scholarly journals Simultaneous observations of the blazar PKS 2155−304 from ultra-violet to TeV energies

2020 ◽  
Vol 639 ◽  
pp. A42
Author(s):  
H. Abdalla ◽  
R. Adam ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
...  
Keyword(s):  
Ultra Violet ◽  
High Energy ◽  
X Rays ◽  
Broad Energy Range ◽  
Significant Contamination ◽  
Multi Wavelength ◽  
High Energy Emission ◽  
Broad Energy ◽  
Made In ◽  
Significant Flux

Here we report the results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS 2155−304 involving Swift, NuSTAR, Fermi-LAT, and H.E.S.S. The use of these instruments allows us to cover a broad energy range, which is important for disentangling the different radiative mechanisms. The source, observed from June 2013 to October 2013, was found in a low flux state with respect to previous observations but exhibited highly significant flux variability in the X-rays. The high-energy end of the synchrotron spectrum can be traced up to 40 keV without significant contamination by high-energy emission. A one-zone synchrotron self-Compton model was used to reproduce the broadband flux of the source for all the observations presented here but failed for previous observations made in April 2013. A lepto-hadronic solution was then explored to explain these earlier observational results.

scholarly journals Constraining the transient high-energy activity of FRB 180916.J0158+65 with Insight–HXMT follow-up observations

2020 ◽  
Vol 642 ◽  
pp. A160
Author(s):  
C. Guidorzi ◽  
M. Orlandini ◽  
F. Frontera ◽  
L. Nicastro ◽  
S. L. Xiong ◽  
...  
Keyword(s):  
Broad Band ◽  
Active Phase ◽  
Effective Area ◽  
High Energy ◽  
Broad Energy Range ◽  
Released Energy ◽  
Fast Radio Burst ◽  
High Energy Emission ◽  
Broad Energy

Context. A link has finally been established between magnetars and fast radio burst (FRB) sources. Within this context, a major issue that remains unresolved pertains to whether sources of extragalactic FRBs exhibit X/γ-ray outbursts and whether this is correlated with radio activity. If so, the subsequent goal is to identify these sources. Aims. We aim to constrain possible X/γ-ray burst activity from one of the nearest extragalactic FRB sources currently known. This is to be done over a broad energy range by looking for bursts over a range of timescales and energies that are compatible with those of powerful flares from extragalactic magnetars. Methods. We followed up on the observation of the as-yet nearest extragalactic FRB source, located at a mere 149 Mpc distance, namely, the periodic repeater FRB 180916.J0158+65. This took place during the active phase between 4 and 7 February 2020, using the Insight–Hard X-ray Modulation Telescope (Insight–HXMT). By taking advantage of the combination of broad-band wavelengths, a large effective area, and several independent detectors at our disposal, we searched for bursts over a set of timescales from 1 ms to 1.024 s with a sensitive algorithm that had been previously characterised and optimised. Moreover, through simulations, we studied the sensitivity of our technique in the released energy-duration phase space for a set of synthetic flares and assuming a range of different energy spectra. Results. We constrain the possible occurrence of flares in the 1−100 keV energy band to E <  1046 erg for durations Δ t <  0.1 s over several tens of ks exposure. Conclusions. We can rule out the occurrence of giant flares similar to the ones that were observed in the few cases of Galactic magnetars. The absence of reported radio activity during our observations prevents us from making any determinations regarding the possibility of simultaneous high-energy emission.

scholarly journals A New Chapter in Hard X-rays of the M87 AGN

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 9
Author(s):  
Ka-Wah Wong ◽  
Rodrigo S. Nemmen ◽  
Jimmy A. Irwin ◽  
Dacheng Lin
Keyword(s):  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow ◽  
Relativistic Jet ◽  
Very High Energy ◽  
Γ Ray ◽  
High Energy Emission ◽  
First Time ◽  
Very High

The nearby M87 hosts an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands, but little has been done in hard X-rays ≳10 keV. For the first time, we have successfully detected hard X-rays up to 40 keV from its X-ray core with joint Chandra and NuSTAR observations, providing important insights to the X-ray origins: from the unresolved jet or the accretion flow. We found that the hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain very-high-energy γ -ray emission above a GeV. We discuss recent models to understand these high energy emission processes.

Sky survey of high-energy cosmic X-rays and spectral information on sources in the Crab nebula, Cygnus, and Scorpius

1968 ◽  
Vol 46 (10) ◽  
pp. S409-S413 ◽  
Author(s):  
Walter H. G. Lewin ◽  
George W. Clark ◽  
William B. Smith
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Rays ◽  
Coma Cluster ◽  
X Ray ◽  
Sky Survey ◽  
Upper Limits ◽  
Intensity Ratios ◽  
The Crab Nebula ◽  
Made In

A complete X-ray survey of the northern sky has been made in the energy range 20–100 keV. Spectra are given for Cyg X-1 and Tau X-1. Intensity ratios (Cyg X-1/Tau X-1) of 0.84 ± 0.10 and 1.30 ± 0.25 were derived in the 20–70 keV range from data obtained on July 19, 1966 and February 13, 1967, respectively. Observations on Sco X-1 and the Coma cluster show upper limits which are quite different from results reported by other groups.

scholarly journals Radio Galaxies - The TeV Challenge

2018 ◽  
Author(s):  
Bindu Rani
Keyword(s):  
Gamma Ray ◽  
Radio Galaxies ◽  
High Energy ◽  
Energy Emission ◽  
Long Baseline ◽  
Multi Wavelength ◽  
Emission Models ◽  
Radiation Processes ◽  
High Energy Emission ◽  
Near Future

Over the past decade, our knowledge of the $\gamma$-ray sky has been revolutionized by ground- and space-based observatories by detecting photons up to several hundreds of tera-electron volt (TeV) energies. A major population of the $\gamma$-ray bright objects are active galactic nuclei (AGN) with their relativistic jets pointed along our line-of-sight. Gamma-ray emission is also detected from nearby mis-aligned AGN such as radio galaxies. While the TeV-detected radio galaxies ($TeVRad$) only form a small fraction of the $\gamma$-ray detected AGN, their multi-wavelength study offers a unique opportunity to probe and pinpoint the high-energy emission processes and sites. Even in the absence of substantial Doppler beaming $TeVRad$ are extremely bright objects in the TeV sky (luminosities detected up to $10^{45}~erg~s^{-1}$), and exhibit flux variations on timescales shorter than the event-horizon scales (flux doubling timescale less than 5 minutes). Thanks to the recent advancement in the imaging capabilities of high-resolution radio interferometry (millimeter very long baseline interferometry, mm-VLBI), one can probe the scales down to less than 10 gravitational radii in $TeVRad$, making it possible not only to test jet launching models but also to pinpoint the high-energy emission sites and to unravel the emission mechanisms. This review provides an overview of the high-energy observations of $TeVRad$ with a focus on the emitting sites and radiation processes. Some recent approaches in simulations are also sketched. Observations by the near-future facilities like Cherenkov Telescope Array, short millimeter-VLBI, and high-energy polarimetry instruments will be crucial for discriminating the competing high-energy emission models.

scholarly journals The unique case of the AGN core of M87: a misaligned low power blazar?

2019 ◽  
Author(s):  
M Lucchini ◽  
F Krauß ◽  
S Markoff
Keyword(s):  
Spectral Energy Distribution ◽  
Large Mass ◽  
High Energy ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Zone Model ◽  
Multi Wavelength ◽  
General Relativistic ◽  
Unique Source ◽  
High Energy Emission

Abstract M87 hosts one of the closest jetted active galactic nucleus (AGN) to Earth. Thanks to its vicinity and to the large mass of is central black hole, M87 is the only source in which the jet can be directly imaged down to near-event horizon scales with radio very large baseline interferometry (VLBI). This property makes M87 a unique source to isolate and study jet launching, acceleration and collimation. In this paper we employ a multi-zone model designed as a parametrisation of general relativistic magneto-hydrodynamics (GRMHD); for the first time we reproduce the jet’s observed shape and multi-wavelength spectral energy distribution (SED) simultaneously. We find strong constraints on key physical parameters of the jet, such as the location of particle acceleration and the kinetic power. However, we under-predict the (unresolved) γ-ray flux of the source, implying that the high-energy emission does not originate in the magnetically-dominated inner jet regions. Our results have important implications both for comparisons of GRMHD simulations with observations, and for unified models of AGN classes.

scholarly journals Historical Supernovae and Supernova Remnants

1996 ◽  
Vol 145 ◽  
pp. 323-331 ◽  
Author(s):  
Zhenru Wang
Keyword(s):  
Tang Dynasty ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
High Energy ◽  
X Rays ◽  
Supernovae And Supernova Remnants ◽  
X Ray ◽  
The Tang Dynasty ◽  
High Energy Emission ◽  
The Relationship

The oldest historical supernova (SN), recorded by ancient Chinese in 14th Century B.C. on pieces of tortoise shells or bones, is identified with the aid of modern space γ-ray observations. Hard X-rays with energy up to 20 keV were observed from IC 443 by the X-ray satellite Ginga. We infer from these observations the age of IC 443 is ∼ 1000 — 1400 yrs. The result supports the hypothesis that IC 443 is the remnant of the historical SN 837 that occurred during the Tang Dynasty. The association between the supernova remnant (SNR) CTB 80 and SN 1408 has been hotly debated for about ten years and is briefly reviewed and discussed here. A new picture is presented to explain this association. High energy emission from historical SNRs can persist in a multiphase interstellar medium (ISM). As a result, the study of the relationship between SNRs and ancient guest stars has gained new vitality.

scholarly journals Recent Advances in X-Ray Astronomy

1995 ◽  
Vol 10 ◽  
pp. 3-16
Author(s):  
Yasuo Tanaka
Keyword(s):  
Wide Temperature Range ◽  
X Rays ◽  
New Era ◽  
X Ray ◽  
Temperature Range ◽  
Rocket Flight ◽  
Recent Advances ◽  
Multi Wavelength ◽  
The Universe ◽  
Made In

X-ray astronomy was born in June 1962 with a totally unexpected discovery of a bright X-ray source (presently known as Sco X-1) in a historic rocket flight conducted by Riccardo Giacconi, Herb Gursky, Frank Paolini and late Bruno Rossi. In the last 30 years, astronomy through the newly opened window has made a dramatic expansion.The universe contains enormously rich varieties which had been left unexplored until recent times. From 40’s through 60’s, new wavelength windows, radio, infrared and X-rays successively opened. As a result, the presence of objects and regions distributed over an extremely wide temperature range from a few Kelvin through hundreds of millions of Kelvin were discovered. A burst of surprising discoveries made in 60’s marked the opening of a whole new era of multi-wavelength astronomy.

Multi-wavelength anomalous diffraction method for I and Xe atoms using ultra-high-energy X-rays from SPring-8

2004 ◽  
Vol 37 (6) ◽  
pp. 925-933 ◽  
Author(s):  
Kazuki Takeda ◽  
Hideyuki Miyatake ◽  
Sam-Yong Park ◽  
Masahide Kawamoto ◽  
Nobuo Kamiya ◽  
...  
Keyword(s):  
Diffraction Method ◽  
High Energy ◽  
X Rays ◽  
Ultra High Energy ◽  
Anomalous Diffraction ◽  
Egg White Lysozyme ◽  
Density Maps ◽  
Mad Phasing ◽  
Multi Wavelength ◽  
Lysozyme Crystals

The first successful multi-wavelength anomalous diffraction (MAD) experiments using ultra-high-energy X-rays (∼35 keV) were performed for iodine and xenon derivatives of hen egg-white lysozyme crystals. The beamline BL41XU of SPring-8 enabled the collection of high-quality MAD data, which led to the calculation of anomalous or dispersive difference Patterson maps that determined the positions of iodine and xenon atoms. The electron density maps obtained by the density modification method for both cases proved to be of sufficient quality for building molecular models. I-MAD and Xe-MAD phasing are now available at SPring-8, and the utilization of ultra-high-energy X-rays will make a significant contribution to the solution of the phase problem in protein crystallography.

scholarly journals The photo-electric action of X-rays

1918 ◽  
Vol 94 (660) ◽  
pp. 269-280 ◽  
Keyword(s):  
Kinetic Energy ◽  
Ultra Violet ◽  
Electric Activity ◽  
Exciting Light ◽  
X Rays ◽  
Left Hand ◽  
Experimental Side ◽  
Fundamental Law ◽  
Electric Action ◽  
Made In

The fundamental law of photo-electric activity states that ½ mv 2 = hv - w , (1) where the left-hand side represents the maximum kinetic energy of the liberated electrons, h is Planck’s constant, v is the frequency of the exciting light, and w is a constant which measures the work necessary for an electron to escape from the substance, and whose value is characteristic of the material under consideration. The equation (1) was first given by Einstein as a deduction from the view that the energy of radiation was distributed in discrete quanta. However, I succeeded in showing that it followed from Planck’s radiation formula; so that it evidently has a wider basis than the restricted and doubtful hypothesis used by Einstein. On the experimental side the evidence for several years was somewhat conflicting, but in 1912 I showed, as a result of experiments made in collaboration with Dr. K. T. Compton, that the equation represented the photo-electric behaviour in the visible and in the ultra-violet as far as λ= 2 x 10 -5 cm., for the metals sodium, aluminium, magnesium, zinc, tin, and platinum as accurately as it could be determined. The experiments also showed that the differences in the values of the constants w for different metals were connected with the corresponding contact potentials V by the relation w n - w m = e (V n -V m ). (2)

scholarly journals Improving EDS For Low Energy X-Rays Under 1000eV Using an Attachable Detector Optic

2008 ◽  
Vol 16 (2) ◽  
pp. 6-9
Author(s):  
David O’Hara ◽  
Greg Brown ◽  
Eric Lochner
Keyword(s):  
Dead Time ◽  
Beam Current ◽  
High Energy ◽  
Low Energy ◽  
Detector Response ◽  
X Rays ◽  
Ray Optics ◽  
X Ray ◽  
Optics Fabrication ◽  
Made In

Although considerable advances have been made in Energy Dispersive Detectors for microanalysis, low energy analysis under 1000eV is still relatively poor due to detector response and inefficient production of low energy x-rays. X-ray optics fabrication methods by O’Hara and measurements by McCarthy et. al. indicated that it should be possible to fabricate x-ray optics that could be used to significantly increase the low energy x-ray flux seen by an EDS detector without increasing the beam current. Such an optic would be useful to increase low energy counts without moving the detector closer, which would simply increase the high energy counts and dead time.

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