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Wei Wang - One of the best experts on this subject based on the ideXlab platform.

  • radio to tev phase resolved emission from the crab pulsar the Annular Gap model
    The Astrophysical Journal, 2012
    Co-Authors: G J Qiao, Wei Wang
    Abstract:

    The Crab pulsar is a quite young, famous pulsar that radiates multi-wavelength pulsed photons. The latest detection of GeV and TeV pulsed emission with an unprecedented signal-to-noise ratio, supplied by the powerful telescopes Fermi, MAGIC, and VERITAS, challenges the current popular pulsar models, and can be a valuable discriminator to justify the pulsar high-energy-emission models. Our work is divided into two steps. First, taking reasonable parameters (the magnetic inclination angle {alpha} = 45 Degree-Sign and the view angle {zeta} = 63 Degree-Sign ), we use the latest high-energy data to calculate radio, X-ray, {gamma}-ray, and TeV light curves from a geometric view to obtain crucial information on emission locations. Second, we calculate the phase-averaged spectrum and phase-resolved spectra for the Crab pulsar and take a theoretical justification from a physical view for the emission properties as found in the first step. It is found that a Gaussian emissivity distribution with the peak emission near the null charge surface in the so-called Annular Gap (AG) region gives the best modeled light curves. The pulsed radio, X-ray, {gamma}-ray, and TeV emission are mainly generated from the emission of primary particles or secondary particles with different emission mechanisms in the nearly similar regionmore » of the AG located in the only magnetic pole, which leads to the nearly 'phase-aligned' multi-wavelength light curves. The emission of peak 1 and peak 2 originates from the AG region near the null charge surface, while the emission of the bridge primarily originates from the core Gap (CG) region. The charged particles cannot co-rotate with the pulsar and escape from the magnetosphere, which determines the original flowing primary particles. The acceleration electric field and potential in the AG and CG are huge enough and are in the several tens of neutron star radii. Thus, the primary particles are accelerated to ultra-relativistic energies and produce numerous secondary particles (pairs) in the inner regions of the AG and CG. We emphasize that there are mainly two types of pairs: one is curvature-radiation induced (CR-induced) and the other is inverse-Compton-scattering induced (ICS-induced). The phase-averaged spectrum and phase-resolved spectra from soft X-ray to TeV bands are produced by four components: synchrotron radiation from CR- and ICS-induced pairs dominates the X-ray band to soft {gamma}-ray band (100 eV to 10 MeV); curvature radiation and synchrotron radiation from the primary particles mainly contribute to the {gamma}-ray band (10 MeV to {approx}20 GeV); ICS from the pairs significantly contributes to the TeV {gamma}-ray band ({approx}20-400 GeV). The multi-wavelength pulsed emission from the Crab pulsar can be well modeled with the AG and CG model. To distinguish our single magnetic pole model from two-pole models, the convincing values of the magnetic inclination angle and the viewing angle will play a key role.« less

  • Radio-to-TeV Phase-resolved Emission from the Crab Pulsar: The Annular Gap Model
    The Astrophysical Journal, 2012
    Co-Authors: Guojun Qiao, Wei Wang
    Abstract:

    In the framework of the three-dimensional (3D) Annular Gap model with reasonable parameters (the magnetic inclination angle \alpha = 45 deg and the view angle \zeta = 63 deg), we first use the latest hight energy data to self-consistently calculate radio, X-ray, gamma-ray and TeV (MAGIC and VERITAS) light curves, phase-averaged spectrum and phase-resolved spectra for the Crab pulsar. It is found that the acceleration electric field and potential in the Annular Gap and core Gap are huge enough in the several tens of neutron star radii. The pulsed emission of radio, X-ray, gamma-ray and TeV are mainly generated from the emission of primary particles or secondary particles with different emission mechanisms in the nearly similar region of the Annular Gap located in the only one magnetic pole, which leads to the nearly "phase-aligned" multi-wavelength light curves. The emission of peak 1 (P1) and peak 2 (P2) is originated from the Annular Gap region near the null charge surface, while the emission of bridge is mainly originated from the core Gap region. The phase-averaged spectrum and phase-resolved spectra of the Crab pulsar from soft X-ray to TeV band are produced by four components: synchrotron radiation from CR-induced and ICS-induced pairs dominates the X-ray band to soft gamma-ray band (100 eV to 10 MeV); curvature radiation and synchrotron radiation from the primary particles mainly contribute to gamma-ray band (10 MeV to \sim 20 GeV); ICS from the pairs significantly contributes to the TeV gamma-ray band (\sim 20 GeV to 400 GeV). The multi-wavelength pulsed emission from the Crab pulsar has been well modeled with the Annular Gap and core Gap model. To distinguish our single magnetic pole model from two-pole models, the convincing values of the magnetic inclination angle and the viewing angle will play a key role.

Guojun Qiao - One of the best experts on this subject based on the ideXlab platform.

  • The Annular Gap: Gamma-Ray & Radio Emission of Pulsars
    International Journal of Modern Physics: Conference Series, 2013
    Co-Authors: Guojun Qiao, J. L. Han
    Abstract:

    Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the Annular Gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot Gap and outer Gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the Annular Gap would play a very important role. Here we show some observational and theoretical evidences about the Annular Gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.

  • Radio-to-TeV Phase-resolved Emission from the Crab Pulsar: The Annular Gap Model
    The Astrophysical Journal, 2012
    Co-Authors: Guojun Qiao, Wei Wang
    Abstract:

    In the framework of the three-dimensional (3D) Annular Gap model with reasonable parameters (the magnetic inclination angle \alpha = 45 deg and the view angle \zeta = 63 deg), we first use the latest hight energy data to self-consistently calculate radio, X-ray, gamma-ray and TeV (MAGIC and VERITAS) light curves, phase-averaged spectrum and phase-resolved spectra for the Crab pulsar. It is found that the acceleration electric field and potential in the Annular Gap and core Gap are huge enough in the several tens of neutron star radii. The pulsed emission of radio, X-ray, gamma-ray and TeV are mainly generated from the emission of primary particles or secondary particles with different emission mechanisms in the nearly similar region of the Annular Gap located in the only one magnetic pole, which leads to the nearly "phase-aligned" multi-wavelength light curves. The emission of peak 1 (P1) and peak 2 (P2) is originated from the Annular Gap region near the null charge surface, while the emission of bridge is mainly originated from the core Gap region. The phase-averaged spectrum and phase-resolved spectra of the Crab pulsar from soft X-ray to TeV band are produced by four components: synchrotron radiation from CR-induced and ICS-induced pairs dominates the X-ray band to soft gamma-ray band (100 eV to 10 MeV); curvature radiation and synchrotron radiation from the primary particles mainly contribute to gamma-ray band (10 MeV to \sim 20 GeV); ICS from the pairs significantly contributes to the TeV gamma-ray band (\sim 20 GeV to 400 GeV). The multi-wavelength pulsed emission from the Crab pulsar has been well modeled with the Annular Gap and core Gap model. To distinguish our single magnetic pole model from two-pole models, the convincing values of the magnetic inclination angle and the viewing angle will play a key role.

  • Annular Gap model for multi-wavelength pulsed emission from young and millisecond pulsars
    Proceedings of the International Astronomical Union, 2012
    Co-Authors: Guojun Qiao
    Abstract:

    The multi-wavelength pulsed emission from young pulsars and millisecond pulsars can be well modeled with the single-pole 3-dimension Annular Gap and core Gap model. To distinguish our single magnetic pole model from two-pole models (e.g. outer Gap model and two-pole caustic model), the convincing values of the magnetic inclination angle and the viewing angle will play a key role.

  • GAMMA-RAY EMISSION FROM THE VELA PULSAR MODELED WITH THE Annular Gap AND THE CORE Gap
    The Astrophysical Journal, 2011
    Co-Authors: Jin-lin Han, Guojun Qiao, C K Chou
    Abstract:

    The Vela pulsar represents a distinct group of γ-ray pulsars. Fermi γ-ray observations reveal that it has two sharp peaks (P1 and P2) in the light curve, with a phase separation of 0.42 and a third peak (P3) in the bridge. The location and intensity of P3 are energy dependent. We use the three-dimensional magnetospheric model for the Annular and core Gaps to simulate the γ-ray light curves and the phase-averaged and phase-resolved spectra. We found that the acceleration electric field along a field line in the Annular Gap region decreases with height. Emission at the high-energy GeV band originates from the synchro-curvature radiation (mainly curvature radiation) of accelerated primary particles, while the synchrotron radiation from secondary particles contributes somewhat to the low-energy γ-ray band (0.1-0.3 GeV). The γ-ray light curve peaks P1 and P2 are generated in the Annular Gap region near the altitude of null charge surface, whereas P3 and the bridge emission are generated in the core Gap region. The intensity and location of P3 at different energy bands depend on the emission altitudes. The radio emission from the Vela pulsar should be generated in a high-altitude narrow region of the Annular Gap, which leads to a radio phase lag of ~0.13 prior to the first γ-ray peak.

  • Magnetosphere Structure and the Annular Gap Model of Pulsars
    Astrophysics and Space Science Proceedings, 2009
    Co-Authors: Guojun Qiao, Kejia Lee, H. G. Wang
    Abstract:

    Pulsar radio and γ-ray emission has been studied for about forty years, yet no elaborated model is present to account for all the emission of pulsars from radio to γ-ray bands. A reasonable emission model should present the mechanism for wide band radiation. The magnetosphere structure and particle acceleration regions are the basis for solving problem, observations are important inputs to establish a reasonable model. In our work, both radio and gamma-ray observations have been considered. We will show how they can limit the radiation locations and radiation mechanisms. The advantages and disadvantages for different radiation locations (such as the polar Gap, the outer Gap and the Annular Gap) are discussed in comparison with observational facts. The Annular Gap model, an joint model for both radio and γ-ray emissions, was proposed recently and reproduce successfully some important observational phenomenon, e.g., bi-drifting. We will also discuss for radio and γ-ray observations of PSR B1055-52, and show that radiations come from the Annular region and the core region. Success in reproducing many observational facts suggest that the Annular Gap is a promising model for pulsar multi-wavelength radiation.

K. J. Lee - One of the best experts on this subject based on the ideXlab platform.

  • the Annular Gap model for γ ray emission from young and millisecond pulsars
    Monthly Notices of the Royal Astronomical Society, 2010
    Co-Authors: G J Qiao, J. L. Han, K. J. Lee
    Abstract:

    Pulsed high-energy radiation from pulsars is not yet completely understood. In this paper, we use the 3D self-consistent Annular Gap model to study light curves for both young and millisecond pulsars (MSPs) observed by the Fermi Gamma-ray Space Telescope. The Annular Gap can generate high-energy emission for short-period pulsars. The Annular Gap regions are so large that they have enough electric potential drop to accelerate charged particles to produce γ-ray photons. For young pulsars, the emission region is from the neutron star surface to about half of the light cylinder radius, and the peak emissivity is in the vicinity of the null charge surface. The emission region for the millisecond pulsars is located much lower than that of the young pulsars. The higher energy γ-ray emission comes from higher altitudes in the magnetosphere. We present the simulated light curves for three young pulsars (the Crab, the Vela and the Geminga) and three millisecond pulsars (PSR J0030+0451, PSR J0218+4232 and PSR J0437-3715) using the Annular Gap model. Our simulations can reproduce the main properties of the observed light curves.

  • The Annular Gap model for gamma-ray emission from young and millisecond pulsars
    Monthly Notices of the Royal Astronomical Society, 2010
    Co-Authors: G J Qiao, J. L. Han, K. J. Lee
    Abstract:

    Pulsed high energy radiation from pulsars is not yet completely understood. In this paper, we use the 3D self-consistent Annular Gap model to study light curves for both young and millisecond pulsars observed by the Fermi Gamma-ray Space Telescope. The Annular Gap can generate high energy emission for short-period pulsars. The Annular Gap regions are so large that they have enough electric potential drop to accelerate charged particles to produce gamma-ray photons. For young pulsars, the emission region is from the neutron star surface to about half of the light cylinder radius, and the peak emissivity is in the vicinity of the null charge surface. The emission region for the millisecond pulsars is located much lower than that of the young pulsars. The higher energy gamma-ray emission comes from higher altitudes in the magnetosphere. We present the simulated light curves for three young pulsars (the Crab, the Vela, the Geminga) and three millisecond pulsars (PSR J0030+0451, PSR J0218+4232, PSR J0437-3715) using the Annular Gap model. Our simulations can reproduce the main properties of observed light curves.

  • the inner Annular Gap for pulsar radiation gamma ray and radio emission
    arXiv: Astrophysics, 2004
    Co-Authors: G J Qiao, H. G. Wang, K. J. Lee, J. L. Han
    Abstract:

    The inner Annular Gap (IAG), a new type of inner Gap whose magnetic field lines intersect the null charge surface (NCS), is proposed to explain $\gamma$-ray and radio emission from pulsars. The IAG can be an important source for high-energy particles. The particles can radiate between the NCS and the IAG. Some observational characteristics in both $\gamma$-ray and radio bands, such as the $\gamma$-ray emission beams of Crab-like, Vela-like and Geminga-like, can be reproduced by numerical method. It is predicted that the view angle $\zeta$ should be larger than the inclination angle ($\zeta>\alpha$), otherwise the $\gamma$-ray radiation will have little possibility to be observed. Whether the inner Annular Gap (or cap) is sparking (or free flow) depends on the surface binding energy of the pulsar. In stead of neutron star models, the scenario of the IAG is favorable for bare strange star models, because bare strange stars can easily satisfy the requisite condition to form an IAG for both pulsars ($\vec{\Omega}\cdot \vec{B} 0$).

G J Qiao - One of the best experts on this subject based on the ideXlab platform.

  • the Annular Gap gamma ray radio emission of pulsars
    International Journal of Modern Physics: Conference Series, 2013
    Co-Authors: G J Qiao, J. L. Han
    Abstract:

    Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the Annular Gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot Gap and outer Gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the Annular Gap would play a very important role. Here we show some observational and theoretical evidences about the Annular Gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.

  • radio to tev phase resolved emission from the crab pulsar the Annular Gap model
    The Astrophysical Journal, 2012
    Co-Authors: G J Qiao, Wei Wang
    Abstract:

    The Crab pulsar is a quite young, famous pulsar that radiates multi-wavelength pulsed photons. The latest detection of GeV and TeV pulsed emission with an unprecedented signal-to-noise ratio, supplied by the powerful telescopes Fermi, MAGIC, and VERITAS, challenges the current popular pulsar models, and can be a valuable discriminator to justify the pulsar high-energy-emission models. Our work is divided into two steps. First, taking reasonable parameters (the magnetic inclination angle {alpha} = 45 Degree-Sign and the view angle {zeta} = 63 Degree-Sign ), we use the latest high-energy data to calculate radio, X-ray, {gamma}-ray, and TeV light curves from a geometric view to obtain crucial information on emission locations. Second, we calculate the phase-averaged spectrum and phase-resolved spectra for the Crab pulsar and take a theoretical justification from a physical view for the emission properties as found in the first step. It is found that a Gaussian emissivity distribution with the peak emission near the null charge surface in the so-called Annular Gap (AG) region gives the best modeled light curves. The pulsed radio, X-ray, {gamma}-ray, and TeV emission are mainly generated from the emission of primary particles or secondary particles with different emission mechanisms in the nearly similar regionmore » of the AG located in the only magnetic pole, which leads to the nearly 'phase-aligned' multi-wavelength light curves. The emission of peak 1 and peak 2 originates from the AG region near the null charge surface, while the emission of the bridge primarily originates from the core Gap (CG) region. The charged particles cannot co-rotate with the pulsar and escape from the magnetosphere, which determines the original flowing primary particles. The acceleration electric field and potential in the AG and CG are huge enough and are in the several tens of neutron star radii. Thus, the primary particles are accelerated to ultra-relativistic energies and produce numerous secondary particles (pairs) in the inner regions of the AG and CG. We emphasize that there are mainly two types of pairs: one is curvature-radiation induced (CR-induced) and the other is inverse-Compton-scattering induced (ICS-induced). The phase-averaged spectrum and phase-resolved spectra from soft X-ray to TeV bands are produced by four components: synchrotron radiation from CR- and ICS-induced pairs dominates the X-ray band to soft {gamma}-ray band (100 eV to 10 MeV); curvature radiation and synchrotron radiation from the primary particles mainly contribute to the {gamma}-ray band (10 MeV to {approx}20 GeV); ICS from the pairs significantly contributes to the TeV {gamma}-ray band ({approx}20-400 GeV). The multi-wavelength pulsed emission from the Crab pulsar can be well modeled with the AG and CG model. To distinguish our single magnetic pole model from two-pole models, the convincing values of the magnetic inclination angle and the viewing angle will play a key role.« less

  • gamma ray emission from the vela pulsar modeled with the Annular Gap and core Gap
    arXiv: High Energy Astrophysical Phenomena, 2011
    Co-Authors: J. L. Han, G J Qiao, C K Chou
    Abstract:

    The Vela pulsar represents a distinct group of {\gamma}-ray pulsars. Fermi {\gamma}-ray observations reveal that it has two sharp peaks (P1 and P2) in the light curve with a phase separation of 0.42 and a third peak (P3) in the bridge. The location and intensity of P3 are energy-dependent. We use the 3D magnetospheric model for the Annular Gap and core Gap to simulate the {\gamma}-ray light curves, phase-averaged and phase-resolved spectra. We found that the acceleration electric field along a field line in the Annular Gap region decreases with heights. The emission at high energy GeV band is originated from the curvature radiation of accelerated primary particles, while the synchrotron radiation from secondary particles have some contributions to low energy {\gamma}-ray band (0.1 - 0.3 GeV). The {\gamma}-ray light curve peaks P1 and P2 are generated in the Annular Gap region near the altitude of null charge surface, whereas P3 and the bridge emission is generated in the core Gap region. The intensity and location of P3 at different energy bands depend on the emission altitudes. The radio emission from the Vela pulsar should be generated in a high-altitude narrow regions of the Annular Gap, which leads to a radio phase lag of ~ 0.13 prior to the first {\gamma}-ray peak.

  • the Annular Gap model for γ ray emission from young and millisecond pulsars
    Monthly Notices of the Royal Astronomical Society, 2010
    Co-Authors: G J Qiao, J. L. Han, K. J. Lee
    Abstract:

    Pulsed high-energy radiation from pulsars is not yet completely understood. In this paper, we use the 3D self-consistent Annular Gap model to study light curves for both young and millisecond pulsars (MSPs) observed by the Fermi Gamma-ray Space Telescope. The Annular Gap can generate high-energy emission for short-period pulsars. The Annular Gap regions are so large that they have enough electric potential drop to accelerate charged particles to produce γ-ray photons. For young pulsars, the emission region is from the neutron star surface to about half of the light cylinder radius, and the peak emissivity is in the vicinity of the null charge surface. The emission region for the millisecond pulsars is located much lower than that of the young pulsars. The higher energy γ-ray emission comes from higher altitudes in the magnetosphere. We present the simulated light curves for three young pulsars (the Crab, the Vela and the Geminga) and three millisecond pulsars (PSR J0030+0451, PSR J0218+4232 and PSR J0437-3715) using the Annular Gap model. Our simulations can reproduce the main properties of the observed light curves.

  • The Annular Gap model for gamma-ray emission from young and millisecond pulsars
    Monthly Notices of the Royal Astronomical Society, 2010
    Co-Authors: G J Qiao, J. L. Han, K. J. Lee
    Abstract:

    Pulsed high energy radiation from pulsars is not yet completely understood. In this paper, we use the 3D self-consistent Annular Gap model to study light curves for both young and millisecond pulsars observed by the Fermi Gamma-ray Space Telescope. The Annular Gap can generate high energy emission for short-period pulsars. The Annular Gap regions are so large that they have enough electric potential drop to accelerate charged particles to produce gamma-ray photons. For young pulsars, the emission region is from the neutron star surface to about half of the light cylinder radius, and the peak emissivity is in the vicinity of the null charge surface. The emission region for the millisecond pulsars is located much lower than that of the young pulsars. The higher energy gamma-ray emission comes from higher altitudes in the magnetosphere. We present the simulated light curves for three young pulsars (the Crab, the Vela, the Geminga) and three millisecond pulsars (PSR J0030+0451, PSR J0218+4232, PSR J0437-3715) using the Annular Gap model. Our simulations can reproduce the main properties of observed light curves.

Jin-lin Han - One of the best experts on this subject based on the ideXlab platform.

  • GAMMA-RAY EMISSION FROM THE VELA PULSAR MODELED WITH THE Annular Gap AND THE CORE Gap
    The Astrophysical Journal, 2011
    Co-Authors: Jin-lin Han, Guojun Qiao, C K Chou
    Abstract:

    The Vela pulsar represents a distinct group of γ-ray pulsars. Fermi γ-ray observations reveal that it has two sharp peaks (P1 and P2) in the light curve, with a phase separation of 0.42 and a third peak (P3) in the bridge. The location and intensity of P3 are energy dependent. We use the three-dimensional magnetospheric model for the Annular and core Gaps to simulate the γ-ray light curves and the phase-averaged and phase-resolved spectra. We found that the acceleration electric field along a field line in the Annular Gap region decreases with height. Emission at the high-energy GeV band originates from the synchro-curvature radiation (mainly curvature radiation) of accelerated primary particles, while the synchrotron radiation from secondary particles contributes somewhat to the low-energy γ-ray band (0.1-0.3 GeV). The γ-ray light curve peaks P1 and P2 are generated in the Annular Gap region near the altitude of null charge surface, whereas P3 and the bridge emission are generated in the core Gap region. The intensity and location of P3 at different energy bands depend on the emission altitudes. The radio emission from the Vela pulsar should be generated in a high-altitude narrow region of the Annular Gap, which leads to a radio phase lag of ~0.13 prior to the first γ-ray peak.

  • The Inner Annular Gap for Pulsar Radiation: γ-Ray and Radio Emission
    The Astrophysical Journal, 2004
    Co-Authors: Guojun Qiao, Kejia Lee, H. G. Wang, Jin-lin Han
    Abstract:

    The inner Annular Gap (IAG), a new type of inner Gap whose magnetic field lines intersect the null charge surface (NCS), is proposed to explain γ-ray and radio emission from pulsars. The IAG can be an important source for high-energy particles. The particles can radiate between the NCS and the IAG. Some observational characteristics in both γ-ray and radio bands, such as the Crab-like, Vela-like, and Geminga-like γ-ray emission beams, can be reproduced by the numerical method. It is predicted that the view angle ζ should be larger than the inclination angle (ζ > α), otherwise the γ-ray radiation will have little possibility to be observed. Whether the IAG (or cap) is sparking (or free flow) depends on the surface binding energy of the pulsar. Instead of neutron star models, the scenario of the IAG is favorable for bare strange star models, because bare strange stars can easily satisfy the requisite condition to form an IAG for both pulsars (Ω 0).