SIMULTANEOUS X-RAY/TeV OBSERVATIONS OF AN EXCEPTIONAL FLARE OF PKS 2155-304

2008 ◽  
Vol 17 (09) ◽  
pp. 1449-1456 ◽  
Author(s):  
◽  
L. COSTAMANTE
Keyword(s):  
Small Amplitude ◽  
X Ray ◽  
Preliminary Results ◽  
Γ Ray ◽  
First Time ◽  
Optical Telescopes

On the night of 29–30 July 2006, a major γ-ray outburst occurred from PKS 2155-304, which was observed simultaneously with H.E.S.S., Chandra and the Bronberg optical telescopes. An overall 6–8 hours of simultaneous uninterrupted coverage was obtained. Here we report the first preliminary results of this exceptional dataset. The source showed correlated variability between the X-ray and VHE bands, with no lags. The spectra evolve with similar patterns. Huge VHE variations (~ 22×) are accompanied only by small-amplitude X-ray and optical variations (factor 2 and 15% respectively). The source has shown for the first time in an HBL a large Compton dominance (LC/LS ~ 10), and a cubic relation between VHE and X-ray flux variations, during a decaying phase. These results challenge all known "standard" scenarios for the blazar 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.

scholarly journals Relativistic jets in Narrow-Line Seyfert 1

2010 ◽  
Vol 6 (S275) ◽  
pp. 176-177
Author(s):  
L. Foschini ◽  
E. Angelakis ◽  
G. Bonnoli ◽  
G. Calderone ◽  
M. Colpi ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Narrow Line ◽  
Relativistic Jets ◽  
Preliminary Results ◽  
New Class ◽  
Γ Ray ◽  
First Time

AbstractNarrow-Line Seyfert 1 (NLS1) class of active galactic nuclei (AGNs) is generally radio-quiet, but a small percent of them are radio-loud. The recent discovery by Fermi/LAT of high-energy γ-ray emission from 4 NLS1s proved the existence of relativistic jets in these systems. It is therefore important to study this new class of γ-ray emitting AGNs. Here we report preliminary results about the observations of the July 2010 γ-ray outburst of PMN J0948+0022, when the source flux exceeded for the first time 10−6 ph cm−2 s−1 (E > 100 MeV).

Preliminary results from the super soft X-ray and γ-ray detectors onboard Shenzhou-2

2002 ◽  
Vol 26 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Nan Zhang ◽  
He-sen Tang ◽  
Jin Chang
Keyword(s):  
X Ray ◽  
Preliminary Results ◽  
Γ Ray

High Energy γ-ray Observations of SN 1987A

1988 ◽  
Vol 7 (4) ◽  
pp. 486-489
Author(s):  
R.K. Sood ◽  
J.A. Thomas ◽  
L. Waldron ◽  
R.K. Manchanda ◽  
G.K. Rochester ◽  
...  
Keyword(s):  
High Energy ◽  
Balloon Flight ◽  
X Ray ◽  
Preliminary Results ◽  
Sn 1987A ◽  
Γ Ray

AbstractSN 1987A has been observed with a combined high energy γ-ray (50-500 MeV) and hard X-ray (15-150 keV) payload during a balloon flight on 5 April 1988 from Alice Springs, Australia. The γ-ray observations, along with our earlier ones on 19 April 1987 are the only such observations of the supernova to date. The γ-ray detector characteristics are described. The preliminary results of the recent flight and their implications in terms of the known supernova parameters are discussed.

scholarly journals An X-ray survey of the central molecular zone: variability of the FeKα emission line

2013 ◽  
Vol 9 (S303) ◽  
pp. 94-96
Author(s):  
Simona Soldi ◽  
Maïca Clavel ◽  
Andrea Goldwurm ◽  
Mark R. Morris ◽  
Gabriele Ponti ◽  
...  
Keyword(s):  
Emission Line ◽  
Molecular Clouds ◽  
Galactic Center ◽  
X Ray ◽  
Preliminary Results ◽  
Sgr A ◽  
Flux Increase ◽  
C Complex ◽  
First Time

AbstractThe bulk of the FeKα emission detected in the central molecular zone (CMZ) is thought to be associated with reflection by the central molecular clouds of enhanced past emission from an external X-ray source, most likely Sgr A*. In order to follow the propagation of the reflected emission through the Galactic center (GC), we analyzed all XMM-Newton observations carried out from 2000 to 2012. Preliminary results indicate that while most of the regions that were bright at 6.4 keV in 2000–2001 have a significantly lower flux in 2012, a few other experienced a flux increase. We report for the first time a significant decrease of the FeKα emission in the Sgr C complex, supporting the reflection origin of the 6.4 keV emission detected in this region.

scholarly journals Unveiling the origin of steep decay in γ-ray bursts

2020 ◽  
Author(s):  
Samuele Ronchini ◽  
Gor Oganesyan ◽  
Marica Branchesi ◽  
Stefano Ascenzi ◽  
Maria Grazia Bernardini ◽  
...  
Keyword(s):  
Energy Exchange ◽  
Relativistic Jets ◽  
Time Resolved ◽  
X Ray ◽  
Compact Binary ◽  
Internal Dissipation ◽  
Adiabatic Cooling ◽  
Γ Ray ◽  
First Time ◽  
Steep Decay

Abstract γ-ray bursts (GRBs) are short-lived transients releasing a large amount of energy (10^51-10^53 erg) in the keV-MeV energy range. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. While thousands of GRBs have been observed over the last thirty years, we still have an incomplete understanding of where and how the radiation is generated in the jet. A novel investigation of the GRB emission mechanism, via time-resolved spectral analysis of the X-ray tails of bright GRB pulses, enables us to discover a unique relation between the spectral index and the flux. This relation is incompatible with the long standing scenario invoked to interpret X-ray tails, that is, the delayed arrival of pho-tons from high-latitude parts of the jet. We show that our results provide for the first time evidence of adiabatic cooling and efficient energy exchange between the emitting particles in the relativistic outflows of GRBs.

Spider diversity in the Bukit Timah Nature Reserve, Singapore

2019 ◽  
Vol 71 ((suppl.1)) ◽  
pp. 209-243
Author(s):  
J.K.H. Koh ◽  
D.J. Court
Keyword(s):  
Nature Reserve ◽  
New Records ◽  
Secondary Forest ◽  
Distinct Species ◽  
Primary Forest ◽  
Preliminary Results ◽  
Vegetation Zones ◽  
Comprehensive Survey ◽  
Quantitative Analyses ◽  
First Time

This paper discusses the preliminary results of the first comprehensive survey of the spiders of the Bukit Timah Nature Reserve (BTNR) in Singapore. Two plots were established in each of the three zones of vegetation, viz., primary forest, old secondary forest, and maturing secondary forest. They were repeatedly sampled over an 18-month period. Sorting of the collection so far suggests that the three vegetation zones harbour rather different spider assemblages. Only ~9% of the total spider fauna recovered was shared by all three zones. The results have also yielded a preliminary picture of dominance, abundance and rarity. Although first intended to obtain a baseline for future quantitative analyses, the survey became a testing ground to modify and refine methodology so as to conduct future quantitative surveys with greater scientific rigour. Taxonomic work on the samples so far shows that the spiders in the BTNR span over 43 families, of which six families are listed for the first time in Singapore. The tally is summarised in an interim checklist of BTNR spiders. The checklist, with a total of 317 entries, shows that there are 158 described species of spiders in BTNR, of which 25 species are new records for Singapore. Another 159 morphospecies are provisionally recognised as distinct species, some of which may be new to science. Our observations during the survey have allowed us to provide a narrative of BTNR spider diversity against a backdrop of their microhabitat specialisation.

Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

2006 ◽  
Vol 71 (2) ◽  
pp. 197-206 ◽  
Author(s):  
Martin Pošta ◽  
Jan Čermák ◽  
Pavel Vojtíšek ◽  
Ivana Císařová
Keyword(s):  
Rhodium Complexes ◽  
Iridium Complexes ◽  
X Ray ◽  
First Time

The first rhodium complexes of diphosphinoazines [{RhCl(1,2-η:5,6-η-CH=CHCH2CH2CH=CHCH2CH2)}2 {μ-R2PCH2C(But)=NN=C(But)CH2PR2] (R = Ph, Cy, Pri) were prepared by cleavage of the bridge in chloro(cycloocta-1,5-diene)rhodium(I) dimer, the analogous iridium(I) complexes were also prepared for the first time. The X-ray structures of isostructural rhodium and iridium complexes with bis(dicyclohexylphosphino)pinacoloneazine were determined. Diphosphinoazine ligands in the complexes remained in (Z,Z) configuration bridging two RhCl(C8H12) units.

scholarly journals Quartz Crystallite Size and Moganite Content as Indicators of the Mineralogical Maturity of the Carboniferous Chert: The Case of Cherts from Eastern Asturias (Spain)

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 611
Author(s):  
Celia Marcos ◽  
María de Uribe-Zorita ◽  
Pedro Álvarez-Lloret ◽  
Alaa Adawy ◽  
Patricia Fernández ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Crystallite Size ◽  
Archaeological Sites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Infrared And Raman Spectroscopy ◽  
First Time ◽  
Geological Formations

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite, since its detection by X-ray diffraction is practically imperceptible, and the crystallite size (over 1000 Å) of the quartz in these cherts would be indicative of its maturity and could potentially be used for dating chert-tools recovered from archaeological sites. Also, this information can constitute essential data to differentiate the cherts and compare them with those used in archaeological tools. However, neither composition nor crystallite size would allow distinguishing between coastal and inland chert outcrops belonging to the same geological formations.

scholarly journals First Report on the Geologic Occurrence of Natural Na–A Zeolite and Associated Minerals in Cretaceous Mudstones of the Paja Formation of Vélez (Santander), Colombia

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 218
Author(s):  
Carlos Alberto Ríos-Reyes ◽  
German Alfonso Reyes-Mendoza ◽  
José Antonio Henao-Martínez ◽  
Craig Williams ◽  
Alan Dyer
Keyword(s):  
Natural Zeolite ◽  
Scanning Electron Micrographs ◽  
Total Sulfur ◽  
Zeolite A ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineral Phases ◽  
The World ◽  
Porosity And Permeability ◽  
First Time

This study reports for the first time the geologic occurrence of natural zeolite A and associated minerals in mudstones from the Cretaceous Paja Formation in the urban area of the municipality of Vélez (Santander), Colombia. These rocks are mainly composed of quartz, muscovite, pyrophyllite, kaolinite and chlorite group minerals, framboidal and cubic pyrite, as well as marcasite, with minor feldspar, sulphates, and phosphates. Total organic carbon (TOC), total sulfur (TS), and millimeter fragments of algae are high, whereas few centimeters and not biodiverse small ammonite fossils, and other allochemical components are subordinated. Na–A zeolite and associated mineral phases as sodalite occur just beside the interparticle micropores (honeycomb from framboidal, cube molds, and amorphous cavities). It is facilitated by petrophysical properties alterations, due to processes of high diagenesis, temperatures up to 80–100 °C, with weathering contributions, which increase the porosity and permeability, as well as the transmissivity (fluid flow), allowing the geochemistry remobilization and/or recrystallization of pre-existing silica, muscovite, kaolinite minerals group, salts, carbonates, oxides and peroxides. X-ray diffraction analyses reveal the mineral composition of the mudstones and scanning electron micrographs show the typical cubic morphology of Na–A zeolite of approximately 0.45 mμ in particle size. Our data show that the sequence of the transformation of phases is: Poorly crystalline aluminosilicate → sodalite → Na–A zeolite. A literature review shows that this is an unusual example of the occurrence of natural zeolites in sedimentary marine rocks recognized around the world.

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