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Post Info TOPIC: HESS J1825-137
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RE: HESS J1825-137
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Title: Multi-Zone Modeling of HESS J1825-137
Authors: Adam Van Etten, Roger W. Romani

The pulsar wind nebula associated with PSR J1826-1334, HESS J1825-137, is a bright very high energy source with an angular extent of ~1 degree 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 modelling, 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) \propto r^{-0.5}. The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar, B(r,t) \propto r^{-0.7} \dot{E}(t)^{½}. Detection of 10 TeV flux ~80 pc from the pulsar requires rapid diffusion of high energy particles with \tau_{esc} ~ 90 (R / 10 pc)² (E_e/100 TeV)^{-1} year, contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement. The model predicts a rather uniform Fermi LAT surface brightness out to ~1 degree from the pulsar, in good agreement with the recently discovered LAT source centred 0.5 degree southwest of PSR J1826-1334 with extension 0.6 ±0.1 degree.

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Title: Suzaku Observation of HESS J1825-137: Discovery of Largely-Extended X-rays near from PSR J1826-1334
Authors: H. Uchiyama, H. Matsumoto, T. G. Tsuru, K. Koyama, A. Bamba

We observed the brightest part of HESS J1825-137 with the Suzaku XIS, and found diffuse X-rays extending at least up to 15' (~ 17 pc) from the pulsar PSR J1826-1334. The spectra have no emission line, and are fitted with an absorbed power-law model. The X-rays, therefore, are likely due to synchrotron emission from a pulsar wind nebula. The photon index near at the pulsar (r<1.5') is 1.7 while those in r=1.5-16 are nearly constant at Gamma=2.0. The spectral energy distribution of the Suzaku and H.E.S.S. results are naturally explained by a combined process; synchrotron X-rays and gamma-rays by the inverse Compton of the cosmic microwave photons by high-energy electrons in a magnetic field of 7 micro G. If the electrons are accelerated at the pulsar, the electrons must be transported over 17 pc in the synchrotron life time of 1900 yr, with a velocity of > 8.8 times 10^3 km s^{-1}.

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PSR B1823-13
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Title: Chandra Observation of PSR B1823-13 and its Pulsar Wind Nebula
Authors: G. G. Pavlov, O. Kargaltsev, W. F. Brisken

We report on an observation of the Vela-like pulsar B1823-13 and its synchrotron nebula with Chandra.The pulsar's spectrum fits a power-law model with a photon index Gamma_PSR=2.4 for the plausible hydrogen column density n_H=10^{22} cm^{-2}, corresponding to the luminosity L_PSR=8*10^{31} ergs s^{-1} in the 0.5-8 keV band, at a distance of 4 kpc. The pulsar radiation likely includes magnetospheric and thermal components, but they cannot be reliably separated because of the small number of counts detected and strong interstellar absorption. The pulsar is surrounded by a compact, 25''x 10'', pulsar wind nebula (PWN) elongated in the east-west direction, which includes a brighter inner component, 7''x 3'', elongated in the northeast-southwest direction. The slope of the compact PWN spectrum is Gamma_comp=1.3, and the 0.5-8 keV luminosity is L_comp~3*10^{32} ergs s^{-1}. The compact PWN is surrounded by asymmetric diffuse emission (extended PWN) seen up to at least 2.4' south of the pulsar, with a softer spectrum (Gamma_ext=1.9), and the 0.5-8 keV luminosity L_ext~10^{33}-10^{34} ergs s^{-1}. We also measured the pulsar's proper motion using archival VLA data: \mu_\alpha=23.0±2.5 mas yr^{-1},
    \mu_\delta=-3.9±3.3 mas yr^{-1}, which corresponds to the transverse velocity v_perp=440 km s^{-1}. The direction of the proper motion is approximately parallel to the elongation of the compact PWN, but it is nearly perpendicular to that of the extended PWN and to the direction towards the centre of the bright VHE gamma-ray source HESS J1825-137, which is likely powered by PSR B1823-13.

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HESS J1825-137
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A team of astronomers from France and South Africa announced the first catalogue of a new type of gamma-ray source, a dozen clouds of “relic” radiation from dead stars that reveal information about the energetic past of these celestial objects.
These findings were presented on Feb. 5, 2007 at the first Gamma Ray Large-Area Space Telescope (GLAST) scientific Symposium meeting in Palo Alto, Calif., by Dr. Arache Djannati-Ataï, an astrophysicist from the Astroparticle & Cosmology (APC) laboratory in Paris, France.
Djannati-Ataï, Drs. Anne Lemière and Régis Terrier, also from the APC, and Prof. Okkie de Jager from Space Unit, North Western University, in Potchefstroom, South Africa, are members of the High Energy Stereoscopic System (H.E.S.S.), a multi-national collaboration that made this finding. H.E.S.S. is a group of four 40-foot telescopes located in Namibia, Africa.

HESS J1825-137
Credit: Astroparticule et Cosmologie (APC), CNRS

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