scholarly journals Impulsive radio and hard X-ray emission from an M-class flare

2018 ◽  
Vol 615 ◽  
pp. A48
Author(s):  
Ping Zhang ◽  
Yang Guo ◽  
Lu Wang ◽  
Siming Liu
Keyword(s):  
Power Law ◽  
Impulsive Phase ◽  
High Energy ◽  
X Rays ◽  
Power Law Model ◽  
Power Law Distribution ◽  
Energetic Electrons ◽  
X Ray ◽  
Nonlinear Force ◽  
Class Flare

Context. Impulsive radio and hard X-ray emission from large solar flares are usually attributed to a hard distribution of high-energy electrons accelerated in the energy dissipation process of magnetic reconnection. Aims. We report the detection of impulsive radio and hard X-ray emissions produced by a population of energetic electrons with a very soft distribution in an M-class flare: SOL2015-08-27T05:45 . Methods. The absence of impulsive emission at 34 GHz and hard X-ray emission above 50 keV and the presence of distinct impulsive emission at 17 GHz and lower frequencies and in the 25–50 keV X-ray band imply a very soft distribution of energetic electrons producing the impulsive radio emission via the gyro-synchrotron process, and impulsive X-rays via bremsstrahlung. Results. The spectrum of the impulsive hard X-ray emission can be fitted equally well with a power-law model with an index of ∼6.5 or a super-hot thermal model with a temperature as high as 100 MK. Imaging observations in the extreme-UV and X-ray bands and extrapolation of the magnetic field structure using a nonlinear force-free model show that energetic electrons trapped in coronal loops are responsible for these impulsive emissions. Conclusions. Since the index of the power-law model is nearly constant during the impulsive phase, the power-law distribution or the super-hot component should be produced by a bulk energization process such as the Fermi and betatron acceleration of collapsing magnetic loops.

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 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 X-Ray Analysis for Electron Beam Enhancement in the Plasma Focus Device*

1974 ◽  
Vol 18 ◽  
pp. 184-196 ◽  
Author(s):  
R. L. Gullickson ◽  
R. H. Barlett
Keyword(s):  
Electric Fields ◽  
Plasma Focus ◽  
Average Energy ◽  
High Energy ◽  
Plasma Focus Device ◽  
X Rays ◽  
Stored Energy ◽  
Power Law Distribution ◽  
X Ray ◽  
Thermoluminescent Dosimeters

AbstractThe plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.

scholarly journals Modelling the Soft X-ray Excess in E1615+061

1994 ◽  
Vol 159 ◽  
pp. 317-317
Author(s):  
M. Bałucińska-Church ◽  
L. Piro ◽  
H. Fink ◽  
F. Fiore ◽  
M. Matsuoka ◽  
...  
Keyword(s):  
Power Law ◽  
Column Density ◽  
High Energy ◽  
X Rays ◽  
Hard Component ◽  
X Ray ◽  
Simple Power ◽  
High Energy Tail ◽  
Photon Index ◽  
Best Fit

SummaryWe report results of an international UV – X-ray campaign in 1990–1992 involving the IUE, Rosat and Ginga satellites to observe E1615+061, a Seyfert 1 galaxy with peculiar spectral and intensity behaviour over the last 20 years. The source has been found to be stable in its medium state during the observations. The Ginga (1–20 keV) spectrum of E1615+061 is adequately represented by a simple power law with a photon index α = 1.8 ± 0.1. However, α ∼ 2, as expected for the intrinsic power law component in a reflection model, cannot be ruled out statistically. The Rosat PSPC (0.1–2 keV) spectra collected during the All Sky Survey and the AO-1 phase can be well-described by a simple power law (α = 2.2 ± 0.1) with cold absorber (NH = 3.5 ± 0.3 · 10λ20 H/cmλ2). Both the photon index being significantly different than that obtained from the Ginga spectrum and the column density being smaller than the galactic column (NH ∼ 4.2 · 10λ20 H/cmλ2) give an indication of a soft excess over and above the hard component seen in the Ginga spectrum. E1615+061 has been observed with IUE in 1990 and in 1992. The source was stable and the colour excess E(B-V) derived from the data = 0.1 is in good agreement with that expected from the galactic absorption.To parameterise the soft excess we fitted the Rosat data with a two-component model consisting of a power law, and a blackbody or thermal bremsstrahlung, with a single galactic absorption term. The column density and the slope of the power law were kept constant. The blackbody temperature was 80 ± 6 eV and 63 ± 12 eV for photon index equal to 1.8 and 2.0, respectively, whereas the bremsstrahlung temperature was 220 ± 40 eV and 115 ± 30 eV for the two cases.An attempt to model the soft excess seen in the Rosat PSPC spectrum has been made assuming that the soft excess is the high energy tail of a disc spectrum which peaks in the UV part of the spectrum. Additionally it was assumed that there is a hard component contributing to the spectrum from UV to X-rays with parameters as described by the Ginga spectrum. The best fit parameters: the mass of the central source and the mass accretion rate were around 5 ± 1 · 10λ6 M⊙ and 0.2 ± 0.04 M⊙/yr, respectively.Our modelling shows that the soft X-ray excess can be described (χredλ2 < 1.2) as the high energy tail of an accretion disk spectrum if the intrinsic power law is quite steep (α = 2). The main contribution to the residuals in the Rosat PSPC range comes from 0.3–0.6 keV, with a tendency for these residuals to increase when the slope gets flatter. The accretion luminosity is ∼ 6.5 · 10λ44 erg/s for the best fit parameters, i.e. about the Eddington luminosity.

scholarly journals Temporal and Spectral Variability of OJ 287 before the April–June 2020 Outburst

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 58
Author(s):  
Nibedita Kalita ◽  
Alok C. Gupta ◽  
Minfeng Gu
Keyword(s):  
Power Law ◽  
Lower Energy ◽  
X Rays ◽  
Power Law Model ◽  
Energy Bands ◽  
Spectral Variability ◽  
X Ray ◽  
Bl Lacertae ◽  
Inverse Compton ◽  
Absorbed Power

We present the results of a temporal and spectral study of the BL Lacertae object OJ 287 in optical, UV, and X-ray bands with observations performed by Swift satellite during September 2019–March 2020. In this period, the source showed moderate variability characterized by variability amplitude of ∼22–31% in all the wavelengths on a short timescale, except the hard X-ray band which was variable by only ∼8%. We observed that the X-ray flux of the source was significantly dominated by the soft photons below 2 keV. Soft lags of ∼45 days were detected between the optical/UV and soft X-ray emissions, while there is no correlation between the hard X-rays and the lower energy bands indicating the presence of two emission components or electron populations. Although two components contribute to the X-ray emission, most of the 0.3–10 keV spectra were well fitted with an absorbed power-law model which outlines the dominance of synchrotron over inverse Compton (IC) mechanism. The X-ray spectra follow a weak “softer when brighter” trend.

scholarly journals Less noticeable shallow decay phase in early X-ray afterglows of GeV/TeV-detected gamma-ray bursts

2020 ◽  
Vol 494 (4) ◽  
pp. 5259-5269 ◽  
Author(s):  
Ryo Yamazaki ◽  
Yuri Sato ◽  
Takanori Sakamoto ◽  
Motoko Serino
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
High Energy ◽  
Decay Phase ◽  
Power Law Model ◽  
X Ray ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

ABSTRACT The nature of the shallow decay phase in the X-ray afterglow of the gamma-ray burst (GRB) is not yet clarified. We analyse the data of early X-ray afterglows of 26 GRBs triggered by Burst Alert Telescope onboard Neil Gehrels Swift Observatory and subsequently detected by Fermi Large Area Telescope (LAT) and/or Imaging Atmospheric Cherenkov Telescopes. It is found that nine events (including two out of three very-high-energy gamma-ray events) have no shallow decay phase and that their X-ray afterglow light curves are well described by single power-law model except for the jet break at later epoch. The rest are fitted by double power-law model and have a break in the early epoch (around ks), however, eight events (including a very-high-energy gamma-ray event) have the pre-break decay index larger than 0.7. We also analyse the data of well-sampled X-ray afterglows of GRBs without LAT detection and compare their decay properties with those of high-energy and very-high-energy gamma-ray events. It is found that for the GeV/TeV bursts, the fraction of events whose X-ray afterglows are described by single power law is significantly larger than those for non-GeV/TeV GRBs. Even if the GeV/TeV GRBs have shallow decay phase, their decay slope tends to be steeper than non-GeV/TeV bursts, that is, they have less noticeable shallow decay phase in the early X-ray afterglow. A possible interpretation along with the energy injection model is briefly discussed.

Millimeter, Microwave, Hard X-Ray, and Soft X-Ray Observations of Energetic Electron Populations in Solar Flares

1994 ◽  
Vol 142 ◽  
pp. 599-610
Author(s):  
M. R. Kundu ◽  
S. M. White ◽  
N. Gopalswamy ◽  
J. Lim
Keyword(s):  
Solar Flares ◽  
Energetic Electron ◽  
Impulsive Phase ◽  
High Energy ◽  
X Rays ◽  
High Turnover ◽  
X Ray ◽  
Nonthermal Electrons ◽  
Time Profiles ◽  
Wavelength Emission

AbstractWe present comparisons of multiwavelength data for a number of solar flares observed during the major campaign of 1991 June. The different wavelengths are diagnostics of energetic electrons in different energy ranges: soft X-rays are produced by electrons with energies typically below 10 keV, hard X-rays by electrons with energies in the range 10-200 keV, microwaves by electrons in the range 100 keV-1 MeV, and millimeter-wavelength emission by electrons with energies of 0.5 MeV and above. The flares in the 1991 June active period were remarkable in two ways: all have very high turnover frequencies in their microwave spectra, and very soft hard X-ray spectra. The sensitivity of the microwave and millimeter data permit us to study the more energetic (>0.3 MeV) electrons even in small flares, where their high-energy bremsstrahlung is too weak for present detectors. The millimeter data show delays in the onset of emission with respect to the emissions associated with lower energy electrons and differences in time profiles, energy spectral indices incompatible with those implied by the hard X-ray data, and a range of variability of the peak flux in the impulsive phase when compared with the peak hard X-ray flux which is two orders of magnitude larger than the corresponding variability in the peak microwave flux. All these results suggest that the hard X-ray-emitting electrons and those at higher energies which produce millimeter emission must be regarded as separate populations. This has implications for the well-known “number problem” found previously when comparing the numbers of nonthermal electrons required to produce the hard X-ray and radio emissions.Subject headings: Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

scholarly journals Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

2019 ◽  
Vol 492 (1) ◽  
pp. 796-803
Author(s):  
Pranjupriya Goswami ◽  
Atreyee Sinha ◽  
Sunil Chandra ◽  
Ranjeev Misra ◽  
Varsha Chitnis ◽  
...  
Keyword(s):  
Power Law ◽  
Wide Band ◽  
Lorentz Factor ◽  
High Energy ◽  
Power Law Distribution ◽  
Large Area ◽  
X Ray ◽  
Curvature Parameter ◽  
The One ◽  
Area X

ABSTRACT We report the analysis of simultaneous multiwavelength data of the high-energy-peaked blazar RGB J0710 + 591 from the Large Area X-ray Proportional Counters, Soft X-ray focusing Telescope, and Ultraviolet Imaging Telescope (UVIT) instruments onboard AstroSat. The wide band X-ray spectrum (0.35–30 keV) is modelled as synchrotron emission from a non-thermal distribution of high-energy electrons. The spectrum is unusually curved, with a curvature parameter βp ∼ 6.4 for a log parabola particle distribution, or a high-energy spectral index p2 &gt; 4.5 for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift–XRT/NuSTAR data where the parameters were βp ∼ 2.2 or p2 ∼ 4. It has long been known that a power-law electron distribution can be produced from a region where particles are accelerated under Fermi process and the radiative losses in acceleration site decide the maximum attainable Lorentz factor, γmax. Consequently, this quantity decides the energy at which the spectrum curves steeply. We show that such a distribution provides a more natural explanation for the AstroSat data as well as the earlier XRT/NuSTAR observation, making this as the first well-constrained determination of the photon energy corresponding to γmax. This in turn provides an estimate of the acceleration time-scale as a function of magnetic field and Doppler factor. The UVIT observations are consistent with earlier optical/UV measurements and reconfirm that they plausibly correspond to a different radiative component than the one responsible for the X-ray emission.

ROSAT Spectra of Quasars

1994 ◽  
Vol 159 ◽  
pp. 369-369
Author(s):  
P. Bühler ◽  
T.J.-L. Courvoisier ◽  
R. Staubert ◽  
H. Brunner ◽  
G. Lamer
Keyword(s):  
Power Law ◽  
Column Density ◽  
Soft Part ◽  
Black Body ◽  
Soft Component ◽  
X Rays ◽  
Power Law Model ◽  
X Ray ◽  
Power Law Index ◽  
Single Power

X–ray observations of AGN with Einstein, EXOSAT and Ginga have shown, that the spectra of quasars in the energy range 2 to 10 keV can be approximately described by a single power law model with a photon index of 1.7 to 2.0. They also suggested that a soft X-ray excess component (below ≈ 1 keV) is a common feature in many quasars. In order to investigate whether a soft excess is characteristic for a certain class of objects we analysed the data of the pointed ROSAT PSPC observations of the six radio-loud quasars PG0007+106, PKS0135-247, QSO0537-286, QSO0923+392, PG1225+317, 3C273 and the radio-quiet quasar PG0804+761. In a first step the observed spectra were fitted with an absorbed single power law model. The hydrogen column density was fixed to its galactic value and the normalisation at 1 keV and the spectral index α were the free fit parameters. In order to decide whether a soft component is present in a source, the resulting power law index was compared with the hard X-ray power law index (2–10 keV) determined in the past with other instruments. A steep ROSAT PSPC spectrum indicates the presence of an additional soft X–ray component. In four cases (PKS0135-247, PG0804+761, QSO0923+392, 3C273) we find that the spectra in the PSPC band are considerably steeper than the spectra above 2 keV and therefore suggest the presence of a soft excess. In order to quantify the contribution of the soft excess these spectra were successively fitted with a model containing a hard power law component and an additional soft component described either by a power law, thermal bremsstrahlung or black body model. For the other three members of our sample (0007+106, 0537-286, 1225+317) the fitted power law index is not enhanced. This means that no soft component has been detected, but not necessarily that it does not exist. There are two effects which render more difficult the detection of a soft component in ROSAT spectra, the absorption of photons by interstellar material and the shift of the spectra towards lower energies due to the redshift. Both processes have first an effect on the soft part of the observed spectrum and it is therefore evident, that this leads to a decrease of the sensitivity for soft X–rays of the emitted spectrum. For the three quasars in our sample, where no soft excess has been detected, either the column density (0007+106) or the redshift (0537-286, 1225+317) is especially large and therefore an eventually present soft component could have remained undetected. In these cases we calculated upper limits for the strength of such a soft component (P. Bühler et al., to be published in A&A.)

The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

1985 ◽  
Vol 43 ◽  
pp. 154-157
Author(s):  
A.J. Tousimis
Keyword(s):  
Ion Beam ◽  
Depth Resolution ◽  
Sample Surface ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Electrons And Ions ◽  
Spatial Depth ◽  
Minimum Surface Area ◽  
Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

Sign in / Sign up

Export Citation Format

Share Document