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fast radio burst frb 20180916b in its host galaxy sdss j015800.28+654253.0 at 149 mpc is by far the closest-known frb with a robust host galaxy association. the source also exhibits a 16.35 day period in its bursting. here we present optical and infrared imaging as well as integral field spectroscopy observations of fr... | the 60 pc environment of frb 20180916b |
several pulsar timing array (pta) experiments such as nanograv and ppta reported evidence of a gravitational wave background at the nano-hz frequency band recently. this signal can originate from scalar-induced gravitational waves (sigw) generated by the enhanced curvature perturbation. here we perform a joint likeliho... | high frequency gravitational waves from pulsar timing arrays |
pulsar timing arrays (ptas) have recently found evidence for a nanohertz-frequency stochastic gravitational-wave background (sgwb). constraining its spectral characteristics will reveal its origins. in order to achieve this, we must understand how data and modeling conditions in each pulsar influence the precision and ... | rapid refitting techniques for bayesian spectral characterization of the gravitational wave background using pulsar timing arrays |
we report the detection of 72 new pulses from the repeating fast radio burst frb 121102 in breakthrough listen c-band (4-8 ghz) observations at the green bank telescope. the new pulses were found with a convolutional neural network in data taken on 2017 august 26, where 21 bursts have been previously detected. our tech... | fast radio burst 121102 pulse detection and periodicity: a machine learning approach |
locating the critical endpoint of qcd and the region of a first-order phase transition at finite baryon chemical potential is an active research area for qcd matter. we provide a gravitational dual description of qcd matter at finite baryon chemical potential μb and finite temperature using the nonperturbative approach... | probing qcd critical point and induced gravitational wave by black hole physics |
we present a new analysis of the profile data from the 47 millisecond pulsars comprising the 12.5 yr data set of the north american nanohertz observatory for gravitational waves, which is presented in a parallel paper (alam et al., hereafter ng12.5). our reprocessing is performed using "wideband" timing methods, which ... | the nanograv 12.5 yr data set: wideband timing of 47 millisecond pulsars |
we report the discovery of four fast radio bursts (frbs) in the ongoing survey for pulsars and extragalactic radio bursts at the parkes radio telescope: frbs 150610, 151206, 151230 and 160102. our real-time discoveries have enabled us to conduct extensive, rapid multimessenger follow-up at 12 major facilities sensitive... | the survey for pulsars and extragalactic radio bursts - ii. new frb discoveries and their follow-up |
we obtain a new anisotropic solution for spherically symmetric spacetimes by analyzing the karmarkar embedding condition. for this purpose we construct a suitable form of one of the gravitational potentials to obtain a closed form solution. this form of the remaining gravitational potential allows us to solve the embed... | anisotropic fluid spheres of embedding class one using karmarkar condition |
the next generation of space-borne gravitational wave detectors may detect gravitational waves from extreme mass-ratio inspirals with primordial black holes. to produce primordial black holes which contribute a non-negligible abundance of dark matter and are consistent with the observations, a large enhancement in the ... | primordial black holes and second order gravitational waves from ultra-slow-roll inflation |
the nanograv collaboration recently reported a strong evidence for a stochastic common-spectrum process in the pulsar-timing data. we evaluate the evidence of interpreting this process as mergers of super massive black hole binaries and/or various stochastic gravitational-wave background sources in the early universe, ... | evidence for different gravitational-wave sources in the nanograv dataset |
the canadian hydrogen intensity mapping experiment (chime) is a drift scan radio telescope operating across the 400-800 mhz band. chime is located at the dominion radio astrophysical observatory near penticton, bc, canada. the instrument is designed to map neutral hydrogen over the redshift range 0.8-2.5 to constrain t... | an overview of chime, the canadian hydrogen intensity mapping experiment |
using full 3+1 dimensional general-relativistic hydrodynamic simulations of equal- and unequal-mass neutron-star binaries with properties that are consistent with those inferred from the inspiral of gw170817, we perform a detailed study of the quark-formation processes that could take place after merger. we use three e... | quark formation and phenomenology in binary neutron-star mergers using v-qcd |
we present the set of deep neutron star interior composition explorer (nicer) x-ray timing observations of the nearby rotation-powered millisecond pulsars psrs j0437-4715, j0030+0451, j1231-1411, and j2124-3358, selected as targets for constraining the mass-radius relation of neutron stars and the dense matter equation... | constraining the neutron star mass-radius relation and dense matter equation of state with nicer. i. the millisecond pulsar x-ray data set |
the present work is focused on the investigation of the existence of compact structures describing anisotropic matter distributions within the framework of modified gravity theories, specifically f (r ,t ) gravity theory. additionally, we have taken f (r ,t ) as a linear function of the ricci scalar r and the trace of ... | study of anisotropic strange stars in f (r ,t ) gravity: an embedding approach under the simplest linear functional of the matter-geometry coupling |
a cosmological first-order phase transition is expected to produce a stochastic gravitational wave background. if the phase transition temperature is on the mev scale, the power spectrum of the induced stochastic gravitational waves peaks around nanohertz frequencies, and can thus be probed with high-precision pulsar t... | constraining cosmological phase transitions with the parkes pulsar timing array |
the hydrogen intensity and real-time analysis experiment (hirax) is a new 400{800mhz radio interferometer under development for deployment in south africa. hirax will comprise 1024 six meter parabolic dishes on a compact grid and will map most of the southern sky over the course of four years. hirax has two primary sci... | hirax: a probe of dark energy and radio transients |
strong evidence for the helling-downs correlation curves have been reported by multiple pulsar timing array (pta) collaborations in middle 2023. in this work, we investigate the graviton mass bounds by analyzing the observational data of the overlap ruduction functions from the nanograv 15-year data release and cpta fi... | unveiling the graviton mass bounds through analysis of 2023 pulsar timing array data releases |
tenuous wind bubbles, which are formed by the spin-down activity of central compact remnants, are relevant in some models of fast radio bursts (frbs) and superluminous supernovae (sne). we study their high-energy signatures, focusing on the role of pair-enriched bubbles produced by young magnetars, rapidly rotating neu... | a burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants |
radio pulsars provide us with some of the most stable clocks in the universe. nevertheless several pulsars exhibit sudden spin-up events, known as glitches. more than forty years after their first discovery, the exact origin of these phenomena is still open to debate. it is generally thought that they are observational... | models of pulsar glitches |
we show that the periodic frb 180916.j0158+65 can be interpreted by invoking an interacting neutron star binary system with an orbital period of ∼16 days. the frbs are produced by a highly magnetized pulsar, whose magnetic field is "combed" by the strong wind from a companion star, either a massive star or a millisecon... | a binary comb model for periodic fast radio bursts |
the discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. in this paper, we present follow-up observations of the gravitational wave event gw170817 and its electromagn... | follow up of gw170817 and its electromagnetic counterpart by australian-led observing programmes |
we review the current understanding of the diffuse gamma-ray background (dgrb). the dgrb is what remains of the total measured gamma-ray emission after the subtraction of the resolved sources and of the diffuse galactic foregrounds. it is interpreted as the cumulative emission of sources that are not bright enough to b... | the nature of the diffuse gamma-ray background |
we present results of the coordinated observing campaign that made the first subarcsecond localization of a fast radio burst, frb 121102. during this campaign, we made the first simultaneous detection of an frb burst using multiple telescopes: the vla at 3 ghz and the arecibo observatory at 1.4 ghz. of the nine bursts ... | a multi-telescope campaign on frb 121102: implications for the frb population |
we analyze the polarization content of gravitational waves in horndeski theory. besides the familiar plus and cross polarizations in einstein's general relativity, there is one more polarization state which is the mixture of the transverse breathing and longitudinal polarizations. the additional mode is excited by the ... | polarizations of gravitational waves in horndeski theory |
in this paper we study online reinforcement learning (rl) in partially observable dynamical systems. we focus on the predictive state representations (psrs) model, which is an expressive model that captures other well-known models such as partially observable markov decision processes (pomdp). psr represents the states... | pac reinforcement learning for predictive state representations |
astrophysical observations of neutron stars probe the structure of dense nuclear matter and have the potential to reveal phase transitions at high densities. most recent analyses are based on parametrized models of the equation of state with a finite number of parameters and occasionally include extra parameters intend... | phase transition phenomenology with nonparametric representations of the neutron star equation of state |
we study the prospects of detection at terrestrial and space interferometers, as well as at pulsar timing array experiments, of a stochastic gravitational wave background which can be produced in models of axion inflation. this potential signal, and the development of these experiments, open a new window on inflation o... | gravitational waves at interferometer scales and primordial black holes in axion inflation |
the symmetry energy and its density dependence are pivotal for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. recently, prex-ii reported a value of 0.283 ±0.071 fm for the neutron-... | detailed examination of astrophysical constraints on the symmetry energy and the neutron skin of 208pb with minimal modeling assumptions |
ultralight primordial black holes (pbhs)(≲109g) completely evaporate via hawking radiation (hr) and produce all the particles in a given theory regardless of their other interactions. if the right handed (rh) neutrinos are produced from pbh evaporation, successful baryogenesis via leptogenesis predicts mass scale of rh... | baryogenesis from ultralight primordial black holes and strong gravitational waves from cosmic strings |
the nasa telescope nicer has recently measured x-ray emissions from the heaviest of the precisely known two-solar mass neutron stars, psr j0740 + 6620. analysis of the data [astrophys. j. lett. 918, l28 (2021), 10.3847/2041-8213/ac089b, astrophys. j. lett. 918, l27 (2021), 10.3847/2041-8213/ac0a81] suggests that psr j0... | large and massive neutron stars: implications for the sound speed within qcd of dense matter |
strongly magnetized, rapidly rotating neutron stars are contenders for the central engines of both long gamma-ray bursts (lgrbs) and hydrogen-poor superluminous supernovae (slsne-i). models for typical (minute long) lgrbs invoke magnetars with high dipole magnetic fields (bd ≳ 1015 g) and short spin-down times, slsne-i... | the diversity of transients from magnetar birth in core collapse supernovae |
we use stergioulas's rns code for investigating fast pulsars with equations of state (eoss) on the causality surface (where the speed of sound is equal to that of light) of the high-density eos parameter space satisfying all known constraints from both nuclear physics and astrophysics. we show that one possible explana... | gw190814's secondary component with mass 2.50-2.67 m⊙ as a superfast pulsar |
young and rotation-powered neutron stars (nss) are commonly observed as rapidly-spinning pulsars. they dissipate their rotational energy by emitting pulsar wind with electromagnetic radiation and spin down at a steady rate, according to the simple steadily-rotating magnetic dipole model. in reality, however, multiwavel... | observational diversity of magnetized neutron stars |
a metastable cosmic-string network is a generic consequence of many grand unified theories (guts) when combined with cosmic inflation. metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of gut monopoles. this leads to a network consisting of metastable long st... | stochastic gravitational-wave background from metastable cosmic strings |
in this paper, we discuss the impact of the following laboratory experiments and astrophysical observation of neutron stars (nss) on their equation of state (eos): (a) the new measurement of neutron skin thickness of 208pb, ${r}_{\mathrm{skin}}^{208}=0.29\pm 0.07$ fm by the prex-ii experiment; (b) the mass measurement ... | impact of prex-ii and combined radio/nicer/xmm-newton's mass-radius measurement of psr j0740+6620 on the dense-matter equation of state |
we present the first 2.5 yr of data from the meerkat pulsar timing array (mpta), part of meertime, a meerkat large survey project. the mpta aims to precisely measure pulse arrival times from an ensemble of 88 pulsars visible from the southern hemisphere, with the goal of contributing to the search, detection, and study... | the meerkat pulsar timing array: first data release |
the nicer collaboration recently reported the measurement of the mass and radius of a pulsar psr j0030+0451. we here use this new measurement to constrain one of the higher-order nuclear matter parameters $k_{\mathrm{sym,0}}$. we further combine the tidal measurement of the binary neutron star merger gw170817 by ligo/v... | measuring nuclear matter parameters with nicer and ligo/virgo |
primordial black holes (pbh) from peaks in the curvature power spectrum could constitute today an important fraction of the dark matter in the universe. at horizon reentry, during the radiation era, order one fluctuations collapse gravitationally to form black holes and, at the same time, generate a stochastic backgrou... | detecting the stochastic gravitational wave background from primordial black hole formation |
in this work we obtain an anisotropic neutron star solution by gravitational decoupling starting from a perfect fluid configuration which has been used to model the compact object psr j0348+0432. additionally, we consider the same solution to model the binary pulsar sax j1808.4-3658 and x-ray binaries her x-1 and cen x... | anisotropic neutron stars by gravitational decoupling |
observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, hii regions and bubbles, the milky way and nearby galaxies, galaxy clusters, and the cosmic web. a variety of approaches are used to investigate ... | observing interstellar and intergalactic magnetic fields |
we report the properties of more than 600 bursts (including cluster-bursts) detected from the repeating fast radio burst (frb) source frb 20201124a with the five-hundred-meter aperture spherical radio telescope during an extremely active episode on utc 2021 september 25-28, in a series of four papers. the observations ... | fast observations of an extremely active episode of frb 20201124a: i. burst morphology |
the collection of individually resolvable gravitational wave (gw) events makes up a tiny fraction of all gw signals that reach our detectors, while most lie below the confusion limit and are undetected. similarly to voices in a crowded room, the collection of unresolved signals gives rise to a background that is well-d... | stochastic gravitational-wave backgrounds: current detection efforts and future prospects |
the dark matter particle explorer (dampe), a high energy cosmic ray and $\gamma$-ray detector in space, has recently reported the new measurement of the total electron plus positron flux between 25 gev and 4.6 tev. a spectral softening at $\sim0.9$ tev and a tentative peak at $\sim1.4$ tev have been reported. we study ... | interpretations of the dampe electron data |
the mass of the dark matter particle is unknown, and may be as low as ∼1 0-22 ev . the lighter part of this range, below ∼ev , is relatively unexplored both theoretically and experimentally but contains an array of natural dark matter candidates. an example is the relaxion, a light boson predicted by cosmological solut... | dark matter direct detection with accelerometers |
using two-dimensional particle-in-cell simulations, we characterize the energy spectra of particles accelerated by relativistic magnetic reconnection (without guide field) in collisionless electron-positron plasmas, for a wide range of upstream magnetizations σ and system sizes l. the particle spectra are well-represen... | the extent of power-law energy spectra in collisionless relativistic magnetic reconnection in pair plasmas |
primordial black hole (pbh) mergers have been proposed as an explanation for the gravitational wave events detected by the ligo collaboration. such pbhs may be formed in the early universe as a result of the collapse of extremely rare high-sigma peaks of primordial fluctuations on small scales, as long as the amplitude... | stochastic gravitational waves associated with the formation of primordial black holes |
einstein’s general theory of relativity (gr) successfully describes gravity. although gr has been accurately tested in weak gravitational fields, it remains largely untested in the general strong field cases. one of the most fundamental predictions of gr is the existence of black holes (bhs). after the recent direct de... | blackholecam: fundamental physics of the galactic center |
we report the discovery of an extended very-high-energy (vhe) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar psr j 0622 +3749 with the large high-altitude air shower observatory (lhaaso). the source is detected with a significance of 8.2 σ for e >25 tev assuming a gaussian template. the b... | extended very-high-energy gamma-ray emission surrounding psr j 0622 +3749 observed by lhaaso-km2a |
we search for stochastic gravitational wave background emitted from cosmic strings using the parkes pulsar timing array data over 15 years. while the common power-law excess revealed by several pulsar timing array experiments might be accounted for by the gravitational wave background from cosmic strings, the lack of t... | searching for cosmic string induced stochastic gravitational wave background with the parkes pulsar timing array |
extending our earlier work, a new family of three hartree-fock-bogoliubov (hfb) mass models, labeled hfb-30, hfb-31, and hfb-32, is presented, along with their underlying interactions, bsk30, bsk31, and bsk32, respectively. the principle new feature is a purely phenomenological pairing term that depends on the density ... | further explorations of skyrme-hartree-fock-bogoliubov mass formulas. xvi. inclusion of self-energy effects in pairing |
we investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. we study a scenario whereby the percolation temperature that signifies the completion of the transition, t_p, is as low as a few mev (nucleosynthesis ... | gravitational waves from a supercooled electroweak phase transition and their detection with pulsar timing arrays |
periodicities observed in two fast radio burst (frb) sources (16 days in frb 180916.j0158+65 and 160 days in frb 121102) are consistent with that of tight, stellar-mass binary systems. in the case of frb 180916.j0158+65 the primary is an early ob-type star with the mass-loss rate $\dot{m}\sim {10}^{-8}\mbox{--}{10}^{-7... | frb periodicity: mild pulsars in tight o/b-star binaries |
conventional approaches to probing axions and axion-like particles (alps) typically rely on a coupling to photons. however, if this coupling is extremely weak, alps become invisible and are effectively decoupled from the standard model. here we show that such invisible axions, which are viable candidates for dark matte... | audible axions |
aims: we present a new microscopic hadron-quark hybrid equation of state model for astrophysical applications, from which compact hybrid star configurations are constructed. these are composed of a quark core and a hadronic shell with a first-order phase transition at their interface. the resulting mass-radius relation... | a new quark-hadron hybrid equation of state for astrophysics. i. high-mass twin compact stars |
recent modeling of neutron star interior composition explorer observations of thermal x-ray pulsations from the surface of the isolated millisecond pulsar psr j0030+0451 suggests that the hot emitting regions on the pulsar’s surface are far from antipodal, which is at odds with the classical assumption that the magneti... | a nicer view of psr j0030+0451: evidence for a global-scale multipolar magnetic field |
over the past few decades, the measurement precision of some pulsar timing experiments has advanced from ∼10 μs to ∼10 ns, revealing many subtle phenomena. such high precision demands both careful data handling and sophisticated timing models to avoid systematic error. to achieve these goals, we present pint (pint is n... | pint: a modern software package for pulsar timing |
we present the pulse arrival times and high-precision dispersion measure estimates for 14 millisecond pulsars observed simultaneously in the 300 $-$ 500 mhz and 1260 $-$ 1460 mhz frequency bands using the upgraded giant metrewave radio telescope. the data spans over a baseline of 3.5 years (2018-2021), and is the first... | the indian pulsar timing array: first data release |
in this work, we have adopted gravitational decoupling by minimal geometric deformation (mgd) approach and have developed an anisotropic version of well-known tolman vii isotropic solution in the framework of f(r, t) gravity, where r is ricci scalar and t is trace of energy momentum tensor. the set of field equations h... | an anisotropic version of tolman vii solution in f(r, t) gravity via gravitational decoupling mgd approach |
we present a family of new exact solutions for relativistic anisotropic stellar objects by considering a four-dimensional spacetime embedded in a five-dimensional pseudo euclidean space, known as class i solutions. these solutions are well behaved in all respects, satisfy all energy conditions, and the resulting compac... | a family of well-behaved karmarkar spacetimes describing interior of relativistic stars |
the extremely high brightness temperatures of pulsars and fast radio bursts (frbs) require their radiation mechanisms to be coherent. coherent curvature radiation from bunches has been long discussed as the mechanism for radio pulsars and recently for frbs. assuming that bunches are already generated in pulsar magnetos... | bunching coherent curvature radiation in three-dimensional magnetic field geometry: application to pulsars and fast radio bursts |
with the upcoming commensal surveys for fast radio bursts (frbs), and their high candidate rate, usage of machine learning algorithms for candidate classification is a necessity. such algorithms will also play a pivotal role in sending real-time triggers for prompt follow-ups with other instruments. in this paper, we h... | fetch: a deep-learning based classifier for fast transient classification |
over 40 years of research suggests that the common envelope phase, in which an evolved star engulfs its companion upon expansion, is the critical evolutionary stage forming short-period, compact-object binary systems, such as coalescing double compact objects, x-ray binaries, and cataclysmic variables. in this work, we... | the complete evolution of a neutron-star binary through a common envelope phase using 1d hydrodynamic simulations |
mode and polarization-division multiplexing technologies (mdm and pdm) can offer considerable parallelism for optical multiplexing biosensors, complex optical neural networks, and high-capacity optical interconnects, while requiring only a single-wavelength laser source. thanks to the mature fabrication processes of si... | mode and polarization-division multiplexing based on silicon nitride loaded lithium niobate on insulator platform |
we investigated rastall gravity, for an anisotropic star with a static spherical symmetry, whereas the matter-geometry coupling as assumed in rastall theory (rt) is expected to play a crucial role differentiating rt from general relativity (gr). indeed, all the obtained results confirm that rt is not equivalent to gr, ... | non-trivial class of anisotropic compact stellar model in rastall gravity |
we present a comprehensive analysis of a supersymmetric $so(10)$ grand unified theory, which is broken to the standard model via the breaking of two intermediate symmetries. the spontaneous breaking of the first intermediate symmetry, $b-l$, leads to the generation of cosmic strings and right-handed neutrino masses and... | testing realistic $so(10)$ susy guts with proton decay and gravitational waves |
we answer frequently asked questions (faqs) about the hellings and downs correlation curve -- the "smoking-gun" signature that pulsar timing arrays (ptas) have detected gravitational waves (gws). many of these questions arise from inadvertently applying intuition about the effects of gws on ligo-like detectors to the c... | answers to frequently asked questions about the pulsar timing array hellings and downs curve |
we combine pulsar population synthesis with simulation-based inference to constrain the magneto-rotational properties of isolated galactic radio pulsars. we first develop a flexible framework to model neutron-star birth properties and evolution, focusing on their dynamical, rotational and magnetic characteristics. in p... | isolated pulsar population synthesis with simulation-based inference |
the standard model, extended with three right-handed (rh) neutrinos, is the simplest model that can explain light neutrino masses, the baryon asymmetry of the universe, and dark matter (dm). models in which rh neutrinos are light are generally easier to test in experiments. in this work, we show that, even if the rh ne... | pbh-infused seesaw origin of matter and unique gravitational waves |
motivated by the recent release of new results from five different pulsar timing array (pta) experiments claiming to have found compelling evidence for primordial gravitational waves (gw) at nano-hz frequencies, we study the consequences for two popular beyond the standard model (sm) frameworks, where such nano-hz gw c... | scale of dirac leptogenesis and left-right symmetry in the light of recent pta results |
we study the electrodynamics of a kinetically mixed dark photon cloud that forms through superradiance around a spinning black hole, and design strategies to search for the resulting multimessenger signals. a dark photon superradiance cloud sources a rotating dark electromagnetic field which, through kinetic mixing, in... | dark photon superradiance: electrodynamics and multimessenger signals |
this paper investigate the impacts of local density perturbations on the stability of self-gravitating compact objects by utilizing cracking technique within the context of f(r, t) gravity, where r and t represent the ricci scalar, and the trace of energy-momentum, respectively. to achieve this, we developed the hydros... | development of local density perturbation technique to identify cracking points in f(r, t) gravity |
the spontaneous breaking of u(1) b - l around the scale of grand unification can simultaneously account for hybrid inflation, leptogenesis, and neutralino dark matter, thus resolving three major puzzles of particle physics and cosmology in a single predictive framework. the b - l phase transition also results in a netw... | probing the scale of grand unification with gravitational waves |
the north american nanohertz observatory for gravitational waves (nanograv) recently reported evidence for the presence of a common stochastic signal across their array of pulsars. the origin of this signal is still unclear. one possibility is that it is due to a stochastic gravitational-wave background (sgwb) in the ∼... | massive black hole binary systems and the nanograv 12.5 yr results |
in the present article, we have constructed static anisotropic compact star models of einstein field equations for the spherical symmetric metric of embedding class one. by assuming the particular form of the metric function ν, we have solved the einstein field equations for anisotropic matter distribution. the anisotr... | modelling of anisotropic compact stars of embedding class one |
an axion rotating in field space can produce dark photons in the early universe via tachyonic instability. this explosive particle production creates a background of stochastic gravitational waves that may be visible at pulsar timing arrays or other gravitational wave detectors. this scenario provides a novel history f... | gravitational waves and dark photon dark matter from axion rotations |
we describe the model of surface emission from a rapidly rotating neutron star that is applied to neutron star interior composition explorer x-ray data of millisecond pulsars in order to statistically constrain the neutron star mass-radius relation and dense matter equation of state. to ensure that the associated calcu... | constraining the neutron star mass-radius relation and dense matter equation of state with nicer. ii. emission from hot spots on a rapidly rotating neutron star |
the quantum chromodynamics (qcd) axion may modify the cooling rates of neutron stars (nss). the axions are produced within the ns cores from nucleon bremsstrahlung and, when the nucleons are in superfluid states, cooper pair breaking and formation processes. we show that four of the nearby isolated magnificent seven ns... | upper limit on the qcd axion mass from isolated neutron star cooling |
collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. they are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ra... | the microphysics of collisionless shock waves |
we present a study of the spectral properties of 441 pulsars observed with the parkes radio telescope near the centre frequencies of 728, 1382 and 3100 mhz. the observations at 728 and 3100 mhz were conducted simultaneously using the dual-band 10-50 cm receiver. these high-sensitivity, multifrequency observations provi... | spectral properties of 441 radio pulsars |
the discovery of pulsars opened a new research field that allows studying a wide range of physics under extreme conditions. more than 3,000 pulsars are currently known, including especially more than 200 of them studied at gamma-ray frequencies. by putting recent insights into the pulsar magnetosphere in a historical c... | pulsar magnetospheres and their radiation |
gravitational waves offer a new window to probe the nature of gravity, including answering if the mediating particle, graviton, has a nonzero mass or not. pulsar timing arrays measure stochastic gravitational wave background (sgwb) at ∼1 - 100 nanohertz . recently, the north american nanohertz observatory for gravitati... | search for stochastic gravitational-wave background from massive gravity in the nanograv 12.5-year dataset |
we present several arguments which favor the scenario of two coexisting families of compact stars: hadronic stars and quark stars. besides the well-known hyperon puzzle of the physics of compact stars, a similar puzzle exists also when considering delta resonances. we show that these particles appear at densities close... | the scenario of two families of compact stars. part 1. equations of state, mass-radius relations and binary systems |
we perform magnetohydrodynamic simulations in full general relativity (grmhd) of quasi-circular, equal-mass, binary neutron stars that undergo merger. the initial stars are irrotational, n = 1 polytropes and are magnetized. we explore two types of magnetic-field geometries: one where each star is endowed with a dipole ... | binary neutron star mergers: a jet engine for short gamma-ray bursts |
we argue that comparison with observations of theoretical models for the velocity distribution of pulsars must be done directly with the observed quantities, that is parallax and the two components of proper motion. we have developed a formalism to do so, and applied it to pulsars with accurate vlbi measurements. for c... | the observed velocity distribution of young pulsars |
keck-telescope spectrophotometry of the companion of psr j1810+1744 shows a flat, but asymmetric light-curve maximum and a deep, narrow minimum. the maximum indicates strong gravity darkening (gd) near the l1 point, along with a heated pole and surface winds. the minimum indicates a low underlying temperature and subst... | psr j1810+1744: companion darkening and a precise high neutron star mass |
to understand the nature of supernovae and neutron star (ns) formation, as well as binary stellar evolution and their interactions, it is important to probe the distribution of ns masses. until now, all double ns (dns) systems have been measured as having a mass ratio close to unity (q ≥ 0.91). here, we report the meas... | pulsar j0453+1559: a double neutron star system with a large mass asymmetry |
high-mass x-ray binaries are fundamental in the study of stellar evolution, nucleosynthesis, structure and evolution of galaxies and accretion processes. hard x-rays observations by integral and swift have broadened significantly our understanding in particular for the super-giant systems in the milky way, whose number... | high-mass x-ray binaries in the milky way. a closer look with integral |
the recent theoretical advance known as the minimal geometric deformation (mgd) method has initiated renewed interest in investigating higher-curvature gravitational effects in relativistic astrophysics. in this work, we model a strange star within the context of einstein-gauss-bonnet gravity with the help of the mgd t... | gravitationally decoupled strange star model beyond the standard maximum mass limit in einstein-gauss-bonnet gravity |
we search for stochastic gravitational wave background (sgwb) generated by domain wall networks in the data release-2 of parkes pulsar timing array and find that the observed strong common power-law process can be explained by domain wall networks for the wall tension $\sigma_{\textrm{dw}}\sim (29-414~\textrm{tev})^3$ ... | domain wall network: a dual solution for gravitational waves and hubble tension? |
the repeating fast radio burst (frb) source, frb 20201124a, was found to be highly active in 2021 march and april. we observed the source with the effelsberg 100-m radio telescope at 1.36 ghz on 2021 april 9 and detected 20 bursts. a downward drift in frequency over time is clearly seen from the majority of bursts in o... | polarization properties of frb 20201124a from detections with the effelsberg 100-m radio telescope |
gravitational waves (gws) from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history. in the next decades, it is anticipated that we could obtain the multi-band gw standard siren data (from nanohertz to a few hundred hertz), which are expected to play an important role in co... | joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations |
we present high-precision timing observations spanning up to nine years for 37 millisecond pulsars monitored with the green bank and arecibo radio telescopes as part of the north american nanohertz observatory for gravitational waves (nanograv) project. we describe the observational and instrumental setups used to coll... | the nanograv nine-year data set: observations, arrival time measurements, and analysis of 37 millisecond pulsars |
we investigate the spectrum of gravitational waves arising from primordial inflation in the presence of a string-theoretical higher-curvature correction, specifically, the gauss-bonnet coupling term for the inflaton (modulus) field. we show that if the modulus field exhibits a wall-crossinglike behavior in the moduli s... | probing the inflationary moduli space with gravitational waves |
we present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (psr j0437-4715, psr j0711-6830, and psr j0737-3039a) and two young pulsars: the crab pulsar (j0534+2200) and the vela pulsar (j0835-4510). we use data from the third observing run of advanced ligo and virg... | gravitational-wave constraints on the equatorial ellipticity of millisecond pulsars |
pulsar timing arrays (pta) are a promising probe to the cosmologically novel nanohertz gravitational wave (gw) regime through the stochastic gw background. in this work, we consider subluminal gw modes as a possible source of correlations in a pta, utilizing the public code ptafast and the 12.5 years correlations data ... | constraining gravitational wave propagation using pulsar timing array correlations |
the nine-year h.e.s.s. galactic plane survey (hgps) has yielded the most uniform observation scan of the inner milky way in the tev gamma-ray band to date. the sky maps and source catalogue of the hgps allow for a systematic study of the population of tev pulsar wind nebulae found throughout the last decade. to investi... | the population of tev pulsar wind nebulae in the h.e.s.s. galactic plane survey |
we investigate the possibility of measuring the primordial gravitational wave (gw) signal across 21 decades in frequencies, using the cosmic microwave background (cmb), pulsar timing arrays (pta), and laser and atomic interferometers. for the cmb and pta experiments we consider the litebird mission and the square kilom... | measuring the spectrum of primordial gravitational waves with cmb, pta and laser interferometers |
we present an overview of future observational facilities that will significantly enhance our understanding of the fundamental nature of dark matter. these facilities span a range of observational techniques including optical/near-infrared imaging and spectroscopy, measurements of the cosmic microwave background, pulsa... | snowmass2021 cosmic frontier white paper: observational facilities to study dark matter |
the possibility that in the mass range around 10-12 m⊙ most of dark matter is constituted of primordial black holes (pbhs) is a very interesting topic. to produce pbhs with this mass, the primordial scalar power spectrum needs to be enhanced to the order of 0.01 at the scale k ∼1012 mpc-1. the enhanced power spectrum a... | primordial black holes and secondary gravitational waves from k and g inflation |
dark matter (dm) particles in the universe accumulate in neutron stars (nss) through their interactions with ordinary matter. it has been known that their annihilation inside the ns core causes late-time heating, with which the surface temperature becomes a constant value of ts ≃ (2 - 3) ×103 k for the ns age t ≳10 6 -... | dark matter heating vs. rotochemical heating in old neutron stars |
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