scholarly journals Energy dependent morphology of the pulsar wind nebula HESS J1825-137 with Fermi-LAT

2020 ◽  
Vol 640 ◽  
pp. A76
Author(s):  
G. Principe ◽  
A. M. W. Mitchell ◽  
S. Caroff ◽  
J. A. Hinton ◽  
R. D. Parsons ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Particle Transport ◽  
Morphological Study ◽  
Emission Region ◽  
Transport Mechanisms ◽  
Strong Energy ◽  
Pulsar Wind ◽  
Energy Dependent ◽  
Extended Emission ◽  
Centroid Location

Aims. Taking advantage of more than 11 years of Fermi-LAT data, we perform a new and deep analysis of the pulsar wind nebula (PWN) HESS J1825-137. Combining this analysis with recent H.E.S.S. results we investigate and constrain the particle transport mechanisms at work inside the source as well as the system evolution. Methods. The PWN is studied using 11.6 years of Fermi-LAT data between 1 GeV and 1 TeV. In particular, we present the results of the spectral analysis and the first energy-resolved morphological study of the PWN HESS J1825-137 at GeV energies, which provide new insights into the γ-ray characteristics of the nebula. Results. An optimised analysis of the source returns an extended emission region larger than 2°, corresponding to an intrinsic size of about 150 pc, making HESS J1825-137 the most extended γ-ray PWN currently known. The nebula presents a strong energy dependent morphology within the GeV range, moving from a radius of ∼1.4° below 10 GeV to a radius of ∼0.8° above 100 GeV, with a shift in the centroid location. Conclusions. Thanks to the large extension and peculiar energy-dependent morphology, it is possible to constrain the particle transport mechanisms inside the PWN HESS J1825-137. Using the variation of the source extension and position, as well as the constraints on the particle transport mechanisms, we present a scheme for the possible evolution of the system. Finally, we provide an estimate of the electron energy density and we discuss its nature in the PWN and TeV halo-like scenario.

scholarly journals On the unusually large spatial extent of the TeV nebula HESS J1825−137: implication from the energy-dependent morphology

2020 ◽  
Vol 494 (2) ◽  
pp. 2618-2627
Author(s):  
Ruo-Yu Liu ◽  
Huirong Yan
Keyword(s):  
Particle Transport ◽  
Transport Mechanism ◽  
High Energy ◽  
Spatial Extent ◽  
Model Parameters ◽  
History Of ◽  
Stereoscopic System ◽  
Pulsar Wind ◽  
Energy Dependent

ABSTRACT Deep observation of the High Energy Stereoscopic System (HESS) on the most extended pulsar wind nebula HESS J1825−137 reveals an enhanced energy-dependent morphology, providing useful information on the particle transport mechanism in the nebula. We find that the energy-dependent morphology is consistent with a diffusion-dominated transport of electrons/positrons. It provides an alternative possible interpretation for the unusually large spatial extent (i.e. ${\gtrsim} 100$ pc) of the nebula, which could then be attributed to the diffusion of escaping electrons/positrons from a compact plerion. The influence of various model parameters on the energy-dependent extent of the nebula is studied in the diffusion-dominated scenario. We also show that the energy-dependent morphology of the nebula may also be used to study the spin-down history of the pulsar.

scholarly journals Particle transport within the pulsar wind nebula HESS J1825–137

2019 ◽  
Vol 621 ◽  
pp. A116 ◽  
Author(s):  
◽  
H. Abdalla ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
...  
Keyword(s):  
Particle Transport ◽  
Crab Nebula ◽  
Spectral Characteristics ◽  
High Energy ◽  
Spectral Variation ◽  
Spatially Resolved ◽  
Pure Diffusion ◽  
Very High Energy ◽  
Pulsar Wind ◽  
Energy Dependent

Context. We present a detailed view of the pulsar wind nebula (PWN) HESS J1825–137. We aim to constrain the mechanisms dominating the particle transport within the nebula, accounting for its anomalously large size and spectral characteristics. Aims. The nebula was studied using a deep exposure from over 12 years of H.E.S.S. I operation, together with data from H.E.S.S. II that improve the low-energy sensitivity. Enhanced energy-dependent morphological and spatially resolved spectral analyses probe the very high energy (VHE, E > 0.1 TeV) γ-ray properties of the nebula. Methods. The nebula emission is revealed to extend out to 1.5° from the pulsar, ~1.5 times farther than previously seen, making HESS J1825–137, with an intrinsic diameter of ~100 pc, potentially the largest γ-ray PWN currently known. Characterising the strongly energy-dependent morphology of the nebula enables us to constrain the particle transport mechanisms. A dependence of the nebula extent with energy of R ∝ Eα with α = −0.29 ± 0.04stat ± 0.05sys disfavours a pure diffusion scenario for particle transport within the nebula. The total γ-ray flux of the nebula above 1 TeV is found to be (1.12 ± 0.03stat ± 0.25sys) × 10−11 cm−2 s−1, corresponding to ~64% of the flux of the Crab nebula. Results. HESS J1825–137 is a PWN with clearly energy-dependent morphology at VHE γ-ray energies. This source is used as a laboratory to investigate particle transport within intermediate-age PWNe. Based on deep observations of this highly spatially extended PWN, we produce a spectral map of the region that provides insights into the spectral variation within the nebula.

scholarly journals Energy-dependent morphology of the pulsar wind nebula HESS J1825-137 seen by the Fermi-LAT

2019 ◽  
Author(s):  
Giacomo Principe ◽  
Alison M.W. Mitchell ◽  
Jim Hinton ◽  
Daniel Parson ◽  
Sami Caroff ◽  
...  
Keyword(s):  
Pulsar Wind ◽  
Energy Dependent

Energy-dependent nebula extent and spatially resolved spectra of the pulsar wind nebula 3C 58

2020 ◽  
Vol 498 (2) ◽  
pp. 1911-1919
Author(s):  
Fang-Wu Lu ◽  
Quan-Gui Gao ◽  
Li Zhang
Keyword(s):  
Surface Brightness ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spatial Variations ◽  
Spectral Energy ◽  
X Ray ◽  
Spatially Resolved ◽  
Photon Index ◽  
Pulsar Wind ◽  
Energy Dependent

ABSTRACT 3C 58 is a pulsar wind nebula (PWN) that shows an interesting energy-dependent nebula extent and spatial variations of the photon index and surface brightness in the X-ray band. These observations provide useful information with which to study the spatially dependent radiative cooling of electrons and the energy-dependent transport mechanisms within the nebula. In this paper, the energy-dependent nebula extent and spatially resolved spectra of this PWN are investigated in the framework of a spatially dependent particle transport model. The observations of the nebula, including the photon spectral energy distribution, spatial variations of the X-ray spectrum, and measurements of the nebula extent, can be naturally explained in this model. Our results show that the energy-dependent nebula extent favours an advection–diffusion scenario with advection-dominated transport, and the variations of the nebula extent with energy in the X-ray band can be attributed to the cooling losses of high-energy electrons affected by synchrotron burn-off. Particle diffusion plays an important role in modifying the spatial variations of the photon index and surface brightness in the X-ray band. The radial extents of the nebula at radio, GeV and TeV energies are predicted by the model, indicating that the nebula extent of 3C 58 varies with energy in these bands. The analyses show that the dependence of the adiabatic cooling rate and synchrotron radiation on the spectral index of injected particles is important for changing the nebula extent at different energies.

scholarly journals Ultracompact H ii regions with extended emission: the complete view

2019 ◽  
Vol 492 (1) ◽  
pp. 895-914 ◽  
Author(s):  
Eduardo de la Fuente ◽  
Alicia Porras ◽  
Miguel A Trinidad ◽  
Stanley E Kurtz ◽  
Simon N Kemp ◽  
...  
Keyword(s):  
Morphological Study ◽  
Galactic Plane ◽  
Radio Continuum ◽  
H Ii Regions ◽  
Direct Connection ◽  
Infrared Excess ◽  
Very Large Array ◽  
Bubble Structure ◽  
Colour Composite ◽  
Extended Emission

ABSTRACT In this paper, we present the results of a morphological study performed on a sample of 28 ultracompact H ii (UC H ii) regions located near extended free–free emission, using radio continuum (RC) observations at 3.6 cm with the C and D Very Large Array (VLA) configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA configurations, we compiled a final catalogue of 21 UC H ii regions directly connected with the surrounding extended emission (EE). The observed morphology of most of the UC H ii regions in RC emission is irregular (single- or multipeaked sources) and resembles a classical bubble structure in the Galactic plane with well-defined cometary arcs. RC images superimposed on colour composite Spitzer images reinforce the assignations of direct connection by the spatial coincidence between the UC components and regions of saturated 24 μm emission. We also find that the presence of EE may be crucial to understand the observed infrared excess because an underestimation of ionizing Lyman photons was considered in previous works (e.g. Wood & Churchwell; Kurtz, Churchwell & Wood).

scholarly journals Probing the origin of the off-pulse emission from the pulsars B0525+21 and B2045−16

2019 ◽  
Vol 627 ◽  
pp. L2 ◽  
Author(s):  
B. Marcote ◽  
Y. Maan ◽  
Z. Paragi ◽  
A. Keimpema
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Bow Shock ◽  
Noise Levels ◽  
Pulsar Wind Nebulae ◽  
Pulse Emission ◽  
Upper Limits ◽  
Pulsar Wind ◽  
Very High ◽  
Extended Emission

Pulsars typically exhibit radio emission in the form of narrow pulses originated from confined regions of their magnetospheres. A potential presence of magnetospherically originated emission outside this region, the so-called off-pulse emission, would challenge the existing theories. Detection of significant off-pulse emission has been reported so far from only two pulsars: B0525+21 and B2045−16 at 325 and 610 MHz, respectively. However, the nature of this newly uncovered off-pulse emission remains unclear. To probe its origin we conducted very-high-resolution radio observations of B0525+21 and B2045−16 with the European VLBI Network (EVN) at 1.39 GHz. Whereas the pulsed emission is detected at a level consistent with previous observations, we report an absence of any off-pulse emission above 42 and 96 μJy beam−1 (three times the rms noise levels) for B0525+21 and B2045−16, respectively. Our stringent upper limits imply the off-pulse emission to be less than 0.4 and 0.3% of the period-averaged pulsed flux density, i.e., much fainter than the previously suggested values of 1−10%. Since the EVN data are most sensitive to extremely compact angular scales, our results suggest a non-magnetospheric origin for the previously reported off-pulse emission. The presence of extended emission that is resolved out to these milliarcsecond scales still remains plausible. In this case, we constrain the emission to arise from structures with sizes of ∼(0.61−19) × 103 au for B0525+21 and ∼(0.48−8.3) × 103 au for B2045−16. These constraints might indicate that the two pulsars are accompanied by compact bow-shock pulsar wind nebulae. Future observations probing intermediate angular scales (∼0.1−5 arcsec) will help to clarify the actual origin of the off-pulse emission.

scholarly journals Diffusion and advection model for particle transport in young pulsar wind nebulae

2012 ◽  
Vol 8 (S291) ◽  
pp. 265-268
Author(s):  
Xiaping Tang ◽  
Roger A. Chevalier
Keyword(s):  
Spectral Index ◽  
Particle Transport ◽  
Crab Nebula ◽  
Outer Boundary ◽  
Outer Part ◽  
Pulsar Wind Nebulae ◽  
Pure Diffusion ◽  
Pulsar Wind ◽  
Kink Instability ◽  
The Crab Nebula

AbstractThe magnetohydrodynamic (MHD) model for young pulsar wind nebulae (PWN) has been successful in reproducing many features of the nebulae. The model is characterized by a termination shock (TS) between the PWN and unshocked pulsar wind. Relativistic particles are injected at the TS and follow an advective flow to the outer boundary. However, toroidal structure of well studied young PWN like the Crab Nebula, 3C 58 and G21.5-0.9 is only present in the region close to the TS. In the outer parts of the nebulae, filamentary and loop-like structure is observed. Also, the radial variation of spectral index due to synchrotron losses is smoother than expected in the MHD flow model. We find that a pure diffusion model with energy independent diffusion and a transmitting boundary can reproduce the basic data on nebular size and spectral index variation for the Crab, 3C 58, and G21.5-0.9. Energy dependent diffusion is also discussed. Power law variations of the coefficient with energy are degenerate with variation in the input particle energy distribution index in the steady state case. Monte Carlo simulations of particle transport with both diffusion and advection for the Crab nebula and 3C 58 suggest a picture in which advection dominates the inner part of the PWN where toroidal structure is clearly present. Diffusion dominates the outer part of the PWN where filamentary and loop-like structure is observed. The source of the chaotic field is uncertain, but may be related to Rayleigh-Taylor instability at the outer boundary of young nebulae and/or the kink instability of the toroidal magnetic field.

scholarly journals PARTICLE TRANSPORT IN YOUNG PULSAR WIND NEBULAE

2012 ◽  
Vol 752 (2) ◽  
pp. 83 ◽  
Author(s):  
Xiaping Tang ◽  
Roger A. Chevalier
Keyword(s):  
Particle Transport ◽  
Pulsar Wind Nebulae ◽  
Pulsar Wind

scholarly journals Constraining models of the pulsar wind nebula in SNR G0.9+0.1 via simulation of its detection properties using the Cherenkov Telescope Array

2020 ◽  
Vol 499 (3) ◽  
pp. 3494-3509
Author(s):  
M Fiori ◽  
L Zampieri ◽  
A Burtovoi ◽  
P Caraveo ◽  
L Tibaldo
Keyword(s):  
Systematic Errors ◽  
High Energy ◽  
Emission Region ◽  
Telescope Array ◽  
Instrument Response Function ◽  
Cherenkov Telescope ◽  
Cutoff Energy ◽  
Spectral Models ◽  
Pulsar Wind ◽  
The Impact

ABSTRACT SNR G0.9+0.1 is a well-known source in the direction of the Galactic Centre composed by a Supernova Remnant (SNR) and a Pulsar Wind Nebula (PWN) in the core. We investigate the potential of the future Cherenkov Telescope Array (CTA), simulating observations of SNR G0.9 + 0.1. We studied the spatial and spectral properties of this source and estimated the systematic errors of these measurements. The source will be resolved if the very high-energy emission region is bigger than ∼0.65′. It will also be possible to distinguish between different spectral models and calculate the cutoff energy. The systematic errors are dominated by the Instrument Response Function instrumental uncertainties, especially at low energies. We computed the evolution of a young PWN inside an SNR using a one-zone time-dependent leptonic model. We applied the model to the simulated CTA data and found that it will be possible to accurately measure the cutoff energy of the γ-ray spectrum. Fitting of the multiwavelength spectrum will allow us to constrain also the magnetization of the PWN. Conversely, a pure power-law spectrum would rule out this model. Finally, we checked the impact of the spectral shape and the energy density of the Inter-Stellar Radiation Fields on the estimate of the parameters of the PWN, finding that they are not significantly affected.

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