Ariel 5 hard X-ray observations

1979 ◽  
Vol 366 (1726) ◽  
pp. 295-310
Keyword(s):  
Power Law ◽  
Line Emission ◽  
Galactic Centre ◽  
X Ray ◽  
Upper Limits ◽  
Inverse Compton ◽  
Time Variations ◽  
Cyclotron Line ◽  
Galactic Sources ◽  
The Magnetic Field

Results from the hard X-ray detector (8 cm 2 area, 8° f. w. h. m. field of view, energy range 26–1200 keV) are reviewed in the context of observations by other groups. At least three different classes of galactic sources are studied by this detector. In the first, magnetospheric control of the emission, which seems to be a modified thermal spectrum is dominant. Examples are Cen X-3, Her X-1, A0535 + 26 and GX 301 – 2. So far, only direct evidence on the magnetic field strength from cyclotron line emission has come from Her X-1. In the second, the characteristics are a power law spectrum extending to over about 200 keV and fast a periodic time variations with little evidence of the presence of strong magnetic fields. Inverse Compton production of the X-ray photons seems important here. Examples are Cyg X-1, A0620–00, Ser X-1 and perhaps Cir X-1, although this last object suffers periodic heavy low energy absorption. The third is the white dwarf emitter class, e. g. AM Herculis and possibly AM Canum Venaticorum; sources in this class surprisingly tend to exhibit a power law rather than a thermal spectral shape. Sco X-1 and Sco X-2 are perhaps a fourth class of object. Hard X-ray upper limits obtained from a survey of COS-B γ -ray source positions are discussed. Further attempts to find hard X-ray emission from the galactic centre X-ray burst sources are mentioned.

scholarly journals G0.173−0.42: an X-ray and radio magnetized filament near the galactic centre

2020 ◽  
Vol 500 (3) ◽  
pp. 3142-3150
Author(s):  
F Yusef-Zadeh ◽  
M Wardle ◽  
C Heinke ◽  
I Heywood ◽  
R Arendt ◽  
...  
Keyword(s):  
Galactic Centre ◽  
Physical Interaction ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Structural Details ◽  
Field Lines ◽  
The Magnetic Field ◽  
Relativistic Particles

ABSTRACT The detection of an X-ray filament associated with the radio filament G0.173–0.42 adds to four other non-thermal radio filaments with X-ray counterparts, amongst the more than 100 elongated radio structures that have been identified as synchrotron-emitting radio filaments in the inner couple of degrees of the Galactic centre. The synchrotron mechanism has also been proposed to explain the emission from X-ray filaments. However, the origin of radio filaments and the acceleration sites of energetic particles to produce synchrotron emission in radio and X-rays remain mysterious. Using MeerKAT, VLA, Chandra, WISE, and Spitzer, we present structural details of G0.173–0.42 which consists of multiple radio filaments, one of which has an X-ray counterpart. A faint oblique radio filament crosses the radio and X-ray filaments. Based on the morphology, brightening of radio and X-ray intensities, and radio spectral index variation, we argue that a physical interaction is taking place between two magnetized filaments. We consider that the reconnection of the magnetic field lines at the interaction site leads to the acceleration of particles to GeV energies. We also argue against the synchrotron mechanism for the X-ray emission due to the short ∼30 yr lifetime of TeV relativistic particles. Instead, we propose that the inverse Compton scattering mechanism is more likely to explain the X-ray emission by upscattering of seed photons emitted from a 106  L⊙ star located at the northern tip of the X-ray filament.

scholarly journals Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

2020 ◽  
Vol 497 (4) ◽  
pp. 4704-4717
Author(s):  
Chong Ge ◽  
Ruo-Yu Liu ◽  
Ming Sun ◽  
Heng Yu ◽  
Lawrence Rudnick ◽  
...  
Keyword(s):  
Power Law ◽  
Electron Spectrum ◽  
Galaxy Cluster ◽  
X Ray ◽  
Cold Fronts ◽  
Inverse Compton ◽  
Galaxy Kinematics ◽  
The Magnetic Field ◽  
Primary Cluster ◽  
Shock Fronts

ABSTRACT We present the results of deep Chandra and XMM–Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic (RR). The temperature and metallicity maps show clear evidence of a merger between the western subcluster (SC) and the primary cluster (PC). We detect five X-ray surface brightness edges. Three of them near the cluster centre are cold fronts (CFs): CF1 is associated with the infalling SC; CF2 is located in the east of the PC; and CF3 is located to the west of the PC core. The other two edges at cluster outskirts are shock fronts (SFs): SF1 near the RR in the NW has Mach numbers derived from the temperature and the density jumps, respectively, of MT = 1.62 ± 0.12 and Mρ = 1.23 ± 0.06; SF2 in the SE has MT = 1.54 ± 0.05 and Mρ = 1.16 ± 0.13. In the region of the RR, there is no evidence for the correlation between X-ray and radio substructures, from which we estimate an upper limit for the inverse-Compton emission, and therefore set a lower limit on the magnetic field (∼ 450 kpc from PC centre) of B > 1.0 μG for a single power-law electron spectrum or B > 0.4 μG for a broken power-law electron spectrum. We propose a merger scenario including a PC, an SC, and a group. Our merger scenario accounts for the X-ray edges, diffuse radio features, and galaxy kinematics, as well as projection effects.

scholarly journals Properties of individual X-ray sources: (Invited discourse)

1970 ◽  
Vol 37 ◽  
pp. 59-80
Author(s):  
Laurence E. Peterson
Keyword(s):  
Power Law ◽  
Crab Nebula ◽  
Optical Observations ◽  
X Rays ◽  
X Ray ◽  
Upper Limits ◽  
Time Variations ◽  
Γ Rays ◽  
The Crab Nebula

Observations to determine the spectra and time variations of hard X-rays from cosmic sources have been made from balloons and from the OSO-III satellite. These data have been obtained using actively collimated scintillation counters with apertures between 6 and 24° FWHM, areas between 10 and 50 cm2 and which operate over the 10–300 keV range. The Crab Nebula has been observed on three occasions over a 22-month period between September 1965 and July 1967. The power law spectrum has a number index of 2.0 ± 0.1. No long-term changes were observed over the 30–100 keV range with a limit at 3%/yr. A balloon search with a 10 cm2 Ge(Li) detector for X-ray lines at 62.5 keV, 110 keV and 180 keV due to heavy element radioactive decays which would be produced in the initial Crab explosion based on the Cf254 hypothesis has resulted in upper limits at about 10−3 γ-rays cm2-sec. This is about a factor of 20 above the predicted levels. Simultaneous X-ray and optical observations of SCO XR-1 from OSO-III confirm that X-ray and optical flaring are indeed coincident phenomena, and that although the X-ray intensity increases about a factor of two during the flare, the equivalent temperature of the excess radiation is nearly the same as that of the quiescent object. Upper limits, 95% confidence, on the flux of M-87 at 40 keV have been obtained. These are inconsistent with the flux of 1.2 × 10−4 photons/cm2-sec-keV reported in the literature. CYG X-1 has been observed to have a power law of number index 2.0 ± 0.2. The OSO-III has observed a number of sources in the southern skies including NOR XR-2 and the variable source Centaurus XR-2.

scholarly journals X-ray Properties of 3C 111: Separation of Primary Nuclear Emission and Jet Continuum

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 219
Author(s):  
Elena Fedorova ◽  
B.I. Hnatyk ◽  
V.I. Zhdanov ◽  
A. Del Popolo
Keyword(s):  
Accretion Disk ◽  
Power Law ◽  
Line Emission ◽  
High Energy ◽  
Power Law Model ◽  
X Ray ◽  
Additional Information ◽  
Observational Dataset ◽  
Simple Power ◽  
Photon Index

3C111 is BLRG with signatures of both FSRQ and Sy1 in X-ray spectrum. The significant X-ray observational dataset was collected for it by INTEGRAL, XMM-Newton, SWIFT, Suzaku and others. The overall X-ray spectrum of 3C 111 shows signs of a peculiarity with the large value of the high-energy cut-off typical rather for RQ AGN, probably due to the jet contamination. Separating the jet counterpart in the X-ray spectrum of 3C 111 from the primary nuclear counterpart can answer the question is this nucleus truly peculiar or this is a fake “peculiarity” due to a significant jet contribution. In view of this question, our aim is to estimate separately the accretion disk/corona and non-thermal jet emission in the 3C 111 X-ray spectra within different observational periods. To separate the disk/corona and jet contributions in total continuum, we use the idea that radio and X-ray spectra of jet emission can be described by a simple power-law model with the same photon index. This additional information allows us to derive rather accurate values of these contributions. In order to test these results, we also consider relations between the nuclear continuum and the line emission.

scholarly journals Cyclotron lines in highly magnetized neutron stars

2019 ◽  
Vol 622 ◽  
pp. A61 ◽  
Author(s):  
R. Staubert ◽  
J. Trümper ◽  
E. Kendziorra ◽  
D. Klochkov ◽  
K. Postnov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Direct Measurement ◽  
Resonant Scattering ◽  
Electron Cyclotron ◽  
X Ray ◽  
Cyclotron Line ◽  
The Magnetic Field ◽  
Proton Cyclotron

Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (end 2018), we list 35 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

Evidence for strong cyclotron line emission in the hard X-ray spectrum of Hercules X-1

1978 ◽  
Vol 219 ◽  
pp. L105 ◽  
Author(s):  
J. Truemper ◽  
W. Pietsch ◽  
C. Reppin ◽  
W. Voges ◽  
R. Staubert ◽  
...  
Keyword(s):  
Line Emission ◽  
X Ray ◽  
Cyclotron Line

scholarly journals Iron Line Emission from NGC1068

1989 ◽  
Vol 134 ◽  
pp. 167-172
Author(s):  
Katsuji Koyama
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Equivalent Width ◽  
Line Emission ◽  
X Rays ◽  
Iron Line ◽  
X Ray ◽  
Central Engine ◽  
Photon Index ◽  
The Continuum

X-ray emission in the 2–10 keV energy range was observed with the Ginga satellite from the Seyfert 2 galaxy NGC1068. The continuum spectrum can be described by a power-law of photon index about 1.5. An intense iron line at 6.5 keV with an equivalent width of 1.3 keV was clearly noticed. The X-ray flux was about 6 × 10 −12 erg/sec/cm2 or 3 × 1041 erg/sec, assuming a distance of 22 Mpc. The observed spectrum is consistent with the scattering and reprocessing of X-rays by the gas surrounding the central engine. With this picture we estimate that the X-ray flux of the central engine is about 1043 - 1044 erg/sec, a typical value for a Seyfert 1 galaxy.

scholarly journals On Special Features of Non-Thermal Solar X Radiation above 10 keV

1972 ◽  
Vol 14 ◽  
pp. 761-762
Author(s):  
G. Elwert ◽  
E. Haug
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Power Law ◽  
Impulsive Phase ◽  
X Rays ◽  
Energetic Electrons ◽  
X Ray ◽  
Preferred Direction ◽  
Field Lines ◽  
The Magnetic Field

The polarization and angular distribution of solar hard X radiation above 10 keV was calculated under the assumption that the X rays originate as bremsstrahlung from energetic electrons moving in a preferred direction. The source electrons are supposed to have a power-law spectrum. These conditions are to be expected in the impulsive phase of an X-ray burst. The spiral orbits of the electrons around the magnetic field lines are taken into account.

scholarly journals Observations of AGN with the Extreme Ultraviolet Explorer

1994 ◽  
Vol 159 ◽  
pp. 105-110
Author(s):  
Herman L. Marshall
Keyword(s):  
Power Law ◽  
Extreme Ultraviolet ◽  
Active Galaxies ◽  
Spectral Features ◽  
Bl Lac Objects ◽  
X Ray ◽  
Difficult Time ◽  
Bl Lac ◽  
First Results ◽  
Galactic Sources

The first results from surveys performed in the extreme ultraviolet (EUV) will be described in the context of studies of active galaxies and BL Lac objects. About a dozen extra-galactic sources are known so far to emit sufficient EUV radiation that they are detectable even through the Galactic interstellar medium. These results are interpreted in the context of a model of EUV or soft X-ray excesses in the case of AGN. In the case of BL Lac objects, the detections indicate that the steep soft X-ray power law spectra continue into the EUV and that there is little intrinsic gas. Finally, there now exists EUV spectra from the Extreme Ultraviolet Explorer for one BL Lac, PKS 2155-304 and two AGN: Mk 478 and NGC 5548. The spectra show no significant spectral features; for AGN, it indicates that optically thin and emission line models may have a difficult time explaining the EUV and soft X-ray bumps.

scholarly journals Statistics of Radio-X-Ray Emission and Magnetic Fields in the Intergalactic Medium

1990 ◽  
Vol 139 ◽  
pp. 414-415
Author(s):  
Hitoshi Hanami
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Magnetic Fields ◽  
Intergalactic Medium ◽  
Relativistic Electrons ◽  
X Ray ◽  
Cooling Flows ◽  
Hot Plasma ◽  
Inverse Compton ◽  
The Magnetic Field

X-ray observations have demonstrated that the intergalactic medium in many clusters (cf. Coma, Perseus) contains a thin, hot plasma that may be produced by the accretion process in the gravitational potential of clusters with radiative cooling; this is usually called “cooling flows” (Fabian, Nulsen, and Canizares 1984; Sarazin 1986). On the other hand, the existence of radio halos in some clusters has been reported (Coma: Jaffe, Perola, and Valentijn 1976; A401: Roland et al. 1981). In addition, many elliptical galaxies in the center of clusters are also strong synchrotron radio sources. These radio emissions provide evidence for large amounts of relativistic electrons associated with the active phenomena in or around these galaxies and clusters. We can estimate the values or limits on the magnetic field in the cluster from the limits on the inverse Compton X-ray emission with the synchrotron radio emission (cf. Jaffe 1980). The intracluster field strength Bo is roughly 1 μG. It has been suggested that the influence of cosmic rays and magnetic fields is important for the properties and dynamics of the intercluster medium (Böhringer and Morfill 1988; Soker and Sarazin 1989). If cooling flows are real, this inward flow can impede the escape of the cosmic rays from the central galaxies in clusters and enhance the magnetic field. The confinement of the cosmic rays and the magnetic field in the center of clusters affects the gas of the intracluster medium.

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