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 Precise Timing and Phase-resolved Spectroscopy of the Young Pulsar J1617–5055 with NuSTAR

2021 ◽  
Vol 923 (2) ◽  
pp. 249
Author(s):  
Jeremy Hare ◽  
Igor Volkov ◽  
George G. Pavlov ◽  
Oleg Kargaltsev ◽  
Simon Johnston
Keyword(s):  
Power Law ◽  
Duty Cycle ◽  
Radio Pulse ◽  
Power Law Model ◽  
Telescope Array ◽  
X Ray ◽  
Linearly Polarized ◽  
Photon Index ◽  
Absorbed Power ◽  
Fourier Harmonics

Abstract We report on a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the young, energetic pulsar PSR J1617–5055. Parkes Observatory 3 GHz radio observations of the pulsar (taken about 7 yr before the NuSTAR observations) are also reported here. NuSTAR detected pulsations at a frequency of f ≈ 14.4 Hz (P ≈ 69.44 ms) and, in addition, the observation was long enough to measure the source’s frequency derivative, f ̇ ≈ − 2.8 × 10 − 11 Hz s−1. We find that the pulsar shows one peak per period at both hard X-ray and radio wavelengths, but that the hard X-ray pulse is broader (having a duty cycle of ∼0.7), than the radio pulse (having a duty cycle of ∼0.08). Additionally, the radio pulse is strongly linearly polarized. J1617's phase-integrated hard X-ray spectrum is well fit by an absorbed power-law model, with a photon index Γ = 1.59 ± 0.02. The hard X-ray pulsations are well described by three Fourier harmonics, and have a pulsed fraction that increases with energy. We also fit the phase-resolved NuSTAR spectra with an absorbed power-law model in five phase bins and find that the photon index varies with phase from Γ = 1.52 ± 0.03 at phases around the flux maximum to Γ = 1.79 ± 0.06 around the flux minimum. Last, we compare our results with other pulsars whose magnetospheric emission is detected at hard X-ray energies and find that, similar to previous studies, J1617's hard X-ray properties are more similar to the MeV pulsars than the GeV pulsars.

scholarly journals The Radiation Transfer of Soft X-rays

1997 ◽  
Vol 166 ◽  
pp. 337-340 ◽  
Author(s):  
Jürgen Kerp ◽  
Jochen Pietz
Keyword(s):  
Power Law ◽  
Intensity Distribution ◽  
Galactic Halo ◽  
Background Radiation ◽  
Plasma Temperature ◽  
Intensity Variation ◽  
Background Intensity ◽  
X Rays ◽  
Energy Bands ◽  
X Ray

AbstractWe discuss the link between the halo plasma temperature and the power-law spectral index of the extragalactic background radiation. This link is of strong influence for the derivation of the Galactic halo intensity distribution. In principal, we can distinguish between two combinations of Galactic halo plasma temperature and power-law slope. The first combination consists of a halo plasma of Thalo = 106 K and an E−2 approximation of the extragalactic background radiation. The second combination is Thalo = 106.2 K and an E−1.5. Both combinations are in agreement with recent observational results, thus it is not feasible to discriminate between both models on the basis of X-ray data available. But, the soft X-ray background intensity distribution in the ¼ keV and ¾ keV ROSAT energy bands differs significantly. The Thalo = 106 K and an E−2 allows a patchy ¼ keV intensity distribution while the Thalo = 106.2 K and an E−1.5 predicts a much smoother intensity variation since the hotter halo plasma accounts for a significant fraction of the ¾ keV background radiation.

scholarly journals An Inverse Compton Scattering Model for the Spectra of X-ray Pulsars

1987 ◽  
Vol 125 ◽  
pp. 248-248
Author(s):  
G.J. Qiao ◽  
X.J. Wu ◽  
H. Chen ◽  
X.Y. Xia
Keyword(s):  
Magnetic Fields ◽  
Power Law ◽  
Lower Energy ◽  
High Energy ◽  
Energy Index ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Cyclotron Absorption ◽  
Inverse Compton ◽  
Energy Cutoff

Many observations have been reported in the field of X-ray pulsars, but the mechanism for X-ray emission is not well understood. The X-ray spectra can not be simply described in terms of blackbody or thermal bremsstralung. The high-energy cutoff could be due to cyclotron absorption in high (≧1012 Gauss) magnetic fields. For the lower energy it can be fitted by a power law with energy index α.

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 Non-Thermal Emission from Radio-Loud AGN Jets: Radio vs. X-rays

Galaxies ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 6
Author(s):  
Elena Fedorova ◽  
Bohdan Hnatyk ◽  
Antonino Del Popolo ◽  
Anatoliy Vasylenko ◽  
Vadym Voitsekhovskyi
Keyword(s):  
Active Galactic Nuclei ◽  
Power Law ◽  
Thermal Emission ◽  
Galactic Nuclei ◽  
X Rays ◽  
X Ray ◽  
Compact Source ◽  
Central Engine ◽  
Sky Survey ◽  
Inverse Compton

We consider the sample of 55 blazars and Seyferts cross-correlated from the Planck all-sky survey based on the Early Release Compact Source Catalog (ERCSC) and Swift BAT 105-Month Hard X-ray Survey. The radio Planck spectra vs. X-ray Swift/XRT+BAT spectra of the active galactic nuclei (AGN) sample were fitted with the simple and broken power law (for the X-ray spectra taking into account also the Galactic neutral absorption) to test the dependencies between the photon indices of synchrotron emission (in radio range) and synchrotron self-Compton (SSC) or inverse-Compton emission (in X-rays). We show that for the major part of the AGN in our sample there is a correspondence between synchrotron and SSC photon indices (one of two for broken power-law model) compatible within the error levels. For such objects, this can give a good perspective for the task of distinguishing between the jet base counterpart from that one emitted in the disk-corona AGN “central engine”.

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.)

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.

Visualization of microvessels by angiography using inverse-Compton scattering X-rays in animal models

2014 ◽  
Vol 21 (6) ◽  
pp. 1327-1332 ◽  
Author(s):  
Toshiharu Fujii ◽  
Naoto Fukuyama ◽  
Chiharu Tanaka ◽  
Yoshimori Ikeya ◽  
Yoshiro Shinozaki ◽  
...  
Keyword(s):  
Compton Scattering ◽  
Photon Number ◽  
High Gain ◽  
Image Sensor ◽  
Clinical Settings ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Small Vessels ◽  
Inverse Compton

The fundamental performance of microangiography has been evaluated using the S-band linac-based inverse-Compton scattering X-ray (iCSX) method to determine how many photons would be required to apply iCSX to human microangiography. ICSX is characterized by its quasi-monochromatic nature and small focus size which are fundamental requirements for microangiography. However, the current iCSX source does not have sufficient flux for microangiography in clinical settings. It was determined whether S-band compact linac-based iCSX can visualize small vessels of excised animal organs, and the amount of X-ray photons required for real time microangiography in clinical settings was estimated. The iCSX coupled with a high-gain avalanche rushing amorphous photoconductor camera could visualize a resolution chart with only a single iCSX pulse of ∼3 ps duration; the resolution was estimated to be ∼500 µm. The iCSX coupled with an X-ray cooled charge-coupled device image sensor camera visualized seventh-order vascular branches (80 µm in diameter) of a rabbit ear by accumulating the images for 5 and 30 min, corresponding to irradiation of 3000 and 18000 iCSX pulses, respectively. The S-band linac-based iCSX visualized microvessels by accumulating the images. An iCSX source with a photon number of 3.6 × 103–5.4 × 104times greater than that used in this study may enable visualizing microvessels of human fingertips even in clinical settings.

scholarly journals Nested Kirkpatrick–Baez (Montel) optics for hard X-rays

2015 ◽  
Vol 48 (2) ◽  
pp. 558-564 ◽  
Author(s):  
Giacomo Resta ◽  
Boris Khaykovich ◽  
David Moncton
Keyword(s):  
Ray Tracing ◽  
Compton Scattering ◽  
Analytical Procedure ◽  
X Rays ◽  
Multilayer Mirrors ◽  
Comprehensive Description ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Proper Orientation

A comprehensive description and ray-tracing simulations are presented for symmetric nested Kirkpatrick–Baez (KB) mirrors, commonly used at synchrotrons and in commercial X-ray sources. This paper introduces an analytical procedure for determining the proper orientation between the two surfaces composing the nested KB optics. This procedure has been used to design and simulate collimating optics for a hard-X-ray inverse Compton scattering source. The resulting optical device is composed of two 12 cm-long parabolic surfaces coated with a laterally graded multilayer and is capable of collimating a 12 keV beam with a divergence of 5 mrad (FWHM) by a factor of ∼250. A description of the ray-tracing software that was developed to simulate the graded multilayer mirrors is included.

New insight into the origin of the GeV flare in the binary system PSR B1259-63/LS 2883 from the 2017 periastron passage

2020 ◽  
Vol 497 (1) ◽  
pp. 648-655
Author(s):  
M Chernyakova ◽  
D Malyshev ◽  
S Mc Keague ◽  
B van Soelen ◽  
J P Marais ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Energy Release ◽  
Broad Band ◽  
Strong Shock ◽  
Optical Observations ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton ◽  
Pulsar Wind

ABSTRACT PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around an O9.5Ve star, LS 2883, with a period of ∼3.4 yr. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broad-band emission in the radio, X-rays, GeV, and TeV domains. While the radio, X-ray, and TeV light curves show rather similar behaviour, the GeV light curve appears very different with a huge outburst about a month after a periastron. The energy release during this outburst seems to significantly exceed the spin-down luminosity of the pulsar and both the GeV light curve and the energy release vary from one orbit to the next. In this paper, we present for the first time the results of optical observations of the system in 2017, and also reanalyse the available X-ray and GeV data. We present a new model in which the GeV data are explained as a combination of the bremsstrahlung and inverse Compton emission from the unshocked and weakly shocked electrons of the pulsar wind. The X-ray and TeV emission is produced by synchrotron and inverse Compton emission of energetic electrons accelerated on a strong shock arising due to stellar/pulsar winds collision. The brightness of the GeV flare is explained in our model as a beaming effect of the energy released in a cone oriented, during the time of the flare, in the direction of the observer.

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