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fast radio bursts (frbs) are an emerging class of short and bright radio transients whose sources remain enigmatic. within the galactic centre, the non-detection of pulsars within the inner ∼10 pc has created a missing pulsar problem that has intensified with time. with all reserve, we advance the notion that the two p... | dark matter-induced collapse of neutron stars: a possible link between fast radio bursts and the missing pulsar problem. |
we have performed a new search for radio pulsars in archival data of the intermediate and high galactic latitude parts of the southern high time resolution universe pulsar survey. this is the first time the entire dataset has been searched for binary pulsars, an achievement enabled by gpu-accelerated dedispersion and p... | the high time resolution universe survey - xiv. discovery of 23 pulsars through gpu-accelerated reprocessing |
we present a spectral study of the ultraluminous be/x-ray transient pulsar swift j0243.6+6124 using neutron star interior composition explorer (nicer) observations during the system’s 2017-2018 giant outburst. the 1.2-10 kev energy spectrum of the source can be approximated with an absorbed cutoff power-law model. we d... | an evolving broad iron line from the first galactic ultraluminous x-ray pulsar swift j0243.6+6124 |
photoelectrochemical (pec) water splitting to produce hydrogen fuel was first reported 50 years ago1, yet artificial photosynthesis has not become a widespread technology. although planar si solar cells have become a ubiquitous electrical energy source economically competitive with fossil fuels, analogous pec devices h... | water splitting with silicon p-i-n superlattices suspended in solution |
nicer, swift/bat, and maxi have continued to monitor the outburst of the be/x-ray binary pulsar ls v +44 17 (also known as rx j0440.9+4431). the source peaked at a pulse-phase averaged count rate of ~1500 c/s in the nicer energy band and is now slowly decreasing in count rate. | continued x-ray monitoring of ls v +44 17 with nicer, swift/bat, and maxi |
radiation detectors based on cadmium zinc telluride (czt) compounds are becoming popular solutions thanks to their high detection efficiency, room temperature operation, and to their reliability in compact detection systems for medical, astrophysical, or industrial applications. however, despite a huge effort to improv... | advances in high-energy-resolution cdznte linear array pixel detectors with fast and low noise readout electronics |
a new measurement of a spatially extended gamma-ray signal from the center of the andromeda galaxy (m31) has recently been published by the fermi-lat collaboration, reporting that the emission broadly resembles the so-called galactic center excess (gce) of the milky way (mw). the weight of the evidence is steadily accu... | millisecond pulsar origin of the galactic center excess and extended gamma-ray emission from andromeda: a closer look |
recent ultra-intense lasers of subcritical fields and proposed x-ray polarimetry for highly magnetized neutron stars of supercritical fields have attracted attention to vacuum birefringence, a unique feature of the nonlinear vacuum under strong electromagnetic fields. we propose a formulation of the vacuum birefringenc... | vacuum birefringence at one-loop in a supercritical magnetic field superposed with a weak electric field and application to pulsar magnetosphere |
recent measurements of neutron star mass from several candidates (psr j 1614 -2230 , psr j 0348 +0432 , msp j 0740 +6620 ) set the lower bound on the maximum possible mass for this class of compact objects ∼2 m⊙ . existence of stars with high mass brings the possibility of existence of exotic matter (hyperons, meson co... | dense matter equation of state of a massive neutron star with antikaon condensation |
we present new, tight, constraints on the cosmological background of gravitational waves (gws) using the latest measurements of cmb temperature and polarization anisotropies provided by the planck, bicep2 and keck array experiments. these constraints are further improved when the gw contribution neffgw to the effective... | updated constraints and forecasts on primordial tensor modes |
gravitational wave (gw) astronomy using a pulsar timing array requires high-quality millisecond pulsars (msps), correctable interstellar propagation delays, and high-precision measurements of pulse times of arrival. here we identify noise in timing residuals that exceeds that predicted for arrival time estimation for m... | the nanograv nine-year data set: excess noise in millisecond pulsar arrival times |
accretion of matter onto a magnetic, rotating object can be strongly affected by the interaction with its magnetic field. this occurs in a variety of astrophysical settings involving young stellar objects, white dwarfs, and neutron stars. as matter is endowed with angular momentum, its inflow toward the star is often m... | a universal relation for the propeller mechanisms in magnetic rotating stars at different scales |
ngc 300 ulx1 is a newly identified ultra-luminous x-ray pulsar. the system is associated with the supernova impostor sn 2010da that was later classified as a possible supergiant be x-ray binary. in this work we report on the spin period evolution of the neutron star based on all the currently available x-ray observatio... | ngc 300 ulx1: a test case for accretion torque theory |
in the canonical picture of pulsars, radio emission arises from a narrow cone centred on the star's magnetic axis but many basic details remain unclear. we use high-quality polarization data taken with the parkes radio telescope to constrain the geometry and emission heights of pulsars showing interpulse emission, and ... | on the beam properties of radio pulsars with interpulse emission |
we calculate the dispersion measure (dm) contributed by the intergalactic medium (igm) to the total measured dm for fast radio bursts (frbs). we use the marenostrum instituto de ciencias del espacio (mice) onion universe simulation to track the evolution of the dark matter particle density over a large range of redshif... | estimates of fast radio burst dispersion measures from cosmological simulations |
we present x-ray, ultraviolet, and optical observations of 1rxs j154439.4-112820, the most probable counterpart of the unassociated fermi-lat source 3fgl j1544.6-1125. the optical data reveal rapid variability, which is a feature of accreting systems. the x-rays exhibit large-amplitude variations in the form of fast sw... | identification of the high-energy gamma-ray source 3fgl j1544.6-1125 as a transitional millisecond pulsar binary in an accreting state |
dark matter annihilations taking place in nearby subhalos could appear as gamma-ray sources without detectable counterparts at other wavelengths. in this study, we consider the collection of unassociated gamma-ray sources reported by the fermi collaboration in an effort to identify the most promising dark matter subhal... | examining the fermi-lat third source catalog in search of dark matter subhalos |
fast-spinning strongly magnetized newborn neutron stars (nss), including nascent magnetars, are popularly implemented as the engine of luminous stellar explosions. here, we consider the scenario that they power various stripped-envelope (se) supernovae (sne), not only superluminous sne ic but also broad-line (bl) sne i... | multi-messenger tests for fast-spinning newborn pulsars embedded in stripped-envelope supernovae |
we present the first fully self-consistent three dimensional model of a neutron star's magnetic field, generated by electric currents in the star's crust via the hall effect. we find that the global-scale field converges to a dipolar hall-attractor state, as seen in recent axisymmetric models, but that small-scale feat... | three dimensional simulation of the magnetic stress in a neutron star crust |
we present the measurements of scatter broadening timescales ({{τ }sc}) for 124 pulsars at 327 mhz using the upgraded ooty radio telescope. these pulsars lie in the dispersion measure range of 37-503 pc cm-3 and declination (δ) range of -57°\lt δ \lt 60{}^\circ . new {{τ }sc} estimates for 58 pulsars are presented, inc... | scatter broadening measurements of 124 pulsars at 327 mhz |
we report on the results of a recent blind search survey for gamma-ray pulsars in fermi large area telescope (lat) data being carried out on the distributed volunteer computing system, einstein@home. the survey has searched for pulsations in 118 unidentified pulsar-like sources, requiring about 10,000 years of cpu core... | the einstein@home gamma-ray pulsar survey. i. search methods, sensitivity, and discovery of new young gamma-ray pulsars |
we present the data analysis pipeline, commissioning observations, and initial results from the greenburst fast radio burst (frb) detection system on the robert c. byrd green bank telescope (gbt) previously described by surnis et al., which uses the 21-cm receiver observing commensally with other projects. the pipeline... | initial results from a real-time frb search with the gbt |
after spending almost a decade in a radio-quiet state, the anomalous x-ray pulsar xte j1810-197 turned back on in early 2018 december. we have observed this radio magnetar at 1.5 ghz with nearly daily cadence since the first detection of radio re-activation on 2018 december 8. in this paper, we report on the current ti... | spin frequency evolution and pulse profile variations of the recently re-activated radio magnetar xte j1810-197 |
the phenomena of the deconfinement of hadronic matter into quark matter at high density, relevant to hybrid star (hs) cores, is studied in the present work. the effective chiral model describes the pure hadronic phase while for the quark phase the mit bag model is chosen with density-dependent bag pressure. phase trans... | properties of hybrid stars with a density-dependent bag model |
we present a model for atmospheric wind circulation in binary millisecond pulsar (msp) companions, showing how the optical light curve (lc) and radial velocities are sensitive to the wind flow, causing lc orbital phase shifts and asymmetries, as observed for several "spider" msps. velocity widths of spectral lines offe... | atmospheric circulation on black widow companions |
pulsar timing array (pta) searches for a gravitational-wave background (gwb) typically include time-correlated "red" noise models intrinsic to each pulsar. using a simple simulated pta data set with an injected gwb signal we show that the details of the red noise models used, including the choice of amplitude priors an... | model dependence of bayesian gravitational-wave background statistics for pulsar timing arrays |
the x-ray radiation produced on the surface of accreting magnetised neutron stars is expected to be strongly polarised. a swing of the polarisation vector with the pulsar phase gives a direct measure of the source inclination and magnetic obliquity. in the case of rapidly rotating millisecond pulsars, the relativistic ... | relativistic rotating vector model for x-ray millisecond pulsars |
context. radio pulses from pulsars are affected by plasma dispersion, which results in a frequency-dependent propagation delay. variations in the magnitude of this effect lead to an additional source of red noise in pulsar timing experiments, including pulsar timing arrays (ptas) that aim to detect nanohertz gravitatio... | dispersion measure variability for 36 millisecond pulsars at 150 mhz with lofar |
the strong interaction at low-energy scales determines the equation of state (eos) of supranuclear matters in neutron stars (nss). it is conjectured that the bulk dense matter may be composed of strangeons, which are quark clusters with nearly equal numbers of u, d, and s quarks. to characterize the strong-repulsive in... | oscillation modes and gravitational waves from strangeon stars |
by applying a relativistic mean-field description of neutron star matter with density dependent couplings, we analyze the properties of two different matter compositions: nucleonic matter with δ baryons and nucleonic matter with hyperons and δ baryons. the δ -meson couplings are allowed to vary within a wide range of v... | δ baryons in neutron stars |
we search for transient sources in a sample of ultraluminous x-ray sources (ulxs) from the 3xmm-dr4 release of the xmm-newton serendipitous source catalogue in order to find candidate neutron star ulxs alternating between an accreting state and the propeller regime, in which the luminosity drops dramatically. by examin... | searching for propeller-phase ulxs in the xmm-newton serendipitous source catalogue |
we have identified 2xmm j125556.57+565846.4, at a distance of 600 pc, as a binary system consisting of a normal star and a probable dormant neutron star. optical spectra exhibit a slightly evolved f-type single star, displaying periodic doppler shifts with a 2.76-d keplerian circular orbit, with no indication of light ... | probable dormant neutron star in a short-period binary system |
neutron stars host the strongest magnetic fields that we know of in the universe. their magnetic fields are the main means of generating their radiation, either magnetospheric or through the crust. moreover, the evolution of the magnetic field has been intimately related to explosive events of magnetars, which host str... | magnetic field evolution in neutron star crusts: beyond the hall effect |
context. extended gamma-ray emission, interpreted as halos formed by the inverse-compton scattering of ambient photons by electron-positron pairs, is observed toward a number of middle-aged pulsars. the physical origin and actual commonness of the phenomenon in the galaxy remain unclear. the conditions of pair confinem... | are pulsar halos rare?. modeling the halos around psrs j0633+1746 and b0656+14 in the light of fermi-lat, hawc, and ams-02 observations and extrapolating to other nearby pulsars |
the moon and mercury both have permanently shaded regions (psrs) at their poles, which are locations that do not see the sun for geologically long periods of time. the psrs of the moon and mercury have very cold temperatures (<120 k) and as a consequence act as traps for volatile materials. volatile enhancements hav... | a tale of two poles: toward understanding the presence, distribution, and origin of volatiles at the polar regions of the moon and mercury |
present paper provides a new model of anisotropic strange star corresponding to the exterior schwarzschild metric. the einstein field equations have been solved by utilizing the krori-barua (kb) ansatz (krori and barua in j. phys. a, math. gen. 8:508, 1975) in presence of quintessence field characterized by a parameter... | singularity-free anisotropic strange quintessence star |
the large-scale development and utilization of coal resources have brought great challenges to the ecological environment of coal-mining areas. therefore, this paper has used scientific and effective methods to monitor and evaluate whether changes in ecological environment quality in coal-mining areas are helpful to al... | remote-sensing evaluation and temporal and spatial change detection of ecological environment quality in coal-mining areas |
we present new discoveries and results from long-term timing of 72 pulsars discovered in the pulsar arecibo l-band feed array (palfa) survey, including precise determination of astrometric and spin parameters, and flux density and scatter broadening measurements at 1.4 ghz. notable discoveries include two young pulsars... | study of 72 pulsars discovered in the palfa survey: timing analysis, glitch activity, emission variability, and a pulsar in an eccentric binary |
the strong interactions at low energy scales determine the state of the supranuclear matter in the pulsar-like compact objects. it is proposed that the bulk strong matter could be composed of strangeons, which are quark clusters with a nearly equal number of three light-flavour quarks. in this work, to characterize the... | rotation and deformation of strangeon stars in the lennard-jones model |
in the present paper we propose a new model of an anisotropic strange star which admits the chaplygin equation of state. the exterior spacetime is described by a schwarzschild line element. the model is developed by assuming the finch-skea ansatz (finch and skea in class. quantum gravity 6:467, 1989. we obtain the mode... | strange star admitting chaplygin equation of state in finch-skea spacetime |
since the day of its explosion, supernova (sn) 1987a has been closely monitored to study its evolution and to detect its central compact relic. in fact, the formation of a neutron star is strongly supported by the detection of neutrinos from the sn. however, besides the detection in the atacama large millimeter/submill... | additional evidence for a pulsar wind nebula in the heart of sn 1987a from multiepoch x-ray data and mhd modeling |
gamma-ray observations have shown pulsars to be efficient converters of rotational energy into gev photons and it is of wide-ranging interest to determine their contribution to the gamma-ray background. we arrive at flux predictions from both the young (<~ myr) and millisecond (~gyr) galactic pulsar populations. we ... | young and millisecond pulsar gev gamma-ray fluxes from the galactic center and beyond |
pulsar glitches provide a unique way to study neutron star microphysics because short post-glitch dynamics are directly linked to strong frictional processes on small scales. to illustrate this connection between macroscopic observables and microphysics, we review calculations of vortex interactions focusing on kelvin ... | glitch rises as a test for rapid superfluid coupling in neutron stars |
using a milky way (mw) double neutron star (dns) merger rate of 210 myr-1, as derived by the laser interferometer gravitational-wave observatory (ligo), we demonstrate that the laser interferometer space antenna (lisa) will detect on average 240 (330) dnss within the mw for a 4 yr (8 yr) mission with a signal-to-noise ... | lisa and the existence of a fast-merging double neutron star formation channel |
the gravitational wave provides a new method to examine general relativity and its alternatives in the high speed, strong field regime. alternative theories of gravity generally predict more polarizations than general relativity, so it is important to study the polarization contents of theories of gravity to reveal the... | the polarizations of gravitational waves† |
we have observed the relativistic binary pulsar psr j1141-6545 over a period of ∼6 yr using the parkes 64 m radio telescope, with a focus on modelling the diffractive intensity scintillations to improve the accuracy of the astrometric timing model. the long-term scintillation, which shows orbital and annual variations,... | modelling annual and orbital variations in the scintillation of the relativistic binary psr j1141-6545 |
radio-loud neutron stars known as pulsars allow a wide range of experimental tests for fundamental physics, ranging from the study of super-dense matter to tests of general relativity (gr) and its alternatives. as a result, pulsars provide strong-field tests of gravity, they allow for the direct detection of gravitatio... | pulsars as probes of gravity and fundamental physics |
we have carried out new, high-frequency, high-time-resolution observations of the crab pulsar. combining these with our previous data, we characterize bright single pulses associated with the main pulse, both the low-frequency and high-frequency interpulses, and the two high-frequency components. our data include obser... | the crab pulsar at centimeter wavelengths. ii. single pulses |
the equation of state (eos) of the neutron star (ns) matter remains an enigma. in this work we perform the bayesian parameter inference with the gravitational wave data (gw170817) and mass-radius observations of some nss (psr j 0030 +0451 , psr j 0437 -4715 , and 4u 1702-429) using the phenomenologically constructed eo... | constraint on phase transition with the multimessenger data of neutron stars |
nearly one-third of the sources listed in the third fermi large area telescope (lat) catalog (3fgl) remain unassociated. it is possible that predicted and even unanticipated gamma-ray source classes are present in these data waiting to be discovered. taking advantage of the excellent spectral capabilities achieved by t... | 3fgl demographics outside the galactic plane using supervised machine learning: pulsar and dark matter subhalo interpretations |
the science cases for incorporating high time resolution capabilities into modern radio telescopes are as numerous as they are compelling. science targets range from exotic sources such as pulsars, to our sun, to recently detected possible extragalactic bursts of radio emission, the so-called fast radio bursts (frbs). ... | the high time and frequency resolution capabilities of the murchison widefield array |
the discovery of pulsars as heavy as 2 solar masses has led astrophysicists to rethink the core compositions of neutron stars, ruling out many models for the nuclear equations of state (eos). we explore the hybrid stars that occur when hadronic matter is treated in a relativistic mean-field approximation and quark matt... | constant-sound-speed parametrization for nambu-jona-lasinio models of quark matter in hybrid stars |
small-scale dark matter structure within the milky way is expected to affect pulsar timing. the change in gravitational potential induced by a dark matter halo passing near the line of sight to a pulsar would produce a varying delay in the light travel time of photons from the pulsar. individual transits produce an eff... | investigating dark matter substructure with pulsar timing - i. constraints on ultracompact minihaloes |
we report on the hard x-ray burst and the first ∼100 days of nicer monitoring of the soft x-ray temporal and spectral evolution of the newly discovered magnetar swift j1818.0-1607. the burst properties are typical of magnetars with a duration of t90 = 10 ± 4 ms and a temperature of kt = 8.4 ± 0.7 kev. the 2-8 kev pulse... | nicer observation of the temporal and spectral evolution of swift j1818.0-1607: a missing link between magnetars and rotation-powered pulsars |
aims: to estimate the compactness of the thermally-emitting isolated neutron star (ins) rx j0720.4-3125, an x-ray spin-phase-resolved spectroscopic study is conducted. in addition, to identify the genuine spin-period, an x-ray timing analysis is performed.methods: the data from all observations of rx j0720.4-3125 condu... | the compactness of the isolated neutron star rx j0720.4-3125 |
we report nondetections of the ∼3 × 108 yr old, slow, isolated, rotation-powered pulsar psr j2144-3933 in observations with the hubble space telescope in one optical band (f475x) and two far-ultraviolet bands (f125lp and f140lp), yielding upper bounds {f}{{f}475{{x}}}< 22.7 {njy}, {f}{{f}125{lp}}< 5.9 {njy}, and ... | hubble space telescope nondetection of psr j2144-3933: the coldest known neutron star |
the discovery and study of pulsars and fast radio bursts (frbs) in time-domain radio data is often hampered by radio frequency interference (rfi). some of this terrestrial rfi is impulsive and bright, and relatively easy to identify and remove. other anthropogenic signals, however, are weaker yet periodic, and their pe... | fourier domain excision of periodic radio frequency interference |
context. high-precision pulsar timing requires accurate corrections for dispersive delays of radio waves, parametrized by the dispersion measure (dm), particularly if these delays are variable in time. in a previous paper, we studied the solar wind (sw) models used in pulsar timing to mitigate the excess of dm that is ... | the impact of solar wind variability on pulsar timing |
the major programme for observing young, non-recycled pulsars with the parkes telescope has transitioned from a narrow-band system to an ultra-wide-band system capable of observing between 704 and 4032 mhz. we report here on the initial 2 yr of observations with this receiver. results include dispersion measure (dm) an... | two years of pulsar observations with the ultra-wide-band receiver on the parkes radio telescope |
slightly more than 30 years ago, whipple detection of the crab nebula was the start of very high energy gamma-ray astronomy. since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly hi... | the crab pulsar and nebula as seen in gamma-rays |
it has been shown that the synergy of a scalar field coupling with both the ricci scalar and the gauss-bonnet invariant significantly affects the properties of scalarized black holes and neutron stars, including their domain of existence and the amount of scalar hair they carry. here we study the radial stability of sc... | stable spontaneously-scalarized black holes in generalized scalar-tensor theories |
the observable population of double neutron star (dns) systems in the milky way allow us to understand the nature of supernovae and binary stellar evolution. until now, all dns systems in wide orbits (porb > 1 d) have been found to have orbital eccentricities, e > 0.1. in this paper, we report the discovery of pu... | the high time resolution universe pulsar survey - xvii. psr j1325-6253, a low eccentricity double neutron star system from an ultra-stripped supernova |
the radio and gamma-ray pulsar psr j2032+4127 was recently found to be in a decades-long orbit with the be star mt91 213, with the pulsar moving rapidly towards periastron. this binary shares many similar characteristics with the previously unique binary system psr b1259-63/ls 2883. here, we describe radio, x-ray, and ... | multiwavelength monitoring and x-ray brightening of be x-ray binary psr j2032+4127/mt91 213 on its approach to periastron |
we present a new single-pulse pipeline for the palfa survey to efficiently identify single radio pulses from pulsars, rotating radio transients (rrats), and fast radio bursts (frbs). we conducted a sensitivity analysis of this new pipeline in which many single pulses were injected into palfa data and run through the pi... | palfa single-pulse pipeline: new pulsars, rotating radio transients, and a candidate fast radio burst |
a large fraction of gamma-ray bursts (grbs) displays an x-ray plateau phase within <105 s from the prompt emission, proposed to be powered by the spin-down energy of a rapidly spinning newly born magnetar. in this work we use the properties of the galactic neutron star population to constrain the grb-magnetar scenar... | constraining the grb-magnetar model by means of the galactic pulsar population |
we present a strong hint of a connection between high-energy γ-ray emitting blazars, very high energy neutrinos, and ultrahigh-energy cosmic rays. we first identify potential hadronic sources by filtering γ-ray emitters in spatial coincidence with the high-energy neutrinos detected by icecube. the neutrino filtered γ-r... | connecting blazars with ultrahigh-energy cosmic rays and astrophysical neutrinos |
it has long been suggested that nearby pulsars within ∼1 kpc are the leading candidate of the 10-500 gev cosmic-ray positron excess measured by pamela and other experiments. the recent measurement of the surface brightness profile of tev nebulae surrounding geminga and psr b0656+14 by the high-altitude water cherenkov ... | gev observations of the extended pulsar wind nebulae constrain the pulsar interpretations of the cosmic-ray positron excess |
a theoretical framework for emission originating from rapidly rotating oblate compact objects is described in detail. using a hamilton-jacobi formalism, we show that special relativistic rotational effects such as aberration of angles, doppler boosting, and time dilatation naturally emerge from the general relativistic... | radiation from rapidly rotating oblate neutron stars |
modern astrophysics is undergoing a revolution. as detector technology has advanced, and astronomers have been able to study the sky with finer temporal detail, a rich diversity of sources that vary on timescales from years down to a few nanoseconds has been found. among these are fast radio bursts, which exhibit pulse... | a decade of fast radio bursts |
it has been suggested that some classes of luminous supernovae (sne) and gamma-ray bursts (grbs) are driven by newborn magnetars. fast-rotating proto-neutron stars have also been of interest as potential sources of gravitational waves (gws). we show that for a range of rotation periods and magnetic fields, hard x-rays ... | gammy-ray and hard x-ray emission from pulsar-aided supernovae as a probe of particle acceleration in embryonic pulsar wind nebulae |
we report on the first millisecond timescale radio interferometric search for the new class of transient known as fast radio bursts (frbs). we used the very large array (vla) for a 166 hr, millisecond imaging campaign to detect and precisely localize an frb. we observed at 1.4 ghz and produced visibilities with 5 ms ti... | a millisecond interferometric search for fast radio bursts with the very large array |
this paper aims to explore a class of static stellar equilibrium configuration of relativistic charged spheres made of a charged perfect fluid. for solving the einstein-maxwell field equations, we consider a particularized metric potential, buchdahl ansatz [1] and then by using a simple transformation. the study is dev... | relativistic charged spheres: compact stars, compactness and stable configurations |
we report on the discovery of a dramatic change in the energy spectrum of the x-ray pulsar gx 304-1 appearing at low luminosity. particularly, we found that the cut-off power-law spectrum typical for accreting pulsars, including gx 304-1 at higher luminosities of lx ∼ 1036-1037 erg s-1, transformed at lower luminosity ... | dramatic spectral transition of x-ray pulsar gx 304-1 in low luminous state |
we discuss the theory of pulsar-timing and astrometry probes of a stochastic gravitational-wave background with a recently developed "total-angular-momentum" (tam) formalism for cosmological perturbations. we review the formalism, emphasizing in particular the features relevant for this work and describe the observable... | pulsar-timing arrays, astrometry, and gravitational waves |
context. glitches are rare spin-up events that punctuate the smooth slow-down of the rotation of pulsars. for the vela pulsar and psr j0537-6910, their large glitch sizes and the times between consecutive events have clear preferred scales (gaussian distributions), contrary to the handful of other pulsars with enough g... | glitch time series and size distributions in eight prolific pulsars |
we provide a bird's-eye view of neutron-star seismology, which aims to probe the extreme physics associated with these objects, in the context of gravitational-wave astronomy. focussing on the fundamental mode of oscillation, which is an efficient gravitational-wave emitter, we consider the seismology aspects of a numb... | a gravitational-wave perspective on neutron-star seismology |
the core rotation rates of massive stars have a substantial impact on the nature of core-collapse (cc) supernovae and their compact remnants. we demonstrate that internal gravity waves (igws), excited via envelope convection during a red supergiant phase or during vigorous late time burning phases, can have a significa... | the spin rate of pre-collapse stellar cores: wave-driven angular momentum transport in massive stars |
we present the results from a monitoring campaign made with the neil gehrels swift observatory of the m51 galaxies, which contain several variable ultraluminous x-ray sources (ulxs). the ongoing campaign started in 2018 may, and we report here on ∼1.5 yr of observations. the campaign, which consists of 106 observations... | swift monitoring of m51: a 38 day superorbital period for the pulsar ulx7 and a new transient ultraluminous x-ray source |
studying how the black hole (bh) - (galaxy) bulge mass relation evolves with redshift provides valuable insights into the co-evolution of supermassive black holes and their host galaxies. however, obtaining accurate measurement of bh masses is challenging due to the bias towards the most massive and luminous galaxies. ... | mass-redshift dependency of supermassive black hole binaries for the gravitational wave background |
at the linear level, the gravitational wave (gw) spectrum predicted by inflation, and many of its alternatives, can have arbitrarily small amplitude and consequently an unconstrained tilt. however, at second order, tensor fluctuations are sourced by scalar fluctuations that have been measured in the cosmic microwave ba... | constraints on scalar and tensor spectra from neff |
millisecond pulsars are very likely the main source of gamma-ray emission from globular clusters. however, the relative contributions of two separate emission processes - curvature radiation from millisecond pulsar magnetospheres versus inverse compton emission from relativistic pairs launched into the globular cluster... | evidence for a high-energy tail in the gamma-ray spectra of globular clusters |
to make best use of multifaceted astronomical and nuclear data sets, probability distributions of neutron star models that can be used to propagate errors consistently from one domain to another are required. we take steps toward a consistent model for this purpose, highlight where model inconsistencies occur, and asse... | prior probability distributions of neutron star crust models |
we made a detailed study of the timing and spectral properties of the x-ray pulsar 1a 0535+262 during the recent giant outburst in 2020 november and december. the flux of the pulsar reached a record value of ~12.5 crab as observed by swift/bat (15-50 kev) and the corresponding mass accretion rate was ~6.67 × 1017 g s-1... | study of timing and spectral properties of the x-ray pulsar 1a 0535+262 during the giant outburst in 2020 november-december |
in this work, we present polarization profiles for 23 millisecond pulsars observed at 820 and 1500 mhz with the green bank telescope as part of the nanograv pulsar timing array. we calibrate the data using mueller matrix solutions calculated from observations of psrs b1929+10 and j1022+1001. we discuss the polarization... | the nanograv 12.5 yr data set: polarimetry and faraday rotation measures from observations of millisecond pulsars with the green bank telescope |
we present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. we used the second data release of the 144 mhz lofar two-metre sky survey to produce circularly polarised maps with a median noise of 140 µjy beam−1 and resolution of 20″ for ≈27% of the northern sky ... | v-lotss: the circularly polarised lofar two-metre sky survey |
the latest pulsar timing array data reveal evidence of nanohertz gravitational waves (gws), which have been explained by both cosmological and astrophysical sources. however, current observations lack the precision needed to differentiate between different models from the spectral index. we find that the cosmological g... | distinguishing the nanohertz gravitational-wave sources by the observations of compact dark matter subhalos |
pulsar-timing arrays (ptas) are in the near future expected to detect a stochastic gravitational-wave background (sgwb) produced by a population of inspiralling supermassive black hole binaries. in this work, we consider a background that can be anisotropic and circularly polarized. we use the expansion of the intensit... | pulsar-timing measurement of the circular polarization of the stochastic gravitational-wave background |
the latest fermi-lat gamma-ray catalogue, 4fgl-dr3, presents a large fraction of sources without clear association to known counterparts, i.e. unidentified sources (unids). in this paper, we aim to classify them using machine learning algorithms, which are trained with the spectral characteristics of associated sources... | classification of fermi-lat unidentified gamma-ray sources using catboost gradient boosting decision trees |
we present a spectral analysis of nustar and nicer observations of the luminous, persistently accreting neutron star (ns) low-mass x-ray binary cygnus x-2. the data were divided into different branches that the source traces out on the z-track of the x-ray color-color diagram; namely, the horizontal branch, the normal ... | radius constraints from reflection modeling of cygnus x-2 with nustar and nicer |
we show that a small but measurable shift in the eclipse midpoint time of eclipsing binary (ebs) stars of ~0.1 s over a decade baseline can be used to directly measure the galactic acceleration of stars in the milky way at ~kiloparsec distances from the sun. we consider contributions to the period drift rate from dynam... | eclipse timing the milky way's gravitational potential |
a deep survey of the large magellanic cloud at ~0.1-100tev photon energies with the cherenkov telescope array is planned. we assess the detection prospects based on a model for the emission of the galaxy, comprising the four known tev emitters, mock populations of sources, and interstellar emission on galactic scales. ... | sensitivity of the cherenkov telescope array to tev photon emission from the large magellanic cloud |
we show via both analytical calculation and numerical simulation that the optimal cross-correlation statistic (os) for stochastic gravitational-wave-background (gwb) searches using data from pulsar timing arrays follows a generalized chi-squared (gx2) distribution—i.e., a linear combination of chi-squared distributions... | analytic distribution of the optimal cross-correlation statistic for stochastic gravitational-wave-background searches using pulsar timing arrays |
pulsar timing provides a sensitive probe of small-scale structure. gravitational perturbations arising from an inhomogeneous environment could manifest as detectable perturbations in the pulsation phase. consequently, pulsar timing arrays have been proposed as a probe of dark matter substructure on mass scales as small... | dark matter microhalos in the solar neighborhood: pulsar timing signatures of early matter domination |
decades long monitoring of millisecond pulsars, which exhibit highly stable rotational periods in pulsar timing array experiments is on the threshold of discovering nanohertz stochastic gravitational wave background. this paper describes the indian pulsar timing array (inpta) experiment, which employs the upgraded gian... | nanohertz gravitational wave astronomy during ska era: an inpta perspective |
we extract new classes of anisotropic solutions in the framework of mimetic gravity, by applying the tolman-finch-skea metric and a specific anisotropy not directly depending on it, and by matching smoothly the interior anisotropic solution to the schwarzschild exterior one. then, in order to provide a transparent pict... | new anisotropic star solutions in mimetic gravity |
periodic modulations are seen in normal pulsars (p > 0.1 s) over timescales ranging from a few seconds to several minutes. such modulations have usually been associated with the phenomenon of subpulse drifting. a number of recent studies have shown subpulse drifting to exhibit very specific physical characteristics:... | periodic modulation: newly emergent emission behavior in pulsars |
we present statistical analysis of a fluence-limited sample of over 1100 giant pulses from the crab pulsar, with fluence > 130 jy ms at ∼1330 mhz. these were detected in ∼260 h of observation with the national centre for radio astrophysics (ncra) 15 m radio telescope. we find that the pulse-energy distribution follo... | super-giant pulses from the crab pulsar: energy distribution and occurrence rate |
in a recent work, we emphasized that an excess in trilepton events plus missing energy observed by the atlas experiment at the lhc could be interpreted as a signal of low-energy supersymmetry. in such a scenario the lightest neutralino mass is approximately mχ≃60 gev and the direct dark matter detection cross section i... | return of the wimp: missing energy signals and the galactic center excess |
cosmological models with a dynamical dark energy field typically lead to a modified propagation of gravitational waves via an effectively time-varying gravitational coupling g (t ). the local variation of this coupling between the time of emission and detection can be probed with standard sirens. here we discuss the ro... | standard sirens as a novel probe of dark energy |
although high-sensitivity surveys have revealed a number of highly dispersed pulsars in the inner galaxy, none have so far been found in the galactic centre (gc) region, which we define to be within a projected distance of 1 pc from sgr a*. this null result is surprising given that several independent lines of evidence... | detecting pulsars in the galactic centre |
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