Pulsar Wind Research Articles

Modeling the Saddle-like GeV–TeV Spectrum of HESS J1809–193: Gamma Rays Arising from Reverse-shocked Pulsar Wind Nebula?

Abstract The evolution of pulsar wind nebulae (PWNe) could be expected to leave imprints in gamma rays. We suggest that the intriguing GeV–TeV spectral energy distribution (SED) of HESS J1809–193 and Fermi-LAT source J1810.3–1925e is very likely to be the gamma-ray signature of PWN J1809–193 in light of the scenario that the PWN was struck by the reverse shock of the parent supernova remnant. Based on the evolutionary theory of PWNe, we consider that, when the PWN was disrupted during a collision by the reverse shock, some VHE electrons escaped impulsively. The remaining electrons stayed in the relic PWN, which was displaced from the pulsar. The VHE part of the remaining electrons was depleted by the strong magnetic field that was enhanced by the reverse shock compression in the reverberation stage, leaving the other part of them generating GeV emission. The particles injected from the pulsar after the disruption enter the relic PWN through the newly formed tunnel called the cocoon. The gamma-ray emission from the escaped electrons can account for the TeV spectrum of component A of HESS J1809–193 or the TeV halo, while the electrons remaining after disruption can account for the GeV spectrum of J1810.3–1925e. Thus, the combination of contributions from these two populations of electrons naturally reproduces the saddle-like SED of HESS 1809–193 and J1810.3–1925e from 5 GeV to 30 TeV, together with the spectral hardening around 100 GeV. We also show that the post-disruption injection of electrons can explain the spectrum of the relatively faint gamma-ray emission of component B of HESS J1809–193.

PSR J1631–4722: The Discovery of a Young and Energetic Pulsar in the Supernova Remnant G336.7+0.5

Abstract Detecting a pulsar associated with a supernova remnant (SNR) and/or pulsar wind nebula (PWN) is crucial for unraveling its formation history and pulsar wind dynamics, yet the association with a radio pulsar is observed only in a small fraction of known SNRs and PWNe. In this paper, we report the discovery of a young pulsar J1631–4722, associated with the Galactic SNR G336.7+0.5 using Murriyang, CSIRO’s Parkes radio telescope. It is also potentially associated with a PWN revealed by the Rapid ASKAP (Australian Square Kilometre Array Pathfinder) Continuum Survey (RACS). This 118 ms pulsar has a high dispersion measure of ∼873 pc cm−3 and a rotation measure of –1004 rad m−2. Because of such a high DM, at frequencies below 2 GHz, the pulse profile is significantly scattered, making it effectively undetectable in previous pulsar surveys at ∼1.4 GHz. Follow-up observations yield a period derivative of Ṗ = 5.5× 10−14, implying a characteristic age, τc = 33.9 kyr, and spin-down luminosity, Ė = 1.3× 1036 erg s−1. PSR J1631–4722, with its high spin-down luminosity and potential link to a PWN, stands out as a promising source of the high-energy γ-ray emission observed in the region.

Anisotropic diffusion of high-energy cosmic rays in magnetohydrodynamic turbulence

The origin of cosmic rays (CRs) and how they propagate remain unclear. Studying the propagation of CRs in magnetohydrodynamic (MHD) turbulence can help to comprehend many open issues related to CR origin and the role of turbulent magnetic fields. To comprehend the phenomenon of slow diffusion in the near-source region, we study the interactions of CRs with the ambient turbulent magnetic field to reveal their universal laws. We numerically study the interactions of CRs with the ambient turbulent magnetic field, considering pulsar wind nebula as a general research case. Taking the magnetization parameter and turbulence spectral index as free parameters, together with radiative losses, we perform three group simulations to analyze the CR spectral, spatial distributions, and possible CR diffusion types. Our studies demonstrate that (1) CR energy density decays with both its effective radius and kinetic energy in the form of power-law distributions; (2) the morphology of the CR spatial distribution strongly depends on the properties of magnetic turbulence and the viewing angle; (3) CRs suffer a slow diffusion near the source and a fast or normal diffusion away from the source; (4) the existence of a power-law relationship between the averaged CR energy density and the magnetization parameter is independent of both CR energy and radiative losses; and (5) radiative losses can suppress CR anisotropic diffusion and soften the power-law distribution of CR energy density. The distribution law established between turbulent magnetic fields and CRs presents an intrinsic property, providing a convenient way to understand complex astrophysical processes related to turbulence cascades.

A multi-wavelength view of the isolated neutron star eRASSU J065715.3+260428

On the premise of a soft spectral distribution and absence of counterparts, the X-ray source was recently identified as a likely thermally emitting isolated neutron star (XINS) in a search in the All-Sky Survey. We investigated the nature and evolutionary state of the neutron star through a dedicated multi-wavelength follow-up observational campaign with and complemented by the analysis of archival LAT observations. The coherent timing analysis of the X-ray observations unveiled the rotation period of the XINS, P=261.085400(4),ms, and its spin-down rate P s,s^-1 (errors are $1σ$ confidence levels). The nearly sinusoidal pulse profile has a pulsed fraction of ∼15,% ($0.2-2$,keV). No optical counterparts are detected down to 27.3,mag ($5σ$, R band) in the FORS2 imaging, implying a large X-ray-to-optical flux ratio above 5200. The X-ray spectrum of the source is best described by a composite phenomenological model consisting of two thermal components, either a double blackbody continuum with temperatures 90,eV and 220,eV or a hydrogen neutron star atmosphere of temperature log(T/ K )∼ 5.8 combined with a hot blackbody of 250,eV, in both cases modified by an absorption feature at low energies, ∼0.3,keV with an equivalent width of ∼100,eV. The presence of faint non-thermal hard X-ray tails is ruled out above $(2.1±1.8)$,% of the source unabsorbed flux. Radio searches at $1-1.5$,GHz with yielded negative results, with a deep upper limit on the pulsed flux of 1.4,μJy ($10σ$). Similarly, no significant spatial or pulsed signals were detected in sixteen years of LAT observations. The most likely interpretation is that the source is a middle-aged spin-powered pulsar, which can also be identified as The absence of non-thermal X-ray, radio, or gamma-ray emission within current limits suggests either an unfavourable viewing geometry or unusual magnetospheric properties. Additional observations are needed to check for faint hard X-ray tails, investigate the presence of diffuse emission from a pulsar-wind nebula, and obtain a more accurately sampled timing solution.

4FGL J1544.2−2554: A new spider pulsar candidate

Context. Spider pulsars are millisecond pulsars in tight binary systems in which a low-mass companion star is heated and ablated by the pulsar wind. Observations of these objects allow one to study stellar evolution with the formation of millisecond pulsars and the physics of superdense matter in neutron stars. However, spiders are rare due to difficulties related to their discovery when using typical radio search techniques. The Fermiγ-ray source 4FGL J1544.2−2554 was recently proposed as a pulsar candidate, and its likely X-ray and optical counterparts, with the galactic coordinates l ≈ 344.​​°76, b ≈ 22.​​°59 and the magnitude G ≈ 20.6, were found using the eROSITA and Gaia surveys. Aims. Our goals are to study whether the source is a new spider pulsar and to estimate its fundamental parameters. Methods. We performed the first optical time series multi-band photometry of the object. We used the Lomb-Scargle periodogram to search for its brightness periodicity and fitted its light curves with a model of direct heating of the binary companion by the pulsar wind. Results. The source shows a strong brightness variability with a period of ≈2.724 h and an amplitude of ≳2.5 mag, and its light curves have a single broad peak per period. These features are typical for spider pulsars. The curves are well fitted by the direct heating model, resulting in an orbit inclination of the presumed spider system of ≈83°, a companion mass of ≈0.1 M⊙, ‘day-side’ and ‘night-side’ temperatures of ≈7200 K and ≈3000 K, a Roche lobe filling factor of ≈0.65, and a distance of ≈2.1 kpc. Conclusions. Our findings suggest that 4FGL J1544.2−2554 is a spider pulsar. This result encourages the search for pulsar millisecond pulsations in radio and γ-rays to confirm its nature.

Ultra-high-energy γ-ray emission associated with the tail of a bow-shock pulsar wind nebula

Ultra-high-energy γ-ray emission associated with the tail of a bow-shock pulsar wind nebula

A deep study confirms diffuse nonthermal X-ray emission from the globular cluster Terzan 5

Diffuse X-ray emission has been detected from a few Galactic globular clusters (GCs), but its nature remains largely unclear. The GC Terzan 5 was previously found to show a significant diffuse thermal X-ray excess from its field, likely contributed by the Galactic background, and a nonthermal component described by a power-law model with photon index $ With over 16 times the accumulated exposure time compared to a prior study, we reexamined and verified the diffuse X-ray emission from the field of which enabled us to place constraints on its nature. We analyzed all available useful observations of including 18 observations over a span of 13 years, with a total exposure time of 641.6 ks. To study the diffuse X-ray emission, we focused on four annular regions with an equal width of 0.72 arcmin centered on (0.72--3.60 arcmin), from which we extracted and analyzed the X-ray spectra after removing point sources and instrumental backgrounds. We confirm a significant diffuse X-ray excess from the field of in the band 0.8--3 keV. After constraining the contribution from the local X-ray background, we find a diffuse X-ray component that is genuinely associated with and can be well described by a power-law model. More interestingly, the fitted photon indices show a significant increase from $ 0.18$ in the inner region to $ 0.71$ in the outer region. The diffuse X-rays are also well fit by a thermal bremsstrahlung model, with plasma temperatures declining from $kT 3$ keV to $kT 1$ keV. We suggest that synchrotron radiation from the combined pulsar winds of millisecond pulsar population is a possible origin of the observed diffuse X-ray emission but that the sharp steepening in the spectra cannot be produced solely by synchrotron cooling. Other radiation processes, like thermal bremsstrahlung, may also contribute to the diffuse X-rays.

Turbulent Transport Characteristics of the Particles within Pulsar Wind Nebulae 3C58 and G54.1+0.3

Turbulent transport characteristics of the particles within two Crab-like pulsar wind nebulae (PWNe), 3C58 and G54.1+0.3, are investigated in the framework of a time-dependent turbulent diffusion model. The model takes the gyroresonant interactions between the particles and turbulent waves into account, which enables us to self-consistently determine the energy and spatial coefficients of particles within the nebula via the distributions of turbulent waves. Our application of the model to the multiband emission from 3C58 and G54.1+0.3 reveals the following. (1) The energy and spatial diffusion coefficients seem to follow quasi-linear distributions in the Kolmogorov-type turbulence, but consistent with nonlinear distributions at low energies in the Kraichnan-type turbulence due to the effects of the turbulent scattering. (2) The stochastic acceleration and spatial diffusion processes may play a role in modifying the electron spectrum in the Kolmogorov-type turbulence, whereas in the Kraichnan-type turbulence the energy exchange between the turbulent waves and particles is more efficient, resulting in more significant effects of the stochastic acceleration and spatial diffusion processes on the electron spectrum at the low energies of E e ≲ 1 TeV. (3) At the high energies of E e ≳ 1 TeV, the diffusion transport appears to be less effective for the evolution of the particles within 3C58 and G54.1+0.3 because the synchrotron radiative cooling process dominates over the particle transport. These two Crab-like PWNe are expected to be electron PeVatrons in the Galaxy, with a common slow diffusion escape occurring in both 3C58 and G54.1+0.3.

Investigation of the Nonthermal X-Ray Emission from the Supernova Remnant CTB 37B Hosting the Magnetar CXOU J171405.7-381031

We present a detailed X-ray investigation of a region (S1) exhibiting nonthermal X-ray emission within the supernova remnant (SNR) CTB 37B hosting the magnetar CXOU J171405.7−381031. Previous analyses modeled this emission with a power law (PL), inferring various values for the photon index (Γ) and absorbing column density (N H). Based on these, S1 was suggested to be an SNR shell, a background pulsar wind nebula, or an interaction region between the SNR and a molecular cloud. Our analysis of a larger data set favors a steepening (broken or curved PL) spectrum over a straight PL, with the best-fit broken power-law (BPL) parameters of Γ = 1.23 ± 0.23 and 2.24 ± 0.16 below and above a break at 5.57 ± 0.52 keV, respectively. However, a simple PL or srcut model cannot be definitively ruled out. For the BPL model, the inferred N H = (4.08 ± 0.72) × 1022 cm−2 towards S1 is consistent with that of the SNR, suggesting a physical association. The BPL-inferred spectral break ΔΓ ≈ 1 and hard Γ can be naturally explained by a nonthermal bremsstrahlung (NTB) model. We present an evolutionary NTB model that reproduces the observed spectrum, which indicates the presence of subrelativistic electrons within S1. However, alternate explanations for S1, an unrelated PWN or the SNR shock with unusually efficient acceleration, cannot be ruled out. We discuss these explanations and their implications for gamma-ray emission from CTB 37B and describe future observations that could settle the origin of S1.

Material mixing in pulsar wind nebulae of massive runaway stars

Abstract In this study we quantitatively examine the manner pulsar wind, supernova ejecta and defunct stellar wind materials distribute and melt together into plerions. We performed 2.5D MHD simulations of the entire evolution of their stellar surroundings and different scenarios are explored, whether the star dies as a red supergiant and Wolf-Rayet supernova progenitors, and whether it moved with velocity $20\, \rm km\, \rm s^{-1}$ or $40\, \rm km\, \rm s^{-1}$ through the ISM. Within the post-explosion, early $10\, \rm kyr$, the H-burning-products rich red supergiant wind only mixes by $\le 20~{{\%}}$, due to its dense circumstellar medium filling the progenitor’s bow shock trail, still unaffected by the supernova blastwave. Wolf-Rayet materials, enhanced in C, N, O elements, distribute circularly for the $35\, \rm M_\odot$ star moving at $20\, \rm km\, \rm s^{-1}$ and oblongly at higher velocities, mixing efficiently up to 80%. Supernova ejecta, filled with Mg, Si, Ca, Ti and Fe, remain spherical for longer times at $20\, \rm km\, \rm s^{-1}$ but form complex patterns at higher progenitor speeds due to earlier interaction with the bow shock, in which they mix more efficiently. The pulsar wind mixing is more efficient for Wolf-Rayet (25%) than red supergiant progenitors (20%). This work reveals that the past evolution of massive stars and their circumstellar environments critically shapes the internal distribution of chemical elements on plerionic supernova remnants, and, therefore, governs the origin of the various emission mechanisms at work therein. This is essential for interpreting multi-frequency observations of atomic and molecular spectral lines, such as in optical, infrared, and soft X-rays.

Tleco: A Toolkit for Modeling Radiative Signatures from Relativistic Outflows

A wide range of astrophysical sources exhibit extreme and rapidly varying electromagnetic emission indicative of efficient nonthermal particle acceleration. Understanding these sources often involves comparing data with a broad range of theoretical scenarios. To this end, it is beneficial to have tools that enable not only fast and efficient parametric investigation of the predictions of a specific scenario but also the flexibility to explore different theoretical ideas. In this paper, we introduce Tleco, a versatile and lightweight toolkit for developing numerical models of relativistic outflows, including their particle acceleration mechanisms and resultant electromagnetic signature. Built on the Rust programming language and wrapped into a Python library, Tleco offers efficient algorithms for evolving relativistic particle distributions and for solving the resulting emissions in a customizable fashion. Tleco uses a fully implicit discretization algorithm to solve the Fokker–Planck equation with user-defined diffusion, advection, cooling, injection, and escape and offers prescriptions for radiative emission and cooling. These include, but are not limited to, synchrotron, inverse-Compton, and self-synchrotron absorption. Tleco is designed to be user friendly and adaptable to model particle acceleration and the resulting electromagnetic spectrum and temporal variability in a wide variety of astrophysical scenarios, including, but not limited to, gamma-ray bursts, pulsar wind nebulae, and jets from active galactic nuclei. In this work, we outline the core algorithms and proceed to evaluate and demonstrate their effectiveness. The code is open source and available in the GitHub repository: https://github.com/zkdavis/Tleco.

Modeling the X-Ray Emission of the Boomerang Nebula and Implication for Its Potential Ultrahigh-energy Gamma-Ray Emission

The Boomerang Nebula is a bright radio and X-ray pulsar wind nebula (PWN) powered by an energetic pulsar, PSR J2229+6114. It is spatially coincident with one of the brightest ultrahigh-energy (UHE; ≥100 TeV) gamma-ray sources, LHAASO J2226+6057. While X-ray observations have provided radial profiles for both the intensity and photon index of the nebula, previous theoretical studies have not reached an agreement on their physical interpretation, which also leads to different anticipation of the UHE emission from the nebula. In this work, we model its X-ray emission with a dynamical evolution model of PWN, considering both convective and diffusive transport of electrons. On the premise of fitting the X-ray intensity and photon index profiles, we find that the magnetic field within the Boomerang Nebula is weak (∼10 μG in the core region and diminishing to 1 μG at the periphery), which therefore implies a significant contribution to the UHE gamma-ray emission by the inverse Compton (IC) radiation of injected electron/positron pairs. Depending on the particle transport mechanism, the UHE gamma-ray flux contributed by the Boomerang Nebula via the IC radiation may constitute about 10%–50% of the flux of LHAASO J2226+6057 at 100 TeV and up to 30% at 500 TeV. Finally, we compare our results with previous studies and discuss potential hadronic UHE emission from the PWN. In our modeling, most of the spindown luminosity of the pulsar may be transformed into thermal particles or relativistic protons.

X-ray Investigation of the Supernova Remnant Candidate G278.0+12.4 and Prospect of Future Missions

In this work, we analyze the X-ray data of supernova remnant (SNR) candidate G278.0+12.4. We examine its nature and the X-ray properties such as electron temperature kTe and abundances, using Suzaku data. We found that the X-ray emission is well represented by two-component model: an unabsorbed thermal plasma with about 5 keV and non-thermal components with a photon index 0.5-1. Our spectral analysis confirm that the G278.0+12.4 is likely to be an SNR. We found non-thermal X-ray emission from the spectra, which indicates that a Pulsar Wind Nebula scenario is possible for G278.0+12.4. In order to make predictions for future missions, we perform XRISM and Athena simulations. We present our results on the nature of G278.0+12.4.

Parkes Radio and NuSTAR X-Ray Observations of the Composite Supernova Remnant B0453–685 in the Large Magellanic Cloud

Gamma-ray emission is observed coincident in position to the evolved, composite supernova remnant (SNR) B0453–685. Prior multiwavelength investigations of the region indicate that the pulsar wind nebula (PWN) within the SNR is the most likely origin for the observed gamma rays, with a possible pulsar contribution that becomes significant at energies below E ∼ 5 GeV. Constraints on the PWN hard X-ray spectrum are important for the most accurate broadband representation of PWN emission and determining the presence of a gamma-ray pulsar component. The results of Parkes radio and Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray observations are presented on PWN B0453–685. We perform a search for the central pulsar in the new Parkes radio data, finding an upper limit of 12 μJy. A pulsation search in the new NuSTAR observations additionally provides a 3σ upper limit on the hard X-ray pulsed fraction of 56%. The PWN is best characterized with a photon index ΓX = 1.91 ± 0.20 in the 3–78 keV NuSTAR data, and the results are incorporated into existing broadband models. Last, we characterize a serendipitous source detected by Chandra and NuSTAR that is considered a new high-mass X-ray binary candidate.

Analysis of the possible detection of the pulsar wind nebulae of PSR J1208-6238, J1341-6220, J1838-0537, and J1844-0346

Context. Pulsar wind nebulae (PWNe) are a source of very high energy radiation that can reach up to tera-electron volts and even peta-electron volts. Our work uses the pulsar tree, a graph theory tool recently presented to analyze the pulsar population and select candidates of interest. Aims. We aim to discover detectable PWNe. We also aim to test to what extent the pulsar tree is able to group detectable PWNe despite only considering the intrinsic properties of pulsars. Methods. We selected four pulsars as tera-electron volt PWNe candidates based on their positions in the pulsar tree. Using observed and assumed ranges of values for relevant parameters, we anticipated the possible spectral energy distributions of the PWNe of four pulsars (PSR J1208-6238, J1341-6220, J1838-0537, and J1844-0346) via a detailed time-dependent leptonic model that was already found to be appropriate for describing almost all other detected nebulae. Results. We estimated the likelihood of detection for the four candidates we studied by comparing the TeV fluxes predicted by the possible models with the sensitivities of different observatories. In doing so, we provide context for analyzing the advantages and caveats of using the pulsar tree position as a marker for properties that go beyond the intrinsic features of pulsars that are considered in producing the pulsar tree.

A Catalog of Pulsar X-Ray Filaments

Abstract We present the first Chandra X-ray Observatory (CXO) catalog of “pulsar X-ray filaments,” or “misaligned outflows.” These are linear, synchrotron-radiating features powered by ultrarelativistic electrons and positrons that escape from bow shock pulsars. The filaments are misaligned with the (large) pulsar velocity, distinguishing them from the pulsar wind nebula (PWN) trail, which is also often visible in CXO ACIS images. Spectral fits and morphological properties are extracted for five secure filaments and three candidates using a uniform method. We present a search of archival CXO data for linear diffuse features; the known examples are recovered and a few additional weak candidates are identified. We also report on a snapshot CXO ACIS survey of pulsars with properties similar to the filament producers, finding no new filaments but some diffuse emission, including one PWN trail. Finally, we provide an updated model for the pulsar properties required to create filaments in light of these new observations.

Analysis of the Emission and Morphology of the Pulsar Wind Nebula Candidate HAWC J2031+415

The first TeV γ-ray source with no lower energy counterparts, TeV J2032+4130, was discovered by HEGRA. It appears in the third HAWC catalog as 3HWC J2031+415 and it is a bright TeV γ-ray source whose emission has previously been resolved as two sources: HAWC J2031+415 and HAWC J2030+409. While HAWC J2030+409 has since been associated with the Fermi Large Area Telescope Cygnus Cocoon, no such association for HAWC J2031+415 has yet been found. In this work, we investigate the spectrum and energy-dependent morphology of HAWC J2031+415. We associate HAWC J2031+415 with a γ-ray binary system containing the pulsar PSR J2032+4127 and its companion MT91 213. We study HAWC data to observe their periastron in 2017. Additionally, we perform a combined multiwavelength analysis using radio, X-ray, and γ-ray emission. We conclude that HAWC J2031+415 and, by extension, TeV J2032+4130 are most probably a pulsar wind nebula powered by PSR J2032+4127.

Testing the molecular cloud paradigm for ultra-high-energy gamma ray emission from the direction of SNR G106.3+2.7

Context. Supernova remnants (SNRs) are believed to be capable of accelerating cosmic rays (CRs) to PeV energies. SNR G106.3+2.7 is a prime PeVatron candidate. It is formed by a head region, where the pulsar J2229+6114 and its boomerang-shaped pulsar wind nebula are located, and a tail region containing SN ejecta. The lack of observed gamma ray emission from the two regions of this SNR has made it difficult to assess which region would be responsible for the PeV CRs. Aims. We aim to characterize the very-high-energy (VHE, 0.1–100 TeV) gamma ray emission from SNR G106.3+2.7 by determining the morphology and spectral energy distribution of the region. This is accomplished using 2565 days of data and improved reconstruction algorithms from the High Altitude Water Cherenkov (HAWC) Observatory. We also explore possible gamma ray production mechanisms for different energy ranges. Methods. Using a multi-source fitting procedure based on a maximum-likelihood estimation method, we evaluate the complex nature of this region. We determine the morphology, spectrum, and energy range for the source found in the region. Molecular cloud information is also used to create a template and evaluate the HAWC gamma ray spectral properties at ultra-high-energies (UHE, > 56 TeV). This will help probe the hadronic nature of the highest-energy emission from the region. Results. We resolve one extended source coincident with all other gamma ray observations of the region. The emission reaches above 100 TeV and its preferred log-parabola shape in the spectrum shows a flux peak in the TeV range. The molecular cloud template fit on the higher energy data reveals that the SNR’s energy budget is fully capable of producing a purely hadronic source for UHE gamma rays. Conclusions. The HAWC observatory resolves one extended source between the head and the tail of SNR G106.3+2.7 in the VHE gamma ray regime. The template fit suggests the highest energy gamma rays could come from a hadronic origin. However, the leptonic scenario, or a combination of the two, cannot be excluded at this time.

Pulsar-wind nebulae meeting the circumstellar media of their progenitors

A significative fraction of high-mass stars sail away through the interstellar medium of the galaxies. Once they evolved and died via a core-collapse supernova, a magnetised, rotating neutron star (a pulsar) is usually left over. The immediate surroundings of the pulsar is the pulsar wind, which forms a nebula whose morphology is shaped by the supernova ejecta and channelled into the circumstellar medium of the progenitor star in the pre-supernova time. Irregular pulsar-wind nebulae display a large variety of radio appearances, screened by their interacting supernova blast wave, or harbour asymmetric up–down emission. Here, we present a series of 2.5-dimensional (2 dimensions for the scalar quantities plus a toroidal component for the vectors) black non-relativistic magneto-hydrodynamical simulations exploring the evolution of the pulsar-wind nebulae generated by a red supergiant and a Wolf-Rayet massive supernova progenitor, moving with Mach number $M=1$ and $M=2$ into the warm phase of the Galactic plane. black In such a simplified approach, the progenitor's direction of motion, the local ambient medium magnetic field, and the progenitor and pulsar axis of rotation, are all aligned; this restricted our study to peculiar pulsar-wind nebula of high-equatorial-energy flux. We find that the reverberation of the termination shock of the pulsar-wind nebulae, when sufficiently embedded into its dead stellar surroundings and interacting with the supernova ejecta, is asymmetric and differs greatly as a function of the past circumstellar evolution of its progenitor, which reflects into their projected radio synchrotron emission. This mechanism is particularly at work in the context of remnants involving slowly moving or very massive stars. We find that the mixing of material in plerionic core-collapse supernova remnants is strongly affected by the asymmetric reverberation in their pulsar-wind nebulae.

X-ray and optical observations of the millisecond pulsar binary PSR J1431–4715

We present the first X-ray observation of the energetic millisecond pulsar binary PSR J1431−4715, performed with XMM-Newton and complemented with fast optical multi-band photometry acquired with the ULTRACAM instrument at ESO-NTT. It is found as a faint X-ray source without a significant orbital modulation. This contrasts with the majority of systems that instead display substantial X-ray orbital variability. The X-ray spectrum is dominated by non-thermal emission and, due to the lack of orbital modulation, does not favour an origin in an intrabinary shock between the pulsar and companion star wind. While thermal emission from the neutron star polar cap cannot be excluded in the soft X-rays, the dominance of synchrotron emission favours an origin in the pulsar magnetosphere that we describe at both X-ray and gamma-ray energies with a synchro-curvature model. The optical multi-colour light curve folded at the 10.8 h orbital period is double-humped and dominated by ellipsoidal effects, but also affected by irradiation. The ULTRACAM light curves are fit with several models encompassing direct heating and a cold spot, or heat redistribution after irradiation either through convection or convection plus diffusion. Despite the inability to constrain the best irradiation models, the fits provide consistent system parameters, giving an orbital inclination of 59 ± 6° and a distance of 3.1 ± 0.3 kpc. The companion is found to be an F-type star, underfilling its Roche lobe (fRL = 73 ± 4%) with a mass of 0.20 ± 0.04 M⊙, confirming the redback status, but hotter than the majority of redbacks. The stellar dayside and nightside temperatures of 7500 K and 7400 K, respectively, indicate a weak irradiation effect on the companion, likely due to its high intrinsic luminosity. Although the pulsar mass cannot be precisely derived, a heavy (1.8−2.2 M⊙) neutron star is favoured.