اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدProbing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S
98
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae (PWNe), and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) $gamma$-ray emission (HESS $mathrm{J0835mhyphen 455}$) was discovered using the H.E.S.S. experiment in 2004. The VHE $gamma$-ray emission was found to be coincident with a region of X-ray emission discovered with ${it ROSAT}$ above 1.5 keV (the so-called textit{Vela X cocoon}): a filamentary structure extending southwest from the pulsar to the centre of Vela X. A deeper observation of the entire Vela X nebula region, also including larger offsets from the cocoon, has been performed with H.E.S.S. This re-observation was carried out in order to probe the extent of the non-thermal emission from the Vela X region at TeV energies and to investigate its spectral properties. In order to increase the sensitivity to the faint $gamma$-ray emission from the very extended Vela X region, a multivariate analysis method combining three complementary reconstruction techniques of Cherenkov-shower images is applied for the selection of $gamma$-ray events. The analysis is performed with the On/Off background method, which estimates the background from separate observations pointing away from Vela X; towards regions free of $gamma$-ray sources but with comparable observation conditions. The $gamma$-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE $gamma$-ray emission from the PWN HESS $mathrm{J0835mhyphen 455}$ is statistically significant over a region of radius 1.2$^{circ}$ around the position $alpha$ = 08$^{mathrm{h}}$ 35$^{mathrm{m}}$ 00$^{mathrm{s}}$, $delta$ = -45$^{circ}$ 36$^{mathrm{prime}}$ 00$^{mathrm{prime}mathrm{prime}}$ (J2000).
قيم البحث
اقرأ أيضاً
The High Energy Stereoscopic System (H.E.S.S.) is an array of four imaging atmospheric-Cherenkov telescopes located in Namibia and designed to detect extensive air showers initiated by gamma-rays in the very-high-energy domain. It is an ideal instrum
ent for surveying the Galactic plane in search of new sources, thanks to its location in the Southern Hemisphere, its excellent sensitivity, and its large field-of-view. The efforts of the H.E.S.S. Galactic Plane Survey, the first comprehensive survey of the inner Galaxy at TeV energies, have contributed to the discovery of an unexpectedly large and diverse population of over 60 sources of VHE gamma rays within its current range of l=250 to 65 degrees in longitude and |b|<=3.5 degrees in latitude. The population of VHE gamma-ray emitters is dominated by the pulsar wind nebula and supernova remnant source classes, although nearly a third remain unidentified or confused. The sensitivity of H.E.S.S. to sources in the inner Galaxy has improved significantly over the past two years, from continued survey observations, dedicated follow-up observations of interesting source candidates, and from the development of advanced methods for discrimination of gamma-ray-induced showers from the dominant background of hadron-induced showers. The latest maps of the Galaxy at TeV energies will be presented, and a few remarkable new sources will be highlighted.
Vela Jr. (RX J0852.0$-$4622) is one of just a few known supernova remnants (SNRs) with a resolved shell across the whole electromagnetic spectrum from radio to very-high-energy ($>100$ GeV; VHE) gamma-rays. Its proximity and large size allow for deta
iled spatially resolved observations of the source making Vela Jr. one of the primary sources used for the study of particle acceleration and emission mechanisms in SNRs. High-resolution X-ray observations reveal a steepening of the spectrum toward the interior of the remnant. In this study we aim for a self-consistent radiation model of Vela Jr. which at the same time would explain the broadband emission from the source and its intensity distribution. We solve the full particle transport equation combined with the high-resolution 1D hydrodynamic simulations (using Pluto code) and subsequently calculate the radiation from the remnant. The equations are solved in the test particle regime. We test two models for the magnetic field profile downstream of the shock: damped magnetic field which accounts for the damping of strong magnetic turbulence downstream, and transported magnetic field. Neither of these scenarios can fully explain the observed radial dependence of the X-ray spectrum under spherical symmetry. We show, however, that the softening of the spectrum and the X-ray intensity profile can be explained under the assumption that the emission is enhanced within a cone.
The W49 region hosts two bright radio sources: the star forming region W49A and the supernova remnant W49B. The 10^6 M_odot Giant Molecular Cloud W49A is one of the most luminous giant radio HII regions in our Galaxy and hosts several active, high-ma
ss star formation sites. The mixed-morphology supernova remnant W49B has one of the highest surface brightness in radio of all the SNRs of this class in our Galaxy and is one of the brightest ejecta-dominated SNRs in X-rays. Infrared observations evidenced that W49B is interacting with molecular clouds and Fermi recently reported the detection of a coincident bright, high-energy gamma-ray source. Observations by the H.E.S.S. telescope array resulted in the significant detection of VHE gamma-ray emission from the W49 region, compatible with VHE emission from the SNR W49B. The results, the morphology and the origin of the VHE emission are presented in the multi-wavelength context and the implications on the origin of the signal are discussed.
Radio continuum observations detect non-thermal synchrotron and thermal bremsstrahlung radiation. Separation of the two different emission components is crucial to study the properties of diffuse interstellar medium. The Cygnus X region is one of the
most complex areas in the radio sky which contains a number of massive stars and HII regions on the diffuse thermal and non-thermal background. More supernova remnants are expected to be discovered. We aim to develop a method which can properly separate the non-thermal and thermal radio continuum emission and apply it to the Cygnus X region. The result can be used to study the properties of different emission components and search for new supernova remnants in the complex. Multi-frequency radio continuum data from large-scale surveys are used to develop a new component separation method. Spectral analysis is done pixel by pixel for the non-thermal synchrotron emission with a realistic spectral index distribution and a fixed spectral index of beta = -2.1 for the thermal bremsstrahlung emission. With the new method, we separate the non-thermal and thermal components of the Cygnus X region at an angular resolution of 9.5arcmin. The thermal emission component is found to comprise 75% of the total continuum emission at 6cm. Thermal diffuse emission, rather than the discrete HII regions, is found to be the major contributor to the entire thermal budget. A smooth non-thermal emission background of 100 mK Tb is found. We successfully make the large-extent known supernova remnants and the HII regions embedded in the complex standing out, but no new large SNRs brighter than Sigma_1GHz = 3.7 x 10^-21 W m^-2 Hz^-1 sr^-1 are found.
We report on observations of very high-energy gamma rays from the shell-type supernova remnant Cassiopeia A with the VERITAS stereoscopic array of four imaging atmospheric Cherenkov telescopes in Arizona. The total exposure time for these observation
s is 22 hours, accumulated between September and November of 2007. The gamma-ray source associated with the SNR Cassiopeia A was detected above 200 GeV with a statistical significance of 8.3 s.d. The estimated integral flux for this gamma-ray source is about 3% of the Crab-Nebula flux. The photon spectrum is compatible with a power law dN/dE ~ E^(-Gamma) with an index Gamma = 2.61 +/- 0.24(stat) +/- 0.2(sys). The data are consistent with a point-like source. We provide a detailed description of the analysis results, and discuss physical mechanisms that may be responsible for the observed gamma-ray emission.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
