Journal articles: 'Gamma ray signatures'

1

Cirelli, Marco. "Gamma-ray signatures of Dark Matter." EPJ Web of Conferences 136 (2017): 01004. http://dx.doi.org/10.1051/epjconf/201713601004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Valle, G. "Gamma ray signatures from Galactic neutralino annihilation." Astronomy & Astrophysics 424, no. 3 (2004): 765–72. http://dx.doi.org/10.1051/0004-6361:20041042.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Gabici, S., and F. A. Aharonian. "Gamma ray signatures of ultra high energy cosmic ray accelerators." Astronomische Nachrichten 327, no. 5-6 (2006): 619–23. http://dx.doi.org/10.1002/asna.200610605.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

The, Lih-Sin, Donald D. Clayton, and Adam Burrows. "X-Ray and Gamma-Ray Signatures of Wolf-Rayet Supernova Explosions." Symposium - International Astronomical Union 143 (1991): 537–46. http://dx.doi.org/10.1017/s007418090004571x.

Full text

Abstract:

It is widely speculated that a Type Ib supernova is the explosion of a Wolf-Rayet star. We calculate the X-ray and gamma-ray signatures of models of that type, assuming all hard photons to have originated with Ni decay chains, in hopes of providing diagnostics of the exposed-core models of massive stars, which constitute one model of the Wolf-Rayet stars, calculated by Ensman and Woosley (1988). These provide the characteristic luminosity peak and light curve of Type Ib supernovae for helium-core masses between 4 and 6 M⊙. We compute gamma-ray line shapes and fluxes and the Comptonized X-ray continuum resulting from the decay of the radioactive 56Co and 57Co isotopes that are synthesized by the explosion of the presupernova star (the suggested Wolf-Rayet or post-Wolf-Rayet star) with a Monte Carlo transport code. The expansion velocity, the total mass of the ejecta, the radial mixing of radioactivity in that ejecta, and the 56Ni yield effect both the strength and the evolution of the hard radiation. With the anticipated launch of Gamma Ray Observatory, we can hope to detect Type Ib supernovae to distances of 3 Mpc and utilize the characteristics of the gamma lines and X-ray spectrum to distinguish between differing Type Ib supernova models and to address their suggested relationship to Wolf-Rayet stars.

APA, Harvard, Vancouver, ISO, and other styles

5

GEHRELS, N., and J. K. CANNIZZO. "GAMMA-RAY BURSTS — OBSERVATIONS." International Journal of Modern Physics D 19, no. 06 (2010): 977–84. http://dx.doi.org/10.1142/s021827181001710x.

Full text

Abstract:

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high-energy emission.

APA, Harvard, Vancouver, ISO, and other styles

6

Zhang, H., I. M. Christie, M. Petropoulou, J. M. Rueda-Becerril, and D. Giannios. "Inverse Compton signatures of gamma-ray burst afterglows." Monthly Notices of the Royal Astronomical Society 496, no. 1 (2020): 974–86. http://dx.doi.org/10.1093/mnras/staa1583.

Full text

Abstract:

ABSTRACT The afterglow emission from gamma-ray bursts (GRBs) is believed to originate from a relativistic blast wave driven into the circumburst medium. Although the afterglow emission from radio up to X-ray frequencies is thought to originate from synchrotron radiation emitted by relativistic, non-thermal electrons accelerated by the blast wave, the origin of the emission at high energies (HE; ≳GeV) remains uncertain. The recent detection of sub-TeV emission from GRB 190114C by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) raises further debate on what powers the very high energy (VHE; ≳300 GeV) emission. Here, we explore the inverse Compton scenario as a candidate for the HE and VHE emissions, considering two sources of seed photons for scattering: synchrotron photons from the blast wave (synchrotron self-Compton or SSC) and isotropic photon fields external to the blast wave (external Compton). For each case, we compute the multiwavelength afterglow spectra and light curves. We find that SSC will dominate particle cooling and the GeV emission, unless a dense ambient infrared photon field, typical of star-forming regions, is present. Additionally, considering the extragalactic background light attenuation, we discuss the detectability of VHE afterglows by existing and future gamma-ray instruments for a wide range of model parameters. Studying GRB 190114C, we find that its afterglow emission in the Fermi-Large Area Telescope (LAT) band is synchrotron dominated. The late-time Fermi-LAT measurement (i.e. t ∼ 104 s), and the MAGIC observation also set an upper limit on the energy density of a putative external infrared photon field (i.e. ${\lesssim} 3\times 10^{-9}\, {\rm erg\, cm^{-3}}$), making the inverse Compton dominant in the sub-TeV energies.

APA, Harvard, Vancouver, ISO, and other styles

7

Parsotan, Tyler, Diego López-Cámara, and Davide Lazzati. "Photospheric Polarization Signatures from Long Gamma-Ray Burst Simulations." Astrophysical Journal 896, no. 2 (2020): 139. http://dx.doi.org/10.3847/1538-4357/ab910f.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

McIntyre, Justin I., Brian T. Schrom, Mathew W. Cooper, et al. "LaCl3:Ce coincidence signatures to calibrate gamma-ray detectors." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652, no. 1 (2011): 201–4. http://dx.doi.org/10.1016/j.nima.2011.02.072.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Burrows, Adam, and Lih-Sin The. "X- and gamma-ray signatures of type IA supernovae." Astrophysical Journal 360 (September 1990): 626. http://dx.doi.org/10.1086/169150.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Murase, Kohta, and Kunihito Ioka. "Closure Relations fore±Pair Signatures in Gamma‐Ray Bursts." Astrophysical Journal 676, no. 2 (2008): 1123–29. http://dx.doi.org/10.1086/527667.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Blanco, Carlos, J. Patrick Harding, and Dan Hooper. "Novel gamma-ray signatures of PeV-scale dark matter." Journal of Cosmology and Astroparticle Physics 2018, no. 04 (2018): 060. http://dx.doi.org/10.1088/1475-7516/2018/04/060.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Serpico, Pasquale D. "Gamma ray astrophysics and signatures of axion-like particles." Advances in Space Research 43, no. 3 (2009): 335–41. http://dx.doi.org/10.1016/j.asr.2008.10.025.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Bernardini, Maria Grazia. "Gamma-ray bursts and magnetars: Observational signatures and predictions." Journal of High Energy Astrophysics 7 (September 2015): 64–72. http://dx.doi.org/10.1016/j.jheap.2015.05.003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Slane, Patrick, Andrei Bykov, Donald C. Ellison, Gloria Dubner, and Daniel Castro. "Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures." Space Science Reviews 188, no. 1-4 (2014): 187–210. http://dx.doi.org/10.1007/s11214-014-0062-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Alamaniotis, Miltiadis, Chan K. Choi, and Lefteri H. Tsoukalas. "Application of Fireworks Algorithm in Gamma-Ray Spectrum Fitting for Radioisotope Identification." International Journal of Swarm Intelligence Research 6, no. 2 (2015): 102–25. http://dx.doi.org/10.4018/ijsir.2015040105.

Full text

Abstract:

Identification of radioisotopic signature patterns in gamma-ray spectra is of paramount importance in various applications of gamma spectroscopy. Therefore, there are several active research efforts to develop accurate and precise methods to perform automated spectroscopic analysis and subsequently recognize gamma-ray signatures. In this work, the authors present a new method for radioisotope identification in gamma-ray spectra obtained with a low resolution radiation detector. The method fits the obtained spectrum with a linear combination of known template signature patterns. Coefficients of the linear combination are evaluated by computing the solution of a single objective optimization problem, whose objective is the Theil-1 inequality coefficient. Optimization of the problem is performed by the Fireworks Algorithm, which identifies a set of coefficients that minimize the Theil-1 value. The computed coefficients are statistically tested for being significantly different than zero or not, and if at least one is found to be zero then the Fireworks Algorithm is used to reiterate fitting using the non-zero templates. Fitting iterations are continued up to the point that no linear coefficients are found to be zero. The output of the method is a list that contains the radioisotopes that have been identified in the measured spectrum. The method is tested on a set of both simulated and real experimental gamma-ray spectra comprised of a variety of isotopes, and compared to a multiple linear regression fitting, and genetic algorithm Theil-1 based fitting. Results demonstrate the potentiality of the Fireworks Algorithm based method, expressed as higher accuracy and similar precision over the other two tested methodologies for radioisotope signature pattern identification in the framework of gamma-ray spectrum fitting.

APA, Harvard, Vancouver, ISO, and other styles

16

PERNA, ROSALBA. "THE INTERACTION BETWEEN GAMMA-RAY BURSTS AND THEIR ENVIRONMENT." Modern Physics Letters A 18, no. 37 (2003): 2611–25. http://dx.doi.org/10.1142/s0217732303012234.

Full text

Abstract:

Gamma-ray Bursts (GRBs) are the most energetic and most relativistic phenomenon in the Universe. Understanding the nature of their progenitors is among the primary efforts of current research in high energy astrophysics, and their unmatched luminosity and other properties makes them ideal cosmological probes. This review summarizes the observational effects resulting from the interaction between the longer-wavelength radiation accompanying GRBs and their close environment. In particular, it discusses signatures that, in addition to providing powerful clues on the GRB progenitors, can also shed light on the physical characteristics, such as metallicity and dust content, of the GRB host galaxies. The last part of the article reviews the long-term signatures imprinted in the medium after a GRB explosion, particularly focusing on how we can identify GRB remnants in our own and nearby galaxies, and what we can learn from their identification.

APA, Harvard, Vancouver, ISO, and other styles

17

Canac, N. E., K. N. Abazajian, T. Tajima, T. Ebisuzaki, and S. Horiuchi. "Observational signatures of gamma-rays from bright blazars and wakefield theory." Monthly Notices of the Royal Astronomical Society 493, no. 2 (2020): 2229–37. http://dx.doi.org/10.1093/mnras/staa338.

Full text

Abstract:

ABSTRACT Gamma-ray observations have revealed strong variability in blazar luminosities in the gamma-ray band over time-scales as short as minutes. We show, for the first time, that the correlation of the spectrum with intensity is consistent with the behaviour of the luminosity variation of blazar spectral energy distributions (SEDs) along a blazar sequence for low synchrotron peak blazars. We show that the observational signatures of variability with flux are consistent with wakefield acceleration of electrons initiated by instabilities in the blazar accretion disc. This mechanism reproduces the observed time variations as short as 100 s. The wakefield mechanism also predicts a reduction of the electron spectral index with increased gamma-ray luminosity, which could be detected in higher energy observations well above the inverse Compton peak.

APA, Harvard, Vancouver, ISO, and other styles

18

Frontera, F., L. Amati, R. Farinelli, et al. "COMPTONIZATION SIGNATURES IN THE PROMPT EMISSION OF GAMMA-RAY BURSTS." Astrophysical Journal 779, no. 2 (2013): 175. http://dx.doi.org/10.1088/0004-637x/779/2/175.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Hakkila, Jon, and Robert D. Preece. "GAMMA-RAY BURST PULSE SHAPES: EVIDENCE FOR EMBEDDED SHOCK SIGNATURES?" Astrophysical Journal 783, no. 2 (2014): 88. http://dx.doi.org/10.1088/0004-637x/783/2/88.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Granot, Jonathan, and Abraham Loeb. "Chromatic Signatures in the Microlensing of Gamma-Ray Burst Afterglows." Astrophysical Journal 551, no. 1 (2001): L63—L66. http://dx.doi.org/10.1086/319843.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Kotera, K., D. Allard, and M. Lemoine. "Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays." Astronomy & Astrophysics 527 (January 24, 2011): A54. http://dx.doi.org/10.1051/0004-6361/201015259.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Weth, C., P. Meszaros, T. Kallman, and M. J. Rees. "Early X‐Ray/Ultraviolet Line Signatures of Gamma‐Ray Burst Progenitors and Hypernovae." Astrophysical Journal 534, no. 2 (2000): 581–86. http://dx.doi.org/10.1086/308792.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Jóhannesson, Guđlaugur, and Troy A. Porter. "Signatures of Recent Cosmic-Ray Acceleration in the High-latitude Gamma-Ray Sky." Astrophysical Journal 917, no. 1 (2021): 30. http://dx.doi.org/10.3847/1538-4357/ac01c9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Musiimenta, Blessing, Bruno Sversut Arsioli, Edward Jurua та Tom Mutabazi. "A search for new γ-ray blazars from infrared selected candidates". Proceedings of the International Astronomical Union 15, S356 (2019): 329–31. http://dx.doi.org/10.1017/s1743921320003257.

Full text

Abstract:

AbstractWe present a systematic study of gamma-ray blazar candidates based on a sample of 40 objects taken from the WIBR catalogue. By using a likelihood analysis, 26 of the 40 sources showed significant gamma-ray signatures ⩾ 3σ. Using high-energy test statistics (TS) maps, we confirm 8 sources, which are completely new, and show another 15 promising γ-ray candidates. The results from this analysis show that a multi-frequency approach can help to improve the current description of the gamma-ray sky.

APA, Harvard, Vancouver, ISO, and other styles

25

Galper, A. M., O. Adriani, R. L. Aptekar, et al. "Characteristics of the GAMMA-400 gamma-ray telescope for searching for dark matter signatures." Bulletin of the Russian Academy of Sciences: Physics 77, no. 11 (2013): 1339–42. http://dx.doi.org/10.3103/s1062873813110105.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Diehl, Roland. "Gamma-ray line measurements from supernova explosions." Proceedings of the International Astronomical Union 12, S331 (2017): 157–63. http://dx.doi.org/10.1017/s1743921317004343.

Full text

Abstract:

AbstractGamma ray lines are expected to be emitted as part of the afterglow of supernova explosions, because radioactive decay of freshly synthesised nuclei occurs. Significant radioactive gamma ray line emission is expected from56Ni and44Ti decay on time scales of the initial explosion (56Ni, τ ~days) and the young supernova remnant (44Ti,τ ~90 years). Less specific, and rather informative for the supernova population as a whole, are lessons from longer lived isotopes such as26Al and60Fe. From isotopes of elements heavier than iron group elements, any interesting gamma-ray line emission is too faint to be observable. Measurements with space-based gamma-ray telescopes have obtained interesting gamma ray line emissions from two core collapse events, Cas A and SN1987A, and one thermonuclear event, SN2014J. We discuss INTEGRAL data from all above isotopes, including all line and continuum signatures from these two objects, and the surveys for more supernovae, that have been performed by gamma ray spectrometry. Our objective here is to illustrate what can be learned from gamma-ray line emission properties about the explosions and their astrophysics.

APA, Harvard, Vancouver, ISO, and other styles

27

Gao, He, and Peter Mészáros. "Reverse Shock Emission in Gamma-Ray Bursts Revisited." Advances in Astronomy 2015 (2015): 1–16. http://dx.doi.org/10.1155/2015/192383.

Full text

Abstract:

A generic synchrotron external shock model is the widely preferred paradigm used to interpret the broadband afterglow data of gamma-ray bursts (GRBs), including predicted observable signatures from a reverse shock which have been confirmed by observations. Investigations of the nature of the reverse shock emission can provide valuable insights into the intrinsic properties of the GRB ejecta. Here we briefly review the standard and the extended models of the reverse shock emission, discussing the connection between the theory and observations, including the implications of the latest observational advances.

APA, Harvard, Vancouver, ISO, and other styles

28

RUFFINI, REMO, FEDERICO FRASCHETTI, LUCA VITAGLIANO, and SHE-SHENG XUE. "OBSERVATIONAL SIGNATURES OF AN ELECTROMAGNETIC OVERCRITICAL GRAVITATIONAL COLLAPSE." International Journal of Modern Physics D 14, no. 01 (2005): 131–41. http://dx.doi.org/10.1142/s0218271805006146.

Full text

Abstract:

We present theoretical predictions for the spectral, temporal and intensity signatures of the electromagnetic radiation emitted during the process of the gravitational collapse of a stellar core to a black hole, during which electromagnetic field strengths rise over the critical value for e+e- pair creation. The last phases of this gravitational collapse are studied, leading to the formation of a black hole with a subcritical electromagnetic field, likely with zero charge, and an outgoing pulse of initially optically thick e+e--photon plasma. Such a pulse reaches transparency at Lorentz gamma factors of 102–104. We find a clear signature in the outgoing electromagnetic signal, drifting from a soft to a hard spectrum, on very precise time-scales and with a very specific intensity modulation. The relevance of these theoretical results for the understanding of short gamma-ray bursts is outlined.

APA, Harvard, Vancouver, ISO, and other styles

29

Hooper, Dan, and Pasquale D. Serpico. "Angular signatures of dark matter in the diffuse gamma ray background." Journal of Cosmology and Astroparticle Physics 2007, no. 06 (2007): 013. http://dx.doi.org/10.1088/1475-7516/2007/06/013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Lopez-Camara, Diego, William H. Lee, and Enrico Ramirez-Ruiz. "GAMMA-RAY BURST PRODUCTION AND SUPERNOVA SIGNATURES IN SLOWLY ROTATING COLLAPSARS." Astrophysical Journal 692, no. 1 (2009): 804–15. http://dx.doi.org/10.1088/0004-637x/692/1/804.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Baring, Matthew G. "Temporal Evolution of Pair Attenuation Signatures in Gamma‐Ray Burst Spectra." Astrophysical Journal 650, no. 2 (2006): 1004–19. http://dx.doi.org/10.1086/506960.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Ezeh, Sunny C., Wilfred A. Mode, Berti M. Ozumba, and Nura A. Yelwa. "Sedimentology and ichnology of Neogene Coastal Swamp deposits in the Niger Delta Basin, Nigeria." Geologos 22, no. 3 (2016): 191–200. http://dx.doi.org/10.1515/logos-2016-0020.

Full text

Abstract:

Abstract Often analyses of depositional environments from sparse data result in poor interpretation, especially in multipartite depositional settings such as the Niger Delta. For instance, differentiating channel sandstones, heteroliths and mudstones within proximal environments from those of distal facies is difficult if interpretations rely solely on well log signatures. Therefore, in order to achieve an effective and efficient interpretation of the depositional conditions of a given unit, integrated tools must be applied such as matching core descriptions with wireline log signature. In the present paper cores of three wells from the Coastal Swamp depositional belt of the Niger Delta are examined in order to achieve full understanding of the depositional environments. The well sections comprise cross-bedded sandstones, heteroliths (coastal and lower shoreface) and mudstones that were laid down in wave, river and tidal processes. Interpretations were made from each data set comprising gamma ray logs, described sedimentological cores showing sedimentary features and ichnological characteristics; these were integrated to define the depositional settings. Some portions from one of the well sections reveal a blocky gamma ray well log signature instead of a coarsening-upward trend that characterises a shoreface setting while in other wells the signatures for heteroliths at some sections are bell blocky in shaped rather than serrated. Besides, heteroliths and mudstones within the proximal facies and those of distal facies were difficult to distinguish solely on well log signatures. However, interpretation based on sedimentology and ichnology of cores from these facies was used to correct these inconsistencies. It follows that depositional environment interpretation (especially in multifarious depositional environments such as the Niger Delta) should ideally be made together with other raw data for accuracy and those based solely on well log signatures should be treated with caution.

APA, Harvard, Vancouver, ISO, and other styles

33

Mitchell, A. M. W., G. P. Rowell, S. Celli, and S. Einecke. "Using interstellar clouds to search for Galactic PeVatrons: gamma-ray signatures from supernova remnants." Monthly Notices of the Royal Astronomical Society 503, no. 3 (2021): 3522–39. http://dx.doi.org/10.1093/mnras/stab667.

Full text

Abstract:

ABSTRACT Interstellar clouds can act as target material for hadronic cosmic rays; gamma rays subsequently produced through inelastic proton–proton collisions and spatially associated with such clouds can provide a key indicator of efficient particle acceleration. However, even in the case that particle acceleration proceeds up to PeV energies, the system of accelerator and nearby target material must fulfil a specific set of conditions in order to produce a detectable gamma-ray flux. In this study, we rigorously characterize the necessary properties of both cloud and accelerator. By using available supernova remnant (SNR) and interstellar cloud catalogues, we produce a ranked shortlist of the most promising target systems, those for which a detectable gamma-ray flux is predicted, in the case that particles are accelerated to PeV energies in a nearby SNR. We discuss detection prospects for future facilities including CTA, LHAASO and SWGO; and compare our predictions with known gamma-ray sources. The four interstellar clouds with the brightest predicted fluxes &gt;100 TeV identified by this model are located at (l,b) = (330.05, 0.13), (15.82, −0.46), (271.09, −1.26), and (21.97, −0.29). These clouds are consistently bright under a range of model scenarios, including variation in the diffusion coefficient and particle spectrum. On average, a detectable gamma-ray flux is more likely for more massive clouds; systems with lower separation distance between the SNR and cloud; and for slightly older SNRs.

APA, Harvard, Vancouver, ISO, and other styles

34

Sardet, A., B. Pérot, C. Carasco, et al. "Gamma signatures of the C-BORD Tagged Neutron Inspection System." EPJ Web of Conferences 170 (2018): 07011. http://dx.doi.org/10.1051/epjconf/201817007011.

Full text

Abstract:

In the frame of C-BORD project (H2020 program of the EU), a Rapidly relocatable Tagged Neutron Inspection System (RRTNIS) is being developed to non-intrusively detect explosives, chemical threats, and other illicit goods in cargo containers. Material identification is performed through gamma spectroscopy, using twenty NaI detectors and four LaBr3 detectors, to determine the different elements composing the inspected item from their specific gamma signatures induced by fast neutrons. This is performed using an unfolding algorithm to decompose the energy spectrum of a suspect item, selected by X-ray radiography and on which the RRTNIS inspection is focused, on a database of pure element gamma signatures. This paper reports on simulated signatures for the NaI and LaBr3 detectors, constructed using the MCNP6 code. First experimental spectra of a few elements of interest are also presented.

APA, Harvard, Vancouver, ISO, and other styles

35

Carneiro, Cleyton de Carvalho, Stephen James Fraser, Alvaro Penteado Crósta, Adalene Moreira Silva, and Carlos Eduardo de Mesquita Barros. "Semiautomated geologic mapping using self-organizing maps and airborne geophysics in the Brazilian Amazon." GEOPHYSICS 77, no. 4 (2012): K17—K24. http://dx.doi.org/10.1190/geo2011-0302.1.

Full text

Abstract:

A self-organizing map (SOM) approach has been used to provide an integrated spatial analysis and classification of airborne geophysical data collected over the Brazilian Amazon. Magnetic and gamma ray spectrometric data were used to extract geophysical signatures related to the spatial distribution of rock types and to produce a geologic map over the prospective Anapu-Tuerê region. Particular emphasis was given to discriminating and identifying rock types, and the processes related to gold mineralization, which are known to occur in the Anapu-Tuerê region. SOM was able to identify and map distinctive geophysical signatures related to the various geologic units identified on the published geologic map. Furthermore, SOM was able to identify and enhance very subtle signatures derived jointly from the magnetic and gamma ray spectrometric data that could be related to geologic processes present in the area. These results demonstrate the effectiveness of using SOM as a tool for geophysical data analysis and for semiautomated mapping in regions such as the Amazon.

APA, Harvard, Vancouver, ISO, and other styles

36

Sparre, M., and R. L. C. Starling. "A search for thermal X-ray signatures in gamma-ray bursts - II. The Swift sample." Monthly Notices of the Royal Astronomical Society 427, no. 4 (2012): 2965–74. http://dx.doi.org/10.1111/j.1365-2966.2012.21858.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Acero, F., A. Bamba, S. Casanova, et al. "Gamma-ray signatures of cosmic ray acceleration, propagation, and confinement in the era of CTA." Astroparticle Physics 43 (March 2013): 276–86. http://dx.doi.org/10.1016/j.astropartphys.2012.05.024.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Barkana, Rennan, та Abraham Loeb. "Gamma‐Ray Bursts versus Quasars: Lyα Signatures of Reionization versus Cosmological Infall". Astrophysical Journal 601, № 1 (2004): 64–77. http://dx.doi.org/10.1086/380435.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

El Kanawati, Wassila, Cedric Carasco, Bertrand Perot, et al. "Gamma-Ray Signatures Improvement of the EURITRACK Tagged Neutron Inspection System Database." IEEE Transactions on Nuclear Science 57, no. 5 (2010): 2879–85. http://dx.doi.org/10.1109/tns.2010.2058864.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Mitrofanov, Igor G., Alexei S. Pozanenko, Michael S. Briggs, et al. "Generic Signatures of the Time Profiles of BATSE Cosmic Gamma‐Ray Bursts." Astrophysical Journal 504, no. 2 (1998): 925–34. http://dx.doi.org/10.1086/306093.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Struminsky, Alexei. "Gamma-Ray Solar Flares and In Situ Particle Acceleration." Proceedings of the International Astronomical Union 13, S335 (2017): 43–48. http://dx.doi.org/10.1017/s1743921317008067.

Full text

Abstract:

AbstractAt present two concurrent paradigms of solar energetic particle (SEP) origin exist: acceleration directly in the flare site or by the shock wave of coronal mass ejection (CME). Active discussions on a relative role of flares and coronal mass ejections for SEP acceleration and propagation are continuous until now. In my opinion only future observations of solar high energy γ–emission with better spectral, spatial and temporal resolution may clarify this issue. In my report I discuss possible signatures of the flare and shock acceleration processes. What is a picture provided by the current instruments? What can we expect to observe with a perfect instrument in high energy gamma rays in one or another case on a time scale of impulsive and long decay flare phases?

APA, Harvard, Vancouver, ISO, and other styles

42

TELEZHINSKY, IGOR, and BOHDAN HNATYK. "HIGH ENERGY SIGNATURES OF POST ADIABATIC SUPERNOVA REMNANTS." Modern Physics Letters A 22, no. 35 (2007): 2617–29. http://dx.doi.org/10.1142/s0217732307025601.

Full text

Abstract:

Between the well-known adiabatic and radiative stages of the Supernova remnant (SNR) evolution there is, in fact, a transition stage with a duration comparable to the duration of adiabatic one. Physical existence of the transition stage is motivated by cooling of some part of the downstream hot gas with formation of a thin cold shell that is joined to a shell of swept up interstellar medium (ISM). We give an approximate analytical method for full hydrodynamical description of the transition stage. On its base we investigate the evolution of X-ray and γ-ray radiation during this stage. It is shown that formation of a dense shell during the transition stage is accompanied by the decrease of X-ray luminosity because of hot gas cooling and increase of gamma-ray flux according to the increase of target proton density and CR energy in the newly born shell. The role of nonuniformity of ISM and its influence on the high energy fluxes from the SNRs is also discussed.

APA, Harvard, Vancouver, ISO, and other styles

43

Khan, Muhammad Younis, Guo-Qiang Xue, Wei-Ying Chen, and Cyril D. Boateng. "Investigation of Groundwater In-rush Zone using Petrophysical Logs and Short-offset Transient Electromagnetic (SOTEM) Data." Journal of Environmental and Engineering Geophysics 25, no. 3 (2020): 433–37. http://dx.doi.org/10.32389/jeeg18-111.

Full text

Abstract:

The water burst from the Ordovician limestone underlain by the Permo-Carboniferous coal seams have potential to trigger coalmine hazards in Northern China. Therefore, it is crucial to identify and accurately map the water enrichment zones and delineate coal seams using an integrated approach based on surface TEM and subsurface wireline log information to avoid water-inrush hazard and ensure safe production of coal. We inverted surface based TEM data using 1-D Occam inversion to identify the conductive anomaly and then further quantified the zone of interest by gamma and resistivity logs. 1-D Occam inversion results show conductive zone around 370 m while higher resistivity and lower gamma ray log signatures were observed against coal seams. Groundwater inrush zone falls within the mid-range gamma ray and resistivity interval as shown on the petrophysical logs. The distinct log signatures (low gamma-ray and high resistivity values) clearly indicated coal seams at depth of 410 and 470 m and subsequently the log trends were used to distinguish between coal units and more permeable sands. The magnitude and the variability of these parameters in the borehole are attributed to the subsurface stratigraphic heterogeneity. They can be key clues for interpretation of depositional facies of coal-bearing sequence and may also be used as a constraint in characterization of groundwater enrichment zone.

APA, Harvard, Vancouver, ISO, and other styles

44

Ramos, Lara Nigro Rodrigues Alves, Augusto César Bittencourt Pires, and Catarina Labouré Benfica Toledo. "AIRBORNE GAMMA-RAY SPECTROMETRIC AND MAGNETIC SIGNATURES OF FAZENDA NOVA REGION, EAST PORTION OF ARENÓPOLIS MAGMATIC ARC, GOIÁS." Revista Brasileira de Geofísica 32, no. 1 (2014): 123. http://dx.doi.org/10.22564/rbgf.v32i1.401.

Full text

Abstract:

ABSTRACT. Airborne geophysical data are an important tool for the interpretation of geological features. The variations observed in airborne magnetic and gamma-ray spectrometric data are typically used to differentiate geological units and delimit structures. In this context, this study aims to use gamma-ray spectrometric and magnetic airborne data to support the geological mapping in the Fazenda Nova region, located in the east portion of the Arenópolis Magmatic Arc. The processing of the gamma-ray spectrometric data consisted of generating K, U, Th, total count, gamma-ray spectrometric ratios and ternary images. The anomalous magnetic field processing and enhancing generated the magnetic maps, which provided information about the structural framework of the area, while the gamma-ray profiles and images allowed the delineation of the geologic-geophysical domains. Fifteen domains were individualized, interpreted especially from ternary images, which displayed a good relation with the granite bodies mapped and indicated different rocks associated with the Goiás Alkaline Province, contributing to improving the geological knowledge of the area. Keywords: airborne geophysics, gamma-ray spectrometric, Arenópolis Magmatic Arc. RESUMO. Dados aerogeofísicos consistem em uma importante ferramenta para a interpretação de feições geológicas. Variações observadas em dados magnéticos e de espectrometria gama aéreos são usualmente utilizadas para a discriminação de unidades geológicas e delimitação de estruturas. Neste contexto, este estudo tem como objetivo o uso de imagens derivadas do processamento de dados magnéticos e gamaespectrométricos aéreos no suporte ao mapeamento geológico na região de Fazenda Nova, localizada na porção leste do Arco Magmático de Arenópolis. Para os dados gamaespectrométricos, o processamento consistiu na geração de imagens dos canais K, U, Th e Contagem Total, além das razões entre os canais e as imagens ternárias. O processamento e realce do campo magnético anômalo geraram as imagens magnéticas, as quais forneceram informações sobre o arcabouço estrutural da área, enquanto que imagens e perfis aeroradiométricos permitiram a delimitação dos domínios litogeofísicos. Foram individualizados 15 domínios, interpretados principalmente a partir das imagens ternárias, os quais apresentaram forte correlação com os corpos graníticos mapeados na região e delimitaram diferentes rochas associadas à Província Alcalina de Goiás, contribuindo para o aprimoramento do conhecimento geológico da região.Palavras-chave: aerogeofísica, gamaespectrometria, Arco Magmático de Arenópolis.

APA, Harvard, Vancouver, ISO, and other styles

45

Giblin, T. W., V. Connaughton, J. van Paradijs, et al. "Extended Power‐Law Decays in BATSE Gamma‐Ray Bursts: Signatures of External Shocks?" Astrophysical Journal 570, no. 2 (2002): 573–87. http://dx.doi.org/10.1086/339622.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Kocevski, Daniel, and Vahe Petrosian. "ON THE LACK OF TIME DILATION SIGNATURES IN GAMMA-RAY BURST LIGHT CURVES." Astrophysical Journal 765, no. 2 (2013): 116. http://dx.doi.org/10.1088/0004-637x/765/2/116.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Yang, H. Y. Karen, M. Ruszkowski, and E. Zweibel. "The Fermi bubbles: gamma-ray, microwave and polarization signatures of leptonic AGN jets." Monthly Notices of the Royal Astronomical Society 436, no. 3 (2013): 2734–46. http://dx.doi.org/10.1093/mnras/stt1772.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

IZZO, LUCA, CARLO LUCIANO BIANCO, MARCO MUCCINO, ANA VIRGINIA PENACCHIONI, and REMO RUFFINI. "THERMAL EMISSION IN GRBS: THE CASE OF GRB 090618." International Journal of Modern Physics: Conference Series 23 (January 2013): 202–7. http://dx.doi.org/10.1142/s2010194513011318.

Full text

Abstract:

The identification of thermal signatures in the spectra of Gamma Ray Bursts (GRBs) has become possible now, thanks especially to the modern space missions dedicated to their observations. There are several models in literature that take into account the presence of a thermal emission, in particular in the early emission of a GRB. In this work we discuss the case of GRB 090618, where thermal signatures in the early γ and X-rays have been observed.

APA, Harvard, Vancouver, ISO, and other styles

49

Zhang, Bing, Peter Mészáros та Junfeng Wang. "Some Recent Developments in γ-ray Burst Afterglow and Prompt Emission Models". Symposium - International Astronomical Union 214 (2003): 311–20. http://dx.doi.org/10.1017/s0074180900194641.

Full text

Abstract:

Extensive observational campaigns of afterglow hunting have greatly enriched our understanding of the gamma-ray burst (GRB) phenomenon. Efforts have been made recently to explore some afterglow properties or signatures that will be tested by the on-going or the future observational campaigns yet come. These include the properties of GRB early afterglows in the temporal domain; the GeV-TeV afterglow signatures in the spectral domain; as well as a global view about the GRB universal structured jet configuration. These recent efforts are reviewed. Within the standard cosmological fireball model, the very model(s) responsible for the GRB prompt emission is (are) not identified. These models are critically reviewed and confronted with the current data.

APA, Harvard, Vancouver, ISO, and other styles

50

Starling, R. L. C., K. L. Page, A. Pe'er, A. P. Beardmore, and J. P. Osborne. "A search for thermal X-ray signatures in gamma-ray bursts - I. Swift bursts with optical supernovae." Monthly Notices of the Royal Astronomical Society 427, no. 4 (2012): 2950–64. http://dx.doi.org/10.1111/j.1365-2966.2012.22116.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Gamma ray signatures'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles