Science.gov

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 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.

  3. 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.

  4. The VERITAS Supernova Remnant / Pulsar Wind Nebula Observation Program

    NASA Astrophysics Data System (ADS)

    Humensky, Thomas Brian; VERITAS Collaboration

    2011-09-01

    Supernova remnants and pulsar wind nebulae together constitute the vast majority of galactic gamma-ray sources seen at TeV energies. Supernova remnants are widely considered to be the strongest candidate for the source of cosmic rays below the knee around 1015 eV. Pulsar wind nebulae, powered by the spin-down energy released by pulsars and visible due to synchrotron and inverse Compton radiation emitted by their constituent electrons, comprise one of the most populous VHE gamma-ray source classes. VERITAS, an array of four imaging Cherenkov telescopes located at the Whipple Observatory in southern Arizona, has made significant contributions to the study of both classes of objects. This poster will summarize the results of this observation program and prospects for the future.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Spectral properties and variability of the Vela pulsar wind nebula

    NASA Astrophysics Data System (ADS)

    Rangelov, Blagoy; Kargaltsev, Oleg; Pavlov, George; Klingler, Noel; Kropotina, Julia

    2015-08-01

    The non-thermal emission around young pulsars (seen in radio and X-rays) is known to be synchrotron radiation from a relativistic pulsar wind shocked in the ambient medium. One of the best examples is the Vela pulsar wind nebula (PWN), which shows spectacular structure, such as jets, arcs, knots, and diffuse extended emission, detected with Chandra. The morphology of the Vela PWN is determined by the properties of the pulsar wind and surrounding medium. We will present the results of our multi-year Chandra campaign. We will present our analysis of the variability and spectral properties of the compact nebula and discuss their implications for pulsar wind models and for the interaction of the relativistic pulsar wind with the ambient medium.

  11. 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.

  12. 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.

  13. The imprint of pulsar parameters on the morphology of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Bühler, Rolf; Giomi, Matteo

    2016-11-01

    The morphology of young Pulsar Wind Nebulae (PWN) is largely determined by the properties of the wind injected by the pulsar. We have used a recent parametrization of the wind obtained from force-free electrodynamics simulations of pulsar magnetospheres to simulate nebulae for different sets of pulsar parameters. We performed axisymmetric relativistic magnetohydrodynamics simulations to test the morphology dependence of the nebula on the obliquity of the pulsar and on the magnetization of the pulsar wind. We compare these simulations to the morphology of the Vela and Crab PWN. We find that the morphology of Vela can be reproduced qualitatively if the pulsar obliquity angle is α ≈ 45° and the magnetization of the wind is high (σ0 ≈ 3.0). A morphology similar to the one of the Crab nebula is only obtained for low-magnetization simulations with α ≳ 45°. Interestingly, we find that Kelvin-Helmholtz instabilities produce small-scale turbulences downstream of the reverse shock of the pulsar wind.

  14. 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.

  15. 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.

  16. Evolution of Pulsar Wind Nebulae inside Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Temim, T.

    2016-06-01

    Composite supernova remnants (SNRs) are those consisting of both a central pulsar that produces a wind of synchrotron-emitting relativistic particle and a supernova (SN) blast wave that expands into the surrounding interstellar medium (ISM). The evolution of the pulsar wind nebula (PWN) is coupled to the evolution of its host SNR and characterized by distinct stages, from the PWN's early expansion into the unshocked SN ejecta to its late-phase interaction with the SNR reverse shock. I will present an overview of the various evolutionary stages of composite SNRs and show how the signatures of the PWN/SNR interaction can reveal important information about the SNR and PWN dynamics, the SN progenitor and explosion asymmetry, the properties of the SN ejecta and newly-formed dust, particle injection and loss processes, and the eventual escape of energetic particles into the ISM. I will also discuss recent multi-wavelength observations and hydrodynamical modeling of evolved systems in which the PWN interacts with the SNR reverse shock and discuss their implications for our general understanding of the structure and evolution of composite SNRs.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Constraining the parameters of the pulsar wind nebula DA 495 and its pulsar with Chandra and XMM-Newton

    NASA Astrophysics Data System (ADS)

    Karpova, A.; Zyuzin, D.; Danilenko, A.; Shibanov, Yu.

    2015-11-01

    We present spectral and timing analyses of the X-ray emission from the pulsar wind nebula DA 495 and its central object, J1952.2+2925, suggested to be the pulsar, using archival Chandra and XMM-Newton data. J1952.2+2925 has a pure thermal spectrum which is equally well fitted either by the blackbody model with a temperature of ≈215 eV and an emitting area radius of ≈0.6 km or by magnetized neutron star atmosphere models with temperatures of 80-90 eV. In the latter case, the thermal emission can come from the entire neutron star surface which temperature is consistent with standard neutron star cooling scenarios. We place also an upper limit on the J1952.2+2925 non-thermal flux. The derived spectral parameters are generally compatible with published ones based only on the Chandra data, but they are much more accurate due to the inclusion of XMM-Newton data. No pulsations were found and we placed an upper limit for the J1952.2+2925 pulsed emission fraction of 40 per cent. Utilizing the interstellar absorption-distance relation, we estimated the distance to DA 495, which can be as large as 5 kpc if J1952.2+2925 emission is described by the atmosphere models. We compiled possible multiwavelength spectra of the nebula including radio data; they depend on the spectral model of the central object. Comparing the results with other pulsar plus wind nebula systems, we set reasonable constraints on the J1952.2+2925 spin-down luminosity and age. We suggest that the Fermi source 3FGL J1951.6+2926 is the likely γ-ray counterpart of J1952.2+2925.

  7. 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.

  8. A Stochastic Acceleration Model of Radio Emission from Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Tanaka, S.; Asano, K.

    2016-06-01

    The broadband emission of Pulsar Wind Nebulae (PWNe) is well described by non-thermal emissions from accelerated electrons and positrons. However, the difference of spectral indices at radio and X-rays are not reproduced by the standard shock particle acceleration and cooling processes, and then, for example, the broken power-law spectrum for the particle energy distribution at the injection has been groundlessly adopted. Here, we propose a possible resolution for the particle distribution; the radio emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside the PWNe. The turbulence may be induced by the interaction of the pulsar wind with the supernova ejecta. We upgrade our one-zone spectral evolution model including the stochastic acceleration and apply it to the Crab Nebula. We consider both continuous and impulsive injections of particles to the stochastic acceleration process. The radio emission in the Crab Nebula is reproduced by our stochastic acceleration model. The required forms of the momentum diffusion coefficient will be discussed.

  9. Newest insights from MHD numerical modeling of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Numerical MHD models are considered very successful in accounting for many of the observed properties of Pulsar Wind Nebulae (PWNe), especially those concerning the high energy emission morphology and the inner nebula dynamics. Although PWNe are known to be among the most powerful accelerators in nature, producing particles up to PeV energies, the mechanisms responsible of such an efficient acceleration are still a deep mystery. Indeed, these processes take place in one of the most hostile environment for particle acceleration: the relativistic and highly magnetized termination shock of the pulsar wind. The newest results from numerical simulations of the Crab Nebula, the PWN prototype, will be presented, with special attention to the problem of particle acceleration. In particular it will be shown how a multi-wavelengths analysis of the wisps properties can be used to constrain the particle acceleration mechanisms working at the Crab's termination shock, by identifying the particle acceleration site at the shock front.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Magnetic Fields in Supernova Remnants and Pulsar-Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Reynolds, Stephen P.; Gaensler, B. M.; Bocchino, Fabrizio

    2012-05-01

    We review the observations of supernova remnants (SNRs) and pulsar-wind nebulae (PWNe) that give information on the strength and orientation of magnetic fields. Radio polarimetry gives the degree of order of magnetic fields, and the orientation of the ordered component. Many young shell supernova remnants show evidence for synchrotron X-ray emission. The spatial analysis of this emission suggests that magnetic fields are amplified by one to two orders of magnitude in strong shocks. Detection of several remnants in TeV gamma rays implies a lower limit on the magnetic-field strength (or a measurement, if the emission process is inverse-Compton upscattering of cosmic microwave background photons). Upper limits to GeV emission similarly provide lower limits on magnetic-field strengths. In the historical shell remnants, lower limits on B range from 25 to 1000 μG. Two remnants show variability of synchrotron X-ray emission with a timescale of years. If this timescale is the electron-acceleration or radiative loss timescale, magnetic fields of order 1 mG are also implied. In pulsar-wind nebulae, equipartition arguments and dynamical modeling can be used to infer magnetic-field strengths anywhere from ˜5 μG to 1 mG. Polarized fractions are considerably higher than in SNRs, ranging to 50 or 60% in some cases; magnetic-field geometries often suggest a toroidal structure around the pulsar, but this is not universal. Viewing-angle effects undoubtedly play a role. MHD models of radio emission in shell SNRs show that different orientations of upstream magnetic field, and different assumptions about electron acceleration, predict different radio morphology. In the remnant of SN 1006, such comparisons imply a magnetic-field orientation connecting the bright limbs, with a substantial density gradient across the remnant.

  15. 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.

  16. 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.

  17. 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

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

    PubMed

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

    2012-02-15

    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.

  19. 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.

  20. 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.

  1. 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.

  2. MULTI-WAVELENGTH EMISSION REGION OF {gamma}-RAY EMITTING PULSARS

    SciTech Connect

    Kisaka, S.; Kojima, Y. E-mail: kojima@theo.phys.sci.hiroshima-u.ac.jp

    2011-09-20

    Using the outer gap model, we investigate the emission region for the multi-wavelength light curve from energetic pulsars. We assume that {gamma}-ray and non-thermal X-ray photons are emitted from a particle acceleration region in the outer magnetosphere, and UV/optical photons originate above that region. We assume that {gamma}-rays are radiated only by outwardly moving particles, whereas the other photons are produced by particles moving inward and outward. We parameterize the altitude of the emission region as the deviation from the rotating dipole in a vacuum and determine it from the observed multi-wavelength pulse profile using the observationally constrained magnetic dipole inclination angle and viewing angle of the pulsars. We find that the outer gap model can explain the multi-wavelength pulse behavior by a simple distribution of emissivity, and discuss the possibility of further improvement. From observational fitting, we also find a general tendency for the altitude of the {gamma}-ray emission region to depend on the inclination angle. In particular, the emission region for low inclination angle is required to be located at very low altitude, which corresponds to the inner region within the last-open field line of the rotating dipole in a vacuum. This model suggests a modification of the statistics for observed {gamma}-ray pulsars: the number of sources with low inclination and viewing angles increases compared with previous estimates.

  3. 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.

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. X-ray Polarization of Supernova Remnants and Pulsar-Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Reynolds, Stephen P.

    2011-09-01

    A dozen or more young shell supernova remnants (SNRs) show fast shocks and hard X-ray continuum emission best interpreted as synchrotron emission. The X-ray emission from pulsar-wind nebulae (PWNe) is entirely synchrotron. Radio emission from young SNRs is polarized at typical levels of 5 -- 15%, while that from PWNe can reach 50% polarization or more. Thus extended polarized X-ray emission is expected for both classes of source. Its detection would confirm beyond any doubt the synchrotron interpretation for those SNR X-ray continua. It will allow the inference of the degree of order in the magnetic field in X-ray emitting regions, along with the spatial orientation of the ordered component. Fractional polarizations may either be higher in X-rays than radio, due to the absence of any Faraday effects at X-ray wavelengths, or lower if magnetic fields are less ordered in (generally smaller) X-ray emitting regions. Efficient particle acceleration in SNRs can result in amplification of the magnetic field by orders of magnitude. The degree of order expected in such amplified fields is unknown; if fields are highly turbulent, no net polarization may survive. I shall review prospects for detecting polarized X-ray emission from SNRs and PWNe and what we stand to learn from detections or upper limits.

  9. NEW X-RAY OBSERVATIONS OF THE GEMINGA PULSAR WIND NEBULA

    SciTech Connect

    Pavlov, George G.; Bhattacharyya, Sudip; Zavlin, Vyacheslav E. E-mail: sudip@tifr.res.i

    2010-05-20

    Previous observations of the middle-aged pulsar Geminga with XMM-Newton and Chandra have shown an unusual pulsar wind nebula (PWN), with a 20'' long central (axial) tail directed opposite to the pulsar's proper motion and two 2' long, bent lateral (outer) tails. Here, we report on a deeper Chandra observation (78 ks exposure) and a few additional XMM-Newton observations of the Geminga PWN. The new Chandra observation has shown that the axial tail, which includes up to three brighter blobs, extends at least 50'' (i.e., 0.06d{sub 250} pc) from the pulsar (d{sub 250} is the distance scaled to 250 pc). It also allowed us to image the patchy outer tails and the emission in the immediate vicinity of the pulsar with high resolution. The PWN luminosity, L{sub 0.3-8{sub keV}} {approx} 3 x 10{sup 29} d {sup 2}{sub 250} erg s{sup -1}, is lower than the pulsar's magnetospheric luminosity by a factor of 10. The spectra of the PWN elements are rather hard (photon index {Gamma} {approx} 1). Comparing the two Chandra images, we found evidence of PWN variability, including possible motion of the blobs along the axial tail. The X-ray PWN is the synchrotron radiation from relativistic particles of the pulsar wind (PW); its morphology is connected with the supersonic motion of Geminga. We speculate that the outer tails are either a sky projection of the limb-brightened boundary of a shell formed in the region of contact discontinuity, where the wind bulk flow is decelerated by shear instability, or polar outflows from the pulsar bent by the ram pressure from the interstellar medium. In the former case, the axial tail may be a jet emanating along the pulsar's spin axis, perhaps aligned with the direction of motion. In the latter case, the axial tail may be the shocked PW collimated by ram pressure.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. PSR B0656+14: A Pulsar Wind Nebulae or a Dust Scattering Halo?

    NASA Astrophysics Data System (ADS)

    Birzan, Laura; Pavlov, George; Kargaltsev, Oleg

    2015-08-01

    PSR B0656+14 is a middle-aged pulsar with a characteristic age of 110 kyr. Using Chandra data, we have searched for a pulsar wind nebula (PWN) in this system and found evidence of extended emission in a 3--20 arcsec annulus around the pulsar, with a luminosity of about 10^{29} erg/s in the 0.5-8 keV band, which is 0.07 of the non-thermal pulsar luminosity. The radial extent of the extended emission is comparable to the expected bow-shock radius, but the putative PWN does not show a bow-shock structure. However, the spectrum of the extended emission appears to be very soft, much softer than the X-ray spectra of other PWN. We discuss several possible explanations for the soft extended emission, including the unusual properties of the pulsarand a dust scattering halo.

  19. 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.

  20. 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.

  1. Modeling statistical properties of the X-ray emission from aged pulsar wind nebulae

    NASA Astrophysics Data System (ADS)

    Bandiera, R.

    2014-03-01

    The number of known pulsar wind nebulae (PWNe) has recently increased considerably, and the majority of them are now middle-age objects. Recent studies have shown a clear correlation of both X-ray luminosity and size with the PWN age, but fail in providing a thorough explanation of the observed trends. Here I propose a different approach to these effects, based on the hypothesis that the observed trends do not simply reproduce the evolution of a ``typical'' PWN, but are a combined effect of PWNe evolving under different ambient conditions, the leading parameter being the ambient medium density. Using a simple analytic approach, I show that most middle-aged PWNe are more likely observable during the reverberation phase, and I succeed in reproducing trends consistent with those observed, provided that the evolution of the X-ray emitting electrons remains adiabatic over the whole reverberation phase. As a direct consequence, I show that the X-ray spectra of older PWNe should be harder, also consistent with observations.

  2. Chandra Observations of the Elusive Pulsar Wind Nebula around PSR B0656+14

    NASA Astrophysics Data System (ADS)

    Bîrzan, L.; Pavlov, G. G.; Kargaltsev, O.

    2016-02-01

    PSR B0656+14 is a middle-aged pulsar with a characteristic age {τ }{{c}}=110 kyr and spin-down power \\dot{E}=3.8× {10}34 erg s-1. Using Chandra data, we searched for a pulsar wind nebula (PWN). We found evidence of an extended emission in a 3.″5-15″ annulus around the pulsar, with a luminosity {L}0.5-8 {keV}{{ext}}˜ 8× {10}28 erg s-1 (at the distance of 288 pc), which is a fraction of ˜0.05 of the nonthermal pulsar luminosity. If the extended emission is mostly due to a PWN, its X-ray effiency, {η }{{pwn}}={L}0.5-8 {keV}{{ext}}/\\dot{E}˜ 2× {10}-6, is lower than those of most other known PWNe, but similar to that of the middle-aged Geminga pulsar. The small radial extent and nearly round shape of the putative PWN can be expained if the pulsar is receding (or approaching) in the direction close to the line of sight. The very soft spectrum of the extended emission ({{Γ }}˜ 8) is much softer than those of typical PWNe; this could be explained by contribution from a faint dust scattering halo, which may dominate in the outer part of the extended emission.

  3. 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.

  4. Relaxation of Pulsar Wind Nebula via Current-Driven Kink Instability

    NASA Astrophysics Data System (ADS)

    Mizuno, Yosuke; Lyubarsky, Yuri; Nishikawa, Ken-Ichi; Hardee, Philip E.

    We have investigated the relaxation of a hydrostatic hot plasma column containing toroidal magnetic field by the Current-Driven (CD) kink instability as a model of pulsar wind nebulae. In our simulations the CD kink instability was excited by a small initial velocity perturbation and developed turbulent structure inside the hot plasma column. We demonstrated that, as envisioned by Begelman, the hoop stress declines and the initial gas pressure excess near the axis decreases. The magnetization parameter "σ", the ratio of the magnetic energy to the thermal energy for a hot plasma, declined from an initial value of 0.3 to about 0.01 when the CD kink instability saturated. Our simulations demonstrated that axisymmetric models strongly overestimate the elongation of the pulsar wind nebulae. Therefore, the previous requirement for an extremely low pulsar wind magnetization can be abandoned. The observed structure of the pulsar wind nebulae do not contradict the natural assumption that the magnetic energy flux still remains a good fraction of the total energy flux after dissipation of alternating fields.

  5. 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.

  6. 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''.

  7. 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.

  8. 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}.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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(+/-).

  14. 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.

  15. Resolving The Remarkable Vela Pulsar Wind Nebula In Space And Time With Chandra.

    NASA Astrophysics Data System (ADS)

    Kargaltsev, Oleg; Pavlov, G. G.; Durant, M.; Kropotina, J.; Levenfish, K.; Bykov, A. M.

    2011-09-01

    Early Chandra observations of the Vela pulsar wind nebula (PWN) have already revealed its rich and dynamic structure. Here we present the results of eleven 40 ks Chandra ACIS observations taken between July 2009 and September 2010. The animation reveals remarkable dynamics of the Vela pulsar jet which resembles a rotating cork-screw. The jet flow is subject to instabilities that give rise to bright blobs, which brighten and fade on a one week timescale. The overall jet shape remains preserved on the timescale of one-two months, but it can change dramatically on a one year timescale. The inner nebula structure is also highly variable. The bright inner counter-jet appears to be the most variable feature of the inner PWN, both in brightness and shape. There are also brightness enhancements (knots) that appear to move along the inner arc, which is apparently a brightened part of a torus. The very deep combined image shows that the X-ray emission extends as far as the radio emission in the equatorial plane and ahead of the moving pulsar. The PWN spectral map reveals an intricate spectral structure with very hard spectra of the PWN features near the pulsar. We compare the Vela spectral map with those we produced for other PWNe observed by Chandra. We discuss the implications of the resolved structure and variability in context of pulsar wind models. This work is supported by the by NASA through Chandra grant G09-0084B and by the Ministry of Education and Science of Russian Federation (Contract No. 11.G34.31.0001).

  16. The implications of a companion enhanced wind on millisecond pulsar production

    NASA Astrophysics Data System (ADS)

    Smedley, Sarah L.; Tout, Christopher A.; Ferrario, Lilia; Wickramasinghe, Dayal T.

    2016-09-01

    The most frequently seen binary companions to millisecond pulsars (MSPs) are helium white dwarfs (He WDs). The standard rejuvenation mechanism, in which a low- to intermediate-mass companion to a neutron star fills its Roche lobe between central hydrogen exhaustion and core helium ignition, is the most plausible formation mechanism. We have investigated whether the observed population can realistically be formed via this mechanism. We used the Cambridge STARS code to make models of Case B RLOF with Reimers' mass loss from the donor. We find that the range of initial orbital periods required to produce the currently observed range of orbital periods of MSPs is extremely narrow. To reduce this fine tuning, we introduce a companion enhanced wind (CEW) that strips the donor of its envelope more quickly so that systems can detach at shorter periods. Our models indicate that the fine tuning can be significantly reduced if a CEW is active. Because significant mass is lost owing to a CEW we expect some binary pulsars to accrete less than the 0.1 M_{⊙} needed to spin them up to millisecond periods. This can account for mildly recycled pulsars present along the entire Mc-Porb relation. Systems with P_spin > 30 ms are consistent with this but too few of these mildly recycled pulsars have yet been observed to make a significant comparison.

  17. X-Ray Thread G0.13-0.11: A Pulsar Wind Nebula?

    NASA Astrophysics Data System (ADS)

    Wang, Q. Daniel; Lu, Fangjun; Lang, Cornelia C.

    2002-12-01

    We have examined Chandra observations of the recently discovered X-ray thread G0.13-0.11 in the Galactic center Radio Arc region. Part of the Chandra data was studied by Yusef-Zadeh, Law, & Wardle, who reported the detection of 6.4 keV line emission in this region. We find, however, that this line emission is not associated with G0.13-0.11. The X-ray spectrum of G0.13-0.11 is well-characterized by a simple power law with an energy slope of 1.8+0.7-0.4 (90% confidence uncertainties). Similarly, the X-ray spectrum of the pointlike source embedded in G0.13-0.11 has a power-law energy slope of 0.9+0.9-0.7. The 2-10 keV band luminosities of these two components are ~3.2×1033 ergs s-1 (G0.13-0.11) and ~7.5×1032 ergs s-1 (point source) at the Galactic center distance of 8 kpc. The morphological, spectral, and luminosity properties strongly indicate that G0.13-0.11 represents the leading edge of a pulsar wind nebula, produced by a pulsar (point source) moving in a strong magnetic field environment. The main body of this pulsar wind nebula is likely traced by a bow-shaped radio feature, which is apparently bordered by G0.13-0.11 and is possibly associated with the prominent nonthermal radio filaments of the Radio Arc. We speculate that young pulsars may be responsible for various unique nonthermal filamentary radio and X-ray features observed in the Galactic center region.

  18. 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

  19. 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.

  20. 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.

  1. Radio Observations of the Pulsar Wind Nebula HESS J1303-631 with ATCA

    NASA Astrophysics Data System (ADS)

    Sushch, Iurii; Oya, Igor; Schwanke, Ullrich; Johnston, Simon; Dalton, Matthew

    2016-04-01

    Based on its enregy-dependent morphology the initially unidentified very high energy (VHE; E > 100 GeV) gamma-ray source HESS J1303-631 was recently associated with the pulsar PSR J1301-6305. Subsequent detection of X-ray and GeV counterparts further supports the identification of the H.E.S.S. source as evolved pulsar wind nebula (PWN). Recent radio observations of the PSR J1301-6305 region with ATCA dedicated to search for the radio counterpart of HESS J1303-631 are reported here. Observations at 5.5 GHz and 7.5 GHz do not reveal any extended emission associated with the pulsar. The analysis of the archival 1.384 GHz and 2.368 GHz data also does not show any significant emission. The 1.384 GHz data reveal a hint of an extended shell-like emission in the same region which might be a supernova remnant. The implications of the non-detection at radio wavelengths on the nature and evolution of the PWN as well as the possibility of the SNR candidate being a birth place of PSR J1301-6305 are discussed.

  2. High resolution radio imaging study of the Pulsar Wind Nebula MSH 15-52

    NASA Astrophysics Data System (ADS)

    Leung, W.-Y.; Ng, C.-Y.

    2016-06-01

    We present a new high-resolution radio imaging study of the pulsar wind nebula (PWN) MSH 15-52, also dubbed as "the hand of God", with the Australia Telescope Compact Array observations. The system is powered by a young and energetic radio pulsar B1509-58 with high spin down luminosity of E(dot) = 2 x 10^37 erg/s. Previous X-ray images have shown that the PWN has a complex hand-shape morphology extending over 10 pc with features like jets, arc, filaments and enhanced emission knots in the HII region RCW 89. The new 6cm and 3cm radio images show different morphology than the X-ray counterpart. No radio counterpart of the X-ray jet is detected, instead we found enhanced emission in a sheath surrounding the jet. Additional small-scale features including a polarized linear filament next to the pulsar have also been discovered. Our polarisation measurements show that the intrinsic orientation of magnetic field aligns with the sheath. Finally, spectral analysis results indicate a steep spectrum for the system, which is rather unusual among PWNe. Implications of these findings will be discussed. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This work is supported by an ECS grant under HKU 709713P.

  3. 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.

  4. Non-thermal emission from relativistic MHD simulations of pulsar wind nebulae: from synchrotron to inverse Compton

    NASA Astrophysics Data System (ADS)

    Volpi, D.; Del Zanna, L.; Amato, E.; Bucciantini, N.

    2008-07-01

    Aims: We develop a set of diagnostic tools for synchrotron-emitting sources, presented in a previous paper, to include a computation of inverse-Compton radiation from the same relativistic particles that give rise to the synchrotron emission. For the first time, we then study the gamma-ray emission properties of Pulsar Wind Nebulae, in the context of the axisymmetric jet-torus scenario. Methods: We evolve the relativistic MHD equations and the maximum energy of the emitting particles, including adiabatic and synchrotron losses along streamlines. The particle energy distribution function is split into two components: one corresponds to radio-emitting electrons, which are interpreted to be a relic population that is born at the outburst of the supernova, and the other is associated with a wind population that is continuously accelerated at the termination shock and emits up to the gamma-ray band. The inverse Compton emissivity is calculated using the general Klein-Nishina differential cross-section and three different photon targets for the relativistic particles are considered: the nebular synchrotron photons, photons associated with the far-infrared thermal excess, and the cosmic microwave background. Results: When the method is applied to the simulations that match the optical and X-ray morphology of the Crab Nebula, the overall synchrotron spectrum can only be fitted assuming an excess of injected particles and a steeper power law (E-2.7) with respect to previous models. The resulting TeV emission has then the correct shape but is in excess of the data. This is related to the magnetic-field structure in the nebula, derived using simulations: in particular, the field is strongly compressed close to the termination shock, but with a lower than expected volume average. The jet-torus structure is also found to be visible clearly in high-resolution gamma-ray synthetic maps. We present a preliminary exploration of time variability in X- and gamma-rays. We find

  5. 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.

  6. Infrared imaging and polarimetric observations of the pulsar wind nebula in SNR G21.5-0.9

    NASA Astrophysics Data System (ADS)

    Zajczyk, A.; Gallant, Y. A.; Slane, P.; Reynolds, S. P.; Bandiera, R.; Gouiffès, C.; Le Floc'h, E.; Comerón, F.; Koch Miramond, L.

    2012-06-01

    We present infrared observations of the supernova remnant G21.5-0.9 with the Very Large Telescope, the Canada-France-Hawaii Telescope and the Spitzer Space Telescope. Using the VLT/ISAAC camera equipped with a narrow-band [Fe II] 1.64 μm filter the entire pulsar wind nebula in SNR G21.5-0.9 was imaged. This led to detection of iron line-emitting material in the shape of a broken ring-like structure following the nebula's edge. The detected emission is limb-brightened. We also detect the compact nebula surrounding PSR J1833-1034, both through imaging with the CFHT/AOB-KIR instrument (K' band) and the IRAC camera (all bands) and also through polarimetric observations performed with VLT/ISAAC (Ks band). The emission from the compact nebula is highly polarised with an average value of the linear polarisation fraction PL^avg ≃ 0.47, and the swing of the electric vector across the nebula can be observed. The infrared spectrum of the compact nebula can be described as a power law of index αIR = 0.7 ± 0.3, and suggests that the spectrum flattens between the infrared and X-ray bands.

  7. 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).

  8. 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.

  9. Distance and age of the pulsar wind nebula 3C 58

    NASA Astrophysics Data System (ADS)

    Kothes, R.

    2013-12-01

    Context. A growing number of researchers present evidence that the pulsar wind nebula 3C 58 is much older than predicted by its proposed connection to the historical supernova of A.D. 1181. There is also a great diversity of arguments. The strongest of these arguments rely heavily on the assumed distance of 3.2 kpc determined with H i absorption measurements. Aims: This publication aims at determining a more accurate distance for 3C 58 and at re-evaluating the arguments for an older age. Methods: I have re-visited the distance determination of 3C 58 based on new H i data from the Canadian Galactic Plane Survey and our recent improvements in the knowledge of the rotation curve of the outer Milky Way Galaxy. I also used newly determined distances to objects in the neighbourhood, which are based on direct measurements by trigonometric parallax. Results: I have derived a new more reliable distance estimate of 2 kpc for 3C 58. This makes the connection between the pulsar wind nebula and the historical event from A.D. 1181 once again much more viable. With permission of Crown Copyright 2013 NRC Canada.

  10. 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

  11. 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.

  12. 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.

  13. 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).

  14. Search for Very High Energy Gamma-ray Emission from Pulsar-Pulsar Wind Nebula Systems with the MAGIC Telescope

    NASA Astrophysics Data System (ADS)

    Anderhub, H.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Baixeras, C.; Balestra, S.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Becker, J. K.; Bednarek, W.; Berger, al K.; Bernardini, E.; Biland, A.; Bock, R. K.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Britzger, D.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Commichau, S.; Contreras, J. L.; Cortina, J.; Costado, M. T.; Covino, S.; Dazzi, F.; De Angelis, A.; de Cea del Pozo, E.; De los Reyes, R.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Errando, M.; Ferenc, D.; Fernández, E.; Firpo, R.; Fonseca, M. V.; Font, L.; Galante, N.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Godinovic, N.; Goebel, F.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Hsu, C. C.; Jogler, T.; Klepser, S.; Kranich, D.; La Barbera, A.; Laille, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Lorenz, E.; Majumdar, P.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moles, M.; Moralejo, A.; Nieto, D.; Nilsson, K.; Ninkovic, J.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Pasanen, M.; Pascoli, D.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Robert, A.; Rügamer, S.; Saggion, A.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Stark, L. S.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Tescaro, D.; Teshima, M.; Torres, D. F.; Turini, N.; Vankov, H.; Wagner, R. M.; Zabalza, V.; Zandanel, F.; Zanin, R.; Zapatero, J.; Cognard, I.

    2010-02-01

    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.

  15. 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.

  16. Multi-wavelength observations of pulsar wind nebulae and composite supernova remnants

    NASA Astrophysics Data System (ADS)

    Temim, Tea

    Multi-wavelength studies of pulsar wind nebulae (PWNe) and supernova remnants (SNRs) lead to a better understanding of their evolutionary development, the interaction of supernovae (SNe) and pulsar winds with their surroundings, and nucleosynthesis and production and processing of dust grains by SNe. PWNe and composite supernova remnants, in particular, are unique laboratories for the study of the energetic pulsar winds, particle injection processes, and the impact of PWNe on the evolving SNR. They provide information on SNR shock properties, densities and temperatures, and the chemical composition and the ionization state of the material ejected by SNe. SNRs also serve as laboratories for the study of dust production and processing in SNe. While X-ray observations yield important information about the SN progenitor, hot gas properties, SN explosion energy, and the surrounding interstellar medium (ISM), the IR can provide crucial information about the faint non-thermal emission, continuum emission from dust, and forbidden line emission from SN ejecta. Combining observations at a wide range of wavelengths provides a more complete picture of the SNR development and helps better constrain current models describing a SNR's evolution and its impact on the surrounding medium. This thesis focuses on a multi-wavelength study of PWNe in various stages of their evolution and investigates their interaction with the expanding SN ejecta and dust and the SNR reverse shock. The study of these interactions can provide important information on the SNR properties that may otherwise be unobservable. The work in this thesis has been carried out under the supervision of Patrick Slane at the Harvard-Smithsonian Center for Astrophysics, and Charles E. Woodward and Rebert D. Gehrz at the University of Minnesota. The first part of the thesis summarizes the evolution and observational properties of SNRs and PWNe, with a focus on the evolution of young PWNe that are sweeping up inner SN

  17. The Infrared Detection of the Pulsar Wind Nebula in the Galactic Supernova Remnant 3C 58

    NASA Astrophysics Data System (ADS)

    Slane, P.; Helfand, D. J.; Reynolds, S. P.; Gaensler, B. M.; Lemiere, A.; Wang, Z.

    2008-03-01

    We present infrared observations of 3C 58 with the Spitzer Space Telescope and the Canada-France-Hawaii Telescope. Using the IRAC camera, we have imaged the entire source, which results in clear detections of the nebula at 3.6 and 4.5 μm. The derived flux values are consistent with extrapolation of the X-ray spectrum to the infrared band, demonstrating that any cooling break in the synchrotron spectrum must occur near the soft X-ray band. We also detect the torus surrounding PSR J0205+6449, the 65 ms pulsar that powers 3C 58. The torus spectrum requires a break between the infrared and X-ray bands, and perhaps multiple breaks. This complex spectrum, which is an imprint of the particles injected into the nebula, has considerable consequences for the evolution of the broadband spectrum of 3C 58. We illustrate these effects and discuss the impact of these observations on the modeling of broadband spectra of pulsar wind nebulae.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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"

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. GAMMA-RAY AND HARD X-RAY EMISSION FROM PULSAR-AIDED SUPERNOVAE AS A PROBE OF PARTICLE ACCELERATION IN EMBRYONIC PULSAR WIND NEBULAE

    SciTech Connect

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

    2015-05-20

    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.

  19. Observations of high energy emission from pulsar wind nebulae using VERITAS

    NASA Astrophysics Data System (ADS)

    Millis, John P.

    2008-09-01

    Broadband emission has been detected from several pulsar wind nebulae (PWNe), however the physical processes that govern the dynamics and mechanisms for the emission are not well understood. Theoretical models have been developed to attempt to explain the emission seen from these objects, and they make specific predictions about the spectrum and luminosity that we can expect to see in various wavelengths. Apparently, PWNe are thought to be strong gamma ray emitters, and this is reinforced by the strong emission seen from the Crab nebula. However, observations of other PWNe in high energy gamma rays has only recently been undertaken. VERITAS (the Very Energetic Radiation Imaging Telescope Array System) recently observed several of these sources in an attempt to detect very high energy gamma rays created in their nebulae. Results of observations of the Crab nebula, the standard source of observation for ground based gamma ray observatories and the most studied of all PWNe, are reported here as a comparison for 4 other northern hemisphere PWNe that were observed. This work will describe the nature of these objects while outlining the work being done to describe the emission detected from various sources. The technical details of the analysis techniques employed to search for high energy gamma rays using the VERITAS array is also presented. Ultimately only the Crab Nebula was detected at high significance. However the best integral flux upper- limits above 250 GeV to date are determined for 3C 58 (1.6% Crab Nebula flux), the Boomerang Nebula (1.5% Crab Nebula flux), PSR J0631+1036 (2.1% Crab Nebula flux) and PSR J1930+1852 (3.7 % Crab Nebula flux).

  20. 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.

  1. 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.

  2. Cold ultrarelativistic pulsar winds as potential sources of galactic gamma-ray lines above 100 GeV

    NASA Astrophysics Data System (ADS)

    Aharonian, F.; Khangulyan, D.; Malyshev, D.

    2012-11-01

    Context. The evidence of line-like spectral features above 100 GeV, in particular at 130 GeV, which have been recently reported from some parts of the Galactic plane, poses serious challenges for any interpretation of this surprise discovery. It is generally believed that the unusually narrow profile of the spectral line cannot be explained by conventional processes in astrophysical objects, and, if real, is likely to be associated with dark matter. Aims: In this paper we argue that cold ultrarelativistic pulsar winds can be alternative sources of very narrow gamma-ray lines. Methods: We demonstrate that Comptonization of a cold ultrarelativistic electron-positron pulsar wind in the deep Klein-Nishina regime can readily provide very narrow (ΔE/E ≤ 0.2) distinct gamma-ray line features. To verify this prediction, we produced photon-count maps based on the Fermi LAT data in the energy interval 100 to 140 GeV. Results: We confirm earlier reports of the presence of marginal gamma-ray line-like signals from three regions of the Galactic plane. Although the maps show some structure inside these regions, unfortunately the limited photon statistics do not allow any firm conclusion in this regard. Conclusions: The confirmation of 130 GeV line emission by low-energy threshold atmospheric Cherenkov telescope systems, in particular by the new 28 m diameter dish of the H.E.S.S. array, would be crucial for resolving the spatial structure of the reported hotspots, and thus for distinguishing between the dark matter and pulsar origins of the "Fermi Lines".

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. FORMATION OF BINARY MILLISECOND PULSARS BY ACCRETION-INDUCED COLLAPSE OF WHITE DWARFS UNDER WIND-DRIVEN EVOLUTION

    SciTech Connect

    Ablimit, Iminhaji; Li, Xiang-Dong

    2015-02-20

    Accretion-induced collapse (AIC) of massive white dwarfs (WDs) has been proposed to be an important channel to form binary millisecond pulsars (MSPs). Recent investigations on thermal timescale mass transfer in WD binaries demonstrate that the resultant MSPs are likely to have relatively wide orbit periods (≳ 10 days). Here we calculate the evolution of WD binaries taking into account the excited wind from the companion star induced by X-ray irradiation of the accreting WD, which may drive rapid mass transfer even when the companion star is less massive than the WD. This scenario can naturally explain the formation of the strong-field neutron star in the low-mass X-ray binary 4U 1822–37. After AIC the mass transfer resumes when the companion star refills its Roche lobe, and the neutron star is recycled owing to mass accretion. A large fraction of the binaries will evolve to become binary MSPs with an He WD companion, with the orbital periods distributed between ≳ 0.1 days and ≲ 30 days, while some of them may follow the cataclysmic variable-like evolution toward very short orbits. If we instead assume that the newborn neutron star appears as an MSP and that part of its rotational energy is used to ablate its companion star, the binaries may also evolve to be the redback-like systems.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    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 A.

    2015-03-01

    We obtained six observations of PSR J1741-2054 using the Chandra ACIS-S detector totaling ∼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 μ =109+/- 10 mas y{{r}-1} in a direction consistent with the symmetry axis of the observed Hα 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 Γ = 2.68 ± 0.04, plus a blackbody with an emission radius of (4.5-2.5+3.2){{d}0.38} km, for a DM-estimated distance of 0.38{{d}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 Γ = 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.

  6. 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.

  7. 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

  8. GLAST 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. 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 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. In particular, the GLAST Large Area Telescope, a successor to EGRET on the Compton Observatory, will provide an excellent complement to H.E.S.S. for the study of the highest-energy emissions powered by neutron stars.

  9. 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.

  10. 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.

  11. 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

  12. DEEP CHANDRA OBSERVATIONS OF THE CRAB-LIKE PULSAR WIND NEBULA G54.1+0.3 AND SPITZER SPECTROSCOPY OF THE ASSOCIATED INFRARED SHELL

    SciTech Connect

    Temim, Tea; Slane, Patrick; Raymond, John C.; Reynolds, Stephen P.; Borkowski, Kazimierz J.

    2010-02-10

    G54.1+0.3 is a young pulsar wind nebula (PWN), closely resembling the Crab, for which no thermal shell emission has been detected in X-rays. Recent Spitzer observations revealed an infrared (IR) shell containing a dozen point sources arranged in a ring-like structure, previously proposed to be young stellar objects. An extended knot of emission located in the NW part of the shell appears to be aligned with the pulsar's X-ray jet, suggesting a possible interaction with the shell material. Surprisingly, the IR spectrum of the knot resembles the spectrum of freshly formed dust in Cas A, and is dominated by an unidentified dust emission feature at 21 {mu}m. The spectra of the shell also contain various emission lines and show that some are significantly broadened, suggesting that they originate in rapidly expanding supernova (SN) ejecta. We present the first evidence that the PWN is driving shocks into expanding SN ejecta and we propose an alternative explanation for the origin of the IR emission in which the shell is composed entirely of SN ejecta. In this scenario, the freshly formed SN dust is being heated by early-type stars belonging to a cluster in which the SN exploded. Simple dust models show that this interpretation can give rise to the observed shell emission and the IR point sources.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. Evolution of vaporizing pulsars

    NASA Technical Reports Server (NTRS)

    Mccormick, P.

    1994-01-01

    We construct evolutional scenarios for LMXB's using a simplified stellar model. We discuss the origin and evolution of short-period, low mass binary pulsars with evaporating companions. We suggest that these systems descend from low-mass X-ray binaries and that angular momentum loss mainly due to evaporative wind drives their evolution. We derive limits on the energy and angular momentum carried away by the wind based on the observed low eccentricity. In our model the companion remains near contact, and its quasiadiabatic expansion causes the binary to expand. Short-term oscillations of the orbital period may occur if the Roche-lobe overflow forms an evaporating disk.

  1. 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.

  2. X-Ray Observations of the Supernova Remnant CTB 87 (G74.9+1.2): An Evolved Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Matheson, H.; Safi-Harb, S.; Kothes, R.

    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 ~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 ~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 H = 1.38 (1.21-1.57) × 1022 cm-2 (90% confidence). The total X-ray luminosity of the source is ~1.6 × 1034 erg s-1 at an assumed distance of 6.1 kpc, with ~2% and 6% contribution from the point source and compact nebula, respectively. The observed properties suggest that CTB 87 is an evolved (~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_0 < 0.2 D^{-1/2}_{6.1} cm-3), likely caused by a stellar wind bubble blown by the progenitor star.

  3. 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.

  4. 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.

  5. Pulsar activation by the interstellar medium?

    NASA Technical Reports Server (NTRS)

    Michel, F. Curtis

    1987-01-01

    Recent work suggests that rotating magnetized neutron stars (i.e., pulsar models) trap plasma instead of emitting it. The trapping arises because nonneutral plasma can be stably trapped within such a magnetosphere provided the overall system charge is nonzero. It has been argued that particles from the interstellar medium would discharge this system, thereby presumably reactivating the system as a pulsar. However, radiation pressure either precludes such discharging (requiring an alternative source of ionization) or pulsar magnetic moments must be almost perfectly aligned with the spin axis (a revolutionary alternative). Indeed, the pulsars for which particles could reach the neutron star are those with periods of at least 3 sec. But those periods are where pulsars become inactive, not active. Conceivably, nulling might represent intermittent accretion of the interstellar medium.

  6. On flow phenomena that emit X-rays in hot star winds

    NASA Technical Reports Server (NTRS)

    Feldmeier, A.; Puls, J.; Kudritzki, R. P.; Pauldrach, A. W. A.; Owocki, S. P.; Reile, C.; Palsa, R.

    1996-01-01

    The X-ray emission from O stars may originate from instability-generated shocks in their stellar winds. Previous numerical simulations that assumed the wind to be isothermal could only draw limited conclusions concerning this emission. Calculations that include the energy transfer in the wind are presented. They confirm that up to a few stellar radii, radiative cooling is efficient which implies that the shock cooling zones are short in comparison with the dynamical lengths. At larger radii, the wind structure changes as all the shocks are destroyed due to a broadening of their cooling zones. The following flow phenomena are discussed as possible X-ray sources: inner radiative shock; shock merging, outer adiabatic shocks, remaining hot gas from shock destruction, and an outer corona.

  7. 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.

  8. Gamma-Ray Pulsar Revolution

    NASA Astrophysics Data System (ADS)

    Caraveo, Patrizia A.

    2014-08-01

    Isolated neutron stars (INSs) were the first sources identified in the field of high-energy gamma-ray astronomy. In the 1970s, only two sources had been identified, the Crab and Vela pulsars. However, although few in number, these objects were crucial in establishing the very concept of a gamma-ray source. Moreover, they opened up significant discovery space in both the theoretical and phenomenological fronts. The need to explain the copious gamma-ray emission of these pulsars led to breakthrough developments in understanding the structure and physics of neutron star (NS) magnetospheres. In parallel, the 20-year-long chase to understand the nature of Geminga unveiled the existence of a radio-quiet, gamma-ray-emitting INS, adding a new dimension to the INS family. We are living through an extraordinary time of discovery. The current generation of gamma-ray detectors has vastly increased the population of known gamma-ray-emitting NSs. The 100 mark was crossed in 2011, and we are now over 150. The gamma-ray-emitting NS population exhibits roughly equal numbers of radio-loud and radio-quiet young INSs, plus an astonishing, and unexpected, group of isolated and binary millisecond pulsars (MSPs). The number of MSPs is growing so rapidly that they are on their way to becoming the most numerous members of the family of gamma-ray-emitting NSs. Even as these findings have set the stage for a revolution in our understanding of gamma-ray-emitting NSs, long-term monitoring of the gamma-ray sky has revealed evidence of flux variability in the Crab Nebula as well as in the pulsed emission from PSR J2021+4026, challenging a four-decades-old, constant-emission paradigm. Now we know that both pulsars and their nebulae can, indeed, display variable emission.

  9. 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 (?)

  10. 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.

  11. Radio-quiet Gamma-ray Pulsars

    NASA Astrophysics Data System (ADS)

    Lin, Lupin Chun-Che

    2016-09-01

    A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog) known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400) of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on) are also specified to discuss their common and specific features.

  12. 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.

  13. 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)

  14. 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.

  15. Pulsar reenergization of old supernova remnant shells

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Fesen, Robert A.; Saken, Jon M.

    1989-01-01

    The morphology of several unusual composite remnants are suggested to be affected by previously unrecognized interactions between high-velocity pulsars and old SNR shells, and the case of CTB 80 is pointed out as a likely example of such interactions. The interactions generate a new class of 'composite remnants' and furnish a novel method for the derivation of kinematic distances and SNR ages; this technique is noted to be especially useful when the pulsar has a measured spindown age or proper motion. It is predicted that a number of pulsars may interact with 80-100 pc radius 'superbubbles' produced by the combined action of winds and supernovae in OB associations.

  16. 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.

  17. The origin of the X-ray-emitting object moving away from PSR B1259-63

    NASA Astrophysics Data System (ADS)

    Barkov, Maxim V.; Bosch-Ramon, Valentí

    2016-02-01

    A mysterious X-ray-emitting object has been detected moving away from the high-mass gamma-ray binary PSR B1259-63, which contains a non-accreting pulsar and a Be star whose winds collide forming a complex interaction structure. Given the strong eccentricity of this binary, the interaction structure should be strongly anisotropic, which together with the complex evolution of the shocked winds, could explain the origin of the observed moving X-ray feature. We propose here that a fast outflow made of a pulsar-stellar wind mixture is always present moving away from the binary in the apastron direction, with the injection of stellar wind occurring at orbital phases close to periastron passage. This outflow periodically loaded with stellar wind would move with a high speed, and likely host non-thermal activity due to shocks, on scales similar to those of the observed moving X-ray object. Such an outflow is thus a very good candidate to explain this X-ray feature. This, if confirmed, would imply pulsar-to-stellar wind thrust ratios of ˜0.1, and the presence of a jet-like structure on the larger scales, up to its termination in the interstellar medium.

  18. 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

  19. 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.

  20. Deep optical observations of the γ-ray pulsar J0357+3205

    NASA Astrophysics Data System (ADS)

    Kirichenko, A.; Danilenko, A.; Shibanov, Yu.; Shternin, P.; Zharikov, S.; Zyuzin, D.

    2014-04-01

    Context. A middle-aged radio-quiet pulsar J0357+3205 was discovered in gamma rays with Fermi and later in X-rays with Chandra and XMM-Newton observatories. It produces an unusual thermally emitting pulsar wind nebula that is observed in X-rays. Aims: Deep optical observations were obtained to search for the pulsar optical counterpart and its nebula using the Gran Telescopio Canarias (GTC). Methods: The direct imaging mode in the Sloan g' band was used. Archival X-ray data were reanalysed and compared with the optical data. Results: No pulsar optical counterpart was detected down to g'≥slant 28.1m. No pulsar nebula was identified in the optical either. We confirm early results that the X-ray spectrum of the pulsar consists of a nonthermal power-law component of the pulsar magnetospheric origin dominating at high energies and a soft thermal component from the neutron star surface. Using magnetised, partially ionised hydrogen atmosphere models in X-ray spectral fits, we found that the thermal component can come from the entire surface of the cooling neutron star with a temperature of 36+8-6 eV, making it one of the coldest among cooling neutron stars known. The surface temperature agrees with the standard neutron star cooling scenario. The optical upper limit does not put any additional constraints on the thermal component, however it does imply a strong spectral break for the nonthermal component between the optical and X-rays as is observed in other middle-aged pulsars. Conclusions: The thermal emission from the entire surface of the neutron star very likely dominates the nonthermal emission in the UV range. Observations of PSR J0357+3205 in this range are promising to put more stringent constraints on its thermal properties. Based on observations made with the Gran Telescopio Canarias (GTC), instaled in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma under Programme GTC3-12BMEX

  1. Double Pulsar: A magnetopause in the double-pulsar binary system

    NASA Astrophysics Data System (ADS)

    Graham-Smith, Francis; McLaughlin, Maura Ann

    2005-02-01

    One of the holy grails of pulsar astronomy was realized last year with the discovery of a double neutron-star binary system in which both stars are visible as radio pulsars. The stars in this highly relativistic system are in a 2.4-hour, mildly eccentric orbit and are separated by only 2.9 light seconds. The wind from one distorts the magnetosphere of the other, forming a comet-like shape similar to the terrestrial magnetosheath. In this article we describe the radio observations of this system, which illuminate the remarkable interactions between the two pulsars. We show how studying these interactions will greatly increase our understanding of pulsar energy budgets, winds and magnetospheric physics.

  2. 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..

  3. 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

  4. Radio pulsar disk electrodynamics

    SciTech Connect

    Michel, F.C.

    1983-03-01

    We outline the macroscopic physics of a disk close to an isolated, magnetized, rotating neutron star. It seems likely that such systems are formed from time to time in the universe. The neutron star acts as a Faraday disk dynamo, and the disk acts as both a load and a neutral sheet, permitting the polar cap current to return to the neutron star and also splitting a dipolar magnetic field into two monopolar halves. Michel and Dessler have proposed that such systems are radio pulsars. The dominant energy loss is from the stellar wind torque (giving a deceleration index n = 7/3), and the next contribution is dissipation in the ''auroral'' zones, where the current returns to the star in a sheet about 5 cm thick. The latter is comparable to the observed radio luminosities and is in reasonable accord with the data. The disk itself may be a source of visible radiation comparable to that in pulsed radiofrequency emission. As the pulsar ages, the disk expands and narrows into a ring, the plausible consequence of which could be cessation of pulsed emission at periods of a few seconds.

  5. 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.

  6. A periodically active pulsar giving insight into magnetospheric physics.

    PubMed

    Kramer, M; Lyne, A G; O'Brien, J T; Jordan, C A; Lorimer, D R

    2006-04-28

    PSR B1931+24 (J1933+2421) behaves as an ordinary isolated radio pulsar during active phases that are 5 to 10 days long. However, when the radio emission ceases, it switches off in less than 10 seconds and remains undetectable for the next 25 to 35 days, then switches on again. This pattern repeats quasi-periodically. The origin of this behavior is unclear. Even more remarkably, the pulsar rotation slows down 50% faster when it is on than when it is off. This indicates a massive increase in magnetospheric currents when the pulsar switches on, proving that pulsar wind plays a substantial role in pulsar spin-down. This allows us, for the first time, to estimate the magnetospheric currents in a pulsar magnetosphere during the occurrence of radio emission.

  7. Age Discrepancy Throws Pulsar Theories into Turmoil

    NASA Astrophysics Data System (ADS)

    2002-03-01

    Space Research at the Massachusetts Institute of Technology, another one of the researchers. By tracking the pulsar's motion for more than a decade, the astronomers were able to calculate that it is traveling through space at more than 500,000 miles per hour. At that speed, the pulsar required about 64,000 years to travel from its birthplace -- the site of the supernova explosion -- to its present location. That means, the astronomers say, that the pulsar is about 64,000 years old. This age, however, differs significantly from the age estimated by another method which has been used by astronomers for decades. This method uses measurements of the rotation rate of the neutron star and the tiny amount by which that rotation slows over time to arrive at an estimate called the pulsar's "characteristic age." For B1951+32, that method produced an estimated age of 107,000 years. "Now we have a pulsar that is much younger than we thought. In 2000, a different pulsar was shown to be significantly older than we thought. That means that some of the assumptions that have gone into estimating the ages of these objects are unjustified," Migliazzo said. The pulsar's rotation is thought to slow because the neutron star's powerful magnetic field acts as a giant dynamo, emitting light, radio waves and other electromagnetic radiation as the star rotates. The energy lost by emitting the radiation results in the star's rotation slowing down. Previous estimates of pulsar ages have assumed that all pulsars are born spinning much faster than we see them now, that the physical characteristics of the pulsar such as its mass and magnetic-field strength do not change with time, and that the slowdown rate can be estimated by applying the physics of a magnet spinning in a vacuum. "With one pulsar older than the estimates and one younger, we now realize that we have to question all three of these assumptions," said Gaensler. Further research, the scientists say, should help them understand more about

  8. X-Ray observations of ``γ-ray only'' pulsars

    NASA Astrophysics Data System (ADS)

    de Luca, A.; Marelli, M.; Caraveo, P. A.

    2011-08-01

    Fermi-LAT and AGILE have already detected more than 70 rotation-powered pulsars at GeV energies, opening a new era of pulsar physics. In particular, Fermi has unveiled the existence of a large population of Geminga-like pulsars, γ-ray bright but radio-silent. We used XMM-Newton, Chandra and Swift to study such new, γ-ray selected, pulsar population and to compare its X-ray behaviour with that of the radio pulsars. While radio-loud and radio-quiet pulsars need not to be different objects, their different viewing geometry with respect to the observer does influence the ratio between γ and X-ray emissions. When plotting the distance-indipendent γ to X-ray flux ratios as a function of the pulsars' rotational energy losses, one immediately sees that pulsars with similar energetics have Fγ/FX spanning 3 decades. Such spread, most probably stemming from vastly different geometrical configurations of the X and γ-ray emitting regions, defies any straightforward interpretation of the plot. We find that, on average, radio-quiet pulsars do have higher values of Fγ/FX, implying an intrinsec faintness of their X-ray emission and/or a different geometrical configuration.

  9. 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.

  10. 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

  11. The pulsar planet production process

    NASA Technical Reports Server (NTRS)

    Phinney, E. S.; Hansen, B. M. S.

    1993-01-01

    Most plausible scenarios for the formation of planets around pulsars end with a disk of gas around the pulsar. The supplicant author then points to the solar system to bolster faith in the miraculous transfiguration of gas into planets. We here investigate this process of transfiguration. We derive analytic sequences of quasi-static disks which give good approximations to exact solutions of the disk diffusion equation with realistic opacity tables. These allow quick and efficient surveys of parameter space. We discuss the outward transfer of mass in accretion disks and the resulting timescale constraints, the effects of illumination by the central source on the disk and dust within it, and the effects of the widely different elemental compositions of the disks in the various scenarios, and their extensions to globular clusters. We point out where significant uncertainties exist in the appropriate grain opacities, and in the effect of illumination and winds from the neutron star.

  12. 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.

  13. Ensemble Pulsar Time Scale

    NASA Astrophysics Data System (ADS)

    Yin, D. S.; Gao, Y. P.; Zhao, S. H.

    2016-05-01

    Millisecond pulsars can generate another type of time scale that is totally independent of the atomic time scale, because the physical mechanisms of the pulsar time scale and the atomic time scale are quite different from each other. Usually the pulsar timing observational data are not evenly sampled, and the internals between data points range from several hours to more than half a month. What's more, these data sets are sparse. And all these make it difficult to generate an ensemble pulsar time scale. Hence, a new algorithm to calculate the ensemble pulsar time scale is proposed. Firstly, we use cubic spline interpolation to densify the data set, and make the intervals between data points even. Then, we employ the Vondrak filter to smooth the data set, and get rid of high-frequency noise, finally adopt the weighted average method to generate the ensemble pulsar time scale. The pulsar timing residuals represent clock difference between the pulsar time and atomic time, and the high precision pulsar timing data mean the clock difference measurement between the pulsar time and atomic time with a high signal to noise ratio, which is fundamental to generate pulsar time. We use the latest released NANOGRAV (North American Nanohertz Observatory for Gravitational Waves) 9-year data set to generate the ensemble pulsar time scale. This data set is from the newest NANOGRAV data release, which includes 9-year observational data of 37 millisecond pulsars using the 100-meter Green Bank telescope and 305-meter Arecibo telescope. We find that the algorithm used in this paper can lower the influence caused by noises in timing residuals, and improve long-term stability of pulsar time. Results show that the long-term (> 1 yr) frequency stability of the pulsar time is better than 3.4×10-15.

  14. 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.

  15. 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.

  16. 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.

  17. 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*.

  18. 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.

  19. 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.

  20. Elemental characterization of particulate matter emitted from biomass burning: Wind tunnel derived source profiles for herbaceous and wood fuels

    NASA Astrophysics Data System (ADS)

    Turn, S. Q.; Jenkins, B. M.; Chow, J. C.; Pritchett, L. C.; Campbell, D.; Cahill, T.; Whalen, S. A.

    1997-02-01

    Particulate matter emitted from wind tunnel simulations of biomass burning for five herbaceous crop residues (rice, wheat and barley straws, corn stover, and sugar cane trash) and four wood fuels (walnut and almond prunings and ponderosa pine and Douglas fir slash) was collected and analyzed for major elements and water soluble species. Primary constituents of the particulate matter were C, K, Cl, and S. Carbon accounted for roughly 50% of the herbaceous fuel PM and about 70% for the wood fuels. For the herbaceous fuels, particulate matter from rice straw in the size range below 10 μm aerodynamic diameter (PM10) had the highest concentrations of both K (24%) and Cl, (17%) and barley straw PM10 contained the highest sulfur content (4%). K, Cl, and S were present in the PM of the wood fuels at reduced levels with maximum concentrations of 6.5% (almond prunings), 3% (walnut prunings), and 2% (almond prunings), respectively. Analysis of water soluble species indicated that ionic forms of K, Cl, and S made up the majority of these elements from all fuels. Element balances showed K, Cl, S, and N to have the highest recovery factors (fraction of fuel element found in the particulate matter) in the PM of the elements analyzed. In general, chlorine was the most efficiently recovered element for the herbaceous fuels (10 to 35%), whereas sulfur recovery was greatest for the wood fuels (25 to 45%). Unique potassium to elemental carbon ratios of 0.20 and 0.95 were computed for particulate matter (PM10 K/C(e)) from herbaceous and wood fuels, respectively. Similarly, in the size class below 2.5 μm, high-temperature elemental carbon to bromine (PM2.5 C(eht)/Br) ratios of ˜7.5, 43, and 150 were found for the herbaceous fuels, orchard prunings, and forest slash, respectively. The molar ratios of particulate phase bromine to gas phase CO2 (PM10 Br/CO2) are of the same order of magnitude as gas phase CH3Br/CO2 reported by others.

  1. 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).

  2. 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.

  3. Toward an Empirical Theory of Pulsar Emission. XI. Understanding the Orientations of Pulsar Radiation and Supernova “Kicks”

    NASA Astrophysics Data System (ADS)

    Rankin, Joanna M.

    2015-05-01

    Two entwined problems have remained unresolved since pulsars were discovered nearly 50 yr ago: the orientation of their polarized emission relative to the emitting magnetic field and the direction of putative supernova “kicks” relative to their rotation axes. The rotational orientation of most pulsars can be inferred only from the (“fiducial”) polarization angle of their radiation, when their beam points directly at the Earth and the emitting polar fluxtube field is ∥ to the rotation axis. Earlier studies have been unrevealing owing to the admixture of different types of radiation (core and conal, two polarization modes), producing both ∥ or ⊥ alignments. In this paper we analyze some 50 pulsars having three characteristics: core radiation beams, reliable absolute polarimetry, and accurate proper motions (PMs). The “fiducial” polarization angle of the core emission, we then find, is usually oriented ⊥ to the PM direction on the sky. The primary core emission is polarized ⊥ to the projected magnetic field in Vela and other pulsars where X-ray imaging reveals the orientation. This shows that the PMs usually lie ∥ to the rotation axes on the sky. Two key physical consequences then follow: first, to the extent that supernova “kicks” are responsible for pulsar PMs, they are mostly ∥ to the rotation axis; and, second, most pulsar radiation is heavily processed by the magnetospheric plasma such that the lowest altitude “parent” core emission is polarized ⊥ to the emitting field, propagating as the extraordinary (X) mode.

  4. The Double Pulsar System J0737-3039

    NASA Astrophysics Data System (ADS)

    Lorimer, D. R.

    The double pulsar system J0737 - 3039 - a 22.7 ms pulsar in a compact 2.4 hr orbit about a 2.7 s pulsar was one of the long-awaited "holy grails" of pulsar astronomy. After only two years of timing, the system is close to surpassing the original Hulse-Taylor binary as a test of general relativity. On-going timing should soon reveal second-order effects in the post-Newtonian parameters. In addition, the observed interactions of the radio beams of the two pulsars provide a unique laboratory for probing neutron star magnetospheres and relativistic winds. Finally, a revised estimate of the cosmic rate of double neutron star mergers including J0737 - 3039 boosts previous estimates by an order of magnitude and suggests a high detection rate for the advanced LIGO gravitational wave detector.

  5. Pulsars, supernovae, and ultrahigh energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Kotera, K.; Fang, K.; Olinto, A. V.; Phinney, E. S.

    2012-12-01

    The acceleration of ultrahigh energy nuclei in fast spinning newborn pulsars can explain the observed spectrum of ultrahigh energy cosmic rays and the trend towards heavier nuclei for energies above 10^{19} eV as indicated by air shower studies reported by the Auger Observatory. By assuming a normal distribution of pulsar birth periods centered at 300 ms, we show that the contribution of extragalactic pulsar births to the ultrahigh energy cosmic ray spectrum naturally gives rise to a contribution to very high energy cosmic rays (VHECRs, between 10^{16} and 10^{18} eV) by Galactic pulsar births. The required injected composition to fit the observed spectrum depends on the absolute energy scale, differing considerably between the energy scale used by Auger and that used by the Telescope Array. Depending on the composition of the cosmic rays that escape the supernova remnant and the diffusion behavior of VHECRs in the Galaxy, the contribution of Galactic pulsar births can also bridge the gap between predictions for cosmic ray acceleration in supernova remnants and the observed spectrum below the ankle. Fast spinning newborn pulsars that could produce UHECRs would be born in supernovae that could present interesting specific radiative features, due to the interaction of the pulsar wind with the surrounding ejecta. The resulting supernova lightcurves could present a high luminosity plateau over a few years, and a bright X-ray and gamma-ray peak around one or two years after the onset of the explosion. If such signatures were observed, they could have important implications both for UHECR astrophysics and for the understanding of core-collapse supernovae.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Probing Microstructure in Interstellar Plasma with Pulsars

    NASA Astrophysics Data System (ADS)

    Backer, Donald

    1999-11-01

    Pulsars provide excellent probes of small structure in the interstellar plasma. The list of observable effects includes dispersion, Faraday rotation, diffraction and refraction. Of great interest recently has been episodes of lensing and dual path propagation when the plasma perturbation has just the right focal length for the pulsar-perturber-earth geometry at a given frequency. I will discuss a recent study of the variable dispersion, refraction and diffraction of the millisecond pulsar B1937+21. This is based mainly on daily observations at 327 and 610 MHz with a pulsar monitoring telescope in Green Bank, WV. Further observations at 820 and 1395 MHz allow us to investigate the limits on dispersion measure determination set by diffraction. Length scales in the medium from 10^10 to 10^15 cm are probed. A second study focuses on a rare event in the Crab pulsar where the dispersion measure jumped by 0.1 pc cm-3 within one week and, prior to the jump, a faint and delayed ghost of the pulsed emission was observed. These phenomena can be explained in terms of a plasma wedge crossing the line of sight. The most likely location of this wedge is in the Rayleigh-Taylor unstable interface between the expanding supernova remains and the pre-supernova stellar wind debris.

  13. 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.

  14. Rotation powered pulsars in the x-rays

    NASA Astrophysics Data System (ADS)

    Arumugasamy, Prakash

    non-recycled X-ray pulsars, PSR J0108-3430 tauc = 166 Myr and E = 5.8 x 1030 erg s -1. The pulsar's spectrum likely consists of a thermal component, emitted from a hot polar cap, and a non-thermal component, emitted from its magnetosphere. The X-ray pulse profile shows a single, asymmetric peak which could be explained by an axially-asymmetric temperature distribution at the pole or by the non-thermal emission from the outer gap. The three pulsars represent important stages in the evolutionary path that a hypothetical single young pulsar like J2022+3842 might take, as it passes through stages close to gamma-ray emission turn-off (like J1836+5925) and X-ray turn-off (similar to J0108-3430). Pulsars in binaries can follow an alternative path. By accreting matter from their companions they can be 'recycled' to short millisecond periods and emit X-rays and gamma-rays for billions of years. I also present a special class of such recycled pulsars which are believed to be in the process of fatally ablating their companions. I present the X-ray analysis of PSR J1446-4701, an E = 3.6 x 1034 erg s-1 pulsar in a 6.7 hr binary orbit, and PSR J1311-3430, an E = 4.9 x 1034 erg s-1 pulsar in an extreme 1.6 hr binary orbit. PSR J1446-4701 turned out to be a non-eclipser with possibly low (face-on) orbital inclination, with emission from both the pulsar and the intra-binary shock observable throughout the binary orbit. PSR J1311-3430 is a known eclipser, in which hints of spectral variability have been found, between pulsar superior and inferior conjunction phases. I also present a comprehensive comparison of the sample of such extremely low-mass binary pulsars. We reveal the true nature of pulsars, slowly and steadily, usually one target at a time, but eventually we expect useful patterns to emerge that improves our understanding of the population of rotation powered pulsars.

  15. Modulated gamma-ray emission from compact millisecond pulsar binary systems

    NASA Astrophysics Data System (ADS)

    Bednarek, W.

    2014-01-01

    Context. A significant number of the millisecond pulsars (MSPs) have been discovered within binary systems. Tens of these MSPs emit γ-rays that are modulated with the pulsar period since this emission is produced in the inner pulsar magnetosphere. In several such binary systems, the masses of the companion stars have been derived allowing two classes of objects to be distinguished, which are called the black widow and the redback binaries. Pulsars in these binary systems are expected to produce winds that create conditions for acceleration of electrons, when colliding with stellar winds. These electrons should interact with the anisotropic radiation from the companion stars producing γ-ray emission modulated with the orbital period of the binary system, similar to what is observed in the massive TeV γ-ray binary systems. Aims: We consider the interaction of a MSP wind with a very inhomogeneous stellar wind from the companion star within binary systems of the black widow and redback types. Our aim is to determine the features of γ-ray emission produced in the collision region of the winds from a few typical MSP binary systems. Methods: It is expected that the pulsar wind should mix efficiently with the inhomogeneous stellar wind. The mixed winds move outside the binary with relatively low velocity. Electrons accelerated in such mixed, turbulent winds can interact with the magnetic field and strong radiation from the companion star, producing not only synchrotron radiation but also γ-rays in the inverse Compton process, fluxes of which are expected to be modulated on the periods of the binary systems. Applying numerical methods, we calculated the GeV-TeV gamma-ray spectra and the light curves expected from some MSP binary systems. Results: Gamma-ray emission, produced within the binary systems, is compared with the sensitivities of the present and future gamma-ray telescopes. It is concluded that energetic MSP binary systems create a new class of TeV

  16. 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.

  17. Arecibo Pulsar Highlights

    NASA Astrophysics Data System (ADS)

    Seymour, Andrew

    2016-01-01

    Here we present some of the recent interesting pulsar research that has been conducted from the Arecibo Observatory (AO). Many of these results are only possible because of the unique capabilities of AO's 305 meter telescope. Along with this, we state several possible improvements to AO's capabilities that would aid pulsar studies in the immediate future.

  18. 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.

  19. 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?

  20. 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

  1. 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.

  2. The second FERMI large area telescope catalog of gamma-ray pulsars

    SciTech Connect

    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.

    2013-09-19

    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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Physical processes in eclipsing pulsars: Eclipse mechanisms and diagnostics

    NASA Technical Reports Server (NTRS)

    Thompson, C.; Blandford, R. D.; Evans, Charles R.; Phinney, E. S.

    1994-01-01

    We investigate how the radio emission of a pulsar interacts with plasma derived from a stellar companion. Various physical mechanisms that can cause radio pulse eclipse are discussed, and predictions are made for the polarization properties of the emergent radio wave. We consider eclipses by a wind from the stellar companion, by a stellar magnetosphere, or by material entrained in the pulsar wind. Eclipses due to refraction require either a relatively high plasma density or a sharp edge to the plasma distribution. The conditions that must prevail for free-free absorption to be effective in eclipsing a radio beam are also outlined. Pulse smearing may be important at higher frequencies; related eclipse mechanisms include pulse spreading due to a rapidly changing electron column, and scattering by Langmuir turbulence. The high brightness temperature radio beam can generate its own plasma turbulence via a number of nonlinear parametric instabilities, such as the instability associated with stimulated Raman scattering. When the plasma turbulence is heavily damped, the radio bean can still undergo induced Compton scattering. Stimulated scattering effects such as these are very sensitive to the presence of narrow-band substructure in the pulsar radio emission. Finally, we consider the possibility that plasma derived from a stellar companion may mix with the relativistic pulsar wind and cause cyclotron absorption at low radio frequencies. Even if the cyclotron optical depth is small, fluctuations in the emergent polarization of the radio beam on the timescale of a few seconds are a very sensitive probe of the spatial structure of the magnetic field in the pulsar wind. The current observational properties of two known eclipsing pulsar systems, PSR 1957+20 and PSR 1744-24A, are used to construct tentative eclipse models. The favored model for PSR 1957+20 is cyclotron or synchrotron absorption by plasma embedded in the pulsar wind combined with pulse smearing at high

  11. Pulsars and Extreme Physics

    NASA Astrophysics Data System (ADS)

    Bell-Burnell, Jocelyn

    2004-10-01

    Pulsars were discovered 35 years ago. What do we know about them now, and what have they taught us about the extremes of physics? With an average density comparable to that of the nucleus, magnetic fields around 108 T and speeds close to c these objects have stretched our understanding of the behaviour of matter. They serve as extrememly accurate clocks with which to carry out precision experiments in relativity. Created in cataclysmic explosions, pulsars are a (stellar) form of life after death. After half a billion revolutions most pulsars finally die, but amazingly some are born again to yet another, even weirder, afterlife. Pulsar research continues lively, delivering exciting, startling and almost unbelievable results!

  12. 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...

  13. 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

  14. 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).

  15. 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.

  16. Known Pulsars Identified in the GMRT 150 MHz All-sky Survey

    NASA Astrophysics Data System (ADS)

    Frail, D. A.; Jagannathan, P.; Mooley, K. P.; Intema, H. T.

    2016-10-01

    We have used the 150 MHz radio continuum survey (TGSS ADR) from the Giant Metrewave Radio Telescope (GMRT) to search for phase-averaged emission toward all well-localized radio pulsars north of -53° decl. We detect emission toward 200 pulsars with high confidence (≥slant 5σ ) and another 88 pulsars at fainter levels. We show that most of our identifications are likely from pulsars, except for a small number where the measured flux density is confused by an associated supernova or pulsar-wind nebula, or a globular cluster. We investigate the radio properties of the 150 MHz sample and find an unusually high number of gamma-ray binary millisecond pulsars with very steep spectral indices. We also note a discrepancy in the measured flux densities between GMRT and LOFAR pulsar samples, suggesting that the flux density scale for the LOFAR pulsar sample may be in error by approximately a factor of two. We carry out a separate search of 30 well-localized gamma-ray, radio-quiet pulsars in an effort to detect a widening of the radio beam into the line of sight at lower frequencies. No steep-spectrum emission was detected either toward individual pulsars or in a weighted stack of all 30 images.

  17. 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.

  18. 1974: the discovery of the first binary pulsar

    NASA Astrophysics Data System (ADS)

    Damour, Thibault

    2015-06-01

    The 1974 discovery, by Russell A Hulse and Joseph H Taylor, of the first binary pulsar, PSR B1913+16, opened up new possibilities for the study of relativistic gravity. PSR B1913+16, as well as several other binary pulsars, provided direct observational proof that gravity propagates at the velocity of light and has a quadrupolar structure. Binary pulsars also provided accurate tests of the strong-field regime of relativistic gravity. General relativity has passed all of the binary pulsar tests with flying colors. The discovery of binary pulsars also had very important consequences for astrophysics, leading to accurate measurement of neutron star masses, improved understanding of the possible evolution scenarios for the co-evolution of binary stars, and proof of the existence of binary neutron stars emitting gravitational waves for hundreds of millions of years, before coalescing in catastrophic events radiating intense gravitational wave signals, and probably also leading to important emissions of electromagnetic radiation and neutrinos. This article reviews the history of the discovery of the first binary pulsar, and describes both its immediate impact and its longer-term effect on theoretical and experimental studies of relativistic gravity.

  19. Single-pulse study of radio pulsars

    NASA Astrophysics Data System (ADS)

    Bilous, Anna V.

    Single pulses provide valuable information about the pulsar magnetosphere, giving more spatial and time resolution than the integrated pulse profiles. Clearly, there are several different types of single pulse emission, however it is still unknown what is the nature or even strict definition of each type. This work aims to shed some light on different kinds of single pulses, making an attempt to constrain some emission theories and trace the possible connection between different types. The thesis consists of following case studies: 1. No apparent correlation was found between giant pulses (GPs) from the Crab pulsar (9 GHz, Green Bank Telescope) and its gamma-ray photons (100 MeV - 5 GeV, Fermi). This result suggests that GPs, at least the ones detected at high radio frequencies, are due to changes in coherence of radio emission rather than an overall increase in the magnetospheric particle density. Also, no apparent correlation was found between Crab GPs (1.5 GHz, Green Bank Telescope) and X-ray photons (1.5 - 4.5 keV, Chandra). 2. We show that single pulses from the millisecond pulsar B182-24A fall into two distinct categories — broad faint pulses, coincident with the peaks of integrated pulse profile and bright narrow GPs on the trailing edges of profile components. Owing to our large fractional bandwidth we were able to prove the hypothesis that the spectra of these GPs consist of separate substantially polarized patches. 3. We present a LOFAR study of single pulses from pulsars B0809+74 and B1133+16 below 90 MHz. We show that the spectral width of bright, low-frequency pulses scales with increasing frequency as Δ f/f ˜ 0.15, at least in the case of PSR B0809+74. This behaviour is consistent with predictions of strong plasma turbulence model. 4. Millisecond pulsar B1744-24A belongs to "windy" binary systems, with unbound material escaping from the companion star and interacting with the pulsar's magnetosphere. B1744-24A appears to emit strong wide single

  20. On some electrodynamic properties of binary pulsars

    NASA Astrophysics Data System (ADS)

    Sironi, Lorenzo

    2006-07-01

    respect to the electromagnetic ones and the Lorentz force per unit volume is assumed to be zero outside the pulsar; after showing the main unsolved problems about this model, I will try to examine the origin of the leptons (positrons and electrons) which are expected to fill the pulsar magnetosphere and to continuously stream away from the star through the light cylinder (where co-rotation with the pulsar would mean traveling at the speed of light). Since even the magnetosphere of a single isolated pulsar is not well understood, my approach in considering some hitherto unexplored properties of the joint magnetosphere of a binary pulsar will mainly be qualitative, trying to understand through order-of-magnitude estimates the physical processes involved. First of all I will describe the possibility that, for binary pulsars in which the orbital separation is less than the sum of the light cylinder radii of the stars, the region at the center of the system could show a time-dependent distortion of the two co-rotating magnetospheres which could give origin to an induced electric field. I will then examine the possibility that such a field is quenched by a local production of pairs caused by the electric field itself. After showing that the electric field can not be switched-off by the pairs, I will discuss the possible observational consequences of the production of such a large number of leptons, which will be accelerated by the electric field along the magnetic field lines toward the pulsars and will then radiate their energy via curvature radiation; unfortunately, the small energy flux emitted, together with the rarity of double neutron star systems, will not likely allow us to detect the radiation emitted. Lastly, I will discuss the original idea that the strong induced electric fields could be responsible for the acceleration of cosmic rays whose energy lies between the knee and the ankle of the cosmic ray spectrum. In this case the unsolved problem is the origin for

  1. 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.

  2. 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.

  3. Pulsar Astrophysics at Very High Energies in the Fermi-HAWC Era

    NASA Astrophysics Data System (ADS)

    Saz Parkinson, Pablo; Belfiore, A.; HAWC Collaboration; Fermi LAT Collaboration

    2013-04-01

    Pulsar astrophysics has received a major boost in recent years with the tremendous progress achieved in the gamma-ray regime. In the 0.1-100 GeV energy range, where pulsars emit a large fraction of their energy, the Fermi Large Area Telescope (LAT) is providing an abundance of high-quality data, greatly improving our understanding of the pulsar mechanism. In addition to detecting over 120 pulsars, the improved statistics from the LAT have enabled studies of some of the brightest pulsars with exquisite detail, up to unprecedented energies (in some cases above 25 GeV), finally bridging the gap with ground-based instruments. At very high energies (VHE, > 100 GeV), recent detections by VERITAS and MAGIC of pulsations from the Crab pose a serious challenge to pulsar models. It is unclear whether the Crab is unique in this respect, or whether VHE emission is common in other pulsars. Some models predict that such emission should smoothly connect with the standard GeV emission seen by the LAT, while others point instead to a different spectral (e.g. inverse Compton) component altogether. If present in other pulsars, such a component might be found at higher energies (> 1 TeV), but its flux is highly uncertain. Further VHE observations of pulsars are crucial to distinguish between (and constrain) the competing scenarios. The High Altitude Water Cherenkov Observatory (HAWC), currently under construction in Mexico, is well-suited to perform observations of pulsars above 100 GeV. The HAWC detector has a wide field of view, high duty cycle, and excellent sensitivity 15 times better than its predecessor Milagro), and its contemporaneous operation with Fermi should enable it to carry out the first comprehensive survey of northern-hemisphere gamma-ray pulsars above 100 GeV. I will discuss the motivations, goals, timeline, and sensitivity of HAWC searches for VHE emission from pulsars.

  4. 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

  5. X-Ray States of Redback Millisecond Pulsars

    NASA Astrophysics Data System (ADS)

    Linares, M.

    2014-11-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L X), between (6-9) × 1032 erg s-1 (disk-passive state) and (3-5) × 1033 erg s-1 (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L X in the pulsar state (>1032 erg s-1).

  6. ON THE POLAR CAP CASCADE PAIR MULTIPLICITY OF YOUNG PULSARS

    SciTech Connect

    Timokhin, A. N.; Harding, A. K.

    2015-09-10

    We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ∼few × 10{sup 5}. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae.

  7. Looking for light pseudoscalar bosons in the binary pulsar system J0737-3039.

    PubMed

    Dupays, Arnaud; Rizzo, Carlo; Roncadelli, Marco; Bignami, Giovanni F

    2005-11-18

    We present numerical calculations of the photon-light-pseudoscalar-boson (LPB) production in the recently discovered binary pulsar system J0737-3039. Light pseudoscalar bosons oscillate into photons in the presence of strong magnetic fields. In the context of this binary pulsar system, this phenomenon attenuates the light beam emitted by one of the pulsars, when the light ray goes through the magnetosphere of the companion pulsar. We show that such an effect is observable in the gamma-ray band since the binary pulsar is seen almost edge-on, depending on the values of the LPB mass and on the strength of its two-photon coupling. Our results are surprising in that they show a very sharp and significant (up to 50%) transition probability in the gamma-ray (> tens of MeV) domain. The observations can be performed by the upcoming NASA GLAST mission.

  8. A burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Kashiyama, Kazumi; Mészáros, Peter

    2016-09-01

    Tenuous wind bubbles, which are formed by the spin-down activity of central compact remnants, are relevant in some models of fast radio bursts (FRBs) and superluminous supernovae (SNe). We study their high-energy signatures, focusing on the role of pair-enriched bubbles produced by young magnetars, rapidly rotating neutron stars, and magnetized white dwarfs. (i) First, we study the nebular properties and the conditions allowing for escape of high-energy gamma-rays and radio waves, showing that their escape is possible for nebulae with ages of ≳10-100 yr. In the rapidly rotating neutron star scenario, we find that radio emission from the quasi-steady nebula itself may be bright enough to be detected especially at sub-mm frequencies, which is relevant as a possible counterpart of pulsar-driven SNe and FRBs. (ii) Secondly, we consider the fate of bursting emission in the nebulae. We suggest that an impulsive burst may lead to a highly relativistic flow, which would interact with the nebula. If the shocked nebula is still relativistic, pre-existing non-thermal particles in the nebula can be significantly boosted by the forward shock, leading to short-duration (maybe millisecond or longer) high-energy gamma-ray flashes. Possible dissipation at the reverse shock may also lead to gamma-ray emission. (iii) After such flares, interactions with the baryonic ejecta may lead to afterglow emission with a duration of days to weeks. In the magnetar scenario, this burst-in-bubble model leads to the expectation that nearby (≲10-100 Mpc) high-energy gamma-ray flashes may be detected by the High-Altitude Water Cherenkov Observatory and the Cherenkov Telescope Array, and the subsequent afterglow emission may be seen by radio telescopes such as the Very Large Array. (iv) Finally, we discuss several implications specific to FRBs, including constraints on the emission regions and limits on soft gamma-ray counterparts.

  9. Modelling pulsar glitches

    NASA Astrophysics Data System (ADS)

    Haskell, Brynmor

    2016-07-01

    Pulsar glitches, i.e. sudden jumps in the spin frequency of pulsars, are thought to be due to the presence of large scale superfluid components in neutron star interiors, and offer a unique insight into the physics of matter at high densities and low temperatures. Nevertheless, more than forty years after the first observation, many open questions still exist on the nature of pulsar glitches. In this talk I will review our current theoretical understanding of glitches, of their trigger mechanisms and of the hydrodynamics of superfluid neutron stars. In particular I will focus on 'superfluid vortex avalanches' and recent advances in applying this paradigm to glitch observations, and I will discuss hydrodynamical modelling of the post-glitch recovery.

  10. Pulsar Bursts Coming From Beachball-Sized Structures

    NASA Astrophysics Data System (ADS)

    2003-03-01

    In a major breakthrough for understanding what one of them calls "the most exotic environment in the Universe," a team of astronomers has discovered that powerful radio bursts in pulsars are generated by structures as small as a beach ball. VLA Image of Crab Nebula VLA Image of Crab Nebula (Click on Image for Larger Version) Pulsar Diagram Diagram of a Pulsar (Click on Image for Larger Version) "These are by far the smallest objects ever detected outside our solar system," said Tim Hankins, leader of the research team, which studied the pulsar at the center of the Crab Nebula, more than 6,000 light-years from Earth. "The small size of these regions is inconsistent with all but one proposed theory for how the radio emission is generated," he added. The other members of the team are Jeff Kern, James Weatherall and Jean Eilek. Hankins was a visiting scientist at Arecibo Observatory in Puerto Rico at the time the pulsar observations were made. He and Eilek are professors at the New Mexico Institute of Mining and Technology (New Mexico Tech) in Socorro, NM. Kern is a graduate student at NM Tech and a predoctoral fellow at the National Radio Astronomy Observatory (NRAO) in Socorro. Weatherall is an adjunct professor at NM Tech, currently working at the Federal Aviation Administration. The astronomers reported their discovery in the March 13 edition of the scientific journal Nature. Pulsars are superdense neutron stars, the remnants of massive stars that exploded as supernovae. Pulsars emit powerful beams of radio waves and light. As the neutron star spins, the beam sweeps through space like the beam of a lighthouse. When such a beam sweeps across the Earth, astronomers see a pulse from the pulsar. The Crab pulsar spins some 33 times every second. British radio astronomers discovered pulsars in 1967, one receiving the Nobel Prize for the discovery. In the years since, the method by which pulsars produce their powerful beams of electromagnetic radiation has remained a

  11. Youngest Radio Pulsar Revealed with Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    2002-04-01

    Astronomers using the National Science Foundation's (NSF) newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have detected remarkably faint radio signals from an 820 year-old pulsar, making it the youngest radio-emitting pulsar known. This discovery pushes the boundaries of radio telescope sensitivity for discovering pulsars, and will enable scientists to conduct observations that could lead to a better understanding of how these stars evolve. The Robert C. Byrd Green Bank Telescope Robert C. Byrd Green Bank Telescope "Important questions about pulsars may be answered by long-term monitoring of objects such as the one we just detected," said Fernando Camilo of Columbia University in New York City. "Young pulsars are particularly rare, and being able to study such a young one at radio wavelengths provides an outstanding opportunity to learn critical facts about their evolution and workings." The results of this research, based on observations conducted on February 22-23, 2002, were accepted for publication in the Astrophysical Journal Letters. Scientists have long suspected that a pulsar - a rapidly spinning, superdense neutron star - was born when a giant star ended its life in a cataclysmic supernova explosion observed in late summer of 1181, as suggested by Japanese and Chinese historical records. For the past 20 years, astronomers have searched this supernova remnant (3C58), located 10,000 light-years away in the constellation Cassiopeia, for the telltale pulsations of a newly born pulsar. Late in 2001, data from NASA's Chandra X-ray satellite confirmed its existence, but it remained an elusive quarry for radio telescopes. "We believed from historical records and certainly knew from recent X-ray observations that this star was there," Camilo remarked, "but despite many attempts, no one had been able to find any radio pulsations from it because the signals are, it turns out, incredibly weak." For comparison, this pulsar's radio emission is some 250

  12. The surprising Crab pulsar and its nebula: a review.

    PubMed

    Bühler, R; Blandford, R

    2014-06-01

    The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae. PMID:24913306

  13. Rotating Radio Transients and Their Place Among Pulsars

    NASA Technical Reports Server (NTRS)

    Burke-Spolaor, S.

    2012-01-01

    Six years ago, the discovery of Rotating Radio Transients (RRATs) marked what appeared to be a new type of sparsely-emitting pulsar. Since 2006, more than 70 of these objects have been discovered in single-pulse searches of archival and new surveys. With a continual inflow of new information about the RRAT population in the form of new discoveries, multi-frequency follow ups, coherent timing solutions, and pulse rate statistics, a view is beginning to form of the place in the pulsar population RRATs hold. Here we review the properties of neutron stars discovered through single pulse searches. We first seek to clarify the definition of the term RRAT, emphasising that "the RRAT population" encompasses several phenomenologies. A large subset of RRATs appears to represent the tail of an extended distribution of pulsar nulling fractions and activity cycles; these objects present several key open questions remaining in this field.

  14. The surprising Crab pulsar and its nebula: a review.

    PubMed

    Bühler, R; Blandford, R

    2014-06-01

    The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae.

  15. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

    Deller, A. T.; Vigeland, S. J.; Kaplan, D. L.; Goss, W. M.; Brisken, W. F.; Chatterjee, S.; Cordes, J. M.; Janssen, G. H.; Lazio, T. J. W.; Petrov, L.; Stappers, B. W.; Lyne, A.

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145–0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M˜ 0.85 {M}ȯ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145–0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  16. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

    Deller, A. T.; Vigeland, S. J.; Kaplan, D. L.; Goss, W. M.; Brisken, W. F.; Chatterjee, S.; Cordes, J. M.; Janssen, G. H.; Lazio, T. J. W.; Petrov, L.; Stappers, B. W.; Lyne, A.

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145-0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M˜ 0.85 {M}⊙ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145-0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  17. The nature of pulsar radio emission

    NASA Astrophysics Data System (ADS)

    Dyks, J.; Rudak, B.; Demorest, P.

    2010-01-01

    High-quality averaged radio profiles of some pulsars exhibit double, highly symmetric features both in emission and in absorption. It is shown that both types of feature are produced by a split fan beam of extraordinary-mode curvature radiation that is emitted/absorbed by radially extended streams of magnetospheric plasma. With no emissivity in the plane of the stream, such a beam produces bifurcated emission components (BFCs) when our line of sight passes through the plane. An example of a double component created in this way is present in the averaged profile of the 5-ms pulsar J1012+5307. We show that the component can indeed be very well fitted by the textbook formula for the non-coherent beam of curvature radiation in the polarization state that is orthogonal to the plane of electron trajectory. The observed width of the BFC decreases with increasing frequency at a rate that confirms the curvature origin. Likewise, the double absorption features (double notches) are produced by the same beam of the extraordinary-mode curvature radiation, when it is eclipsed by thin plasma streams. The intrinsic property of curvature radiation to create bifurcated fan beams explains the double features in terms of a very natural geometry and implies the curvature origin of pulsar radio emission. Similarly, the `double conal' profiles of class D result from a cut through a wider stream with finite extent in magnetic azimuth. Therefore, their width reacts very slowly to changes of viewing geometry resulting from geodetic precession. The stream-cut interpretation implies a highly non-orthodox origin of both the famous S-swing of polarization angle and the low-frequency pulse broadening in D profiles. The azimuthal structure of polarization modes in the curvature radiation beam provides an explanation for the polarized `multiple imaging' and the edge depolarization of pulsar profiles.

  18. What the timing of millisecond pulsars can teach us about their interior.

    PubMed

    Alford, Mark G; Schwenzer, Kai

    2014-12-19

    The cores of compact stars reach the highest densities in nature and therefore could consist of novel phases of matter. We demonstrate via a detailed analysis of pulsar evolution that precise pulsar timing data can constrain the star's composition, through unstable global oscillations (r modes) whose damping is determined by microscopic properties of the interior. If not efficiently damped, these modes emit gravitational waves that quickly spin down a millisecond pulsar. As a first application of this general method, we find that ungapped interacting quark matter is consistent with both the observed radio and x-ray data, whereas for ordinary nuclear matter some additional enhanced damping mechanism is required. PMID:25554870

  19. Pulsars and Acceleration Sites

    NASA Technical Reports Server (NTRS)

    Harding, Alice

    2008-01-01

    Rotation-powered pulsars are excellent laboratories for the studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. But even forty years after their discovery, we still do not understand their pulsed emission at any wavelength. I will review both the basic physics of pulsars as well as the latest developments in understanding their high-energy emission. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. Fortunately the Gamma-Ray Large Area Space Telescope (GLAST), with launch in May 2008 will detect many new gamma-ray pulsars and test the predictions of these models with unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 300 GeV.

  20. The Pulsar Search Collaboratory

    ERIC Educational Resources Information Center

    Rosen, R.; Heatherly, S.; McLaughlin, M. A.; Kondratiev, V. I.; Boyles, J. R.; Wilson, M.; Lorimer, D. R.; Lynch, R.; Ransom, S.

    2010-01-01

    The Pulsar Search Collaboratory (PSC) (NSF #0737641) is a joint project between the National Radio Astronomy Observatory and West Virginia University designed to interest high school students in science, technology, engineering, and mathematics related career paths by helping them to conduct authentic scientific research. The 3 year PSC program,…

  1. Searches for Pulsars at the Center of the Galaxy

    NASA Astrophysics Data System (ADS)

    Majid, Walid

    2015-08-01

    Pulsars are highly magnetized, rapidly rotating neutron stars that emit a beam of electromagnetic radiation that could be detected at Earth, if the emission beam is pointing toward the Earth, analogous to the way a lighthouse can be seen when the light is pointed in the direction of the observer. Pulsars within the central parsec of our Galaxy is expected to make excellent probes of not only the environment of the supermassive black hole at the center of the galaxy, but also in the case of pulsar/black hole binary systems expected in this region, of their own rich environment dominated by relativistic gravity effects. In this presentation I will give an overview of why it is important to search for pulsars in the center of the galaxy, and a summary of previous and ongoing efforts to survey this region with radio telescopes. I will describe the difficulties encountered with current surveys and prospects for detection of perhaps hundreds of pulsars in this region with new generations of radio telescopes now under construction.

  2. The Spectrum of LMC Pulsar B0540-69; Carryover

    NASA Astrophysics Data System (ADS)

    Bless, Robert

    1994-01-01

    PSR B0540-69, a 50 ms pulsar located in the Large Magellanic Cloud, is the most distant pulsar known. B0540-69 is one of the few pulsars for which a second time derivative of rotational frequency has been measured. High Speed Photometer observations in a UV + visible passband (1600 - 7000 angstroms) showed a pulse profile identical to that in the X-ray region, with the same pulsed fraction (van Citters et al 1994). The rotational frequency observed by HSP, when compared with previous measurements, gave a value of 2.28 (0.02) for the braking index. B0540-69 is similar to the Crab pulsar in its rotational perior and associated synchrotron-emitting nebula (a "plerion"), but its pulse profile and braking index are strikingly different. We propose her to obtain an objective prism spectrum of B0540-69 to compare its spectral energy distribution in the UV and blue with that of the Crab pulsar and to determine the fractional part of our UV plus visible pulse profile due to UV photons. Our objective prism spectrum with the FOS Blue detector will measure the relative energy distribution between ~1850 and ~5000 angstroms.

  3. Student Discovers New Pulsar

    NASA Astrophysics Data System (ADS)

    2010-01-01

    A West Virginia high-school student has discovered a new pulsar, using data from the giant Robert C. Byrd Green Bank Telescope (GBT). Shay Bloxton, 15, a participant in a project in which students analyze data from the radio telescope, spotted evidence of the pulsar on October 15. Bloxton, along with NRAO astronomers observed the object again one month later. The new observation confirmed that the object is a pulsar, a rotating, superdense neutron star. Bloxton is a sophomore at Nicholas County High School in Summersville, West Virginia. "I was very excited when I found out I had actually made a discovery," Bloxton said. She went to Green Bank in November to participate in the follow-up observation. She termed that visit "a great experience." "It also helped me learn a lot about how observations with the GBT are actually done," she added. The project in which she participated, called the Pulsar Search Collaboratory (PSC), is a joint project of the National Radio Astronomy Observatory (NRAO) and West Virginia University, funded by a grant from the National Science Foundation. Pulsars are known for their lighthouse-like beams of radio waves that sweep through space as the neutron star rotates, creating a pulse as the beam sweeps by the Earth. First discovered in 1967, pulsars serve as valuable natural "laboratories" for physicists studying exotic states of matter, quantum mechanics and General Relativity. The GBT, dedicated in 2000, has become one of the world's leading tools for discovering and studying pulsars. The PSC, led by NRAO Education Officer Sue Ann Heatherly and Project Director Rachel Rosen, includes training for teachers and student leaders, and provides parcels of data from the GBT to student teams. The project involves teachers and students in helping astronomers analyze data from 1500 hours of observing with the GBT. The 120 terabytes of data were produced by 70,000 individual pointings of the giant, 17-million-pound telescope. Some 300 hours of the

  4. The Rotating Spiral Structure of the Vela Pulsar Jet

    NASA Astrophysics Data System (ADS)

    Kargaltsev, Oleg; Durant, M.; Pavlov, G. G.; Bykov, A. M.; Kropotina, J.; Levenfish, K.

    2013-01-01

    Eleven 40-ks Chandra ACIS observations of the Vela pulsar wind nebula were taken between July 2009 and September 2010. Our analysis of the images of the variable Vela pulsar jet have revealed a remarkable periodic pattern. The observed variations are consistent with those of expected for a steadily rotating helical jet projected on the sky. Such behavior can be a manifestation of neutron star precession, possibly amplified by MHD instabilities. This work is supported by NASA through CXO grant G09-0084B and by the Ministry of Education and Science of the Russian Federation (Contract No. 11.G34.31.0001).

  5. Exoplanets around pulsars

    NASA Astrophysics Data System (ADS)

    Kitiashvili, I.; Gusev, A.

    2003-04-01

    Surprise discovery of thrid planets and cometary body (!?) near the pulsar PSR~B1257+12 (Wolszczan and Frail, 1992) posed the problems of describing their moving around pulsar, their origin and early rotation. At the present time the question whether there exist another three pulsars in the planetary systems is under discussion: PSR 0329+54 (1 planet), PSR B1620--26 (1 planet) and PSR 1828--11 (3 planets, Stairs et al., 2000) . It is known the time scale of pulsars is very stable, then in some cases the periodical fluctuation in time of arrival may be provoked motion of planetary bodies, free precession or concerned with the interior of the neutron star. Discovery exoplanets around PSR~B1257+12 gave strong push for search and investigate planets around neutron stars. Dust disks around stars still retain information about the formation processes of the exoplanetary systems as they are formed by collisions of planetesimals or protoplanets.The conventional explanation for the formation gas giant planets, core accretion, presumes that a gaseous envelope collapses upon a roughly 10 M⊕, solid core that was formed by the collisional accumulation of planetary embryos orbiting in a gaseous disk (Boss, 2002). Small protoplanets torque the disk at the Lindblad and corotation resonances, and the resulting back-torque can propel a planet into the star (Ward, 1997). We investigate the equations of the magneto-rotational instability of the Keplerian disk in linear approximation by qualitative and bifurcation methods. The separation of 3-dimensional parameter space of dynamical system by bifurcation surfaces is obtained. The obtained gallery of more ten phase portraits of disk evolution illustrates the various regimes of the planetary systems evolution. Investigation of a matter around young pulsars will allow us to answer about a possibility of birth of planets after explosion of a supernova star.

  6. ON PLASMA ROTATION AND DRIFTING SUBPULSES IN PULSARS: USING ALIGNED PULSAR B0826-34 AS A VOLTMETER

    SciTech Connect

    Van Leeuwen, J.; Timokhin, A. N. E-mail: andrey.timokhin@nasa.gov

    2012-06-20

    We derive the exact drift velocity of plasma in the pulsar polar cap, in contrast to the order-of-magnitude expressions presented by Ruderman and Sutherland and generally used throughout the literature. We emphasize that the drift velocity depends not on the absolute value, as is generally used, but on the variation of the accelerating potential across the polar cap. If we assume that drifting subpulses in pulsars are indeed due to this plasma drift, several observed subpulse-drift phenomena that are incompatible with the Ruderman and Sutherland family of models can now be explained: we show that variations of drift rate, outright drift reversals, and the connection between drift rates and mode changes have natural explanations within the frame of the 'standard' pulsar model, when derived exactly. We apply this model for drifting subpulses to the case of PSR B0826-34, an aligned pulsar with two separate subpulse-drift regions emitted at two different colatitudes. Careful measurement of the changing and reversing drift rate in each band independently sets limits on the variation of the accelerating potential drop. The derived variation is small, {approx}10{sup -3} times the vacuum potential drop voltage. We discuss the implications of this result for pulsar modeling.

  7. The Optimization of GBT Pulsar Data for the GBNCC Pulsar Survey

    NASA Astrophysics Data System (ADS)

    Gordon, Ashlee Nicole; Green Bank NRAO, GBNCC

    2016-01-01

    The Green Bank Telescope collects data from the Green Bank Northern Celestial Cap (GBNCC) pulsar survey in order to find new pulsars within its sensitivity and also, to confirm previously found pulsars within its sensitivity range. The collected data is then loaded into the CyberSKA website database where astronomers are tasked with rating the data sets based on its potential to be a pulsar from 0(unclassified), 1(class 1 pulsar), 2(class 2 pulsar), 3(class 3 pulsar), 4(radio frequency interference), 5(not a pulsar), 6(know pulsar), 7(harmonic of a known pulsar). This specific research done was to use previously classified pulsars to create a python script that will automatically identify the data set as a pulsar or a non-pulsar. After finding the recurring frequencies of radio frequency interference (RFI), the frequencies were then added to a pipeline to further discern pulsars from RFI.

  8. INTEGRAL and XMM-Newton Observations of the X-Ray Pulsar IGR J16320-4751/AX J1691.9-4752

    NASA Technical Reports Server (NTRS)

    Rodriquez, J.; Bodaghee, A.; Kaaret, P.; Tomsick, J. A.; Kuulkers, E.; Malaguti, G.; Petrucci, P.-O.; Cabanac, C.; Chernyakova, M.; Corbel, S.; Deluit, S.; DiCocco, G.; Ebisawa, K.; Goldwurm, A.; Henri, G.; Lebrun, F.; Paizis, A.; Walter, R.; Foschini, L.

    2006-01-01

    We report on observations of the X-ray pulsar IGR J16320-4751 (also known as AX J1631.9-4752) performed simultaneously with International Gamma-Ray Astrophysics Laboratory (INTEGRAL) and XMM-Newton. We refine the source position and identify the most likely infrared counterpart. Our simultaneous coverage allows us to confirm the presence of X-ray pulsations at approximately 1300 s, that we detect above 20 keV with INTEGRAL for the first time. The pulse fraction is consistent with being constant with energy, which is compatible with a model of polar accretion by a pulsar. We study the spectral properties of IGR J16320-4751 during two major periods occurring during the simultaneous coverage with both satellites, namely a flare and a non-flare period. We detect the presence of a narrow 6.4 keV iron line in both periods. The presence of such a feature is typical of supergiant wind accretors such as Vela X-1 or GX 301-2. We inspect the spectral variations with respect to the pulse phase during the non-flare period, and show that the pulse is solely due to variations of the X-ray flux emitted by the source and not due to variations of the spectral parameters. Our results are therefore compatible with the source being a pulsar in a High Mass X-ray Binary. We detect a soft excess appearing in the spectra as a blackbody with a temperature of approximately 0.07 keV. We discuss the origin of the X-ray emission in IGR J16320-4751: while the hard X-rays are likely the result of Compton emission produced in the close vicinity of the pulsar, based on energy argument we suggest that the soft excess is likely the emission by a collisionally energized cloud in which the compact object is embedded.

  9. Chandra Imaging of the X-Ray Nebula Powered by Pulsar B1509-58

    NASA Technical Reports Server (NTRS)

    Gaensler, B. M.; Arons, J.; Kaspi, V. M.; Pivovaroff, M. J.; Kawai, N.; Tamura, K.

    2002-01-01

    We present observations with the Chandra X-Ray Observatory of the pulsar wind nebula (PWN) powered by the energetic young pulsar B1509-58. These data confirm the complicated morphology of the system indicated by previous observations, and in addition reveal several new components to the nebula. The overall PWN shows a clear symmetry axis oriented at a position angle 150" +- 5" (north through east), which we argue corresponds to the pulsar spin axis. We show that a previously identified radio feature matches well with the overall extent of the X-ray PWN, and propose the former as the long-sought radio nebula powered by the pulsar. We further identify a bright collimated feature, at least 4' long, lying along the nebula's main symmetry axis; we interpret this feature as a physical outflow from the pulsar, and infer a velocity for this jet of greater than 0.2c. The lack of any observed counterjet implies that the pulsar spin axis is inclined at -30" to the line of sight, contrary to previous estimates made from lower resolution data. We also identify a variety of compact features close to the pulsar. A pair of semicircular X-ray arcs lie 17" and 30" to the north of the pulsar; the latter arc shows a highly polarized radio counterpart. We show that these features can be interpreted as ion compression wisps in a particle-dominated equatorial flow, and use their properties to infer a ratio of electromagnetic to particle energy in pairs at the wind shock 0.005, similar to that seen in the Crab Nebula. We further identify several compact knots seen very close to the pulsar; we use these to infer cr < 0.003 at a separation from the pulsar of 0.1 pc.

  10. a Surprise from the Pulsar in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    1995-11-01

    New observations of the spectrum of the rapidly spinning neutron star (the `pulsar') in the Crab Nebula have been carried out with the ESO 3.5-metre New Technology Telescope (NTT) by a group of Italian astronomers [1]. Because of greatly improved spectral resolution which allows to register even very fine details in the pulsar's spectrum, they are able to determine for the first time with high accuracy the overall dependance of the emission on wavelength, i.e. the `shape' of the spectrum. Quite unexpectedly, they also detect a hitherto unknown 100 A (10 nm) broad `absorption dip', which can be securely attributed to the pulsar. These results open an exciting new window for the study of the extreme physical processes close to a pulsar. The Nature of Pulsars It is estimated that there may be as many as 100 million neutron stars in our Galaxy. A neutron star is the superdense remnant of the extremely violent supernova explosion that occurs at the end of the life of a comparatively massive star. In fact, all stars that are more than about 6 times heavier than the Sun are believed to end their lives as supernovae. During the explosion, the central core of the dying star collapses in a few milliseconds and the matter at the centre is compressed to a density comparable to that of an atomic nucleus. Due to the enormous inward pressure, the atomic particles are squeezed together into a kind of neutron jam. The outcome is the formation of a neutron star with a diameter of 10-15 kilometres, weighing as much as the Sun. In accordance with the physical law that implies that the rotation momentum of the exploding star must be conserved, newborn neutron stars will rotate very rapidly around their axis, in some cases as fast as 100 times per second. In the same way, the new neutron star is expected to possess a strong magnetic field. Of these myriads of neutron stars, about 700 have been observed to emit radio pulses (hence the name `pulsar'). A few of these can also be detected

  11. A New Physical Model for Pulsars as Gravitational Shielding and Oscillating Neutron Stars

    NASA Astrophysics Data System (ADS)

    Zhang, Tianxi

    2014-06-01

    Pulsars are fast rotating neutron stars that synchronously emit periodic Dirac delta shape pulses of radio-frequency radiation and Lorentzian shape oscillations of X-rays. The acceleration of particles near the magnetic poles, which derivate from the rotating axis produces coherent beams of radio emissions that are viewed as pulses of radiation whenever the magnetic poles sweep the viewers. However, the conventional lighthouse model of pulsars is only conceptual. The physical mechanism through which particles are accelerated to produce coherent beams of radio emissions is still poorly understood. The process for periodically oscillating X-rays to emit from hot spots at the inner edge of accretion disks of pulsars is also remained as an unsolved mystery. Recently, a new physical model of pulsars is proposed by the author to quantitatively interpret the emission characteristics of pulsars, in accordance with his well-developed five-dimensional fully covariant Kaluza-Klein gravitational shielding theory and the physics of thermal and accelerating charged particle radiation. The results indicate that with the significant gravitational shielding by scalar field a neutron star nonlinearly oscillates and produces synchronous periodically Dirac delta shape pulse-like radio-frequency radiation (emitted by the oscillating or accelerating charged particles) as well as periodically Lorentzian shape oscillating X-rays (as the thermal radiation of neutron stars that temperature varies due to the oscillation). This physical model of pulsars as gravitational shielding and oscillating neutron stars broadens our understanding of neutron stars and develops an innovative mechanism to disclose the mystery of pulsars. In this presentation, I will show the results obtained from the quantitative studies of this new physical model of pulsars for the oscillations of neutron stars and the powers of radio pulse-like emissions and oscillating X-rays.

  12. Gamma radiation from radio pulsars

    NASA Technical Reports Server (NTRS)

    Ruderman, Malvin

    1990-01-01

    The probable magnetospheric location and source of the gamma ray emission from some young radiopulsars is discussed. The suggested evolution of this emission as a function of pulsar period gives a diminished gamma-ray luminosity for a more rapidly spinning pre-Crab pulsar. A greatly enhanced one, similar to that of unidentified Cos B sources, is predicted for a slightly slower post-Vela pulsar, followed by a relatively rapid quenching of the gamma-ray luminosity at still longer periods. Possible anomalous exo-magnetospheric pulsed MeV and TeV-PeV radiation from the Crab pulsar is considered.

  13. Disentangling X-Ray Emission Processes in Vela-Like Pulsars

    NASA Technical Reports Server (NTRS)

    Gaensler, Bryan; Mushotzky, Richard (Technical Monitor)

    2003-01-01

    We present a deep observation with the X-Ray Multimirror Mission of PSR B1823-13, a young pulsar with similar properties to the Vela pulsar. We detect two components to the X-ray emission associated with PSR B1823-13: an elongated core of extent 30 min immediately surrounding the pulsar embedded in a fainter, diffuse component of emission 5 sec in extent, seen only on the southern side of the pulsar. The pulsar itself is not detected, either as a point source or through its pulsations. Both components of the X-ray emission are well fitted by a power-law spectrum, with photon index Gamma approx. 1.6 and X-ray luminosity (0.5-10 keV) L(sub X) approx. 9 x 10(exp 32) ergs/s for the core and Gamma approx. 2.3 and L(sub X) approx. 3 x 10(exp 33) ergs/s for the diffuse emission, for a distance of 4 kpc. We interpret both components of emission as corresponding to a pulsar wind nebula, which we designate G18.0-0.7. We argue that the core region represents the wind termination shock of this nebula, while the diffuse component indicates the shocked downstream wind. We propose that the asymmetric morphology of the diffuse emission with respect to the pulsar is the result of a reverse shock from an associated supernova remnant, which has compressed and distorted the pulsar-powered nebula. Such an interaction might be typical for pulsars at this stage in their evolution. The associated supernova remnant is not detected directly, most likely being too faint to be seen in existing X-ray and radio observations.

  14. Discovery of the optical counterparts to four energetic Fermi millisecond pulsars

    SciTech Connect

    Breton, R. P.; Van Kerkwijk, M. H.; Roberts, M. S. E.; Hessels, J. W. T.; Camilo, F.; McLaughlin, M. A.; Ransom, S. M.; Ray, P. S.; Stairs, I. H.

    2013-06-01

    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified γ-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modeling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10%-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irradiated pulsar binaries and offers insights about the energetics of the pulsar wind and the production of γ-ray emission. In addition, this provides a simple way of estimating the brightness of irradiated pulsar companions given the pulsar spin-down luminosity. Our analysis also suggests that two of the four new irradiated pulsar companions are only partially filling their Roche lobe. Some of these sources are relatively bright and represent good targets for spectroscopic follow-up. These measurements could enable, among other things, mass determination of the neutron stars in these systems.

  15. Physical conditions in the reconnection layer in pulsar magnetospheres

    SciTech Connect

    Uzdensky, Dmitri A.; Spitkovsky, Anatoly E-mail: anatoly@astro.princeton.edu

    2014-01-01

    The magnetosphere of a rotating pulsar naturally develops a current sheet (CS) beyond the light cylinder (LC). Magnetic reconnection in this CS inevitably dissipates a nontrivial fraction of the pulsar spin-down power within a few LC radii. We develop a basic physical picture of reconnection in this environment and discuss its implications for the observed pulsed gamma-ray emission. We argue that reconnection proceeds in the plasmoid-dominated regime, via a hierarchical chain of multiple secondary islands/flux ropes. The inter-plasmoid reconnection layers are subject to strong synchrotron cooling, leading to significant plasma compression. Using the conditions of pressure balance across these current layers, the balance between the heating by magnetic energy dissipation and synchrotron cooling, and Ampere's law, we obtain simple estimates for key parameters of the layers—temperature, density, and layer thickness. In the comoving frame of the relativistic pulsar wind just outside of the equatorial CS, these basic parameters are uniquely determined by the strength of the reconnecting upstream magnetic field. For the case of the Crab pulsar, we find them to be of order 10 GeV, 10{sup 13} cm{sup –3}, and 10 cm, respectively. After accounting for the bulk Doppler boosting due to the pulsar wind, the synchrotron and inverse-Compton emission from the reconnecting CS can explain the observed pulsed high-energy (GeV) and very high energy (∼100 GeV) radiation, respectively. Also, we suggest that the rapid relative motions of the secondary plasmoids in the hierarchical chain may contribute to the production of the pulsar radio emission.

  16. On the nature and evolution of the windy binary pulsar PSR 1744 - 24A

    NASA Astrophysics Data System (ADS)

    Shaham, Jacob; Tavani, Marco

    1991-08-01

    It is suggested that the companion of the pulsar PSR 1744 - 24A is an approximately 0.1 solar mass main-sequence star that slightly underfills its Roche lobe and is sending off a cool wind due to excitation by radiation from the pulsar. Unlike in the similarly excited system of pulsar PSR 1957 + 20, pulsar radiation pressure here almost balances wind pressure at the companion distance, leading to vastly fluctuating eclipse patterns and to occasional attempted accretion episodes that are aborted by the propeller effect and result in X-ray bursts. If this picture is correct, multiwavelength continuous observations of PSR 1744 - 24A will give valuable information about the accretion process onto neutron stars rotating with millisecond periods.

  17. The Extended Pulsar Magnetosphere

    NASA Technical Reports Server (NTRS)

    Constantinos, Kalapotharakos; Demosthenes, Kazanas; Ioannis, Contopoulos

    2012-01-01

    We present the structure of the 3D ideal MHD pulsar magnetosphere to a radius ten times that of the light cylinder, a distance about an order of magnitude larger than any previous such numerical treatment. Its overall structure exhibits a stable, smooth, well-defined undulating current sheet which approaches the kinematic split monopole solution of Bogovalov 1999 only after a careful introduction of diffusivity even in the highest resolution simulations. It also exhibits an intriguing spiral region at the crossing of two zero charge surfaces on the current sheet, which shows a destabilizing behavior more prominent in higher resolution simulations. We discuss the possibility that this region is physically (and not numerically) unstable. Finally, we present the spiral pulsar antenna radiation pattern.

  18. PSR J0737-3039B: A PROBE OF RADIO PULSAR EMISSION HEIGHTS

    SciTech Connect

    Perera, B. B. P.; McLaughlin, M. A.; Lomiashvili, D.; Gourgouliatos, K. N.; Lyutikov, M.

    2012-05-10

    In the double pulsar system PSR J0737-3039A/B, the strong wind produced by pulsar A distorts the magnetosphere of pulsar B. The influence of these distortions on the orbital-dependent emission properties of pulsar B can be used to determine the location of the coherent radio emission generation region in the pulsar magnetosphere. Using a model of the wind-distorted magnetosphere of pulsar B and the well-defined geometrical parameters of the system, we determine the minimum emission height to be {approx}20R{sub NS} in the two bright orbital longitude regions. We can determine the maximum emission height by accounting for the amount of deflection of the polar field line with respect to the magnetic axis using the analytical magnetic reconnection model of Dungey and the semi-empirical numerical model of Tsyganenko. Both of these models estimate the maximum emission height to be {approx}2500R{sub NS}. The minimum and maximum emission heights we calculate are consistent with those estimated for normal isolated pulsars.

  19. a Surprise from the Pulsar in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    1995-11-01

    New observations of the spectrum of the rapidly spinning neutron star (the `pulsar') in the Crab Nebula have been carried out with the ESO 3.5-metre New Technology Telescope (NTT) by a group of Italian astronomers [1]. Because of greatly improved spectral resolution which allows to register even very fine details in the pulsar's spectrum, they are able to determine for the first time with high accuracy the overall dependance of the emission on wavelength, i.e. the `shape' of the spectrum. Quite unexpectedly, they also detect a hitherto unknown 100 A (10 nm) broad `absorption dip', which can be securely attributed to the pulsar. These results open an exciting new window for the study of the extreme physical processes close to a pulsar. The Nature of Pulsars It is estimated that there may be as many as 100 million neutron stars in our Galaxy. A neutron star is the superdense remnant of the extremely violent supernova explosion that occurs at the end of the life of a comparatively massive star. In fact, all stars that are more than about 6 times heavier than the Sun are believed to end their lives as supernovae. During the explosion, the central core of the dying star collapses in a few milliseconds and the matter at the centre is compressed to a density comparable to that of an atomic nucleus. Due to the enormous inward pressure, the atomic particles are squeezed together into a kind of neutron jam. The outcome is the formation of a neutron star with a diameter of 10-15 kilometres, weighing as much as the Sun. In accordance with the physical law that implies that the rotation momentum of the exploding star must be conserved, newborn neutron stars will rotate very rapidly around their axis, in some cases as fast as 100 times per second. In the same way, the new neutron star is expected to possess a strong magnetic field. Of these myriads of neutron stars, about 700 have been observed to emit radio pulses (hence the name `pulsar'). A few of these can also be detected

  20. Pulsar extinction. [astrophysics

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Baker, K.; Turk, J. S.

    1975-01-01

    Radio emission from pulsars, attributed to an instability associated with the creation of electron-positron pairs from gamma rays was investigated. The condition for pair creation therefore lead to an extinction condition. The relevant physical processes were analyzed in the context of a mathematical model, according to which radiation originated at the polar caps and magnetic field lines changed from a closed configuration to an open configuration at the force balance or corotation radius.

  1. The pulsar spectral index distribution

    NASA Astrophysics Data System (ADS)

    Bates, S. D.; Lorimer, D. R.; Verbiest, J. P. W.

    2013-05-01

    The flux-density spectra of radio pulsars are known to be steep and, to first order, described by a power-law relationship of the form Sν ∝ να, where Sν is the flux density at some frequency ν and α is the spectral index. Although measurements of α have been made over the years for several hundred pulsars, a study of the intrinsic distribution of pulsar spectra has not been carried out. From the result of pulsar surveys carried out at three different radio frequencies, we use population synthesis techniques and a likelihood analysis to deduce what underlying spectral index distribution is required to replicate the results of these surveys. We find that in general the results of the surveys can be modelled by a Gaussian distribution of spectral indices with a mean of -1.4 and unit standard deviation. We also consider the impact of the so-called gigahertz-peaked spectrum pulsars proposed by Kijak et al. The fraction of peaked-spectrum sources in the population with any significant turnover at low frequencies appears to be at most 10 per cent. We demonstrate that high-frequency (>2 GHz) surveys preferentially select flatter spectrum pulsars and the converse is true for lower frequency (<1 GHz) surveys. This implies that any correlations between α and other pulsar parameters (for example age or magnetic field) need to carefully account for selection biases in pulsar surveys. We also expect that many known pulsars which have been detected at high frequencies will have shallow, or positive, spectral indices. The majority of pulsars do not have recorded flux density measurements over a wide frequency range, making it impossible to constrain their spectral shapes. We also suggest that such measurements would allow an improved description of any populations of pulsars with `non-standard' spectra. Further refinements to this picture will soon be possible from the results of surveys with the Green Bank Telescope and LOFAR.

  2. Deep optical imaging of the γ-ray pulsar J1048-5832 with the VLT

    NASA Astrophysics Data System (ADS)

    Danilenko, A.; Kirichenko, A.; Sollerman, J.; Shibanov, Yu.; Zyuzin, D.

    2013-04-01

    Context. PSR J1048-5832 is a young radio-pulsar that has recently been detected in γ-rays with Fermi, and also in X-rays with Chandra and XMM-Newton. It powers a compact pulsar wind nebula visible in X-rays and is in many ways similar to the Vela pulsar. Aims: We present deep optical observations made with the ESO Very Large Telescope to search for optical counterparts of the pulsar and its nebula and to explore their multi-wavelength emission properties. Methods: The data were obtained in the V and R bands and were compared with archival data in other spectral domains. Results: We do not detect the pulsar in the optical and derive informative upper limits of R ≳ 28.m1 and V ≳ 28.m4 for its brightness. Using a red-clump star method, we estimate an interstellar extinction towards the pulsar of AV ≈ 2 mag, which is consistent with the absorbing column density derived from X-rays. The respective distance agrees with the dispersion measure distance. We reanalysed the Chandra X-ray data and compared the dereddened upper limits with the unabsorbed X-ray spectrum of the pulsar. We find that regarding its optical-X-ray spectral properties this γ-ray pulsar is not distinct from other pulsars detected in both ranges. However, like the Vela pulsar, it is very inefficient in the optical and X-rays. Among a dozen optical sources overlapping with the pulsar X-ray nebula we find one with V ≈ 26.m9 and R ≈ 26.m3, whose colour is slightly bluer than that of the field stars and is consistent with the peculiar colours typical for pulsar nebula features. It positionally coincides with a relatively bright feature of the pulsar X-ray nebula, resembling the Crab wisp and is located in ~2 from the pulsar. We suggest this source as a counterpart candidate to the feature. Conclusions: Based on the substantial interstellar extinction towards the pulsar and its optical inefficiency, additional optical studies should be carried out at longer wavelengths. Based on observations made

  3. X-ray observations of black widow pulsars

    SciTech Connect

    Gentile, P. A.; McLaughlin, M. A.; Roberts, M. S. E.; Camilo, F.; Hessels, J. W. T.; Kerr, M.; Ransom, S. M.; Ray, P. S.; Stairs, I. H.

    2014-03-10

    We describe the first X-ray observations of five short orbital period (P{sub B} < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs). Four of these—PSRs J0023+0923, J1124–3653, J1810+1744, and J2256–1024—are 'black-widow' pulsars, with degenerate companions of mass <<0.1 M {sub ☉}, three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing 'redback' with a near Roche-lobe filling ∼0.2 solar mass non-degenerate companion. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256–1024, show significant orbital variability while PSR J1124–3653 shows marginal orbital variability. The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission. This is similar to what has been detected in the low-mass X-ray binary to MSP transition object PSR J1023+0038.

  4. Unusual Braking Indices in Young X-ray Pulsars

    NASA Astrophysics Data System (ADS)

    Frederic Archibald, Robert; Kaspi, Victoria M.; Beardmore, Andrew P.; Gehrels, Neil; Kennea, Jamie; Gotthelf, Eric V.; Ferdman, Robert; Guillot, Sebastien; Harrison, Fiona; Keane, Evan; Pivovaroff, Michael; Stern, Daniel; Tendulkar, Shriharsh P.; Tomsick, John

    2016-04-01

    Pulsars spin down over time. By measuring braking indices of pulsars, effectively the change in the spin-down rate over time, we can probe the underlying driving engine of the spin-down. For a magnetic dipole in a vacuum, n is predicted to be 3. To date, all measured braking indices are less than 3, which can be explained, e.g. by particle winds, changes in the magnetic field. In all models of braking indices, n should be nearly constant on year time-scales. Here, I will discuss two recent observation results that challenge this model, interestingly both coming from young X-ray pulsars with no detected radio emission. The first, a long-lived decrease in the braking index of PSR J1846-0258 following a burst of magnetar-like activity, and secondly, the first stationary braking index greater than three. Understanding neutron-star spin evolution is key to constraining these objects' long-term energy output and has relevance to topics ranging from pulsar wind nebulae and supernova remnants to core-collapse supernova rates, physics, and expected outcomes.

  5. Searching for Planets Around Pulsars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    Did you know that the very first exoplanets ever confirmed were found around a pulsar? The precise timing measurements of pulsar PSR 1257+12 were what made the discovery of its planetary companions possible. Yet surprisingly, though weve discovered thousands of exoplanets since then, only one other planet has ever been confirmed around a pulsar. Now, a team of CSIRO Astronomy and Space Science researchers are trying to figure out why.Formation ChallengesThe lack of detected pulsar planets may simply reflect the fact that getting a pulsar-planet system is challenging! There are three main pathways:The planet formed before the host star became a pulsar which means it somehow survived its star going supernova (yikes!).The planet formed elsewhere and was captured by the pulsar.The planet formed out of the debris of the supernova explosion.The first two options, if even possible, are likely to be rare occurrences but the third option shows some promise. In this scenario, after the supernova explosion, a small fraction of the material falls back toward the stellar remnant and is recaptured, forming what is known as a supernova fallback disk. According to this model, planets could potentially form out of this disk.Disk ImplicationsLed by Matthew Kerr, the CSIRO astronomers set out to systematically look for these potential planets that might have formed in situ around pulsars. They searched a sample of 151 young, energetic pulsars, scouring seven years of pulse time-of-arrival data for periodic variation that could signal the presence of planetary companions. Their methods to mitigate pulsar timing noise and model realistic orbits allowed them to have good sensitivity to low-mass planets.The results? They found no conclusive evidence that any of these pulsars have planets.This outcome carries with it some significant implications. The pulsar sample spans 2 Myr in age, in which planets should have had enough time to form in debris disks. The fact that none were detected

  6. A Multiwavelength Study on the High-energy Behavior of the Fermi/LAT Pulsars

    NASA Astrophysics Data System (ADS)

    Marelli, Martino; De Luca, Andrea; Caraveo, Patrizia A.

    2011-06-01

    Using archival as well as freshly acquired data, we assess the X-ray behavior of the Fermi/Large Area Telescope γ-ray pulsars listed in the First Fermi source catalog. After revisiting the relationships between the pulsars' rotational energy losses and their X-ray and γ-ray luminosities, we focus on the distance-independent γ-to-X-ray flux ratios. When plotting our F γ/F X values as a function of the pulsars' rotational energy losses, one immediately sees that pulsars with similar energetics have F γ/F X spanning three decades. Such spread, most probably stemming from vastly different geometrical configurations of the X-ray and γ-ray emitting regions, defies any straightforward interpretation of the plot. Indeed, while energetic pulsars do have low F γ/F X values, little can be said for the bulk of the Fermi neutron stars. Dividing our pulsar sample into radio-loud and radio-quiet subsamples, we find that, on average, radio-quiet pulsars do have higher values of F γ/F X , implying an intrinsic faintness of their X-ray emission and/or a different geometrical configuration. Moreover, despite the large spread mentioned above, statistical tests show a lower scatter in the radio-quiet data set with respect to the radio-loud one, pointing to a somewhat more constrained geometry for the radio-quiet objects with respect to the radio-loud ones.

  7. Discovery of an Unidentified Fermi Object as a Black Widow-Like Millisecond Pulsar

    NASA Technical Reports Server (NTRS)

    Kong, A. K. H.; Huang, R. H. H.; Cheng, K. S.; Takata, J.; Yatsu, Y.; Cheung, C. C.; Donato, D.; Lin, L. C. C.; Kataoka, J.; Takahashi, Y.; Maeda, K.; Hui, C. Y.; Tam, P. H. T.

    2012-01-01

    The Fermi Gamma-ray Space Telescope has revolutionized our knowledge of the gamma-ray pulsar population, leading to the discovery of almost 100 gamma-ray pulsars and dozens of gamma-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and gamma-ray pulsars, until now all of the known gamma-ray MSPs have been visible in the radio. Here we report the discovery of a radio-quiet" gamma-ray emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and gamma-ray properties of the source are consistent with known gamma-ray pulsars. We also found a 4.63-hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a approx. 0.1 Stellar Mass late-type companion star. Based on the profile of the optical and X-ray light-curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intra-binary shock. No radio detection of the source has been reported yet and although no gamma-ray/radio pulsation has been found, we estimated that the spin period of the MSP is approx. 3-5 ms based on the inferred gamma-ray luminosity.

  8. DISCOVERY OF AN UNIDENTIFIED FERMI OBJECT AS A BLACK WIDOW-LIKE MILLISECOND PULSAR

    SciTech Connect

    Kong, A. K. H.; Huang, R. H. H.; Tam, P. H. T.; Cheng, K. S.; Takata, J.; Yatsu, Y.; Cheung, C. C.; Donato, D.; Kataoka, J.; Takahashi, Y.; Maeda, K.; Hui, C. Y.

    2012-03-15

    The Fermi {gamma}-ray Space Telescope has revolutionized our knowledge of the {gamma}-ray pulsar population, leading to the discovery of almost 100 {gamma}-ray pulsars and dozens of {gamma}-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and {gamma}-ray pulsars, until now all of the known {gamma}-ray MSPs have been visible in the radio. Here we report the discovery of a 'radio-quiet' {gamma}-ray-emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and {gamma}-ray properties of the source are consistent with known {gamma}-ray pulsars. We also found a 4.63 hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a {approx}0.1 M{sub Sun} late-type companion star. Based on the profile of the optical and X-ray light curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intrabinary shock. No radio detection of the source has been reported yet, and although no {gamma}-ray/radio pulsation has been found we estimate that the spin period of the MSP is {approx}3-5 ms based on the inferred {gamma}-ray luminosity.

  9. Newly Commissioned Green Bank Telescope Bags New Pulsars

    NASA Astrophysics Data System (ADS)

    2002-01-01

    Astronomers using the National Science Foundation's newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have discovered a windfall of three previously undetected millisecond pulsars in a dense cluster of stars in the Milky Way Galaxy. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope "This globular cluster, known as Messier 62, has been very well studied, and it would have been an exciting discovery to find just one new pulsar. The fact that we were able to detect three new pulsars at one time is simply remarkable," said Bryan Jacoby, a graduate student at the California Institute of Technology who led the research team. Results of the discovery were recently announced in an International Astronomical Union Circular. Jacoby and his colleague Adam Chandler, also a graduate student at Caltech, used the GBT to search for new pulsars in addition to the three already known in this cluster. Their research was part of the GBT's Early Science Program, which allows scientific investigations during the testing and commissioning of the telescope. The researchers used the Berkeley-Caltech Pulsar Machine, a new instrument whose development was overseen by Donald Backer at the University of California at Berkeley, to process the signals from the GBT and record them for later analysis. After their data were analyzed, the researchers discovered the telltale signatures of three additional pulsars and their white dwarf companion stars. Pulsars are rapidly rotating neutron stars that emit intense beams of radio waves along their misaligned magnetic axes. When these beams intersect the Earth, we see the pulsar flash on and off. Due to their exquisitely steady rotation, pulsars allow astronomers to study the basic laws of physics and the ways in which these dense clusters and exotic stellar systems are formed. Astronomers study globular clusters because they are among the oldest building blocks of our Galaxy. With their very dense stellar populations, these

  10. Pulsar timing and general relativity

    NASA Technical Reports Server (NTRS)

    Backer, D. C.; Hellings, R. W.

    1986-01-01

    Techniques are described for accounting for relativistic effects in the analysis of pulsar signals. Design features of instrumentation used to achieve millisecond accuracy in the signal measurements are discussed. The accuracy of the data permits modeling the pulsar physical characteristics from the natural glitches in the emissions. Relativistic corrections are defined for adjusting for differences between the pulsar motion in its spacetime coordinate system relative to the terrestrial coordinate system, the earth's motion, and the gravitational potentials of solar system bodies. Modifications of the model to allow for a binary pulsar system are outlined, including treatment of the system as a point mass. Finally, a quadrupole model is presented for gravitational radiation and techniques are defined for using pulsars in the search for gravitational waves.

  11. Magnetars and white dwarf pulsars

    NASA Astrophysics Data System (ADS)

    Lobato, Ronaldo V.; Malheiro, Manuel; Coelho, Jaziel G.

    2016-07-01

    The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely B ≳ 1014G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields B ˜ (1012-1013)G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field B ˜ 107-1010 G and rotate very fast with frequencies Ω ˜ 1rad/s, consistent with the observed rotation periods P ˜ (2-12)s.

  12. Axion mass limits from pulsar x rays

    SciTech Connect

    Morris, D.E.

    1984-12-01

    Axions thermally emitted by a neutron star would be converted into x rays in the strong magnetic field surrounding the star. An improvement in the observational upper limit of pulsed x rays from the Vela pulsar (PSR 0833-45) by a factor of 12 would constrain the axion mass M/sub a/ < 2 x 10/sup -3/eV if the core is non-superfluid and at temperature T/sub c/ greater than or equal to 2 x 10/sup 8/K. If the core is superfluid throughout, an improvement factor of 240 would be needed to provide the same constraint on the axion mass, while in the absence of superfluidity, an improvement factor of 200 could constrain M/sub a/ < 6 x 10/sup -4/eV. A search for modulated hard x rays from PSR 1509-58 or other young pulsars at presently attainable sensitivities may enable the setting of an upper limit for the axion mass. Observation of hard x rays from a very young hot pulsar with T/sub c/ greater than or equal to 7 x 10/sup 8/K could set a firm bound on the axion mass, since neutron superfluidity is not expected above this temperature. The remaining axion mass range 6 x 10/sup -4/eV > M/sub a/ > 10/sup -5/eV (the cosmological lower bound) can be covered by an improved Sikivie type laboratory cavity detector for relic axions constituting the galactic halo. 48 refs.

  13. Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

    PubMed

    Hermsen, W; Hessels, J W T; Kuiper, L; van Leeuwen, J; Mitra, D; de Plaa, J; Rankin, J M; Stappers, B W; Wright, G A E; Basu, R; Alexov, A; Coenen, T; Grießmeier, J-M; Hassall, T E; Karastergiou, A; Keane, E; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Noutsos, A; Serylak, M; Pilia, M; Sobey, C; Weltevrede, P; Zagkouris, K; Asgekar, A; Avruch, I M; Batejat, F; Bell, M E; Bell, M R; Bentum, M J; Bernardi, G; Best, P; Bîrzan, L; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Ciardi, B; Duscha, S; Eislöffel, J; Falcke, H; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; de Gasperin, F; de Geus, E; Gunst, A W; Heald, G; Hoeft, M; Horneffer, A; Iacobelli, M; Kuper, G; Maat, P; Macario, G; Markoff, S; McKean, J P; Mevius, M; Miller-Jones, J C A; Morganti, R; Munk, H; Orrú, E; Paas, H; Pandey-Pommier, M; Pandey, V N; Pizzo, R; Polatidis, A G; Rawlings, S; Reich, W; Röttgering, H; Scaife, A M M; Schoenmakers, A; Shulevski, A; Sluman, J; Steinmetz, M; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Vermeulen, R; van de Brink, R H; van Weeren, R J; Wijers, R A M J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P

    2013-01-25

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories. PMID:23349288

  14. Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

    Hermsen, W.; Hessels, J. W. T.; Kuiper, L.; van Leeuwen, J.; Mitra, D.; de Plaa, J.; Rankin, J. M.; Stappers, B. W.; Wright, G. A. E.; Basu, R.; Alexov, A.; Coenen, T.; Grießmeier, J.-M.; Hassall, T. E.; Karastergiou, A.; Keane, E.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Noutsos, A.; Serylak, M.; Pilia, M.; Sobey, C.; Weltevrede, P.; Zagkouris, K.; Asgekar, A.; Avruch, I. M.; Batejat, F.; Bell, M. E.; Bell, M. R.; Bentum, M. J.; Bernardi, G.; Best, P.; Bîrzan, L.; Bonafede, A.; Breitling, F.; Broderick, J.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Duscha, S.; Eislöffel, J.; Falcke, H.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; de Gasperin, F.; de Geus, E.; Gunst, A. W.; Heald, G.; Hoeft, M.; Horneffer, A.; Iacobelli, M.; Kuper, G.; Maat, P.; Macario, G.; Markoff, S.; McKean, J. P.; Mevius, M.; Miller-Jones, J. C. A.; Morganti, R.; Munk, H.; Orrú, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Rawlings, S.; Reich, W.; Röttgering, H.; Scaife, A. M. M.; Schoenmakers, A.; Shulevski, A.; Sluman, J.; Steinmetz, M.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Vermeulen, R.; van de Brink, R. H.; van Weeren, R. J.; Wijers, R. A. M. J.; Wise, M. W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

    2013-01-01

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

  15. Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

    PubMed

    Hermsen, W; Hessels, J W T; Kuiper, L; van Leeuwen, J; Mitra, D; de Plaa, J; Rankin, J M; Stappers, B W; Wright, G A E; Basu, R; Alexov, A; Coenen, T; Grießmeier, J-M; Hassall, T E; Karastergiou, A; Keane, E; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Noutsos, A; Serylak, M; Pilia, M; Sobey, C; Weltevrede, P; Zagkouris, K; Asgekar, A; Avruch, I M; Batejat, F; Bell, M E; Bell, M R; Bentum, M J; Bernardi, G; Best, P; Bîrzan, L; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Ciardi, B; Duscha, S; Eislöffel, J; Falcke, H; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; de Gasperin, F; de Geus, E; Gunst, A W; Heald, G; Hoeft, M; Horneffer, A; Iacobelli, M; Kuper, G; Maat, P; Macario, G; Markoff, S; McKean, J P; Mevius, M; Miller-Jones, J C A; Morganti, R; Munk, H; Orrú, E; Paas, H; Pandey-Pommier, M; Pandey, V N; Pizzo, R; Polatidis, A G; Rawlings, S; Reich, W; Röttgering, H; Scaife, A M M; Schoenmakers, A; Shulevski, A; Sluman, J; Steinmetz, M; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Vermeulen, R; van de Brink, R H; van Weeren, R J; Wijers, R A M J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P

    2013-01-25

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

  16. Discovery of spin-up in the X-ray pulsar companion of the hot subdwarf HD 49798

    NASA Astrophysics Data System (ADS)

    Mereghetti, Sandro; Pintore, Fabio; Esposito, Paolo; La Palombara, Nicola; Tiengo, Andrea; Israel, Gian Luca; Stella, Luigi

    2016-06-01

    The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28 ± 0.05 M⊙, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton and Swift observations of this source, we could perform a phase-connected timing analysis extending back to the ROSAT data obtained in 1992. We found that the pulsar is spinning up at a rate of (2.15 ± 0.05) × 10-15 s s-1. This result is best interpreted in terms of a neutron star accreting from the wind of its subdwarf companion, although the remarkably steady period derivative over more than 20 yr is unusual in wind-accreting neutron stars. The possibility that the compact object is a massive white dwarf accreting through a disc cannot be excluded, but it requires a larger distance and/or properties of the stellar wind of HD 49798 different from those derived from the modelling of its optical/UV spectra.

  17. Visibility of Pulsar Emission: Motion of the Visible Point

    NASA Astrophysics Data System (ADS)

    Yuen, R.; Melrose, D. B.

    2014-10-01

    A standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara, 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, ψ, defining a trajectory on a sphere of radius r. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al., 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of ψ. The RVM tends to underestimate the range of ψ over which emission is visible. We suggest that the geometry alone strongly favors the visible pulsar radio being emitted at a heights more than ten percent of the light-cylinder distance, where our neglect of retardation effects becomes significant.

  18. Stellar structures and the enigma of pulsars rotation frequency decay

    NASA Astrophysics Data System (ADS)

    de Oliveira, H. O.; Marinho, R. M., Jr.; Maglhaes, N. S.

    2015-07-01

    Pulsars are astrophysical objects normally modelled as compact neutron stars that originated from the collapse of another star. This model, that we name canonical, assumes that pulsars are described by spherical magnetized dipoles that rotate, usually with the magnetic axis misaligned to the rotation axis. This misalignment would be responsible for the observation of radiation emitted in well-defined time intervals in a certain direction (lighthouse effect), the typical observational characteristic of this kind of star. It has been noticed that the rotation frequency of pulsars is slowly decaying with time (spin down), implying a gradual decrease of the rotational angular velocity (Ω). Such decay can be quantified by a dimensionless parameter called “braking index” (“n”), given by n = ΩΩ/(Ω)2, where a dot indicates a time derivative. The canonical model predicts that this index has one only value for all pulsars, equal to three. However, observational data indicate that actual braking indices are less than three, representing an enigma. The main goal of this research is the exploration of a more precise model for pulsars’ rotation frequency decay.

  19. Non-cosmological FRBs from young supernova remnant pulsars

    NASA Astrophysics Data System (ADS)

    Connor, Liam; Sievers, Jonathan; Pen, Ue-Li

    2016-05-01

    We propose a new extra but non-cosmological explanation for fast radio bursts (FRBs) based on very young pulsars in supernova remnants. Within a few hundred years of a core-collapse supernova, the ejecta is confined within ˜1 pc, providing a high enough column density of free electrons for the observed 375-1600 pc cm-3 of dispersion measure (DM). By extrapolating a Crab-like pulsar to its infancy in an environment like that of SN 1987A, we hypothesize such an object could emit supergiant pulses sporadically which would be bright enough to be seen at a few hundred megaparsecs. We hypothesize that such supergiant pulses would preferentially occur early in the pulsar's life when the free electron density is still high, which is why we do not see large numbers of moderate DM FRBs (≲300 pc cm-3). In this scenario, Faraday rotation at the source gives rotation measures (RMs) much larger than the expected cosmological contribution. If the emission were pulsar-like, then the polarization vector could swing over the duration of the burst, which is not expected from non-rotating objects. In this model, the scattering, large DM, and commensurate RM all come from one place which is not the case for the cosmological interpretation. The model also provides testable predictions of the flux distribution and repeat rate of FRBs, and could be furthermore verified by spatial coincidence with optical supernovae of the past several decades and cross-correlation with nearby galaxy maps.

  20. A study of spatial correlations in pulsar timing array data

    NASA Astrophysics Data System (ADS)

    Tiburzi, C.; Hobbs, G.; Kerr, M.; Coles, W. A.; Dai, S.; Manchester, R. N.; Possenti, A.; Shannon, R. M.; You, X. P.

    2016-02-01

    Pulsar timing array experiments search for phenomena that produce angular correlations in the arrival times of signals from millisecond pulsars. The primary goal is to detect an isotropic and stochastic gravitational wave background. We use simulated data to show that this search can be affected by the presence of other spatially correlated noise, such as errors in the reference time standard, errors in the planetary ephemeris, the solar wind and instrumentation issues. All these effects can induce significant false detections of gravitational waves. We test mitigation routines to account for clock errors, ephemeris errors and the solar wind. We demonstrate that it is non-trivial to find an effective mitigation routine for the planetary ephemeris and emphasize that other spatially correlated signals may be present in the data.

  1. X-ray states of redback millisecond pulsars

    SciTech Connect

    Linares, M.

    2014-11-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as 'redbacks', constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L {sub X}), between (6-9) × 10{sup 32} erg s{sup –1} (disk-passive state) and (3-5) × 10{sup 33} erg s{sup –1} (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L {sub X} in the pulsar state (>10{sup 32} erg s{sup –1}).

  2. DEATH LINE OF GAMMA-RAY PULSARS WITH OUTER GAPS

    SciTech Connect

    Wang, Ren-Bo; Hirotani, Kouichi E-mail: hirotani@tiara.sinica.edu.tw

    2011-08-01

    We analytically investigate the condition for a particle accelerator to be active in the outer magnetosphere of a rotation-powered pulsar. Within the accelerator (or the gap), the magnetic-field-aligned electric field accelerates electrons and positrons, which emit copious gamma-rays via the curvature process. If one of the gamma-rays emitted by a single pair materializes as a new pair on average, the gap is self-sustained. However, if the neutron-star spin-down rate decreases below a certain limit, the gap becomes no longer self-sustained and the gamma-ray emission ceases. We explicitly compute the multiplicity of cascading pairs and find that the obtained limit corresponds to a modification of the previously derived outer-gap death line. In addition to this traditional death line, we find another death line, which becomes important for millisecond pulsars, by separately considering the threshold of photon-photon pair production. Combining these traditional and new death lines, we give predictions on the detectability of gamma-ray pulsars with Fermi and AGILE. An implication for X-ray observations of heated polar-cap emission is also discussed.

  3. Synchrotron X-ray emission from old pulsars

    NASA Astrophysics Data System (ADS)

    Kisaka, Shota; Tanaka, Shuta J.

    2014-09-01

    We study the synchrotron radiation as the observed non-thermal emission by the X-ray satellites from old pulsars (≳1-10 Myr) to investigate the particle acceleration in their magnetospheres. We assume that the power-law component of the observed X-ray spectra is caused by the synchrotron radiation from electrons and positrons in the magnetosphere. We consider two pair-production mechanisms of X-ray emitting particles, the magnetic and the photon-photon pair productions. High-energy photons, which ignite the pair production, are emitted via the curvature radiation of the accelerated particles. We use the analytical description for the radiative transfer and estimate the luminosity of the synchrotron radiation. We find that for pulsars with the spin-down luminosity Lsd ≲ 1033 erg s-1, the locations of the particle acceleration and the non-thermal X-ray emission are within ≲107 cm from the centre of the neutron star, where the magnetic pair production occurs. For pulsars with the spin-down luminosity Lsd ≲ 1031 erg s-1 such as J0108-1431, the synchrotron radiation is difficult to explain the observed non-thermal component even if we consider the existence of the strong and small-scale surface magnetic field structures.

  4. Tempo: Pulsar timing data analysis

    NASA Astrophysics Data System (ADS)

    Manchester, R.; Taylor, J.; Peters, W.; Weisberg, J.; Irwin, A.; Wex, N.; Stairs, I.; Demorest, P.; Nice, D.

    2015-09-01

    Tempo analyzes pulsar timing data. Pulse times of arrival (TOAs), pulsar model parameters, and coded instructions are read from one or more input files. The TOAs are fitted by a pulse timing model incorporating transformation to the solar-system barycenter, pulsar rotation and spin-down and, where necessary, one of several binary models. Program output includes parameter values and uncertainties, residual pulse arrival times, chi-squared statistics, and the covariance matrix of the model. In prediction mode, ephemerides of pulse phase behavior (in the form of polynomial expansions) are calculated from input timing models. Tempo is the basis for the Tempo2 (ascl:1210.015) code.

  5. Searching for the optical counterparts of two young γ-ray pulsars

    NASA Astrophysics Data System (ADS)

    Mignani, R. P.; Testa, V.; Marelli, M.; De Luca, A.; Pierbattista, M.; Razzano, M.; Salvetti, D.; Belfiore, A.; Shearer, A.; Moran, P.

    2016-09-01

    We report on the first deep optical observations of two γ-ray pulsars, both among the very first discovered by the Fermi Gamma-ray Space Telescope. The two pulsars are the radio-loud PSR J1907+0602 in the TeV pulsar wind nebula (PWN) MGRO J1908+06 and the radio-quiet PSR J1809-2332 in the "Taz" radio/X-ray PWN. These pulsars are relatively young and energetic and have been both detected in the X-rays by XMM-Newton, which makes them viable targets for optical observations. We observed the pulsar fields in the B and V bands with the Very Large Telescope (VLT) in June/July 2015 to search for their optical counterparts. Neither of the two pulsars has been detected down to 3σ limiting magnitudes of mv ˜ 26.9 and mv ˜ 27.6 for PSR J1907+0602 and PSR J1809-2332, respectively. We discuss these results in the framework of the multi-wavelength emission properties of pulsars.

  6. PSR J1838-0537: DISCOVERY OF A YOUNG, ENERGETIC GAMMA-RAY PULSAR

    SciTech Connect

    Pletsch, H. J.; Allen, B.; Aulbert, C.; Fehrmann, H.; Guillemot, L.; Kramer, M.; Baring, M. G.; Camilo, F.; Caraveo, P. A.; Marelli, M.; Grove, J. E.; Ray, P. S.; Kerr, M.; Ransom, S. M.; Saz Parkinson, P. M. E-mail: guillemo@mpifr-bonn.mpg.de

    2012-08-10

    We report the discovery of PSR J1838-0537, a gamma-ray pulsar found through a blind search of data from the Fermi Large Area Telescope (LAT). The pulsar has a spin frequency of 6.9 Hz and a frequency derivative of -2.2 Multiplication-Sign 10{sup -11} Hz s{sup -1}, implying a young characteristic age of 4970 yr and a large spin-down power of 5.9 Multiplication-Sign 10{sup 36} erg s{sup -1}. Follow-up observations with radio telescopes detected no pulsations; thus PSR J1838-0537 appears radio-quiet as viewed from Earth. In 2009 September the pulsar suffered the largest glitch so far seen in any gamma-ray-only pulsar, causing a relative increase in spin frequency of about 5.5 Multiplication-Sign 10{sup -6}. After the glitch, during a putative recovery period, the timing analysis is complicated by the sparsity of the LAT photon data, the weakness of the pulsations, and the reduction in average exposure from a coincidental, contemporaneous change in LAT's sky-survey observing pattern. The pulsar's sky position is coincident with the spatially extended TeV source HESS J1841-055 detected by the High Energy Stereoscopic System (H.E.S.S.). The inferred energetics suggest that HESS J1841-055 contains a pulsar wind nebula powered by the pulsar.

  7. High Mass X-ray Binary Pulsars

    NASA Astrophysics Data System (ADS)

    Naik, Sachindra

    2016-07-01

    High Mass X-ray Binaries (HMXBs) are interesting objects that provide a wide range of observational probes to the nature of the two stellar components, accretion process, stellar wind and orbital parameters of the systems. Most of the transient HMXBs are found to Be/X-ray binaries (~67%), consisting of a compact object (neutron star) in orbit around the companion Be star. The orbit of the compact object around the Be star is wide and highly eccentric. Be/X-ray binaries are generally quiescent in X-ray emission. The transient X-ray outbursts seen in these objects are known to be due to interaction between the compact object and the circumstellar disk surrounding the Be star. In the recent years, another class of transient HMXBs have been found which have supergiant companions and show shorter X-ray outbursts. X-ray, infrared and optical observations of these HMXBs provide vital information regarding these systems. The timing and broad-band X-ray spectral properties of a few HMXB pulsars, mainly Be/X-ray binary pulsars during regular X-ray outbursts will be discussed.

  8. Fermi's New Pulsar Detection Technique

    NASA Video Gallery

    To locate a pulsar in Fermi LAT data requires knowledge of the object’s sky position, its pulse period, and how the pulse rate slows over time. Computers check many different combinations of posi...

  9. Pulsar electrodynamics: an unsolved problem

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.; Yuen, R.

    2016-04-01

    > Pulsar electrodynamics is reviewed emphasizing the role of the inductive electric field in an oblique rotator and the incomplete screening of its parallel component by charges, leaving `gaps' with \\Vert \

  10. FSSC Science Tools: Pulsar Analysis

    NASA Technical Reports Server (NTRS)

    Thompson, Dave

    2010-01-01

    This slide presentation reviews the typical pulsar analysis, giving tips for screening of the data, the use of time series analysis, and utility tools. Specific information about analyzing Vela data is reviewed.

  11. Catching the rebirth of a radio millisecond pulsar

    NASA Astrophysics Data System (ADS)

    Patruno, Alessandro

    2012-09-01

    On 2013 Dec 10 we have discovered with a Swift/XRT observation, that the low mass X-ray binary (LMXB) XSS J12270-4859 has recently changed state from a quiescent-LMXB into a new anomalous faint state with no signatures of accretion (ATel #5647). An NTT optical observation suggests a transition around December 2012 in the opposite direction to that of the "missing link" PSR J1023+0038 (that switched from a radio millisecond pulsar (MSP), into an LMXB, Stappers et al.2013, Patruno et al. 2013). A MSP may therefore be now active in XSS J12270. We are currently completing the analysis of Parkes data to search for the putative MSP. The Swift/XRT shows a faint source (1e32-1e33 erg/s). We want now to characterize the spectral behaviour with a 30 ks Chandra pointing. If we do not detect radio pulsations Chandra can potentially tell us if the pulsar (and pulsar wind) are on even if the radio pulsar is undetectable (as our preliminary Parkes analysis seems to suggest).

  12. Millisecond radio pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Verbunt, Frank; Lewin, Walter H. G.; Van Paradijs, Jan

    1989-01-01

    It is shown that the number of millisecond radio pulsars, in globular clusters, should be larger than 100, applying the standard scenario that all the pulsars descend from low-mass X-ray binaries. Moreover, most of the pulsars are located in a small number of clusters. The prediction that Teran 5 and Liller 1 contain at least about a dozen millisecond radio pulsars each is made. The observations of millisecond radio pulsars in globular clusters to date, in particular the discovery of two millisecond radio pulsars in 47 Tuc, are in agreement with the standard scenario, in which the neutron star is spun up during the mass transfer phase.

  13. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; van Straten, Willem; Yardley, Daniel Roger Billing; Burke, Sarah; Oslowski, Stefan; Hotan, Aidan; Champion, David

    2010-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband system (APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision, with four pulsars having rms residuals of less than or about 100 ns and 13 less than 1 microsecond. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project.

  14. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Manchester, Dick; Sarkissian, John; Hobbs, George; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; van Straten, Willem; Yardley, Daniel Roger Billing; Champion, David; Burke, Sarah; Oslowski, Stefan; Hotan, Aidan

    2009-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision, with three pulsars having rms residuals of less than or about 100 ns and more than half less than 1 microsecond. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project.

  15. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Manchester, Dick; Sarkissian, John; Hobbs, George; Bailes, Matthew; Bhat, Ramesh; Hotan, Aidan; Jenet, Rick; van Straten, Willem; Yardley, Daniel Roger Billing; Champion, David; You, Xiaopeng; Burke, Sarah

    2009-04-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision, with three pulsars having rms residuals of less than or about 100 ns and more than half less than 1 microsecond. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project.

  16. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Manchester, Dick; Verbiest, Joris P. W.; Sarkissian, John; Hobbs, George; Bailes, Matthew; Bhat, Ramesh; Hotan, Aidan; Jenet, Rick; Burke-Spolaor, Sarah; van Straten, Willem; Yardley, Daniel Roger Billing; You, Xiaopeng

    2008-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB2, PDFB3) and the baseband systems (CPSR2; APSR soon) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we are getting the world's best pulsar timing precision, with four pulsars having rms residuals of less than 200 ns and more than half less than 1 microsecond. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project.

  17. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Manchester, Dick; Sarkissian, John; Hobbs, George; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; van Straten, Willem; Yardley, Daniel Roger Billing; Burke, Sarah; Oslowski, Stefan; Hotan, Aidan; Champion, David

    2010-04-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision, with four pulsars having rms residuals of less than or about 100 ns and 13 less than 1 microsecond. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project.

  18. Pulsar Observatory for Students (POS)

    NASA Astrophysics Data System (ADS)

    Joshi, Bhal Chandra; Manoharan, P. K.; Gopakumar, A.; Mitra, D.; Bagchi, Joydeep; Saikia, D. J.

    2012-07-01

    A new program, to initiate motivated undergraduate students to the methodology of pulsar astronomy in particular and radio astronomy in general, is being launched at the Ooty Radio Telescope (ORT). The ORT is a 530 m X 30 m cylindrical radio telescope operating at 325 MHz, having an equatorial mount. Its equatorial mount allows modestly trained students to make pulsar observations without any substantial help from the observatory. Due to its large collecting area, it is a sensitive instrument for pulsar astronomy, capable of detecting a large number of pulsars with short observation time. The program consists of biannual workshops that will introduce scores of students to basics of radio-astronomy and pulsars. It will also train them in the use of the ORT as well as expose them to the future prospects and excitements in the field. The second leg of the program involves live ORT observations by these trained students during various academic breaks. There is a possibility for a follow up program of highly motivated students, selected from this program, to pursue projects of their interest from the data obtained in these sensitive observations. The long term aim of the program is to enlarge the pulsar astronomy community in the country. The presentation will highlight the main features of this program and describe the experience drawn from such programs.

  19. Pulsars In The Headlines

    NASA Astrophysics Data System (ADS)

    Del Puerto, C.

    1967 was the year of the so-called “war of the six days” or “third Arab Israeli war”, the year of the Che Guevara's death in Bolivia, the year of the military coup in Greece and, in medicine, the year of the first human heart transplant. Moreover, the signing of the international agreement on the use of space with peaceful means and the crash of the Russian shuttle Soyuz-1, with Cosmonaut Vladimir Kamarov on board also happened that year. Likewise, Spanish writer and professor of journalists, José Azorín, passed away. However, here we are interested in 1967 because it was the year of the detection of pulsars, which astronomers initially confused with signals from extraterrestrials or Little Green Men. Nowadays, they are still present in the headlines.

  20. Ion-proton pulsars

    NASA Astrophysics Data System (ADS)

    Jones, P. B.

    2016-07-01

    Evidence derived with minimal assumptions from existing published observations is presented to show that an ion-proton plasma is the source of radio-frequency emission in millisecond and in normal isolated pulsars. There is no primary involvement of electron-positron pairs. This conclusion has also been reached by studies of the plasma composition based on well-established particle-physics processes in neutron stars with positive polar-cap corotational charge density. This work has been published in a series of papers which are also summarized here. It is now confirmed by simple analyses of the observed radio-frequency characteristics, and its implications for the further study of neutron stars are outlined.

  1. Thermal properties of the middle-aged pulsar J1741–2054

    SciTech Connect

    Karpova, A.; Danilenko, A.; Shibanov, Yu.; Shternin, P.; Zyuzin, D.

    2014-07-10

    We present results of the spectral analysis of the X-ray emission from the middle-aged Fermi pulsar J1741–2054 using all Chandra archival data collected in 2010 and 2013. We confirm early findings by Romani et al. in 2010 that the pulsar spectrum contains a thermal emission component. The component is best described by the blackbody model with temperature ≈60 eV and emitting area radius ≈17 D{sub kpc} km. The thermal emission likely originates from the entire surface of the cooling neutron star if the distance to the pulsar is ≈0.8 kpc. The latter is supported by a large absorbing column density inferred from the X-ray fit and empirical optical extinction-distance relations along the pulsar line of sight. The neutron star surface temperature and characteristic age make it similar to the well studied middle-aged pulsar B1055–52. Like this pulsar, PSR J1741–2054 is hotter than predicted by the standard cooling scenario.

  2. Millisecond pulsars - Nature's most stable clocks

    NASA Astrophysics Data System (ADS)

    Taylor, Joseph H., Jr.

    1991-07-01

    The author describes the role pulsars might play in time and frequency technology. Millisecond pulsars are rapidly rotating neutron stars: spherical flywheels some 20 km in diameter, 1.4 times as massive as the Sun, and spinning as fast as several thousand radians per second. Radio noise generated in a pulsar's magnetosphere by a highly beamed process is detectable over interstellar distances, as a periodic sequence of pulses similar to the ticks of an excellent clock. High-precision comparisons between pulsar time and terrestrial atomic time show that over intervals of several years, some millisecond pulsars have fractional stabilities comparable to those of the best atomic clocks. The author briefly reviews the physics of pulsars, discusses the techniques of pulsar timing measurements, and summarizes the results of careful studies of pulsar stabilities.

  3. Fermi Finds Youthful Pulsar Among Ancient Stars

    NASA Video Gallery

    In three years, NASA's Fermi has detected more than 100 gamma-ray pulsars, but something new has appeared. Among a type of pulsar with ages typically numbering a billion years or more, Fermi has fo...

  4. A New Standard Pulsar Magnetosphere

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Kalapotharakos, Constantinos; Kazanas, Demosthenes

    2014-01-01

    In view of recent efforts to probe the physical conditions in the pulsar current sheet, we revisit the standard solution that describes the main elements of the ideal force-free pulsar magnetosphere. The simple physical requirement that the electric current contained in the current layer consists of the local electric charge moving outward at close to the speed of light yields a new solution for the pulsar magnetosphere everywhere that is ideal force-free except in the current layer. The main elements of the new solution are as follows: (1) the pulsar spindown rate of the aligned rotator is 23% larger than that of the orthogonal vacuum rotator; (2) only 60% of the magnetic flux that crosses the light cylinder opens up to infinity; (3) the electric current closes along the other 40%, which gradually converges to the equator; (4) this transfers 40% of the total pulsar spindown energy flux in the equatorial current sheet, which is then dissipated in the acceleration of particles and in high-energy electromagnetic radiation; and (5) there is no separatrix current layer. Our solution is a minimum free-parameter solution in that the equatorial current layer is electrostatically supported against collapse and thus does not require a thermal particle population. In this respect, it is one more step toward the development of a new standard solution. We discuss the implications for intermittent pulsars and long-duration gamma-ray bursts. We conclude that the physical conditions in the equatorial current layer determine the global structure of the pulsar magnetosphere.

  5. TOWARD A REALISTIC PULSAR MAGNETOSPHERE

    SciTech Connect

    Kalapotharakos, Constantinos; Kazanas, Demosthenes; Harding, Alice

    2012-04-10

    We present the magnetic and electric field structures and the currents and charge densities of pulsar magnetospheres that do not obey the ideal condition, E {center_dot} B = 0. Since the acceleration of particles and the production of radiation require the presence of an electric field component parallel to the magnetic field, E{sub ||}, the structure of non-ideal pulsar magnetospheres is intimately related to the production of pulsar radiation. Therefore, knowledge of the structure of non-ideal pulsar magnetospheres is important because their comparison (including models for the production of radiation) with observations will delineate the physics and the parameters underlying the pulsar radiation problem. We implement a variety of prescriptions that support non-zero values for E{sub ||} and explore their effects on the structure of the resulting magnetospheres. We produce families of solutions that span the entire range between the vacuum and the (ideal) force-free electrodynamic solutions. We also compute the amount of dissipation as a fraction of the Poynting flux for pulsars of different angles between the rotation and magnetic axes and conclude that this is at most 20%-40% (depending on the non-ideal prescription) in the aligned rotator and 10% in the perpendicular one. We present also the limiting solutions with the property J = {rho}c and discuss their possible implication on the determination of the 'on/off' states of the intermittent pulsars. Finally, we find that solutions with values of J greater than those needed to null E{sub ||} locally produce oscillations, potentially observable in the data.

  6. A new standard pulsar magnetosphere

    SciTech Connect

    Contopoulos, Ioannis; Kalapotharakos, Constantinos; Kazanas, Demosthenes

    2014-01-20

    In view of recent efforts to probe the physical conditions in the pulsar current sheet, we revisit the standard solution that describes the main elements of the ideal force-free pulsar magnetosphere. The simple physical requirement that the electric current contained in the current layer consists of the local electric charge moving outward at close to the speed of light yields a new solution for the pulsar magnetosphere everywhere that is ideal force-free except in the current layer. The main elements of the new solution are as follows: (1) the pulsar spindown rate of the aligned rotator is 23% larger than that of the orthogonal vacuum rotator; (2) only 60% of the magnetic flux that crosses the light cylinder opens up to infinity; (3) the electric current closes along the other 40%, which gradually converges to the equator; (4) this transfers 40% of the total pulsar spindown energy flux in the equatorial current sheet, which is then dissipated in the acceleration of particles and in high-energy electromagnetic radiation; and (5) there is no separatrix current layer. Our solution is a minimum free-parameter solution in that the equatorial current layer is electrostatically supported against collapse and thus does not require a thermal particle population. In this respect, it is one more step toward the development of a new standard solution. We discuss the implications for intermittent pulsars and long-duration gamma-ray bursts. We conclude that the physical conditions in the equatorial current layer determine the global structure of the pulsar magnetosphere.

  7. Towards a Realistic Pulsar Magnetosphere

    NASA Technical Reports Server (NTRS)

    Kalapotharakos, Constantinos; Kazanas, Demosthenes; Harding, Alice; Contopoulos, Ioannis

    2012-01-01

    We present the magnetic and electric field structures as well as the currents ami charge densities of pulsar magnetospberes which do not obey the ideal condition, E(raised dot) B = O. Since the acceleration of particles and the production of radiation requires the presence of an electric field component parallel to the magnetic field, E(sub ll) the structure of non-Ideal pulsar magnetospheres is intimately related to the production of pulsar radiation. Therefore, knowledge of the structure of non-Ideal pulsar maglletospheres is important because their comparison (including models for t he production of radiation) with observations will delineate the physics and the parameters underlying the pulsar radiation problem. We implement a variety of prescriptions that support nonzero values for E(sub ll) and explore their effects on the structure of the resulting magnetospheres. We produce families of solutions that span the entire range between the vacuum and the (ideal) Force-Free Electrodynamic solutions. We also compute the amount of dissipation as a fraction of the Poynting flux for pulsars of different angles between the rotation and magnetic axes and conclude that tltis is at most 20-40% (depending on t he non-ideal prescription) in the aligned rotator and 10% in the perpendicular one. We present also the limiting solutions with the property J = pc and discuss their possible implicatioll on the determination of the "on/ off" states of the intermittent pulsars. Finally, we find that solutions with values of J greater than those needed to null E(sub ll) locally produce oscillations, potentially observable in the data.

  8. Star Cluster Buzzing With Pulsars

    NASA Astrophysics Data System (ADS)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  9. Wideband Observations of Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Pennucci, Timothy T.

    2015-08-01

    Pulsars are exotic objects which have yielded a bounty of important astrophysical results. As rapidly rotating, highly magnetized neutron stars, pulsars' stable rotation and beamed radio emission enables their use as interstellar laboratory clocks. The extraordinary timing regularity of the millisecond pulsar (MSP) population permits some of the most precise measurements in astronomy. The discovery of MSPs raised the probability of directly detecting gravitational waves for the first time. Ongoing efforts by several pulsar timing array (PTA) collaborations compliment the ground- and space-based efforts of laser interferometers. One such PTA is the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). NANOGrav has recently employed a new set of wideband instruments to increase the sensitivity of their PTA, and the future of pulsar astronomy is moving towards progressively larger bandwidths. In this dissertation, we address the benefits and issues from adopting the new instrumentation, particularly for the scientific motivations of NANOGrav. We first develop a measurement technique for simultaneously obtaining pulse times-of-arrival (TOAs) and dispersion measures (DMs) using 2D models of evolving Gaussian components. We then apply the methodology broadly to a variety of pulsars, including a bright, test MSP in a globular cluster, the Galactic Center magnetar, and the entire suite of 37 MSPs from the NANOGrav 9-year data set. For a subset of these MSPs, we make targeted observations at specific orbital phases aimed at improving the timing models and constraining the Shapiro delay. With a few exceptions, we find positive or consistent timing results from the implementation of our first generation wideband timing protocol. Some highlights include: improved measurement uncertainties, mitigation of chromatic ISM effects, a reduction in the number of timing parameters and TOAs, signs of chromatic DMs, and at least one new pulsar mass.

  10. What brakes the Crab pulsar?

    NASA Astrophysics Data System (ADS)

    Čadež, A.; Zampieri, L.; Barbieri, C.; Calvani, M.; Naletto, G.; Barbieri, M.; Ponikvar, D.

    2016-03-01

    Context. Optical observations provide convincing evidence that the optical phase of the Crab pulsar follows the radio one closely. Since optical data do not depend on dispersion measure variations, they provide a robust and independent confirmation of the radio timing solution. Aims: The aim of this paper is to find a global mathematical description of Crab pulsar's phase as a function of time for the complete set of published Jodrell Bank radio ephemerides (JBE) in the period 1988-2014. Methods: We apply the mathematical techniques developed for analyzing optical observations to the analysis of JBE. We break the whole period into a series of episodes and express the phase of the pulsar in each episode as the sum of two analytical functions. The first function is the best-fitting local braking index law, and the second function represents small residuals from this law with an amplitude of only a few turns, which rapidly relaxes to the local braking index law. Results: From our analysis, we demonstrate that the power law index undergoes "instantaneous" changes at the time of observed jumps in rotational frequency (glitches). We find that the phase evolution of the Crab pulsar is dominated by a series of constant braking law episodes, with the braking index changing abruptly after each episode in the range of values between 2.1 and 2.6. Deviations from such a regular phase description behave as oscillations triggered by glitches and amount to fewer than 40 turns during the above period, in which the pulsar has made more than 2 × 1010 turns. Conclusions: Our analysis does not favor the explanation that glitches are connected to phenomena occurring in the interior of the pulsar. On the contrary, timing irregularities and changes in slow down rate seem to point to electromagnetic interaction of the pulsar with the surrounding environment.

  11. Systematic and Stochastic Variations in Pulsar Dispersion Measures

    NASA Astrophysics Data System (ADS)

    Lam, M. T.; Cordes, J. M.; Chatterjee, S.; Jones, M. L.; McLaughlin, M. A.; Armstrong, J. W.

    2016-04-01

    We analyze deterministic and random temporal variations in the dispersion measure (DM) from the full three-dimensional velocities of pulsars with respect to the solar system, combined with electron-density variations over a wide range of length scales. Previous treatments have largely ignored pulsars’ changing distances while favoring interpretations involving changes in sky position from transverse motion. Linear trends in pulsar DMs observed over 5-10 year timescales may signify sizable DM gradients in the interstellar medium (ISM) sampled by the changing direction of the line of sight to the pulsar. We show that motions parallel to the line of sight can also account for linear trends, for the apparent excess of DM variance over that extrapolated from scintillation measurements, and for the apparent non-Kolmogorov scalings of DM structure functions inferred in some cases. Pulsar motions through atomic gas may produce bow-shock ionized gas that also contributes to DM variations. We discuss the possible causes of periodic or quasi-periodic changes in DM, including seasonal changes in the ionosphere, annual variations of the solar elongation angle, structure in the heliosphere and ISM boundary, and substructure in the ISM. We assess the solar cycle’s role on the amplitude of ionospheric and solar wind variations. Interstellar refraction can produce cyclic timing variations from the error in transforming arrival times to the solar system barycenter. We apply our methods to DM time series and DM gradient measurements in the literature and assess their consistency with a Kolmogorov medium. Finally, we discuss the implications of DM modeling in precision pulsar timing experiments.

  12. A RADIO PULSAR SEARCH OF THE {gamma}-RAY BINARIES LS I +61 303 AND LS 5039

    SciTech Connect

    Virginia McSwain, M.; Ray, Paul S.; Ransom, Scott M.; Roberts, Mallory S. E.; Dougherty, Sean M.; Pooley, Guy G. E-mail: paul.ray@nrl.navy.mil E-mail: malloryr@gmail.com E-mail: guy@mrao.cam.ac.uk

    2011-09-01

    LS I +61 303 and LS 5039 are exceptionally rare examples of high-mass X-ray binaries with MeV-TeV emission, making them two of only five known '{gamma}-ray binaries'. There has been disagreement within the literature over whether these systems are microquasars, with stellar winds accreting onto a compact object to produce high energy emission and relativistic jets, or whether their emission properties might be better explained by a relativistic pulsar wind colliding with the stellar wind. Here we present an attempt to detect radio pulsars in both systems with the Green Bank Telescope. The upper limits of flux density are between 4.1 and 14.5 {mu}Jy, and we discuss the null results of the search. Our spherically symmetric model of the wind of LS 5039 demonstrates that any pulsar emission will be strongly absorbed by the dense wind unless there is an evacuated region formed by a relativistic colliding wind shock. LS I +61 303 contains a rapidly rotating Be star whose wind is concentrated near the stellar equator. As long as the pulsar is not eclipsed by the circumstellar disk or viewed through the densest wind regions, detecting pulsed emission may be possible during part of the orbit.

  13. Search for Millisecond Pulsars for the Pulsar Timing Array project

    NASA Astrophysics Data System (ADS)

    Milia, S.

    2012-03-01

    Pulsars are rapidly rotating highly magnetised neutron stars (i.e. ultra dense stars, where about one solar mass is concentrated in a sphere with a radius of ~ 10 km), which irradiate radio beams in a fashion similar to a lighthouse. As a consequence, whenever the beams cut our line of sight we perceive a radio pulses, one (or two) per pulsar rotation, with a frequency up to hundred of times a second. Owing to their compact nature, rapid spin and high inertia, pulsars are in general fairly stable rotators, hence the Times of Arrival (TOAs) of the pulses at a radio telescope can be used as the ticks of a clock. This holds true in particular for the sub­class of the millisecond pulsars (MSPs), having a spin period smaller than the conventional limit of 30 ms, whose very rapid rotation and relatively older age provide better rotational stability than the ordinary pulsars. Indeed, some MSPs rotate so regularly that they can rival the best atomic clocks on Earth over timespan of few months or years.This feature allows us to use MSPs as tools in a cosmic laboratory, by exploiting a procedure called timing, which consists in the repeated and regular measurement of the TOAs from a pulsar and then in the search for trends in the series of the TOAs over various timespans, from fraction of seconds to decades.For example the study of pulsars in binary systems has already provided the most stringent tests to date of General Relativity in strong gravitational fields and has unambiguously showed the occurrence of the emission of gravitational waves from a binary system comprising two massive bodies in a close orbit. In last decades a new exciting perspective has been opened, i.e. to use pulsars also for a direct detection of the so far elusive gravitational waves and thereby applying the pulsar timing for cosmological studies. In fact, the gravitational waves (GWs) going across our Galaxy pass over all the Galactic pulsars and the Earth, perturbing the space­time at the

  14. High-Energy Emission at Shocks in Millisecond Pulsar Binaries

    NASA Astrophysics Data System (ADS)

    Kust Harding, Alice; Wadiasingh, Zorawar; Venter, Christo; Boettcher, Markus

    2016-04-01

    A large number of new Black Widow (BW) and Redback (RB) energetic millisecond pulsars have been discovered through radio searches of unidentified Fermi sources, increasing the known number of these systems from 4 to 28. We model the high-energy emission components from particles accelerated to several TeV in intrabinary shocks in BW and RB systems, and their predicted modulation at the binary orbital period. Synchrotron emission is expected at X-ray energies and such modulated emission has already been detected by Chandra and XMM. Inverse Compton emission from accelerated particles scattering the UV emission from the radiated companion star is expected in the Fermi and TeV bands. Detections or constraints on this emission will probe the unknown physics of pulsar winds.

  15. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Verbiest, Joris P. W.; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Yardley, Daniel Roger Billing; Ravi, Vikram; Oslowski, Stefan; Hotan, Aidan; Champion, David; Khoo, Jonathan; Shannon, Ryan; Chaudhary, Ankur

    2012-04-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  16. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; Coles, William; van Straten, Willem; Ravi, Vikram; Oslowski, Stefan; Khoo, Jonathan; Shannon, Ryan; Wang, Jingbo; Levin, Yuri

    2013-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  17. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Verbiest, Joris P. W.; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Yardley, Daniel Roger Billing; Ravi, Vikram; Oslowski, Stefan; Hotan, Aidan; Champion, David; Khoo, Jonathan; Shannon, Ryan; Chaudhary, Ankur

    2011-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  18. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; Coles, William; van Straten, Willem; Yardley, Daniel Roger Billing; Ravi, Vikram; Oslowski, Stefan; Khoo, Jonathan; Shannon, Ryan; Wang, Jingbo; Levin, Yuri

    2013-04-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  19. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Verbiest, Joris P. W.; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Ravi, Vikram; Oslowski, Stefan; Hotan, Aidan; Champion, David; Khoo, Jonathan; Shannon, Ryan; Chaudhary, Ankur

    2012-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CASPSR; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  20. A millisecond pulsar timing array

    NASA Astrophysics Data System (ADS)

    Hobbs, George; Manchester, Dick; Verbiest, Joris P. W.; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Jenet, Rick; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Yardley, Daniel Roger Billing; Oslowski, Stefan; Hotan, Aidan; Champion, David; Khoo, Jonathan; Shannon, Ryan; Chaudhary, Ankur

    2011-04-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  1. Quasispherical subsonic accretion in X-ray pulsars

    NASA Astrophysics Data System (ADS)

    Shakura, Nikolai I.; Postnov, Konstantin A.; Kochetkova, A. Yu; Hjalmarsdotter, L.

    2013-04-01

    A theoretical model is considered for quasispherical subsonic accretion onto slowly rotating magnetized neutron stars. In this regime, the accreting matter settles down subsonically onto the rotating magnetosphere, forming an extended quasistatic shell. Angular momentum transfer in the shell occurs via large-scale convective motions resulting, for observed pulsars, in an almost iso-angular-momentum \\omega \\sim 1/R^2 rotation law inside the shell. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instabilities, with allowance for cooling. A settling accretion regime is possible for moderate accretion rates \\dot M \\lesssim \\dot M_* \\simeq 4\\times 10^{16} g s ^{-1}. At higher accretion rates, a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and the accretion becomes highly nonstationary. Observations of spin-up/spin-down rates of quasispherically wind accreting equilibrium X-ray pulsars with known orbital periods (e.g., GX 301-2 and Vela X-1) enable us to determine the main dimensionless parameters of the model, as well as to estimate surface magnetic field of the neutron star. For equilibrium pulsars, the independent measurements of the neutron star magnetic field allow for an estimate of the stellar wind velocity of the optical companion without using complicated spectroscopic measurements. For nonequilibrium pulsars, a maximum value is shown to exist for the spin-down rate of the accreting neutron star. From observations of the spin-down rate and the X-ray luminosity in such pulsars (e.g., GX 1+4, SXP 1062, and 4U 2206+54), a lower limit can be put on the neutron star magnetic field, which in all cases turns out to be close to the standard value and which agrees with cyclotron line measurements. Furthermore, both explains the spin-up/spin-down of the pulsar frequency on large time-scales and also accounts for the irregular short

  2. Building a Natural Language Interface for the ATNF Pulsar Database for Speeding up Execution of Complex Queries

    NASA Astrophysics Data System (ADS)

    Tang, Rupert; Jenet, F.; Rangel, S.; Dartez, L.

    2010-01-01

    Until now, there has been no available natural language interfaces (NLI's) for querying a database of pulsars (rotating neutron stars emitting radiation at regular intervals). Currently, pulsar records are retrieved through an HTML form accessible via the Australia Telescope National Facility (ATNF) website where one needs to be familiar with pulsar attributes used by the interface (e.g. BLC). Using a NLI relinquishes the need for learning form-specific formalism and allows execution of more powerful queries than those supported by the HTML form. Furthermore, on database access that requires comparison of attributes for all the pulsar records (e.g. what is the fastest pulsar?), using a NLI for retrieving answers to such complex questions is definitely much more efficient and less error-prone. This poster presents the first NLI ever created for the ATNF pulsar database (ATNF-Query) to facilitate database access using complex queries. ATNF-Query is built using a machine learning approach that induces a semantic parser from a question corpus; the innovative application is intended to provide pulsar researchers or laymen with an intelligent language understanding database system for friendly information access.

  3. White dwarf pulsars as possible cosmic ray electron-positron factories

    NASA Astrophysics Data System (ADS)

    Kashiyama, Kazumi; Ioka, Kunihito; Kawanaka, Norita

    2011-01-01

    We suggest that white dwarf (WD) pulsars can compete with neutron star (NS) pulsars for producing the excesses of cosmic ray electrons and positrons (e±) observed by the PAMELA, ATIC/PPB-BETS, Fermi, and H.E.S.S. experiments. A merger of two WDs leads to a rapidly spinning WD with a rotational energy (˜1050erg) comparable to the NS case. The birth rate (˜10-2-10-3/yr/galaxy) is also similar, providing the right energy budget for the cosmic ray e±. Applying the NS theory, we suggest that the WD pulsars can in principle produce e± up to ˜10TeV. In contrast to the NS model, the adiabatic and radiative energy losses of e± are negligible since their injection continues after the expansion of the pulsar wind nebula, and hence it is enough that a fraction ˜1% of WDs are magnetized (˜107-109G) as observed. The long activity also increases the number of nearby sources (˜100), which reduces the Poisson fluctuation in the flux. The WD pulsars could dominate the quickly cooling e± above TeV energy as a second spectral bump or even surpass the NS pulsars in the observing energy range ˜10GeV-1TeV, providing a background for the dark matter signals and a nice target for the future AMS-02, CALET, and CTA experiment.

  4. Pulsar Astrometry with the VLBA

    NASA Astrophysics Data System (ADS)

    Brisken, W.

    2005-12-01

    Many features of the Very Long Baseline Array (VLBA) contrive to make it the best telescope for pulsar astrometry. The measured proper motions and parallaxes allow distances and transverse velocities to be determined. These in turn provide clues to questions spanning nuclear astrophysics on scales of 10-23 m to the distribution of gas in the Galaxy on scales of 1020 m. Three pulsars are discussed in this paper. Among pulsars, B0950+08 has the most accurate VLBI-determined parallax. B1133+16 has a very high transverse velocity; its radial velocity is discussed. B0656+14 is a thermally detected neutron star. Determination of its distance has allowed its radius to be measured and its association with the Monogem ring supernova remnant (SNR) to be established, allowing a long-standing question in cosmic ray astrophysics to be addressed.

  5. Interplanetary GPS using pulsar signals

    NASA Astrophysics Data System (ADS)

    Becker, W.; Bernhardt, M. G.; Jessner, A.

    2015-11-01

    An external reference system suitable for deep space navigation can be defined by fast spinning and strongly magnetized neutron stars, called pulsars. Their beamed periodic signals have timing stabilities comparable to atomic clocks and provide characteristic temporal signatures that can be used as natural navigation beacons, quite similar to the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location, the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. The unique properties of pulsars make clear already today that such a navigation system will have its application in future astronautics. In this paper we describe the basic principle of spacecraft navigation using pulsars and report on the current development status of this novel technology.

  6. String theories and millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Sanchez, N.; Signore, M.

    1988-11-01

    We discuss the two ways of connecting string theories (cosmic, fundamental and the connection between them) to the observational reality: (i) radioastronomy observations (millisecond pulsar timing), and (ii) elementary particle phenomenology (compactification schemes). We study the limits imposed on the string parameter Gμ by recent millisecond pulsar timings. Cosmic strings derived from GUTs agree with (i). For cosmic strings derived from fundamental strings themselves there is contradiction between (i) and (ii). One of these scenarios connecting string theory to reality must be revised (or the transition from fundamental into cosmic strings rejected). Meanwhile, millisecond pulsar can select one scenario, or reject both of them. UA 336 Laboratoire Associé au CNRS, Observatoire de Meudon et Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05, France.

  7. PINT, a New Pulsar Timing Software

    NASA Astrophysics Data System (ADS)

    Luo, Jing; Jenet, Fredrick A.; Ransom, Scott M.; Demorest, Paul; Van Haasteren, Rutger; Archibald, Anne

    2015-01-01

    We are presenting a new pulsar timing software PINT. The current pulsar timing group are heavily depending on Tempo/Tempo2, a package for analysis pulsar data. However, for a high accuracy pulsar timing related project, such as pulsar timing for gravitational waves, an alternative software is needed for the purpose of examing the results. We are developing a Tempo independent software with a different structure. Different modules is designed to be more isolated and easier to be expanded. Instead of C, we are using Python as our programming language for the advantage of flexibility and powerful docstring. Here, we are presenting the detailed design and the first result of the software.

  8. The Disturbance of a Millisecond Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

    Shannon, R. M.; Lentati, L. T.; Kerr, M.; Bailes, M.; Bhat, N. D. R.; Coles, W. A.; Dai, S.; Dempsey, J.; Hobbs, G.; Keith, M. J.; Lasky, P. D.; Levin, Y.; Manchester, R. N.; Osłowski, S.; Ravi, V.; Reardon, D. J.; Rosado, P. A.; Spiewak, R.; van Straten, W.; Toomey, L.; Wang, J.-B.; Wen, L.; You, X.-P.; Zhu, X.-J.

    2016-09-01

    Pulsar timing has enabled some of the strongest tests of fundamental physics. Central to the technique is the assumption that the detected radio pulses can be used to accurately measure the rotation of the pulsar. Here, we report on a broadband variation in the pulse profile of the millisecond pulsar J1643-1224. A new component of emission suddenly appears in the pulse profile, decays over four months, and results in a permanently modified pulse shape. Profile variations such as these may be the origin of timing noise observed in other millisecond pulsars. The sensitivity of pulsar-timing observations to gravitational radiation can be increased by accounting for this variability.

  9. The Disturbance of a Millisecond Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

    Shannon, R. M.; Lentati, L. T.; Kerr, M.; Bailes, M.; Bhat, N. D. R.; Coles, W. A.; Dai, S.; Dempsey, J.; Hobbs, G.; Keith, M. J.; Lasky, P. D.; Levin, Y.; Manchester, R. N.; Osłowski, S.; Ravi, V.; Reardon, D. J.; Rosado, P. A.; Spiewak, R.; van Straten, W.; Toomey, L.; Wang, J.-B.; Wen, L.; You, X.-P.; Zhu, X.-J.

    2016-09-01

    Pulsar timing has enabled some of the strongest tests of fundamental physics. Central to the technique is the assumption that the detected radio pulses can be used to accurately measure the rotation of the pulsar. Here, we report on a broadband variation in the pulse profile of the millisecond pulsar J1643‑1224. A new component of emission suddenly appears in the pulse profile, decays over four months, and results in a permanently modified pulse shape. Profile variations such as these may be the origin of timing noise observed in other millisecond pulsars. The sensitivity of pulsar-timing observations to gravitational radiation can be increased by accounting for this variability.

  10. The soft γ-ray pulsar population: a high-energy overview

    NASA Astrophysics Data System (ADS)

    Kuiper, L.; Hermsen, W.

    2015-06-01

    At high-energy γ-rays (>100 MeV), the Large Area Telescope (LAT) on the Fermi satellite already detected more than 145 rotation-powered pulsars (RPPs), while the number of pulsars seen at soft γ-rays (20 keV-30 MeV) remained small. We present a catalogue of 18 non-recycled RPPs from which presently non-thermal pulsed emission has been securely detected at soft γ-rays above 20 keV, and characterize their pulse profiles and energy spectra. For 14 of them, we report new results, (re)analysing mainly data from RXTE, INTEGRAL, XMM-Newton and Chandra. The soft γ-pulsars are all fast rotators and on average ˜9.3 times younger and ˜43 times more energetic than the Fermi LAT sample. The majority (11 members) exhibits broad, structured single pulse profiles, and only six have double (or even multiple, Vela) pulses. 15 soft γ-ray pulsar show hard power-law spectra in the hard X-ray band and reach maximum luminosities typically in the MeV range. For only 7 of the 18 soft γ-ray pulsars, pulsed emission has also been detected by the LAT, but 12 have a pulsar wind nebula (PWN) detected at TeV energies. For six pulsars with PWNe, we present also the spectra of the total emissions at hard X-rays, and for IGR J18490-0000, associated with HESS J1849-000 and PSR J1849-0001, we used our Chandra data to resolve and characterize the contributions from the point source and PWN. Finally, we also discuss a sample of 15 pulsars which are candidates for future detection of pulsed soft γ-rays, given their characteristics at other wavelengths.

  11. "Missing Link" Revealing Fast-Spinning Pulsar Mysteries

    NASA Astrophysics Data System (ADS)

    2009-05-01

    telescope during a large sky survey in 1998, and had been observed in visible light by the Sloan Digital Sky Survey in 1999, revealing a Sun-like star. When observed again in 2000, the object had changed dramatically, showing evidence for a rotating disk of material, called an accretion disk, surrounding the neutron star. By May of 2002, the evidence for this disk had disappeared. "This strange behavior puzzled astronomers, and there were several different theories for what the object could be," said Ingrid Stairs of the University of British Columbia, who has been visiting the Australia Telescope National Facility and Swinburne University this year. The 2007 GBT observations showed that the object is a millisecond pulsar, spinning 592 times per second. "No other millisecond pulsar has ever shown evidence for an accretion disk," Archibald said. "We know that another type of binary-star system, called a low-mass X-ray binary (LMXB), also contains a fast-spinning neutron star and an accretion disk, but these don't emit radio waves. We've thought that LMXBs probably are in the process of getting spun up, and will later emit radio waves as a pulsar. This object appears to be the 'missing link' connecting the two types of systems," she explained. "It appears this thing has flipped from looking like an LMXB to looking like a pulsar, as it experienced an episode during which material pulled from the companion star formed an accretion disk around the neutron star. Later, that mass transfer stopped, the disk disappeared, and the pulsar emerged," said Scott Ransom of the NRAO. The scientists have studied J1023 in detail with the GBT, with the Westerbork radio telescope in the Netherlands, with the Arecibo radio telescope in Puerto Rico, and with the Parkes radio telescope in Australia. Their results indicate that the neutron star's companion has less than half the Sun's mass, and orbits the neutron star once every four hours and 45 minutes. "This system gives us an unparalled 'cosmic

  12. Crustal entrainment and pulsar glitches.

    PubMed

    Chamel, N

    2013-01-01

    Large pulsar frequency glitches are generally interpreted as sudden transfers of angular momentum between the neutron superfluid permeating the inner crust and the rest of the star. Despite the absence of viscous drag, the neutron superfluid is strongly coupled to the crust due to nondissipative entrainment effects. These effects are shown to severely limit the maximum amount of angular momentum that can possibly be transferred during glitches. In particular, it is found that the glitches observed in the Vela pulsar require an additional reservoir of angular momentum.

  13. Crustal entrainment and pulsar glitches.

    PubMed

    Chamel, N

    2013-01-01

    Large pulsar frequency glitches are generally interpreted as sudden transfers of angular momentum between the neutron superfluid permeating the inner crust and the rest of the star. Despite the absence of viscous drag, the neutron superfluid is strongly coupled to the crust due to nondissipative entrainment effects. These effects are shown to severely limit the maximum amount of angular momentum that can possibly be transferred during glitches. In particular, it is found that the glitches observed in the Vela pulsar require an additional reservoir of angular momentum. PMID:23383772

  14. On the magnetization and origin of the millisecond pulsar 1937 + 214

    NASA Astrophysics Data System (ADS)

    Arons, J.

    1983-03-01

    The structure of the millisecond pulsar PSR1937 + 214 is shown to include a magnetosphere compatible with other radio pulsars, although no synchrotron radiation-emitting bright nebula has been observed. It is suggested that interstellar extinction lowers the nebular energy to below the detection threshold level for the Einstein Observatory. Constraints on the pulsars magnetic dipole moment indicate a minimum spin-down rate of 10 to the -19th. The low magnetization detected may arise from initially low magnetic fields or field decay. Models of an expanding gas bubble are described for the case of supersonic expansion if the object is less than 1000 yr old and subsonic expansion if older. A scenario of a groupe of short period, weakly magnetized neutron stars is discussed.

  15. Models for X-Ray Emission from Isolated Pulsars

    NASA Technical Reports Server (NTRS)

    Wang, F. Y.-H.; Ruderman, M.; Halpern, Jules P.; Zhu, T.; Oliversen, Ronald (Technical Monitor)

    2001-01-01

    A model is proposed for the observed combination of power-law and thermal X-rays from rotationally powered pulsars. For gamma-ray pulsars with accelerators very many stellar radii above the neutron star surface, 100 MeV curvature gamma-rays from e(-) or e(+) flowing starward out of such accelerators are converted to e1 pairs on closed field lines all around the star. These pairs strongly affect X-ray emission from near the star in two ways. (1) The pairs are a source of synchrotron emission immediately following their creation in regions where B approx. 10(exp 10) G. This emission, in the photon energy range 0.1 keV less than E(sub X) less than 5 MeV, has a power-law spectrum with energy index 0.5 and X-ray luminosity that depends on the back-flow current, and is typically approx. 10(exp 33) ergs/ s. (2) The pairs ultimately a cyclotron resonance "blanket" surrounding the star except for two holes along the open field line bundles which pass through it. In such a blanket the gravitational pull on e(+,-) pairs toward the star is balanced by the hugely amplified push of outflowing surface emitted X-rays wherever cyclotron resonance occurs. Because of it the neutron star is surrounded by a leaky "hohlraum" of hot blackbody radiation with two small holes, which prevents direct X-ray observation of a heated polar cap of a gamma-ray pulsar. Weakly spin modulated radiation from the blanket together with more strongly spin-modulated radiation from the holes through it would then dominate observed low energy (0.1-10 keV) emission. For non-y-ray pulsars, in which no such accelerators with their accompanying extreme relativistic back-flow toward the star are expected, optically thick e1 resonance blankets should not form (except in special cases very close to the open field line bundle). From such pulsars blackbody radiation from both the warm stellar surface and the heated polar caps should be directly observable. In these pulsars, details of the surface magnetic field

  16. Spectrum-luminosity dependence of radiation from the polar emitting regions in accreting magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Klochkov, Dmitry

    2016-04-01

    The recent progress in observational techniques allowed one to probe the evolution of the X-ray spectrum in accreting pulsars (especially, of the cyclotron absorption line - the key spectral feature of accreting magnetized neutron stars) in great detail on various timescales, from pulse-to-pulse variability to secular trends. Particularly interesting are the discovered spectrum-luminosity correlations which are being used to infer the structure and physical characteristics of the pulsar's polar emitting region. I will present the latest developments in the modeling of the emitting structure (accretion column/mound/spot) aimed at explaining the observed spectrum-luminosity dependences.

  17. White Dwarf Pulsars

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph

    1998-01-01

    Work on NAG5-3288 ("White Dwarf Pulsars") has been fully integrated with the identically titled project NAG5-4734. The final report below is the same, since the data analysis and interpretative work are integrated, as are the resulting (previous and in-pipeline) publications. The proposal was designed to study pulse and orbital modulations in candidate DQ Herculis stars. Data on 5 stars were obtained. The best results were obtained on YY Draconis, which exhibited a strongly pulsed hard X-ray flux, and even suggested a transition between one-pole and two-pole emission during the course of the observation. This result is being readied for inclusion in a comprehensive study of YY Draconis. A strong pulsation appeared to be present also in H0857-242, but with a period of - 50 minutes, confusion with the first harmonic of the satellite's orbital frequency is possible. So that result is uncertain and is "on ice". A negative result was obtained on 4UO608-49 (V347 Pup), suggesting either that the X-ray identification is incorrect, or that the source is very transient. Finally, data was obtained on V1432 Aql and WZ Sge, respectively the slowest and fastest of these stars. Combined with the ASCA data, the high-energy data demonstrates the latter to contain a white dwarf rotating with P = 27.87 s (Patterson et al. 1998, PASP, 110, 403). Optical photometry contemporaneous with the X-ray data was obtained of V1432 Aql, in order to study the variations in the eclipse waveform. As anticipated, the width and centroid of the eclipse appeared to vary with the 50-day "supercycle".

  18. Search for VHE {gamma}-ray emission in the vicinity of selected pulsars of the Northern Sky with VERITAS

    SciTech Connect

    Aliu, Ester

    2008-12-24

    It is generally believed that pulsars dissipate their rotational energy through powerful winds of relativistic particles. Confinement of these winds leads to the formation of luminous pulsar wind nebulae (PWNe) seen across the electromagnetic spectrum in synchrotron and inverse Compton emission. Recently, many new detections have been produced at the highest energies by Very High Energy (VHE){gamma}-ray observations, identifying PWNe as among the most common sources of galactic VHE {gamma}-ray emission. We report here on the preliminary results of a search for VHE {gamma}-ray emission towards a selection of energetic and/or close pulsars in the Northern hemisphere in the first year of operations of the full VERITAS array.

  19. A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

    SciTech Connect

    Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire; Langston, Glen

    2013-04-15

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.

  20. Braking Index of Isolated Pulsars

    NASA Astrophysics Data System (ADS)

    Hamil, Oliver; Stone, Jirina; Urbanec, Martin; Urbancova, Gabriela

    2015-04-01

    Isolated pulsars are rotating neutron stars with accurately measured angular velocities Ω, and their time derivatives which show unambiguously that the pulsars are slowing down. The exact mechanism of the spin-down is a question of debate in detail, but the commonly accepted view is that it arises through emission of magnetic dipole radiation (MDR). The energy loss by a rotating pulsar is 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, equal to the ratio (ΩΩ̈)/ Ω˙2 . The simple MDR model predicts the value of n = 3, but observations of isolated pulsars provide rather precise values of n, individually accurate to a few percent or better, in the range 1 < n < 2.8, which is consistently less than the predictions of the MDR model. In this work, we study the dynamical limits of the MDR model as a function of angular velocity. The effects of variation in the rest mass, the moment of inertia, and the dependence on a realistic Equation of State of the rotating star are considered. Furthermore, we introduce a simulated superfluid effect by which the angular momentum of the core is eliminated from the calculation.

  1. RESISTIVE SOLUTIONS FOR PULSAR MAGNETOSPHERES

    SciTech Connect

    Li, Jason; Spitkovsky, Anatoly; Tchekhovskoy, Alexander

    2012-02-10

    The current state of the art in the modeling of pulsar magnetospheres invokes either the vacuum or force-free limits for the magnetospheric plasma. Neither of these limits can simultaneously account for both the plasma currents and the accelerating electric fields that are needed to explain the morphology and spectra of high-energy emission from pulsars. To better understand the structure of such magnetospheres, we combine accelerating fields and force-free solutions by considering models of magnetospheres filled with resistive plasma. We formulate Ohm's law in the minimal velocity fluid frame and construct a family of resistive solutions that smoothly bridges the gap between the vacuum and the force-free magnetosphere solutions. The spin-down luminosity, open field line potential drop, and the fraction of open field lines all transition between the vacuum and force-free values as the plasma conductivity varies from zero to infinity. For fixed inclination angle, we find that the spin-down luminosity depends linearly on the open field line potential drop. We consider the implications of our resistive solutions for the spin-down of intermittent pulsars and sub-pulse drift phenomena in radio pulsars.

  2. RADIO-QUIET AND RADIO-LOUD PULSARS: SIMILAR IN GAMMA-RAYS BUT DIFFERENT IN X-RAYS

    SciTech Connect

    Marelli, M.; Mignani, R. P.; Luca, A. De; Salvetti, D.; Parkinson, P. M. Saz; Hartog, P. R. Den

    2015-04-01

    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet (RQ) γ-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from γ-ray pulsar timing. For PSR J2030+4415 we found evidence for a ∼10″-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. and confirm that, on average, the γ-ray-to-X-ray flux ratios (F{sub γ}/F{sub X}) of RQ pulsars are higher than for the radio-loud (RL) ones. Furthermore, while the F{sub γ}/F{sub X} distribution features a single peak for the RQ pulsars, the distribution is more dispersed for the RL ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  3. Observations of gamma-ray pulsars at the highest energies with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Saz Parkinson, Pablo

    2016-07-01

    One of the most exciting developments in pulsar astrophysics in recent years has been the detection, with ground-based instruments (VERITAS, MAGIC), of pulsed gamma-ray emission from the Crab at very high energies (VHE, E>100 GeV). The Large Area Telescope (LAT) on board the Fermi satellite has detected over 160 pulsars above 100 MeV. Twenty-eight of these have been shown to emit pulsations above 10 GeV and approximately a dozen show emission above 25 GeV. While most gamma-ray pulsars are well-fitted in the GeV range by a power law with an exponential cut-off at around a few GeV, some emission models predict emission at energies above 100 GeV, either through a power-law extrapolation of the low-energy spectrum, or via a new (e.g. Inverse Compton) component. We will present results of our search for high-energy emission from LAT-detected gamma-ray pulsars using the latest Pass 8 data and discuss the prospects of finding the next VHE pulsar, providing a good target (or targets) for follow-up observations with current and future ground-based observatories, like CTA.

  4. X-rays from radio pulsars - The detection of PSR 1055-52

    NASA Technical Reports Server (NTRS)

    Cheng, A. F.; Helfand, D. J.

    1983-01-01

    The short-period pulsar PSR 1055-52 has been detected as a soft X-ray source in the course of an Einstein Observatory survey of radio pulsars. Its X-ray to radio luminosity ratio is about 10,000, although the X-rays are not modulated at the neutron star's rotation frequency. High spatial resolution observations suggest that a significant fraction of the emission comes from an extended region surrounding the pulsar. Several possible scenarios for the origin of both point and extended X-ray emission from isolated neutron stars are investigated: radiation from the hot stellar surface, from hot polar caps, and from an optically thick atmosphere, as well as from a circumstellar nebula emitting thermal bremsstrahlung or synchrotron radiation. It is concluded that the spatial, spectral, and temporal characteristics of this source are most consistent with a model in which relativistic particles generated by the pulsar are radiating synchrotron X-rays in the surrounding magnetic field; i.e., that PSR 1055 is embedded in a mini-Crab nebula. Observational tests of this hypothesis are suggested, and the implications of this result for pulsar evolution are briefly discussed.

  5. Magnetar-like X-ray bursts from an anomalous X-ray pulsar.

    PubMed

    Gavriil, F P; Kaspi, V M; Woods, P M

    2002-09-12

    Anomalous X-ray pulsars (AXPs) are a class of rare X-ray emitting pulsars whose energy source has been perplexing for some 20 years. Unlike other X-ray emitting pulsars, AXPs cannot be powered by rotational energy or by accretion of matter from a binary companion star, hence the designation 'anomalous'. Many of the rotational and radiative properties of the AXPs are strikingly similar to those of another class of exotic objects, the soft-gamma-ray repeaters (SGRs). But the defining property of the SGRs--their low-energy-gamma-ray and X-ray bursts--has not hitherto been observed for AXPs. Soft-gamma-ray repeaters are thought to be 'magnetars', which are young neutron stars whose emission is powered by the decay of an ultra-high magnetic field; the suggestion that AXPs might also be magnetars has been controversial. Here we report two X-ray bursts, with properties similar to those of SGRs, from the direction of the anomalous X-ray pulsar 1E1048.1 - 5937. These events imply a close relationship (perhaps evolutionary) between AXPs and SGRs, with both being magnetars.

  6. The global return current in a pulsar's magnetosphere

    NASA Astrophysics Data System (ADS)

    Barzilay, Yudith

    2016-08-01

    An open issue in pulsar's models is the current adjustment between the gap current and the global current that depends on the global structure of the pulsar's magnetosphere. Here I propose a mechanism for the global return current in pulsars.

  7. The Vela pulsar with an active fallback disk

    SciTech Connect

    Özsükan, Gökçe; Ekşi, K. Yavuz; Hambaryan, Valeri; Neuhäuser, Ralph; Hohle, Markus M.; Ginski, Christian; Werner, Klaus

    2014-11-20

    Fallback disks are expected to form around young neutron stars. The presence of these disks can be revealed by their blackbody spectrum in the infrared, optical, and UV bands. We present a re-reduction of the archival optical and infrared data of the Vela pulsar, together with the existing infrared and UV spectrum of Vela, and model their unpulsed components with the blackbody spectrum of a supernova debris disk. We invoke the quiescent disk solution of Sunyaev and Shakura for the description of the disk in the propeller stage and find the inner radius of the disk to be inside the light cylinder radius. We perform a high-resolution X-ray analysis with XMM-Newton and find a narrow absorption feature at 0.57 keV that can be interpreted as the K {sub α} line of He-like oxygen (O VII). The strength of the line indicates an element over-abundance in our line of sight exceeding the amounts that would be expected from interstellar medium. The spectral feature may originate from the pulsar wind nebula and may be partly caused by the reprocessed X-ray radiation by the fallback disk. We discuss the lower-than-three braking index of Vela as partially due to the contribution of the propeller torques. Our results suggest that the pulsar mechanism can work simultaneously with the propeller processes and that the debris disks can survive the radiation pressure for at least ∼10{sup 4} yr. As Vela is a relatively close object, and a prototypical pulsar, the presence of a disk, if confirmed, may indicate the ubiquity of debris disks around young neutron stars.

  8. Gamma-Ray Pulsar Studies With GLAST

    SciTech Connect

    Thompson, D.J.; /NASA, Goddard

    2011-11-23

    Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

  9. Relativistic spin precession in the double pulsar.

    PubMed

    Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea

    2008-07-01

    The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%.

  10. Relativistic spin precession in the double pulsar.

    PubMed

    Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea

    2008-07-01

    The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%. PMID:18599782

  11. Gamma-Ray Pulsar Studies with GLAST

    SciTech Connect

    Thompson, D. J.

    2008-02-27

    Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

  12. A Pulsar and a Disk

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-07-01

    Recent, unusual X-ray observations from our galactic neighbor, the Small Magellanic Cloud, have led to an interesting model for SXP 214, a pulsar in a binary star system.Artists illustration of the magnetic field lines of a pulsar, a highly magnetized, rotating neutron star. [NASA]An Intriguing BinaryAn X-ray pulsar is a magnetized, rotating neutron star in a binary system with a stellar companion. Material is fed from the companion onto the neutron star, channeled by the objects magnetic fields onto a hotspot thats millions of degrees. This hotspot rotating past our line of sight is what produces the pulsations that we observe from X-ray pulsars.Located in the Small Magellanic Cloud, SXP 214 is a transient X-ray pulsar in a binary with a Be-type star. This star is spinning so quickly that material is thrown off of it to form a circumstellar disk.Recently, a team of authors led by JaeSub Hong (Harvard-Smithsonian Center for Astrophysics) have presented new Chandra X-ray observations of SXP 214, tracking it for 50 ks (~14 hours) in January 2013. These observations reveal some very unexpected behavior for this pulsar.X-ray PuzzleThe energy distribution of the X-ray emission from SXP 214 over time. Dark shades or blue colors indicate high counts, and light shades or yellow colors indicate low counts. Lower-energy X-ray emission appeared only later, after about 20 ks. [Hong et al. 2016]Three interesting pieces of information came from the Chandra observations:SXP 214s rotation period was measured to be 211.5 s an increase in the spin rate since the discovery measurement of a 214-second period. Pulsars usually spin down as they lose angular momentum over time so what caused this one to spin up?Its overall X-ray luminosity steadily increased over the 50 ks of observations.Its spectrum became gradually softer (lower energy) over time; in the first 20 ks, the spectrum only consisted of hard X-ray photons above 3 keV, but after 20 ks, softer X-ray photons below 2 ke

  13. The Contribution of Millisecond Pulsars to the Local Electron / Positron Spectrum

    NASA Astrophysics Data System (ADS)

    Venter, Christo; Buesching, Ingo; Harding, Alice; Kopp, Andreas; Gonthier, Peter

    The high energies of gamma-ray photons (as well as the presence of lower-energy photons) coupled with the intense magnetic fields characterizing younger pulsars enable formation of electron-positron pair cascades which fills the pulsar magnetosphere with plasma and also feeds an outflowing particle wind that may create a surrounding pulsar wind nebula (PWN). Although this scenario was originally thought to be unique to the younger pulsar population, Fermi LAT demonstrated that the light curves of millisecond pulsars (MSPs) are generally very similar to those of younger pulsars, requiring copious pair production even for this older class with much lower surface magnetic fields and spin-down power. These pair cascades may thus be a primary source of Galactic electrons and positrons, and may present an astrophysical explanation for the observed enhancement in positron flux in the high-energy band. We investigate Galactic MSPs contribution to the flux of local cosmic-ray electrons and positrons. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic MSPs, taking into account the latest Fermi observations to calibrate the model output. Next, we simulate pair cascade spectra from these MSPs using a model that invokes an offset-dipole magnetic field, as this increases the pair production rate relative to a standard dipole field geometry. The model source pair spectra may extend to several TeV, depending on pulsar properties, neutron star equation of state, and magnetic polar cap offset. Since MSPs are not surrounded by PWNe or supernova shells, we can assume that the pairs escape from the pulsar environment without energy loss and undergo losses only in the intergalactic medium. We lastly compute the spectrum of the transported electrons and positrons at Earth, following their diffusion and energy loss through the Galaxy. We will compare our results with the observed local interstellar spectrum and

  14. "A Search For The Young and Energetic Pulsar in G328.4+0.2"

    NASA Technical Reports Server (NTRS)

    Gaensler, Bryan M.

    2005-01-01

    The pulsar-powered nebula G328.4+0.2 is one of the largest and most luminous such sources known. The nature of G328.4+0.2 has been a source of controversy - the object s flat radio spectral index has been used to argue that this object is a young pulsar wind nebula (PWN), while others have used radial protrusions in the magnetic field orientation along the source s outer edge to argue that it is an old supernova remnant (SNR). In the first interpretation, the X-ray nebula inside this radio source would be located inside the central "bar" detected in the radio. In the second interpretation, the expectation is that the X-ray PWN would be located at either end of this central "bar". The goals of our XMM observation were to try and detect the pulsar, and to use its location and other properties to distinguish between the above two possibilities.

  15. X-RAY STUDIES OF THE BLACK WIDOW PULSAR PSR B1957+20

    SciTech Connect

    Huang, R. H. H.; Kong, A. K. H.; Takata, J.; Cheng, K. S.; Hui, C. Y.; Lin, L. C. C.

    2012-11-20

    We report on Chandra observations of the black widow pulsar, PSR B1957+20. Evidence for a binary-phase dependence of the X-ray emission from the pulsar is found with a deep observation. The binary-phase-resolved spectral analysis reveals non-thermal X-ray emission of PSR B1957+20, confirming the results of previous studies. This suggests that the X-rays are mostly due to intra-binary shock emission, which is strongest when the pulsar wind interacts with the ablated material from the companion star. The geometry of the peak emission is determined in our study. The marginal softening of the spectrum of the non-thermal X-ray tail may indicate that particles injected at the termination shock are dominated by synchrotron cooling.

  16. Birth of millisecond pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.; Bailyn, C. D.

    1988-01-01

    It is argued here that accretion-induced collapse of white dwarfs in binaries can form millisecond pulsars directly without requiring a precursor low-mass X-ray binary stage. Ablation of the precollapse binary companion by the millisecond pulsar's radiation field, a process invoked to explain some of the characteristics of the recently discovered eclipsing millisecond pulsar, can then yield isolated neutron stars witout requiring an additional stellar encounter.

  17. High-sensitivity observations of 28 pulsars

    NASA Technical Reports Server (NTRS)

    Weisberg, J. M.; Armstrong, B. K.; Backus, P. R.; Cordes, J. M.; Boriakoff, V.

    1986-01-01

    Average 430-MHz pulse profiles and, where possible, modulation indices and pulse-nulling fractions are computed for 28 pulsars. Morphological classifications are determined for most of the pulsars. It is found that core emission components tend to have lower modulation indices than conal components, and that pulsars having only a core component never exhibit pulse pulling. PSR 1612 + 07 is shown to undergo mode changes.

  18. Self-modulational formation of pulsar microstructures

    NASA Technical Reports Server (NTRS)

    Chian, A. C.-L.; Kennel, C. F.

    1987-01-01

    A nonlinear plasma theory for self modulation of pulsar radio pulses is discussed. A nonlinear Schroedinger equation is derived for strong electromagnetic waves propagating in an electron positron plasma. The nonlinearities arising from wave intensity induced particle mass variation may excite the modulational instability of circularly and linearly polarized pulsar radiation. The resulting wave envelopes can take the form of periodic wave trains or solitons. These nonlinear stationary waveforms may account for the formation of pulsar microstructures.

  19. The γ-ray Pulsar J0633+0632 in X-rays

    NASA Astrophysics Data System (ADS)

    Danilenko, Andrey; Shternin, Peter; Karpova, Anna; Zyuzin, Dima; Shibanov, Yuriy

    2015-10-01

    We analysed Chandra observations of the bright Fermi pulsar J0633+0632 and found evidence of an absorption feature in its spectrum at 804+42 -26 eV (the errors are at 90% confidence) with equivalent width of 63+47 -36 eV. In addition, we analysed in detail the X-ray spectral continuum taking into account correlations between the interstellar absorption and the distance to the source. We confirm early findings that the spectrum contains non-thermal and thermal components. The latter is equally well described by the blackbody and magnetised atmosphere models and can be attributed to the emission from the bulk of the stellar surface in both cases. The distance to the pulsar is constrained in a range of 1-4 kpc from the spectral fits. We infer the blackbody surface temperature of 108+22 -14 eV, while for the atmosphere model, the temperature, as seen by a distant observer, is 53+12 -7 eV. In the latter case, J0633+0632 is one of the coldest middle-aged isolated neutron stars. Finally, it powers an extended pulsar wind nebula whose shape suggests a high pulsar proper motion. Looking backwards the direction of the presumed proper motion, we found a likely birthplace of the pulsar-the Rosette nebula, a 50-Myr-old active star-forming region located at about 1.5° from the pulsar. If true, this constrains the distance to the pulsar in the range of 1.2-1.8 kpc.

  20. Population synthesis of isolated neutron stars with magneto-rotational evolution - II. From radio-pulsars to magnetars

    NASA Astrophysics Data System (ADS)

    Gullón, M.; Pons, J. A.; Miralles, J. A.; Viganò, D.; Rea, N.; Perna, R.

    2015-11-01

    Population synthesis studies constitute a powerful method to reconstruct the birth distribution of periods and magnetic fields of the pulsar population. When this method is applied to populations in different wavelengths, it can break the degeneracy in the inferred properties of initial distributions that arises from single-band studies. In this context, we extend previous works to include X-ray thermal emitting pulsars within the same evolutionary model as radio-pulsars. We find that the cumulative distribution of the number of X-ray pulsars can be well reproduced by several models that, simultaneously, reproduce the characteristics of the radio-pulsar distribution. However, even considering the most favourable magneto-thermal evolution models with fast field decay, lognormal distributions of the initial magnetic field overpredict the number of visible sources with periods longer than 12 s. We then show that the problem can be solved with different distributions of magnetic field, such as a truncated lognormal distribution, or a binormal distribution with two distinct populations. We use the observational lack of isolated neutron stars (NSs) with spin periods P > 12 s to establish an upper limit to the fraction of magnetars born with B > 1015 G (less than 1 per cent). As future detections keep increasing the magnetar and high-B pulsar statistics, our approach can be used to establish a severe constraint on the maximum magnetic field at birth of NSs.

  1. Pulsar discovery by global volunteer computing.

    PubMed

    Knispel, B; Allen, B; Cordes, J M; Deneva, J S; Anderson, D; Aulbert, C; Bhat, N D R; Bock, O; Bogdanov, S; Brazier, A; Camilo, F; Champion, D J; Chatterjee, S; Crawford, F; Demorest, P B; Fehrmann, H; Freire, P C C; Gonzalez, M E; Hammer, D; Hessels, J W T; Jenet, F A; Kasian, L; Kaspi, V M; Kramer, M; Lazarus, P; van Leeuwen, J; Lorimer, D R; Lyne, A G; Machenschalk, B; McLaughlin, M A; Messenger, C; Nice, D J; Papa, M A; Pletsch, H J; Prix, R; Ransom, S M; Siemens, X; Stairs, I H; Stappers, B W; Stovall, K; Venkataraman, A

    2010-09-10

    Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period; the pulsar likely has closely aligned magnetic and spin axes. The massive computing power provided by volunteers should enable many more such discoveries.

  2. Pulsar Electrodynamics: a Time-dependent View

    SciTech Connect

    Spitkovsky, Anatoly; /KIPAC, Menlo Park

    2006-04-10

    Pulsar spindown forms a reliable yet enigmatic prototype for the energy loss processes in many astrophysical objects including accretion disks and back holes. In this paper we review the physics of pulsar magnetospheres, concentrating on recent developments in force-free modeling of the magnetospheric structure. In particular, we discuss a new method for solving the equations of time-dependent force-free relativistic MHD in application to pulsars. This method allows to dynamically study the formation of the magnetosphere and its response to perturbations, opening a qualitatively new window on pulsar phenomena. Applications of the method to other magnetized rotators, such as magnetars and accretion disks, are also discussed.

  3. A state change in the missing link binary pulsar system PSR J1023+0038

    SciTech Connect

    Stappers, B. W.; Lyne, A. G.; Archibald, A. M.; Hessels, J. W. T.; Bassa, C. G.; Janssen, G. H.; Bogdanov, S.; Kaspi, V. M.; Patruno, A.; Tendulkar, S.; Hill, A. B.; Glanzman, T.

    2014-07-20

    We present radio and γ-ray observations, which, along with concurrent X-ray observations, reveal that the binary millisecond pulsar (MSP)/low-mass X-ray binary transition system PSR J1023+0038 has undergone a transformation in state. Whereas until recently the system harbored a bright millisecond radio pulsar, the radio pulsations at frequencies between 300 to 5000 MHz have now become undetectable. Concurrent with this radio disappearance, the γ-ray flux of the system has quintupled. We conclude that, though the radio pulsar is currently not detectable, the pulsar mechanism is still active and the pulsar wind, as well as a newly formed accretion disk, are together providing the necessary conditions to create the γ-ray increase. This system is the first example of a compact, low-mass binary which has shown significant state changes accompanied by large changes in γ-ray flux; it will continue to provide an exceptional test bed for better understanding the formation of MSPs as well as accretion onto neutron stars in general.

  4. PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope

    NASA Astrophysics Data System (ADS)

    Naidu, Arun; Joshi, Bhal Chandra; Manoharan, P. K.; Krishnakumar, M. A.

    2015-06-01

    This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a bandwidth of about four times larger (16 MHz) than that of the legacy system as well as its fluctuation spectrum with high temporal and frequency resolutions. The key point is that all the above modes operate in real time. This paper presents the design aspects of PONDER and outlines the design methodology for future similar backends. It also explains the principal operations of PONDER, illustrates its capabilities for a variety of pulsar and IPS observations and demonstrates its usefulness for a variety of astrophysical studies using the high sensitivity of the ORT.

  5. Signs of magnetic accretion in the young Be/X-ray pulsar SXP 1062

    NASA Astrophysics Data System (ADS)

    Ikhsanov, N. R.

    2012-07-01

    The spin behaviour of the neutron star in the newly discovered young Be/X-ray long-period pulsar SXP 1062 is discussed. The star is observed to rotate with the period of 1062 s, and spin down at the rate ˜-2.6 × 10-12 Hz s-1. I show that all of the conventional accretion scenarios encounter major difficulties in explaining the rapid spin-down of the pulsar. These difficulties can be, however, avoided within the magnetic accretion scenario in which the neutron star is assumed to accrete from a magnetized wind. The spin-down rate of the pulsar can be explained within this scenario provided the surface magnetic field of the neutron star is B*˜ 4 × 1013 G. I show that the age of the pulsar in this case lies in the range (2-4) × 104 yr, which is consistent with observations. The spin evolution of the pulsar is briefly discussed.

  6. Sampling the Radio Transient Universe: Studies of Pulsars and the Search for Extraterrestrial Intelligence

    NASA Astrophysics Data System (ADS)

    Chennamangalam, Jayanth

    The transient radio universe is a relatively unexplored area of astronomy, offering a variety of phenomena, from solar and Jovian bursts, to flare stars, pulsars, and bursts of Galactic and potentially even cosmological origin. Among these, perhaps the most widely studied radio transients, pulsars are fast-spinning neutron stars that emit radio beams from their magnetic poles. In spite of over 40 years of research on pulsars, we have more questions than answers on these exotic compact objects, chief among them the nature of their emission mechanism. Nevertheless, the wealth of phenomena exhibited by pulsars make them one of the most useful astrophysical tools. With their high densities, pulsars are probes of the nature of ultra-dense matter. Characterized by their high timing stability, pulsars can be used to verify the predictions of general relativity, discover planets around them, study bodies in the solar system, and even serve as an interplanetary (and possibly some day, interstellar) navigation aid. Pulsars are also used to study the nature of the interstellar medium, much like a flashlight illuminating airborne dust in a dark room. Studies of pulsars in the Galactic center can help answer questions about the massive black hole in the region and the star formation history in its vicinity. Millisecond pulsars in globular clusters are long-lived tracers of their progenitors, low-mass X-ray binaries, and can be used to study the dynamical history of those clusters. Another source of interest in radio transient astronomy is the hitherto undetected engineered signal from extraterrestrial intelligence. The Search for Extraterrestrial Intelligence (SETI) is an ongoing attempt at discovering the presence of technological life elsewhere in the Galaxy. In this work, I present my forays into two aspects of the study of the radio transient universe---pulsars and SETI. Firstly, I describe my work on the luminosity function and population size of pulsars in the globular

  7. Pair-Starved Pulsar Magnetospheres

    NASA Technical Reports Server (NTRS)

    Muslimov, Alex G.; Harding, Alice K.

    2009-01-01

    We propose a simple analytic model for the innermost (within the light cylinder of canonical radius, approx. c/Omega) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary angle between the NS spin and magnetic axes. We present the self-consistent solution of Maxwell's equations for the magnetic field and electric current in the pair-starved regime where the density of electron-positron plasma generated above the pulsar polar cap is not sufficient to completely screen the accelerating electric field and thus establish thee E . B = 0 condition above the pair-formation front up to the very high altitudes within the light cylinder. The proposed mode1 may provide a theoretical framework for developing the refined model of the global pair-starved pulsar magnetosphere.

  8. Particle acceleration in pulsar magnetospheres

    NASA Technical Reports Server (NTRS)

    Baker, K. B.

    1978-01-01

    The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.

  9. A Study of Dynamical and Emission Variabilities in Pulsars

    NASA Astrophysics Data System (ADS)

    Seymour, Andrew D.

    Pulsars are rapidly rotating highly magnetized neutron stars thought to have been formed in the core-collapse supernova of massive stars. Ever since their discovery, pulsars have shown complex behaviors. This is certainly true for their emission mechanism, which is still not fully understood. This is primarily because of the abrupt changes that appear in the pulse profile. Recent discoveries have shown that these emission changes effect the spin dynamics, particularly the spin-down rate. This indicates that pulsar emissions are even more complex than previously thought. The goal of this thesis is to apply new analysis techniques to help shed light on the pulsar emission problem. Over the past decade, it has become apparent that a class of `bursting pulsars' exist with the discovery of PSR J1752+2359 and PSR J1938+2213. In these pulsars, a sharp increase in the emission intensity is observed that then tends to systematically drop-off from pulse-to-pulse. We describe the discovery of such a relationship in high-sensitivity observations of the young (characteristic age of 90; 000 yrs) 0.33 s pulsar B0611+22 at both 327 MHz and 1400 MHz with the Arecibo observatory. While it was previously shown that B0611+22 has mode-switching properties, the data presented here show that this pulsar emits bursts with characteristic time-scales of several hundred seconds. At 327 MHz, the pulsar shows steady behavior in one emission mode which is enhanced by bursting emission slightly offset in pulse phase from this steady emission. Contrastingly at 1400 MHz, the two modes appear to behave in a competing operation while still offset in phase. Using a uctuation spectrum analysis, we also investigate each mode independently for sub-pulse drifting. Neither emission mode (i.e. during bursts or persistent emission) shows the presence of the drifting sub-pulse phenomenon. While further examples of this behavior and studies at different wavelengths are required, it appears that this

  10. A Study of Dynamical and Emission Variabilities in Pulsars

    NASA Astrophysics Data System (ADS)

    Seymour, Andrew D.

    Pulsars are rapidly rotating highly magnetized neutron stars thought to have been formed in the core-collapse supernova of massive stars. Ever since their discovery, pulsars have shown complex behaviors. This is certainly true for their emission mechanism, which is still not fully understood. This is primarily because of the abrupt changes that appear in the pulse profile. Recent discoveries have shown that these emission changes effect the spin dynamics, particularly the spin-down rate. This indicates that pulsar emissions are even more complex than previously thought. The goal of this thesis is to apply new analysis techniques to help shed light on the pulsar emission problem. Over the past decade, it has become apparent that a class of `bursting pulsars' exist with the discovery of PSR J1752+2359 and PSR J1938+2213. In these pulsars, a sharp increase in the emission intensity is observed that then tends to systematically drop-off from pulse-to-pulse. We describe the discovery of such a relationship in high-sensitivity observations of the young (characteristic age of 90; 000 yrs) 0.33 s pulsar B0611+22 at both 327 MHz and 1400 MHz with the Arecibo observatory. While it was previously shown that B0611+22 has mode-switching properties, the data presented here show that this pulsar emits bursts with characteristic time-scales of several hundred seconds. At 327 MHz, the pulsar shows steady behavior in one emission mode which is enhanced by bursting emission slightly offset in pulse phase from this steady emission. Contrastingly at 1400 MHz, the two modes appear to behave in a competing operation while still offset in phase. Using a uctuation spectrum analysis, we also investigate each mode independently for sub-pulse drifting. Neither emission mode (i.e. during bursts or persistent emission) shows the presence of the drifting sub-pulse phenomenon. While further examples of this behavior and studies at different wavelengths are required, it appears that this

  11. Probing for Pulsars in XMM Study of the Composite SNRS G327.1-1.1 and CTA 1

    NASA Technical Reports Server (NTRS)

    Mushotsky, Richard (Technical Monitor); Slane, Patrick

    2004-01-01

    The subject grant is for analysis of XMM data from the supernova remnant CTA1. Our investigation centered on the study of the compact source RX 50007.0+7302 that, based on our previous observations, appears to be a neutron star powering a wind nebula in the remnant interior. This compact source has also been suggested as the counterpart of the EGRET source 2EG J0008+7307. The analysis of the data from the compact source is complete. We find that the spectrum of the source is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar cap regions or to cooling emission from a light element atmosphere over the entire star. There is evidence of extended emission on small spatial scales which may correspond to structure in the underlying synchrotron nebula. Extrapolation of the nonthermal emission component to gamma-ray energies yields a flux that is consistent with that of 2EG J0008+7307, thus strengthening the proposition that there is a gamma-ray emitting pulsar at the center of CTA 1. Our timing studies with the EPIC pn data revealed no evidence for pulsations, however; we set an upper limit of 61% on the pulsed fraction from this source. The results from this study were presented.

  12. Searching for Pulsars Using Image Pattern Recognition

    NASA Astrophysics Data System (ADS)

    Zhu, W. W.; Berndsen, A.; Madsen, E. C.; Tan, M.; Stairs, I. H.; Brazier, A.; Lazarus, P.; Lynch, R.; Scholz, P.; Stovall, K.; Ransom, S. M.; Banaszak, S.; Biwer, C. M.; Cohen, S.; Dartez, L. P.; Flanigan, J.; Lunsford, G.; Martinez, J. G.; Mata, A.; Rohr, M.; Walker, A.; Allen, B.; Bhat, N. D. R.; Bogdanov, S.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J. S.; Desvignes, G.; Ferdman, R. D.; Freire, P. C. C.; Hessels, J. W. T.; Jenet, F. A.; Kaplan, D. L.; Kaspi, V. M.; Knispel, B.; Lee, K. J.; van Leeuwen, J.; Lyne, A. G.; McLaughlin, M. A.; Siemens, X.; Spitler, L. G.; Venkataraman, A.

    2014-02-01

    In the modern era of big data, many fields of astronomy are generating huge volumes of data, the analysis of which can sometimes be the limiting factor in research. Fortunately, computer scientists have developed powerful data-mining techniques that can be applied to various fields. In this paper, we present a novel artificial intelligence (AI) program that identifies pulsars from recent surveys by using image pattern recognition with deep neural nets—the PICS (Pulsar Image-based Classification System) AI. The AI mimics human experts and distinguishes pulsars from noise and interference by looking for patterns from candidate plots. Different from other pulsar selection programs that search for expected patterns, the PICS AI is taught the salient features of different pulsars from a set of human-labeled candidates through machine learning. The training candidates are collected from the Pulsar Arecibo L-band Feed Array (PALFA) survey. The information from each pulsar candidate is synthesized in four diagnostic plots, which consist of image data with up to thousands of pixels. The AI takes these data from each candidate as its input and uses thousands of such candidates to train its ~9000 neurons. The deep neural networks in this AI system grant it superior ability to recognize various types of pulsars as well as their harmonic signals. The trained AI's performance has been validated with a large set of candidates from a different pulsar survey, the Green Bank North Celestial Cap survey. In this completely independent test, the PICS ranked 264 out of 277 pulsar-related candidates, including all 56 previously known pulsars and 208 of their harmonics, in the top 961 (1%) of 90,008 test candidates, missing only 13 harmonics. The first non-pulsar candidate appears at rank 187, following 45 pulsars and 141 harmonics. In other words, 100% of the pulsars were ranked in the top 1% of all candidates, while 80% were ranked higher than any noise or interference. The

  13. Searching for pulsars using image pattern recognition

    SciTech Connect

    Zhu, W. W.; Berndsen, A.; Madsen, E. C.; Tan, M.; Stairs, I. H.; Brazier, A.; Lazarus, P.; Lynch, R.; Scholz, P.; Stovall, K.; Cohen, S.; Dartez, L. P.; Lunsford, G.; Martinez, J. G.; Mata, A.; Ransom, S. M.; Banaszak, S.; Biwer, C. M.; Flanigan, J.; Rohr, M. E-mail: berndsen@phas.ubc.ca; and others

    2014-02-01

    In the modern era of big data, many fields of astronomy are generating huge volumes of data, the analysis of which can sometimes be the limiting factor in research. Fortunately, computer scientists have developed powerful data-mining techniques that can be applied to various fields. In this paper, we present a novel artificial intelligence (AI) program that identifies pulsars from recent surveys by using image pattern recognition with deep neural nets—the PICS (Pulsar Image-based Classification System) AI. The AI mimics human experts and distinguishes pulsars from noise and interference by looking for patterns from candidate plots. Different from other pulsar selection programs that search for expected patterns, the PICS AI is taught the salient features of different pulsars from a set of human-labeled candidates through machine learning. The training candidates are collected from the Pulsar Arecibo L-band Feed Array (PALFA) survey. The information from each pulsar candidate is synthesized in four diagnostic plots, which consist of image data with up to thousands of pixels. The AI takes these data from each candidate as its input and uses thousands of such candidates to train its ∼9000 neurons. The deep neural networks in this AI system grant it superior ability to recognize various types of pulsars as well as their harmonic signals. The trained AI's performance has been validated with a large set of candidates from a different pulsar survey, the Green Bank North Celestial Cap survey. In this completely independent test, the PICS ranked 264 out of 277 pulsar-related candidates, including all 56 previously known pulsars and 208 of their harmonics, in the top 961 (1%) of 90,008 test candidates, missing only 13 harmonics. The first non-pulsar candidate appears at rank 187, following 45 pulsars and 141 harmonics. In other words, 100% of the pulsars were ranked in the top 1% of all candidates, while 80% were ranked higher than any noise or interference. The

  14. Pulsars at TeV

    NASA Astrophysics Data System (ADS)

    Edwards, P.

    1994-04-01

    The atmospheric Cerenkov technique is used to search for emission at energies above several hundred GeV from a variety of objects, including pulsars (see, e.g., reviews by Weekes, 1988, Phys. Rep., 160, 1; Weekes, 1992, Sp. Sci. Rev., 59, 315). Claims for TeV emission (from any source) should be of high significance, show gamma-ray-like properties, and be independently confirmed. By these criteria the Crab nebula is currently the only established pulsar-driven system to be observed at TeV energies (Weekes et al., 1989, Astrophys. J., 342, 379; Vacanti et al., 1991, Astrophys. J., 377, 467; Goret et al., 1993, Astron. Astrophys., 270, 401). The gamma-ray signal is not pulsed at TeV energies, leading to models of synchrotron self-Compton emission from the Crab nebula (e.g., De Jager and Harding, 1992, Astrophys. J., 396, 161), although other models have also been proposed (Kwok et al., 1991, Astrophys. J., 379, 653). While claims exist for TeV emission from, amongst others, the Vela pulsar (e.g., Bhat et al., 1987, Astron. Astrophys., 178, 242, Geminga (Vishwanath et al., 1993, Astron. Astrophys., 267, L5; Bowden et al., 1993, J. Phys. G: Nucl. Part. Phys., 19, L29), and PSR 1509-58 (Nel et al., 1992, Astrophys. pulsars have high values of E-dot/d2 (due to their proximity) and are thus potentially observable TeV sources. *The detection of TeV gamma-rays from millisecond pulsars has been considered recently by Smith (1993, Astrophys. -J., 408, 468).

  15. What is causing the eclipse in the millisecond binary pulsar

    SciTech Connect

    Rasio, F.A.; Shapiro, S.L.; Teukolsky, S.A. )

    1989-07-01

    Possible physical mechanisms for explaining the radio eclipses in the millisecond binary pulsar PSR 1957 + 20 are discussed. If, as recent observations suggest, the duration of the eclipses depends on the observing frequency, a plausible mechanism is free-free absorption of the radio pulses by a low-density ionized wind surrounding the companion. Detailed numerical calculations are performed for this case, and it is found that all of the observations made at 430 MHz can be reliably reproduced, including the asymmetry in the excess time delay of the pulses. The model leads to definite predictions for the duration of the eclipse at other observing frequencies, as well as the radio intensity and excess time delay of the pulses as a function of orbital phase. If the duration of the eclipses were found to be independent of frequency, then the likely mechanism would be reflection of the radio signal at a contact discontinuity between a high-density wind and the pulsar radiation. In this case, however, it is difficult to explain the observed symmetry of the eclipse. 12 refs.

  16. Non-thermal emission in astrophysical environments: From pulsars to supernova remnants

    NASA Astrophysics Data System (ADS)

    Lomiashvili, David

    The study of electromagnetic radiation from distant astrophysical objects provides essential data in understanding physics of these sources. In particular, non-thermal radiation provides great insight into the properties of local environments, particle populations, and emission mechanisms, knowledge which otherwise would remain untapped. Throughout the projects conducted for this dissertation, we modeled certain aspects of observed non-thermal emission from three classes of sources: radio pulsars, pulsar wind nebulae, and supernova remnants. Orbital variation in the double pulsar system PSR J0737-3039A/B can be used to probe the details of the magnetospheric structure of pulsar B. Strongly magnetized wind from pulsar A distorts the magnetosphere of pulsar B in a way similar to the solar wind's distortion of the Earth's magnetosphere. Using the two complimentary models of pulsar B's magnetosphere, adapted from the Earth's magnetosphere models by Dungey and Tsyganenko, we determine the precise location of the coherent radio emission generation region in pulsar B's magnetosphere. This analysis is complemented by modeling the observed evolution of the pulse profiles of B due to geodetic precession. The emission region is located at about 3750 stellar radii and has a horseshoe-like shape centered on the polar magnetic field lines. The best fit angular parameters of the emission region indicate that radio emission is generated on the field lines which, according to the theoretical models, originate close to the poles and carry the maximum current. When considered together, not only do the results of the two models converge, they can explain why the modulation of B's radio emission at A's period is observed only within a certain orbital phase region. We discuss the implications of these results for pulsar magnetospheric models and mechanisms of coherent radio emission generation. We also developed a spatially-resolved, analytic model for the high-energy non

  17. Multiwavelength Observations of the Redback Millisecond Pulsar J1048+2339

    NASA Astrophysics Data System (ADS)

    Deneva, J. S.; Ray, P. S.; Camilo, F.; Halpern, J. P.; Wood, K.; Cromartie, H. T.; Ferrara, E.; Kerr, M.; Ransom, S. M.; Wolff, M. T.; Chambers, K. C.; Magnier, E. A.

    2016-06-01

    We report on radio timing and multiwavelength observations of the 4.66 ms redback pulsar J1048+2339, which was discovered in an Arecibo search targeting the Fermi-Large Area Telescope source 3FGL J1048.6+2338. Two years of timing allowed us to derive precise astrometric and orbital parameters for the pulsar. PSR J1048+2339 is in a 6 hr binary and exhibits radio eclipses over half the orbital period and rapid orbital period variations. The companion has a minimum mass of 0.3 M ⊙, and we have identified a V ˜ 20 variable optical counterpart in data from several surveys. The phasing of its ˜1 mag modulation at the orbital period suggests highly efficient and asymmetric heating by the pulsar wind, which may be due to an intrabinary shock that is distorted near the companion, or to the companion’s magnetic field channeling the pulsar wind to specific locations on its surface. We also present gamma-ray spectral analysis of the source and preliminary results from searches for gamma-ray pulsations using the radio ephemeris.

  18. AN EXTREME PULSAR TAIL PROTRUDING FROM THE FRYING PAN SUPERNOVA REMNANT

    SciTech Connect

    Ng, C.-Y.; Bouchard, A.; Bucciantini, N.; Gaensler, B. M.; Camilo, F.; Chatterjee, S.

    2012-02-10

    The Frying Pan (G315.9-0.0) is a radio supernova remnant with a peculiar linear feature (G315.78-0.23) extending 10' radially outward from the rim of the shell. We present radio imaging and polarization observations obtained from the Molonglo Observatory Synthesis Telescope and the Australia Telescope Compact Array, confirming G315.78-0.23 as a bow-shock pulsar wind nebula (PWN) powered by the young pulsar J1437-5959. This is one of the longest pulsar tails observed in radio and it has a physical extent over 20 pc. We found a bow-shock standoff distance of 0.002 pc, smallest among similar systems, suggesting a large pulsar velocity over 1000 km s{sup -1} and a high Mach number {approx}200. The magnetic field geometry inferred from radio polarimetry shows a good alignment with the tail orientation, which could be a result of high flow speed. There are also hints that the postshock wind has a low magnetization and is dominated by electrons and positrons in energy. This study shows that PWNe can offer a powerful probe of their local environment, particularly for the case of a bow shock where the parent supernova shell is also detected.

  19. Radio polarimetry of Galactic Centre pulsars

    NASA Astrophysics Data System (ADS)

    Schnitzeler, D. H. F. M.; Eatough, R. P.; Ferrière, K.; Kramer, M.; Lee, K. J.; Noutsos, A.; Shannon, R. M.

    2016-07-01

    To study the strength and structure of the magnetic field in the Galactic Centre (GC), we measured Faraday rotation of the radio emission of pulsars which are seen towards the GC. Three of these pulsars have the largest rotation measures (RMs) observed in any Galactic object with the exception of Sgr A⋆. Their large dispersion measures, RMs and the large RM variation between these pulsars and other known objects in the GC implies that the pulsars lie in the GC and are not merely seen in projection towards the GC. The large RMs of these pulsars indicate large line-of-sight magnetic field components between ˜ 16 and 33 μG; combined with recent model predictions for the strength of the magnetic field in the GC this implies that the large-scale magnetic field has a very small inclination angle with respect to the plane of the sky (˜12°). Foreground objects like the Radio Arc or possibly an ablated, ionized halo around the molecular cloud G0.11-0.11 could contribute to the large RMs of two of the pulsars. If these pulsars lie behind the Radio Arc or G0.11-0.11 then this proves that low-scattering corridors with lengths ≳100 pc must exist in the GC. This also suggests that future, sensitive observations will be able to detect additional pulsars in the GC. Finally, we show that the GC component in our most accurate electron density model oversimplifies structure in the GC.

  20. The Binary Pulsar: Gravity Waves Exist.

    ERIC Educational Resources Information Center

    Will, Clifford

    1987-01-01

    Reviews the history of pulsars generally and the 1974 discovery of the binary pulsar by Joe Taylor and Russell Hulse specifically. Details the data collection and analysis used by Taylor and Hulse. Uses this discussion as support for Albert Einstein's theory of gravitational waves. (CW)

  1. The "Perseus Arm" Multibeam pulsar survey

    NASA Astrophysics Data System (ADS)

    Lyne, Andrew; Possenti, Andrea; Manchester, Dick; Kramer, Michael; Hobbs, George; McLaughlin, Maura; Burgay, Marta; D'Amico, Nichi; Camilo, Fernando; Stairs, Ingrid; Keith, Michael; Lorimer, Duncan Ross

    2007-04-01

    Given the extremely fruitful results of the completed Parkes Multibeam Pulsar Survey, Parkes Multibeam High Latitude Pulsar Survey, and Parkes Multibeam Intermediate Latitude Swinburne Survey, we have undertaken a new deep search for pulsars, sampling the galactic plane in the direction of the Perseus Arm at galactic coordinates 200 deg pulsar population and in particular improving the knowledge of the poorly known radial distribution of the pulsars in the outer regions of the Galaxy disk. Given the survey parameters and the sky coverage, this search will lead to the discovery of few tens of sources, with a good discovery rate (twice higher than for the two most recent large-scale searches performed at Parkes) and with a favorable ratio of millisecond over longer period pulsars. The requested range of Sidereal Time is complementary to other pulsar projects. We propose to continue this project, concluding the survey observations during this APR07 semester and timing the discovered pulsars.

  2. The "Perseus Arm" Multibeam pulsar survey

    NASA Astrophysics Data System (ADS)

    Lyne, Andrew; Possenti, Andrea; Manchester, Dick; Kramer, Michael; Hobbs, George; McLaughlin, Maura; Burgay, Marta; D'Amico, Nichi; Camilo, Fernando; Stairs, Ingrid; Lorimer, Duncan Ross

    2006-04-01

    Given the extremely fruitful results of the completed Parkes Multibeam Pulsar Survey, Parkes Multibeam High Latitude Pulsar Survey, and Parkes Multibeam Intermediate Latitude Swinburne Survey, we have undertaken a new deep search for pulsars, sampling the galactic plane in the direction of the Perseus Arm at galactic coordinates 200 deg pulsar population and in particular improving the knowledge of the poorly known radial distribution of the pulsars in the outer regions of the Galaxy disk. Given the survey parameters and the sky coverage, this search will lead to the discovery of few tens of sources, with a good discovery rate (twice higher than for the two most recent large-scale searches performed at Parkes) and with a favorable ratio of millisecond over longer period pulsars. The requested range of Sidereal Time is complementary to other pulsar projects. We propose to continue this project and start the timing observations of the discovered pulsars.

  3. The "Perseus Arm" Multibeam pulsar survey

    NASA Astrophysics Data System (ADS)

    Lyne, Andrew; Possenti, Andrea; Manchester, Dick; Kramer, Michael; Hobbs, George; McLaughlin, Maura; Burgay, Marta; D'Amico, Nichi; Camilo, Fernando; Stairs, Ingrid; Lorimer, Duncan Ross

    2006-10-01

    Given the extremely fruitful results of the completed Parkes Multibeam Pulsar Survey, Parkes Multibeam High Latitude Pulsar Survey, and Parkes Multibeam Intermediate Latitude Swinburne Survey, we have undertaken a new deep search for pulsars, sampling the galactic plane in the direction of the Perseus Arm at galactic coordinates 200 deg pulsar population and in particular improving the knowledge of the poorly known radial distribution of the pulsars in the outer regions of the Galaxy disk. Given the survey parameters and the sky coverage, this search will lead to the discovery of few tens of sources, with a good discovery rate (twice higher than for the two most recent large-scale searches performed at Parkes) and with a favorable ratio of millisecond over longer period pulsars. The requested range of Sidereal Time is complementary to other pulsar projects. We propose to continue this project and start the timing observations of the discovered pulsars.

  4. The "Perseus Arm" Multibeam pulsar survey

    NASA Astrophysics Data System (ADS)

    Lyne, Andrew; Possenti, Andrea; Manchester, Dick; Kramer, Michael; Hobbs, George; McLaughlin, Maura; Burgay, Marta; D'Amico, Nichi; Camilo, Fernando; Stairs, Ingrid; Keith, Michael; Lorimer, Duncan Ross

    2007-10-01

    Given the extremely fruitful results of the completed Parkes Multibeam Pulsar Survey, Parkes Multibeam High Latitude Pulsar Survey, and Parkes Multibeam Intermediate Latitude Swinburne Survey, we have undertaken a new deep search for pulsars, sampling the galactic plane in the direction of the Perseus Arm at galactic coordinates 200 deg pulsar population and in particular improving the knowledge of the poorly known radial distribution of the pulsars in the outer regions of the Galaxy disk. Given the survey parameters and the sky coverage, this search will lead to the discovery of few tens of sources, with a good discovery rate (twice higher than for the two most recent large-scale searches performed at Parkes) and with a favorable ratio of millisecond over longer period pulsars. The requested range of Sidereal Time is complementary to other pulsar projects. We propose to continue this project, concluding the survey observations during this OCT07 semester and timing the discovered pulsars.

  5. Neutron Stars and the Discovery of Pulsars.

    ERIC Educational Resources Information Center

    Greenstein, George

    1985-01-01

    Part one recounted the story of the discovery of pulsars and examined the Crab Nebula, supernovae, and neutron stars. This part (experts from the book "Frozen Star") shows how an understanding of the nature of pulsars allowed astronomers to tie these together. (JN)

  6. Pulsar prospects for the Cherenkov telescope array

    NASA Astrophysics Data System (ADS)

    Hassan, T.; Bonnefoy, S.; López, M.; Mirabal, N.; Barrio, J. A.; Contreras, J. L.; de los Reyes, R.; Wilhelmi, E. O.; Rudak, B.; CTA Consortium

    2012-12-01

    In the last few years, the Fermi-LAT telescope has discovered over a 100 pulsars at energies above 100 MeV, increasing the number of known gamma-ray pulsars by an order of magnitude. In parallel, imaging Cherenkov telescopes, such as MAGIC and VERITAS, have detected for the first time VHE pulsed gamma-rays from the Crab pulsar. Such detections have revealed that the Crab VHE spectrum follows a power-law up to at least 400 GeV, challenging most theoretical models, and opening wide possibilities of detecting more pulsars from the ground with the future Cherenkov Telescope Array (CTA). In this contribution, we study the capabilities of CTA for detecting Fermi pulsars. For this, we extrapolate their spectra with "Crab-like" power-law tails in the VHE range, as suggested by the latest MAGIC and VERITAS results.

  7. A radio pulsar spinning at 716 Hz.

    PubMed

    Hessels, Jason W T; Ransom, Scott M; Stairs, Ingrid H; Freire, Paulo C C; Kaspi, Victoria M; Camilo, Fernando

    2006-03-31

    We have discovered a 716-hertz eclipsing binary radio pulsar in the globular cluster Terzan 5 using the Green Bank Telescope. It is the fastest spinning neutron star found to date, breaking the 24-year record held by the 642-hertz pulsar B1937+21. The difficulty in detecting this pulsar, because of its very low flux density and high eclipse fraction (approximately 40% of the orbit), suggests that even faster spinning neutron stars exist. If the pulsar has a mass less than twice the mass of the Sun, then its radius must be constrained by the spin rate to be <16 kilometers. The short period of this pulsar also constrains models that suggest that gravitational radiation, through an r-mode (Rossby wave) instability, limits the maximum spin frequency of neutron stars.

  8. The Parkes Observatory Pulsar Data Archive

    NASA Astrophysics Data System (ADS)

    Hobbs, G.; Miller, D.; Manchester, R. N.; Dempsey, J.; Chapman, J. M.; Khoo, J.; Applegate, J.; Bailes, M.; Bhat, N. D. R.; Bridle, R.; Borg, A.; Brown, A.; Burnett, C.; Camilo, F.; Cattalini, C.; Chaudhary, A.; Chen, R.; D'Amico, N.; Kedziora-Chudczer, L.; Cornwell, T.; George, R.; Hampson, G.; Hepburn, M.; Jameson, A.; Keith, M.; Kelly, T.; Kosmynin, A.; Lenc, E.; Lorimer, D.; Love, C.; Lyne, A.; McIntyre, V.; Morrissey, J.; Pienaar, M.; Reynolds, J.; Ryder, G.; Sarkissian, J.; Stevenson, A.; Treloar, A.; van Straten, W.; Whiting, M.; Wilson, G.

    2011-08-01

    The Parkes pulsar data archive currently provides access to 144044 data files obtained from observations carried out at the Parkes observatory since the year 1991. Around 105 files are from surveys of the sky, the remainder are observations of 775 individual pulsars and their corresponding calibration signals. Survey observations are included from the Parkes 70cm and the Swinburne Intermediate Latitude surveys. Individual pulsar observations are included from young pulsar timing projects, the Parkes Pulsar Timing Array and from the PULSE@Parkes outreach program. The data files and access methods are compatible with Virtual Observatory protocols. This paper describes the data currently stored in the archive and presents ways in which these data can be searched and downloaded.

  9. Possible evidence that pulsars are quark stars

    SciTech Connect

    Xu Renxin

    2008-01-10

    It is a pity that the real state of matter in pulsar-like stars is still not determined confidently because of the uncertainty about cold matter at supranuclear density, even 40 years after the discovery of pulsar. Nuclear matter (related to neutron stars) is one of the speculations for the inner constitution of pulsars even from the Landau's time more than 70 years ago, but quark matter (related to quark stars) is an alternative due to the fact of asymptotic freedom of interaction between quarks as the standard model of particle physics develops since 1960s. Therefore, one has to focus on astrophysical observations in order to answer what the nature of pulsars is. In this presentation, I would like to summarize possible observational evidence/hints that pulsar-like stars could be quark stars, and to address achievable clear evidence for quark stars in the future experiments.

  10. A radio pulsar spinning at 716 Hz.

    PubMed

    Hessels, Jason W T; Ransom, Scott M; Stairs, Ingrid H; Freire, Paulo C C; Kaspi, Victoria M; Camilo, Fernando

    2006-03-31

    We have discovered a 716-hertz eclipsing binary radio pulsar in the globular cluster Terzan 5 using the Green Bank Telescope. It is the fastest spinning neutron star found to date, breaking the 24-year record held by the 642-hertz pulsar B1937+21. The difficulty in detecting this pulsar, because of its very low flux density and high eclipse fraction (approximately 40% of the orbit), suggests that even faster spinning neutron stars exist. If the pulsar has a mass less than twice the mass of the Sun, then its radius must be constrained by the spin rate to be <16 kilometers. The short period of this pulsar also constrains models that suggest that gravitational radiation, through an r-mode (Rossby wave) instability, limits the maximum spin frequency of neutron stars. PMID:16410486

  11. Towards solving the pulsar timing sampling problem

    NASA Astrophysics Data System (ADS)

    van Haasteren, Rutger; Ellis, Justin; Vallisneri, Michele; Nanograv Collaboration

    2016-03-01

    Bayesian data analysis of Pulsar Timing Array (PTA) has proved to be a computationally challenging problem, with scaling relations that are super-linear in both the number of pulsars and the number of model parameters. Thus far, our best models cannot be used when analyzing full (international) pulsar timing array datasets in the search for gravitational waves, and shortcuts always need to be made. A promising approach in the literature, based on Hamiltonian sampling techniques, has been shown to be infeasible in realistic datasets due to phase transition behavior of the likelihood. We have introduced a coordinate transformation that mitigates this phase transition behavior, and makes Hamiltonian sampling efficient. This makes a full (stochastic) gravitational-wave search in pulsar timing data feasible with our most up-to-date models. This method scales almost linearly with the number of pulsars. Supported by NASA through Einstein fellowship PF3-140116.

  12. Gravitational wave emission and spin-down of young pulsars

    SciTech Connect

    Alford, Mark G.; Schwenzer, Kai

    2014-01-20

    The rotation frequencies of young pulsars are systematically below their theoretical Kepler limit. r-modes have been suggested as a possible explanation for this observation. With the help of semi-analytic expressions that make it possible to assess the uncertainties of the r-mode scenario due to the impact of uncertainties in underlying microphysics, we perform a quantitative analysis of the spin-down and the emitted gravitational waves of young pulsars. We find that the frequency to which r-modes spin-down a young neutron star (NS) is surprisingly insensitive to both the microscopic details and the saturation amplitude. Comparing our result to astrophysical data, we show that for a range of sufficiently large saturation amplitudes r-modes provide a viable spin-down scenario and that all observed young pulsars are very likely already outside the r-mode instability region. Therefore, the most promising sources for gravitational wave detection are unobserved NSs associated with recent supernovae, and we find that advanced LIGO should be able to see several of them. Our analysis shows that despite the coupling of the spin-down and thermal evolution, a power-law spin-down with an effective braking index n {sub rm} ≤ 7 is realized. Because of this, the gravitational wave strain amplitude is completely independent of both the r-mode saturation amplitude and the microphysics and depends on the saturation mechanism only within some tens of percent. However, the gravitational wave frequency depends on the amplitude, and we provide the required expected timing parameter ranges to look for promising sources in future searches.

  13. X-ray and γ-ray studies of the millisecond pulsar and possible X-ray binary/radio pulsar transition object PSR J1723-2837

    SciTech Connect

    Bogdanov, Slavko; Esposito, Paolo; Crawford III, Fronefield; Possenti, Andrea; McLaughlin, Maura A.; Freire, Paulo

    2014-01-20

    We present X-ray observations of the 'redback' eclipsing radio millisecond pulsar (MSP) and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ∼2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar MSP binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and γ-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a γ-ray point source, due to the strong Galactic diffuse emission at its position a definitive association cannot be established. No statistically significant pulsations or modulation at the orbital period are detected. For a presumed detection, the implied γ-ray luminosity is ≲5% of its spin-down power. This indicates that PSR J1723-2837 is either one of the least efficient γ-ray producing MSPs or, if the detection is spurious, the γ-ray emission pattern is not directed toward us.

  14. Long-term radio observations of the intermittent pulsar B1931+24

    NASA Astrophysics Data System (ADS)

    Young, N. J.; Stappers, B. W.; Lyne, A. G.; Weltevrede, P.; Kramer, M.; Cognard, I.

    2013-03-01

    We present an analysis of approximately 13 yr of observations of the intermittent pulsar B1931+24 to further elucidate its behaviour. We find that while the source exhibits a wide range of nulling (˜4-39 d) and radio-emitting (˜1-19 d) time-scales, it cycles between its different emission phases over an average time-scale of approximately 38 d, which is remarkably stable over many years. On average, the neutron star is found to be radio-emitting for 26 ± 6 per cent of the time. No evidence is obtained to suggest that the pulsar undergoes any systematic, intrinsic variations in pulse intensity during the radio-emitting phases. In addition, we find no evidence for any correlation between the length of consecutive emission phases. An analysis of the rotational behaviour of the source shows that it consistently assumes the same spin-down rates, i.e. dot{ν }=-16 ± 1× 10^{-15} s-2 when emitting and dot{ν }=-10.8 ± 0.4× 10^{-15} s-2 when not emitting, over the entire observation span. Coupled with the stable switching time-scale, this implies that the pulsar retains a high degree of magnetospheric memory, and stability, in spite of comparatively rapid (˜ ms) dynamical plasma time-scales. While this provides further evidence to suggest that the behaviour of the neutron star is governed by magnetospheric-state switching, the underlying trigger mechanism remains illusive. This should be elucidated by future surveys with next generation telescopes such as LOFAR, MeerKAT and the SKA, which should detect similar sources and provide more clues to how their radio emission is regulated.

  15. Birth and Evolution of Isolated Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Kaspi, Victoria M.

    2006-05-01

    We investigate the birth and evolution of Galactic isolated radio pulsars. We begin by estimating their birth space velocity distribution from proper-motion measurements of Brisken and coworkers. We find no evidence for multimodality of the distribution and favor one in which the absolute one-dimensional velocity components are exponentially distributed and with a three-dimensional mean velocity of 380+40-60 km s-1. We then proceed with a Monte Carlo-based population synthesis, modeling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam surveys. We present a population model that appears generally consistent with the observations. Our results suggest that pulsars are born in the spiral arms, with a galactocentric radial distribution that is well described by the functional form proposed by Yusifov & Küçük, in which the pulsar surface density peaks at radius ~3 kpc. The birth spin period distribution extends to several hundred milliseconds, with no evidence of multimodality. Models that assume the radio luminosities of pulsars to be independent of the spin periods and period derivatives are inadequate, as they lead to the detection of too many old simulated pulsars in our simulations. Dithered radio luminosities proportional to the square root of the spin-down luminosity accommodate the observations well and provide a natural mechanism for the pulsars to dim uniformly as they approach the death line, avoiding an observed pileup on the latter. There is no evidence for significant torque decay (due to magnetic field decay or otherwise) over the lifetime of the pulsars as radio sources (~100 Myr). Finally, we estimate the pulsar birthrate and total number of pulsars in the Galaxy.

  16. EINSTEIN-HOME DISCOVERY OF 24 PULSARS IN THE PARKES MULTI-BEAM PULSAR SURVEY

    SciTech Connect

    Knispel, B.; Kim, H.; Allen, B.; Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H.; Machenschalk, B.; Eatough, R. P.; Keane, E. F.; Kramer, M.; Anderson, D.; Crawford, F.; Rastawicki, D.; Hammer, D.; Papa, M. A.; Siemens, X.; Lyne, A. G.; Miller, R. B.; Sarkissian, J.; and others

    2013-09-10

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of Almost-Equal-To 17, 000 CPU core years was provided by the distributed volunteer computing project Einstein-Home, which has a sustained computing power of about 1 PFlop s{sup -1}. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM ( Almost-Equal-To 420 pc cm{sup -3}). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data.

  17. Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

    NASA Astrophysics Data System (ADS)

    Knispel, B.; Eatough, R. P.; Kim, H.; Keane, E. F.; Allen, B.; Anderson, D.; Aulbert, C.; Bock, O.; Crawford, F.; Eggenstein, H.-B.; Fehrmann, H.; Hammer, D.; Kramer, M.; Lyne, A. G.; Machenschalk, B.; Miller, R. B.; Papa, M. A.; Rastawicki, D.; Sarkissian, J.; Siemens, X.; Stappers, B. W.

    2013-09-01

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of ≈17, 000 CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about 1 PFlop s-1. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM (≈420 pc cm-3). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data.

  18. Properties of the observed recycle radio pulsars

    NASA Astrophysics Data System (ADS)

    Johnston, Simon

    1994-04-01

    Recent searches for pulsars have been highly successful in discovering recycle and binary pulsars, and we now know of approximately 25 recycled pulsars in the Galaxy and approximately 30 in globular cluster systems. These pulsars fall into four classes; those with high-mass stellar companions, with neutron star companions, with low-mass companions, and those whose evolutionary history has been affected by a companion since lost. There are two pulsars known to have high-mass stellar companions. Both systems contain approximately 10 solar mass B-star companions and have high eccentricities (e approximately 0.85). PSR B1259-63 has a spin period of 47 ms and an orbital period in excess of three years. In constrast, PSR J0045-7319 has a spin period close to 1 s and an orbital period of only 50 days. These systems originated from a binary system containing two massive stars. The supernova explosion (SN) creates the pulsar and is also responsible for the observed high eccentricity. There are five pulsars thought to have neutron star companions. All these systems have orbital eccentricities in excess of 0.2, and they fall into two classes. The first class contain the pulsars formed after the first SN, and which have been spun-up to approximately 50 ms periods during the giant phase of their companion star. This also reduces the orbital peirod to 0.3 day and the second SN induces the high eccentricity. The pulsars observed in the second class were born after the second SN and thus have periods more typical of the bulk of pulsars (greater than 250 ms). The bulk of the recycled pulsars have low-mass (probably white dwarf) companions. In general, these pulsars have very fast spin-rates (the 'millisecond' pulsars) and large apparent ages. The observed eccentricities are extremely small (less than 10-5). These pulsars are re-born as millisecond pulsars after accreting matter and angular momentum from their companion stars in their giant phase. The orbit is circularized during

  19. STATISTICAL STUDIES OF GIANT PULSE EMISSION FROM THE CRAB PULSAR

    SciTech Connect

    Majid, Walid A.; Naudet, Charles J.; Lowe, Stephen T.; Kuiper, Thomas B. H.

    2011-11-01

    We have observed the Crab pulsar with the Deep Space Network Goldstone 70 m antenna at 1664 MHz during three observing epochs for a total of 4 hr. Our data analysis has detected more than 2500 giant pulses, with flux densities ranging from 0.1 kJy to 150 kJy and pulse widths from 125 ns (limited by our bandwidth) to as long as 100 {mu}s, with median power amplitudes and widths of 1 kJy and 2 {mu}s, respectively. The most energetic pulses in our sample have energy fluxes of approximately 100 kJy {mu}s. We have used this large sample to investigate a number of giant pulse emission properties in the Crab pulsar, including correlations among pulse flux density, width, energy flux, phase, and time of arrival. We present a consistent accounting of the probability distributions and threshold cuts in order to reduce pulse-width biases. The excellent sensitivity obtained has allowed us to probe further into the population of giant pulses. We find that a significant portion, no less than 50%, of the overall pulsed energy flux at our observing frequency is emitted in the form of giant pulses.

  20. Variations of P2 in subpulse drifting pulsars

    NASA Astrophysics Data System (ADS)

    Yuen, R.; Melrose, D. B.; Samsuddin, M. A.; Tu, Z. Y.; Han, X. H.

    2016-06-01

    We develop a model for subpulse separation period, P2, taking into account both the apparent motion of the visible point as a function of pulsar phase, ψ, and the possibility of abrupt jumps between different rotation states in non-corotating pulsar magnetospheres. We identify three frequencies: (i) the spin frequency of the star, (ii) the drift frequency of the magnetospheric plasma in the source region and (iii) the angular frequency of the visible point around its trajectory. We show how the last of these, which is neglected in traditional models by implicitly assuming the line of sight through the centre of the star, affects the interpretation of P2. We attribute the subpulse structure to emission from m antinodes distributed uniformly in azimuthal angle about the magnetic axis. We show that variations of P2 as a function of rotational phase or observing frequency arise naturally when the motion of the visible point is taken into account. We discuss possible application of our model in signifying overall field-line distortion at the emitting region. Abrupt changes in P2 can occur during state switching in the magnetosphere. We demonstrate that the unique value of P2 in each rotation state can be used, in principle, to relate the rotation state of the magnetospheres to subpulse drifting.

  1. GAMMA-RAY LIGHT CURVES FROM PULSAR MAGNETOSPHERES WITH FINITE CONDUCTIVITY

    SciTech Connect

    Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes

    2012-07-20

    We investigate the shapes of {gamma}-ray pulsar light curves using three-dimensional pulsar magnetosphere models of finite conductivity. These models, covering the entire spectrum of solutions between vacuum and force-free magnetospheres, for the first time afford mapping the GeV emission of more realistic, dissipative pulsar magnetospheres. To this end we generate model light curves following two different approaches: (1) We employ the emission patterns of the slot and outer gap models in the field geometries of magnetospheres with different conductivity {sigma}. (2) We define realistic trajectories of radiating particles in magnetospheres of different {sigma} and compute their Lorentz factor under the influence of magnetospheric electric fields and curvature radiation-reaction; with these at hand we then calculate the emitted radiation intensity. The light curves resulting from these prescriptions are quite sensitive to the value of {sigma}, especially in the second approach. While still not self-consistent, these results are a step forward in understanding the physics of pulsar {gamma}-radiation.

  2. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

    2016-10-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (i) the brightest observed events come from a broad distribution in distances; (ii) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

  3. FORMATION OF BLACK WIDOWS AND REDBACKS—TWO DISTINCT POPULATIONS OF ECLIPSING BINARY MILLISECOND PULSARS

    SciTech Connect

    Chen, Hai-Liang; Chen, Xuefei; Han, Zhanwen; Tauris, Thomas M.

    2013-09-20

    Eclipsing binary millisecond pulsars (MSPs; the so-called black widows and redbacks) can provide important information about accretion history, pulsar irradiation of their companion stars, and the evolutionary link between accreting X-ray pulsars and isolated MSPs. However, the formation of such systems is not well understood, nor the difference in progenitor evolution between the two populations of black widows and redbacks. Whereas both populations have orbital periods between 0.1 and 1.0 days, their companion masses differ by an order of magnitude. In this paper, we investigate the formation of these systems via the evolution of converging low-mass X-ray binaries by employing the MESA stellar evolution code. Our results confirm that one can explain the formation of most of these eclipsing binary MSPs using this scenario. More notably, we find that the determining factor for producing either black widows or redbacks is the efficiency of the irradiation process, such that the redbacks absorb a larger fraction of the emitted spin-down energy of the radio pulsar (resulting in more efficient mass loss via evaporation) compared to that of the black widow systems. We argue that geometric effects (beaming) are responsible for the strong bimodality of these two populations. Finally, we conclude that redback systems do not evolve into black widow systems with time.

  4. Pair Production and Gamma-Ray Emission in the Outer Magnetospheres of Rapidly Spinning Young Pulsars

    NASA Technical Reports Server (NTRS)

    Ruderman, Malvin; Chen, Kaiyou

    1997-01-01

    Electron-positron pair production and acceleration in the outer magnetosphere may be crucial for a young rapidly spinning canonical pulsar to be a strong Gamma-ray emitter. Collision between curvature radiated GeV photons and soft X-ray photons seems to be the only efficient pair production mechanism. For Crib-like pulsars, the magnetic field near the light cylinder is so strong, such that the synchrotron radiation of secondary pairs will be in the needed X-ray range. However, for majority of the known Gamma-ray pulsars, surface emitted X-rays seem to work as the matches and fuels for a gamma-ray generation fireball in the outer magnetosphere. The needed X-rays could come from thermal emission of a cooling neutron star or could be the heat generated by bombardment of the polar cap by energetic particles generated in the outer magnetosphere. With detection of more Gamma-ray pulsars, it is becoming evident that the neutron star's intrisic geometry (the inclination angle between the rotation and magnetic axes) and observational geometry (the viewing angle with respect to the rotation axis) are crucial to the understanding of varieties of observational properties exhibited by these pulsars. Inclination angles for many known high energy Gamma-ray pulsars appear to be large and the distribution seems to be consistent with random orientation. However, all of them except Geminga are pre-selected from known radio pulsars. The viewing angles are thus limited to be around the respective inclination angles for beamed radio emission, which may induce strong selection effect. The viewing angles as well as the inclination angles of PSR 1509-58 and PSB 0656+14 may be small such that most of the high energy Gamma-rays produced in the outer accelerators may not reach the observer's direction. The observed Gamma-rays below 5 MeV from this pulsar may be synchrotron radiation of secondary electron-positron pairs produced outside the accelerating regions.

  5. White dwarf pulsars as possible cosmic ray electron-positron factories

    SciTech Connect

    Kashiyama, Kazumi; Ioka, Kunihito; Kawanaka, Norita

    2011-01-15

    We suggest that white dwarf (WD) pulsars can compete with neutron star (NS) pulsars for producing the excesses of cosmic ray electrons and positrons (e{sup {+-}}) observed by the PAMELA, ATIC/PPB-BETS, Fermi, and H.E.S.S. experiments. A merger of two WDs leads to a rapidly spinning WD with a rotational energy ({approx}10{sup 50} erg) comparable to the NS case. The birth rate ({approx}10{sup -2}-10{sup -3}/yr/galaxy) is also similar, providing the right energy budget for the cosmic ray e{sup {+-}}. Applying the NS theory, we suggest that the WD pulsars can in principle produce e{sup {+-}} up to {approx}10 TeV. In contrast to the NS model, the adiabatic and radiative energy losses of e{sup {+-}} are negligible since their injection continues after the expansion of the pulsar wind nebula, and hence it is enough that a fraction {approx}1% of WDs are magnetized ({approx}10{sup 7}-10{sup 9} G) as observed. The long activity also increases the number of nearby sources ({approx}100), which reduces the Poisson fluctuation in the flux. The WD pulsars could dominate the quickly cooling e{sup {+-}} above TeV energy as a second spectral bump or even surpass the NS pulsars in the observing energy range {approx}10 GeV-1 TeV, providing a background for the dark matter signals and a nice target for the future AMS-02, CALET, and CTA experiment.

  6. Multi-Zone Modeling of the Pulsar Win Nebula HESS J1825-137

    SciTech Connect

    Van Etten, Adam; Romani, Roger W.; /Stanford U., Phys. Dept.

    2011-11-08

    The pulsar wind nebula associated with PSR J1826-1334, HESS J1825-137, is a bright very high energy source with an angular extent of {approx} 1{sup o} 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 3-D time-dependent spectral energy distribution modeling, with emphasis on the spatial variations within HESS J1825-137. The multi-wavelength data places 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(t){sup 1/2}. Detection of 10 TeV flux {approx} 80 pc from the pulsar requires rapid diffusion of high energy particles with {tau}{sub esc} {approx} 90 (R/10 pc){sup 2}(E{sub e}/100TeV){sup -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 {approx} 1{sup o} from the pulsar, in good agreement with the recently discovered LAT source centered 0.5{sup o} southwest of PSR J1826-1334 with extension 0.6 {+-} 0.1{sup o}.

  7. Particles generation and cooling of pulsar magnetosphere

    NASA Astrophysics Data System (ADS)

    Kryvdyk, Volodymyr

    2016-07-01

    The generation of secondary particles (neutrinos, neutrons, electrons, protons, mesons) and gamma-ray photons because of nuclear interactions in magnetospheres of pulsars and magnetars are considered. By means of the nuclear interactions, the primarily accelerated electrons and protons in the pulsar magnetosphere will be generated secondary particles and photons, which will also generate particles and gamma-ray photons by cascading interactions. Namely from these particles and photons, which arise because of multiple interactions, and will consist of the pulsar magnetosphere. It is important that in pulsar magnetosphere will generate the powerful flux of neutral particles (neutrons) and a neutrino that do not interact with the magnetic field and are free to go out with her, bringing out energy and cooling magnetosphere. So, we obtain a powerful new channel cooling pulsar magnetosphere. This is a new result, which shows that cooling of pulsar and magnetars is not only a result of the processes generating neutrinos in the inner core, but also due to the generation of neutrino and neutrons in the pulsar magnetosphere and subsequently their exit in the interstellar environment.

  8. Torque Enhancement, Spin Equilibrium, and Jet Power from Disk-Induced Opening of Pulsar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Parfrey, Kyle; Spitkovsky, Anatoly; Beloborodov, Andrei M.

    2016-05-01

    The interaction of a rotating star’s magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk-magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-detection of frequency increases during outbursts of SAX J1808.4-3658 and XTE J1814-338, and may be generally responsible for preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated by the surrounding environment, the resulting jet can satisfy the power requirements of the highly relativistic outflows from Cir X-1 and Sco X-1. In this framework, the jet power scales relatively weakly with accretion rate, {L}{{j}}\\propto {\\dot{M}}4/7, and would be suppressed at high accretion rates only if the stellar magnetic moment is sufficiently low.

  9. Torque Enhancement, Spin Equilibrium, and Jet Power from Disk-Induced Opening of Pulsar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Parfrey, Kyle; Spitkovsky, Anatoly; Beloborodov, Andrei M.

    2016-05-01

    The interaction of a rotating star’s magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk–magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-detection of frequency increases during outbursts of SAX J1808.4-3658 and XTE J1814-338, and may be generally responsible for preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated by the surrounding environment, the resulting jet can satisfy the power requirements of the highly relativistic outflows from Cir X-1 and Sco X-1. In this framework, the jet power scales relatively weakly with accretion rate, {L}{{j}}\\propto {\\dot{M}}4/7, and would be suppressed at high accretion rates only if the stellar magnetic moment is sufficiently low.

  10. Arecibo Pulsar and Transient Surveys Using ALFA

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.

    2008-02-01

    A large scale survey for pulsars and transients is being conducted at the Arecibo Observatory using the Arecibo L-band Feed Array (ALFA). Data acquisition so far has been with correlation spectrometers that analyze a 0.1 GHz bandwidth at 1.4 GHz. The 256 frequency channels limit dispersion smearing to 1.2 ms at DMmax = 103 pc cm-3 while the sampling interval of 64 μs equals the dispersion smearing at DM~54 pc cm-3, providing high sensitivity to millisecond pulsars with standard periods out to implied distances of several kpc at low Galactic latitudes. In early 2008, we will use a new set of polyphase filter bank systems that provide the same time and frequency resolutions but over ALFA's full 0.3 GHz bandwidth. Currently the survey covers sky positions within 5° of the Galactic plane that are reachable with Arecibo. Preliminary results are given for some of the discoveries made so far, which include millisecond pulsars, a relativistic binary pulsar, a likely counterpart of a Compton GRO/EGRET gamma-ray source, and transient pulsars (including `RRATs''). We discuss the methodology of the survey, which includes archival of raw survey data at the Cornell Center for Advanced Computing and processing at distributed sites. The survey and follow up observations, which include timing observations, multiwavelength searches for orbital companions in the case of binary pulsars, etc. are organized through the Pulsar-ALFA (PALFA) Consortium. We expect the Galactic plane survey to continue until at least 2010, most likely involving multiple passes on each sky position to optimize detection of variable sources. The ALFA system will also be used to survey intermediate Galactic latitudes for millisecond pulsars, relativistic binaries with large systemic velocities, and runaway pulsars that will escape the Galaxy.

  11. X-Ray Emission from the Be Star/Pulsar System PSR 1259-63

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1997-01-01

    The collaboration involved researchers at Columbia University, ISAS-Tokyo, Princeton University for the data analysis part, and UC Berkeley for the theoretical analysis. Four different ASCA observations of the Be star/pulsar system PSR 1259-63 were successfully carried out in 1994. Data for the first three observations near periastron were analyzed first, and the analysis was completed in 1995 and a summary paper was published by the Astrophysical Journal. A comprehensive theoretical analysis of the X-ray data together with the results of the simultaneous GRO gamma-ray observational campaign was carried out and the results published in a series of papers. We find that the ASCA results can strongly constrain outflow models from the Be star companion of PSR 1259-63 as well as the radiation mechanisms as the pulsar orbits around the periastron region. The X-ray data suggest a misalignment between the pulsar orbital plane and the Be star outflow equatorial plane. We find that shock-driven emission from synchrotron radiating electron/positrons of the pulsar wind is in agreement with all data obtained. For the first time in a plerionic system, particle acceleration can be shown to be more efficient and fast than inverse Compton and synchrotron radiation cooling of typical timescales near 10(exp 2) - 10(exp 3) sec. These results are of great importance for the theory of particle acceleration in transverse shocks. A second theoretical paper on the study of the relativistic pulsar wind and shock acceleration mechanisms is being completed.

  12. Classical Accreting Pulsars with NICER

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.

    2014-01-01

    Soft excesses are very common center dot Lx > 1038 erg/s - reprocessing by optically thick material at the inner edge of the accretion disk center dot Lx < 1036 erg/s - photoionized or collisionally heated diffuse gas or thermal emission from the NS surface center dot Lx 1037 erg/s - either or both types of emission center dot NICER observations of soft excesses in bright X-ray pulsars combined with reflection modeling will constrain the ionization state, metalicity and dynamics of the inner edge of the magnetically truncated accretion disk Reflection models of an accretion disk for a hard power law - Strong soft excess below 3 keV from hot X-ray heated disk - For weakly ionized case: strong recombination lines - Are we seeing changes in the disk ionization in 4U1626-26? 13 years of weekly monitoring with RXTE PCA center dot Revealed an unexpectedly large population of Be/X-ray binaries compared to the Milky Way center dot Plotted luminosities are typical of "normal" outbursts (once per orbit) center dot The SMC provides an excellent opportunity to study a homogenous population of HMXBs with low interstellar absorption for accretion disk studies. Monitoring with NICER will enable studies of accretion disk physics in X-ray pulsars center dot The SMC provides a potential homogeneous low-absorption population for this study center dot NICER monitoring and TOO observations will also provide measurements of spinfrequencies, QPOs, pulsed fluxes, and energy spectra.

  13. Radio-Quiet Pulsars and Point Sources in Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Helfand, David

    2002-04-01

    Since Baade and Zwicky made their prescient remark identifying the central blue star in the Crab Nebula as a neutron star, this pulsar's period has increased by 0.9 msec, turning 10^48 ergs of rotational kinetic energy into a relativistic wind that has been deposited in its surroundings. This makes the compact remnant of the supernova of 1054 AD highly conspicuous. It also makes this remnant highly anomalous. Nowhere else in the Galaxy does such a luminous young pulsar exists, despite the fact that at least half a dozen core-collapse supernovae have occurred since the Crab's birth. Indeed, the newly discovered central object in Cas A is four orders of magnitude less luminous in the X-ray band. While the Chandra and XMM-Newton Observatories are discovering an increasing number of Crab-like synchrotron nebulae (albeit, far less luminous than the prototype), they are also revealing X-ray point sources inside supernova remnants that lack detectable radio pulses and show no evidence of a relativistic outflow to power a surrounding nebula. I will provide an inventory of these objects, discuss whether or not truly radio-silent young neutron stars exist, and speculate on the emission mechanisms and power sources which make such objects shine. I will conclude with a commentary on the implications of this population for the distributions of pulsar birth parameters such as spin period, magnetic field strength, and space velocity, as well as offer a glimpse of what future observations might reveal about the demographics of core-collapse remnants.

  14. Parkes Observations of Globular Cluster Pulsars

    NASA Astrophysics Data System (ADS)

    Bailes, M.; Zhu, J.; Richter, S.

    2005-07-01

    Follow-up observations of pulsars from the Swinburne intermediate latitude survey with the Parkes radio telescope have caused us to question the association of PSR B1718-19 with the globular cluster NGC 6342 given the proximity of PSR J1721-1939 to the cluster. We have also found that the millisecond pulsar near the core of NGC 6624 has a large period second derivative, which would change the sign of the first derivative in about 6000 years. This is consistent with the pulsar experiencing a large gravitational perturbation from the cluster core.

  15. Limits to the Stability of Pulsar Time

    NASA Technical Reports Server (NTRS)

    Petit, Gerard

    1996-01-01

    The regularity of the rotation rate of millisecond pulsars is the underlying hypothesis for using these neutron stars as 'celestial clocks'. Given their remote location in our galaxy and to our lack of precise knowledge on the galactic environment, a number of phenomena effect the apparent rotation rate observed on Earth. This paper reviews these phenomena and estimates the order of magnitude of their effect. It concludes that an ensemble pulsar time based on a number of selected millisecond pulsars should have a fractional frequency stability close to 2 x 10(sup -15) for an averaging time of a few years.

  16. Post-Outburst Observations of the Magnetically Active Pulsar J1846-0258: A New Braking Index, Increased Timing Noise, and Radiative Recovery

    NASA Technical Reports Server (NTRS)

    Livingstone, Margaret A.; Ng, C.-Y.; Kaspi, Victoria M.; Gavriil, Fotis P.; Gotthelf, E. V.

    2010-01-01

    The approx.800yr-old pulsar J1846-0258 is a unique transition object between rotation-powered pulsars and magnetars: though behaving like a rotation-powered pulsar most of the time, in 2006 it exhibited a distinctly magnetar-like outburst accompanied by a large glitch. Here we present X-ray timing observations taken with the Rossi X-ray Timing Explorer over a 2.2-yr period after the X-ray outburst and glitch had recovered. We observe that the braking index of the pulsar, previously measured to be n = 2.65+/-0.01, is now n = 2.16+/-0.13, a decrease of 18+/-5%. We also note a persistent increase in the timing noise relative to the pre-outburst level. Despite the timing changes, a 2009 Chandra X-ray Observatory observation shows that the X-ray flux and spectrum of the pulsar and its wind nebula are consistent with the quiescent levels observed in 2000. Subject headings: pulsars: general pulsars: individual (PSR J1846-0258) supernovae: individual (Kes 75 X-rays: stars)

  17. On the magnetic fields of Be/X-ray pulsars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Ikhsanov, N. R.; Mereghetti, S.

    2015-12-01

    We explore the possibility of explaining the properties of the Be/X-ray pulsars observed in the Small Magellanic Cloud (SMC) within the magnetic levitation accretion scenario. This implies that their X-ray emission is powered by a wind-fed accretion on to a neutron star (NS) which captures matter from a magnetized stellar wind. The NS in this case is accreting matter from a non-Keplerian magnetically levitating disc which is surrounding its magnetosphere. This allows us to explain the observed periods of the pulsars in terms of spin equilibrium without the need of invoking dipole magnetic fields outside the usual range ˜1011-1013 G inferred from cyclotron features of Galactic high-mass X-ray binaries. We find that the equilibrium period of a NS, under certain conditions, depends strongly on the magnetization of the stellar wind of its massive companion and, correspondingly, on the magnetic field of the massive companion itself. This may help to explain why similar NSs in binaries with similar properties rotate with different periods yielding a large scatter of periods of the accretion-powered pulsar observed in SMC and our galaxy.

  18. The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays

    NASA Astrophysics Data System (ADS)

    Serafimovich, N. I.; Shibanov, Yu. A.; Lundqvist, P.; Sollerman, J.

    2004-10-01

    The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations with ESO/VLT/FORS1 and analysis of HST/WFPC2 archival data were done. We show that the HST and VLT spectral data for the pulsar have ⪆50% nebular contamination and that this is the reason for the above-mentioned difference. The broadband HST spectrum for the range 3300-8000 Å is clearly nonthermal and has a negative spectral index, Fν ∝ ν-α with αν = 1.07+0.20-0.19. This is different from the almost flat spectrum of the Crab pulsar, and also steeper than for the previously published broadband photometry of PSR B0540-69.3. We have also studied the spatial variations of the brightness and spectral index of the Pulsar Wind Nebula (PWN) around the pulsar, and find no significant spectral index variation over the PWN. The HST data show a clear asymmetry of the surface brightness distribution along the major axis of the torus-like structure of the PWN with respect to the pulsar position, also seen in Chandra/HRC X-ray images. This is different from the Crab PWN and likely linked to the asymmetry of the surrounding SN ejecta. The HST/WFPC2 archival data have an epoch separation of 4 years, and this allows us to estimate the proper motion of the pulsar. We find a motion of 4.9±2.3 mas yr-1 (corresponding to a transverse velocity of 1190±560 km s-1) along the southern jet of the PWN. If this is confirmed at a higher significance level by future observations, this makes PSR B0540-69.3 the third pulsar with a proper motion aligned with the jet axis of its PWN, which poses constraints on pulsar kick models. To establish the multiwavelength spectrum of the pulsar and its PWN, we have included recent Chandra X-ray data, and

  19. Astronomers Discover Fastest-Spinning Pulsar

    NASA Astrophysics Data System (ADS)

    2006-01-01

    Astronomers using the National Science Foundation's Robert C. Byrd Green Bank Telescope have discovered the fastest-spinning neutron star ever found, a 20-mile-diameter superdense pulsar whirling faster than the blades of a kitchen blender. Their work yields important new information about the nature of one of the most exotic forms of matter known in the Universe. Pulsar Graphic Pulsars Are Spinning Neutron Stars CREDIT: Bill Saxton, NRAO/AUI/NSF (Click on image for larger version) "We believe that the matter in neutron stars is denser than an atomic nucleus, but it is unclear by how much. Our observations of such a rapidly rotating star set a hard upper limit on its size, and hence on how dense the star can be.," said Jason Hessels, a graduate student at McGill University in Montreal. Hessels and his colleagues presented their findings to the American Astronomical Society's meeting in Washington, DC. Pulsars are spinning neutron stars that sling "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is left after a massive star explodes at the end of its "normal" life. With no nuclear fuel left to produce energy to offset the stellar remnant's weight, its material is compressed to extreme densities. The pressure squeezes together most of its protons and electrons to form neutrons; hence, the name "neutron star." "Neutron stars are incredible laboratories for learning about the physics of the fundamental particles of nature, and this pulsar has given us an important new limit," explained Scott Ransom, an astronomer at the National Radio Astronomy Observatory and one of Hessels' collaborators on this work. The scientists discovered the pulsar, named PSR J1748-2446ad, in a globular cluster of stars called Terzan 5, located some 28,000 light-years from Earth in the constellation Sagittarius. The newly-discovered pulsar is spinning 716 times per second, or at 716 Hertz (Hz), readily beating the previous record of 642 Hz from a pulsar

  20. Multi-wavelength studies of pulsars and their companions

    NASA Astrophysics Data System (ADS)

    Antoniadis, John Ioannis

    2013-09-01

    Neutron stars are the degenerate relic cores of massive stars formed in the aftermath of a supernova explosion. Matter in their centes is believed to be condensed at densities as high as ten times that found in atomic nuclei. Thus, observational access to their properties provides the means to study the behavior of physical laws in extreme conditions, beyond the reach of terrestrial experiments. Rapidly rotating, highly magnetized neutron stars emit a narrow intense beam of radio emission from their magnetospheric poles. When this pulse happens to intersect our line of sight, it gives rise to the pulsar phenomenon. Regular radio-timing of pulse arrival times on earth, results in some of the most precise measurements in astrophysics. This thesis deals with the study of binary millisecond pulsars with white dwarf companions and is divided in 7 Chapters. Chapters 1 & 2 give a brief introduction to neutron stars, pulsars, and binary pulsars. Chapter 3 describes spectroscopic and optical observations of the low mass white dwarf companion to PSR J1909-3744. For this system, radio observations have yielded a precise mass measurement as well as distance information. Combined with the optical data, these provide the first observational test for theoretical white-dwarf cooling models and spectra. The latter, if reliable, can be used to infer theory-independent masses for similar systems. In Chapter 4, I discuss the measurement of the component masses in the short-orbit PSR J1738+0333 system based on spectroscopy of its white-dwarf companion. This system is particularly important for understanding the physics of pulsar recycling and binary evolution. Moreover, combined with the measurement of the orbital decay from radio-timing, the masses pose the most stringent constraints on Scalar-Tensor gravity. Chapter 5 describes radio and optical observations of PSR J0348+0432, a compact pulsar-white dwarf binary discovered recently with the 100-m Green-Bank Radio Telescope. Spectral

  1. Fastest Pulsar Speeding Out of Galaxy, Astronomers Discover

    NASA Astrophysics Data System (ADS)

    2005-08-01

    A speeding, superdense neutron star somehow got a powerful "kick" that is propelling it completely out of our Milky Way Galaxy into the cold vastness of intergalactic space. Its discovery is puzzling astronomers who used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope to directly measure the fastest speed yet found in a neutron star. Pulsar's Path Across Sky Over about 2.5 million years, Pulsar B1508+55 has moved across about a third of the night sky as seen from Earth. CREDIT: Bill Saxton, NRAO/AUI/NSF (Click on image for larger version 67 KB) The neutron star is the remnant of a massive star born in the constellation Cygnus that exploded about two and a half million years ago in a titanic explosion known as a supernova. Ultra-precise VLBA measurements of its distance and motion show that it is on course to inevitably leave our Galaxy. "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding," said Shami Chatterjee, of the National Radio Astronomy Observatory (NRAO) and the Harvard-Smithsonian Center for Astrophysics. "This discovery is very difficult for the latest models of supernova core collapse to explain," he added. Chatterjee and his colleagues used the VLBA to study the pulsar B1508+55, about 7700 light-years from Earth. With the ultrasharp radio "vision" of the continent-wide VLBA, they were able to precisely measure both the distance and the speed of the pulsar, a spinning neutron star emitting powerful beams of radio waves. Plotting its motion backward pointed to a birthplace among groups of giant stars in the constellation Cygnus -- stars so massive that they inevitably explode as supernovae. "This is the first direct measurement of a neutron star's speed that exceeds 1,000 kilometers per second," said Walter Brisken, an NRAO astronomer. "Most earlier estimates of neutron-star speeds depended on educated

  2. XMM-Newton observations of young and energetic pulsar J2022+3842

    SciTech Connect

    Arumugasamy, P.; Pavlov, G. G.; Kargaltsev, O.

    2014-08-01

    We report on XMM-Newton EPIC observations of the young pulsar J2022+3842, with a characteristic age of 8.9 kyr. We detected X-ray pulsations and found the pulsation period P ≈ 48.6 ms, and its derivative P-dot ≈8.6×10{sup −14}, which is two times larger than previously reported values. The pulsar exhibits two very narrow (FWHM ∼1.2 ms) X-ray pulses each rotation, separated by ≈0.48 of the period, with a pulsed fraction of ≈0.8. Using the correct values of P and P-dot , we calculate the pulsar's spin-down power E-dot =3.0×10{sup 37} erg s{sup –1} and magnetic field B = 2.1 × 10{sup 12} G. The pulsar spectrum is well modeled with a hard power-law (PL) model (photon index Γ = 0.9 ± 0.1, hydrogen column density n{sub H} = (2.3 ± 0.3) × 10{sup 22} cm{sup –2}). We detect a weak off-pulse emission, which can be modeled with a softer PL (Γ ≈ 1.7 ± 0.7), that is poorly constrained because of contamination in the EPIC-pn timing mode data. The pulsar's X-ray efficiency in the 0.5-8 keV energy band, η{sub PSR}=L{sub PSR}/ E-dot =2×10{sup −4}(D/10 kpc){sup 2}, is similar to those of other pulsars. The XMM-Newton observation did not detect extended emission around the pulsar. Our re-analysis of Chandra X-ray Observatory archival data shows a hard, Γ ≈ 0.9 ± 0.5, spectrum and a low efficiency, η{sub PWN} ∼ 2 × 10{sup –5}(D/10 kpc){sup 2}, for the compact pulsar wind nebula, unresolved in the XMM-Newton images.

  3. Discovery of an Energetic Pulsar Associated with SNR G76.9+1.0

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Zaven; Gotthelf, E. V.; Ransom, S. M.; Safi-Harb, S.; Kothes, R.; Landecker, T. L.

    2012-01-01

    We report the discovery of PSR J2022-<-3842, a 24 ms radio and X-ray pulsar in the supernova remnant G76.9+i.0, in observations with the Chandra X-ray telescope, the Robert C. Byrd Green Bank Radio Telescope, and the Rossi X-ray Timing Explorer (RXTE). The pulsar's spin-down rate implies a rotation-powered luminosity E = 1.2 X 10(exp 38) erg/s, a surface dipole magnetic field strength B(sub S), = 1.0 X 10(exp 12) G, and a characteristic age of 8.9 kyr. PSR J2022+3842 is thus the second-most energetic Galactic pulsar known, after the Crab, as well as the most rapidly-rotating young, radio-bright pulsar known. The radio pulsations are highly dispersed and broadened by interstellar scattering, and we find that a large (delta f/f approximates 1.9 x 10(exp -6)) spin glitch must have occurred between our discovery and confirmation observations. The X-ray pulses are narrow (0.06 cycles FWHM) and visible up to 20 keV, consistent with magnetospheric emission from a rotation-powered pulsar. The Chandra X-ray image identifies the pulsar with a hard, unresolved source at the midpoint of the double-lobed radio morphology of G76.9+ 1.0 and embedded within faint, compact X-ray nebulosity. The spatial relationship of the X-ray and radio emissions is remarkably similar to extended structure seen around the Vela pulsar. The combined Chandra and RXTE pulsar spectrum is well-fitted by an absorbed power-law model with column density N(sub H) = (1.7 +/- 0.3) x 10(exp 22) / sq cm and photon index Gamma = 1.0 +/- 0.2; it implies that the Chandra point-source flux is virtually 100% pulsed. For a distance of 10 kpc, the X-ray luminosity of PSR J2022+3842 is L(sub x){2-1O keV) = 7.0 x 10(exp 33) erg/s. Despite being extraordinarily energetic, PSR J2022+3842 lacks a bright X-ray wind nebula and has an unusually low conversion efficiency of spin-down power to X-ray luminosity, Lx/E = 5.9 X 10(exp-5).

  4. The attenuation of gamma-ray emission in strongly-magnetized pulsars

    NASA Technical Reports Server (NTRS)

    Baring, Matthew G.; Harding, Alice K.; Gonthier, Peter L.

    1997-01-01

    Gamma rays from pulsars can be efficiently attenuated in their magnetospheres via the mechanism of single photon pair production and the exotic quantum electrodynamics (QED) process of photon splitting. The modeling of strongly magnetized gamma ray pulsars focusing on the escape or attenuation of photons emitted near the pole at the neutron star surface in dipole fields in a Schwarzschild metric is considered. It was found that pair production and splitting totally inhibit emission above a value of between 10 and 30 MeV in PSR 1509-58 whose surface field is inferred as being high. The principle predictions of the attenuation analysis are reviewed and the observational diagnostic capabilities of the model are considered. The diagnostics include the energy of the gamma ray turnover and the spectral polarization, which constrain the estimated polar cap size and field strength and can determine the relative strength of splitting and pair creation.

  5. FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE VELA PULSAR

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Bartelt, J.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bogart, J. R.; Atwood, W. B.; Bagagli, R.; Baldini, L.; Bellardi, F.; Bellazzini, R.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bisello, D.; Baughman, B. M. E-mail: massimiliano.razzano@pi.infn.it

    2009-05-10

    The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new {gamma}-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile, with some 32,400 pulsed photons at E {>=} 0.03 GeV, shows new features, including pulse structure as fine as 0.3 ms and a distinct third peak, which shifts in phase with energy. We examine the high-energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power-law index of {gamma} = 1.51{sup +0.05} {sub -0.04} with an exponential cutoff at E{sub c} = 2.9 {+-} 0.1 GeV. Spectral fits with generalized cutoffs of the form e{sup -(E/E{sub c}){sup b}} require b {<=} 1, which is inconsistent with magnetic pair attenuation, and thus favor outer-magnetosphere emission models. Finally, we report on upper limits to any unpulsed component, as might be associated with a surrounding pulsar wind nebula.

  6. Piccard: Pulsar timing data analysis package

    NASA Astrophysics Data System (ADS)

    van Haasteren, Rutger

    2016-10-01

    Piccard is a Bayesian-inference pipeline for Pulsar Timing Array (PTA) data and interacts with Tempo2 (ascl:1210.015) through libstempo. The code is use mainly for single-pulsar analysis and gravitational-wave detection purposes of full Pulsar Timing Array datasets. Modeling of the data can include correlated signals per frequency or modeled spectrum, with uniform, dipolar, quadrupolar, or anisotropic correlations; multiple error bars and EFACs per pulsar; and white and red noise. Timing models can be numerically included, either by using the design matrix (linear timing model), or by calling libstempo for the full non-linear timing model. Many types of samplers are included. For common-mode mitigation, the signals can be reconstructed mitigating arbitrary signals simultaneously.

  7. Testing Gravity Using Pulsar Scintillation Measurements

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Nishizawa, Atsushi; Pen, Ue-Li

    2016-03-01

    We propose to use pulsar scintillation measurements to test predictions of alternative theories of gravity. Comparing to single-path pulsar timing measurements, the scintillation measurements can achieve a factor of 104 ~105 improvement in timing accuracy, due to the effect of multi-path interference. The self-noise from pulsar also does not affect the interference pattern, where the data acquisition timescale is 103 seconds instead of years. Therefore it has unique advantages in measuring gravitational effect or other mechanisms (at mHz and above frequencies) on light propagation. We illustrate its application in constraining scalar gravitational-wave background and measuring gravitational-wave speed, in which cases the sensitivities are greatly improved with respect to previous limits. We expect much broader applications in testing gravity with existing and future pulsar scintillation observations.

  8. Quasars, pulsars, black holes and HEAO's

    NASA Technical Reports Server (NTRS)

    Doolitte, R. F.; Moritz, K.; Whilden, R. D. C.

    1974-01-01

    Astronomical surveys are discussed by large X-ray, gamma ray, and cosmic ray instruments carried onboard high-energy astronomy observatories. Quasars, pulsars, black holes, and the ultimate benefits of the new astronomy are briefly discussed.

  9. Interactive Database of Pulsar Flux Density Measurements

    NASA Astrophysics Data System (ADS)

    Koralewska, O.; Krzeszowski, K.; Kijak, J.; Lewandowski, W.

    2012-12-01

    The number of astronomical observations is steadily growing, giving rise to the need of cataloguing the obtained results. There are a lot of databases, created to store different types of data and serve a variety of purposes, e. g. databases providing basic data for astronomical objects (SIMBAD Astronomical Database), databases devoted to one type of astronomical object (ATNF Pulsar Database) or to a set of values of the specific parameter (Lorimer 1995 - database of flux density measurements for 280 pulsars on the frequencies up to 1606 MHz), etc. We found that creating an online database of pulsar flux measurements, provided with facilities for plotting diagrams and histograms, calculating mean values for a chosen set of data, filtering parameter values and adding new measurements by the registered users, could be useful in further studies on pulsar spectra.

  10. Outlook for Detecting Gravitational Waves with Pulsars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-04-01

    Though the recent discovery of GW150914 is a thrilling success in the field of gravitational-wave astronomy, LIGO is only one tool the scientific community is using to hunt for these elusive signals. After 10 years of unsuccessful searching, how likely is it that pulsar-timing-array projects will make their own first detection soon?Frequency ranges for gravitational waves produced by different astrophysical sources. Pulsar timing arrays such as the EPTA and IPTA are used to detect low-frequency gravitational waves generated by the stochastic background and supermassive black hole binaries. [Christopher Moore, Robert Cole and Christopher Berry]Supermassive BackgroundGround-based laser interferometers like LIGO are ideal for probing ripples in space-time caused by the merger of stellar-mass black holes; these mergers cause chirps in the frequency range of tens to thousands of hertz. But how do we pick up the extremely low-frequency, nanohertz background signal caused by the orbits of pairs of supermassive black holes? For that, we need pulsar timing arrays.Pulsar timing arrays are sets of pulsars whose signals are analyzed to look for correlations in the pulse arrival time. As the space-time between us and a pulsar is stretched and then compressed by a passing gravitational wave, the pulsars pulses should arrive a little late and then a little early. Comparing these timing residuals in an array of pulsars could theoretically allow for the detection of the gravitational waves causing them.Globally, there are currently four pulsar timing array projects actively searching for this signal, with a fifth planned for the future. Now a team of scientists led by Stephen Taylor (NASA-JPL/Caltech) has estimated the likelihood that these projects will successfully detect gravitational waves in the future.Probability for SuccessExpected detection probability of the gravitational-wave background as a function of observing time, for five different pulsar timing arrays. Optimistic

  11. The origin of the Guitar pulsar

    NASA Astrophysics Data System (ADS)

    Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M.

    2009-11-01

    Among a sample of 140 OB associations and clusters, we want to identify probable parent associations for the Guitar pulsar (PSR B2224+65), which would then also constrain its age. For this purpose, we are using an Euler-Cauchy technique, treating the vertical component of the Galactic potential to calculate the trajectories of the pulsar and each association into the past. To include errors, we use Monte Carlo simulations varying the initial parameters within their error intervals. The whole range of possible pulsar radial velocities is taken into account during the simulations. We find that the Guitar pulsar most probably originated from the Cygnus OB3 association ~0.8Myr ago, inferring a current radial velocity of vr ~ -30kms-1, consistent with the inclination of its bow shock.

  12. Gamma radiation from pulsar magnetospheric gaps

    NASA Technical Reports Server (NTRS)

    Chiang, James; Romani, Roger W.

    1992-01-01

    We investigate the production of gamma rays in two pulsar emission models: the 'polar cap' model and the 'outer cap' model. For the former, we have performed detailed simulations of energetic electrons flowing in the vacuum dipole open field line region. In the outer gap case, we generate light curves for various magnetosphere geometries. Using data from radio and optical observations, we construct models for specific viewing angles appropriate to the Crab and Vela pulsars. Phase-resolved spectra are also computed in the polar cap case and provide signatures for testing the models. The calculations have been extended to include millisecond pulsars, and we have been able to predict fluxes and spectra for populations of recycled pulsars, which are compared to COS B data for globular cluster populations.

  13. VERITAS observations of the Crab pulsar

    NASA Astrophysics Data System (ADS)

    Zitzer, Benjamin; VERITAS Collaboration

    2012-12-01

    The Crab pulsar has been widely studied across the electromagnetic spectrum from radio to gamma-ray energies. The exact nature of the emission processes taking place in the pulsar is a matter of broad debate. Above a few GeV the energy spectrum turns over suddenly. The shape of this cutoff can provide unique insight in to the particle acceleration processes taking place in the pulsar magnetosphere. Here we discuss the detection of pulsed gamma-rays from the Crab Pulsar above 100 GeV with the VERITAS telescopes in the context of measurements made with the Fermi space telescope below 10 GeV. Limits on the level of flux enhancement of emission correlated with giant radio pulses and dispersion due to Lorentz invariance violation effects will also be presented.

  14. Perspectives on Gamma-Ray Pulsar Emission

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.

    2011-09-01

    Pulsars are powerful sources of radiation across the electromagnetic spectrum. This paper highlights some theoretical insights into non-thermal, magnetospheric pulsar gamma-ray radiation. These advances have been driven by NASA's Fermi mission, launched in mid-2008. The Large Area Telescope (LAT) instrument on Fermi has afforded the discrimination between polar cap and slot gap/outer gap acceleration zones in young and middle-aged pulsars. Altitude discernment using the highest energy pulsar photons will be addressed, as will spectroscopic interpretation of the primary radiation mechanism in the LAT band, connecting to both polar cap/slot gap and outer gap scenarios. Focuses will mostly be on curvature radiation and magnetic pair creation, including population trends that may afford probes of the magnetospheric accelerating potential.

  15. Exploring the Universe with Pulsar Timing Arrays

    NASA Astrophysics Data System (ADS)

    Burke-Spolaor, Sarah

    2016-03-01

    It is an exciting time for pulsar timing arrays, as their upper limits on gravitational radiation are carving into the expected strength of gravitational waves from several source populations in the Universe. Cosmic strings, inflationary gravitational waves, and binary supermassive black holes are all expected contributors to the nanohertz to microhertz band probed by pulsar timing arrays: they might be discovered as bursting sources, as continuously oscillating signals, or as an ensemble population in a stochastic background. This presentation will discuss the predicted intensity and form of these sources, and how the upper limits set by pulsar timing arrays are being used to set unique constraints on source properties, and to measure galaxy evolution in the nearby Universe. Looking to the future, we will explore how pulsar timing arrays can characterize their target source populations, and we will present the prospects for multi-messenger detection.

  16. A Candidate Optical Counterpart to the Middle Aged γ-RAY Pulsar PSRJ1741–2054

    NASA Astrophysics Data System (ADS)

    Mignani, R. P.; Testa, V.; Marelli, M.; De Luca, A.; Salvetti, D.; Belfiore, A.; Pierbattista, M.; Razzano, M.; Shearer, A.; Moran, P.

    2016-07-01

    We carried out deep optical observations of the middle aged γ-ray pulsar PSR J1741‑2054 with the Very Large Telescope (VLT). We identified two objects, of magnitudes m v = 23.10 ± 0.05 and m v = 25.32 ± 0.08, at positions consistent with the very accurate Chandra coordinates of the pulsar, the faintest of which is more likely to be its counterpart. From the VLT images we also detected the known bow-shock nebula around PSR J1741‑2054. The nebula is displaced by ˜0.″9 (at the 3σ confidence level) with respect to its position measured in archival data, showing that the shock propagates in the interstellar medium consistently with the pulsar proper motion. Finally, we could not find evidence of large-scale extended optical emission associated with the pulsar wind nebula detected by Chandra, down to a surface brightness limit of ˜28.1 mag arcsec‑2. Future observations are needed to confirm the optical identification of PSR J1741‑2054 and characterize the spectrum of its counterpart. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO programme 095.D-0328(B).

  17. A massive neutron star in the millisecond pulsar PSR J2215+5135

    NASA Astrophysics Data System (ADS)

    Shahbaz, Tariq

    2016-07-01

    Binary evolution may increase neutron masses via accretion. Hence the most massive neutron stars (NSs) are expected to be located amongst the binary millisecond pulsars (MSPs) spun-up within X-ray binaries. Most MSPs are found with brown dwarf lookalikes or ˜0.2 M stars in systems called "black widows" and "redbacks", respectively, because these companions are ablated by the pulsar wind. These systems offer some advantages over white dwarf-pulsar binaries: they are typically brighter, they present strongly irradiated hemispheres, and they fill significant fractions of their Roche lobes. As a result, their optical light curves exhibit variability due to a combination of their ellipsoidal shape and irradiation, which can be modelled in order to determine orbital parameters such as the mass ratio and inclination. Combining these with optical spectroscopy and/or pulsar timing enables one to determine a reliable NS masses. Here we present the results of our detailed modelling of the optical lightcurves and radial velocity curves of J2215+5135, which allows us to determine various ystem parameters, including the NS mass.

  18. A Candidate Optical Counterpart to the Middle Aged γ-RAY Pulsar PSRJ1741-2054

    NASA Astrophysics Data System (ADS)

    Mignani, R. P.; Testa, V.; Marelli, M.; De Luca, A.; Salvetti, D.; Belfiore, A.; Pierbattista, M.; Razzano, M.; Shearer, A.; Moran, P.

    2016-07-01

    We carried out deep optical observations of the middle aged γ-ray pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two objects, of magnitudes m v = 23.10 ± 0.05 and m v = 25.32 ± 0.08, at positions consistent with the very accurate Chandra coordinates of the pulsar, the faintest of which is more likely to be its counterpart. From the VLT images we also detected the known bow-shock nebula around PSR J1741-2054. The nebula is displaced by ˜0.″9 (at the 3σ confidence level) with respect to its position measured in archival data, showing that the shock propagates in the interstellar medium consistently with the pulsar proper motion. Finally, we could not find evidence of large-scale extended optical emission associated with the pulsar wind nebula detected by Chandra, down to a surface brightness limit of ˜28.1 mag arcsec-2. Future observations are needed to confirm the optical identification of PSR J1741-2054 and characterize the spectrum of its counterpart. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO programme 095.D-0328(B).

  19. Search for VHE gamma-ray emission from Geminga pulsar and nebula with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Buson, S.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, A.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Satalecka, K.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vanzo, G.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.

    2016-06-01

    The Geminga pulsar, one of the brighest gamma-ray sources, is a promising candidate for emission of very-high-energy (VHE > 100 GeV) pulsed gamma rays. Also, detection of a large nebula has been claimed by water Cherenkov instruments. We performed deep observations of Geminga with the MAGIC telescopes, yielding 63 h of good-quality data, and searched for emission from the pulsar and pulsar wind nebula. We did not find any significant detection, and derived 95% confidence level upper limits. The resulting upper limits of 5.3 × 10-13 TeV cm-2 s-1 for the Geminga pulsar and 3.5 × 10-12 TeV cm-2 s-1 for the surrounding nebula at 50 GeV are the mostconstraining ones obtained so far at VHE. To complement the VHE observations, we also analyzed 5 yr of Fermi-LAT data from Geminga, finding that the sub-exponential cut-off is preferred over the exponential cut-off that has been typically used in the literature. We also find that, above 10 GeV, the gamma-ray spectra from Geminga can be described with a power law with index softer than 5. The extrapolation of the power-law Fermi-LAT pulsed spectra to VHE goes well below the MAGIC upper limits, indicating that the detection of pulsed emission from Geminga with the current generation of Cherenkov telescopes is very difficult.

  20. The Galactic center pulsar SGR J1745-29

    NASA Astrophysics Data System (ADS)

    Bower, Geoffrey C.

    2014-05-01

    The discovery of the Galactic center pulsar SGR J1745-29 has provided an important new window into plasma processes in the Galactic center (GC) interstellar medium, the population of compact objects in the GC, and the prospects for probing general relativistic effects through timing of a Sgr A* pulsar companion. We discuss here radio observations of the pulsar and how they are providing fresh insights. In particular, our results show that recent pulsar surveys had the sensitivity to detect many pulsars in the GC region without significant losses due to interstellar scattering. This raise the question of why only this pulsar close to Sgr A* has been detected.

  1. Birth and Evolution of Isolated Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Kaspi, Victoria M.

    2008-02-01

    We investigate the birth and evolution of isolated radio pulsars using a population synthesis method, modeling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam (MB) surveys. Together, the Parkes and Swinburne MB surveys [1, 2] have detected nearly 2/3 of the known pulsars and provide a remarkably homogeneous sample to compare with simulations. New proper motion measurements [3, 4] and an improved model of the distribution of free electrons in the interstellar medium, NE2001 [5], also make revisiting these issues particularly worthwhile. We present a simple population model that reproduces the actual observations well, and consider others that fail. We conclude that: pulsars are born in the spiral arms, with the birthrate of 2.8+/-0.5 pulsars/century peaking at a distance ~3 kpc from the Galactic centre, and with mean initial speed of 380-60+40 km s-1 the birth spin period distribution extends to several hundred milliseconds, with no evidence of multimodality, implying that characteristic ages overestimate the true ages of the pulsars by a median factor >2 for true ages <30,000 yr models in which the radio luminosities of the pulsars are random generically fail to reproduce the observed P-Ṗ diagram, suggesting a relation between intrinsic radio luminosity and (P,Ṗ) radio luminosities L~Ė provides a good match to the observed P-Ṗ diagram; for this favored radio luminosity model, we find no evidence for significant magnetic field decay over the lifetime of the pulsars as radio sources (~100 Myr).

  2. On the magnetosphere of an accelerated pulsar

    NASA Astrophysics Data System (ADS)

    Brennan, T. Daniel; Gralla, Samuel E.

    2014-05-01

    We report on a remarkable class of exact solutions to force-free electrodynamics that has four-current along the light cones of an arbitrary timelike worldline in flat spacetime. No symmetry is assumed, and the solutions are given in terms of a free function of three variables. The field configuration should describe the outer magnetosphere of a pulsar moving on the worldline. The power radiated is the sum of an acceleration (Larmor-type) term and a pulsar-type term.

  3. Pulsar-aided SETI experimental observations

    NASA Technical Reports Server (NTRS)

    Heidmann, J.; Biraud, F.; Tarter, J.

    1989-01-01

    The rotational frequencies of pulsars are used to select preferred radio frequencies for SETI. Pulsar rotational frequencies are converted into SETI frequencies in the 1-10 GHz Galactic radio window. Experimental observations using the frequencies are conducted for target stars closer than 25 parsecs, unknown targets in a globular cluster, and unknown targets in the Galaxy closer than 2.5 kpc. The status of these observations is discussed.

  4. Physics of Rotation Powered Pulsars and Their Nebulae

    NASA Technical Reports Server (NTRS)

    Arons, Jonathan

    1997-01-01

    This letter is my progress report for the Astrophysics Theory grant. The first goal of the research supported by this grant is to produce a time dependent theory of the unsteady relativistic collisionless shock wave terminating the relativistic wind from a pulsar, and compare the predicted surface brightness fluctuations to Hubble Space Telescope observations of the wisps in the Crab Nebula. The second goal is to model the production of electron-positron pairs over the polar caps of rotation powered pulsars, and use the results to predict the heating of the surface due to particle trapping and bombardment of the atmosphere at the base of the polar field lines. We have succeeded in creating a one dimensional hybrid code, in which the electron-positron pairs incident on the shock structure are modeled as a relativistic, adiabatic, ideal MHD fluid, while the heavy ions are treated as particles using a particle-in-cell algorithm. The electromagnetic fields are evaluated from the currents and charge densities in the pairs and the ions, while the particles and the fluid accelerate in response to the computed self-consistent electromagnetic fields. The results are promising, in that the underlying ion cyclotron instability generates finite amplitude, propagating magnetosonic waves in the pairs, whose wavelengths and frequencies, when translated into physical units, are comparable to the observed running waves of brightness observed by HST near the Crab pulsar. The code is undergoing a number of tests, to assure us that this preliminary correspondence is not an artifact. In the coming year, the observational appearance of the models will be computed and compared to the HST observations of the Crab now in hand, and used to predict the HST results which will be obtained the year after next. WE also developed a one dimensional cascade theory for pair creation over pulsars' polar caps. A linear integral equation describing the synchrotron cascade has been derived and solved by

  5. Precision Pulsar Timing at the DSN

    NASA Astrophysics Data System (ADS)

    Majid, Walid A.

    2016-01-01

    Millisecond pulsars are a class of radio pulsars with extremely stable rotations. The excellent timing stability of millisecond pulsars can be used to study a wide variety of astrophysical phenomena. In particular, observations of a large sample of these pulsars can be used to detect the presence of low-frequency gravitational waves. We have developed and are now commissioning a precision pulsar timing backend for the Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to observe and time pulses from an ensemble of millisecond pulsars. The NASA Deep Space Network (DSN) operates clusters of large dish antennas (up to 70-m in diameter), located roughly equi-distant around the Earth, for communication and tracking of deep-space spacecraft. The backend system is capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations scheduled over the next few years.

  6. Pulsar observations with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Fidalgo, David

    2016-07-01

    The vast majority of spectra of gamma-ray pulsars exhibit an exponential cut-off at a few GeV, as seen by the Large Area Telescope (LAT) on board of the Fermi satellite. Due to this cut-off, current Imaging Atmospheric Cherenkov Telescopes (IACTs) with an energy threshold as low as 30 GeV, struggle to detect pulsars. So far, emission above 50 GeV has been confirmed only for the Crab and Vela pulsars. In the case of the former, the spectrum even extends up to about 1 TeV firmly revealing a second emission component. To further understand the emission mechanism of gamma-ray pulsars, the MAGIC collaboration continues the search of pulsars above 50 GeV. In this talk we report on recent results on the Crab and Geminga Pulsar obtained with the MAGIC telescopes, including the analysis of data taken with a new trigger system lowering the energy threshold of the MAGIC telescopes.

  7. DETECTING GRAVITATIONAL WAVE MEMORY WITH PULSAR TIMING

    SciTech Connect

    Cordes, J. M.; Jenet, F. A. E-mail: merlyn@phys.utb.edu

    2012-06-10

    We compare the detectability of gravitational bursts passing through the solar system with those passing near each millisecond pulsar in an N-pulsar timing array. The sensitivity to Earth-passing bursts can exploit the correlation expected in pulse arrival times while pulsar-passing bursts, though uncorrelated between objects, provide an N-fold increase in overall time baseline that can compensate for the lower sensitivity. Bursts with memory from mergers of supermassive black holes produce step functions in apparent spin frequency that are the easiest to detect in pulsar timing. We show that the burst rate and amplitude distribution, while strongly dependent on inadequately known cosmological evolution, may favor detection in the pulsar terms rather than the Earth timing perturbations. Any contamination of timing data by red spin noise makes burst detection more difficult because both signals grow with the length of the time data span T. Furthermore, the different bursts that could appear in one or more data sets of length T Almost-Equal-To 10 yr also affect the detectability of the gravitational wave stochastic background that, like spin noise, has a red power spectrum. A burst with memory is a worthwhile target in the timing of multiple pulsars in a globular cluster because it should produce a correlated signal with a time delay of less than about 10 years in some cases.

  8. The Swinburne intermediate-latitude pulsar survey

    NASA Astrophysics Data System (ADS)

    Edwards, R. T.; Bailes, M.; van Straten, W.; Britton, M. C.

    2001-09-01

    We have conducted a survey of intermediate Galactic latitudes using the 13-beam 21-cm multibeam receiver of the Parkes 64-m radio telescope. The survey covered the region enclosed by 5°<|b|<15° and -100°pulsars in the region with flux densities greater than approximately 0.3-1.1mJy. Offline analysis on the 64-node Swinburne workstation cluster resulted in the detection of 170 pulsars of which 69 were new discoveries. Eight of the new pulsars, by virtue of their small spin periods and period derivatives, may be recycled and have been reported elsewhere. The slow pulsars discovered are typical of those already known in the volume searched, being of intermediate to old age. Several pulsars experience pulse nulling and two display very regular drifting subpulses. We discuss the new discoveries and provide timing parameters for the 48 slow pulsars for which we have a phase-connected solution.

  9. Polarized curvature radiation in pulsar magnetosphere

    NASA Astrophysics Data System (ADS)

    Wang, P. F.; Wang, C.; Han, J. L.

    2014-07-01

    The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and corotating with the pulsar magnetosphere. Within the 1/γ emission cone, the waves can be divided into two natural wave-mode components, the ordinary (O) mode and the extraordinary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the corotation of relativistic particles with magnetosphere is not considered, the intensity distributions for the X-mode and O-mode components are quite similar within the pulsar beam, which causes serious depolarization. However, if the corotation of relativistic particles is considered, the intensity distributions of the two modes are very different, and the net polarization of outcoming emission should be significant. Our numerical results are compared with observations, and can naturally explain the orthogonal polarization modes of some pulsars. Strong linear polarizations of some parts of pulsar profile can be reproduced by curvature radiation and subsequent propagation effect.

  10. Precision Pulsar Timing at the DSN

    NASA Astrophysics Data System (ADS)

    Majid, Walid A.

    2015-01-01

    Millisecond pulsars are a class of radio pulsars with extremely stable rotations. The excellent timing stability of millisecond pulsars can be used to study a wide variety of astrophysical phenomena. In particular, observations of a large sample of these pulsars can be used to detect the presence of low-frequency gravitational waves. We have developed a precision pulsar timing backend for the Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to observe and time pulses from an ensemble of millisecond pulsars. The NASA Deep Space Network (DSN) operates clusters of large dish antennas (up to 70-m in diameter), located roughly equi-distant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations scheduled later this year.This research was performed at the Jet Propulsion Laboratory,California Institute of Technology, under the Research and TechnologyDevelopment Program, under a contract with the National Aeronautics andSpace Administration.

  11. Experimental Validation of Pulse Phase Tracking for X-Ray Pulsar Based

    NASA Technical Reports Server (NTRS)

    Anderson, Kevin

    2012-01-01

    Pulsars are a form of variable celestial source that have shown to be usable as aids for autonomous, deep space navigation. Particularly those sources emitting in the X-ray band are ideal for navigation due to smaller detector sizes. In this paper X-ray photons arriving from a pulsar are modeled as a non-homogeneous Poisson process. The method of pulse phase tracking is then investigated as a technique to measure the radial distance traveled by a spacecraft over an observation interval. A maximum-likelihood phase estimator (MLE) is used for the case where the observed frequency signal is constant. For the varying signal frequency case, an algorithm is used in which the observation window is broken up into smaller blocks over which an MLE is used. The outputs of this phase estimation process were then looped through a digital phase-locked loop (DPLL) in order to reduce the errors and produce estimates of the doppler frequency. These phase tracking algorithms were tested both in a computer simulation environment and using the NASA Goddard Space flight Center X-ray Navigation Laboratory Testbed (GXLT). This provided an experimental validation with photons being emitted by a modulated X-ray source and detected by a silicon-drift detector. Models of the Crab pulsar and the pulsar B1821-24 were used in order to generate test scenarios. Three different simulated detector trajectories were used to be tracked by the phase tracking algorithm: a stationary case, one with constant velocity, and one with constant acceleration. All three were performed in one-dimension along the line of sight to the pulsar. The first two had a constant signal frequency and the third had a time varying frequency. All of the constant frequency cases were processed using the MLE, and it was shown that they tracked the initial phase within 0.15% for the simulations and 2.5% in the experiments, based on an average of ten runs. The MLE-DPLL cascade version of the phase tracking algorithm was used in

  12. Young Pulsar Reveals Clues to Supernova

    NASA Astrophysics Data System (ADS)

    2001-09-01

    Astronomers examined the remnants of a stellar explosion with NASA's Chandra X-ray Observatory and discovered one of the youngest known pulsars. The properties of this pulsar, a neutron star rotating 15 times a second, will enable scientists to better understand how neutron stars are formed in the seconds just before a supernova explosion, and how they pump energy into the space around them for thousands of years after the explosion. A team led by Stephen Murray of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA studied 3C58, the remains of a supernova observed on Earth in 1181 AD in the constellation Cassiopeia. In addition to a pulsating central source they observed an extended X-ray source surrounding the pulsar thought to be produced by a cloud of high-energy particles about 20 light years across. These results were presented at the "Two Years of Science with Chandra" symposium in Washington, D.C. According to Murray, "Our discovery shows that all pulsars are not born equal. This pulsar is about the same age as the Crab Nebula pulsar, but there is little family resemblance." Murray explained that the 3C58 pulsar, which is now rotating at about half the rate of the Crab pulsar, is rotating almost as fast as it was when it was formed. In contrast, the Crab pulsar was formed spinning much more rapidly and has slowed to about half its initial speed. Conventional theory has assumed that all pulsars were like the Crab, born with rapid rotation and then have spun down considerably. The observations of 3C58, along with Chandra observations by another group of scientists of a pulsar associated with the supernova of 386 AD have cast doubt on that assumption, however. Furthermore, the X-ray power of 3C58 and its surrounding nebula are 20,000 and 1,000 times weaker than the Crab pulsar and its surrounding nebula respectively. One possibility for the low power of 3C58 is that the energy flow from its pulsar is primarily in the form of electromagnetic fields

  13. Pulsars "Lying About Their Ages," Astronomers Say, Throwing Theories Into Doubt

    NASA Astrophysics Data System (ADS)

    2000-07-01

    -24, to have travelled from the center of the supernova remnant to its present position in 16,000 years, it would have to have moved at about 1,000 miles per second, a particularly high speed compared to other pulsars. Gaensler and Frail compared a 1993 VLA image of the region to one they made last year to measure the pulsar's change in position over a known time, and thus to calculate its speed. They were surprised to find the pulsar moved at a maximum of about 350 miles per second. "This means the pulsar took much longer to reach its current position, and so it is a much older object than we had believed," said Frail. Columbia University astronomer David Helfand, who, with Robert Becker of the University of California-Davis, first drew attention to the unusual nature of "The Duck" in 1985, said he was "secretly delighted" with the new VLA measurements. "I was skeptical of the high velocity" attributed to the object earlier, he said. The new work, he said, "clearly cautions us that a present snapshot of a system does not always give a full picture of its history." For years, astronomers have estimated the age of a pulsar by measuring the rotation period of its neutron star and the tiny amount by which that rotation slows down over time. The neutron star's powerful magnetic field acts as a giant dynamo, emitting electromagnetic radiation as the star rotates. That loss of energy slows the star's rotation, according to the standard theory used for nearly three decades. A calculation based on the neutron star's rotation period and its rate of slowing produces what astronomers call its "characteristic age," which has been presumed to be the true age. That presumption now is called into question. With the large difference between B1757-24's "characteristic age" and the age required by the new VLA measurements, "this pulsar has been lying to us about its age," said Frail. The discrepancy could require astronomers to re-examine many of their previous conclusions about neutron

  14. Discovery of Eight Recycled Pulsars --- The Swinburne Intermediate Latitude Pulsar Survey

    NASA Astrophysics Data System (ADS)

    Edwards, Russell T.

    We have conducted a pulsar survey of intermediate Galactic latitudes (15deg < |b| < 5deg) at 20 cm. The survey has been highly successful, discovering 58 new pulsars, eight of which are recycled, in only ~14 days of integration time. One pulsar has a very narrow (2deg FWHM) average profile for the pulsar's period (278 ms). The six new recycled binary systems provide valuable information on the formation of white dwarf pulsar binaries. Two systems have massive white dwarf companions (> 0.57 Mo and > 1.2 Mo), while anotherhas a low mass (~0.2 Mo) companion in a 23.3-d orbit, residing the well-known orbital period ``gap''.

  15. The Velocity Distribution of Isolated Radio Pulsars

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Chernoff, D. F.; Cordes, J. M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We infer the velocity distribution of radio pulsars based on large-scale 0.4 GHz pulsar surveys. We do so by modelling evolution of the locations, velocities, spins, and radio luminosities of pulsars; calculating pulsed flux according to a beaming model and random orientation angles of spin and beam; applying selection effects of pulsar surveys; and comparing model distributions of measurable pulsar properties with survey data using a likelihood function. The surveys analyzed have well-defined characteristics and cover approx. 95% of the sky. We maximize the likelihood in a 6-dimensional space of observables P, dot-P, DM, absolute value of b, mu, F (period, period derivative, dispersion measure, Galactic latitude, proper motion, and flux density). The models we test are described by 12 parameters that characterize a population's birth rate, luminosity, shutoff of radio emission, birth locations, and birth velocities. We infer that the radio beam luminosity (i) is comparable to the energy flux of relativistic particles in models for spin-driven magnetospheres, signifying that radio emission losses reach nearly 100% for the oldest pulsars; and (ii) scales approximately as E(exp 1/2) which, in magnetosphere models, is proportional to the voltage drop available for acceleration of particles. We find that a two-component velocity distribution with characteristic velocities of 90 km/ s and 500 km/ s is greatly preferred to any one-component distribution; this preference is largely immune to variations in other population parameters, such as the luminosity or distance scale, or the assumed spin-down law. We explore some consequences of the preferred birth velocity distribution: (1) roughly 50% of pulsars in the solar neighborhood will escape the Galaxy, while approx. 15% have velocities greater than 1000 km/ s (2) observational bias against high velocity pulsars is relatively unimportant for surveys that reach high Galactic absolute value of z distances, but is severe for

  16. Fastest Pulsar Speeding Out of Galaxy, Astronomers Discover

    NASA Astrophysics Data System (ADS)

    2005-08-01

    A speeding, superdense neutron star somehow got a powerful "kick" that is propelling it completely out of our Milky Way Galaxy into the cold vastness of intergalactic space. Its discovery is puzzling astronomers who used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope to directly measure the fastest speed yet found in a neutron star. Pulsar's Path Across Sky Over about 2.5 million years, Pulsar B1508+55 has moved across about a third of the night sky as seen from Earth. CREDIT: Bill Saxton, NRAO/AUI/NSF (Click on image for larger version 67 KB) The neutron star is the remnant of a massive star born in the constellation Cygnus that exploded about two and a half million years ago in a titanic explosion known as a supernova. Ultra-precise VLBA measurements of its distance and motion show that it is on course to inevitably leave our Galaxy. "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding," said Shami Chatterjee, of the National Radio Astronomy Observatory (NRAO) and the Harvard-Smithsonian Center for Astrophysics. "This discovery is very difficult for the latest models of supernova core collapse to explain," he added. Chatterjee and his colleagues used the VLBA to study the pulsar B1508+55, about 7700 light-years from Earth. With the ultrasharp radio "vision" of the continent-wide VLBA, they were able to precisely measure both the distance and the speed of the pulsar, a spinning neutron star emitting powerful beams of radio waves. Plotting its motion backward pointed to a birthplace among groups of giant stars in the constellation Cygnus -- stars so massive that they inevitably explode as supernovae. "This is the first direct measurement of a neutron star's speed that exceeds 1,000 kilometers per second," said Walter Brisken, an NRAO astronomer. "Most earlier estimates of neutron-star speeds depended on educated

  17. Basic physics and cosmology from pulsar timing data

    NASA Technical Reports Server (NTRS)

    Taylor, J. H.

    1991-01-01

    Radio pulsars provide unparalleled opportunities for making measurements of astrophysically interesting phenomena. The author concentrates on two particular applications of high precision timing observations of pulsars: tests of relativistic gravitation theory using the binary pulsar 1913+16, and tests of cosmological models using timing data from millisecond pulsars. New upper limits are presented for the energy density of a cosmic background of low frequency gravitational radiation.

  18. Reconstructing the Guitar: Blowing Bubbles with a Pulsar Bow Shock Backflow

    NASA Astrophysics Data System (ADS)

    van Kerkwijk, Marten H.; Ingle, Ashleigh

    2008-08-01

    The Guitar Nebula is an Hα nebula produced by the interaction of the relativistic wind of a very fast pulsar, PSR B2224+65, with the interstellar medium. It consists of a ram-pressure confined bow shock near its head and a series of semicircular bubbles further behind, the two largest of which form the body of the Guitar. We present a scenario in which this peculiar morphology is due to instabilities in the backflow from the pulsar bow shock. From simulations, these backflows appear similar to jets and their kinetic energy is a large fraction of the total energy in the pulsar's relativistic wind. We suggest that, like jets, these flows become unstable some distance downstream, leading to rapid dissipation of the kinetic energy into heat, and the formation of an expanding bubble. We show that in this scenario the sizes, velocities, and surface brightnesses of the bubbles depend mostly on observables, and that they match roughly what is seen for the Guitar. Similar instabilities may account for features seen in other bow shocks.

  19. AB INITIO PULSAR MAGNETOSPHERE: THREE-DIMENSIONAL PARTICLE-IN-CELL SIMULATIONS OF OBLIQUE PULSARS

    SciTech Connect

    Philippov, Alexander A.; Spitkovsky, Anatoly; Cerutti, Benoit

    2015-03-01

    We present “first-principles” relativistic particle-in-cell simulations of the oblique pulsar magnetosphere with pair formation. The magnetosphere starts to form with particles extracted from the surface of the neutron star. These particles are accelerated by surface electric fields and emit photons capable of producing electron–positron pairs. We inject secondary pairs at the locations of primary energetic particles whose energy exceeds the threshold for pair formation. We find solutions that are close to the ideal force-free magnetosphere with the Y-point and current sheet. Solutions with obliquities ≤40° do not show pair production in the open field line region because the local current density along the magnetic field is below the Goldreich–Julian value. The bulk outflow in these solutions is charge-separated, and pair formation happens in the current sheet and return current layer only. Solutions with higher inclinations show pair production in the open field line region, with high multiplicity of the bulk flow and the size of the pair-producing region increasing with inclination. We observe the spin-down of the star to be comparable to MHD model predictions. The magnetic dissipation in the current sheet ranges between 20% for the aligned rotator and 3% for the orthogonal rotator. Our results suggest that for low obliquity neutron stars with suppressed pair formation at the light cylinder, the presence of phenomena related to pair activity in the bulk of the polar region, e.g., radio emission, may crucially depend on the physics beyond our simplified model, such as the effects of curved spacetime or multipolar surface fields.

  20. Unusual flux-distance relationship for pulsars suggested by analysis of the Australia national telescopy facility pulsar catalogue

    SciTech Connect

    Singleton, John; Perez, M R; Singleton, J; Ardavan, H; Ardavan, A

    2009-01-01

    We analyze pulsar fluxes at 1400 MHz (S(1400)) and distances d taken from the Australia National Telescope Facility (ATNF) Pulsar Catalogue. Under the assumption that pulsar populations in different parts of the Galaxy are similar, we find that either (a) pulsar fluxes diminish with distance according to a non-standard power law (we suggest S(1400){proportional_to} 1/d rather than {proportional_to} 1/d{sup 2}) or (b) that there are very significant (i.e. order of magnitude) errors in the distance estimates quoted in the ATNF Catalogue. The former conclusion (a) supports a recent model for pulsar emission that has also successfully explained the frequency spectrum of the Crab pulsar over 16 orders of magnitude of frequency, whilst alternative (b) would necessitate a radical re-evaluation of both the dispersion method for estimating pulsar distances and current ideas about the distribution of pulsars within our Galaxy.

  1. VARIABILITY OF THE PULSED RADIO EMISSION FROM THE LARGE MAGELLANIC CLOUD PULSAR PSR J0529-6652

    SciTech Connect

    Crawford, F.; Altemose, D.; Li, H.; Lorimer, D. R.

    2013-01-10

    We have studied the variability of PSR J0529-6652, a radio pulsar in the Large Magellanic Cloud (LMC), using observations conducted at 1390 MHz with the Parkes 64 m telescope. PSR J0529-6652 is detectable as a single pulse emitter, with amplitudes that classify the pulses as giant pulses. This makes PSR J0529-6652 the second known giant pulse emitter in the LMC, after PSR B0540-69. The fraction of the emitted pulses detectable from PSR J0529-6652 at this frequency is roughly two orders of magnitude greater than it is for either PSR B0540-69 or the Crab pulsar (if the latter were located in the LMC). We have measured a pulse nulling fraction of 83.3% {+-} 1.5% and an intrinsic modulation index of 4.07 {+-} 0.29 for PSR J0529-6652. The modulation index is significantly larger than values previously measured for typical radio pulsars but is comparable to values reported for members of several other neutron star classes. The large modulation index, giant pulses, and large nulling fraction suggest that this pulsar is phenomenologically more similar to these other, more variable sources, despite having spin and physical characteristics that are typical of the unrecycled radio pulsar population. The large modulation index also does not appear to be consistent with the small value predicted for this pulsar by a model of polar cap emission outlined by Gil and Sendyk. This conclusion depends to some extent on the assumption that PSR J0529-6652 is exhibiting core emission, as suggested by its simple profile morphology, narrow profile width, and previously measured profile polarization characteristics.

  2. NuSTAR OBSERVATIONS AND BROADBAND SPECTRAL ENERGY DISTRIBUTION MODELING OF THE MILLISECOND PULSAR BINARY PSR J1023+0038

    SciTech Connect

    Li, K. L.; Kong, A. K. H.; Tam, P. H. T.; Jin, Ruolan; Takata, J.; Cheng, K. S.; Hui, C. Y. E-mail: akong@phys.nthu.edu.tw

    2014-12-20

    We report the first hard X-ray (3-79 keV) observations of the millisecond pulsar (MSP) binary PSR J1023+0038 using NuSTAR. This system has been shown transiting between a low-mass X-ray binary (LMXB) state and a rotation-powered MSP state. The NuSTAR observations were taken in both LMXB state and rotation-powered state. The source is clearly seen in both states up to ∼79 keV. During the LMXB state, the 3-79 keV flux is about a factor of 10 higher than in the rotation-powered state. The hard X-rays show clear orbital modulation during the X-ray faint rotation-powered state but the X-ray orbital period is not detected in the X-ray bright LMXB state. In addition, the X-ray spectrum changes from a flat power-law spectrum during the rotation-powered state to a steeper power-law spectrum in the LMXB state. We suggest that the hard X-rays are due to the intrabinary shock from the interaction between the pulsar wind and the injected material from the low-mass companion star. During the rotation-powered MSP state, the X-ray orbital modulation is due to Doppler boosting of the shocked pulsar wind. At the LMXB state, the evaporating matter of the accretion disk due to the gamma-ray irradiation from the pulsar stops almost all the pulsar wind, resulting in the disappearance of the X-ray orbital modulation.

  3. The 4U 0115+63: Another energetic gamma ray binary pulsar

    NASA Technical Reports Server (NTRS)

    Chadwick, P. M.; Dipper, N. A.; Dowthwaite, J. C.; Kirkman, I. W.; Mccomb, T. J. L.; Orford, K. J.; Turver, K. E.

    1985-01-01

    Following the discovery of Her X-1 as a source of pulsed 1000 Gev X-rays, a search for emission from an X-ray binary containing a pulsar with similar values of period, period derivative and luminosity was successful. The sporadic X-ray binary 4U 0115-63 has been observed, with probability 2.5 x 10 to the minus 6 power ergs/s to emit 1000 GeV gamma-rays with a time averaged energy flux of 6 to 10 to the 35th power.

  4. On the Extended Emission of the Anomalous X-ray Pulsar IE 1547.0-5408

    NASA Technical Reports Server (NTRS)

    Olausen, S. A.; Kaspi, V. M.; Ng, C. -Y.; Zhu, W. W.; Gavriil, F. P.; Woods, P. M.

    2012-01-01

    We present an analysis of the extended emission around the anomalous X-ray pulsar IE 1547.0-5408 using four XMM-Newton observations taken with the source in varying states of outburst as well as in quiescence. We find that the extended emission flux is highly variable and strongly correlated with the flux of the magnetar. Based on this result, as well as on spectral and energetic considerations, we conclude that the extended emission is dominated by a dust-scattering halo and not a pulsar wind nebula (P-VVN), as has been previously argued. We obtain an upper limit on the 2-10 keV flux of a possible PWN of 4.7 x 10(exp -14) erg/s/sq cm, three times less than the previously claimed value, implying an efficiency for conversion of spin-down energy into nebular luminosity of <9 x 10(exp -4) .

  5. THE PULSAR SEARCH COLLABORATORY: DISCOVERY AND TIMING OF FIVE NEW PULSARS

    SciTech Connect

    Rosen, R.; Swiggum, J.; McLaughlin, M. A.; Lorimer, D. R.; Yun, M.; Boyles, J.; Heatherly, S. A.; Scoles, S.; Lynch, R.; Kondratiev, V. I.; Ransom, S. M.; Moniot, M. L.; Thompson, C.; Cottrill, A.; Raycraft, M.; Weaver, M.; Snider, A.; Dudenhoefer, J.; Allphin, L.; Thorley, J.; and others

    2013-05-01

    We present the discovery and timing solutions of five new pulsars by students involved in the Pulsar Search Collaboratory, a NSF-funded joint program between the National Radio Astronomy Observatory and West Virginia University designed to excite and engage high-school students in Science, Technology, Engineering, and Mathematics (STEM) and related fields. We encourage students to pursue STEM fields by apprenticing them within a professional scientific community doing cutting edge research, specifically by teaching them to search for pulsars. The students are analyzing 300 hr of drift-scan survey data taken with the Green Bank Telescope at 350 MHz. These data cover 2876 deg{sup 2} of the sky. Over the course of five years, more than 700 students have inspected diagnostic plots through a web-based graphical interface designed for this project. The five pulsars discovered in the data have spin periods ranging from 3.1 ms to 4.8 s. Among the new discoveries are PSR J1926-1314, a long period, nulling pulsar; PSR J1821+0155, an isolated, partially recycled 33 ms pulsar; and PSR J1400-1438, a millisecond pulsar in a 9.5 day orbit whose companion is likely a white dwarf star.

  6. The Pulsar Search Collaboratory: Discovery and Timing of Five New Pulsars

    NASA Astrophysics Data System (ADS)

    Rosen, R.; Swiggum, J.; McLaughlin, M. A.; Lorimer, D. R.; Yun, M.; Heatherly, S. A.; Boyles, J.; Lynch, R.; Kondratiev, V. I.; Scoles, S.; Ransom, S. M.; Moniot, M. L.; Cottrill, A.; Weaver, M.; Snider, A.; Thompson, C.; Raycraft, M.; Dudenhoefer, J.; Allphin, L.; Thorley, J.; Meadows, B.; Marchiny, G.; Liska, A.; O'Dwyer, A. M.; Butler, B.; Bloxton, S.; Mabry, H.; Abate, H.; Boothe, J.; Pritt, S.; Alberth, J.; Green, A.; Crowley, R. J.; Agee, A.; Nagley, S.; Sargent, N.; Hinson, E.; Smith, K.; McNeely, R.; Quigley, H.; Pennington, A.; Chen, S.; Maynard, T.; Loope, L.; Bielski, N.; McGough, J. R.; Gural, J. C.; Colvin, S.; Tso, S.; Ewen, Z.; Zhang, M.; Ciccarella, N.; Bukowski, B.; Novotny, C. B.; Gore, J.; Sarver, K.; Johnson, S.; Cunningham, H.; Collins, D.; Gardner, D.; Monteleone, A.; Hall, J.; Schweinhagen, R.; Ayers, J.; Jay, S.; Uosseph, B.; Dunkum, D.; Pal, J.; Dydiw, S.; Sterling, M.; Phan, E.

    2013-05-01

    We present the discovery and timing solutions of five new pulsars by students involved in the Pulsar Search Collaboratory, a NSF-funded joint program between the National Radio Astronomy Observatory and West Virginia University designed to excite and engage high-school students in Science, Technology, Engineering, and Mathematics (STEM) and related fields. We encourage students to pursue STEM fields by apprenticing them within a professional scientific community doing cutting edge research, specifically by teaching them to search for pulsars. The students are analyzing 300 hr of drift-scan survey data taken with the Green Bank Telescope at 350 MHz. These data cover 2876 deg2 of the sky. Over the course of five years, more than 700 students have inspected diagnostic plots through a web-based graphical interface designed for this project. The five