 21'... | trigger 1160641: swift detection of 4u 1630-472 (a.k.a. swift j1633.8-4724a) |
as we further our studies on gamma-ray bursts (grbs), both on theoretical models and observational tools, more and more options begin to open for exploration of its physical properties. as transient events primarily dominated by synchrotron radiation, it is expected that the synchrotron photons emitted by grbs should p... | afterglow polarization from off-axis grb jets |
we analyzed 500 grb optical afterglows with known redshifts, thus building the most comprehensive sample of optical light curves (lcs) to date by searching the literature for all grbs detected between 1997 may and 2021 may by several satellites, e.g., the swift ultraviolet/optical telescope (uvot), and ground-based tel... | vizier online data catalog: optical lc fit parameters for 179 grbs (dainotti+, 2022) |
dark grbs constitute a significant fraction of the grb population. in this paper, we present the multiwavelength analysis of an intense two-episodic grb 150309a observed early on to ~114 days post-burst. despite the strong gamma-ray emission, no optical afterglow was detected for this burst. however, we discovered near... | revealing characteristics of dark grb 150309a: dust extinguished or high-z? |
"at 03:27:45.98 ut on 16 september 2023, the fermi gamma-ray burst monitor (gbm) triggered on trigger 716527670/230916144 as a grb with 64% confidence). this trigger was later followed up by goto (vail et al., gcn 34730), identifying a candidate afterglow (at 2023sva) and suggested it was the counterpart. careful inspe... | fermi gbm statement for trigger 716527670/230916144 |
in this work, we have modeled the hydrodynamic evolution of the grbs fireball in violent interaction with the external medium (the ism) surrounding the burst source by assuming a power law distribution of the accelerated relativistic electrons. for this purpose, a computer code based only on the contribution of the pre... | grb afterglow light curves from a hydrodynamic model |
the large area polarimeter, or leap, is a proposed mission concept that will radically improve our understanding of some of the most energetic phenomena in our universe by exposing the underlying physics governing astrophysical jets and the extreme environment surrounding newborn compact objects. leap will do this by m... | the leap gamma-ray burst polarimeter: an overview |
high-redshift gamma-ray bursts (grbs) are useful to probe the early universe, but only a few candidates have been detected so far. here, we report the optical and near-infrared observations of the afterglow of a relatively high-redshift event grb 220101a, which was triggered on new year's day of 2022, and therefore ref... | optical and near-infrared observations of the distant but bright "new year\'s burst" grb 220101a |
the plateau phase in radio afterglows has been observed in very few gamma-ray bursts (grbs), and in this paper, 27 radio light curves with plateau phases were acquired from the published literature. we obtain the related parameters of the radio plateau, such as temporal indexes during the plateau phase (α 1 and α 2), b... | radio plateaus in gamma-ray burst afterglows and their application in cosmology |
this poster is meant to complement the presentation about the ixpe observation of grb 221009a. here, we provide more details on data analysis and interpretation. grb 221009a is an exceptionally bright gamma-ray burst (grb) that reached earth on 2022 october 9 after traveling through the dust of the milky way. the imagi... | the ixpe view of grb221009a |
despite 40 years of observations, grb prompt emission is still subject to intense debate. several dissipation models are employed to explain the observed non-thermal spectrum, like internal shocks, sub-photospheric dissipation, magnetic reconnection. all these models are indistinguishable for the available data. the di... | constrains on the physics of prompt emission from a distant and energetic gamma-ray burst. |
in 50 years of observations, grb 221009a is unequivocally the brightest gamma-ray burst (grb) every detected. due to its nearby distance, at redshift z=0.151, it is an incredibly rare event with a rate of once in a century. the nearby distance combined with its fantastic energy release provided an unprecedented opportu... | the early afterglow of the brightest gamma-ray burst of all time |
at 02:48:59 ut, the swift burst alert telescope (bat) triggered and located grb 201024a (trigger=1001514). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 125.948, +3.377 which is ra(j2000) = 08h 23m 47s dec(j2000) = +03d 22' 38" with an uncertainty of 3 arcmin (radius, 90% contai... | grb 201024a: swift detection of a burst with an optical afterglow |
during its four year long all sky survey, the erosita instrument on spectrum-x-gamma will perform the deepest all sky survey of the x-ray (0.2-8 kev) sky. the survey consists of a total of eight scans of the whole celestial sphere, which last six months each. each survey is designed as a slew survey where the spectrum-... | erosita observations of transient sources |
in this work we study the afterglow light curve of grb 171205a; this long burst was discovered by the burst alert telescope (bat) on board neil gehrels swift and konus-wind, respectively. the x-ray telescope (xrt) began observing the burst at 144.7 seconds and ended at 6748135.04 seconds after the bat trigger. the whol... | a stepped afterglow light curve of grb 171205a |
the swift/uvot began settled observations of the field of grb 220627a 130224 s after the lat trigger (di lalla, et al., gcn circ. 32283). no optical afterglow consistent with the optical position (de wet et al., gcn circ. 32289, izzo et al., gcn circ. 33391) or x-ray afterglow (gropp et al., gcn circ. 32296) is detecte... | grb 220627a: swift/uvot upper limits |
observations of the long-lived x-ray plateau in short gamma-ray burst (sgrb) afterglow suggest that a portion of binary neutron star mergers would leave behind a rapidly spinning, strongly magnetized neutron star (millisecond magnetar). the new-born magnetar may undergo large deformation due to magnetic distortion or u... | identifying gravitational wave emission signature in electromagnetic observations of short gamma-ray bursts |
we present the broadband numerical modeling of afterglows for two remarkably bright long gamma-ray bursts (grbs), grb 050820a and grb 070125, with a wide range of observations from the radio band to the x-ray band. in our work, we fit light curves and constrain physical parameters using a standard forward shock model f... | on the jet structures of grb 050820a and grb 070125 |
in a previous article, we argued that angular non-stationarities of gamma-ray burst (grb) jets can result in a statistical connection between the angle values deduced from jet break times and the variabilities of prompt light curves. the connection should be an anticorrelation if luminosity densities of jets follow a p... | statistical search for angular non-stationarities of long gamma-ray burst jets using swift data |
the temporal behavior of the very dim optical afterglow of grb 080503 is at odds with the regular forward shock afterglow model and a sole kilonova component responsible for optical emission has been speculated in some literature. here we analyze the optical afterglow data available in archive and construct time-resolv... | grb 080503: a very early blue kilonova and an adjacent nonthermal radiation component |
a large fraction of the baryons at low redshift are undetected and likely reside in the tenuous, hot intergalactic medium (igm). one way to probe the missing baryons is through their absorption of bright sources. the anomalous absorption excess in the x-ray afterglows of gamma-ray bursts (grbs) has been suggested to re... | absorption of gamma-ray burst x-ray afterglows by the missing baryons: confronting observations with cosmological simulations |
we consider the question of entanglement conservation in the context of the er=epr correspondence equating quantum entanglement with wormholes. in quantum mechanics, the entanglement between a system and its complement is conserved under unitary operations that act independently on each; er=epr suggests that an analogo... | entanglement conservation, er=epr, and a new classical area theorem for wormholes |
we connect topological changes that can occur in $3$-space via surgery, with black hole formation, the formation of wormholes and new generalizations of these phenomena, including relationships between quantum entanglement and wormhole formation. by considering the initial manifold as the $3$-dimensional spatial sectio... | topological surgery in cosmic phenomena |
many of the most exciting open problems in high-energy physics are related to the behavior and ultimate nature of gravity and spacetime. in this dissertation, several categories of new results in quantum and classical gravity are presented, with applications to our understanding of both quantum field theory and cosmolo... | defining gravity: effective field theory, entanglement, and cosmology |
the field test of distributed acoustic sensing (das) conducted at garner valley, california on september 11-12, 2013 provided a continuous overnight record of ambient noise. the das array recorded ground motions every one meter of optical cable that was arranged approximately in the shape of a rectangle with dimensions... | properties of noise cross correlation functions obtained from a distributed acoustic sensing (das) array at garner valley, california |
our paper introduces a new technique for diagnosis of various heart diseases without the need of highly experts to investigate the electrocardiogram (ecg). using the same electrodes of the ecg machine, it will be able to transmit directly the electrical activity inside the heart to a moving picture. our technique is ba... | reconstruction of depolarization pattern in myocardial infarction cases using two cascaded stages of artificial neural networks |
69227 deaths, 374643 injured, 17923 people missing, direct economic losses 845.1 billion, and a large number houses collapse were caused by wenchuan ms8 earthquake in sichuan province on may 12, 2008, how to reproduce characteristics of its strong ground motion and predict its intensity distribution, which have importa... | numerical simulation analysis on wenchuan seismic strong motion in hanyuan region |
on 12 may, 2008, the sichuan province in china suffered the catastrophic wenchuan earthquake (ms 8). prior to the event, a large number of small to moderate earthquakes occurred in the area were recorded at stations of sichuan seismic network (scsn). the wave data were collected during the years 2006-2008, the fourier ... | lg attenuation and site response in the sichuan basin and the bayan har block before the 2008 ms8.0 wenchuan earthquake |
full-waveform inversion (fwi) is an effective method for imaging subsurface properties using sparsely recorded data. it involves solving a wave propagation problem to estimate model parameters that accurately reproduce the data. recent trends in fwi have led to the development of extended methodologies, among which sou... | full waveform inversion and lagrange multipliers |
earth introduces strong attenuation and dispersion to propagating waves. the time-fractional wave equation with very small fractional exponent, based on kjartansson's constant-q theory, is widely recognized in the field of geophysics as a reliable model for frequency-independent q anelastic behavior. nonetheless, the n... | compressing the memory variables in constant-q viscoelastic wave propagation via an improved sum-of-exponentials approximation |
solar metallicity — the fraction per unit mass that is composed of elements heavier than he — is a critical and fundamental quantity indicative of the history and future evolution of the sun. over the last decade spectroscopic observations of the solar photosphere using inversion techniques of increasing sophistication... | solar metallicity derived from in-situ solar wind composition |
non-hermitian systems offer new platforms for unusual physical properties that can be flexibly manipulated by redistribution of the real and imaginary parts of refractive indices, whose presence breaks conventional wave propagation symmetries, leading to asymmetric reflection and symmetric transmission with respect to ... | machine learning for knowledge acquisition and accelerated inverse-design for non-hermitian systems |
in this paper, we are concerned with the 2d and 3d geometric shape generation by prescribing a set of characteristic values of a specific geometric body. one of the major motivations of our study is the 3d human body generation in various applications. we develop a novel method that can generate the desired body with c... | an inverse scattering approach for geometric body generation: a machine learning perspective |
observational insights into dynamo processes are gleaned from the cyclic variations of solar differential rotation known as torsional oscillations. these oscillations are closely intertwined with the evolution of the magnetic field on the solar surface throughout the solar cycle, and they can be observed using heliosei... | unveiling the evolution of solar differential rotation across two solar cycles |
microscopic traffic models describe how cars interact with their neighbors in an uninterrupted traffic flow and are frequently used for reference in advanced vehicle control design. in this paper, we propose a novel mechanical system inspired microscopic traffic model using a mass-spring-damper-clutch system. this mode... | a new microscopic traffic model using a spring-mass-damper-clutch system |
quantitative photoacoustic tomography (qpat) is an imaging technique aimed at estimating chromophore concentrations inside tissues from photoacoustic images, which are formed by combining optical information and ultrasonic propagation. the application of qpat as a transcranial imaging modality is complicated by shear w... | coupled elastic-acoustic modelling for quantitative photoacoustic tomography |
the meridional circulation and other large scale flows are important features of the sun's internal structure and are closely connected to the transport of momentum and magnetic flux throughout the solar interior, and in effect to the solar magnetic cycle. therefore, reliable measurements of such flows is crucially imp... | meridional-flow inversions using realistic 3-d sensitivity kernels |
observations of the sun in the visible spectral range belong to standard measurements obtained by instruments both on the ground and in the space. nowadays, both nearly continuous full-disc observations with medium resolution and dedicated campaigns of high spatial, spectral and/or temporal resolution constitute a holy... | exploiting solar visible-range observations by inversion techniques: from flows in the solar subsurface to a flaring atmosphere |
normal-mode coupling is a helioseismic technique that uses measurements of mode eigenfunctions to infer the interior structure of the sun. this technique has led to insights into the evolution and structure of toroidal flows in the solar interior. here, we validate an inversion algorithm for normal-mode coupling by gen... | validating inversions for toroidal flows using normal-mode coupling |
tomography was a non-destructive method for investigating the internal structure of an object, usually used to find internal anomalies caused by differences in the physical parameters. the fresnel volume tomography method was an alternative method for reconstructing the image of an object using travel times, whereas th... | ultrasonic tomography of core plug using fresnel volume approach |
diffraction tomography is a noninvasive technique that estimates the refractive indices of unknown objects and involves an inverse-scattering problem governed by the wave equation. recent works have shown the benefit of nonlinear models of wave propagation that account for multiple scattering and reflections. in partic... | diffraction tomography with helmholtz equation: efficient and robust multigrid-based solver |
digital holography is a 3d imaging technique by emitting a laser beam with a plane wavefront to an object and measuring the intensity of the diffracted waveform, called holograms. the object's 3d shape can be obtained by numerical analysis of the captured holograms and recovering the incurred phase. recently, deep lear... | dh-gan: a physics-driven untrained generative adversarial network for 3d microscopic imaging using digital holography |
wind speed retrieval at sea surface is of primary importance for scientific and operational applications. besides weather models, in-situ measurements and remote sensing technologies, especially satellite sensors, provide complementary means to monitor wind speed. as sea surface winds produce sounds that propagate unde... | learning-based temporal estimation of in-situ wind speed from underwater passive acoustics |
this paper identifies certain interesting mathematical problems of stochastic quantization type in the modeling of laser propagation through turbulent media. in some of the typical physical contexts the problem reduces to stochastic schrodinger equation with space-time white noise of gaussian, poisson and levy type. we... | stochastic quantization of laser propagation models |
full waveform inversion is a high-resolution subsurface imaging technique, in which full seismic waveforms are used to infer subsurface physical properties. we present a novel, target-enclosing, full-waveform inversion framework based on an interferometric objective function. this objective function exploits the equiva... | target-enclosing inversion using an interferometric objective function |
in this paper, we refine a previously developed acoustic source filter, improving its reliability and extending its capabilities. we demonstrate how to fine-tune the filter to meet observational constraints and focus on specific wave-front speeds. this refinement enables discrimination of acoustic source depths and tra... | identifying acoustic wave sources on the sun. ii. improved filter techniques for source wavefield seismology |
we present anseicca, an open-source package for forward and inverse modelling of seis- mic ambient noise cross-correlations at local scales, where the effects of earth's sphericity are negligible. the package implements a nonlinear finite-frequency inversion technique wherein measurements of cross-correlation energy ar... | anseicca: a python package for seismic ambient noise source inversion by cross-correlation modelling |
data-centric inverse problems are a process of inferring physical attributes from indirect measurements. full-waveform inversion (fwi) is a non-linear inverse problem that attempts to obtain a quantitative physical model by comparing the wave equation solution with observed data, optimizing an objective function. howev... | a graph-space optimal transport approach based on kaniadakis κ-gaussian distribution for inverse problems related to wave propagation |
the kagome superconductors kv3sb5 , rbv3sb5 , and csv3sb5 are known to display charge density wave (cdw) order which impacts the topological characteristics of their electronic structure. details of their structural ground states and how they evolve with temperature are revealed here using single crystal x-ray crystall... | structural evolution of the kagome superconductors a v3sb5 (a = k, rb, and cs) through charge density wave order |
radial profiles of density fluctuations and the radial electric field, er, have been measured using doppler reflectometry during the post-pellet enhanced confinement phase achieved, under different heating power levels and magnetic configurations, during the 2018 w7-x experimental campaign. a pronounced er-well is meas... | radial electric field and density fluctuations measured by doppler reflectometry during the post-pellet enhanced confinement phase in w7-x |
we propose a general method to self-consistently study the quasistationary evolution of the magnetic field in the cores of neutron stars. the traditional approach to this problem is critically revised. our results are illustrated by calculation of the typical timescales for the magnetic field dissipation as functions o... | evolution of the magnetic field in neutron stars |
we analyze the fundamental coherence limit of a nano-object with an embedded spin in a stern-gerlach interferometer. this limit stems from the which-path information provided by the object's rotational degrees of freedom due to the evolution of their quantum uncertainty. we show that such interferometry is straightforw... | quantum uncertainty limit for stern-gerlach interferometry with massive objects |
under normal conditions in a neutron-star (ns) crust, ions are locked in place in the crustal lattice and only electrons are mobile, and magnetic-field evolution is thus directly related to the electron velocity. the evolution, however, builds magnetic stresses that can become sufficiently large for the crust to exceed... | magnetic-field evolution in a plastically failing neutron-star crust |
here we present details of an operator-split, implicit-explicit numerical scheme for the solution of the gyrokinetic-poisson system of equations in the local limit. this scheme has been implemented in a new code called stella, which is capable of evolving electrostatic fluctuations with full kinetic electron effects an... | stella: an operator-split, implicit-explicit δf-gyrokinetic code for general magnetic field configurations |
in the interior of neutron stars, the induction equation regulates the long-term evolution of the magnetic fields by means of resistivity, hall dynamics and ambipolar diffusion. despite the apparent simplicity and compactness of the equation, the dynamics it describes is not trivial and its understanding relies on accu... | a simflowny-based high-performance 3d code for the generalized induction equation |
in this paper, we study the thermal evolution of three types of quantum correlations under the homogeneous and inhomogeneous spin star hamiltonian. it is shown that quantum discord (qd) is more stable than the other measures in the thermal regime, but concurrence is more efficient when the hamiltonian parameters are em... | thermal quantum correlations in a two-dimensional spin star model |
simulating the long-term evolution of temperature and magnetic fields in neutron stars is a major effort in astrophysics, having significant impact in several topics. a detailed evolutionary model requires, at the same time, the numerical solution of the heat diffusion equation, the use of appropriate numerical methods... | magneto-thermal evolution of neutron stars with coupled ohmic, hall and ambipolar effects via accurate finite-volume simulations |
fast radio bursts are millisecond-duration radio pulses of extragalactic origin. a recent statistical analysis has found that the burst energetics of the repeating source frb 121102 follow a power law, with an exponent that is curiously consistent with the gutenberg-richter law for earthquakes. this hints that repeat b... | young magnetars with fracturing crusts as fast radio burst repeaters |
we present ultraviolet (uv), optical and infrared photometry and optical spectroscopy of the type ic superluminous supernova (slsn) gaia16apd (=sn 2016eay), covering its evolution from 26 d before the g-band peak to 234.1 d after the peak. gaia16apd was followed as a part of the not unbiased transient survey (nuts). it... | gaia16apd - a link between fast and slowly declining type i superluminous supernovae |
magnetic reconnection is a process that contributes significantly to plasma dynamics and energy transfer in a wide range of plasma and magnetic field regimes, including inertial confinement fusion experiments, stellar coronae, and compact, highly magnetized objects like neutron stars. laboratory experiments in differen... | field reconstruction from proton radiography of intense laser driven magnetic reconnection |
the large-scale magnetic fields of stars can be obtained with the zeeman doppler imaging (zdi) technique, but their interpretation is still challenging as the contribution of the small-scale field or the reliability of the reconstructed field properties is still not fully understood. to quantify this, we use 3d non-pot... | observing the simulations: applying zdi to 3d non-potential magnetic field simulations |
the long-term evolution of the internal, strong magnetic fields of neutron stars needs a specific numerical modelling. the diversity of the observed phenomenology of neutron stars indicates that their magnetic topology is rather complex and 3d simulations are required, for example, to explain the observed bursting mech... | 3d code for magneto-thermal evolution in isolated neutron stars, matins: the magnetic field formalism |
the tayler instability is an important but poorly studied magnetohydrodynamic (mhd) instability that likely operates in stellar interiors. the non-linear saturation of the tayler instability is poorly understood and has crucial consequences for dynamo action and angular momentum transport in radiative regions of stars.... | magnetohydrodynamic simulations of the tayler instability in rotating stellar interiors |
context. the magneto-rotational instability (mri) has been proposed as a mechanism to transport angular momentum (am) and chemical elements in theoretical stellar models.aims: using as a prototype a massive star of 15 m⊙ with solar metallicity, we explore the effects of the mri on the evolution of massive stars.methods... | the magneto-rotational instability in massive stars |
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