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Sample records for emitting pulsar wind

  1. VHE gamma-ray Emitting Pulsar Wind Nebulae Discovered by H.E.S.S.

    SciTech Connect

    Gallant, Y.A.; Carrigan, S.; Djannati-Atai, A.; Funk, S.; Hinton, J.A.; Hoppe, S.; de Jager, O.C.; Khelifi, B.; Komin, Nu.; Kosack, K.; Lemiere, A. Masterson, C.; /Dublin Inst.

    2008-06-05

    Recent advances in very-high-energy (VHE) gamma-ray astronomy have opened a new observational window on the physics of pulsars. The high sensitivity of current imaging atmospheric Cherenkov telescopes, and in particular of the H.E.S.S. array, has already led to the discovery of about a dozen VHE-emitting pulsar wind nebulae (PWNe) and PWN candidates. These include the plerions in the composite supernova remnants MSH 15-52, G21.5-0.9, Kes 75, and Vela, two sources in the Kookaburra, and the nebula of PSR B1823-13. This VHE emission is generally interpreted as inverse Compton emission from the relativistic electrons and positrons accelerated by the pulsar and its wind; as such, it can yield a more direct spatial and spectral view of the accelerated particles than can be inferred from observations of their synchrotron emission. The VHE-emitting PWNe detected by the H.E.S.S. telescopes are reviewed and the implications for pulsar physics discussed.

  2. X-RAY INVESTIGATION OF THE DIFFUSE EMISSION AROUND PLAUSIBLE {gamma}-RAY EMITTING PULSAR WIND NEBULAE IN KOOKABURRA REGION

    SciTech Connect

    Kishishita, Tetsuichi; Bamba, Aya; Uchiyama, Yasunobu

    2012-05-10

    We report on the results from Suzaku X-ray observations of the radio complex region called Kookaburra, which includes two adjacent TeV {gamma}-ray sources HESS J1418-609 and HESS J1420-607. The Suzaku observation revealed X-ray diffuse emission around a middle-aged pulsar PSR J1420-6048 and a plausible pulsar wind nebula (PWN) Rabbit with elongated sizes of {sigma}{sub X} = 1.'66 and {sigma}{sub X} = 1.'49, respectively. The peaks of the diffuse X-ray emission are located within the {gamma}-ray excess maps obtained by H.E.S.S. and the offsets from the {gamma}-ray peaks are 2.'8 for PSR J1420-6048 and 4.'5 for Rabbit. The X-ray spectra of the two sources were well reproduced by absorbed power-law models with {Gamma} = 1.7-2.3. The spectral shapes tend to become softer according to the distance from the X-ray peaks. Assuming the one-zone electron emission model as the first-order approximation, the ambient magnetic field strengths of HESS J1420-607 and HESS J1418-609 can be estimated as 3 {mu}G and 2.5 {mu}G, respectively. The X-ray spectral and spatial properties strongly support that both TeV sources are PWNe, in which electrons and positrons accelerated at termination shocks of the pulsar winds are losing their energies via the synchrotron radiation and inverse Compton scattering as they are transported outward.

  3. X-Ray Investigation of the Diffuse Emission around Plausible γ-Ray Emitting Pulsar Wind Nebulae in Kookaburra Region

    NASA Astrophysics Data System (ADS)

    Kishishita, Tetsuichi; Bamba, Aya; Uchiyama, Yasunobu; Tanaka, Yasuyuki; Takahashi, Tadayuki

    2012-05-01

    We report on the results from Suzaku X-ray observations of the radio complex region called Kookaburra, which includes two adjacent TeV γ-ray sources HESS J1418-609 and HESS J1420-607. The Suzaku observation revealed X-ray diffuse emission around a middle-aged pulsar PSR J1420-6048 and a plausible pulsar wind nebula (PWN) Rabbit with elongated sizes of σX = 1farcm66 and σX = 1farcm49, respectively. The peaks of the diffuse X-ray emission are located within the γ-ray excess maps obtained by H.E.S.S. and the offsets from the γ-ray peaks are 2farcm8 for PSR J1420-6048 and 4farcm5 for Rabbit. The X-ray spectra of the two sources were well reproduced by absorbed power-law models with Γ = 1.7-2.3. The spectral shapes tend to become softer according to the distance from the X-ray peaks. Assuming the one-zone electron emission model as the first-order approximation, the ambient magnetic field strengths of HESS J1420-607 and HESS J1418-609 can be estimated as 3 μG and 2.5 μG, respectively. The X-ray spectral and spatial properties strongly support that both TeV sources are PWNe, in which electrons and positrons accelerated at termination shocks of the pulsar winds are losing their energies via the synchrotron radiation and inverse Compton scattering as they are transported outward.

  4. Pulsar Magnetohydrodynamic Winds

    NASA Astrophysics Data System (ADS)

    Okamoto, Isao; Sigalo, Friday B.

    2006-12-01

    The acceleration and collimation/decollimation of relativistic magnetocentrifugal winds are discussed concerning a cold plasma from a strongly magnetized, rapidly rotating neutron star in a steady axisymmetric state based on ideal magnetohydrodynamics. There exist unipolar inductors associated with the field line angular frequency, α, at the magnetospheric base surface, SB, with a huge potential difference between the poles and the equator, which drive electric current through the pulsar magnetosphere. Any ``current line'' must emanate from one terminal of the unipolar inductor and return to the other, converting the Poynting flux to the kinetic flux of the wind at finite distances. In a plausible field structure satisfying the transfield force-balance equation, the fast surface, SF, must exist somewhere between the subasymptotic and asymptotic domains, i.e., at the innermost point along each field line of the asymptotic domain of \\varpaA2/\\varpi2 ≪ 1, where \\varpiA is the Alfvénic axial distance. The criticality condition at SF yields the Lorentz factor, γF = μ\\varepsilon1/3, and the angular momentum flux, β, as the eigenvalues in terms of the field line angular velocity, α, the mass flux per unit flux tube, η, and one of the Bernoulli integrals, μδ, which are assumed to be specifiable as the boundary conditions at SB. The other Bernoulli integral, μɛ, is related to μδ as μɛ = μδ[1-(α2\\varpiA2/c2)]-1, and both μɛ and \\varpiA2 are eigenvalues to be determined by the criticality condition at SF. Ongoing MHD acceleration is possible in the superfast domain. This fact may be helpful in resolving a discrepancy between the wind theory and the Crab-nebula model. It is argued that the ``anti-collimation theorem'' holds for relativistic winds, based on the curvature of field streamlines determined by the transfield force balance. The ``theorem'' combines with the ``current-closure condition'' as a global condition in the wind zone to produce a

  5. Pulsar braking: magnetodipole vs. wind

    NASA Astrophysics Data System (ADS)

    Tong, Hao

    2016-01-01

    Pulsars are good clocks in the universe. One fundamental question is that why they are good clocks? This is related to the braking mechanism of pulsars. Nowadays pulsar timing is done with unprecedented accuracy. More pulsars have braking indices measured. The period derivative of intermittent pulsars and magnetars can vary by a factor of several. However, during pulsar studies, the magnetic dipole braking in vacuum is still often assumed. It is shown that the fundamental assumption of magnetic dipole braking (vacuum condition) does not exist and it is not consistent with the observations. The physical torque must consider the presence of the pulsar magnetosphere. Among various efforts, the wind braking model can explain many observations of pulsars and magnetars in a unified way. It is also consistent with the up-to-date observations. It is time for a paradigm shift in pulsar studies: from magnetic dipole braking to wind braking. As one alternative to the magnetospheric model, the fallback disk model is also discussed.

  6. Acceleration by pulsar winds in binary systems

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Gaisser, T. K.

    1990-01-01

    In the absence of accretion torques, a pulsar in a binary system will spin down due to electromagnetic dipole radiation and the spin-down power will drive a wind of relativistic electron-positron pairs. Winds from pulsars with short periods will prevent any subsequent accretion but may be confined by the companion star atmosphere, wind, or magnetosphere to form a standing shock. The authors investigate the possibility of particle acceleration at such a pulsar wind shock and the production of very high energy (VHE) and ultra high energy (UHE) gamma rays from interactions of accelerated protons in the companion star's wind or atmosphere. They find that in close binaries containing active pulsars, protons will be shock accelerated to a maximum energy dependent on the pulsar spin-down luminosity. If a significant fraction of the spin-down power goes into particle acceleration, these systems should be sources of VHE and possibly UHE gamma rays. The authors discuss the application of the pulsar wind model to binary sources such as Cygnus X-3, as well as the possibility of observing VHE gamma-rays from known binary radio pulsar systems.

  7. Acceleration by pulsar winds in binary systems

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Gaisser, T. K.

    1990-01-01

    In the absence of accretion torques, a pulsar in a binary system will spin down due to electromagnetic dipole radiation, and the spin-down power will drive a wind of relativistic electron-position pairs. Winds from pulsars with short periods will prevent any subsequent accretion but may be confined by the companion star atmosphere, wind, or magnetosphere to form a standing shock. This paper investigates the possibility of particle acceleration at such a pulsar wind shock and the production of VHE and UHE gamma-rays from interactions of accelerated protons in the companion star's wind or atmosphere. It is found that, in close binaries containing active pulsars, protons will be shock accelerated to a maximum energy dependent on the pulsar spin-down luminosity. If a significant fraction of the spin-down power goes into particle acceleration, these systems should be sources of VHE and possibly UHE gamma-rays. The application of the pulsar wind model to binary sources such as Cygnus X-3 is discussed, as well as the possibility of observing VHE gamma-rays from known binary radio pulsar systems.

  8. Shedding Light on the Pulsar Wind

    NASA Astrophysics Data System (ADS)

    Khangulyan, Dmitry; Aharonian, Felix; Bogovalov, Sergey V.

    2012-07-01

    Pulsars are believed to eject ultrarelativistic electron-positron winds that propagate to the large distances leading to the formation of the extended non-thermal sources known as plerions. The wind has been proposed to originate close to the light cylinder, and carry the rotational energy losses of the pulsar. At the beginning the wind is dominated by electromagnetic energy (Poynting flux), but at some later stage the wind is accelerated with most of the Poynting flux being converted to the kinetic energy of bulk motion. Such winds have not been yet observed, therefore the proposed scenario has been deemed inconclusive. The `cold' winds (in the sense of the low energy of the electrons in the frame of moving plasma) represent a form of "dark substance" since, despite the very high energy of the wind particles, the wind emission is extremely weak. In fact, the pulsar winds are visible only in inverse Compton gamma-rays. Recent observations in high energy (HE) and very high energy (VHE) domains with Fermi Large Area Telescope (Fermi/LAT) and ground based Cherenkov detectors Magic and Veritas allow the key properties of the pulsar winds to be measured in a few important systems.

  9. Gamma rays from pulsar wind shock acceleration

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    1990-01-01

    A shock forming in the wind of relativistic electron-positron pairs from a pulsar, as a result of confinement by surrounding material, could convert part of the pulsar spin-down luminosity to high energy particles through first order Fermi acceleration. High energy protons could be produced by this mechanism both in supernova remnants and in binary systems containing pulsars. The pion-decay gamma-rays resulting from interaction of accelerated protons with surrounding target material in such sources might be observable above 70 MeV with EGRET (Energetic Gamma-Ray Experimental Telescope) and above 100 GeV with ground-based detectors. Acceleration of protons and expected gamma-ray fluxes from SN1987A, Cyg X-3 type sources and binary pulsars are discussed.

  10. GAMMA-RAY SIGNAL FROM THE PULSAR WIND IN THE BINARY PULSAR SYSTEM PSR B1259-63/LS 2883

    SciTech Connect

    Khangulyan, Dmitry; Bogovalov, Sergey V.; Ribo, Marc E-mail: felix.aharonian@dias.ie E-mail: mribo@am.ub.es

    2011-12-01

    Binary pulsar systems emit potentially detectable components of gamma-ray emission due to Comptonization of the optical radiation of the companion star by relativistic electrons of the pulsar wind, both before and after termination of the wind. The recent optical observations of binary pulsar system PSR B1259-63/LS 2883 revealed radiation properties of the companion star which differ significantly from previous measurements. In this paper, we study the implications of these observations for the interaction rate of the unshocked pulsar wind with the stellar photons and the related consequences for fluxes of high energy and very high energy (VHE) gamma rays. We show that the signal should be strong enough to be detected with Fermi close to the periastron passage, unless the pulsar wind is strongly anisotropic or the Lorentz factor of the wind is smaller than 10{sup 3} or larger than 10{sup 5}. The higher luminosity of the optical star also has two important implications: (1) attenuation of gamma rays due to photon-photon pair production and (2) Compton drag of the unshocked wind. While the first effect has an impact on the light curve of VHE gamma rays, the second effect may significantly decrease the energy available for particle acceleration after termination of the wind.

  11. PULSAR WIND NEBULAE WITH THICK TOROIDAL STRUCTURE

    SciTech Connect

    Chevalier, Roger A.; Reynolds, Stephen P. E-mail: reynolds@ncsu.edu

    2011-10-10

    We investigate a class of pulsar wind nebulae that show synchrotron emission from a thick toroidal structure. The best studied such object is the small radio and X-ray nebula around the Vela pulsar, which can be interpreted as the result of interaction of a mildly supersonic inward flow with the recent pulsar wind. Such a flow near the center of a supernova remnant can be produced in a transient phase when the reverse shock reaches the center of the remnant. Other nebulae with a thick toroidal structure are G106.6+2.9 and G76.9+1.0. Their structure contrasts with young pulsar nebulae like the Crab Nebula and 3C 38, which show a more chaotic, filamentary structure in the synchrotron emission. In both situations, a torus-jet structure is present where the pulsar wind passes through a termination shock, indicating the flow is initially toroidal. We suggest that the difference is due to the Rayleigh-Taylor instability that operates when the outer boundary of the nebula is accelerating into freely expanding supernova ejecta. The instability gives rise to mixing in the Crab and related objects, but is not present in the nebulae with thick toroidal regions.

  12. Cherenkov Telescopes Results on Pulsar Wind Nebulae and Pulsars

    NASA Astrophysics Data System (ADS)

    Wilhelmi, Emma De Oña

    The last few years have seen a revolution in very high γ-ray astronomy (VHE; E>100 GeV) driven largely by a new generation of Cherenkov telescopes. These new facilities, namely H.E.S.S. (High Energy Stereoscopic System), MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescope) and its upgrade MAGIC 2, VERITAS (Very Energetic Radiation Imaging Telescope Array System) and CANGAROO (Collaboration of Australia and Nippon for a Gamma Ray Observatory in the Outback) were designed to increase the flux sensitivity in the energy regime of hundreds of GeV, expanding the observed energy range from 50 to multi-TeV, and fostered as a result a period of rapid growth in our understanding of the Non-ThermalUniverse. As a result of this fast development the number of pulsar wind nebulae (PWNe) detected has increased from a few in the early 90's to more than two dozen of firm candidates nowadays. Also, the low energy threshold achieved allows to investigate the pulsed spectra of the high energy pulsars powering PWNe. A review of the most relevant VHE results concerning pulsars and their relativistic winds is discussed here in the context of Cherenkov telescopes.

  13. FERMI-LAT SEARCH FOR PULSAR WIND NEBULAE AROUND GAMMA-RAY PULSARS

    SciTech Connect

    Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Buehler, R.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Bastieri, D.; Buson, S.; Bonamente, E.; Brigida, M.; Bruel, P.

    2011-01-01

    The high sensitivity of the Fermi-LAT (Large Area Telescope) offers the first opportunity to study faint and extended GeV sources such as pulsar wind nebulae (PWNe). After one year of observation the LAT detected and identified three PWNe: the Crab Nebula, Vela-X, and the PWN inside MSH 15-52. In the meantime, the list of LAT detected pulsars increased steadily. These pulsars are characterized by high energy loss rates ( E-dot ) from {approx}3 x 10{sup 33} erg s{sup -1} to 5 x 10{sup 38} erg s{sup -1} and are therefore likely to power a PWN. This paper summarizes the search for PWNe in the off-pulse windows of 54 LAT-detected pulsars using 16 months of survey observations. Ten sources show significant emission, seven of these likely being of magnetospheric origin. The detection of significant emission in the off-pulse interval offers new constraints on the {gamma}-ray emitting regions in pulsar magnetospheres. The three other sources with significant emission are the Crab Nebula, Vela-X, and a new PWN candidate associated with the LAT pulsar PSR J1023-5746, coincident with the TeV source HESS J1023-575. We further explore the association between the HESS and the Fermi source by modeling its spectral energy distribution. Flux upper limits derived for the 44 remaining sources are used to provide new constraints on famous PWNe that have been detected at keV and/or TeV energies.

  14. A MODEL OF THE SPECTRAL EVOLUTION OF PULSAR WIND NEBULAE

    SciTech Connect

    Tanaka, Shuta J.; Takahara, Fumio

    2010-06-01

    We study the spectral evolution of pulsar wind nebulae (PWNe) taking into account the energy injected when they are young. We model the evolution of the magnetic field inside a uniformly expanding PWN. Considering time-dependent injection from the pulsar and coolings by radiative and adiabatic losses, we solve the evolution of the particle distribution function. The model is calibrated by fitting the calculated spectrum to the observations of the Crab Nebula at an age of a thousand years. The spectral evolution of the Crab Nebula in our model shows that the flux ratio of TeV {gamma}-rays to X-rays increases with time, which implies that old PWNe are faint in X-rays, but not in TeV {gamma}-rays. The increase of this ratio is because the magnetic field decreases with time and is not because the X-ray emitting particles are cooled more rapidly than the TeV {gamma}-ray emitting particles. Our spectral evolution model matches the observed rate of the radio flux decrease of the Crab Nebula. This result implies that our magnetic field evolution model is close to the reality. Finally, from the viewpoint of the spectral evolution, only a small fraction of the injected energy from the Crab Pulsar needs to go to the magnetic field, which is consistent with previous studies.

  15. Recent Progress in Studies of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Slane, Patrick

    2008-01-01

    The synchrotron-emitting nebulae formed by energetic winds from young pulsars provide information on a wide range phenomena that contribute to their structure. High resolution X-ray observations reveal jets and toroidal structures in many systems, along with knot-like structures whose emission is observed to be time-variable. Large-scale filaments seen in optical and radio images mark instability regions where the expanding nebulae interact with the surrounding ejecta, and spectral studies reveal the presence of these ejecta in the form of thermal X-ray emission. Infrared studies probe the frequency region where evolutionary and magnetic field effects conspire to change the broadband synchrotron spectrum dramatically, and studies of the innermost regions of the nebulae provide constraints on the spectra of particles entering the nebula. At the highest energies, TeV gamma-ray observations provide a probe of the spectral region that, for low magnetic fields, corresponds to particles with energies just below the X-ray-emitting regime. Here I summarize the structure of pulsar wind nebulae and review several new observations that have helped drive a recent resurgence in theoretical modeling of these systems.

  16. PARTICLE TRANSPORT IN YOUNG PULSAR WIND NEBULAE

    SciTech Connect

    Tang Xiaping; Chevalier, Roger A. E-mail: rac5x@virginia.edu

    2012-06-20

    The model for pulsar wind nebulae (PWNe) as a result of the magnetohydrodynamic (MHD) downstream flow from a shocked, relativistic pulsar wind has been successful in reproducing many features of the nebulae observed close to central pulsars. However, observations of well-studied young nebulae like the Crab Nebula, 3C 58, and G21.5-0.9 do not show the toroidal magnetic field on a larger scale that might be expected in the MHD flow model; in addition, the radial variation of spectral index due to synchrotron losses is smoother than expected in the MHD flow model. We find that pure diffusion models can reproduce the basic data on nebular size and spectral index variation for the Crab, 3C 58, and G21.5-0.9. Most of our models use an energy-independent diffusion coefficient; power-law variations of the coefficient with energy are degenerate with variation in the input particle energy distribution index in the steady state, transmitting boundary case. Energy-dependent diffusion is a possible reason for the smaller diffusion coefficient inferred for the Crab. Monte Carlo simulations of the particle transport allowing for advection and diffusion of particles suggest that diffusion dominates over much of the total nebular volume of the Crab. Advection dominates close to the pulsar and is likely to play a role in the X-ray half-light radius. The source of diffusion and mixing of particles is uncertain, but may be related to the Rayleigh-Taylor instability at the outer boundary of a young PWN or to instabilities in the toroidal magnetic field structure.

  17. Pulsar wind model for the spin-down behavior of intermittent pulsars

    SciTech Connect

    Li, L.; Tong, H.; Yan, W. M.; Yuan, J. P.; Wang, N.; Xu, R. X.

    2014-06-10

    Intermittent pulsars are part-time radio pulsars. They have higher slow down rates in the on state (radio-loud) than in the off state (radio-quiet). This gives evidence that particle wind may play an important role in pulsar spindown. The effect of particle acceleration is included in modeling the rotational energy loss rate of the neutron star. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24, PSR J1841–0500, and PSR J1832+0029) allows their magnetic fields and inclination angles to be calculated simultaneously. The theoretical braking indices of intermittent pulsars are also given. In the pulsar wind model, the density of the particle wind can always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. The duty cycle of particle wind can be determined from timing observations. It is consistent with the duty cycle of the on state. Inclination angle and braking index observations of intermittent pulsars may help to test different models of particle acceleration. At present, the inverse Compton scattering induced space charge limited flow with field saturation model can be ruled out.

  18. Magnetized stimulated scattering in pulsar winds

    NASA Technical Reports Server (NTRS)

    Sincell, Mark W.; Krolik, Julian H.

    1992-01-01

    The effects of stimulated scattering on a collimated high brightness temperature beam of photons traversing a relativistically streaming magnetized plasma are studied. Under the assumption that the center of the photon beam is parallel to the bulk motion, we calculate the scattering rate as a function of the angular spread of the beam and the Lorentz factor gamma. Magnetization changes the photon recoil, without which stimulated scattering has no effect. It also introduces a strong dependence on frequency and polarization: if the photon frequency matches the electron cyclotron frequency, the scattering rate of photons polarized perpendicular to the magnetic field can be substantially enhanced relative to Thomson, and if the photon frequency is much less than the cyclotron frequency, the scattering is suppressed. Applying these calculations to pulsars, we find that stimulated scattering of the radio beam in the magnetized wind believed to exist outside the light cylinder can substantially alter the spectrum and polarization state of the radio signal. We suggest that the scattering rate is so high in some pulsars that the ability of the radio signal to penetrate the pulsar magnetosphere requires modification of either the conventional model of the magnetosphere or assumptions about the effects of stimulated scattering upon a beam.

  19. Radio Observations of Elongated Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Ng, Stephen C.-Y.

    2015-08-01

    The majority of pulsars' rotational energy is carried away by relativistic winds, which are energetic particles accelerated in the magnetosphere. The confinement of the winds by the ambient medium result in synchrotron bubbles with broad-band emission, which are commonly referred to as pulsar wind nebulae (PWNe). Due to long synchrotron cooling time, a radio PWN reflects the integrated history of the system, complementing information obtained from the X-ray and higher energy bands. In addition, radio polarization measurements can offer a powerful probe of the PWN magnetic field structure. Altogether these can reveal the physical conditions and evolutionary history of a system.I report on preliminary results from high-resolution radio observations of PWNe associated with G327.1-1.1, PSRs J1015-5719, B1509-58, and J1549-4848 taken with the Australia Telescope Compact Array (ATCA). Their magnetic field structure and multiwavelength comparison with other observations are discussed.This work is supported by a ECS grant of the Hong Kong Government under HKU 709713P. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  20. PROPAGATION AND STABILITY OF SUPERLUMINAL WAVES IN PULSAR WINDS

    SciTech Connect

    Mochol, Iwona; Kirk, John G. E-mail: john.kirk@mpi-hd.mpg.de

    2013-07-01

    Nonlinear electromagnetic waves with superluminal phase velocity can propagate in the winds around isolated pulsars, and around some pulsars in binary systems. Using a short-wavelength approximation, we find and analyze an integrable system of equations that govern their evolution in spherical geometry. A confined mode is identified that stagnates to finite pressure at large radius and can form a precursor to the termination shock. Using a simplified criterion, we find this mode is stable for most isolated pulsars, but may be unstable if the external pressure is high, such as in the pulsar wind nebulae in starburst galaxies and in W44. Pulsar winds in eccentric binary systems, such as PSR 1259-63, may go through phases with stable and unstable electromagnetic precursors, as well as phases in which the density is too high for these modes to propagate.

  1. High Energy Emission from Pulsar Magnetospheres and Winds

    NASA Astrophysics Data System (ADS)

    Spitkovsky, Anatoly

    Recent gamma-ray observations of pulsars and their nebulae suggest an important role played by magnetic reconnection in determining the structure of the magnetosphere and the wind and in the acceleration of particles that lead to the high energy emission. Strong current sheets that are susceptible to magnetic dissipation are found near the light cylinder of the pulsar and persist throughout the wind. This proposal investigates the processes that occur in these current sheets, and determines their structure and particle acceleration properties. A suite of relativistic MHD and particle-in-cell kinetic simulations will be used to obtain the global 3D geometry of the magnetosphere, flow geometry in the current sheet, and calculate the dissipation of the current both near the pulsar and in the termination shock of the pulsar wind. The results will be applied to modeling the beaming in pulsar gamma-ray light curves, and to understanding particle acceleration in broadband and flaring nebular emission.

  2. Faint X-Ray Structure in the Crab Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Seward, F. D.; Tucker, W. H.; Fesen, R. A.

    2006-12-01

    We report on a Chandra observation of the Crab Nebula that gives the first clear view of the faint boundary of the Crab's X-ray-emitting pulsar wind nebula. There is structure in all directions. Fingers, loops, bays, and the south pulsar jet all indicate that either filamentary material or the magnetic field is controlling the relativistic electrons. In general, spectra soften as distance from the pulsar increases but do not change rapidly along linear features. This is particularly true for the pulsar jet. The termination of the jet is abrupt; the east side is close to an [O III] optical filament, which may be blocking propagation on this side. We argue that linear features have ordered magnetic fields and that the structure is determined by the synchrotron lifetime of particles diffusing perpendicular and parallel to the magnetic field. We find no significant evidence for thermal X-rays inside the filamentary envelope.

  3. HST Imaging of the Pulsar Wind Nebula CTB 80

    NASA Astrophysics Data System (ADS)

    Hester, J.

    2000-12-01

    CTB80 is a remarkable pulsar wind nebula seen as the pulsar is passing through the shell of its own supernova remnant. HST images taken in the light of [O III], [S II], and Hα show the structure of a complex bow shock with a radiative central component and two Balmer-dominated lobes. Continuum images show the presence of a small diffuse knot of emission offset approximately 0.5'' from the location of the radio pulsar along a line bisecting the lobes. We interpret the knot as synchrotron emission, and note that its luminosity and offset from the pulsar make it remarkably like the knot seen 0.5'' to the south east of the Crab pulsar. We propose that the structure of the bow shock in CTB 80 is the result of an axisymmetric bipolar pulsar wind, much like that seen in the Crab Nebula, in which polar jets from the pulsar are responsible for forming the lobes. Shear flow from the relativistic jets may be responsible for stripping the cooling and recombination layer off of the back side of the shocks in the lobes. We predict that X-ray images of CTB 80 will show the presence of both a strong equatorial wind and synchrotron jets along the axis defined by the pulsar, the knot, and the lobes.

  4. X-Ray Observations of the Young Pulsar J1357—6429 and Its Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Chang, Chulhoon; Pavlov, George G.; Kargaltsev, Oleg; Shibanov, Yurii A.

    2012-01-01

    We observed the young pulsar J1357—6429 with the Chandra and XMM-Newton observatories. The pulsar spectrum fits well a combination of an absorbed power-law model (Γ = 1.7 ± 0.6) and a blackbody model (kT = 140+60 - 40 eV, R ~ 2 km at the distance of 2.5 kpc). Strong pulsations with pulsed fraction of 42% ± 5%, apparently associated with the thermal component, were detected in 0.3-1.1 keV. Surprisingly, the pulsed fraction at higher energies, 1.1-10 keV, appears to be smaller, 23% ± 4%. The small emitting area of the thermal component either corresponds to a hotter fraction of the neutron star surface or indicates inapplicability of the simplistic blackbody description. The X-ray images also reveal a pulsar wind nebula (PWN) with complex, asymmetric morphology comprised of a brighter, compact PWN surrounded by the fainter, much more extended PWN whose spectral slopes are Γ = 1.3 ± 0.3 and Γ = 1.7 ± 0.2, respectively. The extended PWN with the observed flux of ~7.5 × 10-13 erg s-1 cm-2 is a factor of 10 more luminous then the compact PWN. The pulsar and its PWN are located close to the center of the extended TeV source HESS J1356-645, which strongly suggests that the very high energy emission is powered by electrons injected by the pulsar long ago. The X-ray to TeV flux ratio, ~0.1, is similar to those of other relic PWNe. We found no other viable candidates to power the TeV source. A region of diffuse radio emission, offset from the pulsar toward the center of the TeV source, could be synchrotron emission from the same relic PWN rather than from the supernova remnant.

  5. An axisymmetric magnetohydrodynamic model for the Crab pulsar wind bubble

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.; Li, Zhi-Yun

    1992-01-01

    We extend Kennel and Coroniti's (1984) spherical magnetohydrodynamic models for the Crab Nebula to include the pinching effect of the toroidal magnetic field. Since the bulk nebular flow is likely to be very submagnetosonic, a quasi-static treatment is possible. We show that the pinching effect can be responsible for the observed elongation of the pulsar wind bubble, as indicated by the surface brightness contours of optical synchrotron radiation. From the observed elongation we estimate a value for sigma, the ratio of Poynting flux to plasma kinetic energy flux in the free pulsar wind, which is consistent with previous results from spherical models. Using the inferred magnetic field configuration inside the pulsar wind bubble, combined with the observed dimensions of the X-ray nebula, we are able to constrain the particle distribution function. We conclude that, for a power-law injection function, the maximum energy has to be much larger in the pulsar equatorial region than in the polar region.

  6. Guitar with a bow: a jet-like X-ray-emitting feature associated a fast-moving pulsar

    NASA Astrophysics Data System (ADS)

    Wang, Q. Daniel

    2011-09-01

    The Guitar Nebula is known to be a ram-pressure confined pulsar wind nebula associated with the very fast-moving pulsar B2224+65. Existing observations at two epochs have shown an unexpected 2 arcmin long X-ray-emitting jet-like feature emanating from the pulsar and offset from its proper motion direction by 118 degree. We propose a deep third epoch observation of this system in order to measure the X-ray spectral gradient across the feature as well as to confirm its proper motion, its morphological variation with time, and the presence of a counter jet. We will then critically test scenarios proposed to explain this system, which represents a class of similarly enigmatic objects recently discovered locally and in the central region of our Galaxy.

  7. Pulsar Wind Nebulae, Space Velocities and Supernova Remnant

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The original proposal for this LTSA grant was for X-ray studies of pulsars, and especially pulsar wind nebulae and what they could tell us about pulsar properties, especially their space velocities. By any metric, this program has been very successful. No fewer than 14 papers on directly related topics (and several dozen more on related topics) have been published in refereed journals with the PI as lead or co-author, all observational results that have had significant impact on the field. These include the first X-ray detection of the "Duck" pulsar, a clear demonstration that estimated pulsar ages can be off by over an order of magnitude (via observations of the young supernova remnant G11.2-0.3) and the detection of the first pulsar wind nebula around a millisecond pulsar. These publications have also resulted in 4 press releases. Moreover, they also represent the thesis work of two PhD students at MIT (Froney Crawford and Mike Pivovaroff) and one postdoctoral fellow, Bryan Gaensler, now Assistant Professor at Harvard.

  8. High-energy flux evolution of Pulsar Wind Nebulae

    SciTech Connect

    Mattana, F.; Falanga, M.; Goetz, D.

    2008-12-24

    The very high energy {gamma}-ray spectra of Pulsar Wind Nebulae are interpreted as due to inverse Compton scattering of ultrarelativistic electrons on the ambient photons, whereas their X-ray spectra are due to synchrotron emission. We investigate the relation between the {gamma}- and X-ray emission and the pulsars' spin-down luminosity and characteristic age. We find that the {gamma}-to X-ray flux ratio of the nebulae is inversely proportional to the spin-down luminosity ({proportional_to}E{sup -1.9}) and to the characteristic age ({proportional_to}{tau}{sub c}{sup 2.2}) of the parent pulsar. We interpret these results as due to the evolution of the electron energy distribution and the nebular dynamics, supporting the idea of so-called relic pulsar wind nebulae. These empirical relations provide a new tool to classify unidentified diffuse {gamma}-ray sources and to estimate the spin-down luminosity and characteristic age for four rotation powered pulsars with no detected pulsation from the X- and {gamma}--ray properties of the associated pulsar wind nebulae.

  9. Pulsars

    NASA Astrophysics Data System (ADS)

    Stappers, Benjamin W.

    2012-04-01

    Pulsars can be considered as the ultimate time-variable source. They show variations on time-scales ranging from nanoseconds to as long as years, and they emit over almost the entire electromagnetic spectrum. The dominant modulation is associated with the rotation period, which can vary from slighty more than a millisecond to upwards of ten seconds (if we include the magnetars). Variations on time-scales shorter than the pulse period are mostly associated with emission processes and are manifested as giant pulses, microstructure and sub-pulses (to name a few). On time-scales of a rotation to a few hundred rotations are other phenomena also associated with the emission, such as nulling, moding, drifting and intermittency. By probing these and slightly longer time-scales we find that pulsars exhibit ``glitches'', which are rapid variations in spin rates. They are believed to be related to the interaction between the superfluid interior of the neutron star and the outer crust. Detailed studies of glitches can reveal much about the properties of the constituents of neutron stars-the only way to probe the physics of material at such extreme densities. Time-scales of about an hour or longer reveal that some pulsars are in binary systems, in particular the most rapidly rotating systems. Discovering and studying those binary systems provides vital clues to the evolution of massive stars, while some of the systems are also the best probes of strong-field gravity theories; the elusive pulsar-black hole binary would be the ultimate system. Pulsars are tools that allow us to probe a range of phenomena and time-scales. It is possible to measure the time of arrival of pulses from some pulsars to better than a few tens of nanoseconds over years, making them some of the most accurate clocks known. Concerning their rotation, deviations from sphericity may cause pulsars to emit gravitational waves which might then be detected by next-generation gravitational-wave detectors. Pulsars

  10. Gamma-rays from pulsar wind nebulae in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Mannheim, Karl; Elsässer, Dominik; Tibolla, Omar

    2012-07-01

    Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) [1] and M82 (Acciari et al., 2009) [2]. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 105 years. A large number of 3 × 104 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.

  11. Constraining the Turbulence Scale and Mixing of a Crushed Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Ng, Chi Yung; Ma, Y. K.; Bucciantini, Niccolo; Slane, Patrick O.; Gaensler, Bryan M.; Temim, Tea

    2016-04-01

    Pulsar wind nebulae (PWNe) are synchrotron-emitting nebulae resulting from the interaction between pulsars' relativistic particle outflows and the ambient medium. The Snail PWN in supernova remnant G327.1-1.1 is a rare system that has recently been crushed by supernova reverse shock. We carried out radio polarization observations with the Australia Telescope Compact Array and found highly ordered magnetic field structure in the nebula. This result is surprising, given the turbulent environment expected from hydrodynamical simulations. We developed a toymodel and compared simple simulations with observations to constrain the characteristic turbulence scale in the PWN and the mixing with supernova ejecta. We estimate that the turbulence scale is about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50-75%. The latter implies substantial mixing of the pulsar wind with the surrounding supernova ejecta.This work is supported by an ECS grant of the Hong Kong Government under HKU 709713P. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  12. Production of Gamma-Rays in the Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Bednarek, W.; Bartosik, M.

    2004-10-01

    We construct the time dependent hadronic-leptonic radiation model for the high energy processes inside the pulsar wind nebulae (PWNe). This model is based on the hypothesis that heavy nuclei are effi- ciently accelerated in the vicinity of young pulsars. Different energy loss processes of nuclei and accel- erated by them leptons are considered in order to obtain the equilibrium spectra of these particles in- side the nebula at an arbitrary time after the pulsar formation. We calculate the multiwavelength spec- tra from specific PWNe expected from different lep- tonic and hadronic processes. From normalization of the calculated synchrotron spectrum to the observed spectrum at low energies, the expected TeV gamma- ray fluxes from a few PWNe are predicted and its possible detectability by the future TeV telescopes is discussed. Key words: Pulsars: nebulae - radiation mecha- nisms: gamma-rays.

  13. Pulsed high-energy γ-rays from thermal populations in the current sheets of pulsar winds

    NASA Astrophysics Data System (ADS)

    Arka, I.; Dubus, G.

    2013-02-01

    Context. More than one hundred pulsars have been detected up to now at GeV energies by the Large Area Telescope (LAT) on the Fermi gamma-ray observatory. Current modelling proposes that the high-energy emission comes from outer magnetospheric gaps, but radiation from the equatorial current sheet that separates the two magnetic hemispheres outside the light cylinder has also been investigated. Aims: We discuss the region outside the light cylinder, the "near wind" zone. We investigate the possibility that synchrotron radiation emitted by thermal populations in the equatorial current sheet of the pulsar wind in this region can explain the lightcurves and spectra observed by Fermi/LAT. Methods: We used analytical estimates as well as detailed numerical computation to calculate the γ-ray luminosities, lightcurves, and spectra of γ-ray pulsars. Results: Many of the characteristics of the γ-ray pulsars observed by Fermi/LAT can be reproduced by our model, most notably the position of these objects in the P - Ṗ diagram, and the range of γ-ray luminosities. A testable result is a sub-exponential cutoff with an index b = 0.35. We also predict the existence of a population of pulsars with cutoff energies in the MeV range. These have systematically lower spindown luminosities than the Fermi/LAT-detected pulsars. Conclusions: It is possible for relativistic populations of electrons and positrons in the current sheet of a pulsar's wind immediately outside the light cylinder to emit synchrotron radiation that peaks in the sub-GeV to GeV regime, with γ-ray efficiencies similar to those observed for the Fermi/LAT pulsars.

  14. Chandra Confirmation of a Pulsar Wind Nebula in DA 495

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Safi-Harb, S.; Landecker, T.L.; Kothes, R.; Camilo, F.

    2008-01-01

    As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nontherma1 nebula 40" in diameter exhibiting a power-law spectrum with photon index Gamma = 1.63, typical of a pulsar wind nebula. Morphologically, the nebula appears to be slightly extended along a direction, in projection on the sky, previously demonstrated to be of significance in radio and ASCA observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5" from the point source, but energetic arguments suggest that it is not the resolved termination shock of the pulsar wind against the ambient medium. Finally, we argue based on synchrotron lifetimes in the nebular magnetic field that DA 495 represents the first example of a pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind.

  15. X-RAY OBSERVATIONS OF THE YOUNG PULSAR J1357-6429 AND ITS PULSAR WIND NEBULA

    SciTech Connect

    Chang, Chulhoon; Pavlov, George G.; Kargaltsev, Oleg; Shibanov, Yurii A. E-mail: pavlov@astro.psu.edu E-mail: shib@astro.ioffe.rssi.ru

    2012-01-10

    We observed the young pulsar J1357-6429 with the Chandra and XMM-Newton observatories. The pulsar spectrum fits well a combination of an absorbed power-law model ({Gamma} = 1.7 {+-} 0.6) and a blackbody model (kT = 140{sup +60}{sub -40} eV, R {approx} 2 km at the distance of 2.5 kpc). Strong pulsations with pulsed fraction of 42% {+-} 5%, apparently associated with the thermal component, were detected in 0.3-1.1 keV. Surprisingly, the pulsed fraction at higher energies, 1.1-10 keV, appears to be smaller, 23% {+-} 4%. The small emitting area of the thermal component either corresponds to a hotter fraction of the neutron star surface or indicates inapplicability of the simplistic blackbody description. The X-ray images also reveal a pulsar wind nebula (PWN) with complex, asymmetric morphology comprised of a brighter, compact PWN surrounded by the fainter, much more extended PWN whose spectral slopes are {Gamma} = 1.3 {+-} 0.3 and {Gamma} = 1.7 {+-} 0.2, respectively. The extended PWN with the observed flux of {approx}7.5 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2} is a factor of 10 more luminous then the compact PWN. The pulsar and its PWN are located close to the center of the extended TeV source HESS J1356-645, which strongly suggests that the very high energy emission is powered by electrons injected by the pulsar long ago. The X-ray to TeV flux ratio, {approx}0.1, is similar to those of other relic PWNe. We found no other viable candidates to power the TeV source. A region of diffuse radio emission, offset from the pulsar toward the center of the TeV source, could be synchrotron emission from the same relic PWN rather than from the supernova remnant.

  16. Particle acceleration and non-thermal emission in Pulsar Wind Nebulae from relativistic MHD simulations

    NASA Astrophysics Data System (ADS)

    Olmi, B.; Del Zanna, L.; Amato, E.; Bucciantini, N.; Bandiera, R.

    2015-09-01

    Pulsar wind nebulae are among the most powerful particle accelerators in the Galaxy with acceleration efficiencies that reach up to 30% and maximum particle energies in the PeV range. In recent years relativistic axisymmetric MHD models have proven to be excellent tools for describing the physics of such objects, and particularly successful at explaining their high energy morphology, down to very fine details. Nevertheless, some important aspects of the physics of PWNe are still obscure: the mechanism(s) responsible for the acceleration of particles of all energies is (are) still unclear, and the origin of the lowest energy (radio emitting) particles is most mysterious. The correct interpretation of the origin of radio emitting particles is of fundamental importance, as this holds information about the amount of pair production in the pulsar magnetosphere, and hence on the role of pulsars as antimatter factories. On the other hand, the long lifetimes of these particles against synchrotron losses, allows them to travel far from their injection location, making their acceleration site difficult to constrain. As far as the highest energy (X and gamma-ray emitting) particles are concerned, their acceleration is commonly believed to occur at the pulsar wind termination shock. But since the upstream flow is thought to have non-uniform properties along the shock surface, important constraints on the acceleration mechanism(s) could come from exact knowledge of the location and flow properties where particles are being accelerated. We investigate in detail both topics by means of 2D numerical MHD simulations. Different assumptions on the origin of radio particles and more generally on the injection sites of all particles are considered, and the corresponding emission properties are computed. We discuss the physical constraints that can be inferred from comparison of the synthetic emission properties against multiwavelength observations of the PWN class prototype, the Crab

  17. On the primary beam deceleration in the pulsar wind

    NASA Astrophysics Data System (ADS)

    Prokofev, V. V.; Arzamasskiy, L. I.; Beskin, V. S.

    2015-12-01

    We investigate the motion of the primary beam outside the light cylinder in the pulsar wind. Inside the light cylinder both primary and secondary plasma move along dipole magnetic field lines where their energies can be arbitrary. But at larger distances the theory predicts quasi-radial motion with the velocity exactly corresponding to the drift velocity which cannot be the same for primary and secondary plasma. Hence, the deceleration of the primary beam is to take place simultaneously resulting in the acceleration of the secondary plasma. We investigate this process in the three-fluid magnetohydrodynamical approximation and demonstrate that for most pulsars the energy of the beam remains practically unchanged. Only for young radio pulsars (Crab, Vela) essential deceleration up to the energy of the secondary plasma takes place outside the fast magnetosonic surface rF ˜ (10-100)RL, the energy of secondary plasma itself increasing insufficiently.

  18. X-RAY EVOLUTION OF PULSAR WIND NEBULAE

    SciTech Connect

    Bamba, Aya; Anada, Takayasu; Dotani, Tadayasu; Ebisawa, Ken; Yamazaki, Ryo; Vink, Jacco

    2010-08-20

    During the search for counterparts of very high energy gamma-ray sources, we serendipitously discovered large, extended, low surface brightness emission from pulsar wind nebulae (PWNe) around pulsars with the ages up to {approx}100 kyr, a discovery made possible by the low and stable background of the Suzaku X-ray satellite. A systematic study of a sample of eight of these PWNe, together with Chandra data sets, has revealed that the nebulae keep expanding up to {approx}100 kyr, although the timescale of the synchrotron X-ray emission is only {approx}60 yr for typical magnetic fields of 100 {mu}G. Our result suggests that the accelerated electrons up to {approx}80 TeV can escape from the PWNe without losing most energies. Moreover, in order to explain the observed correlation between the X-ray size and the pulsar spin-down age, the magnetic field strength in the PWNe must decrease with time.

  19. The NuSTAR Program for Pulsar-wind Nebulae

    NASA Astrophysics Data System (ADS)

    Madsen, Kristin; An, H.; Boggs, S. E.; Craig, W. W.; Freyer, C.; Grefenstette, B.; Hailey, C. J.; Humensky, B.; Jakobsen, S.; Kaspi, V.; Lopez, L. A.; Miyasaka, H.; Mori, K.; Nynka, M.; Pivovaroff, M.; Reynolds, S. P.; Kitaguchi, T.; Westergaard, N. J.; Wik, D. R.; Zoglauer, A.; Christensen, F.; Harrison, F.; Stern, D.; Zhang, W.; NuSTAR Team

    2013-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR), successfully launched in June 2012, is the first telescope to bring the the hard X-ray (3 to 79 keV) sky into focus. NuSTAR's combination of sensitivity and angular resolution enable it, for the first time, to study the morphology of pulsar wind nebuale (PWNe) above 10 keV. PWNe exhibit particles accelerated in pulsar magnetospheres and/or at relativistic wind- termination shocks; as those particles propagate out and suffer radiative and adiabatic losses, their synchrotron radiation contains morphological and spectral clues to the nature of particle acceleration and propagation. NuSTAR's hard x-ray band coupled with its imaging capabilities will address these questions, and in this poster we present NuSTAR plans for observing PWNe as well as preliminary results from the most famous PWN; the Crab.

  20. Relativistic Pulsar Winds with Pressure Anisotropy and Heat Flow

    NASA Astrophysics Data System (ADS)

    Tenbarge, Jason; Hazeltine, Richard; Mahajan, Swadesh

    2008-11-01

    A newly developed covariant fluid model for magnetized plasmas, incorporating anisotropy in both temperature and heat flow, is used to study equatorial radial profiles of density, velocity, magnetic field, pressure, and heat flow in the hot, strongly magnetized wind region beyond the light cylinder of pulsar magnetospheres. Radiative losses are assumed to have isotropized the wind region plasma so that PP. Fluid velocities are taken as mildly relativistic, while temperatures are ultra-relativistic. This study of pulsar magnetospheres extends the work by Tsikarishvili et al. to a more general fluid closure including heat flow. The general covariant fluid model in spherical geometry and equations of state for arbitrary temperature will also be presented for more general applicability. J. M. TenBarge, R. D. Hazeltine, and S. M. Mahajan, Phys. Plasmas 15, 062112 (2008)., E. G. Tsikarishvili, A. D. Rogava, and D. G. Tsiklauri, Ap. J. 439, 822 (1995).

  1. Rotational evolution of the Crab pulsar in the wind braking model

    NASA Astrophysics Data System (ADS)

    Kou, F. F.; Tong, H.

    2015-06-01

    The pulsar wind model is updated by considering the effect of particle density and pulsar death. It can describe both the short-term and long-term rotational evolution of pulsars consistently. It is applied to model the rotational evolution of the Crab pulsar. The pulsar is spun down by a combination of magnetic dipole radiation and particle wind. The parameters of the Crab pulsar, including magnetic field, inclination angle, and particle density are calculated. The primary particle density in acceleration region is about 103 times the Goldreich-Julian charge density. The lower braking index between glitches is due to a larger outflowing particle density. This may be glitch induced magnetospheric activities in normal pulsars. Evolution of braking index and the Crab pulsar in P-dot{P} diagram are calculated. The Crab pulsar will evolve from magnetic dipole radiation dominated case towards particle wind-dominated case. Considering the effect of pulsar `death', the Crab pulsar (and other normal pulsars) will not evolve to the cluster of magnetars but downwards to the death valley. Different acceleration models are also considered. Applications to other sources are also discussed, including pulsars with braking index measured, and the magnetar population.

  2. Three-dimensional analytical description of magnetized winds from oblique pulsars

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander; Philippov, Alexander; Spitkovsky, Anatoly

    2016-04-01

    Rotating neutron stars, or pulsars and magnetars, are plausibly the source of power behind many astrophysical systems, such as gamma-ray bursts, supernovae, pulsar wind nebulae, and supernova remnants. In the past several years, three-dimensional (3D) numerical simulations made it possible to compute pulsar spin-down luminosity from first principles and revealed that oblique pulsar winds are more powerful than aligned ones. However, what causes this enhanced power output of oblique pulsars is not understood. In this work, using time-dependent 3D magnetohydrodynamic and force-free simulations, we show that, contrary to the standard paradigm, the open magnetic flux, which carries the energy away from the pulsar, is laterally non-uniform. We argue that this non-uniformity is the primary reason for the increased luminosity of oblique pulsars. To demonstrate this, we construct simple analytic descriptions of aligned and orthogonal pulsar winds and combine them to obtain an accurate 3D description of the pulsar wind for any obliquity. Our approach describes both the warped magnetospheric current sheet and the smooth variation of pulsar wind properties outside of it. We find that the jump in magnetic field components across the current sheet decreases with increasing obliquity, which could be a mechanism that reduces dissipation in near-orthogonal pulsars. Our analytical description of the pulsar wind can be used for constructing models of pulsar gamma-ray emission, pulsar wind nebulae, neutron star powered ultra-luminous X-ray sources, and magnetar-powered core-collapse gamma-ray bursts and supernovae.

  3. Neutrinos of energy approximately 10(16) eV from gamma-ray bursts in pulsar wind bubbles.

    PubMed

    Guetta, Dafne; Granot, Jonathan

    2003-05-23

    The supranova model for gamma-ray bursts (GRBs) is becoming increasingly more popular. In this scenario the GRB occurs weeks to years after a supernova explosion, and is located inside a pulsar wind bubble (PWB). Protons accelerated in the internal shocks that emit the GRB may interact with the external PWB photons producing pions which decay into approximately 10(16) eV neutrinos. A km(2) neutrino detector would observe several events per year correlated with the GRBs. PMID:12785881

  4. THE PROPER MOTION AND X-RAY ANALYSIS OF THE PULSAR WIND NEBULA, PSR J1741-2054 USING CHANDRA.

    NASA Astrophysics Data System (ADS)

    Auchettl, Katie; Slane, Patrick O.; Romani, Roger W.; Kargaltsev, Oleg; Pavlov, George G.

    2014-08-01

    A pulsar dissipates its rotational energy by generating relativistic winds, which in turn produces a population of high energy electrons and positions that we observe as a synchrotron emitting nebula. If the pulsar has a high space velocity, the corresponding nebula will have a bow-shock morphology due to the pulsar wind being confined by ram pressure. Pulsar wind nebulae (PWNe) provide a good test bed to study the dynamics and interaction of relativistic outflows with their environment and the corresponding shocks that result from these interactions. They can also aid in understanding the evolution of the neutron star and the properties of the local medium with which they are interacting. Here we report on the X-ray analysis of PSR J1741-2054 carried out as a part of the Chandra XVP program (6 ACIS-S observations, totalling ~300 ks over 5 months). By registering this new epoch of observations using X-ray point sources in the field of view to an archival observation taken 3.2 years earlier, we are able to measure the proper motion of the pulsar with >3σ significance. We also investigate the spatial and spectral properties of the pulsar, its compact nebula and extended tail. We find that the compact nebula can be well described with an absorbed power-law with photon index of Γ=1.6+/-0.2, while the tail shows no evidence of variation in the spectral index with the distance from the pulsar. We have also investigated the X-ray spectrum of the neutron star. We find nonthermal emission accompanied by a significant thermal component and will provide constraints on the overall nature of the emission.

  5. Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet's Tale

    NASA Astrophysics Data System (ADS)

    Arons, Jonathan

    2012-11-01

    I outline, from a theoretical and somewhat personal perspective, significant features of Pulsar Wind Nebulae (PWNe) as Cosmic Accelerators. I pay special attention to the recently discovered gamma ray "flares" in the Crab Nebula's emission, focusing on the possibility, raised by the observations, that the accelerating electric field exceeds the magnetic field, suggesting that reconnection in the persistent current layer (a "current sheet") plays a significant role in the behavior of this well studied Pevatron. I address the present status of the termination shock model for the particle accelerator that converts the wind flow energy to the observed non-thermal particle spectra, concluding that it has a number of major difficulties related to the transverse magnetic geometry of the shock wave. I discuss recent work on the inferred pair outflow rates, which are in excess of those predicted by existing theories of pair creation, and use those results to point out that the consequent mass loading of the wind reduces the wind's bulk flow 4-velocity to the point that dissipation of the magnetic field in a pulsar's wind upstream of the termination shock is restored to life as a viable model for the solution of the " σ" problem. I discuss some suggestions that current starvation in the current flow supporting the structured ("striped") upstream magnetic field perhaps induces a transition to superluminal wave propagation. I show that current starvation probably does not occur, because those currents are carried in the current sheet separating the stripes rather than in the stripes themselves.

  6. Solution to the Sigma Problem of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Porth, Oliver; Komissarov, Serguei S.; Keppens, Rony

    2014-03-01

    Pulsar wind nebulae (PWN) provide a unique test-bed for the study of highly relativistic processes right at our astronomical doorstep. In this contribution we will show results from the first 3D RMHD simulations of PWN. Of key interest to our study is the long standing "sigma-problem" that challenges MHD models of Pulsars and their nebulae now for 3 decades. Earlier 2D MHD models were very successful in reproducing the morphology of the inner Crab nebula showing a jet, torus, concentric wisps and a variable knot. However, these models are limited to a purely toroidal field geometry which leads to an exaggerated compression of the termination shock and polar jet — in contrast to the observations. In three dimensions, the toroidal field structure is susceptible to current driven instabilities; hence kink instability and magnetic dissipation govern the dynamics of the nebula flow. This leads to a resolution of the sigma-problem once also the pulsar's obliqueness (striped wind) is taken into account. In addition, we present polarized synchrotron maps constructed from the 3D simulations, showing the wealth of morphological features reproduced in 2D is preserved in the 3D case.

  7. Implications of HESS Observations of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    de Jager, Ocker C.; Djannati-Ataï, Arache

    Even before the discovery of pulsars, pulsar wind nebulae (PWN) like the Crab Nebula were identified as belonging to a class of cosmic radio sources with rela-tivistic electrons moving in magnetized plasmas to give the continuum radiation as observed. Visionaries like [36] already predicted that we should be able to measure the magnetic field strength in PWN using the combination of synchrotron and inverse Compton (IC) radiation. Following this, [43] were the first to provide us with a sophisticated one dimensional (1D) magneto hydrodynamical models (MHD) model of the Crab Nebula, which predicted a magnetic field strength distribution, consistent with broadband multi-wavelength (radio through very high energy gamma-ray) constraints [12,25, 39].

  8. Experimental Constraints on γ-Ray Pulsar Gap Models and the Pulsar GeV to Pulsar Wind Nebula TeV Connection

    NASA Astrophysics Data System (ADS)

    Abeysekara, A. U.; Linnemann, J. T.

    2015-05-01

    The pulsar emission mechanism in the gamma ray energy band is poorly understood. Currently, there are several models under discussion in the pulsar community. These models can be constrained by studying the collective properties of a sample of pulsars, which became possible with the large sample of gamma ray pulsars discovered by the Fermi Large Area Telescope. In this paper we develop a new experimental multi-wavelength technique to determine the beaming factor ≤ft( {{f}{Ω }} \\right) dependance on spin-down luminosity of a set of GeV pulsars. This technique requires three input parameters: pulsar spin-down luminosity, pulsar phase-averaged GeV flux, and TeV or X-ray flux from the associated pulsar wind nebula (PWN). The analysis presented in this paper uses the PWN TeV flux measurements to study the correlation between {{f}{Ω }} and \\dot{E}. The measured correlation has some features that favor the Outer Gap model over the Polar Cap, Slot Gap, and One Pole Caustic models for pulsar emission in the energy range of 0.1-100 GeV, but one must keep in mind that these simulated models failed to explain many of the most important pulsar population characteristics. A tight correlation between the pulsar GeV emission and PWN TeV emission was also observed, which suggests the possibility of a linear relationship between the two emission mechanisms. In this paper we also discuss a possible mechanism to explain this correlation.

  9. Gamma-ray connection of Pulsars-Pulsar Wind Nebulae: From GeV to TeV energies

    NASA Astrophysics Data System (ADS)

    López-Coto, Rubén; de Ona Wilhelmi, Emma

    2015-08-01

    Pulsars are the remnants of massive star explosions and Pulsar Wind Nebulae (PWNe) are the bubbles of relativistic particles and magnetic field surrounding pulsars. The acceleration in PWNe is produced when the pulsar's relativistic wind interacts with its surrounding medium and particles are accelerated at the shock region. The non-thermal photon emission ranges from the radio to the very-high-energy (VHE) range and it is believed to be originated in synchrotron, curvature and inverse Compton processes.So far, pulsars and PWNe represent the largest population of identified GeV and TeV sources. In this contribution, we will describe the recent measurements on young PWNe such as the Crab whose inverse Compton peak was recently accurately determined. We will also discuss the origin of the GeV gamma-ray flares and their non-detection at any other wavelength, together with the recent reports of pulsed emission up to TeV energies. This result evidences the extreme acceleration of electrons in the surrounding of the Crab pulsar, up to Lorenz factors of 5 × 106. We will also put in context the recent discovery of VHE pulsed emission from the Vela pulsar. We will discuss the case of the inefficient pulsar at the center of 3C 58, a PWN discovered by Fermi at GeV energies and by MAGIC at TeV. In addition, we will also present population studies comparing several properties of the central engine such as age or spin-down power with the gamma-ray luminosity of their surrounding PWNe. We will finally show the measurement prospects for this kind of sources with the future Cherenkov Telescope Array.

  10. Future GLAST Observations of Supernova Remnants And Pulsar Wind Nebulae

    SciTech Connect

    Funk, S.; /KIPAC, Menlo Park

    2007-09-26

    Shell-type Supernova remnants (SNRs) have long been known to harbour a population of ultra-relativistic particles, accelerated in the Supernova shock wave by the mechanism of diffusive shock acceleration. Experimental evidence for the existence of electrons up to energies of 100 TeV was first provided by the detection of hard X-ray synchrotron emission as e.g. in the shell of the young SNR SN1006. Furthermore using theoretical arguments shell-type Supernova remnants have long been considered as the main accelerator of protons - Cosmic rays - in the Galaxy; definite proof of this process is however still missing. Pulsar Wind Nebulae (PWN) - diffuse structures surrounding young pulsars - are another class of objects known to be a site of particle acceleration in the Galaxy, again through the detection of hard synchrotron X-rays such as in the Crab Nebula. Gamma-rays above 100 MeV provide a direct access to acceleration processes. The GLAST Large Area telescope (LAT) will be operating in the energy range between 30 MeV and 300 GeV and will provide excellent sensitivity, angular and energy resolution in a previously rather poorly explored energy band. We will describe prospects for the investigation of these Galactic particle accelerators with GLAST.

  11. Abrupt acceleration of a 'cold' ultrarelativistic wind from the Crab pulsar.

    PubMed

    Aharonian, F A; Bogovalov, S V; Khangulyan, D

    2012-02-23

    Pulsars are thought to eject electron-positron winds that energize the surrounding environment, with the formation of a pulsar wind nebula. The pulsar wind originates close to the light cylinder, the surface at which the pulsar co-rotation velocity equals the speed of light, and carries away much of the rotational energy lost by the pulsar. Initially the wind is dominated by electromagnetic energy (Poynting flux) but later this is converted to the kinetic energy of bulk motion. It is unclear exactly where this takes place and to what speed the wind is accelerated. Although some preferred models imply a gradual acceleration over the entire distance from the magnetosphere to the point at which the wind terminates, a rapid acceleration close to the light cylinder cannot be excluded. Here we report that the recent observations of pulsed, very high-energy γ-ray emission from the Crab pulsar are explained by the presence of a cold (in the sense of the low energy of the electrons in the frame of the moving plasma) ultrarelativistic wind dominated by kinetic energy. The conversion of the Poynting flux to kinetic energy should take place abruptly in the narrow cylindrical zone of radius between 20 and 50 light-cylinder radii centred on the axis of rotation of the pulsar, and should accelerate the wind to a Lorentz factor of (0.5-1.0) × 10(6). Although the ultrarelativistic nature of the wind does support the general model of pulsars, the requirement of the very high acceleration of the wind in a narrow zone not far from the light cylinder challenges current models. PMID:22343893

  12. Properties of young pulsar wind nebulae: TeV detectability and pulsar properties

    NASA Astrophysics Data System (ADS)

    Tanaka, Shuta J.; Takahara, Fumio

    2013-03-01

    Among dozens of young pulsar wind nebulae (PWNe), some have been detected in TeV γ-rays (TeV PWNe), while others have not (non-TeV PWNe). The TeV emission detectability is not correlated with either the spin-down power or the characteristic age of the central pulsars and it is an open question as to what determines the detectability. To study this problem, we investigate the spectral evolution of five young non-TeV PWNe: 3C 58, G310.6-1.6, G292.0+1.8, G11.2-0.3 and SNR B0540-69.3. We use a spectral evolution model that was developed in our previous works to be applied to young TeV PWNe. The TeV γ-ray flux upper limits of non-TeV PWNe give upper or lower limits on parameters such as the age of the PWN and the fraction of spin-down power going into magnetic energy injection (the fraction parameter). Combined with other independent observational and theoretical studies, we can guess a plausible value of the parameters for each object. For 3C 58, we prefer parameters with an age of 2.5 kyr and fraction parameter of 3.0 × 10-3, although the spectral modelling alone does not rule out a lower age and a higher fraction parameter. The fraction parameter of 3.0 × 10-3 is also consistent for other non-TeV PWNe and thus the value is regarded as common to young PWNe, including TeV PWNe. Moreover, we find that the intrinsic properties of the central pulsars are similar: 1048-50 erg for the initial rotational energy and 1042-44 erg for the magnetic energy (2 × 1012-3 × 1013 G for the dipole magnetic field strength at the surface). The TeV detectability is correlated with the total injected energy and the energy density of the interstellar radiation field around PWNe. Except for the case of G292.0+1.8, broken power-law injection of the particles reproduces the broad-band emission from non-TeV PWNe well.

  13. A corrugated termination shock in pulsar wind nebulae?

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin

    2016-08-01

    > Successful phenomenological models of pulsar wind nebulae assume efficient dissipation of the Poynting flux of the magnetized electron-positron wind as well as efficient acceleration of the pairs in the vicinity of the termination shock, but how this is realized is not yet well understood. This paper suggests that the corrugation of the termination shock, at the onset of nonlinearity, may lead towards the desired phenomenology. Nonlinear corrugation of the termination shock would convert a fraction of order unity of the incoming ordered magnetic field into downstream turbulence, slowing down the flow to sub-relativistic velocities. The dissipation of turbulence would further preheat the pair population on short length scales, close to equipartition with the magnetic field, thereby reducing the initial high magnetization to values of order unity. Furthermore, it is speculated that the turbulence generated by the corrugation pattern may sustain a relativistic Fermi process, accelerating particles close to the radiation reaction limit, as observed in the Crab nebula. The required corrugation could be induced by the fast magnetosonic modes of downstream nebular turbulence; but it could also be produced by upstream turbulence, either carried by the wind or seeded in the precursor by the accelerated particles themselves.

  14. SPATIALLY RESOLVED SPECTROSCOPY OF A PULSAR WIND NEBULA IN MSH 15-56

    SciTech Connect

    Yatsu, Yoichi; Kawai, Nobuyuki; Yano, Yuki; Asano, Katsuaki; Nakamori, Takeshi

    2013-08-10

    We report the study of a pulsar wind nebula (PWN) in the middle-aged supernova remnant (SNR) MSH 15-56. High-resolution X-ray imaging observations using XMM-Newton and Chandra provided clear images of its comet-like structure, as seen in other PWNe moving rapidly through interstellar mediums. At the PWN apex, Chandra detected a point source emitting a power-law spectrum with a photon index of {Gamma} = 1.3. The photon index of the PWN steepens from 1.7 to 2.5 along the flow line from the apex toward the tail, implying that the PWN is powered by the point source. The opening angle of the tail implies a pulsar velocity of v{sub PSR} = 1900 km s{sup -1}. We also discovered a thin X-ray filament at the edge of the SNR and just near the PWN. Assuming that the SNR is in the Sedov phase, the shell is expanding at 860 km s{sup -1}, which is consistent with the existence of the non-thermal filament. Based on the physical relationship, the PWN will run through the blast wave in the near future.

  15. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    NASA Astrophysics Data System (ADS)

    Swartz, Douglas A.; Weisskopf, M. C.; Zavlin, V.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; van der Horst, A.; Yukita, M.

    2013-04-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXO J061705.3+222127, in the supernova remnant IC443 confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by a pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The observations further reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic; there is no evidence for a strong bow shock and the ring, presumably formed at a wind termination shock, is not distorted by motion through the ambient medium.

  16. X-ray observations of PSR B0355+54 and its pulsar wind nebula

    NASA Astrophysics Data System (ADS)

    McGowan, Katherine E.; Vestrand, W. Thomas; Kennea, Jamie A.; Zane, Silvia; Cropper, Mark; Córdova, France A.

    2007-04-01

    We present X-ray data of the middle-aged radio pulsar PSR B0355+54. The XMM-Newton and Chandra observations show not only emission from the pulsar itself, but also compact diffuse emission extending ˜50″ in the opposite direction to the pulsar’s proper motion. Our analysis also indicates the presence of fainter diffuse emission extending ˜5‧ from the point source. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. We find that the compact diffuse component is well-fitted with a power-law, with an index that is consistent with the values found for other pulsar wind nebulae. The core emission from the pulsar can be characterized with a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.

  17. Pulsar Animation

    NASA Video Gallery

    Pulsars are thought to emit relatively narrow radio beams, shown as green in this animation. If these beams don't sweep toward Earth, astronomers cannot detect the radio signals. Pulsar gamma-ray e...

  18. Suzaku Observations of PSR B1259-63: A New Manifestation of Relativistic Pulsar Wind

    SciTech Connect

    Uchiyama, Yasunobu; Tanaka, Takaaki; Takahashi, Tadayuki; Mori, Koji; Nakazawa, Kazuhiro

    2009-04-27

    We observed PSR B1259-63, a young non-accreting pulsar orbiting around a Be star SS 2883, eight times with the Suzaku satellite from July to September 2007, to characterize the X-ray emission arising from the interaction between a pulsar relativistic wind and Be star outflows. The X-ray spectra showed a featureless continuum in 0.6-10 keV, modeled by a power law with a wide range of photon index 1.3-1.8. When combined with the Suzaku PIN detector which allowed spectral analysis in the hard 15-50 keV band, X-ray spectra do show a break at {approx} 5 keV in a certain epoch. Regarding the PSR B1259-63 system as a compactified pulsar wind nebula, in which e{sup {+-}} pairs are assumed to be accelerated at the inner shock front of the pulsar wind, we attribute the X-ray spectral break to the low-energy cutoff of the synchrotron radiation associated with the Lorentz factor of the relativistic pulsar wind {gamma}{sub 1} {approx} 4 x 10{sup 5}. Our result indicates that Comptonization of stellar photons by the unshocked pulsar wind will be accessible (or tightly constrained) by observations with the Fermi Gamma-ray Space Telescope during the next periastron passage. The PSR B1259-63 system allows us to probe the fundamental properties of the pulsar wind by a direct means, being complementary to the study of large-scale pulsar wind nebulae.

  19. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    NASA Technical Reports Server (NTRS)

    Swartz, D. A.; Weisskopf, M. C.; Zavlin, V. E.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; O'Dell, S. L.; vanderHorst, A J.; Yukita, M.

    2013-01-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222117, in the supernova remnant IC443 reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by the pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest (or, equivalently, flow of ambient medium to the northeast), appears to be subsonic; there is no evidence for a strong bow shock, and the circular ring is not distorted by motion through the ambient medium.

  20. Simulations of stellar/pulsar-wind interaction along one full orbit

    NASA Astrophysics Data System (ADS)

    Bosch-Ramon, V.; Barkov, M. V.; Khangulyan, D.; Perucho, M.

    2012-08-01

    Context. The winds from a non-accreting pulsar and a massive star in a binary system collide forming a bow-shaped shock structure. The Coriolis force induced by orbital motion deflects the shocked flows, strongly affecting their dynamics. Aims: We study the evolution of the shocked stellar and pulsar winds on scales in which the orbital motion is important. Potential sites of non-thermal activity are investigated. Methods: Relativistic hydrodynamical simulations in two dimensions, performed with the code PLUTO and using the adaptive mesh refinement technique, are used to model interacting stellar and pulsar winds on scales ~80 times the distance between the stars. The hydrodynamical results suggest the suitable locations of sites for particle acceleration and non-thermal emission. Results: In addition to the shock formed towards the star, the shocked and unshocked components of the pulsar wind flowing away from the star terminate by means of additional strong shocks produced by the orbital motion. Strong instabilities lead to the development of turbulence and an effective two-wind mixing in both the leading and trailing sides of the interaction structure, which starts to merge with itself after one orbit. The adopted moderate pulsar-wind Lorentz factor already provides a good qualitative description of the phenomena involved in high-mass binaries with pulsars, and can capture important physical effects that would not appear in non-relativistic treatments. Conclusions: Simulations show that shocks, instabilities, and mass-loading yield efficient mass, momentum, and energy exchanges between the pulsar and the stellar winds. This renders a rapid increase in the entropy of the shocked structure, which will likely be disrupted on scales beyond the simulated ones. Several sites of particle acceleration and low- and high-energy emission can be identified. Doppler boosting will have significant and complex effects on radiation. A movie of the simulation is available in

  1. On ultra-high energy cosmic ray acceleration at the termination shock of young pulsar winds

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin; Kotera, Kumiko; Pétri, Jérôme

    2015-07-01

    Pulsar wind nebulae (PWNe) are outstanding accelerators in Nature, in the sense that they accelerate electrons up to the radiation reaction limit. Motivated by this observation, this paper examines the possibility that young pulsar wind nebulae can accelerate ions to ultra-high energies at the termination shock of the pulsar wind. We consider here powerful PWNe, fed by pulsars born with ~ millisecond periods. Assuming that such pulsars exist, at least during a few years after the birth of the neutron star, and that they inject ions into the wind, we find that protons could be accelerated up to energies of the order of the Greisen-Zatsepin-Kuzmin cut-off, for a fiducial rotation period P ~ 1 msec and a pulsar magnetic field Bstar ~ 1013 G, implying a fiducial wind luminosity Lp ~ 1045 erg/s and a spin-down time tsd ~ 3× 107 s. The main limiting factor is set by synchrotron losses in the nebula and by the size of the termination shock; ions with Z>= 1 may therefore be accelerated to even higher energies. We derive an associated neutrino flux produced by interactions in the source region. For a proton-dominated composition, our maximum flux lies slightly below the 5-year sensitivity of IceCube-86 and above the 3-year sensitivity of the projected Askaryan Radio Array. It might thus become detectable in the next decade, depending on the exact level of contribution of these millisecond pulsar wind nebulae to the ultra-high energy cosmic ray flux.

  2. THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

    SciTech Connect

    Zabalza, V.; Paredes, J. M.; Bosch-Ramon, V.

    2011-12-10

    Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

  3. Formation of the dark bays in the Crab optical synchrotron nebula - Is the Crab pulsar wind bubble interacting with its progenitor's wind?

    NASA Technical Reports Server (NTRS)

    Li, Zhi-Yun; Begelman, Mitchell C.

    1992-01-01

    Models are presented for the formation of the two dark bays in the Crab optical synchrotron nebula, from which the optical synchrotron-emitting particles seem to be excluded. It is proposed that the bays are formed by the advance of the Crab pulsar's wind bubble into an ambient medium possessing a stratified density distribution with higher density in the plane of the bays than in other directions. The ambient density and degree of stratification required to produce the bays depends on whether the medium consists of a general interstellar medium, a progenitor stellar wind, or fast-moving supernova ejecta. In the case of an interstellar medium, the bays would be expected to move apart much more slowly than observed, and the required density would have to be implausibly high. It is concluded that the pulsar wind bubble is probably interacting with the slow wind from its progenitor, and it is shown that bays formed in this way agree with the observations reasonably well.

  4. Detection of gamma-ray emission from the Vela pulsar wind nebula with AGILE.

    PubMed

    Pellizzoni, A; Trois, A; Tavani, M; Pilia, M; Giuliani, A; Pucella, G; Esposito, P; Sabatini, S; Piano, G; Argan, A; Barbiellini, G; Bulgarelli, A; Burgay, M; Caraveo, P; Cattaneo, P W; Chen, A W; Cocco, V; Contessi, T; Costa, E; D'Ammando, F; Del Monte, E; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Fuschino, F; Galli, M; Gianotti, F; Hotan, A; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Marisaldi, M; Mastropietro, M; Mereghetti, S; Moretti, E; Morselli, A; Pacciani, L; Palfreyman, J; Perotti, F; Picozza, P; Pittori, C; Possenti, A; Prest, M; Rapisarda, M; Rappoldi, A; Rossi, E; Rubini, A; Santolamazza, P; Scalise, E; Soffitta, P; Striani, E; Trifoglio, M; Vallazza, E; Vercellone, S; Verrecchia, F; Vittorini, V; Zambra, A; Zanello, D; Giommi, P; Colafrancesco, S; Antonelli, A; Salotti, L; D'Amico, N; Bignami, G F

    2010-02-01

    Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources. PMID:20044540

  5. ENHANCED DISSIPATION RATE OF MAGNETIC FIELD IN STRIPED PULSAR WINDS BY THE EFFECT OF TURBULENCE

    SciTech Connect

    Takamoto, Makoto; Inoue, Tsuyoshi; Inutsuka, Shu-ichiro E-mail: inouety@phys.aoyama.ac.jp

    2012-08-10

    In this paper, we report on turbulent acceleration of the dissipation of the magnetic field in the post-shock region of a Poynting flux-dominated flow, such as the Crab pulsar wind nebula. We have performed two-dimensional resistive relativistic magnetohydrodynamics simulations of subsonic turbulence driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting flux-dominated flows in pulsar winds. We find that turbulence stretches current sheets which substantially enhances the dissipation of the magnetic field, and that most of the initial magnetic field energy is dissipated within a few eddy-turnover times. We also develop a simple analytical model for turbulent dissipation of the magnetic field that agrees well with our simulations. The analytical model indicates that the dissipation rate does not depend on resistivity even in the small resistivity limit. Our findings can possibly alleviate the {sigma}-problem in the Crab pulsar wind nebulae.

  6. TIME-DEPENDENT MODELING OF PULSAR WIND NEBULAE

    SciTech Connect

    Vorster, M. J.; Ferreira, S. E. S.; Tibolla, O.; Kaufmann, S. E-mail: omar.tibolla@gmail.com

    2013-08-20

    A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum of electrons injected at the termination shock of the PWN is chosen to be a broken power law. In contrast to previous PWN models of a similar nature, the source spectrum has a discontinuity in intensity at the transition between the low- and high-energy components. To test the model, it is applied to the young PWN G21.5-0.9, where it is found that a discontinuous source spectrum can model the emission at all wavelengths better than a continuous one. The model is also applied to the unidentified sources HESS J1427-608 and HESS J1507-622. Parameters are derived for these two candidate nebulae that are consistent with the values predicted for other PWNe. For HESS J1427-608, a present day magnetic field of B{sub age} = 0.4 {mu}G is derived. As a result of the small present day magnetic field, this source has a low synchrotron luminosity, while remaining bright at GeV/TeV energies. It is therefore possible to interpret HESS J1427-608 within the ancient PWN scenario. For the second candidate PWN HESS J1507-622, a present day magnetic field of B{sub age} = 1.7 {mu}G is derived. Furthermore, for this candidate PWN a scenario is favored in the present paper in which HESS J1507-622 has been compressed by the reverse shock of the supernova remnant.

  7. Time-dependent Modeling of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Vorster, M. J.; Tibolla, O.; Ferreira, S. E. S.; Kaufmann, S.

    2013-08-01

    A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum of electrons injected at the termination shock of the PWN is chosen to be a broken power law. In contrast to previous PWN models of a similar nature, the source spectrum has a discontinuity in intensity at the transition between the low- and high-energy components. To test the model, it is applied to the young PWN G21.5-0.9, where it is found that a discontinuous source spectrum can model the emission at all wavelengths better than a continuous one. The model is also applied to the unidentified sources HESS J1427-608 and HESS J1507-622. Parameters are derived for these two candidate nebulae that are consistent with the values predicted for other PWNe. For HESS J1427-608, a present day magnetic field of B age = 0.4 μG is derived. As a result of the small present day magnetic field, this source has a low synchrotron luminosity, while remaining bright at GeV/TeV energies. It is therefore possible to interpret HESS J1427-608 within the ancient PWN scenario. For the second candidate PWN HESS J1507-622, a present day magnetic field of B age = 1.7 μG is derived. Furthermore, for this candidate PWN a scenario is favored in the present paper in which HESS J1507-622 has been compressed by the reverse shock of the supernova remnant.

  8. The dynamics of Bow-shock Pulsar Wind Nebula: Reconstruction of multi-bubbles

    NASA Astrophysics Data System (ADS)

    Yoon, Doosoo; Heinz, Sebastian

    2014-08-01

    Bow-shock pulsar wind nebulae (PWNe) exhibit a characteristic cometary shape due to the supersonic motion of the pulsar interacting with the interstellar medium (ISM). One of the spectacular bow-shock is the Guitar Nebula, which is produced by the fast pulsar PSR B2224+65 (vpsr > 1000 km s-1 ), and consists of a bright head, a faint neck, a two larger bubbles. We present that the peculiar mophology arises from variations in the interstellar medium density. We perform 3-D hydrodynamic simulation to understand the evolution of the pulsar as its moves through the density discontinuity. We found that when the pulsar encounters the low-density medium, the pressure balance at the head of the bow shock begins to collapse, producing the second bubble. The expansion rate of the bubble is related to the properties of both the pulsar and the ambient medium. Assuming that the pulsar’s properties, including spin-down energy, are constant, we conclude that the ambient density around the second bubble should be 4.46 times larger than around the first bubble in the Guitar body. We further found that when the pulsar encounters the inclined density dicontinuity, it can produce the asymmetric shape of the bow shock observed in a subset of bow-shock PWNe including J2124-3358.

  9. Fermi-LAT Constraints on the Pulsar Wind Nebula Nature of HESS J1857+026

    NASA Technical Reports Server (NTRS)

    Rousseau, R.; Grondin, M.-H.; VanEtten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; Espinoza, C. M.; Johnston, S.; Lyne, A. G.; Smith, D. A.; Stappers, B. W.; Caliandro, G. A.

    2012-01-01

    Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857+026 is a spatially extended gamma-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856+0245. Aims. We search for -ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase.fold 36 months of gamma-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete gamma-ray spectral and morphological analysis. Results. No pulsation was detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857+026. The gamma-ray spectrum is well described by a simple power law with a spectral index of Gamma = 1.53 +/- 0.11(sub stat) +/- 0.55(sub syst) and an energy flux of G(0.1 C100 GeV) = (2.71 +/- 0.52(sub stat) +/- 1.51(sub syst) X 10(exp -11) ergs/ sq cm/s. This implies a gamma.ray efficiency of approx 5 %, assuming a distance of 9 kpc, the gamma-ray luminosity of L(sub gamma) (sub PWN) (0.1 C100 GeV) = (2.5 +/- 0.5(sub stat) +/- 1.5(sub syst)) X 10(exp 35)(d/(9kpc))(exp 2) ergs/s and E-dot = 4.6 X 10(exp 36) erg /s, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

  10. Fermi-LAT constraints on the pulsar wind nebula nature of HESS J1857+026

    NASA Astrophysics Data System (ADS)

    Rousseau, R.; Grondin, M.-H.; Van Etten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; Espinoza, C. M.; Johnston, S.; Lyne, A. G.; Smith, D. A.; Stappers, B. W.; Caliandro, G. A.

    2012-08-01

    Context. Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Aims: We search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods: Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. Results: No γ-ray pulsations were detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11stat ± 0.55syst and an energy flux of G(0.1-100 GeV) = (2.71 ± 0.52stat ± 1.51syst) × 10-11 erg cm-2 s-1. The γ-ray luminosity is LPWNγ (0.1-100 GeV)=(2.5 ± 0.5stat ± 1.5syst) × 1035 (d/9 kpc)2 erg s-1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% for Ė = 4.6 × 1036 erg s-1, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

  11. Suzaku observations of the old pulsar wind nebula candidate HESS J1356-645

    NASA Astrophysics Data System (ADS)

    Izawa, Masaharu; Dotani, Tadayasu; Fujinaga, Takahisa; Bamba, Aya; Ozaki, Masanobu; Hiraga, Junko S.

    2015-06-01

    A largely extended X-ray emission was discovered around the pulsar PSR J1357-6429 with the Suzaku deep observations. The pulsar, whose characteristic age is 7.3 kyr, is located within the TeV γ-ray source HESS J1356-645. The extended emission is found to have a 1 σ X-ray size of ˜ 4', or ˜ 3 pc at 2.4 kpc, with a small offset from the pulsar. Its X-ray spectrum is well reproduced by a simple power-law model with a photon index of 1.70_{-0.06}^{+0.07}. No significant spatial variation was found for the X-ray photon index as a function of distance from the pulsar. We conclude that the extended emission is associated to the pulsar wind nebula (PWN) of PSR J1357-6429. This is a new sample of largely extended nebulae around middle-aged pulsars. We discuss the evolution of this PWN according to the relic PWN scenario.

  12. X-Ray Spectra of Young Pulsars and Their Wind Nebulae: Dependence on Spin-Down Energy Loss Rate

    NASA Technical Reports Server (NTRS)

    Gotthelf, E. V.

    2003-01-01

    An observational model is presented for the spectra of young rotation-powered pulsars and their nebulae based on a study of nine bright Crab-like pulsar systems observed with the Chandra X-ray observatory. A significant correlation is discovered between the X-ray spectra of these pulsars and that of their associated pulsar wind nebulae, both of which are observed to be a function of the spin-down energy loss rate, E. The 2-10 keV spectra of these objects are well characterized by an absorbed power-law model with photon indices, Gamma, in the range of 0.6 < Gamma (sub PSR) < 2.1 and 1.3 < Gamma(sub PWN) < 2.3, for the pulsars and their nebulae, respectively. A linear regression fit relating these two sets of indexes yields Gamma(sub PWN) = 0.91 +/- 0.18 + (0.66 +/- 0.11) Gamma (sub PSR), with a correlation coefficient of r = 0.97. The spectra of these pulsars are found to steepen as Gamma = Gamma(sub max) + alpha E (exp -1/2), with Gamma(sub max) providing an observational limit on the spectral slopes of young rotation-powered pulsars. These results reveal basic properties of young pulsar systems, allow new observational constraints on models of pulsar wind emission, and provide a means of predicting the energetics of pulsars lacking detected pulsations.

  13. Theoretical Study of Compact Objects: Pulsars, Thermally Emitting Neutron Stars and Magnetars

    NASA Astrophysics Data System (ADS)

    Lai, Dong

    This proposal focuses on understanding the various observational manifestations of magnetized neutron stars (NSs), including pulsars, radio-quiet thermally emitting NSs and magnetars. This is motivated by the recent and ongoing observational progress in the study of isolated NSs, made possible by space telescopes such as Chandra and XMM-Newton, and the prospect of near-future observations by NASA's Gravity and Extreme Magnetism SMEX (GEMS) mission (to be launched in 2014). Recent observations have raised a number of puzzles/questions that beg for theoretical understanding and modeling. The proposed research projects are grouped into two parts: (1) Theoretical modeling of surface (or near surface) X-ray emission from magnetized NSs, including the study of the physics of electron/ion cyclotron lines, radiative transfer during magnetar bursts, dense plasma refractive effect, partially ionized atmospheres, and calculations of X-ray polarization signatures of isolated and accreting magnetic NSs, in anticipation of their detections by GEMS. (2) Theoretical study and observational constraint on the internal structure and evolution of magnetic fields in young neutron stars in supernova remnants. The proposed research will improve our understanding of different populations of NSs and their underlying physical processes (including the extreme physics of strong-field quantum electrodynamics) and enhance the scientific return from the current and future NASA astrophysics missions. It is relevant to NASA's objective, ``Discover the origin, structure, evolution, and destiny of the universe''.

  14. Pulsar Wind Nebulae, Space Velocities and Supernova Remnant Associations

    NASA Technical Reports Server (NTRS)

    2002-01-01

    I am pleased to be able to report significant progress in my research relevant to my LTSA grant. This progress I believe is demonstrated by a long list of publications in 2002, as detailed below. I summarize the research results my collaborators and I obtained in 2002. First, my group announced the major discovery of soft-gamma-repeater-like X-ray bursts from the anomalous X-ray pulsars lE-1048.1$-$5937 and lE-2259+586, using the Rossi X-ray Timing Explorer. This result provides an elegant and long-sought-after confirmation that this class of objects and the soft gamma repeaters share a common nature, namely that they are magnetars. Magnetars are a novel manifestation of young neutron stars, quite different from conventional Crab-like radio pulsars. This discovery was made as part of our regular monitoring program, among the goals of which was to detect such outbursts.

  15. Very high energy emission as a probe of relativistic magnetic reconnection in pulsar winds

    NASA Astrophysics Data System (ADS)

    Mochol, Iwona; Pétri, Jérôme

    2015-04-01

    The population of gamma-ray pulsars, including Crab observed in the TeV range, and Vela detected above 50 GeV, challenges existing models of pulsed high-energy emission. Such models should be universally applicable, yet they should account for spectral differences among the pulsars. We show that the gamma-ray emission of Crab and Vela can be explained by synchrotron radiation from the current sheet of a striped wind, expanding with a modest Lorentz factor Γ ≲ 100 in the Crab case, and Γ ≲ 50 in the Vela case. In the Crab spectrum, a new synchrotron self-Compton component is expected to be detected by the upcoming experiment CTA. We suggest that the gamma-ray spectrum directly probes the physics of relativistic magnetic reconnection in the striped wind. In the most energetic pulsars, like Crab, with dot{E}_{38}^{3/2}/P_{-2}≳ 0.002 (where dot{E} is the spin-down power, P is the pulsar period, and X = Xi × 10i in CGS units), reconnection proceeds in the radiative cooling regime and results in a soft power-law distribution of cooling particles; in less powerful pulsars, like Vela, particle energization is limited by the current sheet size, and a hard particle spectrum reflects the acceleration mechanism. A strict lower limit on the number density of radiating particles corresponds to emission close to the light cylinder, and, in units of the GJ density, it is ≳ 0.5 in the Crab wind, and κ ≳ 0.05 in the Vela wind.

  16. RADIATIVE DAMPING AND EMISSION SIGNATURES OF STRONG SUPERLUMINAL WAVES IN PULSAR WINDS

    SciTech Connect

    Mochol, Iwona; Kirk, John G. E-mail: john.kirk@mpi-hd.mpg.de

    2013-10-10

    We analyze the damping of strong, superluminal electromagnetic waves by radiation reaction and Compton drag in the context of pulsar winds. The associated radiation signature is found by estimating the efficiency and the characteristic radiation frequencies. Applying these estimates to the gamma-ray binary containing PSR B1259–63, we show that the GeV flare observed by the Fermi Large Area Telescope can be understood as inverse-Compton emission by particles scattering photons from the companion star, if the pulsar wind termination shock acquires a precursor of superluminal waves roughly 30 days after periastron. This requirement constrains the mass-loading factor of the wind μ=L/ N-dot mc{sup 2}, where L is the luminosity and N-dot is the rate of loss of electrons and positrons, to be roughly 6 × 10{sup 4}.

  17. A Chandra Search for a Pulsar Wind Nebula around PSR B1055-52

    NASA Astrophysics Data System (ADS)

    Posselt, B.; Spence, G.; Pavlov, G. G.

    2015-10-01

    The nearby, middle-aged PSR B1055-52 has many properties in common with the Geminga pulsar. Motivated by the Geminga's enigmatic and prominent pulsar wind nebula (PWN), we searched for extended emission around PSR B1055-52 with Chandra ACIS. For an energy range 0.3-1 keV, we found a 4σ flux enhancement in a 4\\buildrel{\\prime\\prime}\\over{.} 9-20\\prime\\prime annulus around the pulsar. There is a slight asymmetry in the emission close, 1\\buildrel{\\prime\\prime}\\over{.} 5-4\\prime\\prime , to the pulsar. The excess emission has a luminosity of about 1029 erg s-1 in an energy range 0.3-8 keV for a distance of 350 pc. Overall, the faint extended emission around \\text{PSR B1055-52} is consistent with a PWN of an aligned rotator moving away from us along the line of sight with supersonic velocity, but a contribution from a dust scattering halo cannot be excluded. Comparing the properties of other nearby, middle-aged pulsars, we suggest that the geometry—the orientations of rotation axis, magnetic field axis, and the sight-line—is the deciding factor for a pulsar to show a prominent PWN. We also report on an ≳ 30% flux decrease of PSR B1055-52 between the 2000 XMM-Newton and our 2012 Chandra observation. We tentatively attribute this flux decrease to a cross-calibration problem, but further investigations of the pulsar are required to exclude actual intrinsic flux changes.

  18. High Spatial Resolution X-Ray Spectroscopy of the IC443 Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Swartz, Douglas A.; Weisskopf, Martin C.; Bucciantini, Niccolo; Clarke, Tracy E.; Karovska, Margarita; Pavlov, George G.; van der Horst, Alexander; Yukita, Mihoko; Zavlin, Vyacheslav

    2014-08-01

    Deep Chandra ACIS observations of the region around the putative pulsar CXOU J061705.3+222127, in the supernova remnant IC443, reveal a ~5" radius ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar's location. The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar, (2) the non-thermal spectrum and morphology of the surrounding nebula are consistent with a pulsar wind, and (3) the spectrum at greater distances is consistent with thermal emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic: There is no evidence for a strong bow shock; and the ring is not distorted by motion through the ambient medium. Comparing this observation with historical observations of the same target we set a 99-% confidence upper limit to the proper motion of CXOU J061705.3+222127 to be less than 310 km/s, with the best-fit (but not statistically significant) direction toward the west.

  19. High Spatial Resolution X-Ray Spectroscopy of the IC 443 Pulsar Wind Nebula and Environs

    NASA Astrophysics Data System (ADS)

    Swartz, Douglas A.; Pavlov, George G.; Clarke, Tracy; Castelletti, Gabriela; Zavlin, Vyacheslav E.; Bucciantini, Niccolò; Karovska, Margarita; van der Horst, Alexander J.; Yukita, Mihoko; Weisskopf, Martin C.

    2015-07-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222127, in the supernova remnant (SNR) IC 443 reveal an ∼5″ radius ring-like structure surrounding the pulsar and a jet-like feature oriented roughly north–south across the ring and through the pulsar's location at 06h17m5.ˢ200 + 22°21‧27.″52 (J2000.0 coordinates). The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar, (2) the non-thermal spectrum and morphology of the surrounding nebula are consistent with a pulsar wind, and (3) the spectrum at greater distances is consistent with thermal emission from the SNR. The cometary shape of the nebula, suggesting motion toward the southwest, appears to be subsonic: There is no evidence either spectrally or morphologically for a bow shock or contact discontinuity; the nearly circular ring is not distorted by motion through the ambient medium; and the shape near the apex of the nebula is narrow. Comparing this observation with previous observations of the same target, we set a 99% confidence upper limit to the proper motion of CXOU J061705.3+222127 to be less than 44 mas yr‑1 (310 km s‑1 for a distance of 1.5 kpc), with the best-fit (but not statistically significant) projected direction toward the west.

  20. CIRCULAR POLARIZATION OF PULSAR WIND NEBULAE AND THE COSMIC-RAY POSITRON EXCESS

    SciTech Connect

    Linden, Tim

    2015-02-01

    Recent observations by the PAMELA and AMS-02 telescopes have uncovered an anomalous rise in the positron fraction at energies above 10 GeV. One possible explanation for this excess is the production of primary electron/positron pairs through electromagnetic cascades in pulsar magnetospheres. This process results in a high multiplicity of electron/positron pairs within the wind-termination shock of pulsar wind nebulae (PWNe). A consequence of this scenario is that no circular polarization should be observed within PWNe, since the contributions from electrons and positrons exactly cancel. Here we note that current radio instruments are capable of setting meaningful limits on the circular polarization of synchrotron radiation in PWNe, which observationally test the model for pulsar production of the local positron excess. The observation of a PWN with detectable circular polarization would cast strong doubt on pulsar interpretations of the positron excess, while observations setting strong limits on the circular polarization of PWNe would lend credence to these models. Finally, we indicate which PWNe are likely to provide the best targets for observational tests of the AMS-02 excess.

  1. The Crab pulsar and its pulsar-wind nebula in the optical and infrared

    NASA Astrophysics Data System (ADS)

    Tziamtzis, A.; Lundqvist, P.; Djupvik, A. A.

    2009-12-01

    Aims. We investigate the emission mechanism and evolution of pulsars that are associated with supernova remnants. Methods: We used imaging techniques in both the optical and near infrared, using images with very good seeing (≤0.primeprime6) to study the immediate surroundings of the Crab pulsar. In the case of the infrared, we took two data sets with a time window of 75 days to check for variability in the inner part of the Crab nebula. We also measure the spectral indices of all these wisps, the nearby knot, and the interwisp medium, using our optical and infrared data. We then compared the observational results with the existing theoretical models. Results: We report variability in the three nearby wisps located to the northwest of the pulsar and also in a nearby anvil wisp in terms of their structure, position, and emissivity within the time window of 75 days. All the wisps display red spectra with similar spectral indices (α_ν = -0.58 ± 0.08, α_ν = -0.63 ± 0.07, α_ν = -0.53 ± 0.08) for the northwest triplet. The anvil wisp (anvil wisp 1) has a spectral index of α_ν = -0.62 ± 0.10. Similarly, the interwisp medium regions also show red spectra similar to those of the wisps, with the spectral index being α_ν = -0.61 ± 0.08, α_ν = -0.50 ± 0.10, while the third interwisp region has a flatter spectrum with spectral α_ν = -0.49 ± 0.10. The inner knot has a spectral index of α_ν = -0.63 ± 0.02. Also, based on archival HST data and our IR data, we find that the inner knot remains stationary for a time period of 13.5 years. The projected average velocity relative to the pulsar for this period is ≲8 ~km s-1. Conclusions: By comparing the spectral indices of the structures in the inner Crab with the current theoretical models, we find that the Del Zanna et al. model for the synchrotron emission fits our observations, although the spectral index is at the flatter end of their modelled spectra. Based on observations made with the Nordic Optical

  2. Structure of relativistic shocks in pulsar winds: A model of the wisps in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Gallant, Yves A.; Arons, Jonathan

    1994-01-01

    We propose a model of a optical 'wisps' of the Crab Nebula, features observed in the nebular synchrotron surface brightness near the central pulsar, as manifestations of the internal structure of the shock terminating the pulsar wind. We assume that this wind is composed of ions and a much denser plasma of electrons and positrons, frozen together to a toroidal magnetic field and flowing relativistically. We construct a form of solitary wave model of the shock structure in which we self-consistently solve for the ion orbits and the dynamics of the relativistically hot, magnetized e(+/-) background flow. We ignore dispersion in the ion energies, and we treat the pairs as an adiabatic fluid. The synchrotron emission enhancements, observed as the wisps, are then explained as the regions where reflection of the ions in the self-consistent magnetic field causes compressions of the e(+/-).

  3. MULTI-ZONE MODELING OF THE PULSAR WIND NEBULA HESS J1825-137

    SciTech Connect

    Van Etten, Adam; Romani, Roger W.

    2011-12-01

    The pulsar wind nebula associated with PSR J1826-1334, HESS J1825-137, is a bright very high energy (VHE) source with an angular extent of {approx}1 Degree-Sign and spatially resolved spectroscopic TeV measurements. The gamma-ray spectral index is observed to soften with increasing distance from the pulsar, likely the result of cooling losses as electrons traverse the nebula. We describe analysis of X-ray data of the extended nebula, as well as three-dimensional time-dependent spectral energy distribution modeling, with emphasis on the spatial variations within HESS J1825-137. The multi-wavelength data place significant constraints on electron injection, transport, and cooling within the nebula. The large size and high nebular energy budget imply a relatively rapid initial pulsar spin period of 13 {+-} 7 ms and an age of 40 {+-} 9 kyr. The relative fluxes of each VHE zone can be explained by advective particle transport with a radially decreasing velocity profile with v(r){proportional_to}r{sup -0.5}. The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar, B(r,t){proportional_to}r{sup -0.7} E-dot (t){sup 1/2}. Detection of 10 TeV flux {approx}80 pc from the pulsar requires rapid diffusion of high-energy particles, contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement. The model predicts a rather uniform Fermi Large Area Telescope (LAT) surface brightness out to {approx}1 Degree-Sign from the pulsar, in good agreement with the recently discovered LAT source centered 0.{sup 0}5 southwest of PSR J1826-1334 with extension 0.{sup 0}6 {+-} 0.{sup 0}1.

  4. Multi-Zone Modeling of Nonthermal Radiation from Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Van Etten, Adam; Romani, R. W.

    2012-01-01

    Many pulsar wind nebulae (PWN) are spatially resolved in the radio, X-ray, and even very high energy (VHE) wavebands, and thereby provide an excellent laboratory to study not only pulsar winds and dynamics, but also shock processes, the ambient medium, magnetic feld evolution, and particle transport. Single-zone spectral energy distribution (SED) models have long been used to study the global properties of PWN, but to fully take advantage of high resolution data one must move beyond these simple models. I describe 3-D time-dependent PWN spectral energy distribution modeling, with particular emphasis on the spatial variations within the large and bright PWN associated with PSR J1826-1334, HESS J1825-137. Within this PWN, the gamma-ray spectral index is observed to soften with increasing distance from the pulsar, likely the result of cooling losses as electrons traverse the nebula. The large size and high nebular energy budget imply a relatively rapid initial pulsar spin period of 13±7 ms and an age of 40±9 kyr. The relative fluxes of each VHE zone can be explained by advective particle transport with a radially decreasing velocity profile with v(r) r(-0.5). The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar, B(r,t) r(-0.7)Edot(t)(0.5). Detection of 10 TeV flux 80 pc from the pulsar requires rapid diffusion of high energy particles with κesc≈90(R/10 pc)2(E/100 TeV)(-1)year, contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement. The model predicts a rather uniform Fermi LAT surface brightness out to 1 degree from the pulsar, in good agreement with the recently discovered LAT source centered 0.5 degree southwest of PSR J1826-1334 with extension 0.6±0.1 degree. The growing number of sources with spatially resolved X-ray and VHE measurements (e.g. Vela-X, HESS J1303-631) are prime targets for such multi-zone modeling.

  5. Numerical simulations of composite supernova remnants for small σ pulsar wind nebulae

    NASA Astrophysics Data System (ADS)

    Vorster, M. J.; Ferreira, S. E. S.; de Jager, O. C.; Djannati-Ataï, A.

    2013-03-01

    Context. Composite supernova remnants consist of a pulsar wind nebula located inside a shell-type remnant. The presence of a shell has implications on the evolution of the nebula, although the converse is generally not true. Aims: The purpose of this paper is two-fold. The first aim is to determine the effect of the pulsar's initial luminosity and spin-down rate, the supernova ejecta mass, and density of the interstellar medium on the evolution of a spherically-symmetric, composite supernova remnant expanding into a homogeneous medium. The second aim is to investigate the evolution of the magnetic field in the pulsar wind nebula when the the composite remnant expands into a non-uniform interstellar medium. Methods: The Euler conservation equations for inviscid flow, together with the magnetohydrodynamic induction law in the kinematic limit, are solved numerically for a number of scenarios where the ratio of magnetic to particle energy is σ < 0.01. The simulations in the first part of the paper is solved in a one-dimensional configuration. In the second part of the paper, the effect of an inhomogeneous medium on the evolution is studied using a two-dimensional, axisymmetric configuration. Results: It is found that the initial spin-down luminosity and density of the interstellar medium has the largest influence on the evolution of the pulsar wind nebula. The spin-down time-scale of the pulsar only becomes important when this value is smaller than the time needed for the reverse shock of the shell remnant to reach the outer boundary of the nebula. For a remnant evolving in a non-uniform medium, the magnetic field along the boundary of the nebula will evolve to a value that is larger than the magnetic field in the interior. If the inhomogeneity of the interstellar medium is enhanced, while the spin-down luminosity is decreased, it is further found that a magnetic "cloud" is formed in a region that is spatially separated from the position of the pulsar.

  6. The Pulsar Wind Nebula of G11.2-0.3

    NASA Astrophysics Data System (ADS)

    Roberts, M. S. E.; Tam, C.; Kaspi, V. M.; Lyutikov, M.; Gotthelf, E. V.; Vasisht, G.; Kawai, N.

    We present high-resolution radio and X-ray studies of the composite supernova remnant G11.2-0.3. Using archival VLA data, we perform radio spectral tomography to measure for the first time the spectrum of the shell and plerion separately. We compare the radio morphology of each component to that observed in the hard and soft Chandra X-ray images. We measure the X-ray spectra of the shell and the emission in the interior and discuss the hypothesis that soft X-ray emission interior to the shell is the result of the expanding pulsar wind shocking with the supernova ejecta. We also see evidence for spatial variability in the hard X-ray emission near the pulsar, which we discuss in terms of ion-mediated relativistic shocks.

  7. Probing the depths: Relativistic, hydrodynamic simulations and X-ray observations of pulsar wind nebulae

    NASA Astrophysics Data System (ADS)

    Bernstein, Joseph P.

    2008-06-01

    I have undertaken a joint computational and observational study of the interaction of a light, relativistic pulsar wind with a dense, ambient medium. Such a scenario has been suggested as the origin of asymmetric pulsar wind nebulae (PWNe). I present an analysis of Chandra X-ray Observatory data on the supernova remnant (SNR) MSH 11-6 2 . I show that the central region's spectrum above 2 keV is dominated by non-thermal emission consistent with that from a PWN. The spatial and spectral analyses strongly suggest that the nebula harbors a compact object with an inferred spin-down energy sufficient to rotationally power the nebula. Nebular asymmetry strongly suggests that the nebula has been crushed by the SNR reverse shock and the nebula and SNR are consistent with being in pressure equilibrium. Thus, this observation provides evidence that, in this case, the density distribution of the interstellar medium has had a dynamical effect on the morphology of the SNR/PWN system. Another scenario wherein the ambient medium influences PWNe morphology arises when the pulsar's space velocity is supersonic. In order to study such a system I have applied an existing adaptive-mesh, axisymmetric, relativistic hydrodynamic code to the simulation of the interaction of a relativistic pulsar wind with the ambient flow setup by the space motion of the pulsar. I discuss simulations showing that this interaction can give rise to asymmetry reminiscent of the Guitar nebula leading to the formation of a relativistic backflow harboring a series of internal shockwaves. The shockwaves provide thermalized energy that is available for the continued inflation of the PWN bubble. In turn, the bubble enhances the asymmetry, thereby providing positive feedback to the backflow. Further, I present the first results from an extension of the model to study the shock acceleration, and subsequent synchrotron cooling, of particles advected by the flow. The new module may be used to compute models of

  8. POST-PERIASTRON GAMMA-RAY FLARE FROM PSR B1259-63/LS 2883 AS A RESULT OF COMPTONIZATION OF THE COLD PULSAR WIND

    SciTech Connect

    Khangulyan, Dmitry; Bogovalov, Sergey V.; Ribo, Marc E-mail: felix.aharonian@dias.ie E-mail: mribo@am.ub.es

    2012-06-10

    We argue that the bright flare of the binary pulsar PSR B1259-63/LS2883 detected by the Fermi Large Area Telescope is due to the inverse Compton scattering of the unshocked electron-positron pulsar wind with a Lorentz factor {Gamma}{sub 0} Almost-Equal-To 10{sup 4}. The combination of two effects both linked to the circumstellar disk (CD) is a key element in the proposed model. The first effect is related to the impact of the surrounding medium on the termination of the pulsar wind. Inside the disk, the 'early' termination of the wind results in suppression of its gamma-ray luminosity. When the pulsar escapes the disk, the conditions for termination of the wind undergo significant changes. This would lead to a dramatic increase of the pulsar wind zone, and thus to the proportional increase of the gamma-ray flux. On the other hand, if the parts of the CD disturbed by the pulsar can supply infrared photons of density high enough for efficient Comptonization of the wind, almost the entire kinetic energy of the pulsar wind would be converted to radiation, thus the gamma-ray luminosity of the wind could approach the level of the pulsar's spin-down luminosity as reported by the Fermi Collaboration.

  9. EXTENDED HARD X-RAY EMISSION FROM THE VELA PULSAR WIND NEBULA

    SciTech Connect

    Mattana, F.; Terrier, R.; Zurita Heras, J. A.; Goetz, D.; Caballero, I.; Soldi, S.; Schanne, S.; Ponti, G.; Falanga, M.; Renaud, M.

    2011-12-10

    The nebula powered by the Vela pulsar is one of the best examples of an evolved pulsar wind nebula, allowing access to the particle injection history and the interaction with the supernova ejecta. We report on the INTEGRAL discovery of extended emission above 18 keV from the Vela nebula. The northern side has no known counterparts and it appears larger and more significant than the southern one, which is in turn partially coincident with the cocoon, the soft X-ray, and TeV filament toward the center of the remnant. We also present the spectrum of the Vela nebula in the 18-400 keV energy range as measured by IBIS/ISGRI and SPI on board the INTEGRAL satellite. The apparent discrepancy between IBIS/ISGRI, SPI, and previous measurements is understood in terms of the point-spread function, supporting the hypothesis of a nebula more diffuse than previously thought. A break at {approx}25 keV is found in the spectrum within 6' from the pulsar after including the Suzaku XIS data. Interpreted as a cooling break, this points out that the inner nebula is composed of electrons injected in the last {approx}2000 years. Broadband modeling also implies a magnetic field higher than 10 {mu}G in this region. Finally, we discuss the nature of the northern emission, which might be due to fresh particles injected after the passage of the reverse shock.

  10. X-ray studies of the termination shock of the pulsar wind in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Mori, K.; Burrows, D.; Shibata, S.; Pavlov, G.; Hester, J.; Tsunemi, H.

    Chandra observations have discovered a long-sought termination shock of the pulsar wind in the Crab Nebula. The shock is barely seen in the optical wavelengths in contrast with the wisps, which emerge from the shock but can be seen in both the X-ray and optical. We present spectral and spatial analysis of the shock with Chandra. Especially, spectral information is obtained for the first time without being bothered by pile-up. Spectral analysis of other fine structures including "arcs" which are seen in north-eastern part of the torus is also shown. We discuss those results along with large scale spectral variations over the nebula.

  11. THE BALMER-DOMINATED BOW SHOCK AND WIND NEBULA STRUCTURE OF {gamma}-RAY PULSAR PSR J1741-2054

    SciTech Connect

    Romani, Roger W.; Shaw, Michael S.; Camilo, Fernando; Cotter, Garret; Sivakoff, Gregory R. E-mail: msshaw@stanford.ed

    2010-12-01

    We have detected an H{alpha} bow shock nebula around PSR J1741-2054, a pulsar discovered through its GeV {gamma}-ray pulsations. The pulsar is only {approx}1.''5 behind the leading edge of the shock. Optical spectroscopy shows that the nebula is non-radiative, dominated by Balmer emission. The H{alpha} images and spectra suggest that the pulsar wind momentum is equatorially concentrated and implies a pulsar space velocity {approx}150 km s{sup -1}, directed 15{sup 0} {+-} 10{sup 0} out of the plane of the sky. The complex H{alpha} profile indicates that different portions of the post-shock flow dominate line emission as gas moves along the nebula and provide an opportunity to study the structure of this unusual slow non-radiative shock under a variety of conditions. CXO ACIS observations reveal an X-ray pulsar wind nebula within this nebula, with a compact {approx}2.''5 equatorial structure and a trail extending several arcminutes behind. Together these data support a close ({<=}0.5 kpc) distance, a spin geometry viewed edge-on, and highly efficient {gamma}-ray production for this unusual, energetic pulsar.

  12. The electromagnetic interaction of a planet with a rotation-powered pulsar wind: an explanation to fast radio bursts

    NASA Astrophysics Data System (ADS)

    Mottez, F.; Zarka, P.

    2015-12-01

    The pulsars PSR B1257+12 and PSR B1620-26 are known to host planets, and other pulsars are suspected to host asteroids or comets. We investigate the electromagnetic interaction of a relativistic and magnetized pulsar wind with a planet or a smaller body in orbit. Many models predict that, albeit highly relativistic, pulsar winds are slower than Alfven waves. In that case, a pair of stationary Alfven waves, called Alfven wings (AW), is expected to form on the sides of the body. They form a magnetic wake into the plasma flow, and they carry a strong electric current. The theory of Alfven wings was initially developed in the context of the electrodynamic interaction between spacecraft and the Earth's magnetosphere, and then of the Io-Jupiter interaction. We have extended it to relativistic winds, and we have studied the possible consequences on radio emissions from pulsar companions. We predict the existence of very collimated radio beams that are seen by an observer as very rare and brief signals. But they are intense enough to be observed from sources at cosmological distances. Thus they could be an explanation to fast radio bursts (FRB). We discuss the properties (polarisation, recurrence) that could make the difference between this model of FRB and others.

  13. Latest Results on Pulsar Wind Nebulae on the TeV Energy Regime

    NASA Astrophysics Data System (ADS)

    de Oña Wilhelmi, E.

    2011-08-01

    The last few years have seen a revolution in very high γ-ray astronomy (VHE E>100 GeV) driven largely by a new generation of Cherenkov telescopes. These new facilities, namely H.E.S.S. (High Energy Stereoscopic System), MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescope) and its upgrade MAGIC 2, Veritas (Very Energetic Radiation Imaging Telescope Array System) and CANGAROO (Collaboration of Australia and Nippon for a Gamma Ray Observatory in the Outback) were designed to increase the flux sensitivity in the energy regime of hundreds of GeV, expanding the observed energy range from 100 (50) GeV to multi-TeV, and fostered as a result a period of rapid growth in our understanding of the Non-Thermal Universe. As a result of this fast development the number of pulsar wind nebulae (PWNe) detected has increased from a few in the early 90's to more than two dozen of firm candidates nowadays. A review of the most relevant VHE results concerning pulsars and their relativistic winds is discussed here in the context of Cherenkov telescopes.

  14. THE EFFECT OF DIFFUSION ON THE PARTICLE SPECTRA IN PULSAR WIND NEBULAE

    SciTech Connect

    Vorster, M. J.; Moraal, H.

    2013-03-01

    A possible way to calculate particle spectra as a function of position in pulsar wind nebulae is to solve a Fokker-Planck transport equation. This paper presents numerical solutions to the transport equation with the processes of convection, diffusion, adiabatic losses, and synchrotron radiation included. In the first part of the paper, the steady-state version of the transport equation is solved as a function of position and energy. This is done to distinguish the various effects of the aforementioned processes on the solutions to the transport equation. The second part of the paper deals with a time-dependent solution to the transport equation, specifically taking into account the effect of a moving outer boundary. The paper highlights the fact that diffusion can play a significant role in reducing the amount of synchrotron losses, leading to a modification in the expected particle spectra. These modified spectra can explain the change in the photon index of the synchrotron emission as a function of position. The solutions presented in this paper are not limited to pulsar wind nebulae, but can be applied to any similar central source system, e.g., globular clusters.

  15. Near-Infrared, Kilosecond Variability of the Wisps And Jet in the Crab Pulsar Wind Nebula

    SciTech Connect

    Melatos, Andrew; Scheltus, D.; Whiting, M.T.; Eikenberry, S.S.; Romani, R.W.; Rigaut, F.; Spitkovsky, A.; Arons, J.; Payne, D.J.B.; /Melbourne U.

    2006-01-11

    We present a time-lapse sequence of 20 near-infrared (J- and K'-band) snapshots of the central 20'' x 20'' of the Crab pulsar wind nebula, taken at sub-arcsecond resolution with the Hokupa'a/QUIRC adaptive optics camera on the Gemini North Telescope, and sampled at intervals of 10 minutes and 24 hours. It is observed that the equatorial wisps and polar knots in the termination shock of the pulsar wind appear to fluctuate in brightness on kilosecond time-scales. Maximum flux variations of {+-}24 {+-} 4 and {+-}14 {+-} 4 per cent relative to the mean (in 1.2 ks) are measured for the wisps and knots respectively, with greatest statistical significance in J band where the nebula background is less prominent. The J and K' flux densities imply different near-infrared spectra for the nonthermal continuum emission from the wisps and outermost polar knot (''sprite''), giving F{sub {nu}} {proportional_to} {nu}{sup -0.56{+-}0.12} and F{sub {nu}} {proportional_to} {nu}{sup -0.21{+-}0.13} respectively. The data are compared with existing optical and UV photometry and applied to constrain theories of the variability of the wisps (relativistic ion-cyclotron instability) and knots (relativistic fire hose instability).

  16. Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N 157B with H.E.S.S.

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Atäı, A.; Domainko, W.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; G´rard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Grondin, M.-H.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; K´ski, K.; Katz, U.; Kaufmann, S.; K´lifi, B.; Klochkov, D.; K´niak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; M´hault, J.; Menzler, U.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Lstrok; .; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2012-09-01

    We present the significant detection of the first extragalactic pulsar wind nebula (PWN) detected in gamma rays, N 157B, located in the large Magellanic Cloud (LMC). Pulsars with high spin-down luminosity are found to power energised nebulae that emit gamma rays up to energies of several tens of TeV. N 157B is associated with PSR J0537-6910, which is the pulsar with the highest known spin-down luminosity. The High Energy Stereoscopic System telescope array observed this nebula on a yearly basis from 2004 to 2009 with a dead-time corrected exposure of 46 h. The gamma-ray spectrum between 600 GeV and 12 TeV is well-described by a pure power-law with a photon index of 2.8 ± 0.2stat ± 0.3syst and a normalisation at 1 TeV of (8.2 ± 0.8stat ± 2.5syst) × 10-13 cm-2 s-1 TeV-1. A leptonic multi-wavelength model shows that an energy of about 4 × 1049 erg is stored in electrons and positrons. The apparent efficiency, which is the ratio of the TeV gamma-ray luminosity to the pulsar's spin-down luminosity, 0.08% ± 0.01%, is comparable to those of PWNe found in the Milky Way. The detection of a PWN at such a large distance is possible due to the pulsar's favourable spin-down luminosity and a bright infrared photon-field serving as an inverse-Compton-scattering target for accelerated leptons. By applying a calorimetric technique to these observations, the pulsar's birth period is estimated to be shorter than 10 ms. Data set is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/L2

  17. THE VELA-X PULSAR WIND NEBULA REVISITED WITH FOUR YEARS OF FERMI LARGE AREA TELESCOPE OBSERVATIONS

    SciTech Connect

    Grondin, M.-H.; Romani, R. W.; Lemoine-Goumard, M.; Reposeur, T.; Harding, A. K.

    2013-09-10

    The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2 Degree-Sign Multiplication-Sign 3 Degree-Sign south of the pulsar and observed in the radio, X-ray, and very high energy {gamma}-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

  18. The VELA-X-Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations

    NASA Technical Reports Server (NTRS)

    Grondin, M. -H.; Romani, R. W.; Lemoine-Goumard, M.; Guillemot, L.; Harding, Alice K.; Reposeur, T.

    2013-01-01

    The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2deg × 3deg south of the pulsar and observed in the radio, X-ray, and very high energy ?-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

  19. Constraint on pulsar wind properties from induced Compton scattering off radio pulses

    NASA Astrophysics Data System (ADS)

    Tanaka, Shuta J.; Takahara, Fumio

    2013-12-01

    Pulsar winds have longstanding problems in energy conversion and pair cascade processes, which determine the magnetization σ , the pair multiplicity kappa , and the bulk Lorentz factor γ of the wind. We study induced Compton scattering by a relativistically moving cold plasma to constrain the wind properties by imposing that radio pulses from the pulsar itself are not scattered by the wind, as was first studied by Wilson and Rees [D. B. Wilson and M. J. Rees, Mon. Not. R. Astron. Soc., 185, 297 (1978)]. We find that relativistic effects cause a significant increase or decrease of the scattering coefficient depending on scattering geometry. Applying this to the Crab, we consider the uncertainties of the inclination angle of the wind velocity with respect to the radio beam θ _{pl} and the emission region size re, which determines the opening angle of the radio beam. We obtain the lower limit γ gtrsim 10^{1.7} r^{1/2}_{{e},3}θ ^{-1}_pl(1+σ)^{-1/4} (re = 10^3r_{{ e},3} cm) at the light cylinder r_{LC} for an inclined wind θ _{pl} >10^{-2.7}. For an aligned wind θ _{pl} < 10^{-2.7}, we require γ >10^{2.7} at r_{LC} and an additional constraint γ >10^{3.4}r^{1/5}_{{e},3}(1+σ)^{-1/10} at the characteristic scattering radius r_c=10^{9.6}r^{2/5}_{{e},3} cm, within which the `lack of time' effect prevents scattering. Considering the lower limit kappa gtrsim 10^{6.6} suggested by recent studies of the Crab Nebula, for re=10^3 cm, we obtain the most optimistic constraint 10^{1.7}lesssim γ lesssim 10^{3.9} and 10^{6.6}lesssim kappa lesssim 10^{8.8}, which are independent of r when θ _{pl}˜ 1 and 1+σ ˜ 1 at r_LC.

  20. Muons emitted from showers produced by Geminga-pulsar gamma rays.

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, D. P.

    1997-12-01

    The derivation of integral energy spectrum of muons produced by the interactions in gamma-ray showers induced by energetic photons from the Geminga pulsar has been made. The conventional analytical procedure of Drees et al. (1988) has been adopted for muon-number calculations from photoproduced air showers. The FNAL data on πp→π±X inclusive reactions, and the HERA ep collider results have been used for the evaluation of the hadronic energy moments and the photonuclear cross-sections, respectively. The integral number of muons was derived for Zππ = 0.499, σγN = 0.119 mb and σπA = 198 mb. It exhibits a drastic decrease with energy.

  1. The effects of magnetic field, age and intrinsic luminosity on Crab-like pulsar wind nebulae

    NASA Astrophysics Data System (ADS)

    Torres, D. F.; Martín, J.; de Oña Wilhelmi, E.; Cillis, Analia

    2013-12-01

    We investigate the time-dependent behaviour of Crab-like pulsar wind nebulae (PWNe) generating a set of models using four different initial spin-down luminosities (L0 = {1, 0.1, 0.01, 0.001} × L0,Crab), eight values of magnetic fraction (η = 0.001, 0.01, 0.03, 0.1, 0.5, 0.9, 0.99 and 0.999, i.e. from fully particle dominated to fully magnetically dominated nebulae) and three distinctive ages: 940, 3000 and 9000 years. We find that the self-synchrotron Compton (SSC) contribution is irrelevant for LSD = 0.1, 1 and 10 per cent of the Crab power, disregarding the age and the magnetic fraction. SSC only becomes relevant for highly energetic (˜70 per cent of the Crab), particle dominated nebulae at low ages (of less than a few kyr), located in a far-infrared (FIR) background with relatively low energy density. Since no pulsar other than Crab is known to have these features, these results clarify why the Crab nebula, and only it, is SSC dominated. No young PWN would be detectable at TeV energies if the pulsar's spin-down power is 0.1 per cent Crab or lower. For 1 per cent of the Crab spin-down, only particle-dominated nebulae can be detected by HESS-like telescopes when young enough (with details depending on the precise injection and environmental parameters). Above 10 per cent of the Crab's power, all PWNe are detectable by HESS-like telescopes if they are particle dominated, no matter the age. The impact of the magnetic fraction on the final spectral energy distribution is varied and important, generating order of magnitude variations in the luminosity output for systems that are otherwise the same (equal P, dot{P}, injection and environment).

  2. SEARCH FOR VERY HIGH ENERGY GAMMA-RAY EMISSION FROM PULSAR-PULSAR WIND NEBULA SYSTEMS WITH THE MAGIC TELESCOPE

    SciTech Connect

    Anderhub, H.; Biland, A.; Antonelli, L. A.; Antoranz, P.; Balestra, S.; Barrio, J. A.; Bose, D.; Backes, M.; Becker, J. K.; Baixeras, C.; Bastieri, D.; Bock, R. K.; Gonzalez, J. Becerra; Bednarek, W.; Berger, K.; Bernardini, E.; Bonnoli, G.; Bordas, P.; Bosch-Ramon, V.; Tridon, D. Borla E-mail: miguel@gae.ucm.e

    2010-02-10

    The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.

  3. Can the Subsonic Accretion Model Explain the Spin Period Distribution of Wind-fed X-Ray Pulsars?

    NASA Astrophysics Data System (ADS)

    Li, Tao; Shao, Yong; Li, Xiang-Dong

    2016-06-01

    Neutron stars in high-mass X-ray binaries (HMXBs) generally accrete from the wind matter of their massive companion stars. Recently, Shakura et al. suggested a subsonic accretion model for low-luminosity (<4 × 1036 erg s‑1), wind-fed X-ray pulsars. To test the feasibility of this model, we investigate the spin period distribution of wind-fed X-ray pulsars with a supergiant companion star, using a population synthesis method. We find that the modeled distribution of supergiant HMXBs in the spin period–orbital period diagram is consistent with observations, provided that the winds from the donor stars have relatively low terminal velocities (≲1000 km s‑1). The measured wind velocities in several supergiant HMXBs seem to favor this viewpoint. The predicted number ratio of wind-fed X-ray pulsars with persistent X-ray luminosities that are higher and lower than 4 × 1036 erg s‑1 is about 1:10.

  4. Chandra Detection of a Pulsar Wind Nebula Associated With Supernova Remnant 3C 396

    NASA Technical Reports Server (NTRS)

    Olbert, C. M.; Keohane, J. W.; Arnaud, K. A.; Dyer, K. K.; Reynolds, S. P.; Safi-Harb, S.

    2003-01-01

    We present a 100 ks observation of the Galactic supernova remnant 3C396 (G39.2-0.3) with the Chandra X-Ray Observatory that we compare to a 20cm map of the remnant from the Very Large Array. In the Chandra images, a nonthermal nebula containing an embedded pointlike source is apparent near the center of the remnant which we interpret as a synchrotron pulsar wind nebula surrounding a yet undetected pulsar. From the 2-10 keV spectrum for the nebula (N(sub H) = 5.3 plus or minus 0.9 x 10(exp 22) per square centimeter, GAMMA =1.5 plus or minus 0.3) we derive an unabsorbed x-ray flux of S(sub z)=1.62 x 10(exp -12) erg per square centimeter per second, and from this we estimate the spin-down power of the neutron star to be E(sup dot) = 7.2 x 10(exp 36) ergs per second. The central nebula is morphologically complex, showing bent, extended structure. The radio and X-ray shells of the remnant correlate poorly on large scales, particularly on the eastern half of the remnant, which appears very faint in X-ray images. At both radio and X-ray wavelengths the western half of the remnant is substantially brighter than the east.

  5. THE ROLE OF SUPERLUMINAL ELECTROMAGNETIC WAVES IN PULSAR WIND TERMINATION SHOCKS

    SciTech Connect

    Amano, Takanobu; Kirk, John G.

    2013-06-10

    The dynamics of a standing shock front in a Poynting-flux-dominated relativistic flow is investigated by using a one-dimensional, relativistic, two-fluid simulation. An upstream flow containing a circularly polarized, sinusoidal magnetic shear wave is considered, mimicking a wave driven by an obliquely rotating pulsar. It is demonstrated that this wave is converted into large-amplitude electromagnetic waves with superluminal phase speeds by interacting with the shock when the shock-frame frequency of the wave exceeds the proper plasma frequency. The superluminal waves propagate in the upstream, modify the shock structure substantially, and form a well-developed precursor region ahead of a subshock. Dissipation of Poynting flux occurs in the precursor as well as in the downstream region through a parametric instability driven by the superluminal waves. The Poynting flux remaining in the downstream region is carried entirely by the superluminal waves. The downstream plasma is therefore an essentially unmagnetized, relativistically hot plasma with a non-relativistic flow speed, as suggested by observations of pulsar wind nebulae.

  6. Mapping supernova remnants and pulsar wind nebulae across decades of energy

    NASA Astrophysics Data System (ADS)

    Hewitt, John W.

    2016-04-01

    Ground- and space-based gamma ray observatories of the past decade have given us a new understanding of particle accelerators in our galaxy. The improved spatial resolution and sensitivity of recent gamma-ray surveys of the Galactic plane have resolved confusion of sources identified numerous sources to study the physics of particle acceleration and the diffusion of energetic particles into the galaxy. Here I highlight some recent studies of Galactic accelerators from GeV to TeV energies, that allow us to disentangle hadronic from leptonic emission, constrain cosmic ray diffusion, and measure the conditions of particle acceleration. Supernova remnants and pulsar wind nebulae are found to be the two most common Galactic sources identified in very high energy gamma rays, and the future capabilities of CTA promise a dramatic increase in our knowledge of these classes which are currently limited to only a few of the most well-studied cases.

  7. Searching for the Thermal Plasma in the Naked Pulsar Wind Nebula CTB 87

    NASA Astrophysics Data System (ADS)

    Safi-Harb, Samar

    2013-10-01

    The missing thermal X-ray emission from dozens of naked pulsar wind nebulae (PWNe) remains one of the most puzzling questions in the SNR field. Our understanding of PWNe has been largely biased by the study of the brightest and youngest objects, such as the Crab nebula. We propose a deep EPIC observation of CTB 87. Our Chandra study, complemented with multi-wavelength observations, suggests that this remnant is an evolved PWN, most likely crushed by the supernova explosion's reverse shock. Alternatively, a bow-shock interpretation is also plausible. Our proposed observation will discriminate between these two scenarios. XMM-Newton is the ideal facility to perform a deep search for the thermal emission expected at the PWN-reverse shock interaction site and from the long-sought SNR shell.

  8. High-Energy X-Ray Imaging of the Pulsar Wind Nebula MSH 15-52: Constraints on Particle Acceleration and Transport

    NASA Technical Reports Server (NTRS)

    An, Hongjun; Madsen, Kristin K.; Reynolds, Stephen P.; Kaspi, Victoria M.; Harrison, Fiona A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fryer, Chris L.; Grefenstette, Brian W.; Zhang, William W.

    2014-01-01

    We present the first images of the pulsar wind nebula (PWN) MSH 15-52 in the hard X-ray band (8 keV), as measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall, the morphology of the PWN as measured by NuSTAR in the 3-7 keV band is similar to that seen in Chandra high-resolution imaging. However, the spatial extent decreases with energy, which we attribute to synchrotron energy losses as the particles move away from the shock. The hard-band maps show a relative deficit of counts in the northern region toward the RCW 89 thermal remnant, with significant asymmetry. We find that the integrated PWN spectra measured with NuSTAR and Chandra suggest that there is a spectral break at 6 keV, which may be explained by a break in the synchrotron emitting electron distribution at approximately 200 TeV and/or imperfect cross calibration. We also measure spatially resolved spectra, showing that the spectrum of the PWN softens away from the central pulsar B1509-58, and that there exists a roughly sinusoidal variation of spectral hardness in the azimuthal direction. We discuss the results using particle flow models. We find non-monotonic structure in the variation with distance of spectral hardness within 50 of the pulsar moving in the jet direction, which may imply particle and magnetic-field compression by magnetic hoop stress as previously suggested for this source. We also present two-dimensional maps of spectral parameters and find an interesting shell-like structure in the N(sub H) map. We discuss possible origins of the shell-like structure and their implications.

  9. High-energy X-ray imaging of the pulsar wind nebula MSH 15–52: constraints on particle acceleration and transport

    SciTech Connect

    An, Hongjun; Kaspi, Victoria M.; Madsen, Kristin K.; Harrison, Fiona A.; Grefenstette, Brian W.; Reynolds, Stephen P.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Fryer, Chris L.; Hailey, Charles J.; Mori, Kaya; Stern, Daniel; Zhang, William W.

    2014-10-01

    We present the first images of the pulsar wind nebula (PWN) MSH 15–52 in the hard X-ray band (≳8 keV), as measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall, the morphology of the PWN as measured by NuSTAR in the 3-7 keV band is similar to that seen in Chandra high-resolution imaging. However, the spatial extent decreases with energy, which we attribute to synchrotron energy losses as the particles move away from the shock. The hard-band maps show a relative deficit of counts in the northern region toward the RCW 89 thermal remnant, with significant asymmetry. We find that the integrated PWN spectra measured with NuSTAR and Chandra suggest that there is a spectral break at 6 keV, which may be explained by a break in the synchrotron-emitting electron distribution at ∼200 TeV and/or imperfect cross calibration. We also measure spatially resolved spectra, showing that the spectrum of the PWN softens away from the central pulsar B1509–58, and that there exists a roughly sinusoidal variation of spectral hardness in the azimuthal direction. We discuss the results using particle flow models. We find non-monotonic structure in the variation with distance of spectral hardness within 50'' of the pulsar moving in the jet direction, which may imply particle and magnetic-field compression by magnetic hoop stress as previously suggested for this source. We also present two-dimensional maps of spectral parameters and find an interesting shell-like structure in the N {sub H} map. We discuss possible origins of the shell-like structure and their implications.

  10. Crab Flares due to Turbulent Dissipation of the Pulsar Striped Wind

    NASA Astrophysics Data System (ADS)

    Zrake, Jonathan

    2016-05-01

    We interpret γ-ray flares from the Crab Nebula as the signature of turbulence in the pulsar’s electromagnetic outflow. Turbulence is triggered upstream by dynamical instability of the wind’s oscillating magnetic field and accelerates non-thermal particles. On impacting the wind-termination shock, these particles emit a distinct synchrotron component {F}ν ,{flare}, which is constantly modulated by intermittency of the upstream plasma flow. Flares are observed when the high-energy cutoff of {F}ν ,{flare} emerges above the fast-declining nebular emission around 0.1–1 GeV. Simulations carried out in the force-free electrodynamics approximation predict the striped wind to become fully turbulent well ahead of the wind-termination shock, provided its terminal Lorentz factor is ≲ {10}4.

  11. Ionization break-out from millisecond pulsar wind nebulae: an X-ray probe of the origin of superluminous supernovae

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Vurm, Indrek; Hascoët, Romain; Beloborodov, Andrei M.

    2014-01-01

    Magnetic spin-down of a rapidly rotating (millisecond) neutron star has been proposed as the power source of hydrogen-poor `superluminous' supernovae (SLSNe-I). However, producing an unambiguous test that can distinguish this model from alternatives, such as circumstellar interaction, has proven challenging. After the supernova explosion, the pulsar wind inflates a hot cavity behind the expanding stellar ejecta: the nascent millisecond pulsar wind nebula. Electron/positron pairs injected by the wind cool through inverse Compton scattering and synchrotron emission, producing a pair cascade and hard X-ray spectrum inside the nebula. These X-rays ionize the inner exposed side of the ejecta, driving an ionization front that propagates outwards with time. Under some conditions this front can breach the ejecta surface within months after the optical supernova peak, allowing ˜0.1-1 keV photons to escape the nebula unattenuated with a characteristic luminosity LX ˜ 1043-1045 erg s-1. This `ionization break-out' may explain the luminous X-ray emission observed from the transient SCP 06F, providing direct evidence that this SLSN was indeed engine powered. Luminous break-out requires a low ejecta mass and that the spin-down time of the pulsar be comparable to the photon diffusion time-scale at optical maximum, the latter condition being similar to that required for a supernova with a high optical fluence. These relatively special requirements may explain why most SLSNe-I are not accompanied by detectable X-ray emission. Global asymmetry of the supernova ejecta increases the likelihood of an early break-out along the direction of lowest density. Atomic states with lower threshold energies are more readily ionized at earlier times near optical maximum, allowing `UV break-out' across a wider range of pulsar and ejecta properties than X-ray break-out, possibly contributing to the blue/UV colours of SLSNe-I.

  12. Detection of 16 gamma-ray pulsars through blind frequency searches using the Fermi LAT.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Baring, M G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Bignami, G F; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Gwon, C; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jóhannesson, G; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Primack, J R; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J G; Thompson, D J; Tibaldo, L; Tibolla, O; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Van Etten, A; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Watters, K; Winer, B L; Wolff, M T; Wood, K S; Ylinen, T; Ziegler, M

    2009-08-14

    Pulsars are rapidly rotating, highly magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently only seven were observed to pulse in gamma rays, and these were all discovered at other wavelengths. The Fermi Large Area Telescope (LAT) makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics, and the energetics of pulsar wind nebulae and supernova remnants. PMID:19574346

  13. Molecular environment, reverberation, and radiation from the pulsar wind nebula in CTA 1

    NASA Astrophysics Data System (ADS)

    Martín, Jonatan; Torres, Diego F.; Pedaletti, Giovanna

    2016-07-01

    We estimate the molecular mass around CTA 1 using data from Planck and the Harvard CO survey. We observe that the molecular mass in the vicinity of the complex is not enough to explain the TeV emission observed by VERITAS, even under favorable assumptions for the cosmic ray acceleration properties of the supernova remnant. This supports the idea that the TeV emission comes from the pulsar wind nebula (PWN). Here, we model the spectrum of the PWN at possible different stages of its evolution, including both the dynamics of the PWN and the supernova remnant and their interaction via the reverse shock. We have included in the model the energy lost via radiation by particles and the particles escape when computing the pressure produced by the gas. This leads to an evolving energy partition, since for the same instantaneous sharing of the injection of energy provided by the rotational power, the field and the particles are affected differently by radiation and losses. We present the model, and study in detail how the spectrum of a canonical isolated PWN is affected during compression and re-expansion and how this may impact on the CTA 1 case. By exploring the phase-space of parameters that lead to radii in agreement with those observed, we then analyse different situations that might represent the current stage of the CTA 1 PWN, and discuss caveats and requirements of each one.

  14. Diffusion in pulsar wind nebulae: an investigation using magnetohydrodynamic and particle transport models

    NASA Astrophysics Data System (ADS)

    Porth, O.; Vorster, M. J.; Lyutikov, M.; Engelbrecht, N. E.

    2016-08-01

    We study the transport of high-energy particles in pulsar wind nebulae (PWN) using three-dimensional magnetohydrodynamic (MHD) and test-particle simulations, as well as a Fokker-Planck particle transport model. The latter includes radiative and adiabatic losses, diffusion, and advection on the background flow of the simulated MHD nebula. By combining the models, the spatial evolution of flux and photon index of the X-ray synchrotron emission is modelled for the three nebulae G21.5-0.9, the inner regions of Vela, and 3C 58, thereby allowing us to derive governing parameters: the magnetic field strength, average flow velocity, and spatial diffusion coefficient. For comparison, the nebulae are also modelled with the semi-analytic Kennel & Coroniti model but the Porth et al. model generally yields better fits to the observational data. We find that high velocity fluctuations in the turbulent nebula (downstream of the termination shock) give rise to efficient diffusive transport of particles, with average Péclet number close to unity, indicating that both advection and diffusion play an important role in particle transport. We find that the diffusive transport coefficient of the order of ˜ 2 × 1027(Ls/0.42 Ly) cm2 s- 1 (Ls is the size of the termination shock) is independent of energy up to extreme particle Lorentz factors of γp ˜ 1010.

  15. Discovery of a Pulsar Wind Nebula Candidate in the Cygnus Loop

    NASA Technical Reports Server (NTRS)

    Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Petre, Robert; Yamada, Shin'ya; Tamagawa, Toru

    2012-01-01

    We report on a discovery of a diffuse nebula containing a point-like source in the southern blowout region of the Cygnus Loop supernova remnant, based on Suzaku and XMM-Newton observations. The X-ray spectra from the nebula and the point-like source are well represented by an absorbed power-law model with photon indices of 2.2+/-0.1 and 1.6+/-0.2, respectively. The photon indices as well as the flux ratio of F(sub nebula)/F(sub point-like) approx. 4 lead us to propose that the system is a pulsar wind nebula, although pulsations have not yet been detected. If we attribute its origin to the Cygnus Loop supernova, then the 0.5-8 keV luminosity of the nebula is computed to be 2.1x10(exp 31)(d/540pc)(exp 2)ergss/2, where d is the distance to the Loop. This implies a spin-down loss-energy E approx. 2.6x10(exp 35)(d/540pc)(exp 2)ergs/s. The location of the neutron star candidate, approx.2deg away from the geometric center of the Loop, implies a high transverse velocity of approx.1850(theta/2deg)(d/540pc)(t/10kyr)/k/s assuming the currently accepted age of the Cygnus Loop.

  16. Supernova remnants and pulsar wind nebulae with Imaging Atmospheric Cherenkov Telescopes (IACTs)

    NASA Astrophysics Data System (ADS)

    Eger, Peter

    2015-08-01

    The observation of very-high-energy (VHE, E > 100 GeV) gamma rays is an excellent tool to study the most energetic and violent environments in the Galaxy. This energy range is only accessible with ground-based instruments such as Imaging Atmospheric Cherenkov Telescopes (IACTs) that reconstruct the energy and direction of the primary gamma ray by observing the Cherenkov light from the induced extended air showers in Earths atmosphere. The main goals of Galactic VHE gamma-ray science are the identification of individual sources of cosmic rays (CRs), such as supernova remnants (SNRs), and the study of other extreme astrophysical objects at the highest energies, such as gamma-ray binaries and pulsar wind nebulae (PWNe). One of the main challenges is the discrimination between leptonic and hadronic gamma-ray production channels. To that end, the gamma-ray signal from each individual source needs to be brought into context with the multi-wavelength environment of the astrophysical object in question, particularly with observations tracing the density of the surrounding interstellar medium, or synchrotron radiation from relativistic electrons. In this review presented at the European Cosmic Ray Symposium 2014 (ECRS2014), the most recent developments in the field of Galactic VHE gamma-ray science are highlighted, with particular emphasis on SNRs and PWNe.

  17. Diffusion in pulsar wind nebulae: an investigation using magnetohydrodynamic and particle transport models

    NASA Astrophysics Data System (ADS)

    Porth, O.; Vorster, M. J.; Lyutikov, M.; Engelbrecht, N. E.

    2016-08-01

    We study the transport of high-energy particles in pulsar wind nebulae (PWN) using three-dimensional MHD (see Porth et al. (2014) for details) and test-particle simulations, as well as a Fokker-Planck particle transport model. The latter includes radiative and adiabatic losses, diffusion, and advection on the background flow of the simulated MHD nebula. By combining the models, the spatial evolution of flux and photon index of the X-ray synchrotron emission is modelled for the three nebulae G21.5-0.9, the inner regions of Vela, and 3C 58, thereby allowing us to derive governing parameters: the magnetic field strength, average flow velocity and spatial diffusion coefficient. For comparison, the nebulae are also modelled with the semi-analytic Kennel & Coroniti (1984) model but the Porth et al. (2014) model generally yields better fits to the observational data. We find that high velocity fluctuations in the turbulent nebula (downstream of the termination shock) give rise to efficient diffusive transport of particles, with average P\\'eclet number close to unity, indicating that both advection and diffusion play an important role in particle transport. We find that the diffusive transport coefficient of the order of $\\sim2\\times 10^{27} (L_{\\rm s}/0.42\\rm Ly) cm^{2}s^{-1}$ ($L_{\\rm s}$ is the size of the termination shock) is independent of energy up to extreme particle Lorentz factors of $\\gamma_{p}\\sim10^{10}$.

  18. Observations of supernova remnants and pulsar wind nebulae at gamma-ray energies

    NASA Astrophysics Data System (ADS)

    Hewitt, John W.; Lemoine-Goumard, Marianne

    2015-08-01

    In the past few years, gamma-ray astronomy has entered a golden age thanks to two major breakthroughs: Cherenkov telescopes on the ground and the Large Area Telescope (LAT) onboard the Fermi satellite. The sample of supernova remnants (SNRs) detected at gamma-ray energies is now much larger: it goes from evolved supernova remnants interacting with molecular clouds up to young shell-type supernova remnants and historical supernova remnants. Studies of SNRs are of great interest, as these analyses are directly linked to the long standing issue of the origin of the Galactic cosmic rays. In this context, pulsar wind nebulae (PWNe) need also to be considered since they evolve in conjunction with SNRs. As a result, they frequently complicate interpretation of the gamma-ray emission seen from SNRs and they could also contribute directly to the local cosmic ray spectrum, particularly the leptonic component. This paper reviews the current results and thinking on SNRs and PWNe and their connection to cosmic ray production. xml:lang="fr"

  19. Spatial dependence of high energy electrons and their radiations in pulsar wind nebulae

    NASA Astrophysics Data System (ADS)

    Lu, Fang-Wu; Gao, Quan-Gui; Zhang, Li

    2016-06-01

    We investigate the spatial dependence of high energy electrons and their radiations in pulsar wind nebulae (PWNe). By assuming a time-dependent broken power-law injection and spatial dependence of convection velocity, magnetic field strength and diffusion coefficient on the radial distance of an expanding system, we numerically solve the Fokker-Planck transport equation including convection, diffusion, adiabatic loss and radiative loss in spherical coordinates, and investigate the effects of magnetic field, PWN age, maximum energy of electrons, and diffusion coefficient on electron spectra and non-thermal photon emissions. Our results indicate that (1) electron spectra and the corresponding photon spectra are a function of radial distance r of the expanding system; (2) for a given expansion velocity, the increase of the PWN age causes a slower decrease of the convection velocity (V ∝ r ‑β) and a more rapid decrease of the magnetic field strength (B ∝ r ‑1+β), but a more rapid increase of the diffusion coefficient (κ ∝ r 1‑β) because the index β decreases with the PWN age; and (3) the lower energy part of the electron spectra is dominated by convection and adiabatic loss, but the higher energy part is dominated by the competition between synchrotron loss and diffusion, and such a competition is a function of radial distance. Therefore the diffusion effect has an important role in the evolution of electron spectra as well as non-thermal photon spectra in a PWN.

  20. Cosmic Ray Positrons from Pulsars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2010-01-01

    Pulsars are potential Galactic sources of positrons through pair cascades in their magnetospheres. There are, however, many uncertainties in establishing their contribution to the local primary positron flux. Among these are the local density of pulsars, the cascade pair multiplicities that determine the injection rate of positrons from the pulsar, the acceleration of the injected particles by the pulsar wind termination shock, their rate of escape from the pulsar wind nebula, and their propagation through the interstellar medium. I will discuss these issues in the context of what we are learning from the new Fermi pulsar detections and discoveries.

  1. On the power spectra of the wind-fed X-ray binary pulsar GX 301 - 2

    NASA Technical Reports Server (NTRS)

    Orlandini, Mauro; Morfill, G. E.

    1992-01-01

    A phenomenological model of accretion which is applied to the wind-fed X-ray binary pulsar GX 301 - 2 is developed, assuming that the accretion onto the neutron star does not occur from a continuous flux of plasma, but from blobs of matter which are threaded by the magnetic field lines onto the magnetic polar caps of the neutron star. These 'lumps' are produced at the magnetospheric limit by magnetohydrodynamical instability, introducing a 'noise' in the accretion process, due to the discontinuity in the flux of matter onto the neutron star. This model is able to describe the change of slope observed in the continuum component of the power spectra of the X-ray binary pulsar GX 301 - 2, in the frequency range 0.01 - 0.1 Hz. The physical properties of the infalling blobs derived in the model are in agreement with the constraints imposed by observations.

  2. On gigahertz spectral turnovers in pulsars

    NASA Astrophysics Data System (ADS)

    Rajwade, K.; Lorimer, D. R.; Anderson, L. D.

    2016-01-01

    Pulsars are known to emit non-thermal radio emission that is generally a power-law function of frequency. In some cases, a turnover is seen at frequencies around 100 MHz. Kijak et al. have reported the presence of a new class of `Gigahertz Peaked Spectrum' (GPS) pulsars that show spectral turnovers at frequencies around 1 GHz. We apply a model based on free-free thermal absorption to explain these turnovers in terms of surrounding material such as the dense environments found in H II regions, pulsar wind nebulae, or in cold, partially ionized molecular clouds. We show that the turnover frequency depends on the electron temperature of the environment close to the pulsar, as well as the emission measure along the line of sight. We fitted this model to the radio fluxes of known GPS pulsars and show that it can replicate the GHz turnover. From the thermal absorption model, we demonstrate that normal pulsars would exhibit a GPS-like behaviour if they were in a dense environment. We discuss the application of this model in the context of determining the population of neutron stars within the central parsec of the Galaxy. We show that a non-negligible fraction of this population might exhibit high-frequency spectral turnovers, which has implications on the detectability of these sources in the Galactic Centre.

  3. THE SPATIALLY RESOLVED H{alpha}-EMITTING WIND STRUCTURE OF P CYGNI

    SciTech Connect

    Balan, Aurelian; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hutter, D. J.; Templeton, M. E-mail: c.tycner@cmich.ed E-mail: jbenson@nofs.navy.mi E-mail: matthewt@aavso.or

    2010-06-15

    High spatial resolution observations of the H{alpha}-emitting wind structure associated with the luminous blue variable star P Cygni were obtained with the Navy Prototype Optical Interferometer. These observations represent the most comprehensive interferometric data set on P Cyg to date. We demonstrate how the apparent size of the H{alpha}-emitting region of the wind structure of P Cyg compares between the 2005, 2007, and 2008 observing seasons and how this relates to the H{alpha} line spectroscopy. Using the data sets from 2005, 2007, and 2008 observing seasons, we fit a circularly symmetric Gaussian model to the interferometric signature from the H{alpha}-emitting wind structure of P Cyg. Based on our results, we conclude that the radial extent of the H{alpha}-emitting wind structure around P Cyg is stable at the 10% level. We also show how the radial distribution of the H{alpha} flux from the wind structure deviates from a Gaussian shape, whereas a two-component Gaussian model is sufficient to fully describe the H{alpha}-emitting region around P Cyg.

  4. Gammy-Ray and Hard X-Ray Emission from Pulsar-aided Supernovae as a Probe of Particle Acceleration in Embryonic Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Kashiyama, Kazumi; Kiuchi, Kenta; Bartos, Imre

    2015-05-01

    It has been suggested that some classes of luminous supernovae (SNe) and gamma-ray bursts (GRBs) are driven by newborn magnetars. Fast-rotating proto-neutron stars have also been of interest as potential sources of gravitational waves (GWs). We show that for a range of rotation periods and magnetic fields, hard X-rays and GeV gamma rays provide us with a promising probe of pulsar-aided SNe. It is observationally known that young pulsar wind nebulae (PWNe) in the Milky Way are very efficient lepton accelerators. We argue that, if embryonic PWNe satisfy similar conditions at early stages of SNe (in ˜1-10 months after the explosion), external inverse-Compton emission via upscatterings of SN photons is naturally expected in the GeV range as well as broadband synchrotron emission. To fully take into account the Klein-Nishina effect and two-photon annihilation process that are important at early times, we perform detailed calculations including electromagnetic cascades. Our results suggest that hard X-ray telescopes such as NuSTAR can observe such early PWN emission by follow-up observations in months to years. GeV gamma-rays may also be detected by Fermi for nearby SNe, which serve as counterparts of these GW sources. Detecting the signals will give us an interesting probe of particle acceleration at early times of PWNe, as well as clues to driving mechanisms of luminous SNe and GRBs. Since the Bethe-Heitler cross section is lower than the Thomson cross section, gamma rays would allow us to study subphotospheric dissipation. We encourage searches for high-energy emission from nearby SNe, especially SNe Ibc including super-luminous objects.

  5. The very high energy characteristics of shell-type SNRs and Pulsar Wind Nebulae at different ages

    NASA Astrophysics Data System (ADS)

    Sinitsyna, V. G.; Alaverdyan, A. Y.; Andreeva, M. S.; Balygin, K. A.; Borisov, S. S.; Ivanov, I. A.; Kirichenko, A. M.; Klimov, A. I.; Kozhukhova, I. P.; Mirzafatikhov, R. M.; Moseiko, N. I.; Nikolsky, S. I.; Ostashev, I. E.; Palamarchuk, A. I.; Sinitsyna, V. Y.; Volokh, I. G.

    2016-07-01

    The investigation of VHE gamma-ray sources by any methods, including mirror Cherenkov telescopes, touches on the problem of the cosmic ray origin and, accordingly, the role of the Galaxy in their generation. The SHALON observations have yielded the results on Galactic supernova remnants of shell-type and Pulsar Wind Nebulae of different ages. For each of SNRs the observation results are presented with spectral energy distribution by SHALON in comparison with other experiment data and images by SHALON. The data obtained suggest that the very high energy 7-ray emission in the objects being discussed is different in origin

  6. CONSTRAINTS ON THE GALACTIC POPULATION OF TeV PULSAR WIND NEBULAE USING FERMI LARGE AREA TELESCOPE OBSERVATIONS

    SciTech Connect

    Acero, F.; Brandt, T. J.; Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Buehler, R.; Baldini, L.; Ballet, J.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bonamente, E.; Brigida, M.; Bruel, P. E-mail: joshualande@gmail.com E-mail: rousseau@cenbg.in2p3.fr [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS and others

    2013-08-10

    Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV {gamma}-ray emitters. Since launch, the Fermi Large Area Telescope (LAT) has identified five high-energy (100 MeV < E < 100 GeV) {gamma}-ray sources as PWNe and detected a large number of PWN candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV {gamma}-ray unidentified (UNID) sources are the best candidates for finding new PWNe. Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58 TeV PWNe and UNIDs within 5 Degree-Sign of the Galactic plane to establish new constraints on PWN properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their {gamma}-ray fluxes for energies above 10 GeV. The spectral energy distributions and upper limits, in the multi-wavelength context, also provide new information on the source nature and can help distinguish between emission scenarios, i.e., between classification as a pulsar candidate or as a PWN candidate. Six new GeV PWN candidates are described in detail and compared with existing models. A population study of GeV PWN candidates as a function of the pulsar/PWN system characteristics is presented.

  7. Preferred solar wind emitting longitudes on the sun

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.

    1977-01-01

    During the 11 1/2-year period from July 1964 through December 1975, high- and low-speed solar wind flows originated from preferred solar longitudes. The preferred longitude effect was most pronounced from 1970 onward but was also evident in the years preceding 1970. The most pronounced modulation in average solar wind speed with longitude (approximately 20%) was obtained when it was assumed that the synodic rotation period of the sun is 27.025 days. Some deep internal structure in the sun must ultimately be responsible for these long-lived longitudinal effects, which appear to rotate rigidly with the sun.

  8. PROBING THE PULSAR WIND IN THE {gamma}-RAY BINARY SYSTEM PSR B1259-63/SS 2883

    SciTech Connect

    Takata, Jumpei; Taam, Ronald E. E-mail: r-taam@northwestern.edu

    2009-09-01

    The spectral energy distribution from the X-ray to the very high energy regime (>100 GeV) has been investigated for the {gamma}-ray binary system PSR B1259-63/SS 2883 as a function of the orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100 GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fitted using two different methods. In the first method, the magnetization parameter and the Lorentz factor of the wind at the shock are allowed to vary for a given power law index characterizing the accelerated particles at the shock. In this case, the observed photon index of {approx}1.2 in the 1-10 keV energy band near the periastron passage can be understood provided that (1) the electron energy distribution is described by a broken power law and (2) there is a break at an energy of about 8 x 10{sup 6} in units of the electron rest mass energy. In the second method, the magnetization parameter and the power law index are varied for a fixed Lorentz factor. Here, the photon index of {approx}1.2 can result from a particle distribution described by a power law index of {approx}1.5. The calculated emission in the energy band corresponding to 10 MeV-1 GeV from the shocked pulsar wind indicates that these two cases can be distinguished by future Fermi observations near the periastron. It is also found that the emission from the unshocked wind could be detectable by the Fermi telescope near the periastron passage if most of

  9. Ain't no Crab, PWN Got a Brand New Bag: Correlated Radio and X-ray Structures in Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Roberts, M. S. E.; Lyutikov, M.; Gaensler, B. M.; Brogan, C. L.; Tam, C. R.; Romani, R. W.

    2005-04-01

    The traditional view of radio pulsar wind nebulae (PWN), encouraged by the Crab nebula's X-ray and radio morphologies, is that they are a result of the integrated history of their pulsars' wind. The radio emission should therefore be largely unaffected by recent pulsar activity, and hence minimally correlated with structures in the X-ray nebulae. Observations of several PWN, both stationary and rapidly moving, now show clear morphological relationships between structures in the radio and X-ray with radio intensity variations on the order of unity. We present high-resolution X-ray and radio images of several PWN of both types and discuss the morphological relationships between the two wavebands.

  10. LeRoy Apker Award: The Atmospheric Dynamics of Pulsar Companions

    NASA Astrophysics Data System (ADS)

    Jermyn, Adam

    2016-03-01

    Pulsars emit radiation over an extremely wide frequency range, from radio through gamma. Recently, systems in which this radiation significantly alters the atmospheres of low-mass pulsar companions have been discovered. These systems, ranging from ones with highly anisotropic heating to those with transient X-ray emissions, represent an exciting opportunity to investigate pulsars through the changes they induce in their companions. In this work, we present both analytic and numerical work investigating these phenomena, with a particular focus on atmospheric heat transport, transient phenomena, and the possibility of deep heating via gamma rays. We find that certain classes of binary systems may explain decadal-timescale X-ray transient phenomena, as well as the formation of so-called redback companion systems. In addition, we examine the temperature anisotropy induced by the Pulsar in its companion, and demonstrate that this may be used to infer properties of both the companion and the Pulsar wind.

  11. A FAST X-RAY DISK WIND IN THE TRANSIENT PULSAR IGR J17480-2446 IN TERZAN 5

    SciTech Connect

    Miller, Jon M.; Maitra, Dipankar; Cackett, Edward M.; Bhattacharyya, Sudip; Strohmayer, Tod E.

    2011-04-10

    Accretion disk winds are revealed in Chandra gratings spectra of black holes. The winds are hot and highly ionized (typically composed of He-like and H-like charge states) and show modest blueshifts. Similar line spectra are sometimes seen in 'dipping' low-mass X-ray binaries (LMXBs), which are likely viewed edge-on; however, that absorption is tied to structures in the outer disk, and blueshifts are not typically observed. Here, we report the detection of blueshifted He-like Fe XXV (3100 {+-} 400 km s{sup -1}) and H-like Fe XXVI (1000 {+-} 200 km s{sup -1}) absorption lines in a Chandra/HETG spectrum of the transient pulsar and LMXB IGR J17480-2446 in Terzan 5. These features indicate a disk wind with at least superficial similarities to those observed in stellar-mass black holes. The wind does not vary strongly with numerous weak X-ray bursts or flares. A broad Fe K emission line is detected in the spectrum, and fits with different line models suggest that the inner accretion disk in this system may be truncated. If the stellar magnetic field truncates the disk, a field strength of B= (0.7-4.0)x10{sup 9} G is implied, which is in line with estimates based on X-ray timing techniques. We discuss our findings in the context of accretion flows onto neutron stars and stellar-mass black holes.

  12. Detection of the Pulsar Wind Nebula HESS J1825-137 with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Grondin, M.-H.; Funk, S.; Lemoine-Goumard, M.; Van Etten, A.; Hinton, J. A.; Camilo, F.; Cognard, I.; Espinoza, C. M.; Freire, P. C. C.; Grove, J. E.; Guillemot, L.; Johnston, S.; Kramer, M.; Lande, J.; Michelson, P.; Possenti, A.; Romani, R. W.; Skilton, J. L.; Theureau, G.; Weltevrede, P.

    2011-09-01

    We announce the discovery of 1-100 GeV gamma-ray emission from the archetypal TeV pulsar wind nebula (PWN) HESS J1825-137 using 20 months of survey data from the Fermi-Large Area Telescope (LAT). The gamma-ray emission detected by the LAT is significantly spatially extended, with a best-fit rms extension of σ = 0fdg56 ± 0fdg07 for an assumed Gaussian model. The 1-100 GeV LAT spectrum of this source is well described by a power law with a spectral index of 1.38 ± 0.12 ± 0.16 and an integral flux above 1 GeV of (6.50 ± 0.21 ± 3.90) × 10-9 cm-2 s-1. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. Detailed morphological and spectral analyses bring new constraints on the energetics and magnetic field of the PWN system. The spatial extent and hard spectrum of the GeV emission are consistent with the picture of an inverse Compton origin of the GeV-TeV emission in a cooling-limited nebula powered by the pulsar PSR J1826-1334.

  13. DETECTION OF THE PULSAR WIND NEBULA HESS J1825-137 WITH THE FERMI LARGE AREA TELESCOPE

    SciTech Connect

    Grondin, M.-H.; Lemoine-Goumard, M.; Hinton, J. A.; Camilo, F.; Cognard, I.; Theureau, G.; Freire, P. C. C.; Guillemot, L.; Grove, J. E.; Johnston, S.; Possenti, A.; Skilton, J. L. E-mail: lemoine@cenbg.in2p3.fr E-mail: ave@stanford.edu

    2011-09-01

    We announce the discovery of 1-100 GeV gamma-ray emission from the archetypal TeV pulsar wind nebula (PWN) HESS J1825-137 using 20 months of survey data from the Fermi-Large Area Telescope (LAT). The gamma-ray emission detected by the LAT is significantly spatially extended, with a best-fit rms extension of {sigma} = 0.{sup 0}56 {+-} 0.{sup 0}07 for an assumed Gaussian model. The 1-100 GeV LAT spectrum of this source is well described by a power law with a spectral index of 1.38 {+-} 0.12 {+-} 0.16 and an integral flux above 1 GeV of (6.50 {+-} 0.21 {+-} 3.90) x 10{sup -9} cm{sup -2} s{sup -1}. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. Detailed morphological and spectral analyses bring new constraints on the energetics and magnetic field of the PWN system. The spatial extent and hard spectrum of the GeV emission are consistent with the picture of an inverse Compton origin of the GeV-TeV emission in a cooling-limited nebula powered by the pulsar PSR J1826-1334.

  14. The Amazing Pulsar Machine

    NASA Astrophysics Data System (ADS)

    Harding, Alice K.; Large Area Telescope, Fermi

    2014-01-01

    How rotation-powered pulsars accelerate particles to PeV energies and radiate pulsed emission from radio to gamma-ray wavelengths has remained a mystery for over 40 years. But in the last few years, the Fermi Large Area Telescope has revolutionized the study of pulsars and allowed us to peer deeper into the inner workings of this incredibly efficient natural accelerator. Thanks to Fermi discoveries, we now know that the high-energy emission is radiated in the outer magnetosphere, near the light cylinder, that millisecond pulsars are extremely efficient at emitting gamma-ray pulses and that the Crab nebula undergoes dramatic flaring that challenges particle acceleration theory. I will review how these discoveries, together with recent progress in global simulation of pulsar magnetospheres, are changing our models of pulsar particle acceleration, cascade pair production and high-energy emission.

  15. Studies of Pulsar Wind Nebula in the Supernova Remnant IC443: Preliminary Observations from the Chandra Data

    NASA Astrophysics Data System (ADS)

    Ariyibi, E. A.

    2009-10-01

    Preliminary observations of the Chandra data were made in order to study the Pulsar Wind Nebula in the Supernova Remnant IC443. The Chandra X-ray observatory short observation on IC443 was centred on 13 chip ACIS. The CIAO analytical programme was used for the data analysis. The data were separated into point source, with an energy range of 2.1 to 10.0 keV, and diffuse source with energy less than 2.1 Kev. The resulting spectra were fitted to a power law. The observed density numbers and the normalised counts of both the point source and the diffuse source were used to describe the X-ray source. Afin d'étudier la "Pulsar wind Nebula" dans le reste de la Supernova IC 443, nous avons mené une exploitation préliminaire des observations provenant du satellite spatiale Chandra. L'observation brêve de IC 443, par Chandra fut centrée sur les composantes du spectromètre identifiées par la séquence 13. Le programme informatique CIAO fut utilisé pour l'analyse des données. Les données furent groupées en sources ponctuelles, chacune ayant des énergies allant de 2.1 a 10.0 kev ; et en sources diffuses chacune avec des énergies de moins de 2.1 kev. Les spectres obtenus furent interpolés à l'aide de fonction puissance. La densité de flux ainsi que le décompte des particules induites au détecteur par le rayonnement provenant des sources ponctuelles et diffuses furent utilisés pour décrire la source de rayon-X.

  16. Observational properties of pulsars.

    PubMed

    Manchester, R N

    2004-04-23

    Pulsars are remarkable clocklike celestial sources that are believed to be rotating neutron stars formed in supernova explosions. They are valuable tools for investigations into topics such as neutron star interiors, globular cluster dynamics, the structure of the interstellar medium, and gravitational physics. Searches at radio and x-ray wavelengths over the past 5 years have resulted in a large increase in the number of known pulsars and the discovery of new populations of pulsars, posing challenges to theories of binary and stellar evolution. Recent images at radio, optical, and x-ray wavelengths have revealed structures resulting from the interaction of pulsar winds with the surrounding interstellar medium, giving new insights into the physics of pulsars. PMID:15105491

  17. A Compact X-Ray Source in the Radio Pulsar-wind Nebula G141.2+5.0

    NASA Astrophysics Data System (ADS)

    Reynolds, Stephen P.; Borkowski, Kazimierz J.

    2016-01-01

    We report the results of a 50 ks Chandra observation of the recently discovered radio object G141.2+5.0, presumed to be a pulsar-wind nebula. We find a moderately bright unresolved X-ray source that we designate CXOU J033712.8 615302 coincident with the central peak radio emission. An absorbed power-law fit to the 241 counts describes the data well, with absorbing column {N}H=6.7(4.0,9.7)× {10}21 cm-2 and photon index {{Γ }}=1.8(1.4,2.2). For a distance of 4 kpc, the unabsorbed luminosity between 0.5 and 8 keV is {1.7}-0.3+0.4× {10}32 erg s-1 (90% confidence intervals). Both LX and Γ are quite typical of pulsars in PWNe. No extended emission is seen; we estimate a conservative 3σ upper limit to the surface brightness of any X-ray PWN near the point source to be 3× {10}-17 erg cm-2 s-1 arcsec-2 between 0.5 and 8 keV, assuming the same spectrum as the point source; for a nebula of diameter 13\\prime\\prime , the flux limit is 6% of the flux of the point source. The steep radio spectrum of the PWN (α ˜ -0.7), if continued to the X-ray without a break, predicts {L}{{X}} {{(nebula)}}˜ 1× {10}33 erg s-1, so additional spectral steepening between radio and X-rays is required, as is true of all known PWNe. The high Galactic latitude gives a z-distance of 350 pc above the Galactic plane, quite unusual for a Population I object.

  18. The X-Ray Structure and Spectrum of the Pulsar Wind Nebula Surrounding PSR B1853+01 in W44

    NASA Technical Reports Server (NTRS)

    Petre, R.; Kuntz, K. D.; Shelton, R. L.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    We present the result of a Chandra ACIS observation of the pulsar PSR B1853+01 and its associated pulsar wind nebula (PWN), embedded within the supernova remnant W44. A hard band ACIS map cleanly distinguishes the PWN from the thermal emission of W44. The nebula is extended in the north-south direction, with an extent about half that of the radio emission. Morphological differences between the X-ray and radio images are apparent. Spectral fitting reveals a clear difference in spectral index between the hard emission from PSR B1853+01 (Gamma approx. 1.4) and the extended nebula (Gamma approx. 2.2). The more accurate values for the X-ray flux and spectral index are used refine estimates for PWN parameters, including magnetic field strength, the average Lorentz factor gamma of the particles in the wind, the magnetization parameter sigma, and the ratio k of electrons to other particles.

  19. The dynamic X-ray nebula powered by the pulsar B1259-63

    SciTech Connect

    Kargaltsev, Oleg; Volkov, Igor; Hare, Jeremy; Pavlov, George G.; Durant, Martin

    2014-04-01

    We present observations of the eccentric γ-ray binary B1259-63/LS 2883 with the Chandra X-ray Observatory. The images reveal a variable, extended (about 4'', or ∼1000 times the binary orbit size) structure, which appears to be moving away from the binary with the velocity of 0.05 of the speed of light. The observed emission is interpreted as synchrotron radiation from relativistic particles supplied by the pulsar. However, the fast motion through the circumbinary medium would require the emitting cloud to be loaded with a large amount of baryonic matter. Alternatively, the extended emission can be interpreted as a variable extrabinary shock in the pulsar wind outflow launched near binary apastron. The resolved variable X-ray nebula provides an opportunity to probe pulsar winds and their interaction with stellar winds in a previously inaccessible way.

  20. Radio Polarization Observations of the Snail: A Crushed Pulsar Wind Nebula in G327.1–1.1 with a Highly Ordered Magnetic Field

    NASA Astrophysics Data System (ADS)

    Ma, Y. K.; Ng, C.-Y.; Bucciantini, N.; Slane, P. O.; Gaensler, B. M.; Temim, T.

    2016-04-01

    Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the “Snail” PWN inside the supernova remnant G327.1‑1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulated PWN with a turbulence scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50%–75% provides the best match to observations. This implies substantial mixing between the SN ejecta and pulsar wind material in this system.

  1. X-Radiation from the Millisecond Pulsar J0437-4715

    NASA Technical Reports Server (NTRS)

    Zavlin, V. E.; Pavlov, G. G.; Sanwal, D.; Manchester, R. N.; Truemper, J.; Halpern, J. P.; Becker, W.

    2002-01-01

    We report on spectral and timing observations of the nearest millisecond pulsar, 50437-471 5, with the Chandra X-Ray Observatory. The pulsar spectrum, detected up to 7 keV, cannot be described by a simple one-component model. We suggest that it consists of two components: a nonthermal power-law spectrum generated in the pulsar magnetosphere, with a photon index gamma approx. = 2, and a thermal spectrum emitted by heated polar caps, with a temperature decreasing outward from 2 to 0.5 MK. The lack of spectral features in the thermal component suggests that the neutron star surface is covered by a hydrogen (or helium) atmosphere. The timing analysis shows one X-ray pulse per period, with a pulsed fraction of about 40% and the peak at the same pulse phase as the radio peak. No synchrotron pulsar-wind nebula is seen in X-rays.

  2. Pulsar Wind Nebulae as a source of the observed electron and positron excess at high energy: The case of Vela-X

    NASA Astrophysics Data System (ADS)

    Della Torre, S.; Gervasi, M.; Rancoita, P. G.; Rozza, D.; Treves, A.

    2015-12-01

    We investigate, in terms of production from pulsars and their nebulae, the cosmic ray positron and electron fluxes above ∼10 GeV, observed by the AMS-02 experiment up to 1 TeV. We concentrate on the Vela-X case. Starting from the gamma-ray photon spectrum of the source, generated via synchrotron and inverse Compton processes, we estimated the electron and positron injection spectra. Several features are fixed from observations of Vela-X and unknown parameters are borrowed from the Crab nebula. The particle spectra produced in the pulsar wind nebula are then propagated up to the Solar System, using a diffusion model. Differently from previous works, the omnidirectional intensity excess for electrons and positrons is obtained as a difference between the AMS-02 data and the corresponding local interstellar spectrum. An equal amount of electron and positron excess is observed and we interpreted this excess (above ∼100 GeV in the AMS-02 data) as a supply coming from Vela-X. The particle contribution is consistent with models predicting the gamma-ray emission at the source. The input of a few more young pulsars is also allowed, while below ∼100 GeV more aged pulsars could be the main contributors.

  3. X-RAY PHOTOIONIZED BUBBLE IN THE WIND OF VELA X-1 PULSAR SUPERGIANT COMPANION

    SciTech Connect

    Krticka, Jiri; Skalicky, Jan; Kubat, Jiri

    2012-10-01

    Vela X-1 is the archetype of high-mass X-ray binaries (HMXBs), composed of a neutron star and a massive B supergiant. The supergiant is a source of a strong radiatively driven stellar wind. The neutron star sweeps up this wind and creates a huge amount of X-rays as a result of energy release during the process of wind accretion. Here, we provide detailed NLTE models of the Vela X-1 envelope. We study how the X-rays photoionize the wind and destroy the ions responsible for the wind acceleration. The resulting decrease of the radiative force explains the observed reduction of the wind terminal velocity in a direction to the neutron star. The X-rays create a distinct photoionized region around the neutron star filled with a stagnating flow. The existence of such photoionized bubbles is a general property of HMXBs. We unveil a new principle governing these complex objects, according to which there is an upper limit to the X-ray luminosity the compact star can have without suspending the wind due to inefficient line driving.

  4. X-Ray Photoionized Bubble in the Wind of Vela X-1 Pulsar Supergiant Companion

    NASA Astrophysics Data System (ADS)

    Krtička, Jiří; Kubát, Jiří; Skalický, Jan

    2012-10-01

    Vela X-1 is the archetype of high-mass X-ray binaries (HMXBs), composed of a neutron star and a massive B supergiant. The supergiant is a source of a strong radiatively driven stellar wind. The neutron star sweeps up this wind and creates a huge amount of X-rays as a result of energy release during the process of wind accretion. Here, we provide detailed NLTE models of the Vela X-1 envelope. We study how the X-rays photoionize the wind and destroy the ions responsible for the wind acceleration. The resulting decrease of the radiative force explains the observed reduction of the wind terminal velocity in a direction to the neutron star. The X-rays create a distinct photoionized region around the neutron star filled with a stagnating flow. The existence of such photoionized bubbles is a general property of HMXBs. We unveil a new principle governing these complex objects, according to which there is an upper limit to the X-ray luminosity the compact star can have without suspending the wind due to inefficient line driving.

  5. Discovery of TeV gamma-ray emission from the pulsar wind nebula 3C 58 by MAGIC

    NASA Astrophysics Data System (ADS)

    López-Coto, Rubén

    2016-07-01

    The pulsar wind nebula (PWN) 3C 58 is one of the historical very-high-energy (VHE; E>100 GeV) gamma-ray source candidates. It has been compared to the Crab Nebula due to their morphological similarities. This object was detected by Fermi-LAT with a spectrum extending beyond 100 GeV. We analyzed 81 hours of 3C 58 data taken with the MAGIC telescopes and we detected VHE gamma-ray emission for the first time at TeV energies with a significance of 5.7 sigma and an integral flux of 0.65% C.U. above 1 TeV. According to our results 3C 58 is the least luminous PWN ever detected at VHE and the one with the lowest flux at VHE to date. We compare our results with the expectations of time-dependent models in which electrons up-scatter photon fields. The best representation favors a distance to the PWN of 2 kpc and Far Infrared (FIR) comparable to CMB photon fields. Hadronic contribution from the hosting supernova remnant (SNR) requires unrealistic energy budget given the density of the medium, disfavoring cosmic ray acceleration in the SNR as origin of the VHE gamma-ray emission.

  6. The effect of drift on the evolution of the electron/positron spectra in an axisymmetric pulsar wind nebula

    SciTech Connect

    Vorster, Michael J.; Moraal, Harm

    2014-06-20

    Charged particles propagating through a structured magnetic field are subject to drift motion. The primary aim of the present paper is therefore to investigate the effects of gradient, curvature, and neutral sheet drift on the evolution of the electron and positron spectra in a pulsar wind nebula, where the drift motion is a direct result of the magnetic field having an Archimedean spiral structure. In order to investigate the evolution of the spectra, the steady-state, axisymmetric Fokker-Planck transport equation is solved numerically using a finite-difference scheme. Apart from drift motion, the transport processes of convection and diffusion, along with the energy loss processes of adiabatic cooling and synchrotron radiation, are also included in the model. It is found that drift, particularly neutral sheet drift, can lead to a quantitative difference in the evolution of the electron and positron spectra. This difference may be of importance when interpreting the positron excess observed by PAMELA and AMS-02 near Earth.

  7. Particle-In-Cell Simulations of a Nonlinear Transverse Electromagnetic Wave in a Pulsar Wind Termination Shock

    SciTech Connect

    Skjaeraasen, Olaf; Melatos, A.; Spitkovsky, A.; /KIPAC, Menlo Park

    2005-08-15

    A 2.5-dimensional particle-in-cell code is used to investigate the propagation of a large-amplitude, superluminal, nearly transverse electromagnetic (TEM) wave in a relativistically streaming electron-positron plasma with and without a shock. In the freestreaming, unshocked case, the analytic TEM dispersion relation is verified, and the streaming is shown to stabilize the wave against parametric instabilities. In the confined, shocked case, the wave induces strong, coherent particle oscillations, heats the plasma, and modifies the shock density profile via ponderomotive effects. The wave decays over {approx}> 10{sup 2} skin depths; the decay length scale depends primarily on the ratio between the wave frequency and the effective plasma frequency, and on the wave amplitude. The results are applied to the termination shock of the Crab pulsar wind, where the decay length-scale ({approx}> 0.05''?) might be comparable to the thickness of filamentary, variable substructure observed in the optical and X-ray wisps and knots.

  8. Time-dependent modelling of pulsar wind nebulae: study on the impact of the diffusion-loss approximations

    NASA Astrophysics Data System (ADS)

    Martín, Jonatan; Torres, Diego F.; Rea, Nanda

    2012-11-01

    In this work, we present a leptonic, time-dependent model of pulsar wind nebulae (PWNe). The model seeks a solution for the lepton distribution function considering the full time-energy-dependent diffusion-loss equation. The time-dependent lepton population is balanced by injection, energy losses and escape. We include synchrotron, inverse-Compton (IC; with the cosmic-microwave background as well as with IR/optical photon fields), self-synchrotron Compton, and bremsstrahlung processes, all devoid of any radiative approximations. With this model in place we focus on the Crab nebula as an example and present its time-dependent evolution. Afterwards, we analyse the impact of different approximations made at the level of the diffusion-loss equation, as can be found in the literature. Whereas previous models ignored the escape term, e.g. with the diffusion-loss equation becoming advective, others approximated the losses as catastrophic, so that the equation has only time derivatives. Additional approximations are also described and computed. We study what the impact of these approaches is on the determination of the PWN evolution. In particular, we find the time-dependent deviation of the multi-wavelength spectrum and the best-fitting parameters obtained with the complete and the approximate models.

  9. MODELING THE MULTIWAVELENGTH LIGHT CURVES OF PSR B1259-63/LS 2883. II. THE EFFECTS OF ANISOTROPIC PULSAR WIND AND DOPPLER BOOSTING

    SciTech Connect

    Kong, S. W.; Huang, Y. F.; Cheng, K. S.

    2012-07-10

    PSR B1259-63/LS 2883 is a binary system in which a 48 ms pulsar orbits around a Be star in a high eccentric orbit with a long orbital period of about 3.4 yr. It is special for having asymmetric two-peak profiles in both the X-ray and TeV light curves. Recently, an unexpected GeV flare has been detected by the Fermi gamma-ray observatory several weeks after the last periastron passage. In this paper, we show that this observed GeV flare could be produced by the Doppler-boosted synchrotron emission in the bow-shock tail. An anisotropic pulsar wind model, which mainly affects the energy flux injection into the termination shock in a different orbital phase, is also used in this paper, and we find that the anisotropy in the pulsar wind can play a significant role in producing the asymmetric two-peak profiles in both X-ray and TeV light curves. The X-ray and TeV photons before periastron are mainly produced by the shocked electrons around the shock apex, and the light curves after periastron are contributed by the emission from the shock apex and the shock tail together, which result in asymmetric two-peak light curves.

  10. Chandra Observations of the Pulsar B1929+10 and Its Environment

    NASA Astrophysics Data System (ADS)

    Misanovic, Z.; Pavlov, G. G.; Garmire, G. P.

    2008-10-01

    We report on two Chandra observations of the 3 Myr old pulsar B1929+10, which reveal a faint compact (~9'' × 5'') nebula elongated in the direction perpendicular to the pulsar's proper motion, two patchy wings, and a possible short (~3'') jet emerging from the pulsar. In addition, we detect a tail extending up to at least 4' in the direction opposite to the pulsar's proper motion, aligned with the ~15' long tail detected in ROSAT and XMM-Newton observations. The overall morphology of the nebula suggests that the shocked pulsar wind is confined by the ram pressure due to the pulsar's supersonic speed. The shape of the compact nebula in the immediate vicinity of the pulsar seems to be consistent with the current MHD models. However, since these models do not account yet for the change of the flow velocity at larger distances from the pulsar, they are not able to constrain the extent of the long pulsar tail. The luminosity of the whole nebula as seen by Chandra is LPWN ~ 1030 ergs s-1 in the 0.3-8 keV band, for the distance of 361 pc. Using the Chandra and XMM-Newton data, we found that the pulsar spectrum is composed of nonthermal (magnetospheric) and thermal components. The nonthermal component can be described by a power-law model with photon index Γ ≈ 1.7 and luminosity LnonthPSR ≈ 1.7 × 1030 ergs s-1 in the 0.3-10 keV band. The blackbody fit for the thermal component, which presumably emerges from hot polar caps, gives the temperature kT ≈ 0.3 keV and projected emitting area A⊥ ~ 3 × 103 m2, corresponding to the bolometric luminosity Lbol ~ (1-2) × 1030 ergs s-1.

  11. THE DOUBLE PULSAR ECLIPSES. I. PHENOMENOLOGY AND MULTI-FREQUENCY ANALYSIS

    SciTech Connect

    Breton, R. P.; Kaspi, V. M.; McLaughlin, M. A.; Lyutikov, M.; Kramer, M.; Stairs, I. H.; Ransom, S. M.; Ferdman, R. D.; Camilo, F.; Possenti, A.

    2012-03-10

    The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to directly probe the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al. and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor ({approx}10{sup 5}). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov and Thompson and such a geometric connection explains that the observed periodicity is harmonically related to pulsar B's spin frequency. We observe that the eclipses require a sharp transition region beyond which the plasma density drops off abruptly. Such a region defines a plasmasphere that would be well inside the magnetospheric boundary of an undisturbed pulsar. It is also two times smaller than the expected standoff radius calculated using the balance of the wind pressure from pulsar A and the nominally estimated magnetic pressure of pulsar B.

  12. Discovery of TeV γ-ray emission from the pulsar wind nebula 3C 58 by MAGIC

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Zanin, R.

    2014-07-01

    Context. The pulsar wind nebula (PWN) 3C 58 is one of the historical very high-energy (VHE; E> 100 GeV) γ-ray source candidates. It is energized by one of the highest spin-down power pulsars known (5% of Crab pulsar) and it has been compared with the Crab nebula because of their morphological similarities. This object was previously observed by imaging atmospheric Cherenkov telescopes (Whipple, VERITAS and MAGIC), although it was not detected, with an upper limit of 2.3% Crab unit (C.U.) at VHE. It was detected by the Fermi Large Area Telescope (LAT) with a spectrum extending beyond 100 GeV. Aims: We aim to extend the spectrum of 3C 58 beyond the energies reported by the Fermi Collaboration and probe acceleration of particles in the PWN up to energies of a few tens of TeV. Methods: We analyzed 81 h of 3C 58 data taken in the period between August 2013 and January 2014 with the MAGIC telescopes. Results: We detected VHE γ-ray emission from 3C 58 with a significance of 5.7σ and an integral flux of 0.65% C.U. above 1 TeV. According to our results, 3C 58 is the least luminous VHE γ-ray PWN ever detected at VHE and has the lowest flux at VHE to date. The differential energy spectrum between 400 GeV and 10 TeV is well described by a power-law function dφ/dE = f0(E/1 TeV)-Γ with f0 = (2.0 ± 0.4stat ± 0.6sys) × 10-13 cm-2 s-1 TeV-1 and Γ = 2.4 ± 0.2stat ± 0.2sys. The skymap is compatible with an unresolved source. Conclusions: We report the first significant detection of PWN 3C 58 at TeV energies. We compare our results with the expectations of time-dependent models in which electrons upscatter photon fields. The best representation favors a distance to the PWN of 2 kpc and far-infrared (FIR) values similar to cosmic microwave background photon fields. If we consider an unexpectedly high FIR density, the data can also be reproduced by models assuming a 3.2 kpc distance. A low magnetic field, far from equipartition, is required to explain the VHE data. Hadronic

  13. The Fermi LAT Pulsars

    NASA Astrophysics Data System (ADS)

    Romani, Roger W.

    2011-08-01

    The Large Area Telescope on the Fermi satellite is an impressive pulsar discovery machine, with over 75 pulse detections and counting. The populations of radio-selected, γ-selected and millisecond pulsars are now large enough to display observational patterns in the light curves and luminosities. These patterns are starting to teach us about the physics of the emission zone, which seems dominated by open field lines near the speed of light cylinder. The sample also provides initial inferences about the pulsar population. Apparently a large fraction of neutron stars have a young energetic γ-ray emitting phase, making these objects a good probe of massive star evolution. The long-lived millisecond γ-ray pulsars are even more ubiquitous and may produce a significant fraction of the γ-ray background. In any event, it is clear that the present LAT pulsar sample is dominated by nearby objects, and there is every expectation that the number, and quality, of pulsar detections will increase in years to come.

  14. Multi-frequency observations of SNR J0453-6829 in the LMC. A composite supernova remnant with a pulsar wind nebula

    NASA Astrophysics Data System (ADS)

    Haberl, F.; Filipović, M. D.; Bozzetto, L. M.; Crawford, E. J.; Points, S. D.; Pietsch, W.; De Horta, A. Y.; Tothill, N.; Payne, J. L.; Sasaki, M.

    2012-07-01

    Context. The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs), which can be investigated in detail with radio, optical, and X-ray observations. SNR J0453-6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. Aims: We study the emission of SNR J0453-6829 to improve our understanding of its morphology, spectrum, and thus the emission mechanisms in the shell and the PWN of the remnant. Methods: We obtained new radio data with the Australia Telescope Compact Array and analysed archival XMM-Newton observations of SNR J0453-6829. We studied the morphology of SNR J0453-6829 from radio, optical, and X-ray images and investigated the energy spectra in the different parts of the remnant. Results: Our radio results confirm that this LMC SNR hosts a typical PWN. The prominent central core of the PWN exhibits a radio spectral index αCore of -0.04 ± 0.04, while in the rest of the SNR shell the spectral slope is somewhat steeper with αShell = -0.43 ± 0.01. We detect regions with a mean polarisation of P ≅ (12 ± 4)% at 6 cm and (9 ± 2)% at 3 cm. The full remnant is of roughly circular shape with dimensions of (31 ± 1) pc × (29 ± 1) pc. The spectral analysis of the XMM-Newton EPIC and RGS spectra allowed us to derive physical parameters for the SNR. Somewhat depending on the spectral model, we obtain for the remnant a shock temperature of around 0.2 keV and estimate the dynamical age to 12 000-15 000 years. Using a Sedov model we further derive an electron density in the X-ray emitting material of 1.56 cm-3, typical for LMC remnants, a large swept-up mass of 830 M⊙, and an explosion energy of 7.6 × 1050 erg. These parameters indicate a well evolved SNR with an X-ray spectrum dominated by emission from the swept-up material.

  15. G141.2+5.0, A NEW PULSAR WIND NEBULA DISCOVERED IN THE CYGNUS ARM OF THE MILKY WAY

    SciTech Connect

    Kothes, R.; Foster, T. J.; Sun, X. H.; Reich, W.

    2014-04-01

    We report the discovery of the new pulsar wind nebula (PWN) G141.2+5.0 in data observed with the Dominion Radio Astrophysical Observatory's Synthesis Telescope at 1420 MHz. The new PWN has a diameter of about 3.'5, which translates to a spatial extent of about 4 pc at a distance of 4.0 kpc. It displays a radio spectral index of α ≈ –0.7, similar to the PWN G76.9+1.1. G141.2+5.0 is highly polarized up to 40% with an average of 15% in the 1420 MHz data. It is located in the center of a small spherical H I bubble, which is expanding at a velocity of 6 km s{sup –1} at a systemic velocity of v {sub LSR} = –53 km s{sup –1}. The bubble could be the result of the progenitor star's mass loss or the shell-type supernova remnant (SNR) created by the same supernova explosion in a highly advanced stage. The systemic LSR velocity of the bubble shares the velocity of H I associated with the Cygnus spiral arm, which is seen across the second and third quadrants and an active star-forming arm immediately beyond the Perseus arm. A kinematical distance of 4 ± 0.5 kpc is found for G141.2+5.0, similar to the optical distance of the Cygnus arm (3.8 ± 1.1 kpc). G141.2+5.0 represents the first radio PWN discovered in 17 years and the first SNR discovered in the Cygnus spiral arm, which is in stark contrast with the Perseus arm's overwhelming population of shell-type remnants.

  16. Late-Time Evolution of Composite Supernova Remnants: Deep Chandra Observations and Hydrodynamical Modeling of a Crushed Pulsar Wind Nebula in SNR G327.1-1.1

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Slane, Patrick; Kolb, Christopher; Blondin, John; Hughes, John P.; Bucciantini, Niccolo

    2015-01-01

    In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock(RS) that can occur as a result of a density gradient in the ambient medium and or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a approx. 17,000 yr old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar's motion. We also show that the RSPWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to gamma-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

  17. X-Ray Analysis of the Proper Motion and Pulsar Wind Nebula for PSR J1741-2054

    NASA Technical Reports Server (NTRS)

    Auchettl, Katie; Slane, Patrick; Romani, Roger W.; Posselt, Bettina; Pavlov, George G.; Kargaltsev, Oleg; Ng, C-Y.; Temim, Tea; Weisskopf, Martin C.; Bykov, Andrei; Swartz, Douglas

    2015-01-01

    We obtained six observations of PSR J1741-2054 using the Chandra ACIS-S detector totaling approx.300 ks. By registering this new epoch of observations to an archival observation taken 3.2 yr earlier using X-ray point sources in the field of view, we have measured the pulsar proper motion at micron = 109 +/- 10 mas yr(exp. -1) in a direction consistent with the symmetry axis of the observed H(alpha) nebula. We investigated the inferred past trajectory of the pulsar but find no compelling association with OB associations in which the progenitor may have originated. We confirm previous measurements of the pulsar spectrum as an absorbed power law with photon index gamma = 2.68 +/- 0.04, plus a blackbody with an emission radius of (4.5(+3.2/-2.5))d(0.38) km, for a DM-estimated distance of 0.38d(0.38) kpc and a temperature of 61.7 +/- 3.0 eV. Emission from the compact nebula is well described by an absorbed power law model with a photon index of gamma = 1.67 +/- 0.06, while the diffuse emission seen as a trail extending northeast of the pulsar shows no evidence of synchrotron cooling. We also applied image deconvolution techniques to search for small-scale structures in the immediate vicinity of the pulsar, but found no conclusive evidence for such structures.

  18. Optical study of pulsars

    NASA Astrophysics Data System (ADS)

    Sanwal, Divas

    The Crab Pulsar emits radiation at all wavelengths from radio to extreme γ-rays including the optical. We have performed extremely high time resolution multicolor photometry of the Crab Pulsar at optical wavelengths to constrain the high energy emission models for pulsars. Our observations with 1 microsecond time resolution are a factor of 20 better than the previous best observations. We have completely resolved the peak of the main pulse of the Crab Pulsar in optical passbands. The peaks of the main pulse and the interpulse move smoothly from the rising branch to the falling branch with neither a flat top nor a cusp. We find that the peak of the Crab Pulsar main pulse in the B band arrives 140 microseconds before the peak of the radio pulse. The color of the emission changes across the phase. The maximum variation in the color ratio is about 25%. The bluest color occurs in the bridge region between the main pulse and the interpulse. The Crab Pulsar has faded by 2 +/- 2.8% since the previous observations in 1991 using the same instrument. The statistics of photon arrival times are consistent with atmospheric scintillation causing most of the variations in addition to the mean pulse variations in the shape. However, the autocorrelation function (ACF) of the Crab Pulsar light curve shows extra correlations at very short time scales. We identify two time scales, one at about 20 microseconds and another one at about 1000 microseconds at which we observe a break in the ACF. We conclude that these short timescale correlations are internal to the pulsar. We attribute the extra correlation observed in our data to microstructures. This is the first time evidence for microstructures has been observed outside the radio wavelengths. The upturn in the ACF at short time scales depends on the color. The U band shows about 10% more correlation at short time scales while the R band shows only about 3% change. We have also observed the young X-ray pulsar PSR 0656+14 at optical

  19. The Young Core-Collapse Supernova Remnant G11.2-0.3: An Asymmetric Circumstellar Medium and a Variable Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Borkowski, Kazimierz J.; Moseby, A.; Reynolds, S. P.

    2014-01-01

    G11.2-0.3 is a young supernova remnant (SNR) that has been suggested to be associated with a historical supernova of 386 AD. In addition to a bright radio and X-ray shell, it contains a pulsar wind nebula (PWN) and a 65 ms pulsar. We present first results from new deep (about 400 ks in duration) Chandra observations from 2013 May and September. Ahead of the main shell, there are a number of outlying X-ray protrusions surrounded by bow shocks, presumably produced by dense ejecta knots. Pronounced spectral variations are seen in thermal X-ray spectra of the main shell, indicating the presence of shocks with a wide range in shock speeds and large spatial variations in intervening absorption. A band of soft X-ray emission is clearly seen at the remnant's center. We interpret this band as a result of the interaction of supernova ejecta with the strongly asymmetric wind produced by a red supergiant SN progenitor shortly before its explosion. We study interstellar absorption in the central region of the remnant, finding high absorption everywhere. This rules out the association of G11.2-0.3 with SN 386. The PWN is dominated by a bright "jet" whose spatial morphology is markedly different between our May and September observations.

  20. HIGH-RESOLUTION X-RAY OBSERVATIONS OF THE PULSAR WIND NEBULA ASSOCIATED WITH THE GAMMA-RAY SOURCE HESS J1640-465

    SciTech Connect

    Lemiere, A.; Slane, P.; Murray, S.; Gaensler, B. M.

    2009-12-01

    We present a Chandra X-ray observation of the very high energy gamma-ray source HESS J1640 - 465. We identify a point source surrounded by a diffuse emission that fills the extended object previously detected by XMM-Newton at the centroid of the HESS source, within the shell of the radio supernova remnant (SNR) G338.3 - 0.0. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula (PWN) and extends asymmetrically to the southwest of a point source presented as a potential pulsar. The spectrum of the putative pulsar and compact nebula are well characterized by an absorbed power-law model which, for a reasonable N{sub H} value of 14 x 10{sup 22} cm{sup -2}, exhibit an index of 1.1 and 2.5 respectively, typical of Vela-like PWNe. We demonstrate that, given the H I absorption features observed along the line of sight, the SNR and the H II surrounding region are probably connected and lie between 8 kpc and 13 kpc. The resulting age of the system is between 10 and 30 kyr. For a 10 kpc distance (also consistent with the X-ray absorption) the 2-10 keV X-ray luminosities of the putative pulsar and nebula are L{sub PSR} approx 1.3 x 10{sup 33} d {sup 2}{sub 10kpc} erg s{sup -1} and L{sub PWN} approx 3.9 x 10{sup 33} d {sup 2}{sub 10} erg s{sup -1} (d {sub 10} = d/10 kpc). Both the flux ratio of L {sub PWN}/L{sub PSR} approx 3.4 and the total luminosity of this system predict a pulsar spin-down power around E-dotapprox4 x 10{sup 36} erg s{sup -1}. We finally consider several reasons for the asymmetries observed in the PWN morphology and discuss the potential association with the HESS source in terms of a time-dependent one-zone leptonic model.

  1. Fluctuating neutron star magnetosphere: braking indices of eight pulsars, frequency second derivatives of 222 pulsars and 15 magnetars

    NASA Astrophysics Data System (ADS)

    Ou, Z. W.; Tong, H.; Kou, F. F.; Ding, G. Q.

    2016-04-01

    Eight pulsars have low braking indices, which challenge the magnetic dipole braking of pulsars. 222 pulsars and 15 magnetars have abnormal distribution of frequency second derivatives, which also make contradiction with classical understanding. How neutron star magnetospheric activities affect these two phenomena are investigated by using the wind braking model of pulsars. It is based on the observational evidence that pulsar timing is correlated with emission and both aspects reflect the magnetospheric activities. Fluctuations are unavoidable for a physical neutron star magnetosphere. Young pulsars have meaningful braking indices, while old pulsars' and magnetars' fluctuation item dominates their frequency second derivatives. It can explain both the braking index and frequency second derivative of pulsars uniformly. The braking indices of eight pulsars are the combined effect of magnetic dipole radiation and particle wind. During the lifetime of a pulsar, its braking index will evolve from three to one. Pulsars with low braking index may put strong constraint on the particle acceleration process in the neutron star magnetosphere. The effect of pulsar death should be considered during the long term rotational evolution of pulsars. An equation like the Langevin equation for Brownian motion was derived for pulsar spin-down. The fluctuation in the neutron star magnetosphere can be either periodic or random, which result in anomalous frequency second derivative and they have similar results. The magnetospheric activities of magnetars are always stronger than those of normal pulsars.

  2. The Radio Properties and Magnetic Field Configuration in the Crab-Like Pulsar Wind Nebula G54.1+0.3

    NASA Astrophysics Data System (ADS)

    Lang, Cornelia C.; Wang, Q. Daniel; Lu, Fangjun; Clubb, Kelsey I.

    2010-02-01

    We present a multifrequency radio investigation of the Crab-like pulsar wind nebula (PWN) G54.1+0.3 using the Very Large Array. The high resolution of the observations reveals that G54.1+0.3 has a complex radio structure which includes filamentary and loop-like structures that are magnetized, a diffuse extent similar to the associated diffuse X-ray emission. But the radio and X-ray structures in the central region differ strikingly, indicating that they trace very different forms of particle injection from the pulsar and/or particle acceleration in the nebula. No spectral index gradient is detected in the radio emission across the PWN, whereas the X-ray emission softens outward in the nebula. The extensive radio polarization allows us to image in detail the intrinsic magnetic field, which is well-ordered and reveals that a number of loop-like filaments are strongly magnetized. In addition, we determine that there are both radial and toroidal components to the magnetic field structure of the PWN. Strong mid-infrared (IR) emission detected in Spitzer Space Telescope data is closely correlated with the radio emission arising from the southern edge of G54.1+0.3. In particular, the distributions of radio and X-ray emission compared with the mid-IR emission suggest that the PWN may be interacting with this interstellar cloud. This may be the first PWN where we are directly detecting its interplay with an interstellar cloud that has survived the impact of the supernova explosion associated with the pulsar's progenitor.

  3. X-RAY OBSERVATIONS OF THE SUPERNOVA REMNANT CTB 87 (G74.9+1.2): AN EVOLVED PULSAR WIND NEBULA

    SciTech Connect

    Matheson, H.; Safi-Harb, S.; Kothes, R. E-mail: samar@physics.umanitoba.ca

    2013-09-01

    Pulsar wind nebulae (PWNe) studies with the Chandra X-Ray Observatory have opened a new window to address the physics of pulsar winds, zoom on their interaction with their hosting supernova remnant (SNR) and interstellar medium, and identify their powering engines. We here present a new 70 ks, plus an archived 18 ks, Chandra ACIS observation of the SNR CTB 87 (G74.9+1.2), classified as a PWN with unusual radio properties and poorly studied in X-rays. We find that the peak of the X-ray emission is clearly offset from the peak of the radio emission by {approx}100'' and located at the southeastern edge of the radio nebula. We detect a point source-the putative pulsar-at the peak of the X-ray emission and study its spectrum separately from the PWN. This new point source, CXOU J201609.2+371110, is surrounded by a compact nebula displaying a torus-like structure and possibly a jet. A more extended diffuse nebula is offset from the radio nebula, extending from the point source to the northwest for {approx}250''. The spectra of the point source, compact nebula, and extended diffuse nebula are all well described by a power-law model with a photon index of 1.1 (0.7-1.6), 1.2 (0.9-1.4), and 1.7 (1.5-1.8), respectively, for a column density N{sub H} = 1.38 (1.21-1.57) Multiplication-Sign 10{sup 22} cm{sup -2} (90% confidence). The total X-ray luminosity of the source is {approx}1.6 Multiplication-Sign 10{sup 34} erg s{sup -1} at an assumed distance of 6.1 kpc, with {approx}2% and 6% contribution from the point source and compact nebula, respectively. The observed properties suggest that CTB 87 is an evolved ({approx}5-28 kyr) PWN, with the extended radio emission likely a ''relic'' PWN, as in Vela-X and G327.1-1.1. To date, however, there is no evidence for thermal X-ray emission from this SNR, and the SNR shell is still missing, suggesting expansion into a low-density medium (n{sub 0} < 0.2 D{sup -1/2}{sub 6.1} cm{sup -3}), likely caused by a stellar wind bubble blown by the

  4. High-Energy X-rays from J174545.5-285829, the Cannonball: a Candidate Pulsar Wind Nebula Associated with Sgr a East

    NASA Technical Reports Server (NTRS)

    Nynka, Melania; Hailey, Charles J.; Mori, Kaya; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Hong, Jaesub; Perez, Kerstin M.; Stern, Daniel; Zhang, Shuo; Zhang, William W.

    2013-01-01

    We report the unambiguous detection of non-thermal X-ray emission up to 30 keV from the Cannonball, a few arcsecond long diffuse X-ray feature near the Galactic Center, using the NuSTAR X-ray observatory. The Cannonball is a high-velocity (v(proj) approximately 500 km s(exp -1)) pulsar candidate with a cometary pulsar wind nebula (PWN) located approximately 2' north-east from Sgr A*, just outside the radio shell of the supernova remnant Sagittarius A (Sgr A) East. Its non-thermal X-ray spectrum, measured up to 30 keV, is well characterized by a Gamma is approximately 1.6 power law, typical of a PWN, and has an X-ray luminosity of L(3-30 keV) = 1.3 × 10(exp 34) erg s(exp -1). The spectral and spatial results derived from X-ray and radio data strongly suggest a runaway neutron star born in the Sgr A East supernova event. We do not find any pulsed signal from the Cannonball. The NuSTAR observations allow us to deduce the PWN magnetic field and show that it is consistent with the lower limit obtained from radio observations.

  5. A NuSTAR Observation of the Gamma-ray-emitting X-ray Binary and Transitional Millisecond Pulsar Candidate 1RXS J154439.4–112820

    NASA Astrophysics Data System (ADS)

    Bogdanov, Slavko

    2016-07-01

    I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4‑112820, which is associated with the high-energy γ-ray source 3FGL J1544.6‑1125. The system is detected up to ˜30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4‑112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270‑4859 and therefore almost certainly hosts a millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4‑112820 based on archival optical, ultraviolet, X-ray, and γ-ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.

  6. A NuSTAR Observation of the Gamma-ray-emitting X-ray Binary and Transitional Millisecond Pulsar Candidate 1RXS J154439.4–112820

    NASA Astrophysics Data System (ADS)

    Bogdanov, Slavko

    2016-07-01

    I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4‑112820, which is associated with the high-energy γ-ray source 3FGL J1544.6‑1125. The system is detected up to ∼30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4‑112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270‑4859 and therefore almost certainly hosts a millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4‑112820 based on archival optical, ultraviolet, X-ray, and γ-ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.

  7. Multi-wavelength emissions from the millisecond pulsar binary PSR J1023+0038 during an accretion active state

    SciTech Connect

    Takata, J.; Leung, Gene C. K.; Wu, E. M. H.; Cheng, K. S.; Li, K. L.; Kong, A. K. H.; Tam, P. H. T.; Hui, C. Y.; Xing, Yi; Wang, Zhongxiang; Cao, Yi; Tang, Sumin E-mail: akong@phys.nthu.edu.tw

    2014-04-20

    Recent observations strongly suggest that the millisecond pulsar binary PSR J1023+0038 has developed an accretion disk since 2013 June. We present a multi-wavelength analysis of PSR J1023+0038, which reveals that (1) its gamma-rays suddenly brightened within a few days in 2013 June/July and has remained at a high gamma-ray state for several months; (2) both UV and X-ray fluxes have increased by roughly an order of magnitude; and (3) the spectral energy distribution has changed significantly after the gamma-ray sudden flux change. Time variabilities associated with UV and X-rays are on the order of 100-500 s and 50-100 s, respectively. Our model suggests that a newly formed accretion disk, due to the sudden increase of the stellar wind, could explain the changes of all these observed features. The increase of UV is emitted from the disk, and a new component in gamma-rays is produced by inverse Compton scattering between the new UV component and pulsar wind. The increase of X-rays results from the enhancement of injection pulsar wind energy into the intra-binary shock due to the increase of the stellar wind. We also predict that the radio pulses may be blocked by the evaporated winds from the disk, and the pulsar is still powered by rotation.

  8. Identification of HESS J1303-631 as a pulsar wind nebula through γ-ray, X-ray, and radio observations

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Gérard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Grondin, M.-H.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2012-12-01

    Aims: The previously unidentified very high-energy (VHE; E > 100 GeV) γ-ray source HESS J1303-631, discovered in 2004, is re-examined including new data from the H.E.S.S. Cherenkov telescope array in order to identify this object. Archival data from the XMM-Newton X-ray satellite and from the PMN radio survey are also examined. Methods: Detailed morphological and spectral studies of VHE γ-ray emission as well as of the XMM-Newton X-ray data are performed. Radio data from the PMN survey are used as well to construct a leptonic model of the source. The γ-ray and X-ray spectra and radio upper limit are used to construct a one zone leptonic model of the spectral energy distribution (SED). Results: Significant energy-dependent morphology of the γ-ray source is detected with high-energy emission (E > 10 TeV) positionally coincident with the pulsar PSR J1301-6305 and lower energy emission (E < 2 TeV) extending 0.4° to the southeast of the pulsar. The spectrum of the VHE source can be described with a power-law with an exponential cut-off N0 = (5.6 ± 0.5) × 10-12 TeV-1 cm-2 s-1, Γ = 1.5 ± 0.2) and Ecut = (7.7 ± 2.2) TeV. The pulsar wind nebula (PWN) is also detected in X-rays, extending 2-3' from the pulsar position towards the center of the γ-ray emission region. A potential radio counterpart from the PMN survey is also discussed, showing a hint for a counterpart at the edge of the X-ray PWN trail and is taken as an upper limit in the SED. The extended X-ray PWN has an unabsorbed flux of F_2{-10 keV ˜ 1.6+0.2-0.4× 10-13 erg cm-2 s-1} and is detected at a significance of 6.5σ. The SED is well described by a one zone leptonic scenario which, with its associated caveats, predicts a very low average magnetic field for this source. Conclusions: Significant energy-dependent morphology of this source, as well as the identification of an associated X-ray PWN from XMM-Newton observations enable identification of the VHE source as an evolved PWN associated to the

  9. X-rays from the eclipsing pulsar 1957+20

    NASA Technical Reports Server (NTRS)

    Fruchter, A. S.; Bookbinder, J.; Garcia, M. R.; Bailyn, C. D.

    1992-01-01

    The detection of soft X-rays of about 1 keV energy from the eclipsing pulsar PSR1957+20 is reported. This high-energy radiation should be a valuable diagnostic of the wind in this recycled pulsar system. Possible sources of the X-ray emission are the interstellar nebula driven by the pulsar wind, the interaction between the pulsar and its evaporating companion, and the pulsar itself. The small apparent size of the X-ray object argues against the first of these possibilities and suggests that the X-rays are produced within the binary.

  10. Recycled pulsars

    NASA Astrophysics Data System (ADS)

    Jacoby, Bryan Anthony

    2005-11-01

    In a survey of ~4,150 square degrees, we discovered 26 previously unknown pulsars, including 7 "recycled" millisecond or binary pulsars. The most significant discovery of this survey is PSR J1909-3744, a 2.95 ms pulsar in an extremely circular 1.5 d orbit with a low-mass white dwarf companion. Though this system is a fairly typical low-mass binary pulsar (LMBP) system, it has several exceptional qualities: an extremely narrow pulse profile and stable rotation have enabled the most precise long-term timing ever reported, and a nearly edge-on orbit gives rise to a strong Shapiro delay which has allowed the most precise measurement of the mass of a millisecond pulsar: m p = (1.438 +/- 0.024) [Special characters omitted.] . Our accurate parallax distance measurement, d p = ([Special characters omitted.] ) kpc, combined with the mass of the optically-detected companion, m c = (0.2038 +/- 0.022) [Special characters omitted.] , will provide an important calibration for white dwarf models relevant to other LMBP companions. We have detected optical counterparts for two intermediate mass binary pulsar (IMBP) systems; taken together with optical detections and non-detections of several similar systems, our results indicate that the characteristic age t = c P /2 P consistently overestimates the time since the end of mass accretion in these recycled systems. We have measured orbital decay in the double neutron star system PSR B2127+11C in the globular cluster M15. This has allowed an improved measurement of the mass of the pulsar, m p = (1.3584 +/- 0.0097) [Special characters omitted.] , and companion, m c = (1.3544 +/- 0.0097) [Special characters omitted.] , as well as a test of general relativity at the 3% level. We find that the proper motions of this pulsar as well as PSR B2127+11A and PSR B2127+11B are consistent with each other and with one published measurement of the cluster proper motion. We have discovered three binary millisecond pulsars in the globular cluster M62

  11. First X-ray Observations of the Young Pulsar J1357-6429

    NASA Technical Reports Server (NTRS)

    Zavlin, Vyacheslav E.

    2007-01-01

    The first short Chandra and XMM-Newton observations of the young and energetic pulsar J1357-6429 provided strong indications of a tail-like pulsar-wind nebula associated with this object, as well as strong pulsations of its X-ray flux with a pulsed fraction above 40% and a thermal component dominating at lower photon energies (below 2 keV). The elongated nebular is very compact in size. about 1" x 1.5" and might be interpreted as a pulsar jet. The thermal radiation is most plausibly emitted from the entire neutron star surface of an effective temperature about 1 MK covered with a magnetized hydrogen atmosphere At higher energies the pulsar's emission is of a nonthermal (magnetospheric) origin, with a power-law spectrum of a photon index Gamma approx. equals 1.1. This makes the X-ray properties of PSR J1357-6429 very similar to those of the youngest pulsars J1119-6127 and Vela with a detected thermal radiation.

  12. The H-band emitting region of the luminous blue variable P Cygni: Spectrophotometry and interferometry of the wind

    SciTech Connect

    Richardson, N. D.; Gies, D. R.; Baron, F.; Parks, J. R.; Matson, R. A.; Touhami, Y.; Aldoretta, E. J.; McAlister, H. A.; Schaefer, G. H.; Ten Brummelaar, T. A.; Sturmann, J.; Sturmann, L.; Chesneau, O.; Monnier, J. D.; Che, X.; Clemens, D. P.; Taylor, B.; Morrison, N. D.; Kraus, S.; Ridgway, S. T.; and others

    2013-06-01

    We present the first high angular resolution observations in the near-infrared H band (1.6 μm) of the luminous blue variable star P Cygni. We obtained six-telescope interferometric observations with the CHARA Array and the MIRC beam combiner. These show that the spatial flux distribution is larger than expected for the stellar photosphere. A two-component model for the star (uniform disk) plus a halo (two-dimensional Gaussian) yields an excellent fit of the observations, and we suggest that the halo corresponds to flux emitted from the base of the stellar wind. This wind component contributes about 45% of the H-band flux and has an angular FWHM = 0.96 mas, compared to the predicted stellar diameter of 0.41 mas. We show several images reconstructed from the interferometric visibilities and closure phases, and they indicate a generally spherical geometry for the wind. We also obtained near-infrared spectrophotometry of P Cygni from which we derive the flux excess compared to a purely photospheric spectral energy distribution. The H-band flux excess matches that from the wind flux fraction derived from the two-component fits to the interferometry. We find evidence of significant near-infrared flux variability over the period from 2006 to 2010 that appears similar to the variations in the Hα emission flux from the wind.

  13. A CHANDRA X-RAY OBSERVATION OF THE BINARY MILLISECOND PULSAR PSR J1023+0038

    SciTech Connect

    Bogdanov, Slavko; Archibald, Anne M.; Kaspi, Victoria M.; Hessels, Jason W. T.; Lorimer, Duncan; McLaughlin, Maura A.; Ransom, Scott M.; Stairs, Ingrid H.

    2011-12-01

    We present a Chandra X-Ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5{sigma}) large-amplitude (factor of two to three) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. This can be naturally explained by a partial geometric occultation by the secondary star of an X-ray-emitting intrabinary shock, produced by the interaction of outflows from the two stars. The depth and duration of the eclipse imply that the intrabinary shock is localized near or at the surface of the companion star and close to the inner Lagrangian point. The energetics of the shock favor a magnetically dominated pulsar wind that is focused into the orbital plane, requiring close alignment of the pulsar spin and orbital angular momentum axes. The X-ray spectrum consists of a dominant non-thermal component and at least one thermal component, likely originating from the heated pulsar polar caps, although a portion of this emission may be from an optically thin 'corona'. We find no evidence for extended emission due to a pulsar wind nebula or bow shock down to a limiting luminosity of L{sub X} {approx}< 3.6 Multiplication-Sign 10{sup 29} erg s{sup -1} (0.3-8 keV), {approx}< 7 Multiplication-Sign 10{sup -6} of the pulsar spin-down luminosity, for a distance of 1.3 kpc and an assumed power-law spectrum with photon index {Gamma} = 1.5.

  14. Pulsar-irradiated stars in dense globular clusters

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1992-01-01

    We discuss the properties of stars irradiated by millisecond pulsars in 'hard' binaries of dense globular clusters. Irradiation by a relativistic pulsar wind as in the case of the eclipsing millisecond pulsar PSR 1957+20 alter both the magnitude and color of the companion star. Some of the blue stragglers (BSs) recently discovered in dense globular clusters can be irradiated stars in binaries containing powerful millisecond pulsars. The discovery of pulsar-driven orbital modulations of BS brightness and color with periods of a few hours together with evidence for radio and/or gamma-ray emission from BS binaries would valuably contribute to the understanding of the evolution of collapsed stars in globular clusters. Pulsar-driven optical modulation of cluster stars might be the only observable effect of a new class of binary pulsars, i.e., hidden millisecond pulsars enshrouded in the evaporated material lifted off from the irradiated companion star.

  15. Testing black hole superradiance with pulsar companions

    NASA Astrophysics Data System (ADS)

    Rosa, João G.

    2015-10-01

    We show that the magnetic dipole and gravitational radiation emitted by a pulsar can undergo superradiant scattering off a spinning black hole companion. We find that the relative amount of superradiant modes in the radiation depends on the pulsar's angular position relative to the black hole's equatorial plane. In particular, when the pulsar and black hole spins are aligned, superradiant modes are dominant at large angles, leading to an amplification of the pulsar's luminosity, whereas for small angles the radiation is dominantly composed of non-superradiant modes and the signal is attenuated. This results in a characteristic orbital modulation of the pulsar's luminosity, up to the percent level within our approximations, which may potentially yield a signature of superradiant scattering in astrophysical black holes and hence an important test of general relativity.

  16. Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Chernov, S. V.; Gwinn, C. R.; Tchekhovskoy, A. A.

    2015-10-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  17. Spin-down of Pulsars, and Their Electromagnetic and Gravitational Wave Radiations

    NASA Astrophysics Data System (ADS)

    Yue-zhu, Zhang; Yan-yan, Fu; Yi-huan, Wei; Cheng-min, Zhang; Shao-hua, Yu; Yuan-yue, Pan; Yuan-qi, Guo; De-hua, Wang

    2016-04-01

    Pulsars posses extremely strong magnetic fields, and their magnetic axis does not coincide with their rotation axis, this causes the pulsars to emit electromagnetic radiations. Pulsars rely on their rotational energy to compensate for the energy loss caused by the electromagnetic radiation, which leads to the gradually decelerated spin of pulsars. According to the theoretical deduction, we have calculated the initial period of the Crab Nebula pulsar, and derived the period evolution of the pulsar at any time in the future under the effect of the electromagnetic radiation. Considered the possible existence of quadrupole moment in the mass distribution of a pulsar, the gravitational wave radiation will also make the pulsar spin down, hence the variation of spin period of the Crab pulsar under the effect of gravitational wave radiation is further analyzed. Finally, combining the two kinds of radiation mechanisms, the evolution of spin period of the Crab pulsar under the joint action of these two kinds of radiation mechanisms is analyzed.

  18. Pulsars Magnetospheres

    NASA Technical Reports Server (NTRS)

    Timokhin, Andrey

    2012-01-01

    Current density determines the plasma flow regime. Cascades are non-stationary. ALWAYS. All flow regimes look different: multiple components (?) Return current regions should have particle accelerating zones in the outer magnetosphere: y-ray pulsars (?) Plasma oscillations in discharges: direct radio emission (?)

  19. Implications of the pulsar wind nebula scenario for a TeV gamma-ray source VER J2016+371

    NASA Astrophysics Data System (ADS)

    Saha, Lab

    2016-08-01

    We present multiwavelength studies of a TeV gamma-ray source VER J2016+371 suggested to be associated with a supernova remnant CTB 87 (G74.9+1.2) and based on X-ray and radio morphologies, CTB 87 is identified as an evolved pulsar wind nebula. A source in the vicinity of VER J2016+371 is also detected at GeV energies by Fermi Gamma Ray Space Telescope suggesting a likely counterpart at GeV energies. We find that a broken power-law (BPL) distribution of electrons can explain the observed data at radio, X-ray and TeV energies, however, is not sufficient to explain the data at MeV-GeV energies. A Maxwellian distribution of electrons along with the BPL distribution of electrons in low magnetic fields can explain the observed multiwavelength data spanned from radio to TeV energies suggesting this as the most likely scenario for this source. We also find that although the hadronic model can explain the observed GeV-TeV data for the ambient matter density of ˜ 20 cm- 3, no observational support for such high ambient density makes this hadronic scenario unlikely for this source.

  20. Implications of the pulsar wind nebula scenario for a TeV gamma-ray source VER J2016+371

    NASA Astrophysics Data System (ADS)

    Saha, Lab

    2016-08-01

    We present multiwavelength studies of a TeV gamma-ray source VER J2016+371 suggested to be associated with a supernova remnant CTB 87 (G74.9+1.2) and based on X-ray and radio morphologies, CTB 87 is identified as an evolved pulsar wind nebula. A source in the vicinity of VER J2016+371 is also detected at GeV energies by Fermi Gamma Ray Space Telescope suggesting a likely counterpart at GeV energies. We find that a broken power-law (BPL) distribution of electrons can explain the observed data at radio, X-ray and TeV energies, however, is not sufficient to explain the data at MeV--GeV energies. A Maxwellian distribution of electrons along with the BPL distribution of electrons in low magnetic fields can explain the observed multiwavelength data spanned from radio to TeV energies suggesting this as the most likely scenario for this source. We also find that although the hadronic model can explain the observed GeV--TeV data for the ambient matter density of $\\sim 20~ \\rm cm^{-3}$, no observational support for such high ambient density makes this hadronic scenario unlikely for this source.

  1. Gamma-Ray Pulsar Candidates for GLAST

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.

    2008-01-01

    The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit greater than 100 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d2, where E-dot is the energy loss due to rotational spin-down, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d2) times efficiency, assumed proportional to l/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will rely on radio and X-ray timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

  2. Gamma-Ray Pulsar Candidates for GLAST

    NASA Technical Reports Server (NTRS)

    Thompson, David J.; Smith, D. A.; Dumora, D.; Guillemot, L.; Parent, D.; Reposeur, T.; Grove, E.; Romani, R. W.; Thorsett, S. E.

    2007-01-01

    The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio Erequencies, are likely to emit greater than l00 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d^2, where E-dot is the energy loss due to rotational spindown, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d^2) times efficiency, assumed proportional to 1/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will need timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

  3. Investigating CXOU J163802.6–471358: A new pulsar wind nebula in the norma region?

    SciTech Connect

    Jakobsen, Simone J.; Watson, Darach; Tomsick, John A.; Gotthelf, Eric V.; Kaspi, Victoria M.

    2014-06-01

    We present the first analysis of the extended source CXOU J163802.6–471358, which was discovered serendipitously during the Chandra X-ray survey of the Norma region of the Galactic spiral arms. The X-ray source exhibits a cometary appearance with a point source and an extended tail region. The complete source spectrum is fitted well with an absorbed power law model and jointly fitting the Chandra spectrum of the full source with one obtained from an archived XMM-Newton observation results in best fit parameters N {sub H} =1.5{sub −0.5}{sup +0.7}×10{sup 23} cm{sup −2} and Γ=1.1{sub −0.6}{sup +0.7} (90% confidence uncertainties). The unabsorbed luminosity of the full source is then L{sub X}∼4.8×10{sup 33}d{sub 10}{sup 2} erg s{sup –1} with d {sub 10} = d/10 kpc, where a distance of 10 kpc is a lower bound inferred from the large column density. The radio counterpart found for the source using data from the Molonglo Galactic Plane Survey epoch-2 shows an elongated tail offset from the X-ray emission. No infrared counterpart was found. The results are consistent with the source being a previously unknown pulsar driving a bow shock through the ambient medium.

  4. Pulsars for the Beginner

    ERIC Educational Resources Information Center

    DiLavore, Phillip; Wayland, James R.

    1971-01-01

    Presents the history of the discovery of pulsars, observations that have been made on pulsar radiation, and theories that have been presented for its presence and origin. Illustrations using pulsar's properties are presented in mechanics, electromagnetic radiation and thermodynamics. (DS)

  5. X-ray jets from B2224+65: A Middle-aged Pulsar's New Trick

    NASA Astrophysics Data System (ADS)

    Wang, Q. Daniel; Johnson, Seth

    2015-01-01

    Pulsars, though typically not aged ones, are believed to be an important source of energetic cosmic rays. Therefore, it may not be too surprising to detect an X-ray jet associated with the middle-aged radio/X-ray pulsar B2224+65, which is well known for its very high proper motion and its trailing ``Guitar Nebula''. Most unexpected, however, is that this jet is offset from its proper motion direction by 118 degree. Furthermore, an X-ray counter jet and a faint X-ray trail associated with the ``Guitar Nebula'' are now identified in the combined data set of three epoch Chandra observations with a total exposure of 200 ks. We are carrying out a detailed measurements of the X-ray spectral variation with time and across the jets and are critically testing scenarios proposed to explain this enigmatic phenomenon. The study should have strong implications for understanding the origin of cosmic rays, as well as similar linear nonthermal X-ray-emitting features that are associated with more distant pulsars, especially pulsar wind nebula candidates in the central 100 pc region of the Galaxy.

  6. EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

    NASA Technical Reports Server (NTRS)

    Michelson, P. F.; Bertsch, D. L.; Brazier, K.; Chiang, J.; Dingus, B. L.; Fichtel, C. E.; Fierro, J.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.

    1994-01-01

    We report upper limits to the high-energy gamma-ray emission from the millisecond pulsars (MSPs) in a number of globular clusters. The observations were done as part of an all-sky survey by the energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) during Phase I of the CGRO mission (1991 June to 1992 November). Several theoretical models suggest that MSPs may be sources of high-energy gamma radiation emitted either as primary radiation from the pulsar magnetosphere or as secondary radiation generated by conversion into photons of a substantial part of the relativistic e(+/-) pair wind expected to flow from the pulsar. To date, no high-energy emission has been detected from an individual MSP. However, a large number of MSPs are expected in globular cluster cores where the formation rate of accreting binary systems is high. Model predictions of the total number of pulsars range in the hundreds for some clusters. These expectations have been reinforced by recent discoveries of a substantial number of radio MSPs in several clusters; for example, 11 have been found in 47 Tucanae (Manchester et al.). The EGRET observations have been used to obtain upper limits for the efficiency eta of conversion of MSP spin-down power into hard gamma rays. The upper limits are also compared with the gamma-ray fluxes predicted from theoretical models of pulsar wind emission (Tavani). The EGRET limits put significant constraints on either the emission models or the number of pulsars in the globular clusters.

  7. A Pulsar Eases Off the Brakes

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-10-01

    In 2006, pulsar PSR 18460258 unexpectedly launched into a series of energetic X-ray outbursts. Now a study has determined that this event may have permanently changed the behavior of this pulsar, raising questions about our understanding of how pulsars evolve.Between CategoriesA pulsar a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation can be powered by one of three mechanisms:Rotation-powered pulsars transform rotational energy into radiation, gradually slowing down in a predictable way.Accretion-powered pulsars convert the gravitational energy of accreting matter into radiation.Magnetars are powered by the decay of their extremely strong magnetic fields.Astronomical classification often results in one pesky object that doesnt follow the rules. In this case, that object is PSR 18460258, a young pulsar categorized as rotation-powered. But in 2006, PSR 18460258 suddenly emitted a series of short, hard X-ray bursts and underwent a flux increase behavior that is usually only exhibited by magnetars. After this outburst, it returned to normal, rotation-powered-pulsar behavior.Since the discovery of this event, scientists have been attempting to learn more about this strange pulsar that seems to straddle the line between rotation-powered pulsars and magnetars.Unprecedented DropOne way to examine whats going on with PSR 18460258 is to evaluate whats known as its braking index, a measure of how quickly the pulsars rotation slows down. For a rotation-powered pulsar, the braking index should be roughly constant. The pulsar then slows down according to a fixed power law, where the slower it rotates, the slower it slows down.In a recent study, Robert Archibald (McGill University) and collaborators report on 7 years worth of timing observations of PSR 18460258 after its odd magnetar-like outburst. They then compare these observations to 6.5 years of data from before the outburst. The team finds that the braking index for this bizarre

  8. Multi-wavelength analysis of young pulsars: an overview.

    NASA Astrophysics Data System (ADS)

    Maritz, J. M.; Meintjes, P. J.; Buchner, S. J.

    Young pulsars emit a broad spectrum of radiation that range from radio to gamma ray energies. These pulsars are considered as rotation powered pulsars that spin rapidly and are strongly magnetized. Following the discovery of pulsars nearly four decades ago, the population of known pulsars already reached a number of roughly two thousand. This known population of pulsars includes both millisecond and normal pulsars that were discovered by several telescopes. We analyze both HartRAO radio data and Fermi gamma ray data of the Vela pulsar. We also explore a proposed method of probing the electron column density of the instellar gas through analyzing the gamma ray diffuse data associated with the Fermi two-year observation. This paper serves as an overview of gamma ray and radio timing analysis of bright young pulsars with respect to the use of open source timing analysis tools (Tempo2, Psrchive, Enrico and the Fermi tools). We reason that the multi-wavelength picture of pulsars can help clarify questions regarding the origin of pulsed radiation emission mechanisms in several energy bands, but that radio observations will prove adequate for timing noise analysis, given the accurate and long radio data sets. The process of identifying gravitational waves in timing data, rests on gaining a deeper insight into the timing noise phenomena.

  9. New Pulsar Theory

    NASA Astrophysics Data System (ADS)

    Kebede, Legesse

    2015-08-01

    Standard pulsar theory is based on fields that are conserved from progenitor stars. This has limited the scope of pulsar astronomy to a kind of study very much confined to a limited type of pulsars, so called field pulsars. The large majority of pulsars are technically eliminated from statistical studies because they are either too massive, or are of very high magnetic field with no mechanism yet known which forces them to decay to very low frequency rotators in a matter of a few thousands of years. This is one distinct property of these highly magnetized pulsars. The current presentation focuses on a new source for the generation of pulsar fields namely spinning separated surface charges and it shows that pulsar fields are strictly mass dependent. Massive neutron stars are strongly magnetized ( ≥ 1018 G) and less massive ones are weakly magnetized (1011 - 1013 G). This work therefore dismisses the current belief that there have to be two classes of pulsars (field pulsars and anomalous pulsars). It leads to a decay law that provides results that are consistent with observations from these two so called distinct classes of pulsars. This work also suggests that pulsar fields should be infinitely multi-polar which helps to successfully addresses the longtime issues of pulse shape and promises that the current problem of pulsar radiation could be solvable..

  10. Vela Pulsar and Its Synchrotron Nebula

    NASA Astrophysics Data System (ADS)

    Helfand, D. J.; Gotthelf, E. V.; Halpern, J. P.

    2001-07-01

    We present high-resolution Chandra X-ray observations of PSR B0833-45, the 89 ms pulsar associated with the Vela supernova remnant. We have acquired two observations separated by 1 month to search for changes in the pulsar and its environment following an extreme glitch in its rotation frequency. We find a well-resolved nebula with a toroidal morphology remarkably similar to that observed in the Crab Nebula, along with an axial Crab-like jet. Between the two observations, taken ~3×105 s and ~3×106 s after the glitch, the flux from the pulsar is found to be steady to within 0.75% the 3 σ limit on the fractional increase in the pulsar's X-ray flux is <~10-5 of the inferred glitch energy. We use this limit to constrain parameters of glitch models and neutron star structure. We do find a significant increase in the flux of the nebula's outer arc; if associated with the glitch, the inferred propagation velocity is >~0.7c, similar to that seen in the brightening of the Crab Nebula wisps. We propose an explanation for the X-ray structure of the Vela synchrotron nebula based on a model originally developed for the Crab Nebula. In this model, the bright X-ray arcs are the shocked termination of a relativistic equatorial pulsar wind that is contained within the surrounding kidney-bean shaped synchrotron nebula comprising the postshock, but still relativistic, flow. In a departure from the Crab model, the magnetization parameter σ of the Vela pulsar wind is allowed to be of order unity; this is consistent with the simplest MHD transport of magnetic field from the pulsar to the nebula, where B<=4×10-4 G. The inclination angle of the axis of the equatorial torus with respect to the line of sight is identical to that of the rotation axis of the pulsar as previously measured from the polarization of the radio pulse. The projection of the rotation axis on the sky may also be close to the direction of proper motion of the pulsar if previous radio measurements were confused by

  11. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1977-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived, using a uniform sample of pulsars detected during a 408-MHz pulsar survey at Jodrell Bank. There are indications of a fine-scale structure in the spatial distributions and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in our galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy has been estimated and used to derive the pulsar birthrate.

  12. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1976-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived using a uniform sample of pulsars detected during a 408 MHz pulsar survey at Jodrell Bank. There are indications of a fine scale structure in the spatial distribution and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in the galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy was estimated and used to derive the pulsar birthrate.

  13. The Vela Pulsar and Its Synchrotron Nebula

    NASA Astrophysics Data System (ADS)

    Helfand, D.; Gotthelf, E.; Halpern, J.

    2000-10-01

    We present high-resolution Chandra X-ray observations of PSR0833-45, the 89 ms pulsar associated with the Vela supernova remnant. We have acquired two observations of the pulsar separated by one month to search for morphological changes in the pulsar and its environment following an extreme glitch in its rotation frequency. We find a well-resolved nebula with a morphology remarkably similar to the torus-like structure observed in the Crab Nebula, along with an axial Crab-like jet. The flux from the pulsar is found to be steady to within 0.75 %; the 3 sigma limit on the fractional increase in the pulsar's X-ray flux is <10-5 of the inferred glitch energy. We use this limit to constrain parameters of glitch models and neutron star structure. We do find a significant increase in the flux of the nebula's outer torus; if associated with the glitch, the inferred propogation velocity is ~0.5c, similar to that seen in the brightening of the Crab Nebula wisps. We propose an explanation for the X-ray structure of the Vela synchrotron nebula based on a model originally developed for the Crab Nebula. In this model, the bright, arc-shaped X-ray wisps are the shocked termination of a relativistic equatorial pulsar wind which is contained within the surrounding kidney-bean shaped synchrotron nebula which comprises the post-shock, but still relativistic, flow. In a departure from the Crab model, the magnetization parameter of the Vela pulsar wind is required to be of order unity; this is consistent with the simplest MHD transport of magnetic field from the pulsar to the nebula, where B ~ 4 x 10-4G.

  14. Radio pulsar disk electrodynamics

    NASA Technical Reports Server (NTRS)

    Michel, F. C.

    1983-01-01

    Macroscopic physics are discussed for the case of a disk close to an isolated, magnetized, rotating neutron star that acts as a Faraday disk dynamo, while the disk acts as both a load and a neutral sheet. This sheet allows the polar cap current to return to the neutron star, splitting a dipolar field into two monopolar halves. The dominant energy loss is from the stellar wind torque, and the next contribution is dissipation in the auroral zones, where the current returns to the star in a 5 cm-thick sheet. The disk itself may be a source of visible radiation comparable to that in pulsed radio frequency emission. As the pulsar ages, the disk expands and narrows into a ring which, it is suggested, may lead to a cessation of pulsed emission at periods of a few sec.

  15. Pulsar Astronomy with GLAST

    SciTech Connect

    Thorsett, Stephen

    2005-09-12

    Despite their name, the rotation powered neutron stars called "radio pulsars" are actually most luminous in the hard x-ray and gamma-ray bands. GLAST will be the first high-energy satellite with sufficient sensitivity to detect and study large numbers of these pulsars. I will review GLAST's key science goals in pulsar astrophysics and summarize the extraordinary advances in low-energy pulsar surveys since the days of CGRO.

  16. CHANGES IN THE CRAB PULSAR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Scientists are learning more about how pulsars work by studying a series of Hubble Space Telescope images of the heart of the Crab Nebula. The images, taken over a period of several months, show that the Crab is a far more dynamic object than previously understood. At the center of the nebula lies the Crab Pulsar. The pulsar is a tiny object by astronomical standards -- only about six miles across -- but has a mass greater than that of the Sun and rotates at a rate of 30 times a second. As the pulsar spins its intense magnetic field whips around, acting like a sling shot, accelerating subatomic particles and sending them hurtling them into space at close to the speed of light. The tiny pulsar and its wind are the powerhouse for the entire Crab Nebula, which is 10 light-years across -- a feat comparable to an object the size of a hydrogen atom illuminating a volume of space a kilometer across. The three pictures shown here, taken from the series of Hubble images, show dramatic changes in the appearance of the central regions of the nebula. These include wisp-like structures that move outward away from the pulsar at half the speed of light, as well as a mysterious 'halo' which remains stationary, but grows brighter then fainter over time. Also seen are the effects of two polar jets that move out along the rotation axis of the pulsar. The most dynamic feature seen -- a small knot that 'dances around' so much that astronomers have been calling it a 'sprite' -- is actually a shock front (where fast-moving material runs into slower-moving material)in one of these polar jets. The telescope captured the images with the Wide Field and Planetary Camera 2 using a filter that passes light of wavelength around 550 nanometers, near the middle of the visible part of the spectrum. The Crab Nebula is located 7,000 light-years away in the constellation Taurus. Credit: Jeff Hester and Paul Scowen (Arizona State University), and NASA

  17. Timing and Interstellar Scattering of 35 Distant Pulsars Discovered in the PALFA Survey

    NASA Astrophysics Data System (ADS)

    Nice, D. J.; Altiere, E.; Bogdanov, S.; Cordes, J. M.; Farrington, D.; Hessels, J. W. T.; Kaspi, V. M.; Lyne, A. G.; Popa, L.; Ransom, S. M.; Sanpa-arsa, S.; Stappers, B. W.; Wang, Y.; Allen, B.; Bhat, N. D. R.; Brazier, A.; Camilo, F.; Champion, D. J.; Chatterjee, S.; Crawford, F.; Deneva, J. S.; Desvignes, G.; Freire, P. C. C.; Jenet, F. A.; Knispel, B.; Lazarus, P.; Lee, K. J.; van Leeuwen, J.; Lorimer, D. R.; Lynch, R.; McLaughlin, M. A.; Scholz, P.; Siemens, X.; Stairs, I. H.; Stovall, K.; Venkataraman, A.; Zhu, W.

    2013-07-01

    We have made extensive observations of 35 distant slow (non-recycled) pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Timing observations of these pulsars over several years at Arecibo Observatory and Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation properties. Despite being a relatively distant population, these pulsars have properties that mirror those of the previously known pulsar population. Many of the sources exhibit timing noise, and one underwent a small glitch. We have used multifrequency data to measure the interstellar scattering properties of these pulsars. We find scattering to be higher than predicted along some lines of sight, particularly in the Cygnus region. Finally, we present XMM-Newton and Chandra observations of the youngest and most energetic of the pulsars, J1856+0245, which has previously been associated with the GeV-TeV pulsar wind nebula HESS J1857+026.

  18. TIMING AND INTERSTELLAR SCATTERING OF 35 DISTANT PULSARS DISCOVERED IN THE PALFA SURVEY

    SciTech Connect

    Nice, D. J.; Altiere, E.; Farrington, D.; Popa, L.; Wang, Y.; Bogdanov, S.; Camilo, F.; Cordes, J. M.; Brazier, A.; Chatterjee, S.; Hessels, J. W. T.; Kaspi, V. M.; Lyne, A. G.; Stappers, B. W.; Ransom, S. M.; Sanpa-arsa, S.; Allen, B.; Bhat, N. D. R.; Champion, D. J.; Crawford, F.; and others

    2013-07-20

    We have made extensive observations of 35 distant slow (non-recycled) pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Timing observations of these pulsars over several years at Arecibo Observatory and Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation properties. Despite being a relatively distant population, these pulsars have properties that mirror those of the previously known pulsar population. Many of the sources exhibit timing noise, and one underwent a small glitch. We have used multifrequency data to measure the interstellar scattering properties of these pulsars. We find scattering to be higher than predicted along some lines of sight, particularly in the Cygnus region. Finally, we present XMM-Newton and Chandra observations of the youngest and most energetic of the pulsars, J1856+0245, which has previously been associated with the GeV-TeV pulsar wind nebula HESS J1857+026.

  19. A novel mechanism for creating double pulsars

    NASA Technical Reports Server (NTRS)

    Sigurdsson, Steinn; Hernquist, Lars

    1992-01-01

    Simulations of encounters between pairs of hard binaries, each containing a neutron star and a main-sequence star, reveal a new formation mechanism for double pulsars in dense cores of globular clusters. In many cases, the two normal stars are disrupted to form a common envelope around the pair of neutron stars, both of which will be spun up to become millisecond pulsars. We predict that a new class of pulsars, double millisecond pulsars, will be discovered in the cores of dense globular clusters. The genesis proceeds through a short-lived double-core common envelope phase, with the envelope ejected in a fast wind. It is possible that the progenitor may also undergo a double X-ray binary phase. Any circular, short-period double pulsar found in the galaxy would necessarily come from disrupted disk clusters, unlike Hulse-Taylor class pulsars or low-mass X-ray binaries which may be ejected from clusters or formed in the galaxy.

  20. Pulsar Search Results from the Arecibo Remote Command Center

    NASA Astrophysics Data System (ADS)

    Rodriguez, Miguel; Stovall, Kevin; Banaszak, Shawn A.; Becker, Alison; Biwer, Christopher M.; Boehler, Keith; Caballero, Keeisi; Christy, Brian; Cohen, Stephanie; Crawford, Fronefield; Cuellar, Andres; Danford, Andrew; Percy Dartez, Louis; Day, David; Flanigan, Joseph D.; Fonrouge, Aldo; Gonzalez, Adolfo; Gustavson, Kathy; Handzo, Emma; Hinojosa, Jesus; Jenet, Fredrick A.; Kaplan, David L. A.; Lommen, Andrea N.; Longoria, Chasity; Lopez, Janine; Lunsford, Grady; Mahany, Nicolas; Martinez, Jose; Mata, Alberto; Miller, Andy; Murray, James; Pankow, Chris; Ramirez, Ivan; Reser, Jackie; Rojas, Pablo; Rohr, Matthew; Rolph, Kristina; Rose, Caitlin; Rudnik, Philip; Siemens, Xavier; Tellez, Andrea; Tillman, Nicholas; Walker, Arielle; Wells, Bradley L.; Zaldivar, Jonathan; Zermeno, Adrienne; Gbncc Consortium, Palfa Consortium, Gbtdrift Consortium, Ao327 Consortium

    2015-01-01

    This poster presents the pulsar discoveries made by students in the Arecibo Remote Command Center (ARCC) program. The ARCC program was started at the University of Texas - Brownsville (UTB) within the Center for Advanced Radio Astronomy (CARA) as a group of scientists, faculty, graduate, undergraduate, and high school students interested in astrophysics. It has since expanded to form other ARCC programs at the University of Wisconsin-Milwaukee (UWM) and Franklin and Marshall College (F&M). The students in the ARCC group control the world's largest radio telescopes to search and discover pulsars. Pulsars are exotic neutron stars that emit beams of electromagnetic radiation. ARCC students use a web application to view and rate the images of radio pulsar candidates based on their signal characteristics. To date, ARCC students have searched through thousands of candidates and have discovered 61 pulsars to date.

  1. The pulsar B2224+65 and its jets: a two epoch X-ray analysis

    NASA Astrophysics Data System (ADS)

    Johnson, S. P.; Wang, Q. D.

    2010-10-01

    We present an X-ray morphological and spectroscopic study of the pulsar B2224+65 and its apparent jet-like X-ray features based on two epoch Chandra observations. The main X-ray feature, which shows a large directional offset from the ram-pressure confined pulsar wind nebula (Guitar nebula), is broader in apparent width and shows evidence for spectral hardening (at 95 per cent confidence) in the second epoch compared to the first. Furthermore, the sharp leading edge of the feature is found to have a proper motion consistent with that of the pulsar (~180 mas yr-1). The combined data set also provides evidence for the presence of a counter feature, albeit substantially fainter and shorter than the main one. Additional spectral trends along the major and minor axes of the feature are only marginally detected in the two epoch data, including softening counter to the direction of proper motion. Possible explanations for the X-ray features include diffuse energetic particles being confined by an organized ambient magnetic field as well as a simple ballistic jet interpretation; however, the former may have difficulty in explaining observed spectral trends between epochs and along the feature's major axis, whereas the latter may struggle to elucidate its linearity. Given the low counting statistics available in the two epoch observations, it remains difficult to determine a physical production scenario for these enigmatic X-ray emitting features with any certainty.

  2. MULTIWAVELENGTH CONSTRAINTS ON PULSAR POPULATIONS IN THE GALACTIC CENTER

    SciTech Connect

    Wharton, R. S.; Chatterjee, S.; Cordes, J. M.; Deneva, J. S.; Lazio, T. J. W.

    2012-07-10

    The detection of radio pulsars within the central few parsecs of the Galaxy would provide a unique probe of the gravitational and magneto-ionic environments in the Galactic center (GC) and, if close enough to Sgr A*, precise tests of general relativity in the strong-field regime. While it is difficult to find pulsars at radio wavelengths because of interstellar scattering, the payoff from detailed timing of pulsars in the GC warrants a concerted effort. To motivate pulsar surveys and help define search parameters for them, we constrain the pulsar number and spatial distribution using a wide range of multiwavelength measurements. These include the five known radio pulsars within 15' of Sgr A*, non-detections in high-frequency pulsar surveys of the central parsec, radio and gamma-ray measurements of diffuse emission, a catalog of radio point sources from an imaging survey, infrared observations of massive star populations in the central few parsecs, candidate pulsar wind nebulae in the inner 20 pc, and estimates of the core-collapse supernova rate based on X-ray measurements. We find that under current observational constraints, the inner parsec of the Galaxy could harbor as many as {approx}10{sup 3} active radio pulsars that are beamed toward Earth. Such a large population would distort the low-frequency measurements of both the intrinsic spectrum of Sgr A* and the free-free absorption along the line of sight of Sgr A*.

  3. Multiwavelength Constraints on Pulsar Populations in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Wharton, R. S.; Chatterjee, S.; Cordes, J. M.; Deneva, J. S.; Lazio, T. J. W.

    2012-07-01

    The detection of radio pulsars within the central few parsecs of the Galaxy would provide a unique probe of the gravitational and magneto-ionic environments in the Galactic center (GC) and, if close enough to Sgr A*, precise tests of general relativity in the strong-field regime. While it is difficult to find pulsars at radio wavelengths because of interstellar scattering, the payoff from detailed timing of pulsars in the GC warrants a concerted effort. To motivate pulsar surveys and help define search parameters for them, we constrain the pulsar number and spatial distribution using a wide range of multiwavelength measurements. These include the five known radio pulsars within 15' of Sgr A*, non-detections in high-frequency pulsar surveys of the central parsec, radio and gamma-ray measurements of diffuse emission, a catalog of radio point sources from an imaging survey, infrared observations of massive star populations in the central few parsecs, candidate pulsar wind nebulae in the inner 20 pc, and estimates of the core-collapse supernova rate based on X-ray measurements. We find that under current observational constraints, the inner parsec of the Galaxy could harbor as many as ~103 active radio pulsars that are beamed toward Earth. Such a large population would distort the low-frequency measurements of both the intrinsic spectrum of Sgr A* and the free-free absorption along the line of sight of Sgr A*.

  4. Observing peculiar γ-ray pulsars with AGILE

    NASA Astrophysics Data System (ADS)

    Pilia, M.; Pellizzoni, A.

    2011-08-01

    The AGILE γ-ray satellite provides large sky exposure levels (>=109 cm2 s per year on the Galactic Plane) with sensitivity peaking at E ~100 MeV where the bulk of pulsar energy output is typically released. Its ~1 μs absolute time tagging capability makes it perfectly suited for the study of γ-ray pulsars. AGILE collected a large number of γ-ray photons from EGRET pulsars (>=40,000 pulsed counts for Vela) in two years of observations unveiling new interesting features at sub-millisecond level in the pulsars' high-energy light-curves, γ-ray emission from pulsar glitches and Pulsar Wind Nebulae. AGILE detected about 20 nearby and energetic pulsars with good confidence through timing and/or spatial analysis. Among the newcomers we find pulsars with very high rotational energy losses, such as the remarkable PSR B1509-58 with a magnetic field in excess of 1013 Gauss, and PSR J2229+6114 providing a reliable identification for the previously unidentified EGRET source 3EG2227+6122. Moreover, the powerful millisecond pulsar B1821-24, in the globular cluster M28, is detected during a fraction of the observations.

  5. ACCELERATING HIGH-ENERGY PULSAR RADIATION CODES

    SciTech Connect

    Venter, C.; De Jager, O. C.

    2010-12-20

    Curvature radiation (CR) is believed to be a dominant mechanism for creating gamma-ray emission from pulsars and is emitted by relativistic particles that are constrained to move along curved magnetic field lines. Additionally, synchrotron radiation (SR) is expected to be radiated by both relativistic primaries (involving cyclotron resonant absorption of radio photons and re-emission of SR photons), or secondary electron-positron pairs (created by magnetic or photon-photon pair production processes involving CR gamma rays in the pulsar magnetosphere). When calculating these high-energy spectra, especially in the context of pulsar population studies where several millions of CR and SR spectra have to be generated, it is profitable to consider approximations that would save computational time without sacrificing too much accuracy. This paper focuses on one such approximation technique, and we show that one may gain significantly in computational speed while preserving the accuracy of the spectral results.

  6. Very-high-energy gamma-ray observations of pulsar wind nebulae and cataclysmic variable stars with MAGIC and development of trigger systems for IACTs

    NASA Astrophysics Data System (ADS)

    Lopez-Coto, Ruben

    2015-07-01

    lowest possible energy threshold with the LSTs of CTA. Together with this work, the trigger of the MAGIC telescopes was improved. We have simulated, tested and commissioned a new concept of stereoscopic trigger. This new system, that uses the information of the position of the showers on each of the MAGIC cameras, is dubbed "Topo-trigger". The scientific fraction of the thesis deals with galactic sources observed with the MAGIC telescopes. In Part III, I talk about the analysis of the VHE γ-ray emission of Pulsar Wind Nebulae (PWNe): the discovery of VHE γ-ray emission from the puzzling PWN 3C 58, the likely remnant of the SN 1181 AD and the weakest PWN detected at VHE to date; the characterization of the VHE tail of the Crab nebula by observing it at the highest zenith angles; and the search for an additional inverse Compton component during the Crab nebula flares reported by Fermi-LAT in the synchrotron regime. Part IV is concerned with searches for VHE γ-ray emission of cataclysmic variable stars. I studied, on a multiwavelength context, the VHE γ-ray nature of the previously claimed pulsed γ-ray emission of the cataclysmic variable AE Aqr. I also performed observations of novae and a dwarf nova to pinpoint the ac- celeration mechanisms taking place in this kind of objects and to discover a putative hadronic component of the soft γ-ray emission. A conclusion chapter summarizes all the work performed and lists prospects related with the topics treated in this thesis.

  7. High-Energy Pulsar Models: Developments and New Questions

    NASA Technical Reports Server (NTRS)

    Venter, C.; Harding, A. K.

    2014-01-01

    our understanding of particle acceleration, emission, and magnetosphere geometry. One may now also study evolutionary trends of the measured or inferred quantities, and probe pulsar visibility and population properties such as radiation beam sizes of different pulsar classes, as well as the distribution of spin-down power, gamma-ray luminosity, conversion efficiency, spectral index, and cutoff energy across the population. Lastly, the recent detection of very-high-energy (VHE) pulsations from the Crab pulsar generated quite a few ideas to explain this emission, leading to an extension of standard models and possibly even a bridge between the physics of pulsars and pulsar wind nebulae (PWNe).

  8. High-energy pulsar models: Developments and new questions

    NASA Astrophysics Data System (ADS)

    Venter, C.; Harding, A. K.

    2014-03-01

    understanding of particle acceleration, emission, and magnetosphere geometry. One may now also study evolutionary trends of the measured or inferred quantities, and probe pulsar visibility and population properties such as radiation beam sizes of different pulsar classes, as well as the distribution of spin-down power, γ-ray luminosity, conversion efficiency, spectral index, and cutoff energy across the population. Lastly, the recent detection of very-high-energy (VHE) pulsations from the Crab pulsar generated quite a few ideas to explain this emission, leading to an extension of standard models and possibly even a bridge between the physics of pulsars and pulsar wind nebulae (PWNe).

  9. The 3D Space and Spin Velocities of a Gamma-ray Pulsar

    NASA Astrophysics Data System (ADS)

    Romani, Roger W.

    2016-04-01

    PSR J2030+4415 is a LAT-discovered 0.5My-old gamma-ray pulsar with an X-ray synchrotron trail and a rare Halpha bowshock. We have obtained GMOS IFU spectroscopic imaging of this shell, and show a sweep through the remarkable Halpha structure, comparing with the high energy emission. These data provide a unique 3D map of the momentum distribution of the relativistic pulsar wind. This shows that the pulsar is moving nearly in the plane of the sky and that the pulsar wind has a polar component misaligned with the space velocity. The spin axis is shown to be inclined some 95degrees to the Earth line of sight, explaining why this is a radio-quiet, gamma-only pulsar. Intriguingly, the shell also shows multiple bubbles that suggest that the pulsar wind power has varied substantially over the past 500 years.

  10. Pulsar Radiation Models - Radio to High Energies

    NASA Astrophysics Data System (ADS)

    Venter, Christo; Harding, Alice

    Rotation-powered pulsars emit over nearly 19 decades of energy. Although an all-encompassing answer as to the origin of this broad-band emission remains elusive nearly 50 years after their discovery, the theorist does have a few tools in his / her toolkit to aid investigation. Phase-averaged spectra give clues as to the emitting particles, their acceleration, environment, and the radiation mechanism. Moreover, the phase-evolution of spectra constrains the radiation energetics and environment as different parts of the magnetosphere are exposed to the observer during the pulsar's rotation. A detailed model furthermore critically depends on the specification of the emission geometry. Modeling the light curves probes this fundamental geometric assumption, which is closely tied to the posited magnetospheric structure. Studying many versions of the same system helps to constrain critical population-averaged quantities, discover population trends, and probe model performance for different regions of phase space. When coupled with population synthesis, such modeling can provide powerful discrimination between competing emission models. Polarization properties may provide complementary constraints on the magnetic field orientation and pulsar geometry. Lastly, comparison of parameters inferred from independent models for the different wavebands yields necessary crosschecks. It is indeed fortunate that the past few years have witnessed an incredible increase in number and improved characterization of rotation-powered pulsars. We will review how the enhanced quality and quantity of data are providing impetus for further model refinement.

  11. BOOK REVIEW: Rotation and Accretion Powered Pulsars

    NASA Astrophysics Data System (ADS)

    Kaspi, V. M.

    2008-03-01

    Pulsar astrophysics has come a long way in the 40 years since the discovery of the first pulsar by Bell and Hewish. From humble beginnings as bits of 'scruff' on the Cambridge University group's chart recorder paper, the field of pulsars has blossomed into a major area of mainstream astrophysics, with an unparalleled diversity of astrophysical applications. These range from Nobel-celebrated testing of general relativity in the strong-field regime to constraining the equation-of-state of ultradense matter; from probing the winds of massive stars to globular cluster evolution. Previous notable books on the subject of pulsars have tended to focus on some particular topic in the field. The classic text Pulsars by Manchester and Taylor (1977 San Francisco, CA: Freeman) targeted almost exclusively rotation-powered radio pulsars, while the Mészáros book High-Energy Radiation from Magnetized Neutron Stars (1992 Chicago, IL: University of Chicago Press) considered both rotation- and accretion-powered neutron stars, but focused on their radiation at x-ray energies and above. The recent book Neutron Stars 1 by Haensel et al (2007 Berlin: Springer) considers only the equation of state and neutron-star structure. Into this context appears Rotation and Accretion Powered Pulsars, by Pranab Ghosh. In contrast to other books, here the author takes an encyclopedic approach and attempts to synthesize practically all of the major aspects of the two main types of neutron star. This is ambitious. The only comparable undertaking is the useful but more elementary Lyne and Graham-Smith text Pulsar Astronomy (1998 Cambridge: Cambridge University Press), or Compact Stellar X-ray Sources (eds Lewin and van der Klis, 2006 Cambridge: Cambridge University Press), an anthology of technical review articles that also includes black hole topics. Rotation and Accretion Powered Pulsars thus fills a clear void in the field, providing a readable, graduate-level book that covers nearly everything you

  12. Gravitational wave emission from oscillating millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Alford, Mark G.; Schwenzer, Kai

    2015-02-01

    Neutron stars undergoing r-mode oscillation emit gravitational radiation that might be detected on the Earth. For known millisecond pulsars the observed spin-down rate imposes an upper limit on the possible gravitational wave signal of these sources. Taking into account the physics of r-mode evolution, we show that only sources spinning at frequencies above a few hundred Hertz can be unstable to r-modes, and we derive a more stringent universal r-mode spin-down limit on their gravitational wave signal. We find that this refined bound limits the gravitational wave strain from millisecond pulsars to values below the detection sensitivity of next generation detectors. Young sources are therefore a more promising option for the detection of gravitational waves emitted by r-modes and to probe the interior composition of compact stars in the near future.

  13. About pulsars dynamical evolution

    NASA Astrophysics Data System (ADS)

    López-Valdivia, R.; Álvarez, C.; de La Fuente, E.; Lorimer, D.; Kramer, M.

    2011-10-01

    Based on the assumption that pulsars are losing their rotational energy according to dot{ν}=-kν^n where ν is the frequency, dot{ν} its first derivative, and n is the braking index, four evolutionary models are created. Using them, thousands of artificial pulsar populations were generated. A comparison between these populations, and the no glitches and no milisecond pulsars reported by Hobbs et al. (2004) is performed using a Kolmogorov-Smirnov test (K-S).

  14. Revised Pulsar Spindown

    SciTech Connect

    Contopoulos, Ioannis; Spitkovsky, Anatoly; /KIPAC, Menlo Park

    2005-12-14

    We address the issue of electromagnetic pulsar spindown by combining our experience from the two limiting idealized cases which have been studied in great extent in the past: that of an aligned rotator where ideal MHD conditions apply, and that of a misaligned rotator in vacuum. We construct a spindown formula that takes into account the misalignment of the magnetic and rotation axes, and the magnetospheric particle acceleration gaps. We show that near the death line aligned rotators spin down much slower than orthogonal ones. In order to test this approach, we use a simple Monte Carlo method to simulate the evolution of pulsars and find a good fit to the observed pulsar distribution in the P-{dot P} diagram without invoking magnetic field decay. Our model may also account for individual pulsars spinning down with braking index n < 3, by allowing the corotating part of the magnetosphere to end inside the light cylinder. We discuss the role of magnetic reconnection in determining the pulsar braking index. We show, however, that n {approx} 3 remains a good approximation for the pulsar population as a whole. Moreover, we predict that pulsars near the death line have braking index values n > 3, and that the older pulsar population has preferentially smaller magnetic inclination angles. We discuss possible signatures of such alignment in the existing pulsar data.

  15. Gamma-Ray Pulsars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2011-01-01

    The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the detection of over 80 gamma-ray pulsars. Several new populations have been discovered, including 24 radio quiet pulsars found through gamma-ray pulsations alone and about 20 millisecond gamma-ray pulsars. The gamma-ray pulsations from millisecond pulsars were discovered by both folding at periods of known radio millisecond pulsars or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -35 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. The higher sensitivity and larger energy range of the Fermi Large Area Telescope has produced detailed energy-dependent light curves and phase-resolved spectroscopy on brighter pulsars, that have ruled out polar cap models as the major source of the emission in favor of outer magnetosphere accelerators. The large number of gamma-ray pulsars now allows for the first time meaningful population and sub-population studies that are revealing surprising properties of these fascinating sources.

  16. Do asteroids evaporate near pulsars? Induction heating by pulsar waves revisited

    NASA Astrophysics Data System (ADS)

    Kotera, Kumiko; Mottez, Fabrice; Voisin, Guillaume; Heyvaerts, Jean

    2016-07-01

    Aims: We investigate the evaporation of close-by pulsar companions, such as planets, asteroids, and white dwarfs, by induction heating. Methods: Assuming that the outflow energy is dominated by a Poynting flux (or pulsar wave) at the location of the companions, we calculate their evaporation timescales, by applying the Mie theory. Results: Depending on the size of the companion compared to the incident electromagnetic wavelength, the heating regime varies and can lead to a total evaporation of the companion. In particular, we find that inductive heating is mostly inefficient for small pulsar companions, although it is generally considered the dominant process. Conclusions: Small objects like asteroids can survive induction heating for 104 yr at distances as small as 1 R⊙ from the neutron star. For degenerate companions, induction heating cannot lead to evaporation and another source of heating (likely by kinetic energy of the pulsar wind) has to be considered. It was recently proposed that bodies orbiting pulsars are the cause of fast radio bursts; the present results explain how those bodies can survive in the pulsar's highly energetic environment.

  17. Polarization Properties of Rotation Powered Pulsars

    NASA Technical Reports Server (NTRS)

    Harding Alice K.

    2009-01-01

    Polarization measurements of rotation-powered pulsars and their nebulae have unique diagnostic potential. The polarization position angle of the pulsar wind nebula, as is know for the Crab pulsar, can tell us the orientation of the spin axis. Phase-resolved polarimetry of pulsars has had enormous diagnostic capability at radio and optical wavelengths and could also be a powerful diagnostic in the X-ray range. Measurement of the polarization properties as a function of pulse phase can therefore provide a multidimensional mapping of the pulsar emission. In the 'rotating vector' model, radiation originating near a magnetic pole is expected to show a characteristic S-shaped swing of the position angle vs. pulse phase. In this case it is possible to determine the magnetic inclination and viewing angles. Radiation originating further from the poles or further above the neutron star surface will have a more complex polarization signature, as a result of relativistic effects of aberration and time-of-flight delays and may also cause depolarization of the signal. I will discuss predicted polarization properties of pulsed emission in polar cap models, where radiation originates near the neutron star surface at the magnetic poles, and in slot gap and outer gap models, where radiation originates over a range of altitudes out to the speed-of-light cylinder.

  18. Pulsar H(alpha) Bowshocks probe Neutron Star Physics

    NASA Astrophysics Data System (ADS)

    Romani, Roger W.

    2014-08-01

    We propose a KOALA/AAOmega study of southern pulsar bow shocks. These rare, Balmer-dominated, non-radiative shocks provide an ideal laboratory to study the interaction of the relativistic pulsar wind with the ISM. We will cover H(alpha) at high spectral resolution to measure the kinematics of the upstream ISM and the post-shock flow, while the blue channel measures the Balmer decrement and probes for a faint cooling component. These data, with MHD models, allow us to extract the 3D flow geometry and the orientation and asymmetry of the pulsar wind. These data can also measure the pulsar spindown power, thus estimating the neutron star moment of inertia and effecting a fundamental test of dense matter physics.

  19. Future Gamma-Ray Observations of Pulsars and their Environments

    NASA Technical Reports Server (NTRS)

    Thompson, David J.

    2006-01-01

    Pulsars and pulsar wind nebulae seen at gamma-ray energies offer insight into particle acceleration to very high energies under extreme conditions. Pulsed emission provides information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars, while the pulsar wind nebulae yield information about high-energy particles interacting with their surroundings. During the next decade, a number of new and expanded gamma-ray facilities will become available for pulsar studies, including Astro-rivelatore Gamma a Immagini LEggero (AGILE) and Gamma-ray Large Area Space Telescope (GLAST) in space and a number of higher-energy ground-based systems. This review describes the capabilities of such observatories to answer some of the open questions about the highest-energy processes involving neutron stars.

  20. Radio wave propagation in pulsar magnetospheres

    NASA Astrophysics Data System (ADS)

    Petrova, S. A.; Lyubarskii, Yu. E.

    Pulsar magnetospheres are known to contain an ultrarelativistic highly magnetized plasma which streams along the open magnetic lines. The radio emission observed from pulsars is believed to originate sufficiently deep in the open field line tube, so that the characteristics of outgoing waves can be influenced by propagation in the magnetospheric plasma. Refraction of radio waves in pulsar magnetospheres appears to be efficient. The effect not only influences the observed pulse width and its frequency dependency. It can alter the apparent spatial structure of pulsar emission region which can be derived from the observations of pulsar interstellar scintillations. Transverse ray separation versus pulse longitude calculated allowing for magnetospheric refraction appears to be in qualitative agreement with that observed. In particular, the nonmonotonic character of the curve can be attributed to nonmonotonic distribution of the plasma number density across the open field line tube which makes the rays emitted at different spatial locations deviate in the opposite directions. Proceeding from the frequency dependence of refraction some predictions are made about the frequency evolution of the apparent spatial structure of pulsar emission region. Magnetospheric refraction can also determine the profile shape giving rise to ray grouping into separate components. It will be demonstrated that the salient features of profile morphology can be explained within the frame of a primordial hollow-cone emission model taking into account refraction of rays in pulsar plasma. Then the frequency evolution of profile structure is naturally interpreted as a consequence of frequency dependence of refraction. As the waves propagate in the magnetospheric plasma their polarization also evolves essentially. In the vicinity of the emission region normal waves are linearly polarized and propagate independently, with the polarization plane following the orientation of the local magnetic field. As

  1. Particle in Cell Simulations of the Pulsar Y-Point -- Nature of the Accelerating Electric Field

    NASA Astrophysics Data System (ADS)

    Belyaev, Mikhail

    2016-06-01

    Over the last decade, satellite observations have yielded a wealth of data on pulsed high-energy emission from pulsars. Several different models have been advanced to fit this data, all of which “paint” the emitting region onto a different portion of the magnetosphere.In the last few years, particle in cell simulations of pulsar magnetospheres have reached the point where they are able to self-consistently model particle acceleration and dissipation. One of the key findings of these simulations is that the region of the current sheet in and around the Y-point provides the highest rate of dissipation of Poynting flux (Belyaev 2015a). On the basis of this physical evidence, it is quite plausible that this region should be associated with the pulsed high energy emission from pulsars. We present high resolution PIC simulations of an axisymmetric pulsar magnetosphere, which are run using PICsar (Belyaev 2015b). These simulations focus on the particle dynamics and electric fields in and around the Y-point region. We run two types of simulations -- first, a force-free magnetosphere and second, a magnetosphere with a gap between the return current layer and the outflowing plasma in the polar wind zone. The latter setup is motivated by studies of pair production with general relativity (Philippov et al. 2015, Belyaev & Parfrey (in preparation)). In both cases, we find that the Y-point and the current sheet in its direct vicinity act like an “electric particle filter” outwardly accelerating particles of one sign of charge while returning the other sign of charge back to the pulsar. We argue that this is a natural behavior of the plasma as it tries to adjust to a solution that is as close to force-free as possible. As a consequence, a large E dot J develops in the vicinity of the Y-point leading to dissipation of Poynting flux. Our work is relevant for explaining the plasma physical mechanisms underlying pulsed high energy emission from pulsars.

  2. First-Principles Simulations of Pulsar Magnetospheres

    NASA Astrophysics Data System (ADS)

    Spitkovsky, Anatoly

    Pulsars are rotating magnetized neutron stars that produce broadband, pulsed emission. Observations with Fermi Gamma-ray Space Telescope have uncovered more than 100 gamma-ray emitting pulsars, dramatically expanding the number of such sources known, and producing unprecedented data on light curves and spectra in the gamma-ray band. The magnetospheric processes that lead to this emission are very interesting and currently not understood in detail. The main difficulty is the absence of a self-consistent model of the pulsar magnetosphere that can predict the global shape of the magnetic field and the state of the plasma throughout the magnetosphere. The standard picture envisions the magnetosphere as filled with plasma due to space-charge-limited flow of charges from the surface of the star. These charges are accelerated by strong electric fields induced by rapid stellar rotation. As charges are curved while traveling along the magnetic fields, they emit curvature radiation that can pair-produce and fill the magnetosphere with pair plasma. The currents and charges in this plasma affect magnetic field structure and particle acceleration. Until recently, no self-consistent solutions of the pulsar electrodynamics that accounted for plasma supply and production existed. Considerable progress on the global magnetospheric structure was made under assumptions about the plasma supply in the force-free and magnetohydrodynamic limits, which assume abundant plasma throughout the magnetosphere. These solutions allowed to calculate the global structure of oblique rotators and their spin-down power at the expense of losing information about particle density and acceleration, and making it difficult to compute emission spectra. Recently, the development of multidimensional kinetic simulations has brought the goal of self-consistently calculating plasma supply and magnetospheric shape of pulsars closer to reality. In this proposal, we plan to perform first three-dimensional kinetic

  3. The space velocities of radio pulsars

    NASA Astrophysics Data System (ADS)

    Loginov, A. A.; Nikitina, E. B.; Malov, I. F.

    2016-02-01

    Known models proposed to explain the high space velocities of pulsars based on asymmetry of the transport coefficients of different sorts of neutrinos or electromagnetic radiation can be efficient only in the presence of high magnetic fields (to 1016 G) or short rotation periods for the neutron stars (of the order of 1 ms). This current study shows that the observed velocities are not correlated with either the pulsar periods or their surface magnetic fields. The initial rotation periods are estimated in a model for the magnetedipolar deceleration of their spin, aßsuming that the pulsar ages are equal to their kinematic ages. The initial period distribution is bimodal, with peaks at 5 ms and 0.5 s, and similar to the current distribution of periods. It is shown that asymmetry of the pulsar electromagnetic radiation is insufficient to give rise to additional acceleration of pulsars during their evolution after the supernova explosion that gave birth to them. The observations testify to deceleration of the motion, most likely due to the influence of the interstellar medium and interactions with nearby objects. The time scale for the exponential decrease in the magnetic field τ D and in the angle between the rotation axis and magnetic moment τ ß are estimated, yielding τ β = 1.4 million years. The derived dependence of the transverse velocity of a pulsar on the angle between the line of sight and the rotation axis of the neutron star corresponds to the expected dependence for acceleration mechanisms associated with asymmetry of the radiation emitted by the two poles of the star.

  4. Observations of the Eclipsing Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    FRUCHTER et al. (1988a) HAVE RECENTLY DISCOVERED a 1.6 MSEC PULSAR (PSR 1957+20) IN A 9.2 HOUR ECLIPSING BINARY SYSTEM. THE UNUSUAL BEHAVIOR OF THE DISPERSION MEASURE AS A FUNCTION OF ORBITAL PHASE, AND THE DISAPPEARANCE OF THE PULSAR SIGNAL FOR 50 MINUTES DURING EACH ORBIT, IMPLIES THAT THE ECLIPSES ARE DUE TO A PULSAR-INDUCED WIND FLOWING OFF OF THE COMPANION. THE OPTICAL COUNTERPART IS A 21ST MAGNITUDE OBJECT WHICH VARIES IN INTENSITY OVER THE BINARY PERIOD; ACCURATE GROUND-BASED OBSERVATIONS ARE PREVENTED BY THE PROXIMITY (0.7") OF A 20TH MAGNITUDE K DWARF. WE PROPOSE TO OBSERVE THE OPTICAL COUNTERPART IN A TWO-PART STUDY. FIRST, THE WF/PC WILL PROVIDE ACCURATE MULTICOLOR PHOTOMETRY, ENABLING US TO DETERMINE UNCONTAMINATED MAGNITUDES AND COLORS BOTH AT MAXIMUM (ANTI-ECLIPSE) AS WELL AS AT MINIMUM (ECLIPSE). SECOND, WE PROPOSE TO OBSERVE THE EXPECTED UV LINE EMISSION WITH FOS, ALLOWING FOR AN INTIAL DETERMINATION OF THE TEMPERATURE AND DENSITY STRUCTURE AND ABUNDANCES OF THE WIND THAT IS BEING ABLATED FROM THE COMPANION. STUDY OF THIS UNIQUE SYSTEM HOLDS ENORMOUS POTENTIAL FOR THE UNDERSTANDING OF THE RADIATION FIELD OF A MILLISECOND PULSAR AND THE EVOLUTION OF LMXRBs AND MSPs IN GENERAL. WE EXPECT THESE OBSERVATIONS TO PLACE VERY SIGNIFICANT CONTRAINTS ON MODELS OF THIS UNIQUE OBJECT.

  5. The Pulsar Quartet: Listening to a Galactic Symphony

    NASA Astrophysics Data System (ADS)

    Kiziltan, Bülent

    2014-06-01

    Pulsars are exotic dead stars that emit very regular radio pulses. These pulses are attributed to their regular rotation. Some pulsars are spinning fast enough that the audio equivalent waveform of their pulses fall within our hearing range. If human ears were tuned to radio waves it would have been possible to ‘hear’ these very compact stars. We produced the audio waveform of these pulsar signals and mapped them onto a frequency chart to find the corresponding musical notes. We use these ‘audible' pulsars like musical instruments in a symphony orchestra to play a full quartet. At the same time, an accompanying visual interface shows the realistic distribution of all pulsars in our own Galaxy. Pulsars shine as they play each note in the quartet with realistic brightening and subsequent dimming proportional to their rotational energies. This can serve as an educational tool at all levels to demonstrate many interesting aspects of stellar evolution and articulate an aesthetic connection of us with the cosmos. Interested in watching the light show while the Milky Way Pulsar Orchestra plays a quartet?

  6. Multi-messenger Tests for Fast-spinning Newborn Pulsars Embedded in Stripped-envelope Supernovae

    NASA Astrophysics Data System (ADS)

    Kashiyama, Kazumi; Murase, Kohta; Bartos, Imre; Kiuchi, Kenta; Margutti, Raffaella

    2016-02-01

    Fast-spinning strongly magnetized newborn neutron stars (NSs), including nascent magnetars, are popularly implemented as the engine of luminous stellar explosions. Here, we consider the scenario that they power various stripped-envelope (SE) supernovae (SNe), not only superluminous SNe Ic but also broad-line (BL) SNe Ibc and possibly some ordinary SNe Ibc. This scenario is also motivated by the hypothesis that Galactic magnetars largely originate from fast-spinning NSs as remnants of SE SNe. By consistently modeling the energy injection from magnetized wind and {}56{Ni} decay, we show that proto-NSs with ≳ 10 {ms} rotation and a poloidal magnetic field of {B}{{dip}}≳ 5× {10}14 {{G}} can be harbored in ordinary SNe Ibc. On the other hand, millisecond proto-NSs can solely power BL SNe Ibc if they are born with {B}{{dip}}≳ 5× {10}14 {{G}} and superluminous SNe Ic with {B}{{dip}}≳ {10}13 {{G}}. Then, we study how multi-messenger emission can be used to discriminate such pulsar-driven SN models from other competitive scenarios. First, high-energy X-ray and gamma-ray emission from embryonic pulsar wind nebulae can probe the underlying newborn pulsar. Follow-up observations of SE SNe using NuSTAR ∼ 50{--}100 {days} after the explosion are strongly encouraged for nearby objects. We also discuss possible effects of gravitational waves (GWs) on the spin-down of proto-NSs. If millisecond proto-NSs with {B}{{dip}}\\lt {{a}} {few}× {10}13 {{G}} emit GWs through, e.g., non-axisymmetric rotation deformed by the inner toroidal fields of {B}{{t}}≳ {10}16 {{G}}, the GW signal can be detectable from ordinary SNe Ibc in the Virgo cluster by Advanced LIGO, Advanced Virgo, and KAGRA.

  7. AB INITIO PULSAR MAGNETOSPHERE: THREE-DIMENSIONAL PARTICLE-IN-CELL SIMULATIONS OF AXISYMMETRIC PULSARS

    SciTech Connect

    Philippov, Alexander A.; Spitkovsky, Anatoly

    2014-04-20

    We perform ''first-principles'' relativistic particle-in-cell simulations of aligned pulsar magnetosphere. We allow free escape of particles from the surface of a neutron star and continuously populate the magnetosphere with neutral pair plasma to imitate pair production. As pair plasma supply increases, we observe the transition from a charge-separated ''electrosphere'' solution with trapped plasma and no spin-down to a solution close to the ideal force-free magnetosphere with electromagnetically dominated pulsar wind. We calculate the magnetospheric structure, current distribution, and spin-down power of the neutron star. We also discuss particle acceleration in the equatorial current sheet.

  8. A process-based evaluation of dust-emitting winds in the CMIP5 simulation of HadGEM2-ES

    NASA Astrophysics Data System (ADS)

    Fiedler, Stephanie; Knippertz, Peter; Woodward, Stephanie; Martin, Gill M.; Bellouin, Nicolas; Ross, Andrew N.; Heinold, Bernd; Schepanski, Kerstin; Birch, Cathryn E.; Tegen, Ina

    2016-02-01

    Despite the importance of dust aerosol in the Earth system, state-of-the-art models show a large variety for North African dust emission. This study presents a systematic evaluation of dust emitting-winds in 30 years of the historical model simulation with the UK Met Office Earth-system model HadGEM2-ES for the Coupled Model Intercomparison Project Phase 5. Isolating the effect of winds on dust emission and using an automated detection for nocturnal low-level jets (NLLJs) allow an in-depth evaluation of the model performance for dust emission from a meteorological perspective. The findings highlight that NLLJs are a key driver for dust emission in HadGEM2-ES in terms of occurrence frequency and strength. The annually and spatially averaged occurrence frequency of NLLJs is similar in HadGEM2-ES and ERA-Interim from the European Centre for Medium-Range Weather Forecasts. Compared to ERA-Interim, a stronger pressure ridge over northern Africa in winter and the southward displaced heat low in summer result in differences in location and strength of NLLJs. Particularly the larger geostrophic winds associated with the stronger ridge have a strengthening effect on NLLJs over parts of West Africa in winter. Stronger NLLJs in summer may rather result from an artificially increased mixing coefficient under stable stratification that is weaker in HadGEM2-ES. NLLJs in the Bodélé Depression are affected by stronger synoptic-scale pressure gradients in HadGEM2-ES. Wintertime geostrophic winds can even be so strong that the associated vertical wind shear prevents the formation of NLLJs. These results call for further model improvements in the synoptic-scale dynamics and the physical parametrization of the nocturnal stable boundary layer to better represent dust-emitting processes in the atmospheric model. The new approach could be used for identifying systematic behavior in other models with respect to meteorological processes for dust emission. This would help to improve dust

  9. The Second Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Bhattacharyya, B.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burgay, M.; Burnett, T. H.; Busetto, G.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Camilo, F.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chaty, S.; Chaves, R. C. G.; Chekhtman, A.; Chen, A. W.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cognard, I.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; DeCesar, M. E.; De Luca, A.; den Hartog, P. R.; de Palma, F.; Dermer, C. D.; Desvignes, G.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Espinoza, C. M.; Falletti, L.; Favuzzi, C.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Freire, P. C. C.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gotthelf, E. V.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hessels, J.; Hewitt, J.; Hill, A. B.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Janssen, G. H.; Jogler, T.; Jóhannesson, G.; Johnson, R. P.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Johnston, S.; Kamae, T.; Kataoka, J.; Keith, M.; Kerr, M.; Knödlseder, J.; Kramer, M.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Lyne, A. G.; Manchester, R. N.; Marelli, M.; Massaro, F.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; McLaughlin, M. A.; Mehault, J.; Michelson, P. F.; Mignani, R. P.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Perkins, J. S.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Pletsch, H. J.; Porter, T. A.; Possenti, A.; Rainò, S.; Rando, R.; Ransom, S. M.; Ray, P. S.; Razzano, M.; Rea, N.; Reimer, A.; Reimer, O.; Renault, N.; Reposeur, T.; Ritz, S.; Romani, R. W.; Roth, M.; Rousseau, R.; Roy, J.; Ruan, J.; Sartori, A.; Saz Parkinson, P. M.; Scargle, J. D.; Schulz, A.; Sgrò, C.; Shannon, R.; Siskind, E. J.; Smith, D. A.; Spandre, G.; Spinelli, P.; Stappers, B. W.; Strong, A. W.; Suson, D. J.; Takahashi, H.; Thayer, J. G.; Thayer, J. B.; Theureau, G.; Thompson, D. J.; Thorsett, S. E.; Tibaldo, L.; Tibolla, O.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Venter, C.; Vianello, G.; Vitale, V.; Wang, N.; Weltevrede, P.; Winer, B. L.; Wolff, M. T.; Wood, D. L.; Wood, K. S.; Wood, M.; Yang, Z.

    2013-10-01

    This catalog summarizes 117 high-confidence >=0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  10. THE SECOND FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS

    SciTech Connect

    Abdo, A. A.; Ajello, M.; Allafort, A.; Bloom, E. D.; Bottacini, E.; Baldini, L.; Ballet, J.; Baring, M. G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Bregeon, J.; Bhattacharyya, B.; Bissaldi, E.; Bonamente, E.; Brandt, T. J.; Brigida, M.; and others

    2013-10-01

    This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  11. Neutrinos from binary pulsars. [generated by high energy particles striking companion star

    NASA Technical Reports Server (NTRS)

    Eichler, D.

    1978-01-01

    It is shown that binary systems containing moderately young pulsars may emit high-energy neutrinos (between 1 and 100 TeV) at detectable levels. The pulsars are assumed to have total luminosities of the order of 10 to the 38th erg/sec. The neutrinos are produced by high energy particles (e.g. protons) from the pulsar striking the companion. Cyg X3 may be detectable in high-energy neutrinos if it emits greater than about 10 to the 35th erg/sec in high-energy protons. There may be a whole class of objects like Cyg X3, but obscured by thick accretion clouds.

  12. WIDE RADIO BEAMS FROM {gamma}-RAY PULSARS

    SciTech Connect

    Ravi, V.; Manchester, R. N.; Hobbs, G.

    2010-06-10

    We investigate the radio and {gamma}-ray beaming properties of normal and millisecond pulsars (MSPs) by selecting two samples from the known populations. The first, Sample G, contains pulsars which are detectable in blind searches of {gamma}-ray data from the Fermi Large Area Telescope. The second, Sample R, contains pulsars detectable in blind radio searches which have spin-down luminosities E>10{sup 34} erg s{sup -1}. We analyze the fraction of the {gamma}-ray-selected Sample G which have detectable radio pulses and the fraction of the radio-selected Sample R which have detectable {gamma}-ray pulses. Twenty of our 35 Sample G pulsars have already observed radio pulses. This rules out low-altitude polar-cap beaming models if, as is currently believed, {gamma}-ray beams are generated in the outer magnetosphere and are very wide. We further find that, for the highest-E pulsars, the radio and {gamma}-ray beams have comparable beaming factors, i.e., the beams cover similar regions of the sky as the star rotates. For lower-E {gamma}-ray emitting pulsars, the radio beams have about half of the {gamma}-ray sky coverage. These results suggest that, for high-E young and MSPs, the radio emission originates in wide beams from regions high in the pulsar magnetosphere, probably close to the null-charge surface and to the {gamma}-ray emitting regions. Furthermore, it suggests that for these high-E pulsars, as in the {gamma}-ray case, features in the radio profile represent caustics in the emission beam pattern.

  13. Braking index of isolated pulsars

    NASA Astrophysics Data System (ADS)

    Hamil, O.; Stone, J. R.; Urbanec, M.; Urbancová, G.

    2015-03-01

    Isolated pulsars are rotating neutron stars with accurately measured angular velocities Ω , and their time derivatives that show unambiguously that the pulsars are slowing down. Although the exact mechanism of the spin-down is a question of detailed debate, the commonly accepted view is that it arises through emission of magnetic dipole radiation (MDR) from a rotating magnetized body. Other processes, including the emission of gravitational radiation, and of relativistic particles (pulsar wind), are also being considered. The calculated energy loss by a rotating pulsar with a constant moment of inertia is assumed proportional to a model dependent power of Ω . This relation leads to the power law Ω ˙ =-K Ωn where n is called the braking index. The MDR model predicts n exactly equal to 3. Selected observations of isolated pulsars provide rather precise values of n , individually accurate to a few percent or better, in the range 1

  14. Chandra Associates Pulsar and Historic Supernova

    NASA Astrophysics Data System (ADS)

    2001-01-01

    in the same area of the sky. Past attempts to identify the pulsar with G11.2-0.3, and hence the ancient Chinese observations, have been controversial. The location of the pulsar at the center of the remnant provides new evidence that it is associated with the remnant. Since pulsars are known to move rapidly away from where they are formed, a pulsar near the center of the remnant implies the system must be very young, since not enough time has elapsed for the pulsar to travel far from its birthplace. "We believe that the pulsar and the supernova remnant G11.2-0.3 are both likely to be left over from the explosion seen by the Chinese observers over 1600 years ago," said Roberts. "While this is exciting by itself, it also raises new questions about what we know about pulsars especially during their infancies." These questions follow from a discrepancy that arose when the ASCA team applied the present spin rate to current models to determine the pulsar’s estimated lifetime and compare it to the age of G11.2-0.3. The result was an age of roughly 24,000 years - far predating the birth year of 386 AD. To explain this contradiction, the Chandra team argues that this pulsar may have had approximately the same spin rate today as it did at its birth, as had been suggested by the ASCA data. If this is true, then it could have important implications for the conventional wisdom regarding pulsars, which, may be born spinning more slowly than has been thought. "We now have strong evidence that the standard age estimate for this pulsar is probably wrong, and it is much younger than previously believed," said Kaspi. "This, in turn, suggests that other standard pulsar age estimates may be wrong as well, and this has important implications for the population as a whole." In addition to these results, the Chandra observations of G11.2-0.3 have, for the first time, revealed the bizarre appearance of the pulsar wind nebula (also known as "plerions") at the center of the supernova remnant

  15. Radio efficiency of pulsars

    SciTech Connect

    Szary, Andrzej; Melikidze, George I.; Gil, Janusz; Zhang, Bing; Xu, Ren-Xin E-mail: zhang@physics.unlv.edu

    2014-03-20

    We investigate radio emission efficiency, ξ, of pulsars and report a near-linear inverse correlation between ξ and the spin-down power, E-dot , as well as a near-linear correlation between ξ and pulsar age, τ. This is a consequence of very weak, if any, dependences of radio luminosity, L, on pulsar period, P, and the period derivative, P-dot , in contrast to X-ray or γ-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is ≈10{sup 29} erg s{sup –1}, regardless of the position in the P-- P-dot diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for radio efficiency into the Monte Carlo-based population syntheses we can reproduce the observed sample using the random luminosity model. Using the Kolmogorov-Smirnov test on a synthetic flux distribution reveals a high probability of reproducing the observed distribution. Our results suggest that the plasma responsible for generating radio emission is produced under similar conditions regardless of pulsar age, dipolar magnetic field strength, and spin-down rate. The magnetic fields near the pulsar surface are likely dominated by crust-anchored, magnetic anomalies, which do not significantly differ among pulsars, leading to similar conditions for generating electron-positron pairs necessary to power radio emission.

  16. Stellar evolution and pulsars.

    NASA Technical Reports Server (NTRS)

    Chiu, H.-Y.

    1972-01-01

    It has been found that pulsars are rotating magnetic neutron stars, which are created during catastrophic collapses of old stars whose nuclear fuel has long since been used up. The maximum size of pulsars, based on the fastest rotation period of 33 msec, cannot exceed 100 km. The densest star the theory predicts is the neutron star. Its diameter is only 10 km. The processes producing radiation from pulsars are discussed, giving attention to a process similar to that by which a klystron operates and to a process based on a maser mechanism.

  17. High Energy Cosmic Rays and Neutrinos from Newborn Pulsars

    NASA Astrophysics Data System (ADS)

    Fang, Ke; Kotera, Kumiko; Olinto, Angela

    2013-04-01

    Newborn pulsars offer favorable sites for cosmic ray acceleration and interaction. Particles could be striped off the star surface and accelerated in the pulsar wind up to PeV-100 EeV energies, depending on the pulsar's birth period and magnetic field strength. Once accelerated, the cosmic rays interact with the surrounding supernova ejecta until they escape the source. By assuming a normal distribution of pulsar birth periods centered at 300,ms, we find the combined contribution of extragalactic pulsars produce ultrahigh energy cosmic rays that agree with both the observed energy spectrum and composition trend reported by the Auger Observatory. Meanwhile, we point out their Galactic counterparts naturally give rise to a cosmic ray flux peaked at very high energies (VHE, between 10^16 and 10^18 ,eV), which can bridge the gap between predictions of cosmic rays produced by supernova remnants and the observed spectrum and composition just below the ankle. Young pulsars in the universe would also contribute to a diffuse neutrino background due to the photomeson interactions, whose detectability and typical neutrino energy are discussed. Lastly, we predict a neutrino emission level for the future birth of a nearby pulsar.

  18. AMBER/VLTI high spectral resolution observations of the Brγ emitting region in HD 98922. A compact disc wind launched from the inner disc region

    NASA Astrophysics Data System (ADS)

    Caratti o Garatti, A.; Tambovtseva, L. V.; Garcia Lopez, R.; Kraus, S.; Schertl, D.; Grinin, V. P.; Weigelt, G.; Hofmann, K.-H.; Massi, F.; Lagarde, S.; Vannier, M.; Malbet, F.

    2015-10-01

    Context. High angular and spectral resolution observations can provide us with fundamental clues to the complex circumstellar structure of young stellar objects (YSOs) and to the physical processes taking place close to these sources. Aims: We analyse the main physical parameters and the circumstellar environment of the young Herbig Be star HD 98922. Methods: We present AMBER/VLTI high spectral resolution (R = 12 000) interferometric observations across the Brγ line, accompanied by UVES high-resolution spectroscopy and SINFONI-AO assisted near-infrared (NIR) integral field spectroscopic data. To interpret our observations, we develop a magneto-centrifugally driven disc-wind model. Results: Our analysis of the UVES spectrum shows that HD 98922 is a young (~5 × 105 yr) Herbig Be star (SpT = B9V), located at a distance of 440± 6050 pc, with a mass accretion rate (Ṁacc) of ~(9 ± 3) × 10-7 M⊙ yr-1. SINFONI K-band AO-assisted imaging shows a spatially resolved circumstellar disc-like region (~140 AU in diameter) with asymmetric brightness distribution. Our AMBER/VLTI UT observations indicate that the Brγ emitting region (ring-fit radius ~0.31 ± 0.04 AU) is smaller than the continuum emitting region (inner dust radius ~0.7 ± 0.2 AU), showing significant non-zero V-shaped differential phases (i.e. non S-shaped, as expected for a rotating disc). The value of the continuum-corrected pure Brγ line visibility at the longest baseline (89 m) is ~0.8 ± 0.1, i.e. the Brγ emitting region is partially resolved. Our modelling suggests that the observed Brγ line-emitting region mainly originates from a disc wind with a half opening angle of 30°, and with a mass-loss rate (Ṁw) of ~2 × 10-7 M⊙ yr-1. The observed V-shaped differential phases are reliably reproduced by combining a simple asymmetric continuum disc model with our Brγ disc-wind model. Conclusions: In conclusion, the Brγ emission of HD 98922 can be modelled with a disc wind that is able to

  19. Geriatric Pulsar Still Kicking

    NASA Astrophysics Data System (ADS)

    2009-02-01

    The oldest isolated pulsar ever detected in X-rays has been found with NASA's Chandra X-ray Observatory. This very old and exotic object turns out to be surprisingly active. The pulsar, PSR J0108-1431 (J0108 for short) is about 200 million years old. Among isolated pulsars -- ones that have not been spun-up in a binary system -- it is over 10 times older than the previous record holder with an X-ray detection. At a distance of 770 light years, it is one of the nearest pulsars known. Pulsars are born when stars that are much more massive than the Sun collapse in supernova explosions, leaving behind a small, incredibly weighty core, known as a neutron star. At birth, these neutron stars, which contain the densest material known in the Universe, are spinning rapidly, up to a hundred revolutions per second. As the rotating beams of their radiation are seen as pulses by distant observers, similar to a lighthouse beam, astronomers call them "pulsars". Astronomers observe a gradual slowing of the rotation of the pulsars as they radiate energy away. Radio observations of J0108 show it to be one of the oldest and faintest pulsars known, spinning only slightly faster than one revolution per second. The surprise came when a team of astronomers led by George Pavlov of Penn State University observed J0108 in X-rays with Chandra. They found that it glows much brighter in X-rays than was expected for a pulsar of such advanced years. People Who Read This Also Read... Chandra Data Reveal Rapidly Whirling Black Holes Milky Way’s Giant Black Hole Awoke from Slumber 300 Years Ago Erratic Black Hole Regulates Itself Celebrate the International Year of Astronomy Some of the energy that J0108 is losing as it spins more slowly is converted into X-ray radiation. The efficiency of this process for J0108 is found to be higher than for any other known pulsar. "This pulsar is pumping out high-energy radiation much more efficiently than its younger cousins," said Pavlov. "So, although it

  20. Fermi Pulsar Analysis

    NASA Video Gallery

    This animation illustrates how analysis of Fermi data reveals new pulsars. Fermi's LAT records the precise arrival time and approximate direction of the gamma rays it detects, but to identify a pul...

  1. Observations of accreting pulsars

    NASA Technical Reports Server (NTRS)

    Prince, Thomas A.; Bildsten, Lars; Chakrabarty, Deepto; Wilson, Robert B.; Finger, Mark H.

    1994-01-01

    We discuss recent observations of accreting binary pulsars with the all-sky BATSE instrument on the Compton Gamma Ray Observatory. BATSE has detected and studied nearly half of the known accreting pulsar systems. Continuous timing studies over a two-year period have yielded accurate orbital parameters for 9 of these systems, as well as new insights into long-term accretion torque histories.

  2. Pulse Portraiture: Pulsar timing

    NASA Astrophysics Data System (ADS)

    Pennucci, Timothy T.; Demorest, Paul B.; Ransom, Scott M.

    2016-06-01

    Pulse Portraiture is a wideband pulsar timing code written in python. It uses an extension of the FFTFIT algorithm (Taylor 1992) to simultaneously measure a phase (TOA) and dispersion measure (DM). The code includes a Gaussian-component-based portrait modeling routine. The code uses the python interface to the pulsar data analysis package PSRCHIVE (ascl:1105.014) and also requires the non-linear least-squares minimization package lmfit (ascl:1606.014).

  3. THE RADIATIVE X-RAY AND GAMMA-RAY EFFICIENCIES OF ROTATION-POWERED PULSARS

    SciTech Connect

    Vink, Jacco; Bamba, Aya; Yamazaki, Ryo

    2011-02-01

    We present a statistical analysis of the X-ray luminosity of rotation-powered pulsars and their surrounding nebulae using the sample of Kargaltsev and Pavlov, and we complement this with an analysis of the {gamma}-ray emission of Fermi-detected pulsars. We report a strong trend in the efficiency with which spin-down power is converted to X-ray and {gamma}-ray emission with characteristic age: young pulsars and their surrounding nebulae are efficient X-ray emitters, whereas in contrast old pulsars are efficient {gamma}-ray emitters. We divided the X-ray sample in a young ({tau}{sub c} < 1.7 x 10{sup 4} yr) and old sample and used linear regression to search for correlations between the logarithm of the X-ray and {gamma}-ray luminosities and the logarithms of the periods and period derivatives. The X-ray emission from young pulsars and their nebulae are both consistent with L{sub X}{proportional_to} P-dot{sup 3}/P{sup 6}. For old pulsars and their nebulae the X-ray luminosity is consistent with a more or less constant efficiency {eta}{identical_to}L{sub X}/ E-dot{sub rot}{approx}8x10{sup -5}. For the {gamma}-ray luminosity we confirm that L{sub {gamma}} {proportional_to} {radical}E-dot{sub rot}. We discuss these findings in the context of pair production inside pulsar magnetospheres and the striped wind model. We suggest that the striped wind model may explain the similarity between the X-ray properties of the pulsar wind nebulae and the pulsars themselves, which according to the striped wind model may both find their origin outside the light cylinder, in the pulsar wind zone.

  4. The Vela pulsar in the near-infrared

    NASA Astrophysics Data System (ADS)

    Shibanov, Yu. A.; Koptsevich, A. B.; Sollerman, J.; Lundqvist, P.

    2003-08-01

    We report on the first detection of the Vela pulsar in the near-infrared with the VLT/ISAAC in the Js and H bands. The pulsar magnitudes are Js=22.71+/-0.10 and H=22.04+/-0.16. We compare our results with the available multiwavelength data and show that the dereddened phase-averaged optical spectrum of the pulsar can be fitted with a power law Fnu ~ nu -alpha_nu with alphanu = 0.12+/-0.05, assuming the color excess EB-V=0.055+/-0.005 based on recent spectral fits of the emission of the Vela pulsar and its supernova remnant in X-rays. The negative slope of the pulsar spectrum is different from the positive slope observed over a wide optical range in the young Crab pulsar spectrum. The near-infrared part of the Vela spectrum appears to have the same slope as the phase-averaged spectrum in the high energy X-ray tail, obtained in the 2-10 keV range with the RXTE. Both of these spectra can be fitted with a single power law suggesting their common origin. Because the phase-averaged RXTE spectrum in this range is dominated by the second X-ray peak of the pulsar light curve, coinciding with the second main peak of its optical pulse profile, we suggest that this optical peak can be redder than the first one. We also detect two faint extended structures in the 1.5 = 3.1 arcsec vicinity of the pulsar, projected on and aligned with the south-east jet and the inner arc of the pulsar wind nebula, detected in X-rays with Chandra. We discuss their possible association with the nebula. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programme 66.D-0568).

  5. STRONG FIELD EFFECTS ON PULSAR ARRIVAL TIMES: GENERAL ORIENTATIONS

    SciTech Connect

    Wang Yan; Creighton, Teviet; Price, Richard H.; Jenet, Frederick A.

    2009-11-10

    A pulsar beam passing close to a black hole can provide a probe of very strong gravitational fields even if the pulsar itself is not in a strong field region. In the case that the spin of the hole can be ignored, we have previously shown that all strong field effects on the beam can be understood in terms of two 'universal' functions: F(phi{sub in}) and T(phi{sub in}) of the angle of beam emission phi{sub in}; these functions are universal in that they depend only on a single parameter, the pulsar/black hole distance from which the beam is emitted. Here we apply this formalism to general pulsar-hole-observer geometries, with arbitrary alignment of the pulsar spin axis and arbitrary pulsar beam direction and angular width. We show that the analysis of the observational problem has two distinct elements: (1) the computation of the location and trajectory of an observer-dependent 'keyhole' direction of emission in which a signal can be received by the observer; and (2) the determination of an annulus that represents the set of directions containing beam energy. Examples of each are given along with an example of a specific observational scenario.

  6. The Pulsating Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

    Tsui, K. H.

    2015-06-01

    Following the basic principles of a charge-separated pulsar magnetosphere, we consider the magnetosphere to be stationary in space, instead of corotating, and the electric field to be uploaded from the potential distribution on the pulsar surface, set up by the unipolar induction. Consequently, the plasma of the magnetosphere undergoes guiding center drifts of the gyromotion due to the forces transverse to the magnetic field. These forces are the electric force, magnetic gradient force, and field line curvature force. Since these plasma velocities are of drift nature, there is no need to introduce an emf along the field lines, which would contradict the {{E}\\parallel }={\\boldsymbol{E}} \\cdot {\\boldsymbol{B}} =0 plasma condition. Furthermore, there is also no need to introduce the critical field line separating the electron and ion open field lines. We present a self-consistent description where the magnetosphere is described in terms of electric and magnetic fields and also in terms of plasma velocities. The fields and velocities are then connected through the space-charge densities self-consistently. We solve the pulsar equation analytically for the fields and construct the standard steady-state pulsar magnetosphere. By considering the unipolar induction inside the pulsar and the magnetosphere outside the pulsar as one coupled system, and under the condition that the unipolar pumping rate exceeds the Poynting flux in the open field lines, plasma pressure can build up in the magnetosphere, in particular, in the closed region. This could cause a periodic opening up of the closed region, leading to a pulsating magnetosphere, which could be an alternative to pulsar beacons. The closed region can also be opened periodically by the build up of toroidal magnetic field through a positive feedback cycle.

  7. Pulsar lensing geometry

    NASA Astrophysics Data System (ADS)

    Liu, Siqi; Pen, Ue-Li; Macquart, J.-P.; Brisken, Walter; Deller, Adam

    2016-05-01

    We test the inclined sheet pulsar scintillation model (Pen & Levin) against archival very long baseline interferometry (VLBI) data on PSR 0834+06 and show that its scintillation properties can be precisely reproduced by a model in which refraction occurs on two distinct lens planes. These data strongly favour a model in which grazing-incidence refraction instead of diffraction off turbulent structures is the primary source of pulsar scattering. This model can reproduce the parameters of the observed diffractive scintillation with an accuracy at the percent level. Comparison with new VLBI proper motion results in a direct measure of the ionized interstellar medium (ISM) screen transverse velocity. The results are consistent with ISM velocities local to the PSR 0834+06 sight-line (through the Galaxy). The simple 1-D structure of the lenses opens up the possibility of using interstellar lenses as precision probes for pulsar lens mapping, precision transverse motions in the ISM, and new opportunities for removing scattering to improve pulsar timing. We describe the parameters and observables of this double screen system. While relative screen distances can in principle be accurately determined, a global conformal distance degeneracy exists that allows a rescaling of the absolute distance scale. For PSR B0834+06, we present VLBI astrometry results that provide (for the first time) a direct measurement of the distance of the pulsar. For most of the recycled millisecond pulsars that are the targets of precision timing observations, the targets where independent distance measurements are not available. The degeneracy presented in the lens modelling could be broken if the pulsar resides in a binary system.

  8. Superfluidity in Millisecond Pulsars (Review)

    NASA Astrophysics Data System (ADS)

    Pines, D.; Alpar, A.

    The authors review the evidence for superfluidity in the Vela pulsar, the Crab pulsar and PSR 0525+21, and examine the prospects for observing similar consequences of superfluidity in the already-discovered millisec pulsars. They consider, inter alia, the likelihood of observing glitches, the expected post-glitch behavior, and pulsar heating by energy dissipation due to the creep of neutron vortex lines in pinned superfluid regions of the crust.

  9. The Twisting Jet from the Vela Pulsar

    NASA Astrophysics Data System (ADS)

    Teter, M. A.; Pavlov, G. G.; Sanwal, D.; Kargaltsev, O.

    2002-05-01

    Observations of the Vela pulsar-wind nebula (PWN) with Chandra have revealed a long, thin filament -- an extension of the pulsar's jet beyond the bright outer arc confining the PWN in the direction of the pulsar's proper motion. This curved external jet terminates in a region of enhanced emission (a blob) at a distance of about 100'' (0.15 pc) from the pulsar, larger than the size of the PWN. The shape of the jet and its brightness are seen to vary on a timescale as short as a few days, its remote parts move in the sky plane with apparent velocities of up to 0.2 c. The X-ray spectrum of the external jet, including the termination blob, shows no spectral features. It is well described by a power-law model with a photon-index of γ ~= 1.2 (slightly harder than the average spectrum of the PWN, γ ~= 1.5). This indicates that the jet's radiation is due to synchrotron emission of relativistic particles in a magnetic field. The fact that the jet remains confined, although it twists at large distances from the pulsar, suggests a self-confining structure of its magnetic field. The varying shape and intensity of this stream of relativistic particles can be associated with varying local conditions in the Vela SNR and/or large-scale MHD instabilities and internal variations of the magnetic field within the jet. We will present a movie with a sequence of 12 Chandra images over past two years, demonstrating the structure of the twisting jet, and discuss various interpretations of these observations. The work was partially supported by SAO grant GO2-3091X and NASA grant NAG5-10865.

  10. On the peculiar shapes of some pulsar bow-shock nebulae

    NASA Astrophysics Data System (ADS)

    Bandiera, Rino

    Pulsar bow-shock nebulae are pulsar-wind nebulae formed by the direct interaction of pulsar relativistic winds with the interstellar medium. The bow-shock morphology, well outlined in Hα for some objects, is an effect of the supersonic pulsar motion with respect to the ambient medium. However, in a considerable fraction of cases (e.g. the nebulae associated to PSR B2224+65, PSR B0740-28, PSR J2124-3358) clear deviations from the classical bow shock shape are observed. Such deviations are usually interpreted as due to ambient density gradients and/or to pulsar-wind anisotropies. Here I present a different interpretation, aiming at explaining deviations from the standard morphology as signs of the peculiar physical conditions present in these objects. Using dimensional arguments, I show that, unlike normal pulsar-wind nebulae, in pulsar bow-shock nebulae the mean free path of the highest-energy particles may be comparable with the bow-shock head. I then investigate whether this may affect the shape of the bow-shock; for instance, whether a conical bow shock (like that observed in the "Guitar", the nebula associated to PSR B2224+65) does really imply an ambient density gradient. Finally, I discuss some other possible signatures of these high-energy, long mean-free-path particles.