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we present a new solution of embedding class i describing the interior of a spherically symmetric charged anisotropic stellar configuration. the exact analytic solution has been explored by considering buchdahl type metric potential g_{rr}. using this analytic solution, we have discussed various physical aspects of a c... | charged anisotropic buchdahl solution as an embedding class i spacetime |
we are presenting a new class of well-behaved solutions in embedding class-i. we proceed our calculations by assuming a new type of grr metric potential and solved for the other metric gtt using karmarkar condition. the necessary condition that any solutions of einstein's field equations to be class-i is to satisfy kar... | a new relativistic stellar model with anisotropic fluid in karmarkar space-time |
to assist with the commissioning (jiang et al. 2019) of the five-hundred-meter aperture spherical radio telescope (fast), we performed a pulsar search, with the primary goal of developing and testing the pulsar data acquisition and processing pipelines. we tested and used three pipelines, two (p1 and p2 hereafter) sear... | the first pulsar discovered by fast |
we provide new exact solutions to the einstein-maxwell system of equations for matter configurations with anisotropy and charge. the spacetime is static and spherically symmetric. a quadratic equation of state is utilised for the matter distribution. by specifying a particular form for one of the gravitational potentia... | compact stars with quadratic equation of state |
in the summer of 2012, during a pulsar search collaboratory workshop, two high-school students discovered j1930-1852, a pulsar in a double neutron star (dns) system. most dns systems are characterized by short orbital periods, rapid spin periods, and eccentric orbits. however, j1930-1852 has the longest spin period ({{... | psr j1930-1852: a pulsar in the widest known orbit around another neutron star |
we report here the einstein@home discovery of psr j1913+1102, a 27.3 ms pulsar found in data from the ongoing arecibo palfa pulsar survey. the pulsar is in a 4.95 hr double neutron star (dns) system with an eccentricity of 0.089. from radio timing with the arecibo 305 m telescope, we measure the rate of advance of peri... | einstein@home discovery of a double neutron star binary in the palfa survey |
bow-shock pulsar wind nebulae (pwne) show a variety of morphological shapes. we attribute this diversity to the geometrical factors: relative orientations of the pulsar rotation axis, proper velocity, and the line of sight (magnetic inclination angle may also have certain influence on the morphology). we identify three... | 3d dynamics and morphology of bow-shock pulsar wind nebulae |
in more than four years of observation the large area telescope on board the fermi satellite has identified pulsed γ-ray emission from more than 80 young or middle-aged pulsars, in most cases providing light curves with high statistics. fitting the observed profiles with geometrical models can provide estimates of the ... | light-curve modelling constraints on the obliquities and aspect angles of the young fermi pulsars |
more than a dozen binary systems are now established as sources of variable, high-energy (he, 0.1- 100 gev) gamma rays. five are also established sources of very-high-energy (vhe, ⩾ 100 gev) gamma rays. the mechanisms behind gamma-ray emission in binaries are very diverse. my current understanding is that they divide u... | gamma-ray emission from binaries in context |
the green bank north celestial cap (gbncc) pulsar survey will cover the entire northern sky (δ > -40°) at 350 mhz, and is one of the most uniform and sensitive all-sky pulsar surveys to date. we have created a pipeline to reanalyze gbncc survey data to take a 350 mhz census of all pulsars detected by the survey, reg... | the green bank north celestial cap pulsar survey. v. pulsar census and survey sensitivity |
using data from the large european array for pulsars, and the effelsberg telescope, we study the scintillation parameters of the millisecond pulsar psr j0613-0200 over a 7 yr timespan. the 'secondary spectrum' - the 2d power spectrum of scintillation - presents the scattered power as a function of time delay, and conta... | measuring interstellar delays of psr j0613-0200 over 7 yr, using the large european array for pulsars |
the remarkable null pulse coincident with the 2016 glitch in vela rotation indicates a dynamical event involving the crust and the magnetosphere of the neutron star. we propose that a crustal quake associated with the glitch strongly disturbed the vela magnetosphere and thus interrupted its radio emission. we present t... | a quake quenching the vela pulsar |
previous studies have shown that the radiation emitted by a rapidly rotating magnetar embedded in a young supernova can greatly amplify its luminosity. these one-dimensional studies have also revealed the existence of an instability arising from the piling up of radiatively accelerated matter in a thin dense shell deep... | magnetar-powered supernovae in two dimensions. i. superluminous supernovae |
we report on observations of the pulsar/be star binary system psr j2032+4127/mt91 213 in the energy range between 100 {gev} and 20 {tev} with the very energetic radiation imaging telescope array and major atmospheric gamma imaging cherenkov telescope arrays. the binary orbit has a period of approximately 50 years, with... | periastron observations of tev gamma-ray emission from a binary system with a 50-year period |
we demonstrate the blind interferometric detection and localization of two fast radio bursts (frbs) with subarcminute precision on the 400 m baseline between the canadian hydrogen intensity mapping experiment (chime) and the chime pathfinder. in the same spirit as very long baseline interferometry (vlbi), the telescope... | a synoptic vlbi technique for localizing nonrepeating fast radio bursts with chime/frb |
fast reconnection operating in magnetically dominated plasmas is often invoked in models for magnetar giant flares, for magnetic dissipation in pulsar winds, or to explain the gamma-ray flares observed in the crab nebula; hence, its investigation is of paramount importance in high-energy astrophysics. here we study, by... | fast reconnection in relativistic plasmas: the magnetohydrodynamics tearing instability revisited |
the structure of a light quark star is studied within a new two-flavor nambu-jona-lasinio model. by retaining the contribution from the vector term in the fierz-transformed lagrangian, a two-solar-mass pure quark star is achieved. to overcome the disadvantage of three-momentum truncation in the regularization procedure... | nonstrange quark stars from an njl model with proper-time regularization |
we investigate neutron star moments of inertia from bayesian posterior probability distributions of the nuclear equation of state that incorporate information from microscopic many-body theory and empirical data of finite nuclei. we focus on psr j0737-3039a and predict that for this 1.338 m⊙ neutron star the moment of ... | predicting the moment of inertia of pulsar j0737-3039a from bayesian modeling of the nuclear equation of state |
it is generally held that >100 tev emission from astrophysical objects unambiguously demonstrates the presence of pev protons or nuclei, due to the unavoidable klein-nishina suppression of inverse compton emission from electrons. however, in the presence of inverse compton dominated cooling, hard high-energy electro... | ultra-high energy inverse compton emission from galactic electron accelerators |
context. central compact objects (ccos) in supernova remnants are isolated thermally emitting neutron stars (nss). they are most probably characterized by a magnetic field strength that is roughly two orders of magnitude lower than that of most of the radio and accreting pulsars. the thermal emission of ccos can be mod... | the neutron star in hess j1731-347: central compact objects as laboratories to study the equation of state of superdense matter |
two energetic hard x-ray bursts from the rotation-powered pulsar psr j1119-6127 recently triggered the fermi and swift space observatories. we have performed in-depth spectral and temporal analyses of these two events. our extensive searches in both observatories’ data for lower luminosity bursts uncovered 10 additiona... | magnetar-like x-ray bursts from a rotation-powered pulsar, psr j1119-6127 |
we present a systematic study of the unbinned, photon-by-photon likelihood technique which can be used as an alternative method to analyse phase-dependent, x-ray spectro-polarimetric observations obtained with ixpe and other photoelectric polarimeters. we apply the unbinned technique to models of the luminous x-ray pul... | unbinned likelihood analysis for x-ray polarization |
we report on the spectral behavior of the first galactic ultraluminous x-ray pulsar swift j0243.6+6124 with nustar observations during its 2017-2018 outburst. at sub-eddington levels, the source spectrum is characterized by three emission components: from the accretion column, the hot spot, and a broad iron line emissi... | super-eddington accretion onto the galactic ultraluminous x-ray pulsar swift j0243.6+6124 |
in anticipation of a ligo detection of a black hole/neutron star merger, we expand on the intriguing possibility of an electromagnetic counterpart. black hole/neutron star mergers could be disappointingly dark since most black holes will be large enough to swallow a neutron star whole, without tidal disruption and with... | black hole pulsar |
the propeller regime has been studied using axisymmetric numerical simulations, where matter accretes from a thin turbulent disk and interacts with a rotating magnetized star. a wide range of propeller strengths has been studied, from very strong (where the magnetosphere rotates much more rapidly than the inner disk) t... | properties of strong and weak propellers from mhd simulations |
curvature radiation is a natural candidate for the emission mechanism of fast radio burs (frb). however, frb spectra have structure with δν/ν ∼ 0.03-0.2, inconsistent with the very smooth spectrum of curvature radiation. although this spectral structure might be attributed to chromatic scintillation or lensing, in four... | coherent plasma-curvature radiation in frb |
in this paper we provide a comprehensive derivation of the energy density in the stochastic gravitational-wave background $\omega_\mathrm{gw}(f)$, and show how this quantity is measured in ground-based detectors such as laser interferometer gravitational-wave observatory (ligo), space-based laser interferometer space a... | understanding $\\omega_\\mathrm{gw}(f)$ in gravitational wave experiments |
we report the detection of pulsed gamma-ray emission from the geminga pulsar (psr j0633+1746) between 15 gev and 75 gev. this is the first time a middle-aged pulsar has been detected up to these energies. observations were carried out with the magic telescopes between 2017 and 2019 using the low-energy threshold sum-tr... | detection of the geminga pulsar with magic hints at a power-law tail emission beyond 15 gev |
context. the discovery of extended gamma-ray emission toward a number of middle-aged pulsars suggests the possibility of long-lived particle confinement beyond the classical pulsar wind nebula (pwn) stage. how this emerging source class can be extrapolated to a galactic population remains unclear.aims: we aim to evalua... | population synthesis of pulsar wind nebulae and pulsar halos in the milky way. predicted contributions to the very-high-energy sky |
the near-earth (within ∼100 pc) supernova explosions in the past several million years can cause the global deposition of radioactive elements (e.g., 60fe) on earth. the remnants of such supernovae are too old to be easily identified. it is therefore of great interest to search for million-year-old near-earth neutron s... | the nearest neutron star candidate in a binary revealed by optical time-domain surveys |
the fermi bubbles are giant, γ-ray-emitting lobes emanating from the nucleus of the milky way discovered in ~1-100 gev data collected by the large area telescope on board the fermi gamma-ray space telescope. previous work has revealed substructure within the fermi bubbles that has been interpreted as a signature of col... | gamma-ray emission from the sagittarius dwarf spheroidal galaxy due to millisecond pulsars |
we examine the chandrasekhar limit for white dwarfs in f (r ) gravity, with a simple polytropic equation of state describing stellar matter. we use the most popular f (r ) gravity model, namely the f (r )=r +α r2 gravity, and calculate the parameters of the stellar configurations with polytropic equation of state of th... | maximal masses of white dwarfs for polytropes in r2 gravity and theoretical constraints |
accretion-induced collapse (aic) of massive white dwarfs (wds) has been proposed as an important way for the formation of neutron star (ns) systems. an oxygen-neon (one) wd that accretes h-rich material from a red-giant (rg) star may experience the aic process, eventually producing millisecond pulsars (msps), known as ... | formation of millisecond pulsars with long orbital periods by accretion-induced collapse of white dwarfs |
we follow the idea that the qcd phase diagram may be described by a crossover from a hadron resonance gas to perturbative qcd using the switch function ansatz of albright, kapusta, and young [phys. rev. c 90, 024915 (2014), 10.1103/physrevc.90.024915]. while the switch function could be calibrated at vanishing baryon c... | neutron stars with crossover to color superconducting quark matter |
m82 x-2 is the first pulsating ultraluminous x-ray source discovered. the luminosity of these extreme pulsars, if isotropic, implies an extreme mass transfer rate. an alternative is to assume a much lower mass transfer rate, but with an apparent luminosity boosted by geometrical beaming. only an independent measurement... | orbital decay in m82 x-2 |
a new type of embedding class-i metric representing anisotropic fluid distribution is presented in this paper. the new solution satisfies tov equation and does represent a static stellar configuration. this new solution is an interesting hybrid solution where gttis of schwarzschild interior and grris of vaidya-tikekar.... | a hybrid space-time of schwarzschild interior and vaidya-tikekar solution as an embedding class i |
the 1-70 kev persistent spectra of 15 magnetars, observed with suzaku from 2006 to 2013, were studied as a complete sample. combined with early nustar observations of four hard x-ray emitters, nine objects showed a hard power-law emission dominating at ≳ 10 kev with the 15-60 kev flux of ∼1-11× {10}-11 erg s-1 cm-2. th... | magnetar broadband x-ray spectra correlated with magnetic fields: suzaku archive of sgrs and axps combined with nustar, swift, and rxte |
the pulsar radio emission originates from regions below 10% of the light cylinder radius. this requires a mechanism where coherent emission is excited in relativistic pair plasma with frequency ν _{cr} which is below the plasma frequency ν_{°} i.e. ν _{cr} < ν_{°}. a possible model for the emission mechanism is char... | nature of coherent radio emission from pulsars |
the density-dependent relativistic hartree-fock (ddrhf) theory is extended to include δ isobars for the study of dense nuclear matter and neutron stars. to this end, we solve the rarita-schwinger equation for spin-3/2 particle. both the direct and exchange terms of the δ isobars' self-energies are evaluated in detail. ... | δ (1232 ) effects in density-dependent relativistic hartree-fock theory and neutron stars |
context. the relationship between the dispersion measures (dms) and redshifts of fast radio bursts (frbs) is of scientific interest. upcoming commensal surveys may detect and localise many frbs to the sub-arcsecond angular resolutions required for accurate redshift determination. meanwhile, it is important to exploit s... | constraining the redshifts of unlocalised fast radio bursts |
globular clusters host a variety of lower-luminosity (lx < 1035 erg s-1) x-ray sources, including accreting neutron stars (nss) and black holes (bhs), millisecond pulsars (msps), cataclysmic variables, and chromospherically active binaries. in this paper, we provide a comprehensive catalog of more than 1100 x-ray so... | the maveric survey: chandra/acis catalog of faint x-ray sources in 38 galactic globular clusters |
in general relativity gravitational waves propagate at the speed of light; however, in alternative theories of gravity that might not be the case. we investigate the effects of a modified speed of gravity, ct2, on the b modes of the cosmic microwave background (cmb) anisotropy in polarization. we find that a departure ... | measuring the speed of cosmological gravitational waves |
context. rapidly rotating neutron stars blow a relativistic, magnetized wind mainly composed of electron-positron pairs. the free expansion of the wind terminates far from the neutron star where a weakly magnetized pulsar wind nebula forms, implying efficient magnetic dissipation somewhere upstream.aims: the wind curre... | dissipation of the striped pulsar wind |
we compute the gravitational waveform from a binary system in scalar-tensor gravity at 2pn relative order. we restrict our calculation to nonspinning binary systems on quasicircular orbits and compute the spin-weighted spherical modes of the radiation. the evolution of the phase of the waveform is computed in the time ... | gravitational waveforms in scalar-tensor gravity at 2pn relative order |
the identification of the ultraluminous x-ray source (ulx) x-2 in m82 as an accreting pulsar has shed new light on the nature of a subset of ulxs, while rising new questions on the nature of the super-eddington accretion. here, by numerically solving the torque equation of the accreting pulsar within the framework of t... | nustar j095551+6940.8: a highly magnetized neutron star with super-eddington mass accretion |
a charged particle moving through a medium emits cherenkov radiation when its velocity exceeds the phase velocity of light in that medium. under the influence of a strong electromagnetic field, quantum fluctuations can become polarized, imbuing the vacuum with an effective anisotropic refractive index and allowing the ... | cherenkov radiation from the quantum vacuum |
due to ionosphere absorption and the interference by natural and artificial radio emissions, ground observation of the sky at the decameter or longer is very difficult. this unexplored part of electromagnetic spectrum has the potential of great discoveries, notably in the study of cosmic dark ages and dawn, but also in... | discovering the sky at the longest wavelengths with small satellite constellations |
numerous extended sources around galactic pulsars have shown significant γ -ray emission from gev to tev energies, revealing hundreds of tev energy electrons scattering off of the underlying photon fields through inverse compton scattering (ics). hawc tev gamma-ray observations of few-degree extended emission around th... | investigating γ -ray halos around three hawc bright sources in f e r m i -lat data |
accurate measurements of the masses of neutron stars are necessary to test binary evolution models, and to constrain the neutron star equation of state. in pulsar binaries with no measurable post-keplerian parameters, this requires an accurate estimate of the binary system's inclination and the radial velocity of the c... | measuring the mass of the black widow psr j1555-2908 |
psr b0950+08 is a bright nonrecycled pulsar whose single-pulse fluence variability is reportedly large. based on observations at two widely separated frequencies, 55 mhz (nenufar) and 1.4 ghz (westerbork synthesis radio telescope), we review the properties of these single pulses. we conclude that they are more similar ... | dual-frequency single-pulse study of psr b0950+08 |
fast radio bursts (frbs) are extragalactic radio transients of extraordinary luminosity. studying the diverse temporal and spectral behaviour recently observed in a number of frbs may help to determine the nature of the entire class. for example, a fast spinning or highly magnetised neutron star (ns) might generate the... | a fast radio burst with submillisecond quasi-periodic structure |
the detection of ∼1.5-3.2 myr old 60fe on earth indicates recent nearby core-collapse supernovae. for supernovae in multiple stars, the primary stars may become neutron stars, while former companions may become unbound and become runaway stars. we wrote software for tracing back the space motion of runaway and neutron ... | a nearby recent supernova that ejected the runaway star ζ oph, the pulsar psr b1706-16, and 60fe found on earth |
the center of the galaxy is one of the prime targets in the search for a signal of annihilating (or decaying) dark matter. if such a signal were to be detected, it would shed light on one of the biggest mysteries in physics today: what is dark matter? fundamental properties of the particle nature of dark matter, such a... | the fermi–lat galactic center excess: evidence of annihilating dark matter? |
thanks to advances in γ -ray astronomy and precise measurements of cosmic ray (cr) properties, the last decade has witnessed significant progresses in our understanding of the origin of galactic crs. in particular, gev crs have been associated with supernova remnants (snrs) with soft γ -ray spectra, while there is evid... | the origin of galactic cosmic rays |
due to ionosphere absorption and the interference of natural and artificial radio emissions, astronomical observation from the ground becomes very difficult at the wavelengths of decametre or longer, which we shall refer to as the ultralong wavelengths. this unexplored part of the electromagnetic spectrum has the poten... | discovering the sky at the longest wavelengths with a lunar orbit array |
the secondary component of the gw190814 event left us with a question, “whether it is a supermassive neutron star or lightest black-hole?” recently, fattoyev et al. obtained an energy density functional (edf) named as bigapple, which reproduces the mass of the neutron star is 2.60 m⊙ which is well consistent with gw190... | bigapple force and its implications to finite nuclei and astrophysical objects |
we present here a simple, systematic method for determining the correct global rotation count of a radio pulsar; an essential step for the derivation of an accurate phase-coherent ephemeris. we then build on this method by developing a new algorithm for determining the global rotational count for pulsars with sparse ti... | an algorithm for determining the rotation count of pulsars |
based on relativistic mean field (rmf) models, we study finite λ-hypernuclei and massive neutron stars. the effective n-n interactions pk1 and tm1 are adopted, while the n-λ interactions are constrained by reproducing the binding energy of λ-hyperon at 1s orbit of {}{{λ }}{}40{ca}. it is found that the λ-meson coupling... | massive neutron stars and λ-hypernuclei in relativistic mean field models |
we present charged anisotropic durgapal iv interior solutions of the general relativistic field equations in curvature coordinates. these exact solutions can be used to model stable and well-behaved compact stars. using these solutions we have presented models of well-known neutron and quark stars such as psr j1903+032... | some analytic models of relativistic compact stars |
we collect new and archival optical observations of nine “black-widow” millisecond pulsar binaries. new measurements include direct imaging with the keck, gemini-s, mdm, and las cumbres observatory 2 m telescopes. this is supplemented by synthesized colors from keck long-slit spectra. four black-widow optical companion... | multiband optical light curves of black-widow pulsars |
the pulsar radio emission is commonly associated with the plasma outflow in the open field line tube; then a pencil beam is emitted along the pulsar magnetic axis. observations suggest that there is an additional radio emission mechanism specific for pulsars with high magnetic field at the light cylinder. these pulsars... | radio emission of the crab and crab-like pulsars |
among efforts to detect gravitational radiation, pulsar timing arrays are uniquely poised to detect “memory” signatures, permanent perturbations in spacetime from highly energetic astrophysical events such as mergers of supermassive black hole binaries. the north american nanohertz observatory for gravitational waves (... | nanograv constraints on gravitational wave bursts with memory |
in the standard gravitational lensing scenario, rays from a background source are bent in the direction of a foreground lensing mass distribution. diverging lens behaviour produces deflections in the opposite sense to gravitational lensing, and is also of astrophysical interest. in fact, diverging lensing due to compac... | two families of astrophysical diverging lens models |
in this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the icecube neutrino telescope are presented. in contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the informati... | searches for time-dependent neutrino sources with icecube data from 2008 to 2012 |
high brightness temperature radio transients such as pulsars and fast radio bursts (frbs) require the coherent radiation of particles. the antenna class of coherent radiation models require a large number of charged particles radiating in phase, therefore the particles must be spatially confined and have well-aligned v... | coherent curvature radiation: maximum luminosity and high-energy emission |
psr j1713+0747 is one of the most precisely timed pulsars in the international pulsar timing array experiment. this pulsar showed an abrupt profile shape change between 2021 april 16, (mjd 59320) and 2021 april 17 (mjd 59321). in this paper, we report the results from multi-frequency observations of this pulsar carried... | evidence for profile changes in psr j1713+0747 using the ugmrt |
with strong evidence of a common-spectrum stochastic process in the most recent data sets from the nanograv collaboration, the european pulsar timing array (pta), parkes pta, and the international pta, it is crucial to assess the effects of the several astrophysical and cosmological sources that could contribute to the... | disentangling multiple stochastic gravitational wave background sources in pta data sets |
over a dozen millisecond pulsars are ablating low-mass companions in close binary systems. in the original `black widow', the eight-hour orbital period eclipsing pulsar psr j1959+2048 (psr b1957+20)1, high-energy emission originating from the pulsar2 is irradiating and may eventually destroy3 a low-mass companion. thes... | a 62-minute orbital period black widow binary in a wide hierarchical triple |
the cooling mechanisms of a neutron star (hereafter referred to as ns) have the potential to reveal important features of superdense matter. the values of the surface temperatures are known for a good sample of nss aged ≤ 106 years and, with some exceptions, can be explained through standard cooling mechanisms (neutrin... | internal heating mechanisms in neutron stars |
data from the fermi large area telescope suggests that there is an extended excess of gev gamma-ray photons in the inner galaxy. identifying potential astrophysical sources that contribute to this excess is an important step in verifying whether the signal originates from annihilating dark matter. in this paper, we foc... | distinguishing dark matter from unresolved point sources in the inner galaxy with photon statistics |
supermassive black hole-host galaxy relations are key to the computation of the expected gravitational wave background (gwb) in the pulsar timing array (pta) frequency band. it has been recently pointed out that standard relations adopted in gwb computations are in fact biased-high. we show that when this selection bia... | selection bias in dynamically measured supermassive black hole samples: consequences for pulsar timing arrays |
we have modelled the near-infrared to radio images of the crab nebula with a bayesian sed model to simultaneously fit its synchrotron, interstellar (is), and supernova dust emission. we infer an is dust extinction map with an average av = 1.08 ± 0.38 mag, consistent with a small contribution ({≲ }22{{ per cent}}) to th... | the dust content of the crab nebula |
this article investigates the dust ion acoustic multi-shock wave excitations in weakly relativistic multi-component plasma by assuming nonthermal, nonextensive electrons and positrons, relativistic ion fluid having kinetic viscosity and immobile dust. burgers equation is derived to investigate such excitations by apply... | dust ion acoustic multi-shock wave excitations in the weakly relativistic plasmas with nonthermal nonextensive electrons and positrons |
we present a timing analysis of multiple xmm-newton and nustar observations of the ultra-luminous pulsar ngc 7793 p13 spread over its 65 d variability period. we use the measured pulse periods to determine the orbital ephemeris, confirm a long orbital period with porb = 63.9+0.5-0.6 d, and find an eccentricity of e ≤ 0... | a tale of two periods: determination of the orbital ephemeris of the super-eddington pulsar ngc 7793 p13 |
a construction and analysis of an exact solution to einstein's field equations with the source of matter being an anisotropic fluid that allows to model compact stars with a rate of compactness u ≤0 .2061897680 of which the orders of magnitude of pressure and density match those of neutron stars. the model is physicall... | a possible representation for the neutron star psr j0437-4715 |
context. high-precision pulsar-timing experiments are affected by temporal variations of the dispersion measure (dm), which are related to spatial variations in the interstellar electron content and the varying line of sight to the source. correcting for dm variations relies on the cold-plasma dispersion law which stat... | first detection of frequency-dependent, time-variable dispersion measures |
the parkes pulsar timing array (ppta) project monitors two dozen millisecond pulsars (msps) in order to undertake a variety of fundamental physics experiments using the parkes 64-m radio telescope. since 2017 june, we have been undertaking commensal searches for fast radio bursts (frbs) during the msp observations. her... | commensal discovery of four fast radio bursts during parkes pulsar timing array observations |
at high-energy γ-rays (>100 mev), the large area telescope (lat) on the fermi satellite already detected more than 145 rotation-powered pulsars (rpps), while the number of pulsars seen at soft γ-rays (20 kev-30 mev) remained small. we present a catalogue of 18 non-recycled rpps from which presently non-thermal pulse... | the soft γ-ray pulsar population: a high-energy overview |
recent studies of low redshift type ia supernovae (sn ia) indicate that half explode from less than chandrasekhar mass white dwarfs, implying ignition must proceed from something besides the canonical criticality of chandrasekhar mass sn ia progenitors. we show that 1-100 pev mass asymmetric dark matter, with imminentl... | dark matter ignition of type ia supernovae |
we outline a model of the crab pulsar wind nebula with two different populations of synchrotron emitting particles, arising from two different acceleration mechanisms: (i) component-i due to fermi-i acceleration at the equatorial portion of the termination shock, with particle spectral index pi ≈ 2.2 above the injectio... | interpreting crab nebula's synchrotron spectrum: two acceleration mechanisms |
nearby sources may contribute to cosmic-ray electron (cre) structures at high energies. recently, the first dampe results on the cre flux hinted at a narrow excess at energy ∼1.4 tev . we show that in general a spectral structure with a narrow width appears in two scenarios. the first is spectrum broadening for the con... | origins of sharp cosmic-ray electron structures and the dampe excess |
context. the existence of 2 m⊙ pulsars puts very strong constraints on the equation of state (eos) of neutron stars (nss) with hyperon cores, which can be satisfied only by special models of hadronic matter. the radius-mass relation for these models is sufficiently specific that it could be subjected to an observationa... | neutron stars with hyperon cores: stellar radii and equation of state near nuclear density |
we report on an effort to extract and monitor interstellar scintillation parameters in regular timing observations collected for the north american nanohertz observatory for gravitational waves pulsar timing array. scattering delays are measured by creating dynamic spectra for each pulsar and observing epoch of wide-ba... | the nanograv nine-year data set: monitoring interstellar scattering delays |
we present an extended grid of mean three-dimensional (3d) spectra for low-mass, pure-hydrogen atmosphere da white dwarfs (wds). we use co5bold radiation-hydrodynamics 3d simulations covering teff = 6000-11,500 k and log g = 5-6.5 (g in cm s-2) to derive analytical functions to convert spectroscopically determined 1d t... | 3d model atmospheres for extremely low-mass white dwarfs |
we present initial pulsar results from the first station of the long wavelength array (lwa1) obtained during the commissioning period of lwa1 and in early science results. we present detections of periodic emission from 44 previously known pulsars, including 3 millisecond pulsars. the effects of the interstellar medium... | pulsar observations using the first station of the long wavelength array and the lwa pulsar data archive |
massive black hole binaries (mbhbs) are thought to be the main source of gravitational waves (gws) in the low-frequency domain surveyed by ongoing and forthcoming pulsar timing array campaigns and future space-borne missions, such as elisa. however, many low-redshift mbhbs in realistic astrophysical environments may no... | post-newtonian evolution of massive black hole triplets in galactic nuclei - i. numerical implementation and tests |
we present a new study of the rayleigh-taylor unstable regime of accretion on to rotating magnetized stars in a set of high grid resolution three-dimensional magnetohydrodynamic simulations performed in low-viscosity discs. we find that the boundary between the stable and unstable regimes is determined almost entirely ... | boundary between stable and unstable regimes of accretion. ordered and chaotic unstable regimes |
many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. these are likely due to the rapid dissipation of electromagnetic energy in a highly magn... | kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria |
psr j0537-6910, also known as the big glitcher, is the most prolific glitching pulsar known, and its spin-induced pulsations are only detectable in x-ray. we present results from analysis of 2.7 yr of nicer timing observations, from 2017 august to 2020 april. we obtain a rotation phase-connected timing model for the en... | return of the big glitcher: nicer timing and glitches of psr j0537-6910 |
the dark matter particle explorer (dampe) experiment has recently announced the first results for the measurement of total electron plus positron fluxes between 25 gev and 4.6 tev. a spectral break at about 0.9 tev and a tentative peak excess around 1.4 tev have been found. however, it is very difficult to reproduce bo... | a simple and natural interpretations of the dampe cosmic-ray electron/positron spectrum within two sigma deviations |
we report on a search for high-energy counterparts to fast radio bursts (frbs) with the fermi gamma-ray burst monitor, fermi large area telescope, and the neil gehrels swift observatory burst alert telescope. we find no significant associations for any of the 23 frbs in our sample, but report upper limits to the high-e... | a search for high-energy counterparts to fast radio bursts |
pulsars can act as an excellent probe of the milky way magnetic field. the average strength of the galactic magnetic field component parallel to the line of sight can be estimated as $\langle b_\parallel \rangle = 1.232 \, \text{rm}/\text{dm}$ , where rm and dm are the rotation and dispersion measure of the pulsar. how... | magnetic fields in the milky way from pulsar observations: effect of the correlation between thermal electrons and magnetic fields |
magnetic field evolution in neutron-star crusts is driven by the hall effect and ohmic dissipation, for as long as the crust is sufficiently strong to absorb maxwell stresses exerted by the field and thus makes the momentum equation redundant. for the strongest neutron-star fields, however, stresses build to the point ... | axisymmetric magneto-plastic evolution of neutron-star crusts |
context. interstellar scintillation (iss) of pulsar emission can be used both as a probe of the ionized interstellar medium (iism) and cause corruptions in pulsar timing experiments. of particular interest are so-called scintillation arcs which can be used to measure time-variable interstellar scattering delays directl... | pulsar scintillation studies with lofar. i. the census |
we report the results of an observational campaign using the effelsberg 100-m telescope of the pulsars j1746-2849, j1746-2850, j1746-2856, and j1745-2912 located in the central molecular zone (cmz) close to the galactic centre in order to study rotation measure (rm) variations. we report for the first time the rm value... | rotation measure variations in galactic centre pulsars |
as one of the major components of the interstellar medium, the ionized gas in our milky way, especially the low-density diffuse component, has not been extensively observed in the radio band. the galactic plane pulsar snapshot (gpps) survey covers the sky area within the galactic latitude of ±10° around the galactic pl... | peering into the milky way by fast: ii. ionized gas in the inner galactic disk revealed by the piggyback line observations of the fast gpps survey |
gravitational waves are ripples in the fabric of spacetime that are caused by events such as the merging of black holes. in principle, many types of events occur that could create gravitational waves with frequencies ranging from as high as a few kilohertz to as low as a few nanohertz. sources of gravitational waves in... | seeing the gravitational wave universe |
we present the largest single survey to date of average profiles of radio pulsars, observed and processed using the same telescope and data reduction software. specifically, we present measurements for 1170 pulsars, observed by the thousand pulsar array programme at the 64-dish sarao meerkat radio telescope, in a frequ... | the thousand pulsar array program on meerkat - ix. the time-averaged properties of the observed pulsar population |
we investigate pre-merger coherent radio emission from neutron star mergers arising due to the magnetospheric interaction between compact objects. we consider two plausible radiation mechanisms, and show that if one neutron star has a surface magnetic field bs ≥ 1012g, coherent millisecond radio bursts with characteris... | pulsar revival in neutron star mergers: multimessenger prospects for the discovery of pre-merger coherent radio emission |
psr j1012+5307, a millisecond pulsar in orbit with a helium white dwarf (wd), has been timed with high precision for about 25 yr. one of the main objectives of this long-term timing is to use the large asymmetry in gravitational binding energy between the neutron star and the wd to test gravitational theories. such tes... | very long baseline astrometry of psr j1012+5307 and its implications on alternative theories of gravity |
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