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we present deep polarimetric observations at 154 mhz with the murchison widefield array (mwa), covering 625 deg2 centered on α = 0hand δ = -27°. the sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. our analysis ... | low-frequency observations of linearly polarized structures in the interstellar medium near the south galactic pole |
inspiraling massive black hole binaries (mbhbs) forming in the aftermath of galaxy mergers are expected to be the loudest gravitational-wave (gw) sources relevant for pulsar-timing arrays (ptas) at nhz frequencies. the incoherent overlap of signals from a cosmic population of mbhbs gives rise to a stochastic gw backgro... | post-newtonian evolution of massive black hole triplets in galactic nuclei - iii. a robust lower limit to the nhz stochastic background of gravitational waves |
despite considerable experimental progress large parts of the axionlike particle (alp) parameter space remain difficult to probe in terrestrial experiments. in some cases, however, small-scale structure of the alp dark matter (dm) distribution is strongly enhanced, offering opportunities for astrophysical tests. such a... | imprints of the early universe on axion dark matter substructure |
in this paper, we use the equation of state based on a modification of the 2 +1 flavors nambu-jona-lasinio (njl) model to study the quark matter of hybrid stars. for comparison, we utilize five eoss of the relativistic mean-field (rmf) model to describe the hadronic phase. with the three-window crossover interpolation ... | studies of the structure of massive hybrid stars within a modified njl model |
the recent detection of pulsations from the ultraluminous x-ray source (ulx) nustar j095551+6940.8 in m82 by bachetti et al. indicates that the object is an accreting neutron star in a high-mass x-ray binary (hmxb) system. the super-eddington luminosity of the object implies that the magnetic field is sufficiently stro... | the ultraluminous x-ray source nustar j095551+6940.8: a magnetar in a high-mass x-ray binary. |
in this letter, we present a new method that quantitatively identifies the occurrence probability of equations of state (eos) beyond "standard" eos models that disfavor sharp and strong phase-transitions, based on neutron star mass and radius observations. the radii of two neutron stars with different masses are natura... | indication of sharp and strong phase-transitions from nicer observations |
context. extended gamma-ray tev emission (tev halos) around middle-aged pulsars has been detected. a proposed model to explain these tev halos is that electrons from a degree-wide pulsar wind nebula (pwn) get up-scattered by cosmic microwave background photons through inverse compton processes. however, no x-ray degree... | searching for x-ray counterparts of degree wide tev halos around middle-aged pulsars with srg/erosita |
in this paper, we investigate the scalar-induced gravitational waves in single-field non-attractor inflation for the pulsar timing arrays data. our model comprises three phases of inflation: the first and third phases are slow-roll inflation, while the second phase is a period of non-attractor inflation. we analyze the... | induced gravitational waves from non-attractor inflation and nanograv data |
most black holes (bhs) will absorb a neutron star (ns) companion fully intact without tidal disruption, suggesting the pair will remain dark to telescopes. even without tidal disruption, electromagnetic (em) luminosity is generated from the battery phase of the binary when the bh interacts with the ns magnetic field. o... | fast radio bursts and radio transients from black hole batteries |
neutron stars are among the densest known objects in the universe and an ideal laboratory for the strange physics of supercondensed matter. while the simultaneous measurements of mass and radius of nonrotating neutron stars may impose constraints on the properties of the dense nuclear matter, the observation and study ... | effects of the equation of state on the bulk properties of maximally rotating neutron stars |
we present broadband, multi-epoch x-ray spectroscopy of the pulsating ultra-luminous x-ray source (ulx) in ngc 5907. simultaneous xmm-newton and nustar data from 2014 are best described by a multicolor blackbody model with a temperature gradient as a function of accretion disk radius significantly flatter than expected... | spectral changes in the hyperluminous pulsar in ngc 5907 as a function of super-orbital phase |
we report on a search for fast radio bursts (frbs) with the green bank northern celestial cap (gbncc) pulsar survey at 350 mhz. pointings amounting to a total on-sky time of 61 days were searched to a dispersion measure (dm) of 3000 pc cm-3, while the rest (23 days; 29% of the total time) were searched to a dm of 500 p... | a search for fast radio bursts with the gbncc pulsar survey |
we study the dynamics and evolution of the milky way nuclear star cluster performing a high-resolution direct one-million-body simulation. focusing on the interactions between such stellar systems and the central supermassive black hole, we find that different stellar components adapt their overall distribution differe... | direct n-body simulation of the galactic centre |
we propose that chirally asymmetric plasma can be produced in the gap regions of the magnetospheres of pulsars and black holes. we show that, in the case of supermassive black holes situated in active galactic nuclei, the chiral charge density and the chiral chemical potential are very small and unlikely to have any ob... | chiral anomalous processes in magnetospheres of pulsars and black holes |
the optical study of the heated substellar companions of black widow (bw) millisecond pulsars (msps) provides unique information on the msp particle and radiation output and on the neutron star mass. here we present an analysis of optical photometry and spectroscopy of a set of relatively bright bws, many newly discove... | an optical study of the black widow population |
it was suggested that the γ-ray halo around geminga might not be interpreted by slow diffusion. if the ballistic regime of electron/positron propagation is considered, the geminga halo may be explained even with a large diffusion coefficient. in this work, we examine this effect by taking the generalized jüttner propag... | slow diffusion is necessary to explain the γ-ray pulsar halos |
mixed fermion-boson stars are stable, horizonless, everywhere-regular solutions of the coupled einstein-(complex, massive) klein-gordon-euler system. while isolated neutron stars and boson stars are uniquely determined by their central energy density, mixed configurations conform to an extended parameter space that dep... | can fermion-boson stars reconcile multimessenger observations of compact stars? |
we model here the merger histories of the supermassive black hole (smbh) population in the late stages of a cosmological simulation of a ~ 2 × 1013 m ⊙ galaxy group. the gravitational dynamics around the several tens of smbhs (m • > 7.5 × 107 m ⊙) hosted by the galaxies in the group is computed at high accuracy usin... | signatures of the many supermassive black hole mergers in a cosmologically forming massive early-type galaxy |
pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. the vela pulsar wind nebula is powered by a young pulsar (b0833-45, aged 11,000 years)1 and located inside an extended structure called vela x, which is its... | vela pulsar wind nebula x-rays are polarized to near the synchrotron limit |
in spite of the rich phenomenology of the polarization properties of radio pulsars, the rotating vector model (rvm) created 50 years ago remains the best method to determine the beam geometry of a pulsar. we apply the rvm to a sample of 854 radio pulsars observed with the meerkat telescope in order to draw conclusions ... | the thousand-pulsar-array programme on meerkat - xi. application of the rotating vector model |
in order to address the generation of neutron star magnetic fields, with particular focus on the dichotomy between magnetars and radio pulsars, we consider the properties of dynamos as inferred from other astrophysical systems. with sufficiently low (modified) rossby number, convective dynamos are known to produce dipo... | on the origin of pulsar and magnetar magnetic fields |
the origin of fast radio bursts (frbs), the brightest cosmic explosion in radio bands, remains unknown. magnetar-related mechanisms are currently favored. the searches for short-term periodicity that is naturally expected for such fast-spinning compact objects, however, have failed. we introduce here a novel method for... | frbs' brownian motion on time-energy bivariate space |
pulsar timing arrays (ptas) and the laser interferometer space antenna (lisa) will open complementary observational windows on massive black hole binaries (mbhbs), i.e. with masses in the range ${\sim} 10^6\!-\!10^{10}\, \rm m_{\odot }$. while ptas may detect a stochastic gravitational wave background from a population... | implications of pulsar timing array observations for lisa detections of massive black hole binaries |
context. gas expulsion is a central concept in some of the models for multiple populations and the light-element anti-correlations in globular clusters. if the star formation efficiency was around 30 per cent and the gas expulsion happened on the crossing timescale, this process could preferentially expel stars born wi... | gas expulsion in massive star clusters?. constraints from observations of young and gas-free objects |
gravitational waves (gw) sourced by second-order primordial curvature fluctuations are among the favoured models fitting the recent pulsar timing array (pta) measurement of a stochastic gw background (sgwb). we study how spectral distortions (sds) and anisotropies of the cosmic microwave background (cmb) can constrain ... | the quest of cmb spectral distortions to probe the scalar-induced gravitational wave background interpretation in pta data |
neutron star-black hole (nsbh) mergers detected in gravitational waves have the potential to shed light on supernova physics, the dense matter equation of state, and the astrophysical processes that power their potential electromagnetic counterparts. we use the population of four candidate nsbh events detected in gravi... | population properties and multimessenger prospects of neutron star-black hole mergers following gwtc-3 |
the frequency dependence of radio pulse arrival times provides a probe of structures in the intervening media. demorest et al. was the first to show a short-term (∼100-200 days) reduction in the electron content along the line of sight to psr j1713+0747 in data from 2008 (approximately mjd 54750) based on an apparent d... | a second chromatic timing event of interstellar origin toward psr j1713+0747 |
this python module provides an interface for querying the australia telescope national facility (atnf) pulsar catalogue (manchester et al. 2005). the intended users are astronomers wanting to extract data from the catalogue through a script rather than having to download and parse text tables output using the standard ... | psrqpy: a python interface for querying the atnf pulsar catalogue |
supermassive black holes (bhs) are believed to be the central powerhouse of active galactic nuclei. applying the pulsar outer-magnetospheric particle accelerator theory to bh magnetospheres, we demonstrate that an electric field is exerted along the magnetic field lines near the event horizon of a rotating bh. in this ... | energetic gamma radiation from rapidly rotating black holes |
we introduce simplified models for enhancements in the matter power spectrum at small scales and study their implications for dark matter substructure and gravitational observables. these models capture the salient aspects of a variety of early universe scenarios that predict enhanced small-scale structure, such as axi... | dark matter microhalos from simplified models |
a bright radio burst was newly discovered in sgr 1935+2154, which exhibits some fast radio burst (frb)-like temporal and frequency properties, suggesting a neutron star (ns)/magnetar magnetospheric origin of frbs. we propose an explanation of the temporal and frequency properties of sub-pulses of repeating frbs based o... | on the magnetospheric origin of repeating fast radio bursts |
observations of binary pulsars and pulsars in globular clusters suggest that at least some pulsars must receive weak natal kicks at birth. if all pulsars received strong natal kicks above 50 km s-1, those born in globular clusters would predominantly escape, while wide binaries would be disrupted. on the other hand, ob... | constraints on weak supernova kicks from observed pulsar velocities |
cosmic rays (crs) leave their sources mainly along the local magnetic field; in doing so they excite both resonant and nonresonant modes through streaming instabilities. the excitation of these modes leads to enhanced scattering and in turn to a large pressure gradient that causes the formation of bubbles of gas, crs, ... | dynamical effects of cosmic rays on the medium surrounding their sources |
we perform general relativistic, magnetohydrodynamic simulations of merging binary neutron stars incorporating neutrino transport and magnetic fields. our new radiative transport module for neutrinos adopts a general relativistic, truncated-moment formalism. the binaries consist of two identical, irrotational stars mod... | jet launching from binary neutron star mergers: incorporating neutrino transport and magnetic fields |
einstein's theory of general relativity is one of the pillars of modern physics. for decades, the theory has been mainly tested in the weak field regime with experiments in the solar system and observations of binary pulsars. thanks to a new generation of observational facilities, the past 5 years have seen remarkable ... | testing general relativity with black hole x-ray data: a progress report |
recently, some fast radio burst (frb) repeaters were reported to exhibit complex, diverse variations of faraday rotation measures (rms), which implies that they are surrounded by an inhomogeneous, dynamically evolving, magnetized environment. we systematically investigate some possible astrophysical processes that may ... | faraday rotation measure variations of repeating fast radio burst sources |
we perform hydrodynamic simulations of mass transfer in binaries that contain a white dwarf and a neutron star (wd-ns binaries), and measure the specific angular momentum of material lost from the binary in disc winds. by incorporating our results within a long-term evolution model, we measure the long-term stability o... | mass transfer in white dwarf-neutron star binaries |
we investigate constraints on the spectral index of primordial gravitational waves (gws), paying particular attention to a blue-tilted spectrum. such constraints can be used to test a certain class of models of the early universe. we investigate observational bounds from ligo+virgo, pulsar timing and big bang nucleosyn... | blue-tilted tensor spectrum and thermal history of the universe |
we report on the analysis of nustar observations of the be-transient x-ray pulsar v 0332+53 during the giant outburst in 2015 and another minor outburst in 2016. we confirm the cyclotron-line energy-luminosity correlation previously reported in the source and the line energy decrease during the giant outburst. based on... | luminosity dependence of the cyclotron line and evidence for the accretion regime transition in v 0332+53 |
we present the orbital solution for the newly discovered transient be x-ray binary swift j0243.6+6124 based on the data from the gamma-ray burst monitor on board fermi obtained during the october 2017 outburst. we model the doppler induced and intrinsic spin variations of the neutron star assuming that the latter is dr... | orbit and intrinsic spin-up of the newly discovered transient x-ray pulsar swift j0243.6+6124 |
we have observed a large glitch in the crab pulsar (psr b0531+21). the glitch occurred around mjd 58064 (2017 november 8) when the pulsar underwent an increase in the rotation rate of δν = 1.530 × 10-5 hz, corresponding to a fractional increase of δν/ν = 0.516 × 10-6, making this event the largest glitch ever observed ... | the largest glitch observed in the crab pulsar |
we present an algorithm to generalize a plethora of well-known solutions to einstein field equations describing spherically symmetric relativistic fluid spheres by relaxing the pressure isotropy condition on the system. by suitably fixing the model parameters in our formulation, we generate closed-form solutions which ... | anisotropic generalization of well-known solutions describing relativistic self-gravitating fluid systems: an algorithm |
in paper i of this series, we detected a significant value of the braking index (n) for 19 young, high- $\dot{e}$ radio pulsars using ∼10 yr of timing observations from the 64-m parkes radio telescope. here, we investigate this result in more detail using a bayesian pulsar timing framework to model timing noise and to ... | timing of young radio pulsars - ii. braking indices and their interpretation |
wave effects are often neglected in microlensing studies; however, for coherent point-like sources, such as pulsars and fast radio bursts (frbs), wave effects will become important in their gravitational lensing. in this paper, we describe the wave-optics formalism, its various limits, and the conditions for which thes... | wave effects in the microlensing of pulsars and frbs by point masses |
fast radio bursts (frbs) are short-duration radio transients of unknown origin. thus far, they have been blindly detected at millisecond time-scales with dispersion measures (dms) between 110 and 2600 pc cm-3. however, the observed pulse width, dm, and even brightness distributions depend strongly on the time and frequ... | interpreting the distributions of frb observables |
we present a detailed study of the complex time-frequency structure of a sample of previously reported bursts of frb 121102 detected with the meerkat telescope in september 2019. the wide contiguous bandwidth of these observations have revealed a complex bifurcating structure in some bursts at 1250 mhz. when de-dispers... | an analysis of the time-frequency structure of several bursts from frb 121102 detected with meerkat |
psr j1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbital period, of 3.98 hr. we here present a timing study based on five years of observations, conducted with the five largest radio telescopes in the world, aimed at determining the companion nature. through the measurement of ... | the binary companion of young, relativistic pulsar j1906+0746 |
in a search with the parkes radio telescope of 56 unidentified fermi-large area telescope (lat) gamma-ray sources, we have detected 11 millisecond pulsars (msps), 10 of them discoveries, of which five were reported by kerr et al. we did not detect radio pulsations from six other pulsars now known in these sources. we d... | parkes radio searches of fermi gamma-ray sources and millisecond pulsar discoveries |
extreme scattering events (eses) in the interstellar medium (ism) were first observed in regular flux measurements of compact extragalactic sources. they are characterized by a flux variation over a period of weeks, suggesting the passage of a “diverging plasma lens” across the line of sight (los). modeling the refract... | pulsar observations of extreme scattering events |
anisotropic bursts of gravitational radiation produced by events such as supermassive black hole mergers leave permanent imprints on space. such gravitational wave `memory' (gwm) signals are, in principle, detectable through pulsar timing as sudden changes in the apparent pulse frequency of a pulsar. if an array of pul... | searching for gravitational wave memory bursts with the parkes pulsar timing array |
binary neutron star (bns) mergers are the leading model to explain the phenomenology of short gamma-ray bursts (sgrbs). recent observations of long-lasting x-ray afterglows of sgrbs challenge standard paradigms and indicate that in a large fraction of events a long-lived neutron star (ns) may be formed rather than a bl... | electromagnetic emission from long-lived binary neutron star merger remnants. i. formulation of the problem |
cosmological observations precisely measure primordial variations in the density of the universe at megaparsec and larger scales, but much smaller scales remain poorly constrained. however, sufficiently large initial perturbations at small scales can lead to an abundance of ultradense dark matter minihalos that form du... | lensing constraints on ultradense dark matter halos |
this paper is devoted to evaluating exact anisotropic spherical solutions for static self-gravitating systems through extended geometric deformation decoupling technique. for this purpose, we consider an isotropic tolman iv solution and extend it to anisotropic domain by transforming both temporal as well as radial met... | anisotropic spherical solutions through extended gravitational decoupling approach |
nasa's nicer telescope has recently provided evidence for non-dipolar magnetic field structures in rotation-powered millisecond pulsars. these stars are assumed to have gone through a prolonged accretion spin-up phase, begging the question of what accretion flows on to stars with complex magnetic fields would look like... | grmhd simulations of accreting neutron stars with non-dipole fields |
with the ever-increasing sensitivity and timing baselines of modern radio telescopes, a growing number of pulsars are being shown to exhibit transitions in their rotational and radio emission properties. in many of these cases, the two are correlated with pulsars assuming a unique spin-down rate ($\dot{\nu }$) for each... | long-term rotational and emission variability of 17 radio pulsars |
previous studies in low pressure magnetized capacitively coupled radio frequency (rf) plasmas operated in argon with optimized geometric reactor symmetry have shown that the magnetic asymmetry effect (mae) allows to control the particle flux energy distributions at the electrodes, the plasma symmetry, and the dc self-b... | the magnetic asymmetry effect in geometrically asymmetric capacitively coupled radio frequency discharges operated in ar/o2 |
ecological environment quality assessment (eeq) is an important parameter for sustainable development and sometimes it's more valuable during industrialization and urbanization progress of the region. this study compares remote sensing ecological index (rsei) and ecological index (ei) and assesses eeq with the most pop... | eco-environmental quality assessment based on pressure-state-response framework by remote sensing and gis |
we evaluate the performance of four different machine learning (ml) algorithms: an artificial neural network multi-layer perceptron (ann mlp), adaboost, gradient boosting classifier (gbc), and xgboost, for the separation of pulsars from radio frequency interference (rfi) and other sources of noise, using a dataset obta... | separation of pulsar signals from noise using supervised machine learning algorithms |
the soft-gamma repeater swift j1818.0-1607 is only the fifth magnetar found to exhibit pulsed radio emission. using the ultra-wideband low receiver system of the parkes radio telescope, we conducted a 3 hr observation of swift j1818.0-1607. folding the data at a rotation period of p = 1.363 s, we obtained wideband pola... | spectropolarimetric properties of swift j1818.0-1607: a 1.4 s radio magnetar |
pulsar timing experiments require high-fidelity template profiles in order to minimize the biases in pulse time-of-arrival (toa) measurements and their uncertainties. efforts to acquire more precise toas given the fixed effective area of telescopes, finite receiver noise, and limited integration time have led pulsar as... | frequency-dependent template profiles for high-precision pulsar timing |
galactic electron density distribution models are crucial tools for estimating the impact of the ionised interstellar medium on the impulsive signals from radio pulsars and fast radio bursts. the two prevailing galactic electron density models (gedms) are ymw16 (yao et al. <xref rid="r50" ref-type="bibr">2017<... | a comparison of galactic electron density models using pygedm |
scalar-tensor theories (stts) are a widely studied alternative to general relativity (gr) in which gravity is endowed with an additional scalar degree of freedom. although severely constrained by solar system and pulsar timing experiments, there remains a large set of stts which are consistent with all present day obse... | possibility of setting a new constraint to scalar-tensor theories |
pulsars are wonderful gravitational probes. their tiny size and stellar mass give their rotation periods a stability comparable to that of atomic frequency standards. this is especially true of the rapidly rotating "millisecond pulsars" (msps). many of these rapidly rotating pulsars are in orbit with another star, allo... | pulsars and gravity |
motivated by the recent suggestions that very massive pulsar (psr j0952-0607) and very light compact object (hess j1731-347) exist, in this article, we revisit the possibility of such objects being strange stars instead of the standard hadronic neutron stars. we study the possible presence of local anisotropy and how i... | anisotropic strange stars in the spotlight: unveiling constraints through observational data |
we introduce a new method for evaluating the oscillatory integrals which describe natural interference patterns. as an illustrative example of contemporary interest, we consider astrophysical plasma lensing of coherent sources like pulsars and fast radio bursts in radioastronomy. plasma lenses are known to occur near t... | oscillatory path integrals for radio astronomy |
magnetic reconnection, a plasma process converting magnetic energy to particle kinetic energy, is often invoked to explain magnetic energy releases powering high-energy flares in astrophysical sources including pulsar wind nebulae and black hole jets. reconnection is usually seen as the (essentially two-dimensional) no... | reconnection and particle acceleration in three-dimensional current sheet evolution in moderately magnetized astrophysical pair plasma |
there are several unexplored regions of the short-duration radio transient phase space. one such unexplored region is the luminosity gap between giant pulses (from pulsars) and cosmologically located fast radio bursts (frbs). the survey for transient astronomical radio emission 2 (stare2) is a search for such transient... | stare2: detecting fast radio bursts in the milky way |
typically, neutron stars are discovered by observations at radio, x-ray or gamma-ray wavelengths. unlike radio pulsar surveys and x-ray observations, optical time-domain surveys can unveil and characterize exciting but less explored non-accreting and/or non-beaming neutron stars in binaries. here we report the discover... | a dynamically discovered and characterized non-accreting neutron star-m dwarf binary candidate |
we have implemented prescriptions for modelling pulsars in the rapid binary population synthesis code compact object mergers: population astrophysics and statistics. we perform a detailed analysis of the double neutron star (dns) population, accounting for radio survey selection effects. the surface magnetic field deca... | modelling double neutron stars: radio and gravitational waves |
we report the detection of gev γ-ray emission from the very-high-energy γ-ray source ver j2227+608 associated with the “tail” region of supernova remnant (snr) g106.3+2.7. the gev γ-ray emission is extended and spatially coincident with molecular clouds traced by co emission. the broadband gev to tev emission of ver j2... | ver j2227+608: a hadronic pevatron pulsar wind nebula? |
the magic stereoscopic system collected 69 hours of crab nebula data between october 2009 and april 2011. analysis of this data sample using the latest improvements in the magic stereoscopic software provided an unprecedented precision of spectral and night-by-night light curve determination at gamma rays. we derived a... | measurement of the crab nebula spectrum over three decades in energy with the magic telescopes |
we report on the polarization properties of two fast radio bursts (frbs): 151230 and 160102 discovered in the survey for pulsars and extragalactic radio bursts (superb) at the parkes radio telescope. frb 151230 is observed to be 6 ± 11 per cent circularly polarized and 35 ± 13 per cent linearly polarized with a rotatio... | the survey for pulsars and extragalactic radio bursts - iii. polarization properties of frbs 160102 and 151230 |
we explain the excess of the antiproton fraction recently reported by the ams-02 experiment by considering collisions between cosmic-ray protons accelerated by a local supernova remnant and the surrounding dense cloud. the same "pp collisions" provide the right ratio of daughter particles to fit the observed positron e... | can we explain ams-02 antiproton and positron excesses simultaneously by nearby supernovae without pulsars or dark matter? |
resonances are among the clearest quantum mechanical signatures of scattering processes. previously, shape resonances and feshbach resonances have been observed in inelastic and reactive collisions involving atoms or diatomic molecules. structure in the integral cross section has been observed in a handful of elastic c... | observation of orbiting resonances in he(3s1) + nh3 penning ionization |
since its initial discovery, the fast radio burst (frb) frb 121102 has been found to be repeating with millisecond-duration pulses. very recently, 14 new bursts were detected by the green bank telescope during its continuous monitoring observations. in this paper, we show that the burst energy distribution has a power-... | frb 121102: a starquake-induced repeater? |
the alpha magnetic spectrometer (ams-02) has just published the unprecedentedly precise measurement of the cosmic electron and positron spectra. in this paper, we try to give a quantitative study on the ams-02 results by a global fitting to the electron and positron spectra, together with the updated positron fraction ... | quantitative study of the ams-02 electron/positron spectra: implications for pulsars and dark matter properties |
aims: we present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 mhz with the lofar high-band antennas. based on the observed profiles, we perform an initial investigation of expected observational effects resulting from the propagation of po... | pulsar polarisation below 200 mhz: average profiles and propagation effects |
millisecond pulsars are neutron stars that attain their very fast rotation during a 108-109-yr-long phase of disk accretion of matter from a low-mass companion star1,2. they can be detected as accretion-powered millisecond x-ray pulsars if towards the end of this phase their magnetic field is strong enough to channel t... | optical pulsations from a transitional millisecond pulsar |
geminga pulsar is surrounded by a multitev γ-ray halo radiated by the high-energy electrons and positrons accelerated by the central pulsar wind nebula (pwn). the angular profile of the γ-ray emission reported by high-altitude water cherenkov observatory indicates an anomalously slow diffusion for the cosmic-ray electr... | possible origin of the slow-diffusion region around geminga |
we present an analytic model to describe the supermassive black hole binary (smbhb) merger rate in the universe with astrophysical observables: galaxy stellar mass function, pair fraction, merger time-scale, and black hole-host galaxy relations. we construct observational priors and compute the allowed range of the cha... | constraining astrophysical observables of galaxy and supermassive black hole binary mergers using pulsar timing arrays |
we present the discovery of a new optical/x-ray source likely associated with the fermi γ-ray source 4fgl j1408.6-2917. its high-amplitude periodic optical variability, large spectroscopic radial-velocity semiamplitude, evidence for optical emission lines and flaring, and x-ray properties together imply the source is p... | a new flaring black widow candidate and demographics of black widow millisecond pulsars in the galactic field |
we report the discovery of psr j0952-0607, a 707 hz binary millisecond pulsar that is now the fastest-spinning neutron star known in the galactic field (i.e., outside of a globular cluster). psr j0952-0607 was found using lofar at a central observing frequency of 135 mhz, well below the 300 mhz to 3 ghz frequencies typ... | lofar discovery of the fastest-spinning millisecond pulsar in the galactic field |
we present a detailed, broad-band x-ray spectral analysis of the ultraluminous x-ray source (ulx) pulsar ngc 7793 p13, a known super-eddington source, utilizing data from the xmm-newton, nustar and chandra observatories. the broad-band xmm-newton+nustar spectrum of p13 is qualitatively similar to the rest of the ulx sa... | super-eddington accretion on to the neutron star ngc 7793 p13: broad-band x-ray spectroscopy and ultraluminous x-ray sources |
the atacama millimeter/submillimeter array (alma) phasing project (app) has developed and deployed the hardware and software necessary to coherently sum the signals of individual alma antennas and record the aggregate sum in very long baseline interferometry (vlbi) data exchange format. these beamforming capabilities a... | the alma phasing system: a beamforming capability for ultra-high-resolution science at (sub)millimeter wavelengths |
a bayesian analysis of the possible behaviors of the dense matter equation of state informed by recent ligo-virgo as well as nicer measurements reveals that all the present observations are compatible with a fully nucleonic hypothesis for the composition of dense matter, even in the core of the most massive pulsar psr ... | the nuclear matter density functional under the nucleonic hypothesis |
in this work we investigate the link between high-mass x-ray binaries (hmxbs) and star formation in the large magellanic cloud (lmc), our nearest star-forming galaxy. using optical photometric data, we identify the most likely counterpart of 44 x-ray sources. among the 40 hmxbs classified in this work, we find 33 be/x-... | star formation history and x-ray binary populations: the case of the large magellanic cloud |
accreting neutron stars can power a wide range of astrophysical phenomena including short- and long-duration gamma-ray bursts, ultra-luminous x-ray sources, and x-ray binaries. numerical simulations are a valuable tool for studying the accretion-disk-magnetosphere interaction that is central to these problems, most cle... | general-relativistic simulations of four states of accretion onto millisecond pulsars |
observations by the fermi-lat have uncovered a bright, spherically symmetric excess surrounding the center of the milky way galaxy. the spectrum of the γ -ray excess peaks sharply at an energy ∼2 gev , exhibiting a hard spectrum at lower energies, and falls off quickly above an energy ∼5 gev . the spectrum of the exces... | high-energy tail of the galactic center gamma-ray excess |
we present a comparative study of the low-frequency eclipses of spider (compact and irradiating binary) psrs b1957+20 and j1816+4510. combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. psrs b1957+20 and j1816+4510 have similar orbital properties, ... | study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition |
spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. in the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from elec... | first narrow-band search for continuous gravitational waves from known pulsars in advanced detector data |
for about half a century, the radio pulsar population was observed to spin in the ~0.002-12 s range, with different pulsar classes having a spin-period evolution that differs substantially depending on their magnetic fields or past accretion history. the recent detection of several slowly rotating pulsars has reopened ... | long-period pulsars as possible outcomes of supernova fallback accretion |
most neutron stars (nss) and black holes (bhs) are believed to be the final remnants in the evolution of massive stars. in this study, we propose a new formation channel for the formation of bhs and peculiar nss [specifically, magnetars and thorne-żytkow objects (t$\dot{\rm z}$os)], which we refer to as the core-merger... | stellar core-merger-induced collapse: new formation pathways for black holes, thorne-żytkow objects, magnetars, and superluminous supernovae |
supermassive black hole binaries (smbhbs) should form frequently in galactic nuclei as a result of galaxy mergers. at subparsec separations, binaries become strong sources of low-frequency gravitational waves (gws), targeted by pulsar timing arrays. we used recent upper limits on continuous gws from the north american ... | the nanograv 11 yr data set: limits on supermassive black hole binaries in galaxies within 500 mpc |
the mergers of compact binaries with at least one neutron star component are the potential leading sites of the production and ejection of r-process elements. discoveries of galactic binary pulsars, short gamma-ray bursts, and gravitational-wave detections have all been constraining the rate of these events, while the ... | gamma rays from kilonova: a potential probe of r-process nucleosynthesis |
in this work, we present an anisotropic generalization of the buchdahl static stellar model by implementing the method of extended gravitational decoupling and further requirement of vanishing complexity (herrera, phys rev d 97:044010,2018). starting off with a general spherically symmetric static metric with two unkno... | complexity-free anisotropic solution of buchdahl's model and energy exchange between relativistic fluids by extended gravitational decoupling |
we present observations of 35 high spin-down energy radio pulsars using the meerkat telescope. polarization profiles and associated parameters are also presented. we derive the geometry for a selection of pulsars which show interpulse emission. we point out that, in several cases, these radio pulsars should also be see... | the thousand-pulsar-array programme on meerkat iv: polarization properties of young, energetic pulsars |
the question of what gravitational theory could supersede general relativity has been central in theoretical physics for decades. many disparate alternatives have been proposed motivated by cosmology, quantum gravity and phenomenological angles, and have been subjected to tests derived from cosmological, solar system a... | fixing extensions to general relativity in the nonlinear regime |
recent observations indicate that in a large fraction of binary neutron star (bns) mergers a long-lived neutron star (ns) may be formed rather than a black hole. unambiguous electromagnetic (em) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (sgrbs) and their afterglow r... | electromagnetic emission from long-lived binary neutron star merger remnants. ii. lightcurves and spectra |
we review observations of several classes of neutron-star-powered outflows: pulsar-wind nebulae (pwne) inside shell supernova remnants (snrs), pwne interacting directly with interstellar medium (ism), and magnetar-powered outflows. we describe radio, x-ray, and gamma-ray observations of pwne, focusing first on integrat... | pulsar-wind nebulae and magnetar outflows: observations at radio, x-ray, and gamma-ray wavelengths |
in this work, we report the discovery and characterization of psr j1411+2551, a new binary pulsar discovered in the arecibo 327 mhz drift pulsar survey. our timing observations of the radio pulsar in the system span a period of about 2.5 years. this timing campaign allowed a precise measurement of its spin period (62.4... | pulsar j1411+2551: a low-mass double neutron star system |
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