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1

STUDIES ON THE UTILIZATION OF INDUCED MUTATION FOR SUGAR BEET BREEDING. I. SENSITIVITY OF SUGAR BEET TO $gamma$-RAYS (Co⁶°)  

Microsoft Academic Search

Dry dormant seeds of sugar beet were irradiated with Co⁶° gamma ; rays of 40 to 1,000 kr in order to determine the radiosensitivity of this plant ; as a first step to the utilization of induced mutation for sugar beet breeding. ; It was found that even at 300 kr the seed showed a high germination rate, ; although

K. Syakudo; A. Ujihara

1959-01-01

2

Mutagenesis at the ad-3A and ad-3B loci haploid UV-sensitive strains of Neurospora crassa. III. Comparison of dose-response curves for inactivation and mutation induced by gamma-rays.  

PubMed

Gamma-Ray-induced inactivation and induction of mutations at the ad-3A and ad-3B loci of Neurospora crassa have been compared among 6 different UV-sensitive strains and a standard wild-type strain. The 6 strains show varying degrees of sensitivity to gamma-ray-induced inactivation, with the relative sensitivity at 37% survival being uvs-6 greater than upr-1 greater than uvs-2 greater than uvs-3 greater than wild-type greater than uvs-5 greater than uvs-4. Studies on the induction of ad-3 mutants by gamma-rays show that when the dose-response curve (expressed in terms of ad-3 mutants among the surviving colonies) of the UV-sensitive strains are compared with wild-type, the 2 excision-repair-deficient mutants uvs-2 and upr-1 exhibit enhanced ad-3 mutant frequencies, uvs-3 exhibits reduced ad-3 mutant frequencies whereas both uvs-4 and uvs-5 show lower mutant frequencies than wild-type. PMID:6454839

Schpbach, M E; de Serres, F J

1981-03-01

3

Induced Background in the Mars Observer Gamma-Ray Spectrometer  

NASA Technical Reports Server (NTRS)

Gamma-Ray Spectrometers in space must necessarily work in an environment of a background of lines due to natural and cosmic-ray induced radioactivity and lines due to prompt emission following nuclear reactions caused by primary and secondary cosmic rays. The Gamma-Ray Spectrometer (GRS) on the Mar Observer mission has provided important data allowing one to estimate for future missions the extent of the background due to cosmic rays. These data will help in the design of instruments and in calculation of realistic background intensities that may effect the sensitivity of determining the intensity of lines of interest.

Boynton, William V.; Evans, Larry G.; Starr, Richard; Bruekner, Johnnes; Bailey, S. H.; Trombka, Jacob I.

1997-01-01

4

Neutron-induced gamma-ray production  

SciTech Connect

High resolution Ge detectors coupled with the WNR high-intensity, high-energy, pulsed neutron source at LAMPF recently have been used to measure a variety of reactions including (n,xn) for 1 {le} x {le} 11, (n,n{alpha}), (n,np), etc. The reactions are identified by the known gamma-ray energies of prompt transitions between the low lying states in the final nuclei. With our spallation neutron source cross section data are obtained at all neutron energies from a few MeV to over 200 MeV. Applications of the data range from assisting the interpretation of the planned Mars Observer mission to map the elemental composition of the martian surface, to providing data for nuclear model verification and understanding reaction mechanisms. For example, a study of the Pb(n,xn) reactions for 2 {le} x {le} 11 populating the first excited states of the even Pb isotopes is underway. These data will be used to test preequilibrium and other reaction models. 9 refs., 5 figs.

Nelson, R.O.; Drake, D.M.; Haight, R.C.; Laymon, C.M.; Wender, S.A.; Young, P.G. (Los Alamos National Lab., NM (USA)); Drosg, M.; Pavlik, A.; Vonach, H. (Vienna Univ. (Austria). Inst. fuer Radiumforschung und Kernphysik); Larson, D.C. (Oak Ridge National Lab., TN (USA))

1990-01-01

5

The measurement of gamma ray induced heating in a mixed neutron and gamma ray environment  

SciTech Connect

The problem of measuring the gamma heating in a mixed DT neutron and gamma ray environment was explored. A new detector technique was developed to make this measurement. Gamma heating measurements were made in a low-Z assembly irradiated with 14-Mev neutrons and (n, n{prime}) gammas produced by a Texas Nuclear Model 9400 neutron generator. Heating measurements were made in the mid-line of the lattice using a proportional counter operating in the Continuously-varied Bias-voltage Acquisition mode. The neutron-induced signal was separated from the gamma-induced signal by exploiting the signal rise-time differences inherent to radiations of different linear energy transfer coefficient, which are observable in a proportional counter. The operating limits of this measurement technique were explored by varying the counter position in the low-Z lattice, hence changing the irradiation spectrum observed. The experiment was modelled numerically to help interpret the measured results. The transport of neutrons and gamma rays in the assembly was modelled using the one- dimensional radiation transport code ANISN/PC. The cross-section set used for these calculations was derived from the ENDF/B-V library using the code MC{sup 2}-2 for the case of DT neutrons slowing down in a low-Z material. The calculated neutron and gamma spectra in the slab and the relevant mass-stopping powers were used to construct weighting factors which relate the energy deposition in the counter fill-gas to that in the counter wall and in the surrounding material. The gamma energy deposition at various positions in the lattice is estimated by applying these weighting factors to the measured gamma energy deposition in the counter at those locations.

Chiu, H.K.

1991-10-01

6

Detection of Neutrons Liberated from Beryllium by Gamma Rays: a New Technique for Inducing Radioactivity  

Microsoft Academic Search

We have observed that a radiation emitted from beryllium under the influence of radium gamma rays excites induced radioactivity in iodine, and we conclude that neutrons are liberated from beryllium by gamma rays.

Leo Szilard; T. A. Chalmers

1934-01-01

7

Neutron induced gamma-ray production data  

NASA Astrophysics Data System (ADS)

The capture reaction mechanisms are classified according to the hierarchy of quasiparticle numbers in the capture configurations - one quasiparticle (channel capture), three quasiparticles (doorway mechanism) and five or more quasiparticles (statistical processes). The nonstatistical effects in the 2 P and 3 S size resonance region of neutron strength function were systematically studied and the mass, shell and even-odd effects were explored. Two computer codes, GRS and GNASH-M, were developed and used for the calculations of neutron-induced photon production data in C-12, O-16, Al-27, Si-28, Fe-56, Cu-63-65, Au-197, and Pb-208 at the neutron energy region from thermal to 20 MeV.

Ho, Yukun

1991-11-01

8

Uranium-induced background of germanium gamma-ray spectrometers.  

PubMed

The uranium-induced background in eight high-resolution gamma-ray spectrometers was analyzed in order to identify the locations of its sources. On the basis of the energy dependence of the peak count rates, normalized to units of emission probability and detection probability, the contributions of the molecular sieve and the beryllium window were extracted. Based on the uncertainties achieved the contribution of the detector shields could not be observed. However, some correlations between the construction of the detectors and the values of the parameters describing the energy dependence were observed and the uranium activity in the beryllium windows was assessed. PMID:22728837

Korun, M; Maver Modec, P; Vodenik, B; Zorko, B

2012-08-01

9

Determination of the elemental distribution in a sample using neutron induced gamma-ray emission tomography  

Microsoft Academic Search

The factors that affect accurate, quantitative results to be obtained by neutron induced gamma-ray emission tomography are stated. The technique, which is a combination of neutron activation analysis with computerised gamma-ray emission tomography, would be enhanced by the use of multiple detector assemblies, in geometrical configurations, which simultaneously record the gamma-rays emitted and improve detection efficiency. Developments in the past

N. M. Spyrou; J. M. Sharaf; S. Rajeswaran; E. Mesbahi

1997-01-01

10

Oligonucleotide chip assay for quantification of gamma ray-induced single strand breaks.  

PubMed

An oligonucleotide chip assay was designed for direct quantification of single strand breaks (SSBs) induced by gamma-ray irradiation. The oligonucleotides used were 20-mers, which were short enough to produce only a single strand break within a single oligonucleotide. The two ends of the oligonucleotides were labeled with fluorescein and biotin, respectively. The biotinylated ends of the oligonucleotides were immobilized on a silicon wafer chip treated with (3-aminopropyl)triethoxysilane (APTES), glutaraldehyde, and avidin. The DNA fragments cleaved by gamma-ray irradiation were detected by a laser-induced fluorescence (LIF) detection system. The gamma-ray-induced SSBs were quantified using a calibration curve (fluorescence intensity versus gamma-ray dose) without the need for complicated mathematical calculation based on gel-based separation. The experimentally determined gamma-ray-induced SSBs yield was almost equal to the theoretical value derived from gel electrophoresis of plasmid DNAs and DNA surface coverage. PMID:19128912

Ki, Hyeon A; Kim, Min Jung; Pal, Sukdeb; Song, Joon Myong

2009-02-20

11

Changes in DNA base sequence induced by gamma-ray mutagenesis of lambda phage and prophage  

SciTech Connect

Mutations in the cI (repressor) gene were induced by gamma-ray irradiation of lambda phage and of prophage, and 121 mutations were sequenced. Two-thirds of the mutations in irradiated phage assayed in recA host cells (no induction of the SOS response) were G:C to A:T transitions; it is hypothesized that these may arise during DNA replication from adenine mispairing with a cytosine product deaminated by irradiation. For irradiated phage assayed in host cells in which the SOS response had been induced, 85% of the mutations were base substitutions, and in 40 of the 41 base changes, a preexisting base pair had been replaced by an A:T pair; these might come from damaged bases acting as AP (apurinic or apyrimidinic) sites. The remaining mutations were 1 and 2 base deletions. In irradiated prophage, base change mutations involved the substitution of both A:T and of G:C pairs for the preexisting pairs; the substitution of G:C pairs shows that some base substitution mechanism acts on the cell genome but not on the phage. In the irradiated prophage, frameshifts and a significant number of gross rearrangements were also found.

Tindall, K.R.; Stein, J.; Hutchinson, F.

1988-04-01

12

Lymphocytes from wasted mice express enhanced spontaneous and {gamma}-ray-induced apoptosis  

SciTech Connect

Mice bearing the autosomal recessive mutation wasted (wst/wst) display a disease pattern including faulty repair of DNA damage in lymphocytes after radiation exposure, neurologic abnormalities, and immunodeficiency. Many of the features of this mouse model have suggested a premature or increased spontaneous frequency of apoptosis in thymocytes; past work has shown an inability to establish cultured T cell lines, an abnormally high death rate of stimulated T cells in culture, and an increased sensitivity of T cells to the killing effects of ionizing radiations in wst/wst mice relative to controls. The experiments reported here were designed to examine splenic and thymic lymphocytes from wasted and control mice for signs of early apoptosis. Our results revealed enhanced expression of Rp-8 mRNA (associated with apoptosis) in thymic lymphocytes and reduced expression in splenic lymphocytes of wst/wst mice relative to controls; expression of Rp-2 and Td-30 mRNA (induced during apoptosis) were not detectable in spleen or thymus. Higher spontaneous DNA fragmentation was observed in wasted mice than in controls; however, {gamma}-ray-induced DNA fragmentation peaked at a lower dose and occurred to a greater extent in wasted mice relative to controls. These results provide evidence for high spontaneous and {gamma}-ray-induced apoptosis in T cells of wasted mice as a mechanism underlying the observed lymphocyte and DNA repair abnormalities.

Woloschak, G.E. [Argonne National Lab., IL (United States)]|[Loyola Univ. Medical Center, Maywood, IL (United States); Chang-Liu, Chin-Mei [Argonne National Lab., IL (United States); Chung, Jen; Libertin, C.R. [Loyola Univ. Medical Center, Maywood, IL (United States)

1993-09-01

13

Neutron induced background in the COMPTEL detector on the Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

Interactions of neutrons in a prototype of the Compton imaging telescope (COMPTEL) gamma ray detector for the Gamma Ray Observatory were studied to determine COMPTEL's sensitivity as a neutron telescope and to estimate the gamma ray background resulting from neutron interactions. The IUCF provided a pulsed neutron beam at five different energies between 18 and 120 MeV. These measurements showed that the gamma ray background from neutron interactions is greater than previously expected. It was thought that most such events would be due to interactions in the upper detector modules of COMPTEL and could be distinguished by pulse shape discrimination. Rather, the bulk of the gamma ray background appears to be due to interactions in passive material, primarily aluminum, surrounding the D1 modules. In a considerable fraction of these interactions, two or more gamma rays are produced simultaneously, with one interacting in the D1 module and the other interacting in the module of the lower (D2) detector. If the neutron interacts near the D1 module, the D1 D2 time of flight cannot distinguish such an event from a true gamma ray event. In order to assess the significance of this background, the flux of neutrons in orbit has been estimated based on observed events with neutron pulse shape signature in D1. The strength of this neutron induced background is estimated. This is compared with the rate expected from the isotropic cosmic gamma ray flux.

Morris, D. J.; Aarts, H.; Bennett, K.; Busetta, M.; Byrd, R.; Collmar, W.; Connors, A.; Diehl, R.; Eymann, G.; Foster, C.

1992-01-01

14

Neutron-induced gamma ray spectroscopy: Simulations for chemical mapping of planetary surfaces  

NASA Astrophysics Data System (ADS)

Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma ray lines that can be measured by a gamma ray spectrometer on board an orbiting spacecraft. These data can be used to determine the concentration of many elements in the surface of a planetary body, which enables us to recognize individual geological units and provides clues to the bulk composition and in turn the origin and evolution of the body. To investigate the gamma ray fluxes induced by accelerator neutrons, experiments were carried out by irradiating thin targets with neutrons of energies from 14 MeV to 0.025 eV. The neutron fluxes at target position were measured by foil activation techniques. The ratio of the epithermal to thermal neutron flux was determined to be 2.0, a value that is similar to that in the moon. Gamma rays in the energy range of 0.1 to 8 MeV emitted by the targets and the surrounding material were measured by a high-resolution germanium detector. Most of the gamma ray lines that are expected to be used for planetary gamma ray Spectroscopy were found in the recorded spectra. These spectra were unfolded, background was subtracted, and gamma ray attenuation corrections were made to obtain the corresponding gamma ray fluxes from the targets. The majority of gamma ray lines were narrow without noticeable Doppler broadening except for the very broad 4.4-MeV line of carbon and five asymmetric germanium lines produced by the detector itself. The agreement of measured gamma ray flux ratios with calculated flux ratios for neutron-capture reactions showed that thermal neutron data can be used for theoretical calculations of low-energy neutron-induced gamma ray fluxes. This study was a first step toward a more realistic simulation of cosmic-ray-induced gamma-ray production and it indicates the importance of accelerator irradiation experiments to future planetary missions.

Brckner, J.; Wnke, H.; Reedy, R. C.

15

Neutron-induced gamma-ray spectroscopy: simulations for chemical mapping of planetary surfaces  

SciTech Connect

Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma-ray lines that can be measured by a gamma-ray spectrometer on board of an orbiting spacecraft. These data can be used to determine the concentration of many elements in the surface of a planetary body, which provides clues to its bulk composition and in turn to its origin and evolution. To investigate the gamma rays made by neutron interactions, thin targets were irradiated with neutrons having energies from 14 MeV to 0.025 eV. By means of foil activation technique the ratio of epithermal to thermal neutrons was determined to be similar to that in the Moon. Gamma rays emitted by the targets and the surrounding material were detected by a high-resolution germanium detector in the energy range of 0.1 to 8 MeV. Most of the gamma-ray lines that are expected to be used for planetary gamma-ray spectroscopy were found in the recorded spectra and the principal lines in these spectra are presented. 58 refs., 7 figs., 9 tabs.

Brueckner, J.; Waenke, H.; Reedy, R.C.

1986-01-01

16

Detection of pulsed, bremsstrahlung-induced, prompt neutron capture gamma-rays with HPGe detector  

SciTech Connect

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy (up to 8-MeV) electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of bremsstrahlung photons are produced by each pulse of electrons. Interrogating neutrons are generated by the bremsstrahlung photons interacting within a photoneutron source material. The interactions of the neutrons within a target result in the emission of elemental characteristic gamma-rays. Spectrometry is performed by analyzing the photoneutron-induced prompt gamma-rays acquired between accelerator pulses with a unique, high-purity germanium (HPGe) gamma-ray detection system using a modified transistor reset preamplifier. The detection system, the experimental configuration, and the accelerator operation used to characterize the detection system performance are described. Using a 6.5 MeV electron accelerator and a beryllium metal photoneutron source, gamma-ray spectra were successfully acquired for Al, Cu, polyethylene, NaC1, and depleted uranium targets as soon as 30 {mu}s after each bremsstrahlung (or x-ray) flash.

Jones, J.L.

1996-08-01

17

Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced  

E-print Network

LETTERS Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced Lorentz-energy neutrinos12,13 . At these energies, the background level in neutrino detectors such as IceCube (currently under construction in Antarctica) is extremely low. We show that the detection of even a single neutrino

Loss, Daniel

18

Time correlation of cosmic-ray-induced neutrons and gamma rays at sea level  

E-print Network

Time correlation of cosmic-ray-induced neutrons and gamma rays at sea level G. Miloshevsky n , A and evaporation processes of air nuclei are time-correlated. The occurrence of their counts in a fixed time interval is not a random (Poisson) distribution, but rather time-correlated bursts of counts

Harilal, S. S.

19

Optimizing the gate-pulse width for fast neutron induced gamma-ray spectroscopy  

NASA Astrophysics Data System (ADS)

We used a pulsed 14 MeV neutron generator (NG) to acquire two concurrent gamma-ray spectra induced by inelastic neutron scattering (INS) and thermal neutron capture (TNC) in Si, O, and C, which are key elements in soil analyses. These separate spectra were acquired by gating the data acquisition system during the neutron pulse, to obtain an INS spectrum, and in between the neutron pulses, to obtain a TNC spectrum. Despite this separation, TNC gamma rays are still counted in the INS window due to the steady state achieved in the former reaction. With the NG operating at 10 kHz and a 25% duty cycle, the magnitude of the single-escape gamma rays from the Si 4.93 MeV gamma-ray peak in the TNC spectrum to the 4.43 MeV carbon region in the INS spectrum is 10.1% of the 4.93 MeV peak intensity. This percentage depends on the neutron repetition rate and duty cycle. It can be reduced to 4.9% by using a narrower gate-pulse that closely fits the neutron burst. We also show that under these conditions the net count rate in the individual peaks of soil elements, Si and O (6.13 MeV) of the TNC spectrum reaches a steady state between the neutron pulses, but the total count rate from the entire spectrum does not.

Mitra, Sudeep; Wielopolski, Lucian

2005-09-01

20

Proton-induced X-ray and gamma ray emission analysis of biological samples  

NASA Astrophysics Data System (ADS)

A 4.1 MeV external proton beam was employed to simultaneously induce X-ray emission (PIXE) and gamma ray emission (PIGE) in biological samples that included human colostrum, spermatozoa, teeth, tree-rings, and follicular fluids. The analytical method was developed to simultaneously determine the elements lithium (Z = 3) through uranium (Z = 92) in the samples. PIXE-PIGE experimental design is described as well as applications in environmental and medical fields.

Hall, Gene S.; Navon, Eliahu

1986-04-01

21

Induced Radioactivity in Recovered Skylab Materials. [gamma ray spectra  

NASA Technical Reports Server (NTRS)

Four radioactive isotopes found in aluminum and stainless steel samples from Skylab debris were recovered in Australia. The low-level activity was induced by high-energy protons and neutrons in the space environment. Measurements of the specific activities are given.

Fishman, G. J.; Meegan, C. A.

1980-01-01

22

The {alpha}-induced thick-target {gamma}-ray yield from light elements  

SciTech Connect

The {alpha}-induced thick-target {gamma}-ray yield from light elements has been measured in the energy range 5.6 MeV {le} E{sub {alpha}} {le} 10 MeV. The {gamma}-ray yield for > 2.1 MeV from thick targets of beryllium, boron nitride, sodium fluoride, magnesium, aluminum and silicon were measured using the {alpha}-particle beam from the Lawrence Berkeley Laboratories 88 in. cyclotron. The elemental yields from this experiment were used to construct the {alpha}-induced direct production {gamma}-ray spectrum from materials in the SNO detector, a large volume ultra-low background neutrino detector located in the Creighton mine near Sudbury, Canada. This background source was an order of magnitude lower than predicted by previous calculations. These measurements are in good agreement with theoretical calculations of this spectrum based on a statistical nuclear model of the reaction, with the gross high energy spectrum structure being reproduced to within a factor of two. Detailed comparison of experimental and theoretical excitation population distribution of several residual nuclei indicate the same level of agreement within experimental uncertainties.

Heaton, R.K. [Queen`s Univ., Kingston, ON (Canada). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States)

1994-10-01

23

Proton and gamma ray induced gain degradation in bipolar transistor  

NASA Astrophysics Data System (ADS)

This paper describes the results of the effect of 24 MeV proton and (CO)-C-60 gamma-irradiation on the collector characteristic., and forward current gain of commercial bipolar transistor (npn 2N2219A). The transistor has been exposed to these radiations in the biased condition and the collector characteristics and forward current gain have been measured as a function of proton fluence and gamma-dose. The observation is that both the proton and gamma-irradiation induce significant gain degradation in the transistor. The results are discussed in terms of displacement damage produced by energetic protons and gamma-radiation in the bulk of the semiconductor.

Kulkarni, S. R.; Sarma, A.; Joshi, G. R.; Ravindra, M.; Damle, R.

2003-09-01

24

Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses  

SciTech Connect

High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90 Degree-Sign collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF{sub 2} scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF{sub 2} scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

Taira, Y.; Toyokawa, H.; Kuroda, R. [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Yamamoto, N. [Nagoya University Synchrotron Radiation Research Center, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Adachi, M.; Tanaka, S.; Katoh, M. [UVSOR, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji-cho, Okazaki, Aichi 444-8585 (Japan)

2013-05-15

25

Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses  

NASA Astrophysics Data System (ADS)

High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90 collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

2013-05-01

26

Dose-rate effects of neutrons and gamma-rays on the induction of mutation and oncogenic transformation in plateau-phase mouse m5S cells.  

PubMed

The dose-rate effect of 252-californium neutrons was investigated using confluent cultures of mouse m5S cells. The relative biological effectiveness (RBE) of neutrons for oncogenic transformation was increased from 3.3 to 5.1 when the dose-rate was reduced from 1.8 to 0.12 cGy/min. Similarly, neutron RBE values for HPRT- mutation were 4.9 and 7.4 at dose-rates of 1.8 and 0.12 cGy/min, respectively. The increases in RBE as dose-rate was reduced were due mainly to diminished transformation- and mutation-induction by gamma-rays (the standard radiation). The yields of neutron-induced oncogenic transformation as well as neutron-induced mutation were constant for both dose rates. Our observation contrasts with reports by others using proliferating cells where both oncogenic transformation and mutation were enhanced with neutron exposure at a reduced dose-rate, the so-called inverse dose-rate effect. Since m5S cells are sensitive to postconfluent inhibition of cell division, this observation could be ascribed to cell growth conditions used in these experiments. The mechanism of the inverse dose-rate effect of neutrons suggests that the enhancement of neutron-induced mutation and oncogenic transformation at a reduced dose-rate is strongly associated with cell proliferation during exposure. PMID:8096859

Komatsu, K; Sawada, S; Takeoka, S; Kodama, S; Okumura, Y

1993-04-01

27

Fermi large area telescope observations of the cosmic-ray induced gamma-ray emission of the Earth's atmosphere  

Microsoft Academic Search

We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded 6.4106 photons with energies >100MeV and 250 hours total

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; E. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; R. Buehler; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; C. Cecchi; . elik; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. de Palma; S. W. Digel; E. Do Couto E Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; N. Gehrels; S. Germani; B. Giebels; N. Giglietto; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; E. Hays; D. Horan; R. E. Hughes; G. Jhannesson; A. S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Kndlseder; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. Makeev; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rain; R. Rando; M. Razzano; A. Reimer; O. Reimer; T. Reposeur; L. S. Rochester; A. Y. Rodriguez; M. Roth; H. F.-W. Sadrozinski; A. Sander; P. M. Saz Parkinson; C. Sgr; G. H. Share; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. S. Strickman; D. J. Suson; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2009-01-01

28

Formation of Millisecond Pulsars from Accretion Induced Collapse and Constraints on Pulsar Gamma Ray Burst Models  

E-print Network

We study accretion induced collapse of magnetized white dwarfs as an origin of millisecond pulsars. We apply magnetized accretion disk models to the pre-collapse accreting magnetic white dwarfs and calculate the white dwarf spin evolution. If the pulsar magnetic field results solely from the flux-frozen fossil white dwarf field, a typical millisecond pulsar is born with a field strength $\\sim 10^{11}-10^{12}G$. The uncertainty in the field strength is mainly due to the uncertain physical parameters of the magnetized accretion disk models. A simple correlation between the pulsar spin $\\Omega_*$ and the magnetic field $B_*$, $(\\Omega_*/10^4s^{-1})\\sim (B_{*}/10^{11}G)^{-4/5}$, is derived for a typical accretion rate $\\sim 5\\times 10^{-8}M_{\\sun}/yr$. This correlation remains valid for a wide pre-collapse physical conditions unless the white dwarf spin and the binary orbit are synchronized prior to accretion induced collapse. We critically examine the possibility of spin-orbit synchronization in close binary systems. Using idealized homogeneous ellipsoid models, we compute the electromagnetic and gravitational wave emission from the millisecond pulsars and find that electromagnetic dipole emission remains nearly constant while millisecond pulsars may spin up rather than spin down as a result of gravitational wave emission. We also derive the physical conditions under which electromagnetic emission from millisecond pulsars formed by accretion induced collapse can be a source of cosmological gamma-ray bursts. We find that relativistic beaming of gamma-ray emission and precession of gamma-ray emitting jets are required unless the dipole magnetic field strengths are $>10^{15}$G; such strong dipole fields are in excess of those allowed from the accretion induced collapse formation process except in spin-orbit synchronization.

Insu Yi; Eric G. Blackman

1997-04-28

29

Numerical simulations of planetary gamma-ray spectra induced by galactic cosmic rays  

SciTech Connect

The fluxes of cosmic-ray-produced gamma rays escaping from Mars were calculated using the LAHET Code System and basic nuclear data for {gamma}-ray production. Both surface water content and atmospheric thickness strongly affect the fluxes of {gamma}-ray lines escaping from Mars.

Masarik, J.; Reedy, R.C.

1994-07-01

30

Induced mutations in foxtail millet ( Setaria italica Beauv.)  

Microsoft Academic Search

Chlorophyll mutations induced by gamma rays, EMS and DES were studied in foxtail millet (Setaria italica), using two cultures, MU-1 (bristled) and MU-2 (non-bristled). No major differences in the mutagenic response of the two cultures were observed. The treatments included four doses of gamma rays (10Kr, 20Kr, 30Kr, 40Kr) and four durations (6 hrs, 12 hrs, 18 hrs, 24 hrs)

P. K. Gupta; Yashvir

1975-01-01

31

Magnetic Compton-induced pair cascade model for gamma-ray pulsars  

NASA Technical Reports Server (NTRS)

Electrons accelerated to relativistic energies in pulsar magnetospheres will Compton scatter surface thermal emission and nonthermal optical, UV, and soft X-ray emission to gamma-ray energies, thereby initiating a pair cascade through synchrotron radiation and magnetic pair production. This process is proposed as the origin of the high-energy radiation that has been detected from six isolated pulsars. We construct an analytic model of magnetic Compton scattering near the polar cap of isolated pulsar magnetospheres and present approximate analytic derivations for scattered spectra, electron energy-loss rates, and photon luminosities. A Monte Carlo simulation is used to model the pair cascade induced by relativistic electrons scattering photons through the cyclotron resonance. For simplicity, the primary electrons are assumed to be monoenergetic and the nonresonant emission is omitted. Assuming that the angle phi(sub B) between the magnetic and spin axes is approximately equal to the polar-cap angle theta(sub pc), this model can produce both double-peaked and broad single-peaked pulse profiles and account for the trend of harder gamma-ray spectra observed from older pulsars.

Sturner, Steven J.; Dermer, Charles D.; Michel, F. Curtis

1995-01-01

32

The Internal-collision-induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the PFD regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized (e.g., 1 <~ ? <~ 100). Similar to the internal shock (IS) model, the mini-shells interact internally at the radius R IS ~ ?2 c?t. Most of these early collisions, however, have little energy dissipation, but serve to distort the ordered magnetic field lines entrained in the ejecta. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and Ep in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT.

Zhang, Bing; Yan, Huirong

2011-01-01

33

Comparison of gamma-ray-induced chromosome ring and inversion frequencies  

SciTech Connect

A method was used to detect chromosome inversions as apparent or false sister chromatid exchanges (SCEs) in the first mitosis after {gamma} irradiation of human G{sub o} cells. Dose-response relationships for small inversions have not been measured and reported previously, but it has been assumed that these are induced with a frequency equal to that of their easily mesured asymmetrical counterpart, the interstitial deletion. Our experiments confirm this expectation. The results also demonstrate, as others have suggested, that in protocols where SCEs have been reported in the first postirradiation mitosis after incorporation of BrdU in the previous cell cycle, the X- or {gamma}-ray treatment of G{sub o}{sup {minus}} or G{sub 1}-phase cells produces virtually no true SCEs. 23 refs., 3 figs., 2 tabs.

Muehlmann, M.C.; Bedford, J.S. [Colorado State Univ., Fort Collins, CO (United States)

1995-08-01

34

Ion-induced gamma-ray detection of fast ions escaping from fusion plasmas  

SciTech Connect

A 12 12 pixel detector has been developed and used in a laboratory experiment for lost fast-ion diagnostics. With gamma rays in the MeV range originating from nuclear reactions {sup 9}Be(?, n?){sup 12}C, {sup 9}Be(d, n?){sup 12}C, and {sup 12}C(d, p?){sup 13}C, a high purity germanium (HPGe) detector measured a fine-energy-resolved spectrum of gamma rays. The HPGe detector enables the survey of background-gamma rays and Doppler-shifted photo peak shapes. In the experiments, the pixel detector produces a gamma-ray image reconstructed from the energy spectrum obtained from total photon counts of irradiation passing through the detector's lead collimator. From gamma-ray image, diagnostics are able to produce an analysis of the fast ion loss onto the first wall in principle.

Nishiura, M., E-mail: nishiura@ppl.k.u-tokyo.ac.jp; Mushiake, T. [Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561 (Japan); Doi, K.; Wada, M. [Graduate School of Science and Engineering, Doshisha University, Kyotanabe 610-0321 (Japan); Taniike, A.; Matsuki, T. [Graduate School of Maritime Sciences, Kobe University, Kobe 658-0022 (Japan); Shimazoe, K. [Graduate School of Engineering, The University of Tokyo, Tokyo 113-8654 (Japan); Yoshino, M. [Furukawa Co. Ltd., Tsukuba, Ibaraki 305-0856 (Japan); Nagasaka, T.; Tanaka, T.; Kisaki, M. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Fujimoto, Y.; Fujioka, K. [Institute of Laser Engineering, Osaka University, Osaka 565-0871 (Japan); Yamaoka, H. [RIKEN SPring-8 center, RIKEN, Sayo, Hyogo 679-5148 (Japan); Matsumoto, Y. [Tokushima Bunri University, Tokushima 770-8514 (Japan)

2014-11-15

35

Ion-induced gamma-ray detection of fast ions escaping from fusion plasmas  

NASA Astrophysics Data System (ADS)

A 12 12 pixel detector has been developed and used in a laboratory experiment for lost fast-ion diagnostics. With gamma rays in the MeV range originating from nuclear reactions 9Be(?, n?)12C, 9Be(d, n?)12C, and 12C(d, p?)13C, a high purity germanium (HPGe) detector measured a fine-energy-resolved spectrum of gamma rays. The HPGe detector enables the survey of background-gamma rays and Doppler-shifted photo peak shapes. In the experiments, the pixel detector produces a gamma-ray image reconstructed from the energy spectrum obtained from total photon counts of irradiation passing through the detector's lead collimator. From gamma-ray image, diagnostics are able to produce an analysis of the fast ion loss onto the first wall in principle.

Nishiura, M.; Doi, K.; Taniike, A.; Matsuki, T.; Shimazoe, K.; Mushiake, T.; Yoshino, M.; Nagasaka, T.; Fujimoto, Y.; Fujioka, K.; Tanaka, T.; Kisaki, M.; Yamaoka, H.; Matsumoto, Y.; Wada, M.

2014-11-01

36

Comparison of the biological effectiveness of 45 MeV C-ions and {gamma}-rays in inducing early and late effects in normal human primary fibroblasts  

SciTech Connect

Investigation of the mechanisms underlying the biological effects induced by densely ionizing radiation has relevant implications in both radiation protection and therapy. In particular, the possible advantages of hadrontherapy with respect to conventional radiotherapy in terms of high conformal tumor treatment and sparing of healthy tissues are well known. Further improvements are limited by lack of radiobiological knowledge, particularly about the specific cellular response to the damage induced by particles of potential interest for tumor treatment. This study compares early and late effects induced in AG01522 normal human primary fibroblasts by {gamma}-rays and C-ions having E {approx} 45 MeV/u at the cell entrance, corresponding to LET (in water) {approx} 49 keV/{mu}m. Different end points have been investigated, namely: cell killing and lethal mutation, evaluated as early and delayed reproductive cell death, respectively; chromosome damage, as measured by micronuclei induction (MN); DNA damage, in terms of DSB induction and repair, as measured by the H2AX phosphorylation/dephosphorylation kinetics. Linear dose-response relationships were found for cell killing and induction of lethal mutations, with RBEs of about 1.3 and 1.6 respectively, indicating that the presence of genomic instability is greater in the progeny of C-ions irradiated cells. H2AX phosphorylation/dephosphorylation kinetics have shown a maximum foci number at 30 min after irradiation, higher for {gamma}-rays than for C-ions. However, in the first 12 h the fraction of residual {gamma}-H2AX foci was higher for C-ions irradiated cells, indicating a lower removal rate, possibly related to multiple/more complex damage along the particle track, with respect to the sparse lesions produced by {gamma}-rays. MN induction, observed after 72 h from irradiation, was also greater for C-ions. Overall, these data indicate a more severe DNA damage induced by 45 MeV/u C-ions with respect to {gamma}-rays, likely responsible of an increased cellular misrepair, leading to the greater observed levels of chromosome damage and, eventually, of genomic instability. They give strong support to the idea that higher damage severity at molecular level, determined by the typical deposition pattern of densely ionizing radiation, is the earliest relevant factor for the more severe late effects at cellular level.

Fratini, E. [Centro studi e ricerche e museo storico della fisica E. Fermi, Roma (Italy); Balduzzi, M. [ENEA, Roma, Italy and INFN, Sezione Roma1-Gruppo Collegato Sanita, Roma (Italy); Antonelli, F.; Sorrentino, E.; Esposito, G. [Istituto Superiore di Sanita, Roma, Italy and INFN, Sezione Roma1-Gruppo Collegato Sanita, Roma (Italy); Cuttone, G.; Romano, F. [INFN-LNS, Catania (Italy); Dini, V.; Simone, G.; Campa, A.; Tabocchini, M. A. [stituto Superiore di Sanita, Roma, Italy and INFN, Sezione Roma1-Gruppo Collegato Sanita, Roma (Italy); Belli, M. [INFN, Sezione Roma1-Gruppo Collegato Sanita, Roma (Italy)

2013-07-18

37

Cross sections relevant to gamma-ray astronomy: Proton induced reactions  

Microsoft Academic Search

Gamma-ray production cross sections have been measured for the gamma-ray lines most strongly excited in the proton bombardment of ¹²C, ¹⁴N, ¹⁶O, ²°Ne, ²⁴Mg, ²⁸Si, and ⁵⁶Fe, for proton energies from threshold to 23 MeV. In addition, cross sections for the ¹⁴N(p,n)¹⁴O and ⁵⁶Fe(p,n)⁵⁶Co reactions were determined from delayed gamma-ray yields. Ge(Li) detectors were used. Tabulations of cross sections averaged

P. Dyer; D. Bodansky; A. G. Seamster; E. B. Norman; D. R. Maxson

1981-01-01

38

Cross sections relevant to gamma-ray astronomy: Alpha-particle-induced reactions  

Microsoft Academic Search

Gamma-ray production cross sections have been measured for the gamma-ray lines most strongly excited in the alpha-particle bombardments of ²°Ne, ²⁴Mg, ²⁷Al, ²⁸Si, and ⁵⁶Fe for alpha-particle energies from threshold to approximately 27 MeV. Tabulations of cross sections averaged over alpha-particle energy bins of 1 MeV are provided for calculations relevant to gamma-ray line astronomy. Examples are given of astrophysical

Alan G. Seamster; Eric B. Norman; Donald D. Leach; P. Dyer; D. Bodansky

1984-01-01

39

Charged Particle Induced Radiation damage of Germanium Detectors in Space: Two Mars Observer Gamma-Ray Detectors  

NASA Technical Reports Server (NTRS)

The Mars Observer Gamma-Ray Spectrometer (MO GRS) was designed to measure gamma-rays emitted by the Martian surface. This gamma-ray emission is induced by energetic cosmic-ray particles penetrating the Martian surface and producing many secondary particles and gamma rays. The MO GRS consisted of an high-purity germanium (HPGe) detector with a passive cooler. Since radiation damage due to permanent bombardment of energetic cosmic ray particles (with energies up to several GeV) was expected for the MO GRS HPGe crystal, studies on radiation damage effects of HPGe crystals were carried on earth. One of the HPGe crystals (paradoxically called FLIGHT) was similar to the MO GRS crystal. Both detectors, MO GRS and FLIGHT, contained closed-end coaxial n-type HPGe crystals and had the same geometrical dimensions (5.6 x 5.6 cm). Many other parameters, such as HV and operation temperature, differed in space and on earth, which made it somewhat difficult to directly compare the performance of both detector systems. But among other detectors, detector FLIGHT provided many useful data to better understand radiation damage effects.

Bruekner, J.; Koenen, M.; Evans, L. G.; Starr, R.; Bailey, S. H.; Boynton W. V.

1997-01-01

40

Turbulence induced additional deceleration in relativistic shock wave propagation: implications for gamma-ray burst  

NASA Astrophysics Data System (ADS)

The late afterglow of gamma-ray burst is believed to be due to progressive deceleration of the forward shock wave driven by the gamma-ray burst ejecta propagating in the interstellar medium. We study the dynamic effect of interstellar turbulence on shock wave propagation. It is shown that the shock wave decelerates more quickly than previously assumed without the turbulence. As an observational consequence, an earlier jet break will appear in the light curve of the forward shock wave. The scatter of the jet-corrected energy release for gamma-ray burst, inferred from the jet-break, may be partly due to the physical uncertainties in the turbulence/shock wave interaction. This uncertainties also exist in two shell collisions in the well-known internal shock model proposed for gamma-ray burst prompt emission. The large scatters of known luminosity relations of gamma-ray burst may be intrinsic and thus gamma-ray burst is not a good standard candle. We also discuss the other implications.

Liu, Xue-Wen

2012-11-01

41

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Miscellaneous tasks related to mission operations and data analysis for the Burst and Transient Source Experiment on the Gamma Ray Observatory, to collection, analysis, and interpretation of data from the Marshall Space Flight Center Very Low Frequency transient monitoring program, and to compilation and analysis of induced radioactivity data were performed. The results are summarized and relevant references are included.

Paciesas, William S.

1992-01-01

42

Detectability of Planck-scale-induced Blurring with Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

Microscopic fluctuations inherent to the fuzziness of spacetime at the Planck scale might accumulate in wavefronts propagating a cosmological distance and lead to noticeable blurring in an image of a pointlike source. Distant quasars viewed in the optical and ultraviolet with Hubble Space Telescope (HST) may show this weakly, and if real suggests a stronger effect should be seen for gamma-ray bursts (GRBs) in X-rays and ?-rays. Those telescopes, however, operate far from their diffraction limits. A description of how Planck-scale-induced blurring could be sensed at high energy, including with cosmic rays, while still agreeing with the HST results is discussed. It predicts dilated apparent source size and inflated uncertainties in positional centroids, effectively a threshold angular accuracy restricting knowledge of source location on the sky. These outcomes are found to be consistent with an analysis of the 10 highest-redshift GRB detections reported for the Fermi satellite. Confusion with photon cascade and scattering phenomena is also possible; prospects for a definitive multiwavelength measurement are considered.

Steinbring, Eric

2015-03-01

43

Clonally Expanding Thymocytes Having Lineage Capability in Gamma-Ray-Induced Mouse Atrophic Thymus  

SciTech Connect

Purpose: To characterize, in the setting of gamma-ray-induced atrophic thymus, probable prelymphoma cells showing clonal growth and changes in signaling, including DNA damage checkpoint. Methods and Materials: A total of 111 and 45 mouse atrophic thymuses at 40 and 80 days, respectively, after gamma-irradiation were analyzed with polymerase chain reaction for D-J rearrangements at the TCRbeta locus, flow cytometry for cell cycle, and Western blotting for the activation of DNA damage checkpoints. Results: Limited D-J rearrangement patterns distinct from normal thymus were detected at high frequencies (43 of 111 for 40-day thymus and 21 of 45 for 80-day thymus). Those clonally expanded thymocytes mostly consisted of CD4{sup +}CD8{sup +} double-positive cells, indicating the retention of lineage capability. They exhibited pausing at a late G1 phase of cell cycle progression but did not show the activation of DNA damage checkpoints such as gammaH2AX, Chk1/2, or p53. Of interest is that 17 of the 52 thymuses showing normal D-J rearrangement patterns at 40 days after irradiation showed allelic loss at the Bcl11b tumor suppressor locus, also indicating clonal expansion. Conclusion: The thymocytes of clonal growth detected resemble human chronic myeloid leukemia in possessing self-renewal and lineage capability, and therefore they can be a candidate of the lymphoma-initiating cells.

Yamamoto, Takashi; Morita, Shin-ichi [Department of Molecular Genetics, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan); Department of 3rd Internal Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan); Go, Rieka; Obata, Miki; Katsuragi, Yoshinori; Fujita, Yukari [Department of Molecular Genetics, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan); Maeda, Yoshitaka; Yokoyama, Minesuke [Center for Bioresource-Based Researches, Brain Research Institute, Niigata (Japan); Aoyagi, Yutaka [Department of 3rd Internal Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan); Ichikawa, Hitoshi [Genetics Division, National Cancer Center Research Institute, Tokyo (Japan); Mishima, Yukio [Department of Molecular Genetics, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan); Kominami, Ryo, E-mail: rykomina@med.niigata-u.ac.j [Department of Molecular Genetics, Niigata University Graduate School of Medical and Dental Sciences, Niigata (Japan)

2010-05-01

44

Early and Late Chromosome Damages in Human Lymphocytes Induced by Gamma Rays and Fe Ions  

NASA Technical Reports Server (NTRS)

Chromosomal translocations and inversions are considered stable, and cells containing these types of chromosome aberrations can survive multiple cell divisions. An efficient method to detect an inversion is multi-color banding fluorescent in situ hybridization (mBAND) which allows identification of both inter- and intrachromosome aberrations simultaneously. Post irradiation, chromosome aberrations may also arise after multiple cell divisions as a result of genomic instability. To investigate the stable or late-arising chromosome aberrations induced after radiation exposure, we exposed human lymphocytes to gamma rays and Fe ions ex vivo, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis and at several time intervals during the culture period post irradiation. With gamma irradiation, about half of the damages observed at first mitosis remained after 7 day- and 14 day- culture, suggesting the transmissibility of damages to the surviving progeny. Detailed analysis of chromosome break ends participating in exchanges revealed a greater fraction of break ends involved in intrachromosome aberrations in the 7- and 14-day samples in comparison to the fraction at first mitosis. In particular, simple inversions were found at 7 and 14 days, but not at the first mitosis, suggesting that some of the aberrations might be formed days post irradiation. In contrast, at the doses that produced similar frequencies of gamma-induced chromosome aberrations as observed at first mitosis, a significantly lower yield of aberrations remained at the same population doublings after Fe ion exposure. At these equitoxic doses, more complex type aberrations were observed for Fe ions, indicating that Fe ion-induced initial chromosome damages are more severe and may lead to cell death. Comparison between low and high doses of Fe ion irradiation in the induction of late damages will also be discussed.

Sunagawa, Mayumi; Zhang, Ye; Yeshitla, Samrawit; Kadhim, Munira; Wilson, Bobby; Wu, Honglu

2014-01-01

45

EMISSION PATTERNS AND LIGHT CURVES OF GAMMA RAYS IN THE PULSAR MAGNETOSPHERE WITH A CURRENT-INDUCED MAGNETIC FIELD  

SciTech Connect

We study the emission patterns and light curves of gamma rays in the pulsar magnetosphere with a current-induced magnetic field perturbation. Based on the solution of a static dipole with the magnetic field induced by some currents (perturbation field), we derive the solutions of a static as well as a retarded dipole with the perturbation field in the Cartesian coordinates. The static (retarded) magnetic field can be expressed as the sum of the pure static (retarded) dipolar magnetic field and the static (retarded) perturbation field. We use the solution of the retarded magnetic field to investigate the influence of the perturbation field on the emission patterns and light curves, and apply the perturbed solutions to calculate the gamma-ray light curves for the case of the Vela pulsar. We find that the perturbation field induced by the currents will change the emission patterns and then the light curves of gamma rays, especially for a larger perturbation field. Our results indicate that the perturbation field created by the outward-flowing (inward-flowing) electrons (positrons) can decrease the rotation effect on the magnetosphere and makes emission pattern appear to be smoother relative to that of the pure retarded dipole, but the perturbation field created by the outward-flowing (inward-flowing) positrons (electrons) can make the emission pattern less smooth.

Li, X.; Zhang, L., E-mail: lizhang@ynu.edu.cn [Department of Physics, Yunnan University, Kunming (China)

2011-12-20

46

Multiple fractions of gamma rays induced resistance to cis-dichloro-diammineplatinum (II) and methotrexate in human HeLa cells  

SciTech Connect

Previous irradiation could induce changes in the cell-sensitivity to additional cytotoxic agents. In this study we examined whether the sensitivity to additional cytotoxic agents was affected in cells irradiated with multiple fractions of gamma rays if these agents were given at the time when the lesions induced in DNA by radiation have already been repaired. Human cervix carcinoma HeLa cells were irradiated daily with 0.5 Gy of gamma rays five times a week for 6 weeks. When the fractionation regimen was completed, that is when the cells had accumulated the total dose of 15 Gy of gamma rays, the sensitivity of these cells to gamma rays, UV light, cis-dichlorodiammineplatinum (II) (cis-DDP), methotrexate (MTX), and hydroxyurea (HU) was examined and compared to control cells. Results revealed that preirradiated cells did not change sensitivity to gamma rays and UV light, but that they increased the resistance to cis-DDP, and MTX (especially for higher concentrations of MTX), and increased sensitivity to HU (for lower concentrations of HU). The increased resistance to cis-DDP was also measurable up to 30 days after the last dose of gamma rays. The results indicate that preirradiation of HeLa cells with multiple fractions of gamma rays could change their sensitivity to additional cytotoxic agents, and that this is a relatively long-lasting effect. Our results suggest that caution is needed in medical application of radiation combined with chemical treatment.

Osmak, M.; Perovic, S. (Ruder Boskovic Institute, Croatia (Yugoslavia))

1989-06-01

47

Possible effects on avionics induced by terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

Terrestrial gamma-ray flashes (TGFs) are impulsive (intrinsically sub-millisecond) events associated with lightning in powerful thunderstorms. TGFs turn out to be very powerful natural accelerators known to accelerate particles and generate radiation up to hundreds of MeV energies. The number ratio of TGFs over normal lightning has been measured in tropical regions to be near 10-4. We address in this Article the issue of the possible susceptibility of typical aircraft electronics exposed to TGF particle, gamma ray and neutron irradiation. We consider possible scenarios regarding the intensity, the duration, and geometry of TGFs influencing nearby aircraft, and study their effects on electronic equipment. We calculate, for different assumptions, the total dose and the dose-rate, and estimate single-event-effects. We find that in addition to the electromagnetic component (electrons/positrons, gamma rays) also secondary neutrons produced by gamma-ray photo production in the aircraft structure substantially contribute to single-event effects in critical semiconductors components. Depending on the physical characteristics and geometry, TGFs may deliver a large flux of neutrons within a few milliseconds in an aircraft. This flux is calculated to be orders of magnitude larger than the natural cosmic-ray background, and may constitute a serious hazard to aircraft electronic equipment. We present a series of numerical simulations supporting our conclusions. Our results suggest the necessity of dedicated measurement campaigns addressing the radiative and particle environment of aircraft near or within thunderstorms.

Tavani, M.; Argan, A.; Paccagnella, A.; Pesoli, A.; Palma, F.; Gerardin, S.; Bagatin, M.; Trois, A.; Picozza, P.; Benvenuti, P.; Flamini, E.; Marisaldi, M.; Pittori, C.; Giommi, P.

2013-04-01

48

Possible effects on avionics induced by Terrestrial Gamma-Ray Flashes  

NASA Astrophysics Data System (ADS)

We address the issue of the possible susceptibility of typical aircraft electronics exposed to particle, gamma-ray and neutron irradiation coming from Terrestrial Gamma-ray Flashes (TGF). We consider possible scenarios regarding the intensity, the duration, and geometry of TGFs influencing a nearby aircraft, and study their effects on electronic equipment. We calculate, for different assumptions, the total dose and the dose-rate, and estimate single-event effects. We find that in addition to the electromagnetic component (electrons/positrons, gamma-rays) also secondary neutrons produced by gamma-ray photoproduction in the aircraft structure substantially contribute to single-event effects in critical semiconductors components. Depending on the physical characteristics and geometry, TGFs may deliver a large flux of neutrons within a few milliseconds on an aircraft. This flux is calculated to be orders of magnitude larger than the natural cosmic-ray background, and may constitute a serious hazard to aircraft electronic equipment. We present a series of numerical simulations supporting our conclusions. Our results suggest the necessity of dedicated measurement campaigns addressing the radiative and particle environment of aircraft near or within thunderstorms.

Tavani, Marco; Argan, Andrea; Paccagnella, Alessandro; Pesoli, Alessandro; Palma, Francesco; Gerardin, Simone; Bagatin, Marta; Trois, Alessio; Picozza, Piergiorgio; Benvenuti, Piero; Flamini, Enrico; Marisaldi, Martino; Pittori, Carlotta; Giommi, Paolo

2013-04-01

49

Very-High-Energy Gamma-Ray Induced Pair Cascades in Blazars and Radio Galaxies  

NASA Astrophysics Data System (ADS)

Recent blazar detections by H.E.S.S., MAGIC, and VERITAS suggest that very-high-energy (VHE, E > 100 GeV) gamma-ray production may be common to most radio-loud Active Galactic Nuclei (AGN). We have investigated the signatures of Compton-supported pair cascades initiated by VHE gamma-ray absorption in arbitrary radiation fields, including monochromatic Ly-alpha line emission from the Broad Line Region and thermal infrared radiation from a circum-nuclear dust torus. We follow the spatial development of the cascade in full 3-dimensional geometry. We show that even for relatively weak magnetic fields, the cascades can be efficiently isotropized, leading to substantial off-axis cascade emission peaking in the Fermi energy range at detectable levels for nearby radio galaxies. We provide model fits to the gamma-ray loud radio galaxies NGC 1275 and Cen A, demonstrating that off-axis cascade emission may play an important role for the gamma-ray emission from radio galaxies observed by Fermi. This work was supported by NASA through Fermi Guest Investigator Grants NNX09AT81G and NNX10AO49G.

Roustazadeh, Parisa; Boettcher, M.

2011-01-01

50

PROTON INDUCED GAMMA-RAY ANALYSIS OF ATMOSPHERIC AEROSOLS FOR CARBON, NITROGEN, AND SULFUR COMPOSITION  

EPA Science Inventory

A technique for the simultaneous quantitative analysis of carbon, nitrogen, and sulfur using in-beam gamma-ray spectrometry has been developed for use with atmospheric aerosol samples. Samples are collected on quartz filters, and the aerosol composition is determined by analyzing...

51

Chemical warfare agent and high explosive identification by spectroscopy of neutron-induced gamma rays  

Microsoft Academic Search

A nondestructive assay method to identify chemical warfare (CW) agents and high explosive (HE) munitions was tested with actual chemical agents and explosives. The assay method exploits the gamma radiation produced by neutron interactions inside a container or munition to identify the elemental composition of its contents. The characteristic gamma-ray signature of the chemical elements chlorine, phosphorus, and sulfur were

A. J. Caffrey; J. D. Cole; R. J. Gehrke; R. C. Greenwood

1992-01-01

52

High energy irradiations simulating cosmic-ray-induced planetary gamma ray production. I - Fe target  

NASA Technical Reports Server (NTRS)

Two thick Fe targets were bombarded by a series of 6 GeV proton irradiations for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Gamma ray energy spectra were obtained with a germanium solid state detector during the bombardment, and 46 of the gamma ray lines were ascribed to the Fe targets. A comparison between observed and predicted values showed good agreement for Fe lines from neutron inelastic scattering and spallation reactions, and less satisfactory agreement for neutron capture reactions, the latter attributed to the difference in composition between the Fe target and the mean lunar abundance used in the modeling. Through an analysis of the irradiation results together with continuum data obtained in lunar orbit, it was found that 100 hours of measurement with a current instrument should generate a spectrum containing approximately 20 lines due to Fe alone, with a 2-sigma sensitivity for detection of about 0.2 percent.

Metzger, A. E.; Parker, R. H.; Yellin, J.

1986-01-01

53

Limits on thunderstorm-induced radioactive chlorine from gamma ray observations  

NASA Astrophysics Data System (ADS)

We present analysis of thunderstorm data collected with a liquid nitrogen-cooled germanium spectrometer with energies between 13 keV-2.6 MeV that was deployed at Langmuir Lab on South Baldy Peak in New Mexico for June through August 2005. The motivation was to search for gamma ray emissions from radioactive chlorine-39 and chlorine-38, as suggested by Greenfield et al. (2003). Based on the observations, we place an upper limit on the rate of chlorine production through such a process (6.8 10-17 chlorine atoms per argon atom). This rate is sufficiently low to suggest that the anomalous gamma ray count increases observed by Greenfield et al. (2003) were not caused by radioactive chlorine.

Lundberg, J. L.; Millan, R. M.; Eack, K.

2011-11-01

54

Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253  

SciTech Connect

Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via PcrPism??{sup 0}???. For a 'normal' star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a 'thick-target' model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

Wang, Xilu; Fields, Brian D. [Department of Astronomy, MC-221, 1002 W. Green Street, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

2014-05-09

55

Gamma ray astronomy  

Microsoft Academic Search

This paper summarizes recents results in gamma-ray astronomy, most of which were derived with data from groundbased gamma-ray detectors. Many of the contributions presented at this conference involve multiwavelength studies which combine ground-based gamma-ray measurements with optical data or space-based X-ray and gamma-ray measurements. Besides measurements of the diffuse emission from the Galaxy, observations of blazars, gamma-ray bursts, and supernova

Martin Pohl

2001-01-01

56

In vivo elemental analysis by counting neutron-induced gamma rays for medical and biological applications  

NASA Astrophysics Data System (ADS)

Non-invasive in vivo elemental analysis is a technique used to assess human body composition which is indicative of nutritional status and health condition. The in vivo measurement of the body's major elements is used for a variety of medical studies requiring the determination of the body's compartments (protein, fat, water, bone). Whole body gamma-ray counters, consisting of Nal(Tl) crystal detectors in a shielded room, are used for measuring in vivo the body's Ca, Cl, Na and P by delayed neutron activation analysis. Thermal neutrons from a moderated 238Pu-Be source are used for the measurement of total body nitrogen (and thus protein) and chlorine at low radiation exposure (0.80 mSv). The resulting high energy prompt gamma-rays from nitrogen (10.83 MeV) and chlorine (6.11 MeV) are detected simultaneously with the irradiation. Body fat (the main energy store) and fat distribution (which relates to risk for cardiovascular disease) are measured by detecting C and O in vivo through fast neutron inelastic scattering. A small sealed D-T neutron generator is used for the pulsed (4 - 8 KHz) production of fast neutrons. Carbon and oxygen are detected by counting the 4.44 and 6.13 MeV gamma-rays resulting from the inelastic scattering of the fast neutrons from the 12C and 16O nuclei, respectively. One use of this method is the systematic study of the mechanisms driving the age-associated depletion of the metabolizing, oxygen-consuming cellular compartment of the body. The understanding of this catabolism may suggest ways to maintain lean tissue and thus to preserve quality of life for the very old.

Kehayias, Joseph J.; Ma, Ruimei; Zhuang, Hong; Moore, Robert; Dowling, Lisa

1995-03-01

57

On-line coal analysis using fast neutron-induced gamma-rays.  

PubMed

On-line measurement of bulk elemental composition is often best achieved with highly penetrative neutron-gamma techniques. CSIRO has developed and implemented one such technique, neutron inelastic-scattering and thermal-capture analysis (NITA). A distinctive feature of NITA is its use of fast neutron sources to generate inelastic scattering reactions, thus exciting gamma-rays from industrially important elements such as carbon and oxygen. A full-scale prototype for on-line coal quality measurement has been tested under simulated industrial conditions. The effect of sample compositional inhomogeneity and stream thickness will be discussed. PMID:16026989

Lim, C S; Abernethy, D A

2005-01-01

58

Coincidence measurements between alpha particles and gamma rays in reactions induced by 85 and 155 MeV C on ??Sm  

E-print Network

COINCIDENCE MEASUREMENTS BETWEEN ALPHA PARTICLES AND GAMMA RAYS 12 154 IN REACTIONS INDUCED BY 85 AND 155 MEV C ON Sm A Thesis by STEVEN EDWARD CALA Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE August 1978 Major Subject: Chemistry COINCIDENCE MEASUREMENTS BETWEEN ALPHA PARTICLES AND GAMMA RAYS 12 154 IN REACTIONS INDUCED BY 85 AND 155 MEV C ON Sm A Thesis by STEVEN EDWARD CALA Approved...

Cala, Steven Edward

1978-01-01

59

GAMMA-RAY POLARIZATION INDUCED BY COLD ELECTRONS VIA COMPTON PROCESSES  

SciTech Connect

The polarization measurement is an important tool to probe the prompt emission mechanism in gamma-ray bursts (GRBs). The synchrotron photons can be scattered by cold electrons in the outflow via Compton scattering (CS) processes. The observed polarization depends on both the photon energy and the viewing angle. With the typical bulk Lorentz factor {Gamma} {approx} 200, photons with energy E > 10 MeV tend to have smaller polarization than photons with energy E < 1 MeV. At the right viewing angle, i.e., {theta} {approx} {Gamma}{sup -1}, the polarization achieves its maximal value, and the polarization angle changes 90 Degree-Sign relative to the initial polarization direction. Thus, the synchrotron radiation plus CS model can naturally explain the 90 Degree-Sign change of the polarization angle in GRB 100826A.

Chang Zhe; Jiang Yunguo; Lin Hainan, E-mail: changz@ihep.ac.cn, E-mail: jiangyg@ihep.ac.cn, E-mail: linhn@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China)

2013-05-20

60

Sex-dependent Differences in Intestinal Tumorigenesis Induced in Apc1638N/+ Mice by Exposure to {gamma} Rays  

SciTech Connect

Purpose: The purpose of the present study was to assess the effect of 1 and 5 Gy radiation doses and to investigate the interplay of gender and radiation with regard to intestinal tumorigenesis in an adenomatous polyposis coli (APC) mutant mouse model. Methods and Materials: Apc1638N/+ female and male mice were exposed whole body to either 1 Gy or 5 Gy of {gamma} rays and euthanized when most of the treated mice became moribund. Small and large intestines were processed to determine tumor burden, distribution, and grade. Expression of proliferation marker Ki-67 and estrogen receptor (ER)-{alpha} were also assessed by immunohistochemistry. Results: We observed that, with both 1 Gy and 5 Gy of {gamma} rays, females displayed reduced susceptibility to radiation-induced intestinal tumorigenesis compared with males. As for radiation effect on small intestinal tumor progression, although no substantial differences were found in the relative frequency and degree of dysplasia of adenomas in irradiated animals compared with controls, invasive carcinomas were found in 1-Gy- and 5-Gy-irradiated animals. Radiation exposure was also shown to induce an increase in protein levels of proliferation marker Ki-67 and sex-hormone receptor ER-{alpha} in both non tumor mucosa and intestinal tumors from irradiated male mice. Conclusions: We observed important sex-dependent differences in susceptibility to radiation-induced intestinal tumorigenesis in Apc1638N/+ mutants. Furthermore, our data provide evidence that exposure to radiation doses as low as 1 Gy can induce a significant increase in intestinal tumor multiplicity as well as enhance tumor progression in vivo.

Trani, Daniela [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Maastricht Radiation Oncology (MaastRO) Lab, GROW-School for Oncology and Developmental Biology, University of Maastricht (Netherlands); Moon, Bo-Hyun [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Kallakury, Bhaskar; Hartmann, Dan P. [Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States)] [Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Datta, Kamal [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Fornace, Albert J., E-mail: af294@georgetown.edu [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Center of Excellence in Genomic Medicine Research (CEGMR), King Abdulaziz University, Jeddah (Saudi Arabia)

2013-01-01

61

Accumulation and dissipation of positive charges induced on a PMMA build-up cap of an ionisation chamber by (60)Co gamma-ray irradiation.  

PubMed

The signal current from an ionisation chamber with a PMMA build-up cap decreases with irradiation time due to electric fields produced by positive charges induced on the cap. In the present study, it was confirmed that the signal current decreases faster for irradiation using narrower (60)Co gamma-ray beams. This is because the number of secondary electrons that are emitted from surrounding materials and penetrate the build-up cap is smaller in a narrower gamma-ray beam, so that fewer positive charges are neutralised. The ionisation chamber was first subjected to continuous gamma-ray irradiation for 24 h, following which it was irradiated with shorter periodic gamma-ray bursts while measuring the current signal. This allowed the coefficients of positive charge accumulation and dissipation to be determined. It was found that the dissipation coefficient has a large constant value during gamma-ray irradiation and decreases asymptotically to a small value after irradiation is stopped. From the coefficients, the minimum signal current was calculated, which is the value when accumulation and dissipation balance each other under continuous irradiation. The time required for the signal current to recover following irradiation was also calculated. PMID:23390147

Morishita, Y; Takata, N

2013-07-01

62

Induced Mutations for Improving Production on Bread and Durum Wheat  

NASA Astrophysics Data System (ADS)

Wheat is a very important crop and has been bred for food and its improvement is continuous from cross-breeding. Radiation and chemically induced mutations have provided variability in selection for novel varieties. Four bread and one durum wheat cultivars were exposed to gamma rays, Cs 137 with doses 10, 15 and 20 krad (2000 seeds of each dose and cultivars). We have isolated mutant plants with height reduced and on cv Progress spike without chaff.

Stamo, Ilirjana; Ylli, Ariana; Dodbiba, Andon

2007-04-01

63

Induced Mutations for Improving Production on Bread and Durum Wheat  

SciTech Connect

Wheat is a very important crop and has been bred for food and its improvement is continuous from cross-breeding. Radiation and chemically induced mutations have provided variability in selection for novel varieties. Four bread and one durum wheat cultivars were exposed to gamma rays, Cs 137 with doses 10, 15 and 20 krad (2000 seeds of each dose and cultivars). We have isolated mutant plants with height reduced and on cv Progress spike without chaff.

Stamo, Ilirjana; Ylli, Ariana; Dodbiba, Andon [Institute of Biological Research, Academy of Sciences, Rruga Sami Frasheri 5, Tirana (Albania); Institute of Nuclear Physics, Academy of Sciences, P.O. Box 85 Tirana (Albania)

2007-04-23

64

Body composition to climate change studies - the many facets of neutron induced prompt gamma-ray analysis  

SciTech Connect

In-vivo body composition analysis of humans and animals and in-situ analysis of soil using fast neutron inelastic scattering and thermal neutron capture induced prompt-gamma rays have been described. By measuring carbon (C), nitrogen (N) and oxygen (O), protein, fat and water are determined. C determination in soil has become important for understanding below ground carbon sequestration process in the light of climate change studies. Various neutron sources ranging from radio isotopic to compact 14 MeV neutron generators employing the associated particle neutron time-of-flight technique or micro-second pulsing were implemented. Gamma spectroscopy using recently developed digital multi-channel analyzers has also been described.

Mitra,S.

2008-11-17

65

Gamma-ray waveguides  

SciTech Connect

We have developed an approach for gamma-ray optics using layered structures acting as planar waveguides. Experiments demonstrating channeling of 122 keV gamma rays in two prototype waveguides validate the feasibility of this technology. Gamma-ray waveguides allow one to control the direction of radiation up to a few MeV. The waveguides are conceptually similar to polycapillary optics, but can function at higher gamma-ray energies. Optics comprised of these waveguides will be able to collect radiation from small solid angles or concentrate radiation into small area detectors. Gamma-ray waveguides may find applications in medical imaging and treatment, astrophysics, and homeland security.

Tournear, D. M.; Hoffbauer, M. A.; Akhadov, E. A.; Chen, A. T.; Pendleton, S. J.; Williamson, T. L.; Cha, K. C.; Epstein, R. I. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2008-04-14

66

Gamma-ray astronomy  

E-print Network

This paper summarizes recents results in gamma-ray astronomy, most of which were derived with data from ground-based gamma-ray detectors. Many of the contributions presented at this conference involve multiwavelength studies which combine ground-based gamma-ray measurements with optical data or space-based X-ray and gamma-ray measurements. Besides measurements of the diffuse emission from the Galaxy, observations of blazars, gamma-ray bursts, and supernova remnants this paper also covers theoretical models for the acceleration of radiating particles and their emission mechanisms in these sources.

Martin Pohl

2001-11-29

67

Neutron-induced gamma-ray production cross sections for the first excited-state transitions in Ne-20 and Ne-22  

E-print Network

Background: Neutron-induced reactions are a significant concern for experiments that require extremely low levels of radioactive backgrounds. Measurements of gamma-ray production cross sections over a wide energy range will help to predict and identify neutron backgrounds in these experiments. Purpose: Determine partial gamma-ray production cross sections for neutron-induced reactions in natural neon. Methods: The broad-spectrum neutron beam at the Los Alamos Neutron Science Center (LANSCE) was used for the measurement. Gamma rays from neutron-induced reactions were detected using the GErmanium Array for Neutron Induced Excitations (GEANIE). Results: Partial gamma-ray cross sections were measured for the first excited-state transitions in Ne-20 and Ne-22. The measured cross sections were compared to the TALYS and CoH3 nuclear reaction codes. Conclusions: These are the first experimental data for (n,n') reactions in neon. In addition to providing data to aid in the prediction and identification of neutron backgrounds in low-background experiments, these new measurements will help refine cross-section predictions in a mass region where models are not well constrained.

S. MacMullin; M. Boswell; M. Devlin; S. R. Elliott; N. Fotiades; V. E. Guiseppe; R. Henning; T. Kawano; B. H. LaRoque; R. O. Nelson; J. M. O'Donnell

2012-10-03

68

Assessment of gamma ray-induced DNA damage in Lasioderma serricorne using the comet assay  

NASA Astrophysics Data System (ADS)

We attempted a DNA comet assay under alkaline conditions to verify the irradiation treatment of pests. Lasioderma serricorne (Fabricius) were chosen as test insects and irradiated with gamma rays from a 60Co source at 1 kGy. We conducted the comet assay immediately after irradiation and over time for 7 day. Severe DNA fragmentation in L. serricorne cells was observed just after irradiation and the damage was repaired during the post-irradiation period in a time-dependent manner. The parameters of the comet image analysis were calculated, and the degree of DNA damage and repair were evaluated. Values for the Ratio (a percentage determined by fluorescence in the damaged area to overall luminance, including intact DNA and the damaged area of a comet image) of individual cells showed that no cells in the irradiated group were included in the Ratio<0.1 category, the lowest grade. This finding was observed consistently throughout the 7-day post-irradiation period. We suggest that the Ratio values of individual cells can be used as an index of irradiation history and conclude that the DNA comet assay under alkaline conditions, combined with comet image analysis, can be used to identify irradiation history.

Kameya, Hiromi; Miyanoshita, Akihiro; Imamura, Taro; Todoriki, Setsuko

2012-03-01

69

Molecular characterization of mutations induced by gamma irradiation in rice.  

PubMed

In order to analyze mutations induced by gamma irradiation in higher plants, we irradiated rice with gamma rays and screened for mutations expressing phenotypes of glutinous endosperm (wx), chlorophyll b deficiency, endosperm protein deficiency, gibberellin-related dwarfism, and shortened plastochron-in order to clarify types of mutations. Nucleotide sequence analysis showed that the most frequent mutation induced by gamma rays was deletion, particularly small deletion. Of the 24 mutations, 15 were small deletions (1-16 bp), four were large deletions (9.4-129.7 kbp), three were single-base substitutions, and two were inversions. Deletions 100 bp-8 kbp in length were not found, suggesting that gamma irradiation is unlikely to induce deletions of 100 bp to 8 kbp but is more likely to induce deletions between 1 and several ten bp or those of around 10 kbp or more. Based on the results, reverse genetics applications may be possible for gamma irradiation-induced deletions in rice by mismatch cleavage analysis used in Targeting Induced Local Lesions IN Genomes (TILLING) to detect small deletions and base substitutions or by using array comparative genomic hybridization (aCGH) to detect large deletions. PMID:20154423

Morita, Ryouhei; Kusaba, Makoto; Iida, Shuichi; Yamaguchi, Hiroyasu; Nishio, Takeshi; Nishimura, Minoru

2009-10-01

70

Gamma ray-induced synthesis of hyaluronic acid/chondroitin sulfate-based hydrogels for biomedical applications  

NASA Astrophysics Data System (ADS)

Hyaluronic acid (HA)/chondroitin sulfate (CS)/poly(acrylic acid) (PAAc) hydrogel systems were synthesized by gamma-ray irradiation without the use of additional initiators or crosslinking agents to achieve a biocompatible hydrogel system for skin tissue engineering. HA and CS derivatives with polymerizable residues were synthesized. Then, the hydrogels composed of glycosaminoglycans, HA, CS, and a synthetic ionic polymer, PAAc, were prepared using gamma-ray irradiation through simultaneous free radical copolymerization and crosslinking. The physicochemical properties of the HA/CS/PAAc hydrogels having various compositions were investigated to evaluate their feasibility as artificial skin substitutes. The gel fractions of the HA/CS/PAAc hydrogels increased in absorbed doses up to 15 kGy, and they exhibited 91-93% gel fractions under 15 kGy radiation. All of the HA/CS/PAAc hydrogels exhibited relatively high water contents of over 90% and reached an equilibrium swelling state within 24 h. The enzymatic degradation kinetics of the HA/CS/PAAc hydrogels depended on both the concentration of the hyaluronidase solution and the ratio of HA/CS/PAAc. The in vitro drug release profiles of the HA/CS/PAAc hydrogels were significantly influenced by the interaction between the ionic groups in the hydrogels and the ionic drug molecules as well as the swelling of the hydrogels. From the cytotoxicity results of human keratinocyte (HaCaT) cells cultured with extracts of the HA/CS/PAAc hydrogels, all of the HA/CS/PAAc hydrogel samples tested showed relatively high cell viabilities of more than 82%, and did not induce any significant adverse effects on cell viability.

Zhao, Linlin; Gwon, Hui-Jeong; Lim, Youn-Mook; Nho, Young-Chang; Kim, So Yeon

2015-01-01

71

Gamma ray transients  

NASA Technical Reports Server (NTRS)

The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

Cline, Thomas L.

1987-01-01

72

Gamma Ray Bursts Sudden, intense flashes of gamma rays  

E-print Network

Gamma Ray Bursts #12;The Case Sudden, intense flashes of gamma rays come from nowhere and disappear with out a trace. Incredibly powerful: A single gamma ray burst is hundreds of times brighter a supernova #12;Who Vela (1960's) Looking for arms testing, found gamma ray bursts Compton Gamma Ray Observatory

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

73

Gamma rays induce DNA damage and oxidative stress associated with impaired growth and reproduction in the copepod Tigriopus japonicus.  

PubMed

Nuclear radioisotope accidents are potentially ecologically devastating due to their impact on marine organisms. To examine the effects of exposure of a marine organism to radioisotopes, we irradiated the intertidal copepod Tigriopus japonicus with several doses of gamma radiation and analyzed the effects on mortality, fecundity, and molting by assessing antioxidant enzyme activities and gene expression patterns. No mortality was observed at 96h, even in response to exposure to a high dose (800Gy) of radiation, but mortality rate was significantly increased 120h (5 days) after exposure to 600 or 800Gy gamma ray radiation. We observed a dose-dependent reduction in fecundity of ovigerous females; even the group irradiated with 50Gy showed a significant reduction in fecundity, suggesting that gamma rays are likely to have a population level effect. In addition, we observed growth retardation, particularly at the nauplius stage, in individuals after gamma irradiation. In fact, nauplii irradiated with more than 200Gy, though able to molt to copepodite stage 1, did not develop into adults. Upon gamma radiation, T. japonicus showed a dose-dependent increase in reactive oxygen species (ROS) levels, the activities of several antioxidant enzymes, and expression of double-stranded DNA break damage genes (e.g. DNA-PK, Ku70, Ku80). At a low level (sub-lethal dose) of gamma irradiation, we found dose-dependent upregulation of p53, implying cellular damage in T. japonicus in response to sub-lethal doses of gamma irradiation, suggesting that T. japonicus is not susceptible to sub-lethal doses of gamma irradiation. Additionally, antioxidant genes, phase II enzyme (e.g. GSTs), and cellular chaperone genes (e.g. Hsps) that are involved in cellular defense mechanisms also showed the same expression patterns for sublethal doses of gamma irradiation (50-200Gy). These findings indicate that sublethal doses of gamma radiation can induce oxidative stress-mediated DNA damage and increase the expression of antioxidant enzymes and proteins with chaperone-related functions, thereby significantly affecting life history parameters such as fecundity and molting in the copepod T. japonicus. PMID:24800869

Han, Jeonghoon; Won, Eun-Ji; Lee, Bo-Young; Hwang, Un-Ki; Kim, Il-Chan; Yim, Joung Han; Leung, Kenneth Mei Yee; Lee, Yong Sung; Lee, Jae-Seong

2014-07-01

74

Gamma-ray astrophysics  

NASA Technical Reports Server (NTRS)

Conference papers on gamma ray astrophysics are summarized. Data cover the energy region from about 0.3 MeV to a few hundred GeV and theoretical models of production mechanisms that give rise to both galactic and extragalactic gamma rays.

Stecker, F. W. (editor); Trombka, J. I. (editor)

1973-01-01

75

Gamma-Ray Pulsars  

NASA Technical Reports Server (NTRS)

The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the detection of over 80 gamma-ray pulsars. Several new populations have been discovered, including 24 radio quiet pulsars found through gamma-ray pulsations alone and about 20 millisecond gamma-ray pulsars. The gamma-ray pulsations from millisecond pulsars were discovered by both folding at periods of known radio millisecond pulsars or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -35 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. The higher sensitivity and larger energy range of the Fermi Large Area Telescope has produced detailed energy-dependent light curves and phase-resolved spectroscopy on brighter pulsars, that have ruled out polar cap models as the major source of the emission in favor of outer magnetosphere accelerators. The large number of gamma-ray pulsars now allows for the first time meaningful population and sub-population studies that are revealing surprising properties of these fascinating sources.

Harding, Alice K.

2011-01-01

76

Gamma ray detector shield  

DOEpatents

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26

77

Gamma ray detector shield  

Microsoft Academic Search

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

R. D. Ohlinger; H. W. Humphrey

1985-01-01

78

Gamma-ray astronomy  

Microsoft Academic Search

A brief description is given of the present status of gamma-ray astronomy, both galactic and extragalactic. More detailed attention is given to a specific question: the nature of the apparent 'gamma-ray sources'. The undoubted correlation of at least some of the sources with dense clouds of gas in the interstellar medium is discussed. A new analysis of the SAS II

B. Houston; A. W. Wolfendale

1982-01-01

79

Gamma ray astronomy. [survey  

NASA Technical Reports Server (NTRS)

A survey of the instruments developed for gamma ray astronomy is given together with a brief summary of the current status of the observational results. These include the studies of galactic gamma ray emission, the diffuse, presumably extragalactic, gamma radiation, and localized gamma ray sources. The study of the spatial distribution of galactic gamma radiation is beginning to provide a new means for the study of galactic structure and dynamics. The diffuse emission may provide evidence of gamma ray emission in the cosmological past, although improved observations must be obtained before the picture can be clarified. The study of localized sources has shown NP0532, the Crab radio pulsar, to be a gamma ray pulsar also and strong emission from Vela may be due to supernova produced cosmic rays interacting with the remnant gas.

Kniffen, D.

1975-01-01

80

mBAND Analysis of Late Chromosome Aberrations in Human Lymphocytes Induced by Gamma Rays and Fe Ions  

NASA Technical Reports Server (NTRS)

Chromosomal translocations and inversions are considered stable, and cells containing these types of chromosome aberrations can survive multiple cell divisions. An efficient method to detect an inversion is multi-color banding fluorescent in situ hybridization (mBAND) which allows identification of both inter- and intrachromosome aberrations simultaneously. Post irradiation, chromosome aberrations may also arise after multiple cell divisions as a result of genomic instability. To investigate the stable or late-arising chromosome aberrations induced after radiation exposure, we exposed human lymphocytes to gamma rays and Fe ions ex vivo, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis and at several time intervals during the culture period post irradiation. With gamma irradiation, about half of the damages observed at first mitosis remained after 7 day- and 14 day- culture, suggesting the transmissibility of damages to the surviving progeny. Detailed analysis of chromosome break ends participating in exchanges revealed a greater fraction of break ends involved in intrachromosome aberrations in the 7- and 14-day samples in comparison to the fraction at first mitosis. In particular, simple inversions were found at 7 and 14 days, but not at the first mitosis, suggesting that some of the aberrations might be formed days post irradiation. In contrast, at the doses that produced similar frequencies of gamma-induced chromosome aberrations as observed at first mitosis, a significantly lower yield of aberrations remained at the same population doublings after Fe ion exposure. At these equitoxic doses, more complex type aberrations were observed for Fe ions, indicating that Fe ion-induced initial chromosome damages are more severe and may lead to cell death. Comparison between low and high doses of Fe ion irradiation in the induction of late damages will also be discussed.

Sunagawa, Mayumi; Zhang, Ye; Yeshitla, Samrawit; Kadhim, Munira; Wilson, Bobby; Wu, Honglu

2014-01-01

81

Hyperthermia increases gamma-ray and fission neutron-induced translocations in Drosophila  

SciTech Connect

Hyperthermia has been reported in Drosophila melanogaster to increase radiation-induced chromosome rearrangements, chromosome loss, recessive and dominant lethals. To determine whether hyperthermia would also affect high linear energy transfer (LET)-induced genetic damage such as translocations, which involve breakage and reunion of chromosomes, a genetic system was employed not only allowing detection of ordinary 2;3 translocations, but also permitting a more accurate measure of Y-autosome translocations.

Mittler, S.

1984-01-01

82

A study of gamma-ray and beta-particle decay heat following thermal neutron induced fission of {sup 235}U  

SciTech Connect

Aggregate gamma-ray and aggregate beta-particle energy spectra have been measured for fission products resulting from thermal neutron-induced fission of {sup 235}U for decay times ranging from approximately 0.2s to 12,000s after fission. Preliminary energy distributions have been deduced from the measurements and these have been compared with summation calculations performed with CINDER using the ENDF/B-VI fission product data base.

Couchell, G.P.; Campbell, J.M.; Li, Shengjie; Nguyen, H.V.; Pullen, D.J.; Schier, W.A.; Seabury, E.H.; Tipnis, S.V. [Univ. of Massachusetts, Lowell, MA (United States); England, T.R. [Los Alamos National Lab., NM (United States)

1994-12-31

83

Does merger-induced core-collapse produce gamma-ray bursts in type Ib & Ic supernovae?  

E-print Network

Gamma-ray bursts, discovered over three decades ago, can appear to be a hundred times as luminous as the brightest supernovae. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of type Ib and Ic. Here we interpret the overabundance of millisecond pulsars in globular clusters and the details of supernova 1987A to reveal the energy source, which powers at least some long-duration gamma-ray bursts, as core-collapse following the merger of two white dwarfs, either as stars or stellar cores. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core-collapse, or the beams/jets themselves must clear their own path. The core-collapse produces supernovae of type Ib, Ic, or II (as with SN1987A, a SNa IIp), leaving a weakly magnetized neutron star remnant with a spin period near 2 milliseconds. There is no compelling reason to invoke any other model for gamma-ray bursts.

John Middleditch

2003-11-12

84

Sucrose delays membrane deterioration of chrysanthemum flowers induced by gamma-rays  

NASA Astrophysics Data System (ADS)

Fluidity of the flower membranes of cut chrysanthemums ( Dendranthema grandiflorum Kitamura) decreased soon after gamma-irradiation at 750Gy and continued to decrease during storage following irradiation. Holding chrysanthemum cut inflorescence in 2% sucrose suppressed the decrease. The results suggest that sugars reduce radiation-induced physiological deterioration of chrysanthemum flower membranes.

Kikuchi, O. K.; Todoriki, S.; Hayashi, T.

1998-06-01

85

Neutron induced prompt gamma-ray and instrumental neutron activation analyses of urban estuarine sediments  

Microsoft Academic Search

Neutron induced prompt -ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Tama River estuary in Tokyo, Japan. The vertical distribution of 24 elements in the sediments was determined and the factors goveming the vertical profiles have been discussed. Major elements are distributed depending on weathering that proceeds much with increasing

A. Kuno; M. Matsuo; B. Takano; C. Yonezawa; H. Matsue; H. Sawahata

1997-01-01

86

Prompt gamma rays from triton-induced reactions on oxygen and their use for analysis  

Microsoft Academic Search

Triton-induced reactions on oxygen were studied with a view to using the prompt ?-rays for analytical purposes. Five ?-rays\\u000a were found to be potentially useful, of which three had a high intensity, the n(1, 0), n(2, 0) and p(1, 0) ?-rays, the other\\u000a two being the n(3, 0) and the unresolved pair ?(1, 0)?(2, 0). The ?-rays are labelled according

M. Peisach

1972-01-01

87

Induced mutations in rice  

Technology Transfer Automated Retrieval System (TEKTRAN)

Induced mutations have a long history in both applied and basic aspects of rice research. During the past fifty years, over 500 rice varieties have been developed worldwide, either directly from induced mutants or as a result of crossing such mutants with other breeding lines. More recently, the gen...

88

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts originate from cosmological distances and represent the largest known explosions in the Universe. The observed temporal and spectral characteristics of bursts in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory, will be described. The talk will concentrate on recent studies of burst properties, correlations of GRB parameters and other statistical studies that have recently come to light. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various models for the energy source of gamma-ray bursts will be described.

Fishman, Gearld J.

2003-01-01

89

Gamma-ray Astronomy  

E-print Network

The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

Jim Hinton

2007-12-20

90

Gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

Cosmic gamma rays, the physical processes responsible for their production and the astrophysical sites from which they were seen are reported. The bulk of the observed gamma ray emission is in the photon energy range from about 0.1 MeV to 1 GeV, where observations are carried out above the atmosphere. There are also, however, gamma ray observations at higher energies obtained by detecting the Cerenkov light produced by the high energy photons in the atmosphere. Gamma ray emission was observed from sources as close as the Sun and the Moon and as distant as the quasar 3C273, as well as from various other galactic and extragalactic sites. The radiation processes also range from the well understood, e.g. energetic particle interactions with matter, to the still incompletely researched, such as radiation transfer in optically thick electron positron plasmas in intense neutron star magnetic fields.

Ramaty, R.; Lingenfelter, R. E.

1982-01-01

91

High Energy Gamma Rays  

E-print Network

This article reviews the present status of high energy gamma-ray astronomy at energies above 30 MeV. Observations in the past decade using both space- and ground-based experiments have been primarily responsible for giving a tremendous boost to our knowledge of the high energy Universe. High energy gamma-rays have been detected from a wide range of Galactic and extragalactic astrophysical sources, such as gamma-ray bursters, pulsars, and active galaxies. These observations have established high energy gamma-ray astronomy as a vital and exciting field, that has a bright future. This review summarizes the experimental techniques, observations and results obtained with recent experiments, and concludes with a short description of future prospects.

R. Mukherjee

2000-09-22

92

Gamma ray line astronomy  

NASA Technical Reports Server (NTRS)

The interpretations and implications of the astrophysical observations of gamma-ray lines are reviewed. At the Galactic Center e(+)-e(-) pairs from a compact object produce an annihilation line that shows no redshift, indicating an annihilation site far removed from this object. In the jets of SS433, gamma-ray lines are produced by inelastic excitations, probably in dust grains, although line emission from fusion reactions has also been considered. Observations of diffuse galactic line emission reveal recently synthesized radioactive aluminum in the interstellar medium. In gamma-ray bursts, redshifted pair annihilation lines are consistent with a neutron star origin for the bursts. In solar flares, gamma-ray line emission reveals the prompt acceleration of protons and nuclei, in close association with the flare energy release mechanism.

Ramaty, R.

1984-01-01

93

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Miscellaneous tasks related to the development of the Bursts and Transient Source Experiment on the Gamma Ray Observatory and to analysis of archival data from balloon flight experiments were performed. The results are summarized and relevant references are included.

Paciesas, William S.

1991-01-01

94

Gamma ray optics  

SciTech Connect

Via refractive or diffractive scattering one can shape {gamma} ray beams in terms of beam divergence, spot size and monochromaticity. These concepts might be particular important in combination with future highly brilliant gamma ray sources and might push the sensibility of planned experiments by several orders of magnitude. We will demonstrate the experimental feasibility of gamma ray monochromatization on a ppm level and the creation of a gamma ray beam with nanoradian divergence. The results are obtained using the inpile target position of the High Flux Reactor of the ILL Grenoble and the crystal spectrometer GAMS. Since the refractive index is believed to vanish to zero with 1/E{sup 2}, the concept of refractive optics has never been considered for gamma rays. The combination of refractive optics with monochromator crystals is proposed to be a promising design. Using the crystal spectrometer GAMS, we have measured for the first time the refractive index at energies in the energy range of 180 - 2000 keV. The results indicate a deviation from simple 1/E{sup 2} extrapolation of X-ray results towards higher energies. A first interpretation of these new results will be presented. We will discuss the consequences of these results on the construction of refractive optics such as lenses or refracting prisms for gamma rays and their combination with single crystal monochromators.

Jentschel, M.; Guenther, M. M.; Habs, D.; Thirolf, P. G. [Institut Laue-Langevin, F38042 Grenoble (France); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching, Germany and Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany)

2012-07-09

95

The gamma-ray observatory  

NASA Technical Reports Server (NTRS)

An overview is given of the Gamma Ray Observatory (GRO) mission. Detection of gamma rays and gamma ray sources, operations using the Space Shuttle, and instruments aboard the GRO, including the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET) are among the topics surveyed.

1991-01-01

96

Prospects for gamma ray astronomy  

NASA Technical Reports Server (NTRS)

The Solar Maximum Mission and the Gamma Ray Experiment aboard the SMM spacecraft are discussed. Mission plans for interplanetary probes are also discussed. The Gamma Ray observatory and its role in future gamma ray astronomy is highlighted. It is concluded that gamma ray astronomy will be of major importance in the development of astronomical models and in the development of comsological theory.

1981-01-01

97

gamma ray astronomy with muons  

Microsoft Academic Search

Although gamma ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative ``enhancement'' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the

Francis Halzen; Todor Stanev; Gaurang B. Yodh

1997-01-01

98

Gamma Ray Bursts from Ordinary Cosmic Strings  

E-print Network

We give an upper estimate for the number of gamma ray bursts from ordinary (non-superconducting) cosmic strings expected to be observed at terrestrial detectors. Assuming that cusp annihilation is the mechanism responsible for the bursts we consider strings arising at a GUT phase transition and compare our estimate with the recent BATSE results. Further we give a lower limit for the effective area of future detectors designed to detect the cosmic string induced flux of gamma ray bursts.

R. H. Brandenberger; A. T. Sornborger; M. Trodden

1993-02-12

99

Simultaneous determination of Si, Al and Na concentrations by particle induced gamma-ray emission and applications to reference materials and ceramic archaeological artifacts  

NASA Astrophysics Data System (ADS)

A particle induced gamma ray emission (PIGE) method using 4 MeV proton beam was standardized for simultaneous determination of Si, Al and Na concentrations and has been applied for non-destructive analysis of several reference materials and archaeological clay pottery samples. Current normalized count rates of gamma-rays for the three elements listed above were obtained by an in situ method using Li as internal standard. The paper presents application of the in situ current normalized PIGE method for grouping study of 39 clay potteries, obtained from Rajasthan and Andhra Pradesh states of India. Grouping of artifacts was carried out using the ratios of SiO2 to Al2O3 concentrations, due to their non volatile nature. Powder samples and elemental standards in pellet forms (cellulose matrix) were irradiated using the 4 MeV proton beam (?10 nA) from the 3 MV tandem accelerator at IOP Bhubaneswar, and assay of prompt gamma rays was carried out using a 60% relative efficiency HPGe detector coupled to MCA. The concentration ratio values of SiO2/Al2O3 indicated that pottery samples fell into two major groups, which are in good agreement with their collection areas. Reference materials from IAEA and NIST were analyzed for quantification of Si, Al and Na concentrations as a part of validation as well as application of PIGE method.

Dasari, K. B.; Chhillar, S.; Acharya, R.; Ray, D. K.; Behera, A.; Lakshmana Das, N.; Pujari, P. K.

2014-11-01

100

Gamma ray optics  

NASA Astrophysics Data System (ADS)

Via refractive or diffractive scattering one can shape ? ray beams in terms of beam divergence, spot size and monochromaticity. These concepts might be particular important in combination with future highly brilliant gamma ray sources and might push the sensibility of planned experiments by several orders of magnitude. We will demonstrate the experimental feasibility of gamma ray monochromatization on a ppm level and the creation of a gamma ray beam with nanoradian divergence. The results are obtained using the inpile target position of the High Flux Reactor of the ILL Grenoble and the crystal spectrometer GAMS. Since the refractive index is believed to vanish to zero with 1/E2, the concept of refractive optics has never been considered for gamma rays. The combination of refractive optics with monochromator crystals is proposed to be a promising design. Using the crystal spectrometer GAMS, we have measured for the first time the refractive index at energies in the energy range of 180 - 2000 keV. The results indicate a deviation from simple 1/E2 extrapolation of X-ray results towards higher energies. A first interpretation of these new results will be presented. We will discuss the consequences of these results on the construction of refractive optics such as lenses or refracting prisms for gamma rays and their combination with single crystal monochromators.

Jentschel, M.; Gnther, M. M.; Habs, D.; Thirolf, P. G.

2012-07-01

101

Gamma ray camera  

DOEpatents

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array. 6 figs.

Perez-Mendez, V.

1997-01-21

102

Gamma ray camera  

DOEpatents

A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array.

Perez-Mendez, Victor (Berkeley, CA)

1997-01-01

103

Techniques for gamma rays.  

NASA Technical Reports Server (NTRS)

The detecting systems used in high energy astrophysics are generally more similar to particle detectors than to optical devices. The basic design of the gamma ray instrument depends on whether the energy range is below about 10 MeV and therefore in the region where the Compton effect predominates in the absorption of the gamma-rays, or above that energy where electron-positron pair production is most important. The most usual approach to the detector system in the lower of the two energy intervals is to use a scintillation counter in the center of the detector system to absorb the photons and permit a measure of their energy, and to surround it by another detector which is employed as an active anticoincidence shield to discriminate against charged particles. In the gamma-ray interval above about 10 MeV, the very low flux of gamma rays and the high particle background has directed the development of high energy gamma-ray telescopes towards complicated techniques and large detector arrays. As a result, several investigators have now turned to the spark chamber as the heart of a detector system. Generally, it is surrounded by an anticoincidence system and is triggered by a counter telescope.

Fichtel, C. E.

1971-01-01

104

Inelastic cross sections from gamma-ray measurements  

SciTech Connect

Measurements of gamma rays following neutron induced reactions have been studied with the Germanium Array for Neutron-induced Excitations (GEANIE) at the Los Alamos Neutron Science Center (LANSCE) for many years. Gamma-ray excitation functions and coincidence studies provide insight into nuclear reaction mechanisms as well as expanding our knowledge of energy levels and gamma-rays. Samples studied with Ge detectors at LANSCE range from Be to Pu. Fe, Cr and Ti have been considered for use as reference cross sections. An overview of the measurements and efforts to create a reliable neutron-induced gamma-ray reference cross section will be presented.

Nelson, Ronald Owen [Los Alamos National Laboratory

2010-12-06

105

Evaluation of distant carbon sources in biosurfactant production by a gamma ray-induced Pseudomonas putida mutant  

Microsoft Academic Search

Pseudomonas putida 33 wild strain, subjected to gamma ray mutagenesis and designated as P. putida 300-B mutant was used as microbial rhamnolipid-producer by using distant carbon sources (viz. hydrocarbons, waste frying oils WFOs, vegetable oil refinery wastes and molasses) in the minimal media under shake flask conditions. The behavior of glucose as co-substrate and growth initiator was examined. The 300-B

Zulfiqar Ali Raza; Muhammad Saleem Khan; Zafar M. Khalid

2007-01-01

106

Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber  

PubMed Central

In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%. PMID:24755521

Jang, Kyoung Won; Shin, Sang Hun; Kim, Seon Geun; Kim, Jae Seok; Yoo, Wook Jae; Ji, Young Hoon; Lee, Bongsoo

2014-01-01

107

Gamma-ray bursts.  

PubMed

Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow. PMID:22923573

Gehrels, Neil; Mszros, Pter

2012-08-24

108

Gamma Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day ,last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

Gehrels, Neil; Meszaros, Peter

2012-01-01

109

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

A review is given of recent papers in the field of gamma-ray astronomy. It is mentioned that the strongest feature of the gamma ray sky is the general radiation from the galactic plane which is superimposed on what appears to be a general diffuse radiation, whose properties are not yet defined. The observation of high-energy galactic gamma radiation by the SAS-2 satellite is considered as is the observation of point and localized sources (the Crab Nebula, Vela, etc.). The observation of diffusive gamma radiation is discussed.

Fichtel, C. E.

1975-01-01

110

The involvement of hypoxia-inducible factor-1alpha in the susceptibility to gamma-rays and chemotherapeutic drugs of oral squamous cell carcinoma cells.  

PubMed

The transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha) is the key regulator that controls the hypoxic response of mammalian cells. The overexpression of HIF-1alpha has been demonstrated in many human tumors. However, the role of HIF-1alpha in the therapeutic efficacy of chemotherapy and radiotherapy in cancer cells is poorly understood. In this study, we investigated the influence of HIF-1alpha expression on the susceptibility of oral squamous cell carcinoma (OSCC) cells to chemotherapeutic drugs (cis-diamminedichloroplatinum and 5-fluorouracil) and gamma-rays. Treatment with chemotherapeutic drugs and gamma-rays enhanced the expression and nuclear translocation of HIF-1alpha, and the susceptibility of OSCC cells to the drugs and gamma-rays was negatively correlated with the expression level of HIF-1alpha protein. The overexpression of HIF-1alpha induced OSCC cells to become more resistant to the anticancer agents, and down-regulation of HIF-1alpha expression by small interfering RNA enhanced the susceptibility of OSCC cells to them. In the HIF-1alpha-knockdown OSCC cells, the expression of P-glycoprotein, heme oxygenase-1, manganese-superoxide dismutase and ceruloplasmin were downregulated and the intracellular levels of chemotherapeutic drugs and reactive oxygen species were sustained at higher levels after the treatment with the anticancer agents. These results suggest that enhanced HIF-1alpha expression is related to the resistance of tumor cells to chemo- and radio-therapy and that HIF-1alpha is an effective therapeutic target for cancer treatment. PMID:17066447

Sasabe, Eri; Zhou, Xuan; Li, Dechao; Oku, Naohisa; Yamamoto, Tetsuya; Osaki, Tokio

2007-01-15

111

Gamma Ray Bursts  

E-print Network

Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed to explain them, with a view towards implications for C.T.A.

Peter Mszros

2012-04-12

112

Gamma-ray bursts  

Microsoft Academic Search

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models

P. Mszros

2006-01-01

113

Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

The project has progressed successfully during this period of performance. The highlights of the Gamma Ray Astronomy teams efforts are: (1) Support daily BATSE data operations, including receipt, archival and dissemination of data, quick-look science analysis, rapid gamma-ray burst and transient monitoring and response efforts, instrument state-of-health monitoring, and instrument commanding and configuration; (2) On-going scientific analysis, including production and maintenance of gamma-ray burst, pulsed source and occultation source catalogs, gamma-ray burst spectroscopy, studies of the properties of pulsars and black holes, and long-term monitoring of hard x-ray sources; (3) Maintenance and continuous improvement of BATSE instrument response and calibration data bases; (4) Investigation of the use of solid state detectors for eventual application and instrument to perform all sky monitoring of X-Ray and Gamma sources with high sensitivity; and (5) Support of BATSE outreach activities, including seminars, colloquia and World Wide Web pages. The highlights of this efforts can be summarized in the publications and presentation list.

Wu, S. T.

2000-01-01

114

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Miscellaneous tasks related to the development of the Burst and Transient Source Experiment on the Gamma Ray Observatory and to collection, analysis, and interpretation of data from the MSFC Very Low Frequency transient monitoring program were performed. The results are summarized and relevant references are included.

Paciesas, William S.

1991-01-01

115

Gamma-ray telescopes  

Microsoft Academic Search

The last half-century has seen dramatic developments in ??ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent\\u000a research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as ??ray bursts, blazars, Galactic transients, and the Galactic distribution of 26Al.

Neil Gehrels; John K. Cannizzo

2009-01-01

116

Determination of Fluorine in Fourteen Microanalytical Geologic Reference Materials using SIMS, EPMA, and Proton Induced Gamma Ray Emission (PIGE) Analysis  

NASA Astrophysics Data System (ADS)

Fluorine (F) is a volatile constituent of magmas and hydrous minerals, and trace amounts of F are incorporated into nominally anhydrous minerals such as olivine and clinopyroxene. Microanalytical techniques are routinely used to measure trace amounts of F at both high sensitivity and high spatial resolution in glasses and crystals. However, there are few well-established F concentrations for the glass standards routinely used in microanalytical laboratories, particularly standards of low silica, basaltic composition. In this study, we determined the F content of fourteen commonly used microanalytical glass standards of basaltic, intermediate, and rhyolitic composition. To serve as calibration standards, five basaltic glasses with ~0.2 to 2.5 wt% F were synthesized and characterized. A natural tholeiite from the East Pacific Rise was mixed with variable amounts of CaF2. The mixture was heated in a 1 atmosphere furnace to 1440 C at fO2 = NNO for 30 minutes and quenched in water. Portions of the run products were studied by electron probe microanalysis (EPMA) and secondary ion mass spectrometry (SIMS). The EPMA used a 15 m diameter defocused electron beam with a 15 kV accelerating voltage and a 25 nA primary current, a TAP crystal for detecting FK? X-rays, and Biotite 3 as the F standard. The F contents by EPMA agreed with the F added to the basalts after correction for mass loss during melting. The SIMS analyses used a primary beam of 16O- and detection of low-energy negative ions (-5 kV) at a mass resolution that resolved 18OH. Both microanalytical techniques confirmed homogeneity, and the SIMS calibration defined by EPMA shows an excellent linear trend with backgrounds of 2 ppm or less. Analyses of basaltic glass standards based on our synthesized calibration standards gave the following F contents and 2? errors (ppm): ALV-519 = 83 3; BCR-2G = 359 6; BHVO-2G = 322 15; GSA-1G = 10 1; GSC-1G = 11 1; GSD-1G = 19 2; GSE-1G = 173 1; KL2G (MPI-DING) = 101 1; ML3B-G (MPI-DING) = 49 17. These values are lower than published values for BCR-2 and BHVO-2 (unmelted powders) and the information values for the MPI-DING glass standards. Proton Induced Gamma ray Emission (PIGE) was tested for the high silica samples. PIGE analyses (1.7 MeV Tandem Accelerator; reaction type: 19F(p, ??)16O; primary current = 20-30 nA; incident beam voltage = 1.5 MeV) were calibrated with a crystal of fluor-topaz (F = 20.3 wt%) and gave F values of: NIST 610 = 266 14 ppm; NIST 620 = 54 5 ppm; and UTR-2 = 1432 32 ppm. SIMS calibration defined by the PIGE analyses shows an excellent linear trend with low background similar to the basaltic calibration. The F concentrations of intermediate MPI-DING glasses were determined based on SIMS calibration generated from the PIGE analysis above. The F concentrations and 2? errors (ppm) are: T1G = 219.9 6.8; StHs/680-G = 278.0 2.0 ppm. This study revealed a large matrix effect between the high-silica and basaltic glasses, thus requiring the use of appropriate standards and separate SIMS calibrations when analyzing samples of different compositions.

Guggino, S. N.; Hervig, R. L.

2010-12-01

117

Gamma-Ray Burst Wallsheet  

NSDL National Science Digital Library

The Gamma-ray Burst Wallsheet was developed to illustrate the properties of light emanating from a gamma-ray burst as seen by three distant satellites, including NASA's Swift. The back of the wallsheet has one of the three activities in the accompanying educator guide (Angling for Gamma-ray Bursts).

2005-01-01

118

Gamma ray astronomy in perspective  

NASA Technical Reports Server (NTRS)

A brief overview of the development of gamma ray astronomy is presented. Gamma ray telescopes and other optical measuring instruments are highlighted. Emphasis is placed on findings that were unobtainable before gamma ray astronomy. Information on evolution of the solar system, the relationship of the solar system to the galaxy, and the composition of interstellar matter is discussed.

1981-01-01

119

Modeling Photodisintegration-induced TeV Photon Emission from Low-luminosity Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Ultra-high-energy cosmic-ray heavy nuclei have recently been considered as originating from nearby low-luminosity gamma-ray bursts that are associated with Type Ibc supernovae. Unlike the power-law decay in long duration gamma-ray bursts, the light curve of these bursts exhibits complex UV/optical behavior: shock breakout dominated thermal radiation peaks at about 1 day, and, after that, nearly constant emission sustained by radioactive materials for tens of days. We show that the highly boosted heavy nuclei at PeV energy interacting with the UV/optical photon field will produce considerable TeV photons via the photodisintegration/photo-de-excitation process. It was later predicted that a thermal-like ?-ray spectrum peaks at about a few TeV, which may serve as evidence of nucleus acceleration. The future observations by the space telescope Fermi and by the ground atmospheric Cherenkov telescopes such as H.E.S.S., VERITAS, and MAGIC will shed light on this prediction.

Liu, Xue-Wen; Wu, Xue-Feng; Lu, Tan

2012-05-01

120

Topics in gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Observations of gamma rays from solar flares, gamma ray bursts, the Galactic center, galactic nucleosynthesis, SS433, and Cygnus X-3, and their effects on astrophysical problems are discussed. It is observed that gamma ray spectra from solar flares are applicable to the study of particle acceleration and confinement and the determination of chemical abundances in the solar atmosphere. The gamma ray lines from the compact galactic object SS433 are utilized to examine the acceleration of jets, and analysis of the gamma ray lines of Cygnus X-3 reveal that particles can be accelerated in compact sources to ultrahigh energies.

Ramaty, R.; Lingenfelter, R. E.

1986-01-01

121

Solar Flares: Gamma Rays  

E-print Network

We briefly review the theory of gamma ray production in solar flares and present the highlights of the observations and their implications. Specifically: (i) the gamma ray data show that a large fraction of the released flare energy is in accelerated ions, mostly around 1 MeV/nucleon; (ii) the accelerated He-3, heavy ion, and relativistic electron abundances are enriched, implying that the particle acceleration is dominated by stochastic gyroresonant interactions with plasma turbulence; (iii) there is evidence for the enhancement of the abundances of ambient chromospheric elements with low first ionization potentials; (iv) the observed Li-7 and Be-7 lines, at 0.429 MeV and 0.478 MeV due to alpha-alpha interactions, show that both the accelerated alpha particle and the ambient He abundances are significantly enhanced.

Reuven Ramaty; Natalie Mandzhavidze

1998-10-06

122

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

The Burst and Transient Source Experiment (BATSE) is one of four instruments on the Compton observatory which was launched by the space shuttle Atlantis on April 5, 1991. As of mid-March, 1994, BATSE detected more than 925 cosmic gamma-ray bursts and more than 725 solar flares. Pulsed gamma rays have been detected from at least 16 sources and emission from at least 28 sources (including most of the pulsed sources) has been detected by the earth occultation technique. UAH participation in BATSE is extensive but can be divided into two main areas, operations and data analysis. The daily BATSE operations tasks represent a substantial level of effort and involve a large team composed of MSFC personnel as well as contractors such as UAH. The scientific data reduction and analysis of BATSE data is also a substantial level of effort in which UAH personnel have made significant contributions.

Paciesas, William S.

1994-01-01

123

Gamma ray collimator  

NASA Technical Reports Server (NTRS)

A gamma ray collimator including a housing having first and second sections is disclosed. The first section encloses a first section of depleted uranium which is disposed for receiving and supporting a radiation emitting component such as cobalt 60. The second section encloses a depleted uranium member which is provided with a conical cut out focusing portion disposed in communication with the radiation emitting element for focusing the emitted radiation to the target.

Casanova, Edgar J. (inventor)

1991-01-01

124

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars  

SciTech Connect

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.

Massaro, F.; D'Abrusco, R.; Tosti, G.; Ajello, M.; Gasparrini, A.Paggi.D.

2012-04-02

125

UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS  

SciTech Connect

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.

Massaro, F.; Ajello, M. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D'Abrusco, R.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Tosti, G. [Dipartimento di Fisica, Universita degli Studi di Perugia, 06123 Perugia (Italy); Gasparrini, D. [ASI Science Data Center, ESRIN, I-00044 Frascati (Italy)

2012-06-10

126

Simulation of prompt gamma-ray emission during proton radiotherapy  

Microsoft Academic Search

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector

Joost M Verburg; Helen A Shih; Joao Seco

2012-01-01

127

Fuzzy correlations of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

The origin of gamma-ray bursts is not known, both in the sense of the nature of the source emitting the radiation and literally, the position of the burst on the sky. Lacking unambiguously identified counterparts in any wavelength band studied to date, statistical approaches are required to determine the burster distance scale. Angular correlation analysis is one of the most powerful tools in this regard. However, poor detector resolution gives large localization errors, effectively beam smearing the positions. The resulting fuzzy angular correlation function is investigated and the generic isotropization that smearing induces on any intrinsic clustering is discussed. In particular, the extent to which gamma-ray burst observations by the BATSE detector aboard the Gamma-Ray Observatory might recover an intrinsic source correlation is investigated.

Hartmann, Dieter H.; Linder, Eric V.; Blumenthal, George R.

1991-01-01

128

Gamma-ray localization of terrestrial gamma-ray flashes.  

PubMed

Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of ?5-10 at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the subsatellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space. PMID:20867680

Marisaldi, M; Argan, A; Trois, A; Giuliani, A; Tavani, M; Labanti, C; Fuschino, F; Bulgarelli, A; Longo, F; Barbiellini, G; Del Monte, E; Moretti, E; Trifoglio, M; Costa, E; Caraveo, P; Cattaneo, P W; Chen, A; D'Ammando, F; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Froysland, T; Galli, M; Gianotti, F; Lapshov, I; Lazzarotto, F; Lipari, P; Mereghetti, S; Morselli, A; Pacciani, L; Pellizzoni, A; Perotti, F; Picozza, P; Piano, G; Pilia, M; Prest, M; Pucella, G; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Soffitta, P; Striani, E; Vallazza, E; Vercellone, S; Vittorini, V; Zambra, A; Zanello, D; Antonelli, L A; Colafrancesco, S; Cutini, S; Giommi, P; Lucarelli, F; Pittori, C; Santolamazza, P; Verrecchia, F; Salotti, L

2010-09-17

129

Gamma rays produce superior seedless citrus  

SciTech Connect

Using gamma radiation, seedless forms of some varieties of oranges and grapefruit are being produced. Since it has long been known that radiation causes mutations in plants and animals, experiments were conducted to determine if seediness could be altered by exposing seeds or budwood to higher than natural doses of gamma radiation. Orange and grapefruit seeds and cuttings exposed to gamma rays in the early 1970's have produced trees that bear fruit superior to that now on the market.

Pyrah, D.

1984-10-01

130

Intrinsic and dust-induced polarization in gamma-ray burst afterglows: the case of GRB 021004  

E-print Network

Polarization measurements for the optical counterpart to GRB 021004 are presented and discussed. Our observations were performed with the TNG and the VLT-UT3 (Melipal) during the first and fourth night after the gamma-ray burst discovery. We find robust evidence of temporal evolution of the polarization, which is therefore, at least partially, intrinsic to the optical transient. We do not find convincing evidence of wavelength dependence for the intrinsic polarization of the transient, in agreement with current polarization models for optical afterglows. We discuss the role of dust, both in our galaxy and in the host, in modifying the transmitted polarization vector, showing how a sizable fraction of the observed polarized flux is due to Galactic selective extinction, while it is not possible to single out any clear contribution from dust in the host galaxy. We discuss how our data compare to those obtained by different groups showing that a two-component model is required to describe the complete dataset. This is not surprising given the complex lightcurve of GRB 021004.

D. Lazzati; S. Covino; S. di Serego Alighieri; G. Ghisellini; J. Vernet; E. Le Floc'h; D. Fugazza; S. Di Tomaso; D. Malesani; N. Masetti; E. Pian; E. Oliva; L. Stella

2003-08-29

131

{gamma} ray astronomy with muons  

SciTech Connect

Although {gamma} ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard {gamma} ray spectra there is a relative {open_quotes}enhancement{close_quotes} of muons from {gamma} ray primaries as compared to that from nucleon primaries. All shower {gamma} rays above the photoproduction threshold contribute to the number of muons N{sub {mu}}, which is thus proportional to the primary {gamma} ray energy. With {gamma} ray energy 50 times higher than the muon energy and a probability of muon production by the {gamma}{close_quote}s of about 1{percent}, muon detectors can match the detection efficiency of a GeV satellite detector if their effective area is larger by 10{sup 4}. The muons must have enough energy for sufficiently accurate reconstruction of their direction for doing astronomy. These conditions are satisfied by relatively shallow neutrino detectors such as AMANDA and Lake Baikal, and by {gamma} ray detectors such as MILAGRO. TeV muons from {gamma} ray primaries, on the other hand, are rare because they are only produced by higher energy {gamma} rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal, and MILAGRO detectors. {copyright} {ital 1997} {ital The American Physical Society}

Halzen, F. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Stanev, T. [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States)] [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States); Yodh, G.B. [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)] [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)

1997-04-01

132

Gamma Ray Astronomy with Muons  

E-print Network

Although gamma ray showers are muon-poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative `enhancement' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the photoproduction threshold contribute to the number of muons $N_\\mu$, which is thus proportional to the primary gamma ray energy. With gamma ray energy 50 times higher than the muon energy and a probability of muon production by the gammas of about 1\\%, muon detectors can match the detection efficiency of a GeV satellite detector if their effective area is larger by $10^4$. The muons must have enough energy for sufficiently accurate reconstruction of their direction for doing astronomy. These conditions are satisfied by relatively shallow neutrino detectors such as AMANDA and Lake Baikal and by gamma ray detectors like MILAGRO. TeV muons from gamma ray primaries, on the other hand, are rare because they are only produced by higher energy gamma rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal and MILAGRO detectors.

F. Halzen; T. Stanev; G. B. Yodh

1996-08-29

133

Digital Pulse Processing and Gamma Ray Tracking  

NSDL National Science Digital Library

Two of the big changes in new generations of Nuclear Physics instrumentation will be the incorporation of digital processing and the use of gamma ray tracking. The Nuclear Physics Group at Daresbury has set up a project to investigate digital pulse processing for gamma ray detectors and how best to implement gamma ray tracking in large Germanium gamma ray detectors. Topics on this site include but are not limited to: gamma ray tracking, overview of the Gamma Ray Tracking Project, pictures of one of the tracking gamma ray detectors (TIGRE), pictures of test experiment, gamma ray tracking project publications, and links to other gamma ray tracking pages.

134

VERY HIGH ENERGY GAMMA RAY Tadashi KIFUNE  

E-print Network

VERY HIGH ENERGY GAMMA RAY ASTRONOMY Tadashi KIFUNE Institute for Cosmic Ray Research, University for the photon of background radiation field. The gamma ray reactions characterize VHE gamma ray astronomy­based tech­ nique to detect TeV gamma rays. The current status of gamma ray astronomy in its growing stage

Enomoto, Ryoji

135

Polarization mesurements of gamma ray bursts and axion like particles  

E-print Network

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of axion like particles (ALPs). Based on evidences of polarized gamma ray emission detected in several gamma ray bursts we estimated the level of ALPs induced dichroism, which could take place in the magnetized fireball environment of a GRB. This allows to estimate the sensitivity of polarization measurements of GRBs to the ALP-photon coupling. This sensitivity $\\gag\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the ALP mass $m_a=10^{-3}~{\\rm eV}$ and MeV energy spread of gamma ray emission is competitive with the sensitivity of CAST and becomes even stronger for lower ALPs masses.

Andre Rubbia; Alexander Sakharov

2008-09-03

136

The Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D.

1994-01-01

137

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D.

1994-06-01

138

The Compton Gamma Ray Observatory  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments,

N. Gehrels; E. Chipman; D. Kniffen

1994-01-01

139

Gamma Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. There has been tremendous recent progress in our understanding of bursts with the new data from the Swift mission. Swift was launched in November 2004 and is a multiwave length observatory designed to determine the origin of bursts and use them to probe the early Universe. It was developed and is being operated by an international team of scientists from the US, UK and Italian. The first year of findings from the mission will be presented. A large step forward has been made in our understanding of the mysterious short GRBs. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gehrels, Neil

2006-01-01

140

Gamma Ray Bursts - Observations  

NASA Technical Reports Server (NTRS)

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.

Gehrels, N.; Cannizzo, J. K.

2010-01-01

141

Gamma-Ray Pulsar Revolution  

NASA Astrophysics Data System (ADS)

Isolated neutron stars (INSs) were the first sources identified in the field of high-energy gamma-ray astronomy. In the 1970s, only two sources had been identified, the Crab and Vela pulsars. However, although few in number, these objects were crucial in establishing the very concept of a gamma-ray source. Moreover, they opened up significant discovery space in both the theoretical and phenomenological fronts. The need to explain the copious gamma-ray emission of these pulsars led to breakthrough developments in understanding the structure and physics of neutron star (NS) magnetospheres. In parallel, the 20-year-long chase to understand the nature of Geminga unveiled the existence of a radio-quiet, gamma-ray-emitting INS, adding a new dimension to the INS family. We are living through an extraordinary time of discovery. The current generation of gamma-ray detectors has vastly increased the population of known gamma-ray-emitting NSs. The 100 mark was crossed in 2011, and we are now over 150. The gamma-ray-emitting NS population exhibits roughly equal numbers of radio-loud and radio-quiet young INSs, plus an astonishing, and unexpected, group of isolated and binary millisecond pulsars (MSPs). The number of MSPs is growing so rapidly that they are on their way to becoming the most numerous members of the family of gamma-ray-emitting NSs. Even as these findings have set the stage for a revolution in our understanding of gamma-ray-emitting NSs, long-term monitoring of the gamma-ray sky has revealed evidence of flux variability in the Crab Nebula as well as in the pulsed emission from PSR J2021+4026, challenging a four-decades-old, constant-emission paradigm. Now we know that both pulsars and their nebulae can, indeed, display variable emission.

Caraveo, Patrizia A.

2014-08-01

142

Cross sections relevant to gamma-ray line emission in solar flares: $^3$He-induced reactions on $^{16}$O nuclei  

E-print Network

Gamma-ray production cross sections have been measured for gamma-ray lines copiously emitted in the $^3$He bombardment of $^{16}$O nuclei: the 937, 1042 and 1081 keV lines of $^{18}$F and the 1887 keV line of $^{18}$Ne. Four Ge detectors with BGO shielding for Compton suppression were used to measure the angular distributions of the gamma-rays. The excitation functions have been obtained for $^3$He bombarding energies from 3.7 to 36 MeV. Total cross sections are tabulated for calculations relevant to gamma-ray astronomy. The importance of these lines as diagnosis for the presence and properties of accelerated $^3$He in solar flares is discussed in light of the measured cross sections.

V. Tatischeff; J. Duprat; J. Kiener; M. Assuncao; A. Coc; C. Engrand; M. Gounelle; A. Lefebvre; M. -G. Porquet; N. De Sereville; J. -P. Thibaud; C. Bourgeois; M. Chabot; F. Hammache; J. -A. Scarpaci

2003-08-25

143

CO sub 2 ter dot minus radical induced cleavage of disulfide bonds in proteins. A gamma-ray and pulse radiolysis mechanistic investigation  

SciTech Connect

Disulfide bond reduction by the CO{sub 2}{sup {center dot}{minus}} radical was investigated in aponeocarzinostatin, aporiboflavin-binding protein, and bovine immunoglobulin. Protein-bound cysteine free thiols were formed under {gamma}-ray irradiation in the course of a pH-dependent and protein concentration dependent chain reaction. The chain efficiency increased upon acidification of the medium, with an apparent pK{sub a} around 5, and decreased abruptly below pH 3.6. It decreased also at neutral pH as cysteine accumulated. From pulse radiolysis analysis, CO{sub 2}{sup {center dot}{minus}} proved able to induce rapid one-electron oxidation of thiols and of tyrosine phenolic groups in addition to one-electron donation to exposed disulfide bonds. The bulk rate constant of CO{sub 2}{sup {center dot}{minus}} uptake by the native proteins was 5{minus} to 10-fold faster at pH 3 than at pH 8, and the protonated form of the disulfide radical anion, appeared to be the major protein radical species formed under acidic conditions. Formation of the disulfide radical cation, phenoxyl radical Tyr-O{sup {center dot}} disproportionation, and phenoxyl radical induced oxidation of preformed thiol groups should also be taken into consideration to explain the fate of the oxygen-centered phenoxyl radical.

Favaudon, V.; Tourbez, H.; Lhoste, J-M. (Institut Curie-Biologie, Orsay (France)); Houee-Levin, C. (Univ. Rene-Descartes, Paris (France))

1990-12-01

144

High energy gamma ray astronomy  

NASA Technical Reports Server (NTRS)

High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.

Fichtel, Carl E.

1987-01-01

145

Loss of a putative tumor suppressor locus after gamma-ray-induced neoplastic transformation of HeLa x Skin fibroblast human cell hybrids  

SciTech Connect

The nontumorigenic HeLa x skin fibroblast hybrid cell line, CGL1, can be induced to re-express HeLa tumor-associated cell surface antigen, p75-IAP (intestinal alkaline phosphatase), with resulting neoplastic transformation, by exposure to {gamma} radiation. This has allowed the human hybrid system to be developed into a quantitative in vitro model for radiation-induced neoplastic transformation of human cells. Recently, several {gamma}-ray-induced IAP-expression mutants (GIMs) of the nontumorigenic HeLa x skin fibroblast hybrid CGL1 were isolated and all were tumorigenic when injected subcutaneously into nude mice. Control cell lines which were negative for p75-IAP (CONs) were also isolated from irradiated populations, and none were found to be tumorigenic. We have now begun to investigate the molecular basis of radiation-induced neoplastic transformation in this system by studying the potential genetic linkage between p75/IAP expression, tumorigenicity and damage to a putative tumor suppressor locus on fibroblast chromosome 11. Previous analysis of rare spontaneous segregants has indicated that this locus is involved in the regulation of tumorigenicity and in the expression of the HeLa tumor-associated cell surface marker intestinal alkaline phosphatase (p75-IAP) in this system. Therefore, analysis by restriction fragment length polymorphism and chromosome painting have been performed for chromosome 11, and for chromosome 13 as a control, for the p75/IAP-positive GIM and p75/IAP-negative CON cell lines. We report that in five of eight of the GIMs large-scale damage to the fibroblast chromosome 11`s is evident (four GIMs have lost one complete copy of a fibroblast chromosome 11 heavily damaged). None of the CONs, however (0/5), have lost a complete copy of either fibroblast chromosome 11. No large-scale damage to the control chromosome 13`s was detected in the GIMs or CONs. 49 refs., 3 figs., 2 tabs.

Mendonca, M.S.; Redpath, J.L.; Fasching, C.L. [Univ. of California, Irvine, CA (United States)

1995-07-01

146

Mutagenic response of rhodes grass (Chloris gayanaKunth.) to gamma rays. II. Studies on second (M2) generation parameters  

Microsoft Academic Search

The effect of gamma rays on parameters such as chlorophyll mutation frequency and spectrum, mutagenic effectiveness and efficiency and viable mutation frequency and spectrum were studied in M2 generation of Rhodes grass employing nine doses of gamma rays. The chlorophyll mutation frequency increased in a linear fashion at low and medium doses and was erratic at higher doses. The chlorophyll

G. Krishna; G. Shivashankar; J. Nath

1984-01-01

147

Gamma-Ray Burst Lines  

E-print Network

The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980's, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features around 400 keV. During the 1990's the situation has become much less clear. A small fraction of bursts observed with BATSE have statistically significant low-energy features, but the reality of the features is suspect because in several cases the data of the BATSE detectors appear to be inconsistent. Furthermore, most of the possible features appear in emission rather than the expected absorption. Analysis of data from other instruments has either not been finalized or has not detected lines.

Michael S. Briggs

1999-10-20

148

Gamma Ray Bursts and CETI  

E-print Network

Gamma ray burst sources are isotropically distributed. They could be located at distances $\\sim 1000$ AU. (Katz \\cite{JK92}) GRB signals have many narrow peaks that are unresolved at the millisecond time resolution of existing observations. \\cite{JK87} CETI could use stars as gravitational lenses for interstellar gamma ray laser beam communication. Much better time resolution of GRB signals could rule out (or confirm?) the speculative hypothesis that GRB = CETI.

Frank D. Smith Jr

1993-02-10

149

Gamma-ray burst afterglows  

Microsoft Academic Search

The discovery of counterparts in X-ray and optical to radio wavelengths has revolutionized the study of gamma-ray bursts, until recently the most enigmatic of astrophysical phenomena. We now know that gamma-ray bursts are the biggest explosions in nature, caused by the ejection of ultrarelativistic matter from a powerful energy source and its subsequent collision with its environment. We have just

Paradijs van J. A; Chryssa Kouveliotou; Ralph A. M. J. Wijers

2000-01-01

150

Multiwavelength Astronomy: Gamma Ray Science  

NSDL National Science Digital Library

Dieter Hartmann, a high-energy physicist, presents a story-based lesson on the science of Gamma-Ray astronomy. The lesson focuses on gamma-ray bursts; examining their sources, types, and links to the origin and evolution of the Universe. The story-based format of the lesson also provides insights into the nature of science. Students answer questions based on the reading guide. A list of supplemental websites is also included.

151

Gamma-ray line astronomy  

NASA Technical Reports Server (NTRS)

Gamma-ray astronomy is a valuable source of information on solar activity, supernovae, and nucleosynthesis. Cosmic gamma-ray lines were first observed from solar flares and more recently from the galactic center and a transient event. The latter may give an important insight into nuclear reactions taking place near neutron stars and black holes and a measure of the gravitational redshifts of such objects.

Ramaty, R.; Lingenfelter, R. E.

1979-01-01

152

Swift: Gamma-Ray Bursts  

NSDL National Science Digital Library

In the late 1960s, scientists accidentally discovered gamma-ray bursts, intense flashes of energy that typically last no more than a few seconds or minutes. For decades after the discovery of these powerful bursts, they remained one of the greatest mysteries in astronomy. This video segment discusses the Swift satellite mission, launched in 2004 to investigate gamma-ray bursts, and presents some theories as to their origins. The segment is four minutes fourteen seconds in length.

153

Gamma ray bursts ROBERT S MACKAY  

E-print Network

Gamma ray bursts ROBERT S MACKAY COLIN ROURKE We propose that a gamma ray burst is a kinematic Gamma ray bursts are intense flashes of electromagnetic radiation of cosmic origin lasting from ten accepted mechanism. We propose that a gamma ray burst is simply a kinematic effect, namely the effect

Rourke, Colin

154

VERY HIGH ENERGY GAMMA RAY Tadashi KIFUNE  

E-print Network

VERY HIGH ENERGY GAMMA RAY ASTRONOMY Tadashi KIFUNE Institute for Cosmic Ray Research, University radiation eld. The gamma ray reactions characterize VHE gamma ray astronomy. The Universe, through the high primordial black holes, acted, to some extent, as impetus for promoting gamma ray astronomy. Although

Enomoto, Ryoji

155

Hard X-ray and gamma-rays from supernovae  

NASA Technical Reports Server (NTRS)

The hard electromagnetic radiation produced by and accompanying the explosion of supernovae is discussed. This radiation may have three origins: (i) the eruption of the shock wave from the surface of the star; (ii) radioactive decay of unstable isotopes produced during the explosion; and (iii) gamma-rays produced by neutrino annihilation following accretion-induced collapse. Though the latter has been proposed as a mechanism for making cosmological gamma-ray bursts, it is shown that this is unlikely.

Woosley, S. E.

1993-01-01

156

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than that of previous observations. The 16,000 kilogram observatory contains four instruments on a stabilized platform. The mission began normal operations on 16 May 1991 and is now over half-way through a full-sky survey. The mission duration is expected to be from six to ten years. A Science Support Center has been established at Goddard Space Flight Center for the purpose of supporting a vigorous Guest Investigator Program. New scientific results to date include: (1) the establishment of the isotropy, combined with spatial inhomogeneity, of the distribution of gamma-ray bursts in the sky; (2) the discovery of intense high energy (100 MeV) gamma-ray emission from 3C 279 and other quasars and BL Lac objects, making these the most distant and luminous gamma-ray sources ever detected; (3) one of the first images of a gamma-ray burst; (4) the observation of intense nuclear and position-annihilation gamma-ray lines and neutrons from several large solar flares; and (5) the detection of a third gamma-ray pulsar, plus several other transient and pulsing hard X-ray sources.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

1993-01-01

157

Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

This photograph shows the Compton Gamma-Ray Observatory (GRO) being deployed by the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-37 mission in April 1991. The GRO reentered Earth atmosphere and ended its successful mission in June 2000. For nearly 9 years, the GRO Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center (MSFC), kept an unblinking watch on the universe to alert scientists to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of stars, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in the BATSE science program.

1991-01-01

158

Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

This photograph shows the Compton Gamma-Ray Observatory being released from the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-35 mission in April 1991. The GRO reentered the Earth's atmosphere and ended its successful mission in June 2000. For nearly 9 years, GRO's Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center, kept an unblinking watch on the universe to alert scientist to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of star, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in BATSE's science program.

1991-01-01

159

Study of radiation dose induced by cosmic-ray origin low-energy gamma rays and electrons near sea level  

NASA Astrophysics Data System (ADS)

For a long time, it has been known that low-energy continuous gamma radiation is present in open air at the Earth's surface. In previous investigations it was assumed that this radiation is produced almost exclusively by gamma photons emitted due to the natural radioactivity, which are backscattered by air above ground. We show that significant amount of this radiation (related to energy region 30-300 keV) that peaks at about 90 keV, is produced by cosmic-rays, with the photon flux of about 3000 m-2 s-1. We find that the contribution of this omnipresent low-energy gamma radiation of cosmic-ray origin, including the corresponding low-energy electron flux, to the doses of general population are non-negligible components of overall doses induced by cosmic rays near sea level.

Mrdja, D.; Bikit, I.; Bikit, K.; Slivka, J.; Anicin, I.

2015-02-01

160

Apoptosis (cell death) induced in mouse bowel by 1,2-dimethylhydrazine, methylazoxymethanol acetate, and gamma-rays  

SciTech Connect

Apoptosis is a pattern of cell death involving nuclear pyknosis, cytoplasmic condensation, and karyorrhexis. The frequency of apoptosis after treatment with two colon carcinogens and radiation was studied in the crypts of five different portions of mouse bowel. When 1,2-dimethylhydrazine (DMH) was injected s.c., the earliest rise in apoptotic incidence after a high dose (200 mg/kg) was noted at 3 h in small intestine and at 6 h in large bowel. After i.p. administration of methylazoxymethanol (MAM) acetate, apoptotic cells were seen in large bowel after 3 h. When the plateau values attained after high doses of DMH were compared, many apoptotic cells were found in the lower part of the large bowel, whereas few such cells were observed in the small intestine and the upper part of the large bowel. This finding was reversed in the case of radiation-induced apoptosis. In the descending colon, a definite circadian rhythm in the apoptotic incidence was observed 6 h after injection of DMH or MAM acetate. Apoptosis showed a high incidence when these drugs were given between 2400 h and 0900 h, but a low incidence after administration between 1200 h and 2100 h. In the small intestine a rhythm was also noted for MAM acetate, but not significantly for DMH.

Ijiri, K. (Univ. of Tokyo (Japan))

1989-11-15

161

{gamma}-ray production by proton and {alpha}-particle induced reactions on {sup 12}C, {sup 16}O, {sup 24}Mg, and Fe  

SciTech Connect

{gamma}-ray production cross sections for proton and {alpha}-particle interactions with {sup 12}C, {sup 16}O, {sup 24}Mg, and Fe have been measured in the energy range 5-25 MeV with proton beams and 5-40 MeV with {alpha}-particle beams. Isotopically pure foils of {sup 24}Mg and foils of natural isotopical composition of C, MgO, and Fe have been used. {gamma}-ray angular distributions were obtained with five high-purity Ge detectors with bismuth germanate Compton shields placed at angles of 45 deg. to 157.5 deg. Cross sections for more than 50 different {gamma}-ray transitions were extracted, and for many of them no data have been published before. Comparison of present data with data available in the literature shows mostly good to excellent agreement. In addition to the production cross sections, high-statistics, low-background line shapes of the 4.438 MeV {sup 12}C {gamma} ray from inelastic scattering off {sup 12}C and spallation of {sup 16}O were obtained. Comparison with nuclear reaction calculations shows that these data place interesting constraints on nuclear reaction models.

Belhout, A.; Kiener, J.; Coc, A.; Duprat, J.; Engrand, C.; Fitoussi, C.; Gounelle, M.; Lefebvre-Schuhl, A.; Sereville, N. de; Tatischeff, V.; Thibaud, J.-P.; Chabot, M.; Hammache, F.; Benhabiles-Mezhoud, H. [USTHB, Faculte de Physique, BP 32, El-Alia, 16111 Bab Ezzouar, Algiers (Algeria); Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse (CSNSM), CNRS-IN2P3 et Universite Paris-Sud, F-91405 Orsay Campus (France); Institut de Physique Nucleaire (IPN), CNRS-IN2P3 et Universite Paris-Sud, F-91400 Orsay (France); Departement de Physique, Universite de Boumerdes, Avenue de l'Independance, 35000 Boumerdes (Algeria)

2007-09-15

162

Terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

Lightning and thunderstorm systems in general have been recently recognized as powerful particle accelerators, capable of producing electrons, positrons, gamma-rays and neutrons with energies as high as several tens of MeV. In fact, these natural systems turn out to be the highest energy and most efficient natural particle accelerators on Earth. Terrestrial Gamma-ray Flashes (TGFs) are millisecond long, very intense bursts of gamma-rays and are one of the most intriguing manifestation of these natural accelerators. Only three currently operative missions are capable of detecting TGFs from space: the RHESSI, Fermi and AGILE satellites. In this paper we review the characteristics of TGFs, including energy spectrum, timing structure, beam geometry and correlation with lightning, and the basic principles of the associated production models. Then we focus on the recent AGILE discoveries concerning the high energy extension of the TGF spectrum up to 100 MeV, which is difficult to reconcile with current theoretical models.

Marisaldi, Martino; Fuschino, Fabio; Labanti, Claudio; Tavani, Marco; Argan, Andrea; Del Monte, Ettore; Longo, Francesco; Barbiellini, Guido; Giuliani, Andrea; Trois, Alessio; Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo

2013-08-01

163

Upgrade of the JET Gamma-Ray Cameras  

NASA Astrophysics Data System (ADS)

The JET gamma-ray camera diagnostics have already provided valuable information on the gamma-ray imaging of fast ion in JET plasmas /1,2/. The applicability of gamma-ray imaging to high performance deuterium and deuterium-tritium JET discharges is strongly dependent on the fulfilment of rather strict requirements for the characterisation of the neutron and gamma-ray radiation fields. These requirements have to be satisfied within very stringent boundary conditions for the design, such as the requirement of minimum impact on the co-existing neutron camera diagnostics. The JET Gamma-Ray Cameras (GRC) upgrade project deals with these issues with particular emphasis on the design of appropriate neutron/gamma-ray filters ("neutron attenuators"). Several design versions have been developed and evaluated for the JET GRC neutron attenuators at the conceptual design level. The main design parameter was the neutron attenuation factor. The two design solutions, that have been finally chosen and developed at the level of scheme design, consist of: a) one quasi-crescent shaped neutron attenuator (for the horizontal camera) and b) two quasi-trapezoid shaped neutron attenuators (for the vertical one). The second design solution has different attenuation lengths: a short version, to be used together with the horizontal attenuator for deuterium discharges, and a long version to be used for high performance deuterium and DT discharges. Various neutron-attenuating materials have been considered (lithium hydride with natural isotopic composition and 6Li enriched, light and heavy water, polyethylene). Pure light water was finally chosen as the attenuating material for the JET gamma-ray cameras. The neutron attenuators will be steered in and out of the detector line-of-sight by means of an electro-pneumatic steering and control system. The MCNP code was used for neutron and gamma ray transport in order to evaluate the effect of the neutron attenuators on the neutron field of the JET GRC. The modelling was dedicated to the estimation of neutron and (plasma-emitted) gamma-ray attenuation, neutron-induced gamma-ray background and the neutron in-scattering impact on the neutron detectors due to the attenuator in the parking location. A numerical study of the gamma-ray detector (CsI(Tl)) was done by means of the IST Monte Carlo code. It provided preliminary results on the detector efficiency and response function.

Soare, S.; Zoita, V.; Craciunescu, T.; Curuia, M.; Kiptily, V.; Lengar, I.; Murari, A.; Prior, P.; Anghel, M.; Bonheure, G.; Constantin, M.; David, E.; Edlington, T.; Falie, D.; Griph, S.; Le Guern, F.; Krivchenkov, Y.; Loughlin, M.; Pantea, A.; Popovichev, S.; Riccardo, V.; Syme, B.; Thompson, V.; Tiseanu, I.

2008-03-01

164

Neutrinos from Gamma Ray Bursts  

E-print Network

We show that the detection of neutrinos from a typical gamma ray burst requires a kilometer-scale detector. We argue that large bursts should be visible with the neutrino telescopes under construction. We emphasize the 3 techniques by which neutrino telescopes can perform this search: by triggering on i) bursts of muons from muon neutrinos, ii) muons from air cascades initiated by high energy gamma rays and iii) showers made by relatively low energy ($\\simeq 100\\,\\mev$) electron neutrinos. Timing of neutrino-photon coincidences may yield a measurement of the neutrino mass to order $10^{-5}$~eV, an interesting range in light of the solar neutrino anomaly.

F. Halzen; G. Jaczko

1996-02-07

165

Gamma-ray Imaging Methods  

SciTech Connect

In this document we discuss specific implementations for gamma-ray imaging instruments including the principle of operation and describe systems which have been built and demonstrated as well as systems currently under development. There are several fundamentally different technologies each with specific operational requirements and performance trade offs. We provide an overview of the different gamma-ray imaging techniques and briefly discuss challenges and limitations associated with each modality (in the appendix we give detailed descriptions of specific implementations for many of these technologies). In Section 3 we summarize the performance and operational aspects in tabular form as an aid for comparing technologies and mapping technologies to potential applications.

Vetter, K; Mihailescu, L; Nelson, K; Valentine, J; Wright, D

2006-10-05

166

On Gamma-Ray Bursts  

E-print Network

(Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the process of gravitational collapse, leading to the creation of an electron-positron-photon plasma: the basic self-accelerating system explaining both the energetics and the high energy Lorentz factor observed in GRBs. We then turn to recall the two basic interpretational paradigms of our GRB model. [...] We then turn to the special role of the baryon loading in discriminating between "genuine" short and long or "fake" short GRBs [...] We finally turn to the GRB-Supernova Time Sequence (GSTS) paradigm: the concept of induced gravitational collapse. [...] We then present some general conclusions.

Remo Ruffini; Maria Grazia Bernardini; Carlo Luciano Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; Maria Giovanna Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; Jorge Armando Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

2008-04-17

167

Background modelling in very-high-energy gamma-ray astronomy  

Microsoft Academic Search

Context: Ground based Cherenkov telescope systems measure astrophysical gamma-ray emission against a background of cosmic-ray induced air showers. The subtraction of this background is a major challenge for the extraction of spectra and morphology of gamma-ray sources. Aims: The unprecedented sensitivity of the new generation of ground based very-high-energy gamma-ray experiments such as HESS has lead to the discovery of

D. Berge; S. Funk; J. Hinton

2007-01-01

168

On Gamma-Ray Bursts  

Microsoft Academic Search

We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high

Remo Ruffini; M. G. Bernardini; C. L. Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; M. G. Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; J. A. Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

2008-01-01

169

Cosmic gamma-ray bursts  

Microsoft Academic Search

The results of the observation of cosmic gamma-ray bursts are discussed and available theoretical models are presented. Emphasis is placed on a cosmological model in which a gamma burst results from a powerful (? 10511053 erg) and very short ( ?10 100 s) energy release which occurs in a compact ( ? 106107 cm) region and gives rise to a

Konstantin A Postnov

1999-01-01

170

The Compton Gamma Ray Observatory  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than

N. Gehrels; E. Chipman; D. A. Kniffen

1993-01-01

171

Gamma-ray camera flyby  

SciTech Connect

Animation based on an actual classroom demonstration of the prototype CCI-2 gamma-ray camera's ability to image a hidden radioactive source, a cesium-137 line source, in three dimensions. For more information see http://newscenter.lbl.gov/feature-stories/2010/06/02/applied-nuclear-physics/.

None

2010-01-01

172

The Gamma-ray Universe through Fermi  

NASA Technical Reports Server (NTRS)

Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Thompson, David J.

2012-01-01

173

Advances in gamma-ray line astronomy  

NASA Technical Reports Server (NTRS)

Gamma ray line observations of solar flares, gamma ray transients, and the galactic center are reviewed and interpreted. Prospects of future line detections are discussed. Previously announced in STAR as N82-27200

Ramaty, R.; Lingenfelter, R. E.

1983-01-01

174

Diagnosing ICF gamma-ray physics  

SciTech Connect

Gamma rays produced in an ICF environment open up a host of physics opportunities we are just beginning to explore. A branch of the DT fusion reaction, with a branching ratio on the order of 2e-5 {gamma}/n, produces 16.7 MeV {gamma}-rays. These {gamma}-rays provide a direct measure of fusion reaction rate (unlike x-rays) without being compromised by Doppler spreading (unlike neutrons). Reaction-rate history measurements, such as nuclear bang time and burn width, are fundamental quantities that will be used to optimize ignition on the National Ignition Facility (NIF). Gas Cherenkov Detectors (GCD) that convert fusion {gamma}-rays to UV/visible Cherenkov photons for collection by fast optical recording systems established their usefulness in illuminating ICF physics in several experimental campaigns at OMEGA. Demonstrated absolute timing calibrations allow bang time measurements with accuracy better than 30 ps. System impulse response better than 95 ps fwhm have been made possible by the combination of low temporal dispersion GCDs, ultra-fast microchannel-plate photomultiplier tubes (PMT), and high-bandwidth Mach Zehnder fiber optic data links and digitizers, resulting in burn width measurement accuracy better than 10ps. Inherent variable energy-thresholding capability allows use of GCDs as {gamma}-ray spectrometers to explore other interesting nuclear processes. Recent measurements of the 4.44 MeV {sup 12}C(n,n{prime}) {gamma}-rays produced as 14.1 MeV DT fusion neutrons pass through plastic capsules is paving the way for a new CH ablator areal density measurement. Insertion of various neutron target materials near target chamber center (TCC) producing secondary, neutron-induced {gamma}y-rays are being used to study other nuclear interactions and as in-situ sources to calibrate detector response and DT branching ratio. NIF Gamma Reaction History (GRH) diagnostics, based on the GCD concept, are now being developed based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF-specific logistics, requirements and extreme radiation environment. Implementation will occur in two phases: (1) four PMT-based channels mounted to the outside of the target chamber at {approx}6m from TCC (GRH-6m) for the 3e13-3e16 DT neutron yield range expected during the early ignition-tuning campaigns; and (2) several channels located just inside the target bay shield wall at 15 m from TCC (GRH-15m) with optical paths leading through the cement shield wall to well-shielded streak cameras and PMTs for the 1e16-1e20 yield range expected during the DT ignition campaign. Multiple channels at each phase will allow for increased redundancy, reliability, accuracy and flexibility. This suite of diagnostics will make possible exploration of interesting {gamma}-ray physics well beyond the ignition campaign.

Herrmann, Hans W [Los Alamos National Laboratory; Kim, Y H [Los Alamos National Laboratory; Mc Evoy, A [Los Alamos National Laboratory; Young, C S [Los Alamos National Laboratory; Mack, J M [Los Alamos National Laboratory; Hoffman, N [Los Alamos National Laboratory; Wilson, D C [Los Alamos National Laboratory; Langenbrunner, J R [Los Alamos National Laboratory; Evans, S [Los Alamos National Laboratory; Sedillo, T [Los Alamos National Laboratory; Batha, S H [Los Alamos National Laboratory; Dauffy, L [LLNL; Stoeffl, W [LLNL; Malone, R [Los Alamos National Laboratory; Kaufman, M I [Los Alamos National Laboratory; Cox, B C [Los Alamos National Laboratory; Tunnel, T W [Los Alamos National Laboratory; Miller, E K [NSTEC/SB; Ali, Z A [NSREC/LIVERMORE; Horsfield, C J [AWE; Rubery, M [AWE

2010-01-01

175

Extreme Terrestrial Gamma ray Events  

NASA Astrophysics Data System (ADS)

Terrestrial gamma ray flashes were first discovered by the Compton GRO observatory and such event have been observed later on-board Rhessi satellite and more recently by the Fermi and Agile missions. These events are believed to be associated with the thunderstorm activity in the lower atmosphere. When observed from the satellite instruments, the observed time structure. Shows short milliseconds bursts probably due to lightning discharges , however an other type of long bursts with a duration of a few seconds to a few minutes have been observed only in the lower atmosphere. Such behaviour is natural as the upward moving photons go through a large atmospheric depth several 100 gms which will affect both the time structure and the spectral nature as the thunderstorms normally originate only in the lower troposphere just above the convective boundary layer. We report the observations of extreme terrestrial gamma ray events with time duration ~150-250 min observed during the thunderstorm activity in Hyderabad South, India. At 17.3o lat. and 78.6o long., Hyderabad is located in the convergence zone with high level of thunderstorm activity during the monsoon period. Spectral data suggest a continuum flux of the gamma ray from 100 keV to 10 MeV for hours. Temporal characteristics studied with time resolution of 100 microsec do not show any excess power density at any frequency. The data suggest that unlike gamma ray flashes which are generated just during the lightening flash, large electric field disturbances during long thunderstorm activity may lead to large flux of accelerated particles, which emit continuum gamma rays flux.

Manchanda, R. K.; Kamble, Nilima

2012-07-01

176

Portable compton gamma-ray detection system  

DOEpatents

A Compton scattered gamma-ray detector system. The system comprises a gamma-ray spectrometer and an annular array of individual scintillators. The scintillators are positioned so that they are arrayed around the gamma-ray spectrometer. The annular array of individual scintillators includes a first scintillator. A radiation shield is positioned around the first scintillator. A multi-channel analyzer is operatively connected to the gamma-ray spectrometer and the annular array of individual scintillators.

Rowland, Mark S. (Alamo, CA); Oldaker, Mark E. (Pleasanton, CA)

2008-03-04

177

Light Curves of Swift Gamma Ray Bursts  

E-print Network

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short - long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars.

Paolo Cea

2006-09-22

178

Gamma-ray astronomy at high energies  

Microsoft Academic Search

Progress in high-energy gamma-ray astronomy has depended upon the development of sophisticated detectors and analysis techniques. Observations in this decade using space-based and ground-based detectors have observed gamma-ray emission from a variety of sources. For the first time a consistent picture of the gamma-ray sky has emerged. This article describes the detection techniques in gamma-ray astronomy, the nature of the

C. M. Hoffman; C. Sinnis; P. Fleury; M. Punch

1999-01-01

179

Monte Carlo calibration of the SMM gamma ray spectrometer for high energy gamma rays and neutrons  

Microsoft Academic Search

The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission spacecraft was primarily designed and calibrated for nuclear gamma ray line measurements, but also has a high energy mode which allows the detection of gamma rays at energies above 10 MeV and solar neutrons above 20 MeV. The GRS response has been extrapolated until now for high energy gamma rays

J. F. Cooper; C. Reppin; D. J. Forrest; E. L. Chupp; G. H. Share; R. L. Kinzer

1985-01-01

180

Gamma ray spectroscopy in astrophysics. [conferences  

NASA Technical Reports Server (NTRS)

Experimental and theoretical aspects of gamma ray spectroscopy in high energy astrophysics are discussed. Line spectra from solar, stellar, planetary, and cosmic gamma rays are examined as well as HEAO investigations, the prospects of a gamma ray observatory, and follow-on X-ray experiments in space.

Cline, T. L. (editor); Ramaty, R. (editor)

1978-01-01

181

Gamma ray astrophysics. [emphasizing processes and absorption  

NASA Technical Reports Server (NTRS)

Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

Stecker, F. W.

1974-01-01

182

Nuclear gamma rays from energetic particle interactions  

NASA Technical Reports Server (NTRS)

Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1978-01-01

183

Gamma-ray signatures of classical novae  

E-print Network

The role of classical novae as potential gamma-ray emitters is reviewed, on the basis of theoretical models of the gamma-ray emission from different nova types. The interpretation of the up to now negative results of the gamma-ray observations of novae, as well as the prospects for detectability with future instruments (specially onboard INTEGRAL) are also discussed.

M. Hernanz; J. Gomez-Gomar; J. Jose

2001-09-06

184

Monte Carlo approach to sequential {gamma}-ray emission from fission fragments  

SciTech Connect

A Monte Carlo simulation of the fission fragment statistical decay based on a sequential neutron followed by {gamma}-ray emission is proposed. The {gamma}-ray energy spectrum is calculated as a function of the mass of the fission fragments and integrated over the whole mass distribution. The prompt {gamma}-ray multiplicity distribution, both the average number of emitted {gamma} rays and the average {gamma}-ray energy as a function of the mass of the fission fragments [respectively, N{sub {gamma}}(A) and <{epsilon}{sub {gamma}}>(A)], are also assessed. The {gamma}-{gamma} correlations emitted from both light and heavy fragments are calculated as well as correlations between {gamma}-ray energies. Results are reported for the neutron-induced fission of {sup 235}U (at 0.53 MeV neutron energy) and for the spontaneous fission of {sup 252}Cf.

Lemaire, S.; Talou, P.; Kawano, T.; Madland, D.G. [Theoretical Division, Nuclear Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Chadwick, M.B. [PADNWP, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-01-15

185

A history of gamma ray bursts and other astronomical conundrums  

E-print Network

line between X-ray and gamma ray astronomy has nothing to doray astronomers and gamma-ray astronomy is done by gamma rayGamma Ray Bursts and Other Astronomical Conundrums Virginia Trimble Department of Physics & Astronomy

Trimble, V

2006-01-01

186

Fission prompt gamma-ray multiplicity distribution measurements and simulations at DANCE  

SciTech Connect

The nearly energy independence of the DANCE efficiency and multiplicity response to {gamma} rays makes it possible to measure the prompt {gamma}-ray multiplicity distribution in fission. We demonstrate this unique capability of DANCE through the comparison of {gamma}-ray energy and multiplicity distribution between the measurement and numerical simulation for three radioactive sources {sup 22}Na, {sup 60}Co, and {sup 88}Y. The prospect for measuring the {gamma}-ray multiplicity distribution for both spontaneous and neutron-induced fission is discussed.

Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

2010-08-24

187

Differential Radiosensitivity Phenotypes of DNA-PKcs Mutations Affecting NHEJ and HRR Systems following Irradiation with Gamma-Rays or Very Low Fluences of Alpha Particles  

PubMed Central

We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate ? irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE) production by very low fluences of ?-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR) mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by ?-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of ?-particles is resulted from bystander effects in cells not traversed by ?-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ) and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component. PMID:24714417

Little, John B.; Kato, Takamitsu A.; Shih, Hung-Ying; Xie, Xian-Jin; Wilson Jr., Paul F.; Brogan, John R.; Kurimasa, Akihiro; Chen, David J.; Bedford, Joel S.; Chen, Benjamin P. C.

2014-01-01

188

Compton Gamma Ray Observatory Guest Investigator Program  

NASA Technical Reports Server (NTRS)

This paper presents a final report for the Compton Gamma Ray Observatory Guest Investigator Program from 06/01/91-07/31/97. The topics include: 1) Solar Flare Neutron Spectra and Accelerated Ions; 2) Gamma Ray Lines From The Orion Complex; 3) Implications of Nuclear Line Emission From The Orion Complex; 4) Possible Sites of Nuclear Line Emission From Massive OB Associations; 5) Gamma-Ray Burst Repitition and BATSE Position Uncertainties; 6) Effects of Compton Scattering on BATSE Gamma-Ray Burst Spectra; and 7) Selection Biases on the Spectral and Temporal Distribution of Gamma Ray Bursts.

Lingenfelter, Richard E.

1997-01-01

189

Gamma rays from globular clusters  

NASA Technical Reports Server (NTRS)

Globular clusters are known to contain a relatively large number of pulsars whose individual and collective emission in the X-ray and gamma-ray energy bands may be detectable by the instruments on board the Compton Gamma-Ray Observatory (CGRO), ROSAT, and possibly SIGMA. We discuss the several types of high-energy emission expected from isolated and interacting binary pulsars in globular clusters. Individual or collective high-energy emission from isolated pulsars is expected to be too low to be detected with current instruments. However, a class of high-luminosity hidden millisecond pulsars enshrouded in the evaporating material from irradiated companion stars can produce unpulsed shock emission detectable by the high-sensitivity instruments of ROSAT and CGRO. Establishing upper limits of high-energy emission from globular clusters will be valuable in constraining models for the formation of cluster millisecond pulsars.

Tavani, Marco

1993-01-01

190

High-energy gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

The subject of gamma-ray astronomy is discussed with emphasis on celestial gamma rays with energies in excess of 10 MeV. Early observations of such gamma rays are reviewed, a gamma-ray spark-chamber telescope is described together with a gas Cerenkov-counter telescope, and the gamma-ray sky is delineated. It is shown that the diffuse high-energy gamma radiation from the galactic plane probably results primarily from cosmic-ray interactions with interstellar matter. Mechanisms for gamma-ray production are identified, and it is noted that the general galactic radiation may prove to be of great value in studies of galactic structure. Possible sources are considered for the diffuse celestial radiation, and discrete sources are described, including the Crab pulsar, the Vela remnant, the Cygnus region, and Gould's Belt. Future developments in gamma-ray astronomy are considered.

Fichtel, C.; Kniffen, D.; Greisen, K.

1975-01-01

191

Gamma-ray burst afterglows  

E-print Network

Extended, fading emissions in multi-wavelength are observed following Gamma-ray bursts (GRBs). Recent broad-band observational campaigns led by the Swift Observatory reveal rich features of these GRB afterglows. Here we review the latest observational progress and discuss the theoretical implications for understanding the central engine, composition, and geometric configuration of GRB jets, as well as their interactions with the ambient medium.

Bing Zhang

2007-01-10

192

STS-37: Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

This NASA Kennedy Space Center (KSC) video release presents footage of pre-flight activities involving the STS-37 primary payload, the Gamma Ray Observatory (GRO). The GRO is shown being removed from the transport aircraft to one of the runways at Kennedy. Other footage includes Kennedy work crews moving the GRO into position as well as discussions between the STS-37 astronauts and the work crews regarding GRO operation.

1991-01-01

193

One-dimensional gamma-ray shielding calculations for the EBT-P  

Microsoft Academic Search

Due to the expected large loss of electrons on the magnetic coil assemblies and other components of the proposed EBT-P plasma device, the induced gamma-ray field from bremsstrahlung will be very intense. These gamma rays will yield increased heating loads on the superconducting cryogenic coils as well as produce a significant biological hazard. In this summary, the results from a

R. A. Lillie; T. A. Gabriel; B. L. Bishop; V. C. Baker

1980-01-01

194

Measurement of pulmonary edema in intact dogs by transthoracic gamma-ray attenuation  

Microsoft Academic Search

Attenuation of the 122 keV gamma rays of cobalt-57 across the thorax of anesthetized dogs was evaluated as a method for following the time course of lung water changes in acute pulmonary edema induced by either increased microvascular permeability or increased microvascular hydrostatic pressure. The gamma rays traversed the thorax centered on the seventh rib laterally where the lung mass

D. S. Simon; J. F. Murray; N. C. Staub

1979-01-01

195

Gamma-ray astronomy with H.E.S.S  

NASA Astrophysics Data System (ADS)

H.E.S.S. is an array of imaging atmospheric Cherenkov telescopes for ground based gamma-ray astronomy. Consisting of four telescopes with 107 m2 mirror area each, operational since 10 years, and a new 600 m2 telescope in the center of the array, it uses Cherenkov light emitted by gamma-ray induced particle showers in the atmosphere to investigate high-energy phenomena in the universe. H.E.S.S. has discovered of the order of 60% of all very-high energy gamma-ray sources. Recent results cover physics topics like the acceleration of cosmic rays in supernova remnants, the interaction of cosmic rays with molecular clouds, or the acceleration and the emission processes in binary systems. Other topics covered are the physics of relativistic flows in pulsar wind nebulae and extra-galactic objects like AGN or radio galaxies as well as exotic physics like the search for axions.

Frster, A.

2014-12-01

196

Pulsed neutron gamma-ray logging in archaeological site survey  

NASA Astrophysics Data System (ADS)

An archaeological survey method based on neutron gamma-ray logging is described. The method relies on the measurement of capture gamma radiation induced by neutron irradiation from a pulsed generator. This technique provides elemental information on the irradiated zone by spectroscopic analysis of the gamma-ray data. This approach has been studied with Geant4 Monte Carlo simulations. In particular, irradiation volume for a deuterium-deuterium and deuterium-tritium (D-T) neutron generator and sampling volume for the D-T source were estimated. In addition, a neutron log response, which illustrates the capability of the neutron tool to localize artifacts lying beneath the surface, is shown.

Miceli, A.; Festa, G.; Gorini, G.; Senesi, R.; Andreani, C.

2013-12-01

197

Gamma-ray astronomy: Nuclear transition region  

NASA Technical Reports Server (NTRS)

This monograph reviews the major theoretical and experimental efforts made during the past 12 years in gamma-ray astronomy over the energy range from 10 keV to about 100 MeV, where nuclear-transition lines are expected. Early attempts to detect celestial gamma rays are recounted, mechanisms of gamma-ray line and continuum production are examined, and formulas giving the various possible differential gamma-ray spectral shapes are provided. Predicted fluxes are discussed for solar gamma rays as well as for gamma emission from supernova remnants, supernovae, neutron stars, flare stars, the galactic core and disk, black holes, and diffuse sources. Gamma-ray interactions with matter are analyzed, particularly the photoelectric effect, Compton scattering from free electrons, and pair production in nuclear fields. Significant results are summarized for observations of gamma rays from the sun as well as from point and extended sources within and beyond the Galaxy, including diffuse fluxes and transient gamma-ray bursts. Factors pertaining to the design of gamma-ray astronomy experiments are considered, especially detector background limitations, gamma-ray production within instruments, and present-day detection methods.

Chupp, E. L.

1976-01-01

198

Space instrumentation for gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

The decade of the 1990s has witnessed a renaissance in the field of gamma-ray astronomy. The seminal event was the launch of the Compton Gamma-Ray Observatory (CGRO) in April 1991. There have been a flood of major discoveries from CGRO including breakthroughs in gamma-ray bursts, annihilation radiation, and blazars. The Italian SAX satellite was launched in April 1996. Although not primarily a gamma-ray mission, it has added a new dimension to our understanding of gamma-ray bursts. Along with these new discoveries a firm groundwork has been laid for missions and new technology development that should maintain a healthy and vigorous field throughout most of the next decade. These include the ESA INTEGRAL mission (INTErnational Gamma-Ray Astrophysics Laboratory, to be launched in mid-2001) and the NASA GLAST mission (Gamma-Ray Large Area Space Telescope) with a likely launch in the middle of the next decade. These two missions will extend the observational capabilities well beyond those of CGRO. New technologies (to gamma-ray astronomy), such as cooled germanium detectors, silicon strip detectors, and CdTe detectors are planned for these new missions. Additional promising new technologies such as CdZnTe strip detectors, scintillator fibers, and a gamma-ray lens for future gamma-ray astronomy missions are under development in laboratories around the world.

Teegarden, B. J.

1999-02-01

199

Cosmic Rays and Gamma Ray Bursts From Microblazars  

E-print Network

Highly relativistic jets from merger and accretion induced collapse of compact stellar objects, which may produce the cosmological gamma ray bursts (GRBs), are also very efficient and powerful cosmic ray accelerators. The expected luminosity, energy spectrum and chemical composition of cosmic rays from Galactic GRBs, most of which do not point in our direction, can explain the observed properties of Galactic cosmic rays.

Arnon Dar

1998-09-13

200

Can Fireball or Firecone Models Explain Gamma Ray Bursts?  

E-print Network

The observed afterglows of gamma ray bursts, in particular that of GRB 970228 six months later, seem to rule out relativistic fireballs and relativistic firecones driven by merger or accretion induced collapse of compact stellar objects in galaxies as the origin of GRBs. GRBs can be produced by superluminal jets from such events.

Arnon Dar

1998-01-04

201

Gamma-rays from synchrotron pair cascades in blazars?  

Microsoft Academic Search

The possibility of gamma-ray production in blazars as a result of synchrotron e^+\\/- pair cascade initiated by extremely high energy curvature photons in the disc\\/jet magnetic field is considered. It is assumed that the curvature radiation is produced by particles accelerated in the DC electric fields which are in turn induced during a reconnection process of the magnetic field in

W. Bednarek

1997-01-01

202

Relative Biological Effectiveness (RBE) of 131I Radiation Relative to 60Co Gamma Rays  

PubMed Central

Objective: To assess relative biological effectiveness (RBE) of 131I radiation relative to 60Co gamma rays in glioblastoma spheroid cells. Materials and Methods: : In this experimental study, glioblastoma spheroid cells were exposed to 131I radiation and 60Co gamma rays. Radiation induced DNA damage was evaluated by alkaline comet assay. Samples of spheroid cells were treated by radiation from 131I for four different periods of time to find the dose-response equation. Spheroid cells were also exposed by 200 cGy of 60Co gamma rays as reference radiation to induce DNA damage as endpoint. Results: Resulted RBE of 131I radiation relative to 60Co gamma rays in 100 m giloblastoma spheroid cells was equal to 1.16. Conclusion: The finding of this study suggests that 131I photons and electrons can be more effective than 60Co gamma rays to produce DNA damage in glioblastoma spheroid cells. PMID:24027663

Neshasteh-Riz, Ali; Mahmoud Pashazadeh, Ali; Mahdavi, Seyed Rabie

2013-01-01

203

Effects of air--density perturbations on the transport of gamma rays produced by point gamma-ray sources  

Microsoft Academic Search

A series of MORSE Monte Carlo calculations were performed to determine ; the effect that changes in the air density produced by one weapon detonation ; would have on the transpont of gamma-ray radiation produced by a second weapon ; detonated about one second later. The response of interest was the ionization ; that would be induced in silicon by

B. J. McGregor; F. R. Mynatt

1973-01-01

204

Quasars, blazars, and gamma rays  

NASA Technical Reports Server (NTRS)

The paper discusses the extragalactic sources that have been discovered with the Energetic Gamma Ray Experiment Telescope. All of the sources demonstrate evidence of blazar properties at other wavelengths, including high optical polarization, extreme optical variability, flat-spectrum radio emission associated with a compact core, and apparent superluminal motion. These properties are believed to be produced by those few rare extragalactic quasars and radio galaxies that are favorably aligned to make it possible to observe almost directly down a relativistically outflowing jet of matter expelled from a supermassive black hole.

Dermer, Charles D.; Schlickeiser, Reinhard

1992-01-01

205

High Redshift Gamma Ray Bursts  

NASA Technical Reports Server (NTRS)

The Swift Observatory has been detecting 100 gamma-ray bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from 1 minute after the burst, continuing for days. GRBs are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=9.4 giving information on metallicity, star formation rate and reionization. The talk will present the latest results.

Gehrels, Neil

2012-01-01

206

Gamma-ray burst reprocessing  

NASA Technical Reports Server (NTRS)

A review of three theoretical models for the generation of transient optical emission thought to accompany the gamma-ray bursts is presented. The physics of reprocessing by Compton-heated electrons in the magnetosphere of a highly magnetized neutron star, the surface layers of a companion star, and an accretion disk are discussed. The spectral shapes, time scales, and arrival time delays between low and high energy photons predicted by the models are compared. These predictions are so different that broad band monitoring could be used to indicate which of the three scenarios (if any) is correct.

Melia, Fulvio

1988-01-01

207

Gamma-Ray Attenuation Coefficient Measurements  

Microsoft Academic Search

In an earlier paper, published by the authors elsewhere, it was shown that for 661.6-keV gamma rays the measurements of gamma-ray attenuation coefficients would greatly improve if one uses the counting sequence of Conner et al. together with a new criterion mut<1, where mu is the gamma-ray attenuation coefficient and t is the thickness of the sample. In this paper

S. Gopal; B. Sanjeevaiah

1973-01-01

208

Gamma-Ray Astronomy Technology Needs  

NASA Technical Reports Server (NTRS)

In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophysical understanding in many ways. We present an overview of current and future planned space y-ray missions and discussion technology needs for- the next generation of space gamma-ray instruments.

Gehrels, N.; Cannizzo, J. K.

2012-01-01

209

The physics of gamma-ray bursts  

Microsoft Academic Search

Gamma-ray bursts (GRB's), short and intense pulses of low-energy gamma rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding

Tsvi Piran

2004-01-01

210

Black Stars and Gamma Ray Bursts  

E-print Network

Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed ``black stars''. Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

Tanmay Vachaspati

2007-06-08

211

Space instrumentation for gamma-ray astronomy  

Microsoft Academic Search

The decade of the 1990s has witnessed a renaissance in the field of gamma-ray astronomy. The seminal event was the launch of the Compton Gamma-Ray Observatory (CGRO) in April 1991. There have been a flood of major discoveries from CGRO including breakthroughs in gamma-ray bursts, annihilation radiation, and blazars. The Italian SAX satellite was launched in April 1996. Although not

B. J Teegarden

1999-01-01

212

Galaxies and gamma-ray astronomy  

Microsoft Academic Search

Comparisons between the recently measured X-ray spectra of active galaxies, the intensity upper limits to the ..gamma..-ray emission above 35 MeV from the same objects obtained from data from SAS 2, and other ..gamma..-ray data are used to address the nature of the high-energy spectra of several types of active galaxies, their contribution to the measured diffuse ..gamma..-ray emission between

G. F. Bignami; C. E. Fichtel; R. C. Hartman; D. J. Thompson

1979-01-01

213

Very High Energy Gamma-Ray Astronomy  

Microsoft Academic Search

We present a review of the current status of very high energy gamma-ray astronomy. The development of the atmospheric Cerenkov imaging technique for ground-based gamma-ray astronomy has led to a rapid growth in the number of observatories. The detection of TeV gamma-rays from active galactic nuclei was unexpected and is providing new insights into the emission mechanisms in the jets.

Michael Catanese; Trevor C. Weekes

1999-01-01

214

Some aspects of gamma-ray astronomy  

Microsoft Academic Search

The present state of gamma-ray astronomy is reviewed. The basic understanding of the processes by which gamma radiation is generated and absorbed is outlined. The basic observational results in various gamma-ray energy ranges are presented. The nature of the gamma bursts, the radiation source at the center of the local galaxy, etc., are discussed for the range of soft gamma-ray

Vitalii L Ginzburg

1989-01-01

215

GRI: The Gamma-Ray Imager mission  

NASA Astrophysics Data System (ADS)

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe While at lower wavebands the observed emission is generally dominated by thermal processes the gamma-ray sky provides us with a view on the non-thermal Universe Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood and nuclear reactions are synthesizing the basic constituents of our world Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime With the INTEGRAL observatory ESA has provided a unique tool to the astronomical community and has put Europe in the lead in the field of gamma-ray astronomy INTEGRAL provides an unprecedented survey of the soft gamma-ray sky revealing hundreds of sources new classes of objects extraordinary views of antimatter annihilation in our Galaxy and fingerprints of recent nucleosynthesis processes While INTEGRAL has provided the global overview over the soft gamma-ray sky there is a growing need to perform deeper more focused investigations of gamma-ray sources In soft X-rays a comparable step was taken going from the Einstein satellite to the XMM Newton observatory Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission providing major improvements compared to past missions regarding sensitivity and angular resolution Such a

Kndlseder, J.; Gri Consortium

216

The Mystery of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts remain one of the greatest mysteries in astrophysics. Observations of gamma-ray bursts made by the BATSE experiment on the Compton Gamma-Ray Observatory will be described. Most workers in the field now believe that they originate from cosmological distances. This view has been reinforced by observations this year of several optical afterglow counterparts to gamma-ray bursts. A summary of these recent discoveries will be presented, along with their implications for models of the burst emission mechanism and the energy source of the bursts.

Fishman, Gerald J.

2004-01-01

217

Hard gamma ray emission from blazars  

NASA Technical Reports Server (NTRS)

The gamma-ray emission expected from compact extragalactic sources of nonthermal radiation is examined. The highly variable objects in this class should produce copious amounts of self-Compton gamma-rays in the compact relativistic jet. This is shown to be a likely interpretation of the hard gamma-ray emission recently detected from the quasar 3C 279 during a period of strong nonthermal flaring at lower frequencies. Ways of discriminating between the self-Compton model and other possible gamma-ray emission mechanisms are discussed.

Marscher, Alan P.; Bloom, Steven D.

1992-01-01

218

Radiation-induced mutation at minisatellite loci  

SciTech Connect

We are studying the radiation-induced increase of mutation rate in minisatellite loci in mice and humans. Minisatellite mutations were scored by multilocus DNA fingerprint analysis in the progeny of {gamma}-irradiated and non-irradiated mice. The frequency of mutation in offspring of irradiated males was 1.7 higher that in the control group. Germline mutation at human minisatellite loci was studied among children born in heavily polluted areas of the Mogilev district of Belarus after the Chernobyl accident and in a control population. The frequency of mutation assayed both by DNA fingerprinting and by eight single locus probes was found to be two times higher in the exposed families than in the control group. Furthermore, mutation rate was correlated with the parental radiation dose for chronic exposure {sup 137}Cs, consistent with radiation-induction of germline mutation. The potential use of minisatellites in monitoring germline mutation in humans will be discussed.

Dubrova, Y.E. [Univ. of Leicester (United Kingdom)]|[Vavilov Institute of General Genetics, Moscow (Russian Federation); Nesterov, V.N.; Krouchinsky, N.G. [Research Institute for Radiation Medicine, Mogilev (Belarus)] [and others

1997-10-01

219

Origin of Gamma Ray Bursters  

NASA Astrophysics Data System (ADS)

Major advances have been made in the field of gamma-ray bursts in the last two years. The successful discovery of X-ray, optical and radio afterglows has made possible the identification of host galaxies at cosmological distances. The energy release inferred in these outbursts place them among the most energetic and violent events in the Universe. They are thought to be the outcome of a cataclysmic stellar collapse or compact stellar merger, leading to a relativistically expanding fireball, in which particles are accelerated at shocks and produce nonthermal radiation. The substantial agreement between observations and the theoretical predictions of the standard fireball shock model provides confirmation of the basic aspects of this scenario. New issues being raised by the most recent observations concern the amount and the nature of the collimation of the outflow and its implications for the energetics, the production of prompt bright flashes at wavelengths much longer than gamma-rays, the time structure of the afterglow, its dependence on the central engine or progenitor system behavior, and the role of the environment on the evolution of the afterglow.

Mszros, P.

220

Gamma-ray burst models.  

PubMed

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts. PMID:17293332

King, Andrew

2007-05-15

221

The Correlation between Gamma-ray and Radio Emissions in gamma-ray Loud Blazars  

Microsoft Academic Search

We collect 119 gamma-ray-loud blazars (97 flat spectrum radio quasars (FSRQs) and 22 BL Lacertae objects (BL Lacs)), and investigate possible correlations between their gamma-ray emission (maximum, minimum and average values) at 1 GeV and the radio emission at 8.4 GHz. Our main results are as follows. For the lower state gamma-ray data, there is no correlation between the gamma-ray

Jiang-He Yang; Jun-Hui Fan

2005-01-01

222

The status of low-energy gamma-ray astronomy and the Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

A brief sketch of the objectives and status of the various subdisciplines in gamma-ray astronomy (below 10 GeV) are presented. The Gamma-Ray Observatory planned for launch in 1988 is described. This NASA observatory and several planned French-Soviet spacecraft are expected to elevate gamma-ray astronomy into a mature observational science for the Space Station era.

Fishman, G. J.

1985-01-01

223

Observation of entrance channel effects in compound nucleus formation with high energy. gamma. -rays  

SciTech Connect

We investigated entrance channel effects in the decay of excited {sup 160}Er and {sup 164}Yb, formed with {sup 16}O and {sup 64}Ni beams by measuring high energy (5--25 MeV) {gamma}-ray spectra. Gamma rays from the decay of the giant dipole resonance (GDR) built on highly excited states provide a good probe to study these effects, since the {gamma} rays are emitted in the early stages of the reaction. The {gamma}-ray spectra measured in the {sup 16}O-induced reactions show the typical GDR bump whereas the {gamma}-ray spectra from the more symmetric entrance channels show dramatically different shape. 22 refs., 5 figs., 2 tabs.

Thoennessen, M.; Beene, J.R.; Auble, R.L.; Bertrand, F.E.; Baktash, C.; Halbert, M.L.; Horen, D.J.; Ludemann, C.A. (Oak Ridge National Lab., TN (USA)); Sarantites, D.G.; Stracener, D.W. (Washington Univ., St. Louis, MO (USA)); Spang, W. (Kernforschungsanlage Juelich GmbH (Germany, F.R))

1990-01-01

224

Measurement of $gamma$-ray attenuation coefficients  

Microsoft Academic Search

Gamma-ray attenuation coefficients have been determined for aluminum, ; copper, tin, platinum and lead (elements with Z between 13 and 82) using gamma -; rays with energies between 295 and 2440 keV from a sealed Ra-226 source. A ; lithium-drifted germanium detector was employed without collimation or shielding. ; The average standard error of the experimental results was 1%. (auth)

Christmas

1974-01-01

225

The Compton Gamma Ray Observatory: mission status  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and

N. Gehrels; E. Chipman; D. A. Kniffen

1994-01-01

226

Temperature distribution in gamma-ray shielding  

Microsoft Academic Search

Analytical expressions are obtained for the temperature distributions in gamma ray shielding for isotropic and unidirectional beams with boundary conditions of the third kind. These are solved numerically for concrete shielding, and the effects of shield thickness, gamma-ray scattering, boundary conditions and beam geometry on the temperature distribution profile are examined.

D. P. Osanov

1965-01-01

227

Supernovae as sources of gamma rays  

NASA Technical Reports Server (NTRS)

Most supernovae are profoundly radioactive and the Gamma Ray Observatory is an ideal instrument for detecting their unique gamma ray line and X-ray signatures. How the observation of these hard photons can be used to do supernova science will be addressed, with particular emphasis being placed on Type Ia explosions and nearby events.

Burrows, Adam

1992-01-01

228

Concept of new gamma ray detector  

E-print Network

We present a concept of a new gamma ray detector in order to observe undetected TeV gamma ray background. We measure a track of an electron-positron pair made by a pair creation in a magnet. By using Si as a tracker in a magnetic field 3 T, an energy range is up to 10 TeV.

S. Osone

2004-03-15

229

Gamma Ray Burst All-Sky Spectrometer  

Microsoft Academic Search

The Gamma Ray Burst All-Sky Spectrometer Experiment (GASE) is designed to detect radio emission from gamma ray bursts (GRB's). Radio emission from GRB's could help us better understand the plasma physics of the blast and might also help us measure dark energy. GASE uses short-baseline interferometry with eight dipole antennas located at the MIT Haystack Observatory. These antennas measure the

Arielle Steger

2011-01-01

230

Very high-energy gamma rays from gamma-ray bursts.  

PubMed

Very high-energy (VHE) gamma-ray astronomy has undergone a transformation in the last few years, with telescopes of unprecedented sensitivity having greatly expanded the source catalogue. Such progress makes the detection of a gamma-ray burst at the highest energies much more likely than previously. This paper describes the facilities currently operating and their chances for detecting gamma-ray bursts, and reviews predictions for VHE gamma-ray emission from gamma-ray bursts. Results to date are summarized. PMID:17293337

Chadwick, Paula M

2007-05-15

231

Atmospheric gamma-ray and neutron flashes  

SciTech Connect

Gamma-ray pulses are calculated from 2D numerical simulations of an upward atmospheric discharge in a self-consistent electric field using the multigroup approach to the kinetics of relativistic runaway electrons (REs). Computed {gamma}-ray numbers and spectra are consistent with those of terrestrial {gamma}-ray flashes (TGFs) observed aboard spacecrafts. The RE flux is concentrated mainly within the domain of the Blue Jet fluorescence. This confirms that exactly the domain adjacent to a thundercloud is the source of the observed {gamma}-ray flashes. The yield of photonuclear neutrons is calculated. One {gamma}-ray pulse generates {approx}10{sup 14}-10{sup 15} neutrons. The possibility of the direct deposition of REs to the detector readings and the origin of the lightning-advanced TGFs are discussed.

Babich, L. P., E-mail: babich@elph.vniief.ru; Kudryavtsev, A. Yu., E-mail: kay@sar.ru; Kudryavtseva, M. L., E-mail: kay@sar.ru; Kutsyk, I. M. [All-Russian Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center (Russian Federation)

2008-01-15

232

Characteristics of gamma-ray line flares  

NASA Technical Reports Server (NTRS)

Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

Bai, T.; Dennis, B.

1983-01-01

233

Instrumentation for gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

The current status of gamma-ray-telescope technology for ground, airborne, and space observations is surveyed and illustrated with drawings, diagrams, and graphs and tables of typical data. For the low- and medium-energy ranges, consideration is given to detectors and detector cooling systems, background-rejection methods, radiation damage, large-area detectors, gamma-ray imaging, data analysis, and the Compton-interaction region. Also discussed are the gamma-ray interaction process at high energies; multilevel automated spark-chamber gamma-ray telescopes; the Soviet Gamma-1 telescope; the EGRET instrument for the NASA Gamma-Ray Observatory; and Cerenkov, air-shower, and particle-detector instruments for the TeV and PeV ranges. Significant improvements in resolution and sensitivity are predicted for the near future.

Bertsch, David L.; Fichtel, Carl E.; Trombka, Jacob I.

1988-01-01

234

Future Missions for Gamma-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Gamma-ray astronomy has made great advances in recent years, due largely to the recently completed 9-year mission of the Compton Gamma Ray Observatory. In this talk I will give an overview of what advances we may expect in the near future, with particular emphasis on earth-orbiting missions scheduled for flight within the next 5 years. Two missions, the High Energy Transient Explorer and Swift, will provide important new information on the sources of gamma-ray bursts. The Gamma-Ray Large Area Space Telescope will investigate high energy emission from a wide variety of sources, including active galaxies and gamma-ray pulsars. The contributions of ground-based and multiwavelength observations will also be addressed.

Meegan, Charles; Rose, M. Franklin (Technical Monitor)

2000-01-01

235

Constraining axion by polarized prompt emission from gamma ray bursts  

E-print Network

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion-photon coupling. This constraint $\\g_{a\\gamma\\gamma}\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the axion mass $m_a=10^{-3} {\\rm eV}$ is competitive with the sensitivity of CAST and becomes even stronger for lower masses.

A. Rubbia; A. S. Sakharov

2007-08-21

236

Constraining axion by polarized prompt emission from gamma ray bursts  

NASA Astrophysics Data System (ADS)

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion photon coupling. This constraint g?2.210GeV calculated for the axion mass m=10eV is competitive with the sensitivity of CAST and becomes even stronger for lower masses.

Rubbia, Andr; Sakharov, Alexander

2008-02-01

237

Mutations induced in Drosophila during space flight.  

PubMed

To examine the possible effects of space radiation on living organisms, fruit flies Drosophila melanogaster were loaded on the US Space Shuttle Endeavour, and after the flight we have analyzed two types of mutations, sex-linked recessive lethal mutations induced in male reproductive cells and somatic mutations which give rise to morphological changes in hairs growing on the surface of wing epidermal cells. Wild type strains and a radiation-sensitive strain mei-41 were used. The frequencies of sex-linked recessive lethal mutations in flight groups were 2 and 3 times higher for wild type Canton-S and mei-41 strains, respectively, than those in ground control groups. By contrast, the frequencies of wing-hair somatic mutations differed little between flight and control groups. The possibility that the space environment causes mutations in certain types of cells such as male reproductive cells, is discussed. PMID:11541768

Ikenaga, M; Yoshikawa, I; Kojo, M; Ayaki, T; Ryo, H; Ishizaki, K; Kato, T; Yamamoto, H; Hara, R

1997-12-01

238

Modeling gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. This shell model code can be used to constrain broadband observations of GRB 090926A, which showed two flares in both the Swift UVOT and XRT bands. Using the prompt emission fluence to constrain the total energy contained in the blastwave, the internal shock model requires that Lorentz factors of the shells causing flares must be less than the Lorentz factor of the blastwave when the shells are ejected. Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from an external shock. We analyze four GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM), which have high quality lightcurves in both instrument energy bands. Using the MeV prompt emission (GBM) data, we can record the energy output from the central engine as a function of time. Assuming a constant radiative efficiency, we are able to track energy accumulation in the external shock using our internal/external shell model code and show that the late time lightcurves fit well within the external shock model, but the early time lightcurves are dominated by the internal shock component which has a shallow decay phase due to the initial pile-up of shells onto the blast wave.

Maxham, Amanda

239

Gamma-Ray Emission from Microquasars  

NASA Astrophysics Data System (ADS)

Microquasars, X-ray binary systems that generate relativistic jets, were discovered in our Galaxy in the last decade of the XXth century. Their name indicates that they are manifestations of the same physics as quasars but on a completely different scale. Parallel to this discovery, the EGRET instrument on board of the Compton Gamma Ray Observatory detected 271 point like gamma-ray sources 170 of which were not clearly identified with known objects. This marked the beginning of gamma-ray source population studies in the Galaxy. We present in this thesis models for gamma-ray production in microquasars with the aim to propose them as possible parent populations for different groups of EGRET unidentified sources. These models are developed for a variety of scenarios taking into account several possible combinations, i.e. black holes or neutron stars as the compact object, low mass or high mass stellar companions, as well as leptonic or hadronic gamma-ray production processes. We also show that the presented models for gamma-rays emitting microquasars can be used to explain observations from well known sources that are detected in energy ranges other than EGRET's. Finally, we include an alternative gamma-ray producing situation that does not involve microquasars but a specific unidentified EGRET source possibly linked to a magnetized accreting pulsar.

Kaufman Bernado, M. M.

2005-04-01

240

Gamma-ray Astronomy and GLAST  

NASA Technical Reports Server (NTRS)

The high energy gamma-ray (30 MeV to 100 GeV) sky has been relatively poorly studied. Most of our current knowledge comes from observations made by the Energetic Gamma Ray Experiment Telescope (EGRET) detector on the Compton Gamma Ray Observatory (CGRO), which revealed that the GeV gamma-ray sky is rich and vibrant. Studies of astrophysical objects at GeV energies are interesting for several reasons: The high energy gamma-rays are often produced by a different physical process than the better studied X-ray and optical emission, thus providing a unique information for understanding these sources. Production of such high-energy photons requires that charged particles are accelerated to equally high energies, or much greater. Thus gamma-ray astronomy is the study of extreme environments, with natural and fundamental connections to cosmic-ray and neutrino astrophysics. The launch of GLAST in 2008 will herald a watershed in our understanding of the high energy gamma-ray sky, providing dramatic improvements in sensitivity, angular resolution and energy range. GLAST will open a new avenue to study our Universe as well as to answer scientific questions EGRET observations have raised. In this talk, I will describe the GLAST instruments and capabilities and highlight some of the science we expect to address.

McEnery, Julie

2007-01-01

241

Future prospects for gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

As gamma-ray astronomy moves from the discovery to the exploratory phase, the promise of gamma-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the gamma-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, solar particle acceleration, the chemical composition of the planets and other bodies of the solar system, the structure of our galaxy, the origin and dynamic pressure effects of the cosmic rays, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the universe. The gamma-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the gamma-ray burst network, Solar Polar, and very high energy gamma-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.

Fichtel, C.

1981-01-01

242

Molecular markers of ionizing radiation-induced gene mutations in mammalian cells.  

PubMed

We have isolated independent Chinese hamster ovary (CHO) cell mutants at the hypoxanthine guanine phosphoribosyltransferase (hprt) locus from untreated, 60Co gamma-ray-exposed, and 212Bi alpha-exposed cells and identified the molecular changes underlying the mutation determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. Both the parental CHO-K1 cells and the X-ray-sensitive mutant xrs-5 cells were studied. The radiosensitive xrs-5 cells are defective in DNA double-strand break rejoining ability and in V(D)J recombination, which can be complemented by Ku protein. Of the 71 spontaneous CHO-K1 hprt mutants analyzed, 78% showed no change in exon number or size, 20% showed loss of one to eight exons (partial deletion), and 3% showed loss of all nine hprt exons (total deletion). Exposure of CHO-K1 cells to 6 Gy of gamma rays, which reduced survival levels to 10%, produced a high deletion spectrum with 45% of the 20 mutants analyzed showing a loss of one to eight exons and 30% showing total deletion. Exposure to an equitoxic dose of alpha radiation from 212Bi, a 220Rn daughter, resulted in a spectrum similar to the gamma-ray spectrum in that 75% of the 49 mutants analyzed were deletions. To alpha radiation, however, tended to produce larger intragenic deletions than gamma radiation. Of the 92 spontaneous xrs-5 mutants analyzed for deletions, 43% showed a loss of one to eight exons and 14% showed total deletion. This suggests that, in certain regions of the hprt gene, base alterations can be converted into large deletions and alteration in the Ku protein complex can influence this type of mutational process. Exposure to alpha radiation (10% survival) to xrs-5 cells resulted in a deletion spectrum similar to that seen in CHO-K1 cells. Of the 49 mutants analyzed, 43% showed on change in exon number or size, 16% showed a loss of one to eight exons, and 41% showed total deletion. While the defect in xrs-5 cells has a profound effect on spontaneous mutant spectra, this defect does not appear to affect alpha-induced mutation spectra. PMID:8781403

Hsie, A W; Porter, R C; Xu, Z; Yu, Y; Sun, J; Meltz, M L; Schwartz, J L

1996-05-01

243

Interpretations and implications of gamma ray lines from solar flares, the galactic center in gamma ray transients  

NASA Technical Reports Server (NTRS)

Observations and theories of astrophysical gamma ray line emission are reviewed and prospects for future observations by the spectroscopy experiments on the planned Gamma Ray Observatory are discussed.

Ramaty, R.; Lingenfelter, R. E.

1980-01-01

244

Ultra-sensitive in-beam gamma-ray spectroscopy for nuclear astrophysics at LUNA  

E-print Network

Ultra-sensitive in-beam gamma-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory gamma-ray background for E_\\gamma gamma-counting setups. The gamma-ray background induced by an incident alpha-beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.

Caciolli, A; Bemmerer, D; Bonetti, R; Broggini, C; Confortola, F; Corvisiero, P; Costantini, H; Elekes, Z; Formicola, A; Flp, Z; Gervino, G; Guglielmetti, A; Gustavino, C; Gyurky, Gy; Imbriani, G; Junker, M; Laubenstein, M; Lemut, A; Limata, B; Marta, M; Mazzocchi, C; Menegazzo, R; Prati, P; Roca, V; Rolfs, C; Alvarez, C Rossi; Somorjai, E; Straniero, O; Strieder, F; Terrasi, F; Trautvetter, H P

2008-01-01

245

Ultra-sensitive in-beam gamma-ray spectroscopy for nuclear astrophysics at LUNA  

E-print Network

Ultra-sensitive in-beam gamma-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory gamma-ray background for E_\\gamma gamma-counting setups. The gamma-ray background induced by an incident alpha-beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.

A. Caciolli; L. Agostino; D. Bemmerer; R. Bonetti; C. Broggini; F. Confortola; P. Corvisiero; H. Costantini; Z. Elekes; A. Formicola; Zs. Fulop; G. Gervino; A. Guglielmetti; C. Gustavino; Gy. Gyurky; G. Imbriani; M. Junker; M. Laubenstein; A. Lemut; B. Limata; M. Marta; C. Mazzocchi; R. Menegazzo; P. Prati; V. Roca; C. Rolfs; C. Rossi Alvarez; E. Somorjai; O. Straniero; F. Strieder; F. Terrasi; H. P. Trautvetter

2008-12-17

246

Extreme energy gamma rays and neutrinos and their observation in JEM-EUSO Mission  

SciTech Connect

The origin of the extreme energy cosmic rays (EECRs) is a mystery in the contemporary astrophysics. The JEM-EUSO Mission that mainly aims establishing astronomy using such EECRs with very high statistics will also have realistic capability of detecting gamma rays and neutrinos with approx10{sup 20} eV energies. Aboard the International Space Station, the JEM-EUSO mission also provides a unique platform to detect and study the air showers from extreme energy gamma rays and neutrinos. In the present paper, we discuss a part of results from our study on properties of gamma ray and neutrino induced air showers and the advantage for space-based observation.

Shinozaki, K. [RIKEN, Wako 351-0198 (Japan)

2010-06-01

247

First search for neutrinos in correlation with gamma-ray bursts with the ANTARES neutrino telescope  

SciTech Connect

A search for neutrino-induced muons in correlation with a selection of 40 gamma-ray bursts that occurred in 2007 has been performed with the ANTARES neutrino telescope. During that period, the detector consisted of 5 detection lines. The ANTARES neutrino telescope is sensitive to TeVPeV neutrinos that are predicted from gamma-ray bursts. No events were found in correlation with the prompt photon emission of the gamma-ray bursts and upper limits have been placed on the flux and fluence of neutrinos for different models.

NONE

2013-03-01

248

Gamma-Ray Burst Early Afterglows  

E-print Network

The successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore the unknown physical composition of GRB jets, the link between the prompt gamma-ray emission and the afterglow emission, the GRB central engine activity, as well as the immediate GRB environment. Here I review some of the recent theoretical efforts to address these problems and describe how the latest Swift data give answers to these outstanding questions.

Bing Zhang

2005-09-19

249

Cosmic gamma-ray lines - Theory  

NASA Technical Reports Server (NTRS)

The various processes that lead to gamma-ray line emission and the possible astrophysical sources of such emission are reviewed. The processes of nuclear excitation, radiative capture, positron annihilation, and cyclotron radiation, which may produce gamma-ray line emission from such diverse sources as the interstellar medium, novas, supernovas, pulsars, accreting compact objects, the galactic nucleus and the nuclei of active galaxies are considered. The significance of the relative intensities, widths, and frequency shifts of the lines are also discussed. Particular emphasis is placed on understanding those gamma-ray lines that have already been observed from astrophysical sources.

Lingenfelter, R. E.; Ramaty, R.

1980-01-01

250

Detecting axionlike particles with gamma ray telescopes.  

PubMed

We propose that axionlike particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma-ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the "Hillas criterion", such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground-based gamma-ray telescopes in the TeV range. PMID:18233353

Hooper, Dan; Serpico, Pasquale D

2007-12-01

251

Very High Energy Gamma-Ray Astronomy  

E-print Network

We present a review of the current status of very high energy gamma-ray astronomy. The development of the atmospheric Cherenkov imaging technique for ground-based gamma-ray astronomy has led to a rapid growth in the number of observatories. The detection of TeV gamma rays from Active Galactic Nuclei was unexpected and is providing new insights into the emission mechanisms in the jets. Next generation telescopes are under construction and will increase dramatically the knowledge available at this extreme end of the cosmic electromagnetic spectrum.

Michael Catanese; Trevor C. Weekes

1999-06-30

252

NEAR Gamma Ray Spectrometer Characterization and Repair  

NASA Technical Reports Server (NTRS)

This report covers the work completed in the third year of the contract. The principle activities during this period were (1) the characterization of the NEAR 2 Gamma Ray Spectrometer using a neutron generator to generate complex gamma ray spectra and a large Ge Detecter to identify all the major peaks in the spectra; (2) the evaluation and repair of the Engineering Model Unit of the Gamma Ray Spectrometer for the NEAR mission; (3) the investigation of polycapillary x-ray optics for x-ray detection; and (4) technology transfer from NASA to forensic science.

Groves, Joel Lee; Vajda, Stefan

1998-01-01

253

Cosmic-ray effects on diffuse gamma-ray measurements.  

NASA Technical Reports Server (NTRS)

Evaluation of calculations and experimental evidence from 600-MeV proton irradiation indicating that cosmic-ray-induced radioactivity in detectors used to measure the diffuse gamma-ray background produces a significant counting rate in the energy region around 1 MeV. It is concluded that these counts may be responsible for the observed flattening of the diffuse photon spectrum at this energy.

Fishman, G. J.

1972-01-01

254

Gamma-Ray Pulsar Studies with GLAST  

E-print Network

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

D. J. Thompson

2007-11-27

255

Thermal neutron capture gamma-rays  

SciTech Connect

The energy and intensity of gamma rays as seen in thermal neutron capture are presented. Only those (n,..cap alpha..), E = thermal, reactions for which the residual nucleus mass number is greater than or equal to 45 are included. These correspond to evaluations published in Nuclear Data Sheets. The publication source data are contained in the Evaluated Nuclear Structure Data File (ENSDF). The data presented here do not involve any additional evaluation. Appendix I lists all the residual nuclides for which the data are included here. Appendix II gives a cumulated index to A-chain evaluations including the year of publication. The capture gamma ray data are given in two tables - the Table 1 is the list of all gamma rays seen in (n,..gamma..) reaction given in the order of increasing energy; the Table II lists the gamma rays according to the nuclide.

Tuli, J.K.

1983-01-01

256

Optical reprocessing of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

One model for the optical flashes associated with three cosmic gamma-ray burst sources invokes the reprocessing of some of the gamma-radiation emitted by a hypothesized collapsed object in the surface layers of a nearby companion star. This model was investigated by carrying out detail, fully hydrodynamical calculations of such reprocessing in the surface layers of very low mass stars. It is found that, at most, 7 percent of the gamma-ray fluence incident on the companion star is reprocessed into the blue band; the time scale for this reprocessing is typically 100 s, which is long compared to the duration of the gamma-ray burst itself. Using this result, it is shown that there is marginal agreement between the observed and calculated ratios of gamma-ray fluence to optical fluence at earth.

Melia, F.; Rappaport, S.; Joss, P. C.

1986-01-01

257

Optical reprocessing of gamma-ray bursts  

SciTech Connect

One model for the optical flashes associated with three cosmic gamma-ray burst sources invokes the reprocessing of some of the gamma-radiation emitted by a hypothesized collapsed object in the surface layers of a nearby companion star. This model was investigated by carrying out detail, fully hydrodynamical calculations of such reprocessing in the surface layers of very low mass stars. It is found that, at most, 7 percent of the gamma-ray fluence incident on the companion star is reprocessed into the blue band; the time scale for this reprocessing is typically 100 s, which is long compared to the duration of the gamma-ray burst itself. Using this result, it is shown that there is marginal agreement between the observed and calculated ratios of gamma-ray fluence to optical fluence at earth. 18 references.

Melia, F.; Rappaport, S.; Joss, P.C.

1986-06-01

258

Neutron Detection Gamma Ray Sensitivity Criteria  

SciTech Connect

The shortage of 3He has triggered the search for effective alternative neutron detection technologies for national security and safeguards applications. Any new detection technology must satisfy two basic criteria: (1) it must meet a neutron detection efficiency requirement, and (2) it must be insensitive to gamma-ray interference at a prescribed level, while still meeting the neutron detection requirement. It is the purpose of this paper to define measureable gamma ray sensitivity criteria for neutron detectors. Quantitative requirements are specified for: intrinsic gamma ray detection efficiency and gamma ray absolute rejection. The ratio GARRn is defined, and it is proposed that the requirement for neutron detection be 0.9 < GARRn < 1.1 at a 10 mR/h exposure rate. An example of results from a 3He based neutron detector are provided showing that this technology can meet the stated requirements. Results from tests of some alternative technologies are also reported.

Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Mace, Emily K.; Stephens, Daniel L.; Woodring, Mitchell L.

2011-10-21

259

Gamma-Ray Pulsar Studies With GLAST  

SciTech Connect

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

Thompson, D.J.; /NASA, Goddard

2011-11-23

260

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

Research activities in cosmic rays, gamma rays, and astrophysical plasmas are covered. The activities are divided into sections and described, followed by a bibliography. The astrophysical aspects of cosmic rays, gamma rays, and of the radiation and electromagnetic field environment of the Earth and other planets are investigated. These investigations are performed by means of energetic particle and photon detector systems flown on spacecraft and balloons.

Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

1989-01-01

261

Gamma-ray binaries and related systems  

NASA Astrophysics Data System (ADS)

After initial claims and a long hiatus, it is now established that several binary stars emit high- (0.1-100 GeV) and very high-energy (>100 GeV) gamma rays. A new class has emerged called "gamma-ray binaries", since most of their radiated power is emitted beyond 1 MeV. Accreting X-ray binaries, novae and a colliding wind binary ( ? Car) have also been detected"related systems" that confirm the ubiquity of particle acceleration in astrophysical sources. Do these systems have anything in common? What drives their high-energy emission? How do the processes involved compare to those in other sources of gamma rays: pulsars, active galactic nuclei, supernova remnants? I review the wealth of observational and theoretical work that have followed these detections, with an emphasis on gamma-ray binaries. I present the current evidence that gamma-ray binaries are driven by rotation-powered pulsars. Binaries are laboratories giving access to different vantage points or physical conditions on a regular timescale as the components revolve on their orbit. I explain the basic ingredients that models of gamma-ray binaries use, the challenges that they currently face, and how they can bring insights into the physics of pulsars. I discuss how gamma-ray emission from microquasars provides a window into the connection between accretion-ejection and acceleration, while ? Car and novae raise new questions on the physics of these objectsor on the theory of diffusive shock acceleration. Indeed, explaining the gamma-ray emission from binaries strains our theories of high-energy astrophysical processes, by testing them on scales and in environments that were generally not foreseen, and this is how these detections are most valuable.

Dubus, Guillaume

2013-08-01

262

The Gamma-Ray Imager GRI  

NASA Astrophysics Data System (ADS)

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Wunderer, Cornelia B.; GRI Collaboration

2006-09-01

263

GRI: the gamma-ray imager mission  

NASA Astrophysics Data System (ADS)

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques hav paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Kndlseder, Jrgen

2006-06-01

264

Classification of Swift's gamma-ray bursts  

Microsoft Academic Search

Context. Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 s. There are, however, some indications for the existence of a third class. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for gamma-ray bursts. Therefore we reanalyze the durations and their distribution and also the classi-

I. Horvth; L. G. Balzs; Z. Bagoly; P. Veres

2008-01-01

265

Swift Observations of Gamma-Ray Bursts  

Microsoft Academic Search

The Swift mission, launched on 20 November 2004, is detecting ~ 100 gamma-ray bursts (GRBs) each year, and immediately (within ~ 90 s) starting X-ray and UV\\/optical observations of the afterglow. It has already collected an impressive database including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows, and rapid follow-up by other observatories notified through the Gamma-ray

Neil Gehrels

2008-01-01

266

High altitude balloons and gamma ray astronomy  

SciTech Connect

The author's experience with scientific high altitude ballooning will be presented. Usefulness of satellite versus balloon platforms will be contrasted in the context of gamma ray astronomy. General principles of gamma ray astronomy instrumentation will be discussed and illustrated in terms of our current instrument, GRIS. Some words about the supernova phenomenon and its necessity for the existence of life in the universe will be followed by a brief glimpse of our preliminary data from Supernova 1987a.

MacCallum, C.J.

1988-01-01

267

Neutrinos and Gamma Rays from Galaxy Clusters  

E-print Network

The next generation of neutrino and gamma-ray detectors should provide new insights into the creation and propagation of high-energy protons within galaxy clusters, probing both the particle physics of cosmic rays interacting with the background medium and the mechanisms for high-energy particle production within the cluster. In this paper we examine the possible detection of gamma-rays (via the GLAST satellite) and neutrinos (via the ICECUBE and Auger experiments) from the Coma cluster of galaxies, as well as for the gamma-ray bright clusters Abell 85, 1758, and 1914. These three were selected from their possible association with unidentified EGRET sources, so it is not yet entirely certain that their gamma-rays are indeed produced diffusively within the intracluster medium, as opposed to AGNs. It is not obvious why these inconspicuous Abell-clusters should be the first to be seen in gamma-rays, but a possible reason is that all of them show direct evidence of recent or ongoing mergers. Their identification with the EGRET gamma-ray sources is also supported by the close correlation between their radio and (purported) gamma-ray fluxes. Under favorable conditions (including a proton spectral index of 2.5 in the case of Abell 85, and sim 2.3 for Coma, and Abell 1758 and 1914), we expect ICECUBE to make as many as 0.3 neutrino detections per year from the Coma cluster of galaxies, and as many as a few per year from the Abell clusters 85, 1758, and 1914. Also, Auger may detect as many as 2 events per decade at ~ EeV energies from these gamma-ray bright clusters.

Brandon Wolfe; Fulvio Melia; Roland M. Crocker; Raymond R. Volkas

2008-07-04

268

The Mystery of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts remain on of the greatest mysteries in astrophysics in spite of recent observational advances and intense theoretical work. Although some of the basic properties of bursts were known 25 years ago, new and more detailed observations have been made by the BATSE (Burst and Transient Source Experiment) experiment on the Compton Gamma Ray Observatory in the past five years. Recent observations of bursts and some proposed models will be discussed.

Fishman, Gerald J.

1998-01-01

269

Gamma Ray Astronomy with Underground Detectors  

Microsoft Academic Search

Underground detectors measure the directions of up-coming muons of neutrino origin. They can also observe down-going muons made by gamma rays in the Earth's atmosphere. Although gamma ray showers are muon-poor, they produce a sufficient number of muons to detect the sources observed by GeV and TeV telescopes. With a threshold higher by one hundred and a probability of muon

F. Halzen; T. Stanev

1995-01-01

270

VHE gamma-ray astronomy: observations  

Microsoft Academic Search

The recent operation of a new generation of Cherenkov telescopes is providing unprecedented results which are opening in the last months a truly new age in VHE cosmic gamma-ray observations. We're in the down of the setting of a new window in our observation of the cosmos: VHE gamma-ray astronomy. The techniques and concepts used by these new telescopes is

Manel Martnez

2006-01-01

271

Gamma ray astronomy with COS-B  

Microsoft Academic Search

Observational results in the field of gamma-ray astronomy that have been obtained to date with the COS-B satellite are discussed and questions raised by these observations are summarized. Following a brief review of the instrumental characteristics of COS-B and the extent of COS-B gamma-ray coverage of the sky, particular attention is given to the questions raised by the discovery of

B. N. Swanenburg

1981-01-01

272

Microsatellite gamma-ray spectroscopy experiment  

Microsoft Academic Search

Preliminary results from Gamma ray experiment installed on a micro-satellite, Techsat 1, are reported. The experiment is based on CdZnTe detectors coupled to custom designed CMOS electronics, which includes low noise charge sensitive preamplifiers, pulse shaping amplifiers and sampling circuits. It was realized as a mile stone towards a micro- satellite mounted Gamma ray space telescope. The experiment is a

G. Asa; Arie Ruzin; Claudio G. Jakobson; G. Shaviv; Yael Nemirovsky

1999-01-01

273

Nature of gamma-ray burst spectra  

SciTech Connect

The recent discovery of low-energy absorption features in the spectra of gamma-ray bursts (GRBs) reported by Murakami et al. (1988) is discussed in the context of a new model for gamma-ray emission in isolated neutron-star sources. It is shown that the whole GRB spectrum may be due to irradiation of a reprocessing and reflecting boundary near a source of power-law gamma radiation. In this picture, the gamma-rays originate far above the surface of a magnetized neutron star where attenuation of the spectrum by pair production is minimal. The surface layers of the neutron star absorb a fraction of the gamma-ray energy and reflect some of the gamma-rays. The resultant spectrum is comprised of a power law at high energy, a steep component at intermediate energy, and a thermal component at low energy. There is a slight enhancement of the gamma-ray flux near E0 that may be the cause of the apparent d(-)d(+) annihilation line seen in some bursts. 27 references.

Melia, F.

1988-11-01

274

Gamma-ray spectroscopy: An historical perspective  

SciTech Connect

The possibility of MeV-range gamma-rays from extraterrestrial sources had been speculated on by cosmic-ray physicists since the late 1940's. The first definitive detection occurred with balloon-borne cosmic-ray instrumentation during a class 2 solar flare in March 1958, apparently associated with the acceleration of a nonthermal particle population. Following this detection, physicists were motivated to develop instrumentation specific for observation of astronomical gamma-ray sources. Gamma-ray lines were also first observed during the flares of August 1972, apparently associated with accelerated particles undergoing nuclear interactions in the solar atmosphere. The development of low background, high resolution Ge counters has permitted construction of gamma-ray telescopes with unprecedented resolution and sensitivity. Even modest versions of these devices have measured discrete gamma-ray lines from sources as diverse as cosmic gamma-ray bursts, the galactic center and the galactic plane. Many other predictions are within the range of modern detectors.

Peterson, L.E.

1988-09-25

275

Gamma-ray albedo of the moon  

E-print Network

We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 4 GeV (600 MeV for the inner part of the Moon disc). Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation; this makes it a useful "standard candle" for gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo gamma rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

Igor V. Moskalenko; Troy A. Porter

2007-08-15

276

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-print Network

grail of gamma-ray burst astronomy for a quarter of a century. From the discovery of gamma-ray burstsThe Biggest Bangs The Mystery of Gamma-Ray Bursts, The Most Violent Explosions in The Universe J. I a Gamma-Ray Burst Kill the Dinosaurs? Will a Burst Kill Us? · Glossary · Sources · Index viii #12;Chapter

Katz, Jonathan I.

277

Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy  

SciTech Connect

The beta-delayed gamma-ray spectra from the fission of {sup 235}U, {sup 238}U, and {sup 239}Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 minute to 14 hours. Spectra at all delay times contain sets of prominent gamma-ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.

Marrs, R E; Norman, E B; Burke, J T; Macri, R A; Shugart, H A; Browne, E; Smith, A R

2007-11-15

278

Understanding hadronic gamma-ray emission from supernova remnants  

E-print Network

We aim to test the plausibility of a theoretical framework in which the gamma-ray emission detected from supernova remnants may be of hadronic origin, i.e., due to the decay of neutral pions produced in nuclear collisions involving relativistic nuclei. In particular, we investigate the effects induced by magnetic field amplification on the expected particle spectra, outlining a phenomenological scenario consistent with both the underlying Physics and the larger and larger amount of observational data provided by the present generation of gamma experiments, which seem to indicate rather steep spectra for the accelerated particles. In addition, in order to study to study how pre-supernova winds might affect the expected emission in this class of sources, the time-dependent gamma-ray luminosity of a remnant with a massive progenitor is worked out. Solid points and limitations of the proposed scenario are finally discussed in a critical way.

Damiano Caprioli

2011-05-06

279

Measurement of radionuclide activities induced in target components of an IBA CYCLONE 18/9 by gamma-ray spectrometry with HPGe and LaBr3: Ce detectors.  

PubMed

Cyclotrons are used worldwide to produce radiopharmaceuticals by proton irradiation of a suitable target. The intense secondary neutron beam generated by proton interactions with the target induce high radionuclide activities in the target assembly parts that may result in an exposure to high dose levels of the operators during maintenance. The main goal of this work is to evaluate gamma-emitting radionuclide activities induced in Havar foils and titanium windows of a target assembly and carousel stripper forks of an IBA CYCLONE 18/9 cyclotron. The knowledge of radionuclide inventory for each component is required by many companies to assess risk for operators before waste handling and disposal. Gamma-ray spectrometric analyses were carried out with High Purity Germanium (HPGe) and Lanthanum bromide (LaBr3:Ce) scintillation detectors. HPGe is the most used detector for its high energy resolution although it is more suitable for use in a laboratory. The use of LaBr3:Ce can be considered a viable option, particularly in realizing a portable spectrometric system to perform "on-site" measurements and a fast dose rate evaluation before the disposal of activated parts. Due to a high activity of target assembly components replaced after a typical irradiation cycle (about 5000 ?Ah integrated beam current), gamma-ray spectrometric measurements were performed at a large distance from the detector, even more than 100 cm, or by using a purposely realized Lead-walled collimator. The identification of some key-radionuclides allows to evaluate through simple formulations the dose rate behavior for each component as function of decay time from the last irradiation. The knowledge of the dose rate behavior is a significant piece of information to health physicists for waste handling with safety at work. For an Havar foil, the dose rate will be reduced to about 1/1,000 of the starting value after a decay period of approximately 4 y (about 1,500 d), with a relatively safety at product disposal work. For a longer time, only long-lived radionuclides (57)Co, (60)Co, and (54)Mn contribute to dose rate. PMID:24949919

Tomarchio, Elio

2014-08-01

280

Supernovae and Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Participants; Preface; Gamma-ray burst-supernova relation B. Paczynski; Observations of gamma-ray bursts G. Fishman; Fireballs T. Piran; Gamma-ray mechanisms M. Rees; Prompt optical emission from gamma-ray bursts R. Kehoe, C. Akerlof, R. Balsano, S. Barthelmy, J. Bloch, P. Butterworth, D. Casperson, T. Cline, S. Fletcher, F. Frontera, G. Gisler, J. Heise, J. Hills, K. Hurley, B. Lee, S. Marshall, T. McKay, A. Pawl, L. Piro, B. Priedhorsky, J. Szymanski and J. Wren; X-ray afterglows of gamma-ray bursts L. Piro; The first year of optical-IR observations of SN1998bw I. Danziger, T. Augusteijn, J. Brewer, E. Cappellaro, V. Doublier, T. Galama, J. Gonzalez, O. Hainaut, B. Leibundgut, C. Lidman, P. Mazzali, K. Nomoto, F. Patat, J. Spyromilio, M. Turatto, J. Van Paradijs, P. Vreeswijk and J. Walsh; X-ray emission of Supernova 1998bw in the error box of GRB980425 E. Pian; Direct analysis of spectra of type Ic supernovae D. Branch; The interaction of supernovae and gamma-ray bursts with their surroundings R. Chevalier; Magnetars, soft gamma-ray repeaters and gamma-ray bursts A. Harding; Super-luminous supernova remnants Y. -H. Chu, C. -H. Chen and S. -P. Lai; The properties of hypernovae: SNe Ic 1998bw, 1997ef, and SN IIn 1997cy K. Nomoto, P. Mazzali, T. Nakamura, K. Iwanmoto, K. Maeda, T. Suzuki, M. Turatto, I. Danziger and F. Patat; Collapsars, Gamma-Ray Bursts, and Supernovae S. Woosley, A. MacFadyen and A. Heger; Pre-supernova evolution of massive stars N. Panagia and G. Bono; Radio supernovae and GRB 980425 K. Weiler, N. Panagia, R. Sramek, S. Van Dyk, M. Montes and C. Lacey; Models for Ia supernovae and evolutionary effects P. Hoflich and I. Dominguez; Deflagration to detonation A. Khokhlov; Universality in SN Iae and the Phillips relation D. Arnett; Abundances from supernovae F. -K. Thielemann, F. Brachwitz, C. Freiburghaus, S. Rosswog, K. Iwamoto, T. Nakamura, K. Nomoto, H. Umeda, K. Langanke, G. Martinez-Pinedo, D. Dean, W. Hix and M. Strayer; Sne, GRBs, and the global properties of the Universe B. Schmidt; How good are SNe Ia as standard candles? A. Sandage, G. Tammann and A. Saha; Type Ia supernovae and their implications for cosmology M. Livio; Conference summary: supernovae and gamma-ray bursts J. Wheeler.

Livio, Mario; Panagia, Nino; Sahu, Kailash

2001-07-01

281

Gamma ray astrophysics to the year 2000. Report of the NASA Gamma Ray Program Working Group  

NASA Technical Reports Server (NTRS)

Important developments in gamma-ray astrophysics up to energies of 100 GeV during the last decade are reviewed. Also, the report seeks to define the major current scientific goals of the field and proposes a vigorous program to pursue them, extending to the year 2000. The goals of gamma-ray astronomy include the study of gamma rays which provide the most direct means of studying many important problems in high energy astrophysics including explosive nucleosynthesis, accelerated particle interactions and sources, and high-energy processes around compact objects. The current research program in gamma-ray astronomy in the U.S. including the space program, balloon program and foreign programs in gamma-ray astronomy is described. The high priority recommendations for future study include an Explorer-class high resolution gamma-ray spectroscopy mission and a Get Away Special cannister (GAS-can) or Scout class multiwavelength experiment for the study of gamma-ray bursts. Continuing programs include an extended Gamma Ray Observatory mission, continuation of the vigorous program of balloon observations of the nearby Supernova 1987A, augmentation of the balloon program to provide for new instruments and rapid scientific results, and continuation of support for theoretical research. Long term recommendations include new space missions using advanced detectors to better study gamma-ray sources, the development of these detectors, continued study for the assembly of large detectors in space, collaboration with the gamma-ray astronomy missions initiated by other countries, and consideration of the Space Station attached payloads for gamma-ray experiments.

1988-01-01

282

CONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2  

E-print Network

Energy Gamma Ray Astronomy (HEGRA) has been published for emission above 20 TeV from GRB 920925c (PadillaCONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2 W. Benbow,3 11; accepted 2005 June 3 ABSTRACT The Milagro Gamma-Ray Observatory employs a water Cerenkov detector

California at Santa Cruz, University of

283

DISCOVERY OF LOCALIZED TEV GAMMA-RAY SOURCES AND DIFFUSE TEV GAMMA-RAY EMISSION FROM THE GALACTIC  

E-print Network

OF PHILOSOPHY Department of Physics and Astronomy 2007 #12;ABSTRACT DISCOVERY OF LOCALIZED TEV GAMMA-RAY SOURCESDISCOVERY OF LOCALIZED TEV GAMMA-RAY SOURCES AND DIFFUSE TEV GAMMA-RAY EMISSION FROM THE GALACTIC AND DIFFUSE TEV GAMMA-RAY EMISSION FROM THE GALACTIC PLANE WITH MILAGRO USING A NEW BACKGROUND REJECTION

California at Santa Cruz, University of

284

Mercuric iodine room temperature gamma-ray detectors  

NASA Technical Reports Server (NTRS)

high resolution mercuric iodide room temperature gamma-ray detectors have excellent potential as an essential component of space instruments to be used for high energy astrophysics. Mercuric iodide detectors are being developed both as photodetectors used in combination with scintillation crystals to detect gamma-rays, and as direct gamma-ray detectors. These detectors are highly radiation damage resistant. The list of applications includes gamma-ray burst detection, gamma-ray line astronomy, solar flare studies, and elemental analysis.

Patt, Bradley E.; Markakis, Jeffrey M.; Gerrish, Vernon M.; Haymes, Robert C.; Trombka, Jacob I.

1990-01-01

285

Gamma-ray spectrometry of LDEF samples  

SciTech Connect

A total of 31 samples from the Long Duration Exposure Facility (LDEF), including materials of aluminum, vanadium, and steel trunnions were analyzed by ultra-low-level gamma spectroscopy. The study quantified particle induced activations of (sup 22)Na, {sup 46}Sc, {sup 51}Cr, {sup 54}Mn, {sup 56}Co, {sup 57}Co, {sup 58}Co, and {sup 60}Co. The samples of trunnion sections exhibited increasing activity toward the outer end of the trunnion and decreasing activity toward its radial center. The trunnion sections did not include end pieces, which have been reported to collect noticeable {sup 7}Be on their leading surfaces. No significant {sup 7}Be was detected in the samples analyzed. The Underground Counting Facility at Savannah River Laboratory (SRL) was used in this work. The facility is 50 ft. underground, constructed with low-background shielding materials, and operated as a clean room. The most sensitive analyses were performed with a 90%-efficient HPGe gamma-ray detector, which is enclosed in a purged active/passive shield. Each sample was counted for one to six days in two orientations to yield more representative average activities for the sample. The non-standard geometries of the LDEF samples prompted the development of a novel calibration method, whereby the efficiency about the samples surfaces (measured with point sources) predicted the efficiency for the bulk sample.

Winn, W.G.

1991-01-01

286

Gamma-ray spectrometry of LDEF samples  

SciTech Connect

A total of 31 samples from the Long Duration Exposure Facility (LDEF), including materials of aluminum, vanadium, and steel trunnions were analyzed by ultra-low-level gamma spectroscopy. The study quantified particle induced activations of (sup 22)Na, {sup 46}Sc, {sup 51}Cr, {sup 54}Mn, {sup 56}Co, {sup 57}Co, {sup 58}Co, and {sup 60}Co. The samples of trunnion sections exhibited increasing activity toward the outer end of the trunnion and decreasing activity toward its radial center. The trunnion sections did not include end pieces, which have been reported to collect noticeable {sup 7}Be on their leading surfaces. No significant {sup 7}Be was detected in the samples analyzed. The Underground Counting Facility at Savannah River Laboratory (SRL) was used in this work. The facility is 50 ft. underground, constructed with low-background shielding materials, and operated as a clean room. The most sensitive analyses were performed with a 90%-efficient HPGe gamma-ray detector, which is enclosed in a purged active/passive shield. Each sample was counted for one to six days in two orientations to yield more representative average activities for the sample. The non-standard geometries of the LDEF samples prompted the development of a novel calibration method, whereby the efficiency about the samples surfaces (measured with point sources) predicted the efficiency for the bulk sample.

Winn, W.G.

1991-12-31

287

Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis  

SciTech Connect

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

Xie Xufei; Zhang Xing; Yuan Xi; Chen Jinxiang; Li Xiangqing; Zhang Guohui; Fan Tieshuan [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing (China); Yuan Guoliang; Yang Jinwei; Yang Qingwei [Southwestern Institute of Physics, Chengdu (China)

2012-09-15

288

The Gamma-Ray Imager GRI  

NASA Astrophysics Data System (ADS)

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are major science themes that are addressed in the gamma-ray regime. ESA's INTEGRAL observatory currently provides the astronomical community with a unique tool to investigate the sky up to MeV energies and hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes have been discovered. NASA's GLAST mission will similarly take the next step in surveying the high-energy ( GeV) sky, and NuSTAR will pioneer focusing observations at hard X-ray energies (to 80 keV). There will be clearly a growing need to perform deeper, more focused investigations of gamma-ray sources in the 100-keV to MeV regime. Recent technological advances in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow the study of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Wunderer, Cornelia B.; GRI Collaboration

2008-03-01

289

117Fermi Detects Gamma-Rays from Messier 82 The Fermi Gamma-Ray Space  

E-print Network

telescope is red; Hubble space telescope observations of hydrogen line emission is orange, and the bluest117Fermi Detects Gamma-Rays from Messier 82 The Fermi Gamma-Ray Space Telescope has recently rays/sec/cm 2 at energies of 10,000 and 100,000 MeV. Space Math http://spacemath.gsfc.nasa.gov #12

290

Radiation-induced mutations and plant breeding  

SciTech Connect

Ionizing radiation could cause genetic changes in an organism and could modify gene linkages. The induction of mutation through radiation is random and the probability of getting the desired genetic change is low but can be increased by manipulating different parameters such as dose rate, physical conditions under which the material has been irradiated, etc. Induced mutations have been used as a supplement to conventional plant breeding, particularly for creating genetic variability for specific characters such as improved plant structure, pest and disease resistance, and desired changes in maturity period; more than 200 varieties of crop plants have been developed by this technique. The Pakistan Atomic Energy Commission has used this technique fruitfully to evolve better germplasm in cotton, rice, chickpea, wheat and mungbean; some of the mutants have become popular commercial varieties. This paper describes some uses of radiation induced mutations and the results achieved in Pakistan so far.

Naqvi, S.H.M.

1985-01-01

291

Present aspects of induced mutations in plant breeding  

Microsoft Academic Search

The present status of the utilization of induced mutations in plant breeding is briefly reviewed. It is concluded that with induced mutations in principle successes can be expected similar to those with the conventional breeding methods. Owing to the relatively small yield of progressive mutations the efficiency of mutation breeding, however, is rather poor at present. Greater efficiency may be

Horst Gaul

1958-01-01

292

Gamma-ray lines from radiative dark matter decay  

SciTech Connect

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Garny, Mathias; Ibarra, Alejandro; Tran, David [Physik-Department T30d, Technische Universitt Mnchen, James-Franck-Strae, 85748 Garching (Germany); Weniger, Christoph, E-mail: mathias.garny@ph.tum.de, E-mail: alejandro.ibarra@ph.tum.de, E-mail: david.tran@ph.tum.de, E-mail: weniger@mppmu.mpg.de [Max-Planck-Institut fr Physik, Mnchen, Fhringer Ring 6, 80805 Mnchen (Germany)

2011-01-01

293

GRI: The Gamma-Ray Imager mission  

NASA Astrophysics Data System (ADS)

With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction have paved the way towards a new gamma-ray mission, providing major improvements regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow the study of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Kndlseder, Jrgen; GRI Consortium

2006-06-01

294

GRI: The Gamma-Ray Imager mission  

NASA Astrophysics Data System (ADS)

With the INTEGRAL observatory ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction have paved the way towards a new gamma-ray mission, providing major improvements regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow studies of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Kndlseder, Jrgen

295

Observing Gamma-ray Bursts with GLAST  

NASA Technical Reports Server (NTRS)

The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high-energy gamma-ray sky. The Large Area Telescope, the main instrument, is a pair-conversion telescope which will survey the sky in the energy range 20 MeV to greater than 300 GeV. The LAT's wide field of view (greater than 2 sr), large effective area and low deadtime combine to provide excellent high-energy gamma-ray observations of GRB. To tie these frontier high-energy observations to the better-known properties at lower energies, a second instrument, the GLAST Burst Monitor (GBM) will provide important spectra and timing in the 8 keV to 30 MeV range. Upon detection of a GRB by the LAT or the GBM, the spacecraft can autonomously repoint to keep the GRB location within the LAT field of view, allowing high-energy afterglow observations. We describe how the instruments, spacecraft, and ground system work together to provide observations of gamma-ray bursts from 8 keV to over 300 GeV and provide rapid notification of these observations to the wider gamma-ray burst community. Analysis and simulation tools dedicated to the GRB science have been developed. In this contribution we show the expected LAT sensitivity obtained with such simulations, and illustrate the results we expect from GLAST observations with spectral and temporal analysis of simulated GRB.

McEnery, Julie

2008-01-01

296

ADP study of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

This grant supported study of cyclotron scattering lines in the spectra of gamma-ray bursts through analysis of Ginga and HEAO-1 archival data, and modeling of the results in terms of radiation transfer calculations of cyclotron scattering in a strong magnetic field. A Monte Carlo radiation transfer code with which we are able to calculate the expected properties of cyclotron scattering lines in the spectra of gamma-ray bursts was developed. The extensive software necessary in order to carry out fits of these model spectra to gamma-ray burst spectral data, including folding of the model spectra through the detector response functions was also developed. Fits to Ginga satellite data on burst GB880205 were completed and fits to Ginga satellite data on burst GB870303 are being carried out. These fits have allowed us to test our software, as well as to garner new scientific results. This work has demonstrated that cyclotron resonant scattering successfully accounts for the locations, strengths, and widths of the observed line features in GB870303 and GB880205. The success of the model provides compelling evidence that these gamma-ray bursts come from strongly magnetic neutron stars and are galactic in origin, resolving longstanding controversies about the nature and distance of the burst sources. These results were reported in two papers which are in press in the proceedings of the Taos Workshop on Gamma-Ray Bursts, and in a paper submitted for publication.

Lamb, Don Q.; Wang, John C. L.; Heuter, Geoffry J.; Graziani, Carlo; Loredo, Tom; Freeman, Peter

1991-01-01

297

Gamma-ray Emission from Nova Outbursts  

NASA Astrophysics Data System (ADS)

Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission, with the 511 keV line and a continuum. Gamma-ray spectra and light curves are potential unique tools to trace the corresponding isotopes and to give insights on the properties of the expanding envelope. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected with the Fermi satellite in V407 Cyg, a nova in a symbiotic binary, where the companion is a red giant with a wind, instead of a main sequence star as in the cataclysmic variables hosting classical novae. Two more novae have been detected recently (summer 2012) by Fermi, apparently in non symbiotic binaries, thus challenging our understanding of the emission mechanism. Both scenarios (radioactivities and acceleration) of gamma-ray production in novae are discussed.

Hernanz, M.

2014-12-01

298

The Pulsing Gamma-ray Sky  

NASA Astrophysics Data System (ADS)

The Fermi Space Telescope, with its discovery of nearly 150 gamma-ray pulsars has solidified and extended the suspicions of the EGRET era: energetic spin-powered pulsars are fantastic particle accelerators, they emit most of their photon energy in the GeV range and they paint their gamma-ray beams over much of the sky. I summarize here the suite of gamma-ray discoveries and what it has taught us about pulsar populations. Young, classical radio-detectable pulsars, gamma-ray only `Gemingas' and energetic millisecond pulsars are equally represented in the Fermi sky. This sample certainly reveals much about magnetospheric physics. However, by chasing down the pulsars responsible for Fermi sources we continue to discover exotic systems whose study impacts a wide range of high energy astrophysics. Gamma-ray pulsars are revealing details of close binary evolution, testing the equation of state of ultra-dense matter, helping us understand the cosmic ray positrons, and aiding in the search for ultra-low frequency gravitational radiation. I summarize recent progress on these fronts and the prospects for more exciting discoveries to come.

Romani, Roger W.

2014-01-01

299

LUMINOSITY EVOLUTION OF GAMMA-RAY PULSARS  

SciTech Connect

We investigate the electrodynamic structure of a pulsar outer-magnetospheric particle accelerator and the resulting gamma-ray emission. By considering the condition for the accelerator to be self-sustained, we derive how the trans-magnetic-field thickness of the accelerator evolves with the pulsar age. It is found that the thickness is small but increases steadily if the neutron-star envelope is contaminated by sufficient light elements. For such a light element envelope, the gamma-ray luminosity of the accelerator is kept approximately constant as a function of age in the initial 10,000 yr, forming the lower bound of the observed distribution of the gamma-ray luminosity of rotation-powered pulsars. If the envelope consists of only heavy elements, on the other hand, the thickness is greater, but it increases less rapidly than a light element envelope. For such a heavy element envelope, the gamma-ray luminosity decreases relatively rapidly, forming the upper bound of the observed distribution. The gamma-ray luminosity of a general pulsar resides between these two extreme cases, reflecting the envelope composition and the magnetic inclination angle with respect to the rotation axis. The cutoff energy of the primary curvature emission is regulated below several GeV even for young pulsars because the gap thickness, and hence the acceleration electric field, is suppressed by the polarization of the produced pairs.

Hirotani, Kouichi, E-mail: hirotani@tiara.sinica.edu.tw [Postal address: TIARA, Department of Physics, National Tsing Hua University, 101, Sec. 2, Kuang Fu Rd., Hsinchu 300, Taiwan. (China)] [Postal address: TIARA, Department of Physics, National Tsing Hua University, 101, Sec. 2, Kuang Fu Rd., Hsinchu 300, Taiwan. (China)

2013-04-01

300

Gamma-ray burster recurrence timescales  

NASA Technical Reports Server (NTRS)

Three optical transients have been found which are associated with gamma-ray bursters (GRBs). The deduced recurrence timescale for these optical transients (tau sub opt) will depend on the minimum brightness for which a flash would be detected. A detailed analysis using all available data of tau sub opt as a function of E(gamma)/E(opt) is given. For flashes similar to those found in the Harvard archives, the best estimate of tau sub opt is 0.74 years, with a 99% confidence interval from 0.23 years to 4.7 years. It is currently unclear whether the optical transients from GRBs also give rise to gamma-ray events. One way to test this association is to measure the recurrence timescale of gamma-ray events tau sub gamma. A total of 210 gamma-ray error boxes were examined and it was found that the number of observed overlaps is not significantly different from the number expected from chance coincidence. This observation can be used to place limits on tau sub gamma for an assumed luminosity function. It was found that tau sub gamma is approx. 10 yr if bursts are monoenergetic. However, if GRBs have a power law luminosity function with a wide dynamic range, then the limit is tau sub gamma 0.5 yr. Hence, the gamma-ray data do not require tau sub gamma and tau sub opt to be different.

Schaefer, B. E.; Cline, T. L.

1984-01-01

301

Gamma rays from pulsar wind shock acceleration  

NASA Technical Reports Server (NTRS)

A shock forming in the wind of relativistic electron-positron pairs from a pulsar, as a result of confinement by surrounding material, could convert part of the pulsar spin-down luminosity to high energy particles through first order Fermi acceleration. High energy protons could be produced by this mechanism both in supernova remnants and in binary systems containing pulsars. The pion-decay gamma-rays resulting from interaction of accelerated protons with surrounding target material in such sources might be observable above 70 MeV with EGRET (Energetic Gamma-Ray Experimental Telescope) and above 100 GeV with ground-based detectors. Acceleration of protons and expected gamma-ray fluxes from SN1987A, Cyg X-3 type sources and binary pulsars are discussed.

Harding, Alice K.

1990-01-01

302

Solar gamma rays and neutron observations  

NASA Technical Reports Server (NTRS)

The present status of knowledge concerning the impulsive and the continuous emission of solar gamma rays and neutrons is reviewed in the light of the recent solar activity in early August 1972. The gamma ray spectrometer on OSO-7 has observed the sun continuously for most of the activity period except for occultation by the earth. In association with the 2B flare on 4 August 1972 and the 3B flare on 7 August 1972, the monitor provides evidence for solar gamma ray line emission in the energy range from 300 keV to 10 MeV. A summary of all the results available from preliminary analysis of the data will be given. Significant improvements in future experiments can be made with more sensitive instruments and more extensive time coverage of the sun.

Chupp, E. L.; Forrest, D. J.; Suri, A. N.

1972-01-01

303

Ground-Based Gamma Ray Astronomy  

NASA Astrophysics Data System (ADS)

This paper is the write-up of a rapporteur talk given by the author at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil, in 2013. It attempts to summarize results and developments in ground-based gamma-ray observations and instrumentation from among the 300 submissions to the gamma-ray sessions of the meeting. Satellite observations and theoretical developments were covered by a companion rapporteur (Stawarz, L., 33rd ICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-Ray Astronomy, 2013). Any review of this nature is unavoidably subjective and incomplete. Nevertheless, the article should provide a useful status report for those seeking an overview of this exciting and fast-moving field.

Holder, Jamie

2014-10-01

304

Gamma Ray Astronomy with Magnetized Zevatrons  

E-print Network

Nearby sources of cosmic rays up to a ZeV(=10^21 eV) could be observed with a multi-messenger approach including secondary gamma-rays and neutrinos. If cosmic rays above ~10^18 eV are produced in magnetized environments such as galaxy clusters, the flux of secondary gamma-rays below ~1 TeV can be enhanced up to several orders of magnitudes compared to unmagnetized sources. A particular source of enhancement are synchrotron and cascade photons from e^+e^- pairs produced by protons from sources with relatively steep injection spectra proportional to E^-2.6. Such sources should be visible at the same time in ultra-high energy cosmic ray experiments and gamma-ray telescopes.

Eric Armengaud; Guenter Sigl; Francesco Miniati

2005-11-09

305

Galaxies and gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

The nature of the high-energy spectra of several types of active galaxies and their contribution to the measured diffuse gamma-ray emission between 1 and 150 MeV are considered, using X-ray spectra of active galaxies and SAS 2 data regarding the intensity upper limits to the gamma-ray emission above 35 MeV. It is found that a substantial increase in slope of the photon energy spectrum must occur in the low energy gamma-ray region for Seyfert galaxies, BL Lac objects, and emission line galaxies; the power-law spectra observed in the X-ray range must steepen substantially between 50 keV and 50 MeV. In addition, a cosmological integration shows that Seyfert galaxies, BL Lac objects, and quasars may account for most of the 1-150 MeV diffuse background, even without significant evolution.

Bignami, G. F.; Fichtel, C. E.; Hartman, R. C.; Thompson, D. J.

1979-01-01

306

Technology Needs for Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

Gehrels, Neil

2011-01-01

307

The Gamma-Ray Opacity of the Universe & Indirect Measurements of the EBL  

NASA Astrophysics Data System (ADS)

As gamma rays with energies of 20 GeV to 10s of TeV travel over extragalactic distances, their energy-dependent cross section with diffuse photons from the EBL (Extragalactic Background Light) results in electron-positron pair production. Thereby, absorption by the EBL affects the energy spectra of all extragalactic gamma-ray sources, effectively creating an energy dependent gamma-ray horizon.Observations of blazars with current generation satellite- and ground-based telescopes have revealed low gamma-ray opacities, much lower than previously expected. In turn, the energy spectra of blazars at GeV to TeV energies now also provide strong constraints to the EBL in the UV/optical light, the near-IR and the mid-IR.While photons with energies of 1 TeV or larger photons should not reach the observer from a redshift of z ~ 1 or larger, the production of secondary photons via hypothesized new physics (Axion-Like Particles), or cosmic-ray induced cascades could render high-redshift sources observable at TeV energies. Therefore, measurements of the gamma-ray opacity of the universe are also relevant for testing propagation models that are build on physical scenarios beyond gamma-ray absorption via pair production. A completely self-consistent picture, where direct measurements of the EBL or lower limits from galaxy counts, converge with indirect measurements with gamma rays is yet to be achieved with observations.Recent results from gamma-ray observations, their interpretation and caveats will be discussed.

Krennrich, Frank

2014-06-01

308

Measuring planetary neutron albedo fluxes by remote gamma-ray sensing  

NASA Technical Reports Server (NTRS)

In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

Haines, E. L.; Metzger, A. E.

1984-01-01

309

Statistics of cosmological gamma-ray bursts  

NASA Technical Reports Server (NTRS)

A phenomenological model of gamma-ray burst spectra is used to calculate the statistics of gamma-ray bursts originating at cosmological distances. A model of bursters with no source evolution in a q sub 0 = 1/2 Friedmann cosmology is in accord with recent observations of the differential V/Vmax distribution. The data are best fit with an average peak-burst luminosity of (4 +/- 2) x 10 exp 51 ergs/s and a present-day source emissivity of 940 +/- 440 bursts/(10 exp 10 yr) cu Mpc. A spectral test of the cosmological hypothesis is proposed.

Dermer, Charles D.

1992-01-01

310

Noiseless coding for the Gamma Ray spectrometer  

NASA Technical Reports Server (NTRS)

The payload of several future unmanned space missions will include a sophisticated gamma ray spectrometer. Severely constrained data rates during certain portions of these missions could limit the possible science return from this instrument. This report investigates the application of universal noiseless coding techniques to represent gamma ray spectrometer data more efficiently without any loss in data integrity. Performance results demonstrate compression factors from 2.5:1 to 20:1 in comparison to a standard representation. Feasibility was also demonstrated by implementing a microprocessor breadboard coder/decoder using an Intel 8086 processor.

Rice, R.; Lee, J. J.

1985-01-01

311

VHE Gamma-ray Supernova Remnants  

SciTech Connect

Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22

312

Analyzing gamma-ray burst spectral data  

NASA Technical Reports Server (NTRS)

The paper describes an improved method for calculating gamma-ray spectra of gamma-ray bursts. This method is independent of any assumed model for the incident spectrum. In many cases it makes it possible to perform chi-squared model fitting without detailed knowledge of the instrument response functions. The results of extensive calculations using simulated data and realistic response functions are presented; the Backus-Gilbert technique produces model-independent spectral estimates that are quantitatively accurate and easy to calculate.

Loredo, Thomas J.; Epstein, Richard I.

1989-01-01

313

Gamma-ray binaries: pulsars in disguise?  

Microsoft Academic Search

Context: .LS 5039 and LS I+61303 are unique amongst high-mass X-ray binaries (HMXB) for their spatially-resolved radio emission and their counterpart at >GeV gamma-ray energies, canonically attributed to non-thermal particles in an accretion-powered relativistic jet. The only other HMXB known to emit very high-energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond pulsar. Aims: .The purpose is to investigate whether

Guillaume Dubus; Marie Curie

2006-01-01

314

A supersymmetric model of gamma ray bursts  

E-print Network

We propose a model for gamma ray bursts in which a star subject to a high level of fermion degeneracy undergoes a phase transition to a supersymmetric state. The burst is initiated by the transition of fermion pairs to sfermion pairs which, uninhibited by the Pauli exclusion principle, can drop to the ground state of minimum momentum through photon emission. The jet structure is attributed to the Bose statistics of sfermions whereby subsequent sfermion pairs are preferentially emitted into the same state (sfermion amplification by stimulated emission). Bremsstrahlung gamma rays tend to preserve the directional information of the sfermion momenta and are themselves enhanced by stimulated emission.

L. Clavelli; G. Karatheodoris

2005-08-08

315

Gamma-ray Bursts: The Prompt Emission  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts are the largest explosions in the Universe. The radiation is thought to come from a hypernova initiated from the collapse of a massive star or perhaps the merger of two compact stars such s neutron stars and/or black holes. Most of the observed energy is radiated as gamma rays, usually lasting from a fraction of a second to several hundred seconds. The energy generation process is usually referred to as the "central engine". Observed properties of this prompt emission, including spectra, time profiles and durations will be discussed. The history of these observations and future GRB spacecraft will also be described.

Fishman, Jerry

2005-01-01

316

Gamma ray bursts from magnetospheric plasma oscillations  

NASA Technical Reports Server (NTRS)

Neutron star Magnetospheric Plasma Oscillations (MPO), can account for the energetics, decay time scale, and spectra of typical Gamma Ray Bursts (GRBs). The soft photon source is likely to be due to backwarming of the reprocessing boundary by the incipient gamma rays. It is shown that the observed fraction of bursts displaying low energy absorption features may be understood in the context of an MPO model. Moreover, it is found that GRB spectra should display these cyclotron lines about 18 percent of the time, which is consistent with the KONUS and Ginga sets of data.

Melia, Fulvio

1989-01-01

317

Gamma Ray Astronomy With IceCube  

E-print Network

We demonstrate that the South Pole kilometer-scale neutrino observatory IceCube can detect multi-TeV gamma rays continuously over a large fraction of the southern sky. While not as sensitive as pointing atmospheric Cerenkov telescopes, IceCube can roughly match the sensitivity of Milagro. Also, IceCube is complementary to Milagro because it will observe, without interruption, a relatively poorly studied fraction of the southern sky. The information which IceCube must record to function as a gamma ray observatory is only the directions and possibly energies of down-going muons.

Francis Halzen; Dan Hooper

2003-05-13

318

Gamma ray spectrometer for Lunar Scout 2  

NASA Technical Reports Server (NTRS)

We review the current status of the Los Alamos program to develop a high-resolution gamma-ray spectrometer for the Lunar Scout-II mission, which is the second of two Space Exploration Initiative robotic precursor missions to study the Moon. This instrument will measure gamma rays in the energy range of approximately 0.1 - 10 MeV to determine the composition of the lunar surface. The instrument is a high-purity germanium crystal surrounded by an CsI anticoincidence shield and cooled by a split Stirling cycle cryocooler. It will provide the abundance of many elements over the entire lunar surface.

Moss, C. E.; Burt, W. W.; Edwards, B. C.; Martin, R. A.; Nakano, George H.; Reedy, R. C.

1993-01-01

319

Gamma ray astronomy and black hole astrophysics  

NASA Technical Reports Server (NTRS)

The study of soft gamma emissions from black-hole candidates is identified as an important element in understanding black-hole phenomena ranging from stellar-mass black holes to AGNs. The spectra of Cyg X-1 and observations of the Galactic Center are emphasized, since thermal origins and MeV gamma-ray bumps are evident and suggest a thermal-pair cloud picture. MeV gamma-ray observations are suggested for studying black hole astrophysics such as the theorized escaping pair wind, the anticorrelation between the MeV gamma bump and the soft continuum, and the relationship between source compactness and temperature.

Liang, Edison P.

1990-01-01

320

Gamma-ray Burst Skymap Website  

NSDL National Science Digital Library

The Gamma-ray Burst Skymap website automatically updates for each gamma-ray burst as it occurs, whether detected by Swift or other orbiting satellites. For each burst, the location on the sky, star map, constellation and detecting mission are generated automatically. It is then quickly updated by hand to include a written description of the burst properties and scientific significance, as observations continue. Note: In order to view the content of the website, users need to download and install Silverlight on their computers.

2012-12-06

321

Radioactivities and gamma-rays from supernovae  

NASA Technical Reports Server (NTRS)

An account is given of the implications of several calculations relevant to the estimation of gamma-ray signals from various explosive astronomical phenomena. After discussing efforts to constrain the amounts of Ni-57 and Ti-44 produced in SN 1987A, attention is given to the production of Al-27 in massive stars and SNs. A 'delayed detonation' model of type Ia SNs is proposed, and the gamma-ray signal which may be expected when a bare white dwarf collapses directly into a neutron star is discussed.

Woosley, S. E.

1991-01-01

322

Mercury Gamma-rays and Neutron Spectrometer for ESA BepiColompo mission: numerical simulation of neutrons and gamma-rays from Mercury subsurface  

NASA Astrophysics Data System (ADS)

The nuclear instrument MGNS is under development for implementation on the MPO of Bepi-Colombo mission, as the contribution of Federal Space Agency of Russia to this project. In com-parison of gamma-rays spectrometer onboard NASA's Messenger interplanetary probe, which will provide mapping data for northern hemisphere of the planet only because of elliptical orbit, the MGNS onboard MPO will provide global mapping of the planet with similar coverage of southern and northern hemispheres of the Mercury. For analyse chemistry composition of Mercury subsurface we will apply method of as-called remote sensing of neutrons. This method can be use for study celestial body of Solar system without thick atmospheres, like Moon, Mars, Phobos, Mercury etc. by the analysis of induced nuclear gamma-rays and neutron emission. These gamma-rays and neutrons are produced by energetic galactic cosmic rays colliding with nuclei of regolith within a 1-2 meter layer of subsurface. This report will also describe result of numerical simulation flux of neutrons and gamma-rays lines from Mercury subsurface. The simulation was done for four different theoretical models of surface composition (model: ChM, EM, RM and VM) and for four different surface temperature (90 , 300 , 500 and 725 ). We simulate spectrum of neutron flux generated by Mercury surface and flax of gamma-rays for two major line (Al: 7.724 MeV and Si: 3.539 MeV) as function of temperature and subsurface composition.

Kozyrev, S. Alexander; Gunko, Natalya; Gurvits, Leonid; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Sanin, Anton; Shvetsov, Valery; Timoshenko, Genagy; Tretyakov, Vladislav; Tsygan, Anatoly; Vostrukhin, Andrey

323

Ultrahigh Energy Cosmic Rays and Prompt TeV Gamma Rays from Gamma Ray Bursts  

E-print Network

Gamma Ray Bursts (GRBs) have been proposed as one {\\it possible} class of sources of the Ultrahigh Energy Cosmic Ray (UHECR) events observed up to energies $\\gsim10^{20}\\ev$. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV gamma rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.

Pijushpani Bhattacharjee; Nayantara Gupta

2003-05-12

324

Gamma-ray Burst Educator Guide  

NSDL National Science Digital Library

This guide accompanies an educational wallsheet that uses Gamma-ray Bursts as an engagement to teach selected topics in physical science and mathematics. It features four curriculum enhancement activities, background information, assessment information, student worksheets, extension and transfer activities, and detailed information about the physical science and mathematics content standards for grades 9-12.

325

Gamma-ray bursts: Restarting the Engine  

E-print Network

Recent gamma-ray burst observations have revealed late-time, highly energetic events which deviate from the simplest expectations of the standard fireball picture. Instead they may indicate that the central engine is active or restarted at late times. We suggest that fragmentation and subsequent accretion during the collapse of a rapidly rotating stellar core offers a natural mechanism for this.

Andrew King; Paul T. O'Brien; Michael R. Goad; Julian Osborne; Emma Olsson; Kim Page

2005-08-04

326

Solar gamma rays. [of flare origin  

NASA Technical Reports Server (NTRS)

Calculations are presented for the production of gamma-ray lines and continuum emission in solar flares. The interaction models used in the calculations are described, neutron-producing reactions are identified, and formation of the 2.2-MeV line is analyzed. The most important prompt gamma-ray lines that can be observed during solar flares are determined, and the production of gamma-ray continuum emission by electron-proton bremsstrahlung is examined. The results are compared with data on the solar flare of August 4, 1972, to deduce the number and spectrum of accelerated particles at the sun as well as the energy deposited by them in the solar atmosphere. Problems concerning the formation of the 0.51-MeV line by positron annihilation are investigated, and estimates are made for the high-energy gamma-ray and neutron fluxes (at earth) produced by the August 4 flare. The main findings for that flare are: (1) the strongest line, at 2.2 MeV, was due to neutron capture by protons in the photosphere; (2) the intensity of that line depended on the photospheric He-3 abundance; (3) the neutrons were produced mainly in proton-alpha reactions by accelerated particles with energies in excess of 30 MeV/nucleon; and (4) the strongest prompt lines were due to deexcitation of excited states in C-12, O-16, and N-15.

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1975-01-01

327

Measurements of Gamma-Ray Attenuation Coefficients  

Microsoft Academic Search

Measurements have been made to determine gamma-ray attenuation coefficients very accurately by using an extremely-narrow-collimated-beam transmission method which effectively excluded corrections due to small-angle and multiple scattering of photons. The measured mass attenuation coefficients with maximum errors less than 3% for 34 elements in the range from hydrogen to lead are given.

B. Goswami; N. Chaudhuri

1973-01-01

328

AGILE and gamma-ray astrophysics  

NASA Astrophysics Data System (ADS)

The study of ? rays is fundamental for our understanding of the universe: ? rays probe the most energetic phenomena occurring in nature, and several signatures of new physics are associated with the emission of ? rays. The main science objectives and the status of the new generation high-energy gamma-ray astrophysics experiment AGILE are presented.

Longo, F.; Argan, A.; Auricchio, N.; Barbiellini, G.; Bulgarelli, A.; Caraveo, P.; Celesti, E.; Chen, A.; Cocco, V.; Costa, E.; Di Cocco, G.; Fedel, G.; Feroci, M.; Fiorini, M.; Froysland, T.; Galli, M.; Gianotti, F.; Giuliani, A.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Mauri, A.; Marisaldi, M.; Mereghetti, S.; Morelli, E.; Morselli, A.; Pacciani, L.; Paladin, F.; Pellizzoni, A.; Perotti, F.; Picozza, P.; Pittori, C.; Pontoni, C.; Porrovecchio, J.; Preger, B.; Prest, M.; Rapisarda, M.; Rossi, E.; Rubini, A.; Soffitta, P.; Tavani, M.; Traci, A.; Trifoglio, M.; Vallazza, E.; Vercellone, S.; Zanello, D.

2003-09-01

329

Gamma-Ray Telescope and Uncertainty Principle  

ERIC Educational Resources Information Center

Heisenberg's Uncertainty Principle is one of the important basic principles of quantum mechanics. In most of the books on quantum mechanics, this uncertainty principle is generally illustrated with the help of a gamma ray microscope, wherein neither the image formation criterion nor the lens properties are taken into account. Thus a better

Shivalingaswamy, T.; Kagali, B. A.

2012-01-01

330

Delayed Nickel Decay in Gamma Ray Bursts  

E-print Network

Recently observed emission lines in the X-ray afterglow of gamma ray bursts suggest that iron group elements are either produced in the gamma ray burst, or are present nearby. If this material is the product of a thermonuclear burn, then such material would be expected to be rich in Nickel-56. If the nickel remains partially ionized, this prevents the electron capture reaction normally associated with the decay of Nickel-56, dramatically increasing the decay timescale. Here we examine the consequences of rapid ejection of a fraction of a solar mass of iron group material from the center of a collapsar/hypernova. The exact rate of decay then depends on the details of the ionization and therefore the ejection process. Future observations of iron, nickel and cobalt lines can be used to diagnose the origin of these elements and to better understand the astrophysical site of gamma ray bursts. In this model, the X-ray lines of these iron-group elements could be detected in suspected hypernovae that did not produce an observable gamma ray burst due to beaming.

G. C. McLaughlin; R. A. M. J. Wijers

2002-05-19

331

The Supernova Gamma-Ray Burst Connection  

Microsoft Academic Search

The chief distinction between ordinary supernovae and long-soft gamma-ray bursts (GRBs) is the degree of differential rotation in the inner several solar masses when a massive star dies, and GRBs are rare mainly because of the difficulty achieving the necessary high rotation rate. Models that do provide the necessary angular momentum are discussed, with emphasis on a new single star

Stan Woosley; A. Heger

2006-01-01

332

Gamma-Ray Burst Environments and Progenitors  

Microsoft Academic Search

Likely progenitors for gamma-ray bursts (GRBs) are the mergers of compact objects or the explosions of massive stars. These two cases have distinctive environments for the GRB afterglow: the compact object explosions occur in the interstellar medium (ISM) and those of massive stars occur in the preburst stellar wind. We calculate the expected afterglow for a burst in a Wolf-Rayet

Roger A. Chevalier; Zhi-Yun Li

1999-01-01

333

Gamma-Ray Bursts The Second Revolution  

Microsoft Academic Search

Gamma-ray bursts GRBs are among the most mysterious astronomical phenomenon ever discovered. Unlike most astronomical discoveries which were explained within weeks or months after their initial discovery, GRBs remain a puzzle for more than thirty years. During the last decade our understanding of GRBs has undergone two major revolutions. First, BATSE discovered that GRBs are distributed isotropically over the sky

Tsvi Piran

1998-01-01

334

Three Types of Gamma-Ray Bursts  

Microsoft Academic Search

A multivariate analysis of gamma-ray burst (GRB) bulk properties is presented to discriminate between distinct classes of GRBs. Several variables representing burst duration, fluence, and spectral hardness are considered. Two multivariate clustering procedures are used on a sample of 797 bursts from the Third BATSE Catalog, a nonparametric average linkage hierarchical agglomerative clustering procedure validated with Wilks' Lambda^* and other

Soma Mukherjee; Eric D. Feigelson; Gutti Jogesh Babu; Fionn Murtagh; Chris Fraley; Adrian Raftery

1998-01-01

335

Gamma Ray Burst Detectives (Elementary School)  

NSDL National Science Digital Library

This interactive resource invites students to join NASA to find the source of gamma ray bursts, the single biggest explosions in the Universe since the Big Bang. The web site features an animation, information on three possible star sources, and a check yes or no for each star with feedback.

2010-04-28

336

Gamma Ray Burst Detectives (High School)  

NSDL National Science Digital Library

>This WPSU interactive resource invites students to join NASA to find the source of gamma ray bursts, the single biggest explosions in the Universe since the Big Bang by exploring three aspects of the death of stars: energy, duration, and variability.

WPSU

2011-04-27

337

Accretion Models of Gamma-Ray Bursts  

Microsoft Academic Search

Many models of gamma-ray bursts (GRBs) involve accretion onto a compact object, usually a black hole, at a mass accretion rate on the order of a fraction of a solar mass per second. If the accretion disk is larger than a few tens or hundreds of Schwarzschild radii, the accretion will proceed via a convection-dominated accretion flow (CDAF) in which

Ramesh Narayan; Tsvi Piran; Pawan Kumar

2001-01-01

338

Theories of Gamma-Ray Bursts  

Microsoft Academic Search

The gamma ray burst phenomenon is reviewed from a theoretical point of view, with emphasis on the fireball shock scenario of the prompt emission and the longer wavelength afterglow. Recent progress and issues are discussed, including spectral-temporal evolution, localizations, jets, spectral lines, environmental and cosmological aspects, as well as some prospects for future experiments in both electromagnetic and nonelectromagnetic channels.

P. Mszros

2002-01-01

339

The Gamma-Ray Observatory: An overview  

NASA Technical Reports Server (NTRS)

The Gamma-Ray Observatory (GRO) is a 16,000 kg spacecraft containing four instruments which span almost six decades of energy from about 50 keV to about 30 GeV. It will provide the first opportunity to make simultaneous observations over such a broad band of gamma-ray energies. GRO is assembled and undergoing testing prior to its scheduled June 4, 1990 launch aboard the Space Shuttle. The orbit will be circular with an altitude of 450 km and with an inclination of 28 degrees. Data will be recorded at 32 kilobits per second and dumped once per orbit via the Tracking and Data Relay Satellite System (TDRSS). The spacecraft is three-axis stabilized and timing will be maintained to .1 ms. The observing schedule will begin with an all sky survey, consisting of 30 two week pointings, covering the first 15 months of science operations. Following observations will emphasize source studies and deep searches. Originally selected as a Principal Class spacecraft with a two year mission, extension of the mission to six to ten years makes a vigorous Guest Investigator Program both possible and desirable. Such a program will be fully in place by the third year of the mission, with limited opportunities earlier. Each of the four instruments has a capability for observing both gamma-ray bursts and solar flare gamma-rays, and there is some solar neutron capability. Correlated observations with those at other wavelengths is also receiving considerable attention in the mission planning.

Kniffen, Donald A.

1989-01-01

340

High redshift Gamma-Ray Bursts  

E-print Network

Ten years of operations of the Swift satellite have allow us to collect a small sample of long Gamma-Ray Bursts (GRBs) at redshift larger than six. I will review here the present status of this research field and discuss the possible use of GRBs as a fundamental new tool to explore the early Universe, complementary to quasar and galaxy surveys.

Salvaterra, R

2015-01-01

341

New shield for gamma-ray spectrometry  

NASA Technical Reports Server (NTRS)

Gamma-ray shield that can be evacuated, refilled with a clean gas, and pressurized for exclusion of airborne radioactive contaminants effectively lowers background noise. Under working conditions, repeated evacuation and filling procedures have not adversely affected the sensitivity and resolution of the crystal detector.

Brar, S. S.; Gustafson, P. F.; Nelson, D. M.

1969-01-01

342

Neutron production in terrestrial gamma ray flashes  

Microsoft Academic Search

Terrestrial gamma ray flashes (TGFs) are brief bursts of photons with energies up to 20 MeV typically observed in association with lightning. Such energetic photons may undergo photonuclear reactions with nontrivial cross section in the vicinity of the giant dipole resonance. Pulses of neutrons have been observed experimentally in coincidence with lightning, suggesting such reactions are observable. We present simulations

B. E. Carlson; N. G. Lehtinen

2010-01-01

343

First RHESSI terrestrial gamma ray flash catalog  

Microsoft Academic Search

We present a summary of data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) terrestrial gamma ray flash (TGF) catalog. We describe the RHESSI search algorithm and discuss its limitations due to its design emphasis on cleanliness rather than completeness. This search algorithm has identified 820 TGFs between March of 2002 and February of 2008. Radiation damage to

B. W. Grefenstette; D. M. Smith; B. J. Hazelton; L. I. Lopez

2009-01-01

344

Study of gamma-ray strength functions  

SciTech Connect

The use of gamma-ray strength function systematics to calculate neutron capture cross sections and capture gamma-ray spectra is discussed. The ratio of the average capture width, GAMMA/sub ..gamma../-bar, to the average level spacing, D/sub obs/, both at the neutron separation energy, can be derived from such systematics with much less uncertainty than from separate systematics for values of GAMMA/sub ..gamma../-bar and D/sub obs/. In particular, the E1 gamma-ray strength function is defined in terms of the giant dipole resonance (GDR). The GDR line shape is modeled with the usual Lorentzian function and also with a new energy-dependent, Breit-Wigner (EDBW) function. This latter form is further parameterized in terms of two overlapping resonances, even for nuclei where photonuclear measurements do not resolve two peaks. In the mass ranges studied, such modeling is successful for all nuclei away from the N = 50 closed neutron shell. Near the N = 50 shell, a one-peak EDBW appears to be more appropriate. Examples of calculated neutron capture excitation functions and capture gamma-ray spectra using the EDBW form are given for target nuclei in the mass-90 region and also in the Ta-Au mass region. 20 figures.

Gardner, D.G.; Gardner, M.A.; Dietrich, F.S.

1980-08-07

345

Persistent Counterparts to Gamma-Ray Bursts  

Microsoft Academic Search

The recent discovery of persistent gamma-ray burst (GRB) counterparts at lower frequencies permits several important conclusions to be drawn. The spectrum of GRB 970508 is not consistent with an external shock origin for both the prompt GRB and the persistent emission, suggesting that at least the prompt radiation is produced by internal shocks. Comparisons among three GRBs with counterparts (or

J. I. Katz; T. Piran

1997-01-01

346

GAMMA RAY IMAGING FOR ENVIRONMENTAL REMEDIATION  

EPA Science Inventory

The research is a three year development program to apply high resolution gamma-ray imaging technologies to environmental remediation of radioactive hazards. High resolution, position-sensitive germanium detectors are being developed at the Naval Research Laboratory for space app...

347

High energy gamma-ray astronomy  

Microsoft Academic Search

The physics results of high energy gamma-ray astronomy are reported,\\u000aemphasizing recent achievements with ground-based detectors. This includes some\\u000aof the instrumental developments and latest projects. The fundamental\\u000acontribution of the field to the question of Cosmic Ray origin is highlighted.

H. J. Vlk

2005-01-01

348

High Energy Gamma-Ray Astronomy  

E-print Network

The physics results of high energy gamma-ray astronomy are reported, emphasizing recent achievements with ground-based detectors. This includes some of the instrumental developments and latest projects. The fundamental contribution of the field to the question of Cosmic Ray origin is highlighted.

H. J. Voelk

2004-01-19

349

Gamma-Ray Astronomy of Cosmic Rays  

E-print Network

Many of the basic problems in the astrophysics of charged Cosmic Rays remain on principle unresolved by in situ observations in the Solar System due to the chaotic nature of the propagation of these particles in Interstellar space. This concerns the existence and the nature of localized individual particle sources as well as the transport in the Galaxy and establishes the need for astronomical observations of secondary gamma-rays. The only exception may be the highest energy particles at energies around $10^{20}$ eV which possibly reach us on straight line orbits from their production sites. Recently such gamma-ray observations, both in space and on the ground, have made great progress even though the instrumental sensitivities are still low. It is argued that two basic questions, regarding first of all the Supernova Remnant source hypothesis and secondly the contributions to the diffuse gamma-ray background, have come close to an empirical resolution. Apart from motivations deriving from extragalactic astronomy this expectation is at the root of the construction of a new generation of high-sensitivity gamma-ray instruments. As a representative example the H.E.S.S. array of atmospheric Cherenkov telescopes is described.

Heinrich Voelk

2002-02-22

350

Gamma Ray and Neutron Detector Interactive  

NSDL National Science Digital Library

This product illustrates how scientists learn about the composition of an asteroid by studying energy and neutrons that emanate from it. The Dawn spacecraft contains three instruments -- the Gamma Ray and Neutro Detector (GRaND), the Visible Infrared Spectrometer, and the Framing Camera -- that will provide answers to questions about the formation and evolution of the early solar system.

John Ristvey

2009-04-22

351

Investigation of gamma rays from the galactic center  

NASA Technical Reports Server (NTRS)

Data from Argentine balloon flights made to investigate gamma ray emission from the galactic center are summarized. Data are also summarized from a Palestine, Texas balloon flight to measure gamma rays from NP 0532 and Crab Nebulae.

Helmken, H. F.

1973-01-01

352

Swift's 500th Gamma Ray Burst - Duration: 1:04.  

NASA Video Gallery

On April 13, 2010, NASA's Swift Gamma-ray Burst Explorer satellite discovered its 500th burst. Swift's main job is to quickly localize each gamma-ray burst (GRB), report its position so that others...

353

Gamma Ray Telescope Senses High-Energy Radiation  

NSDL National Science Digital Library

This video from NASA describes the GLAST satellite, which is equipped with a gamma-ray telescope, and shares some background about the kinds of extreme universal phenomena indicated by the presence of gamma rays.

WNET

2011-11-02

354

GeV-TeV Gamma-ray Astronomy  

E-print Network

Recent results of GeV and TeV observations of gamma-rays from the Universe are briefly reviewed. Topics include observational technique, diffuse gamma-rays, pulsars, unidentified sources, plerions, supernova remnants and AGNs.

Masaki Mori

2001-08-29

355

Gamma ray lines from the Galactic Center and gamma ray transients  

NASA Technical Reports Server (NTRS)

The observations and interpretations of cosmic (nonsolar) gamma ray lines are discussed. The most prominent of these lines is the e(+)e(-) annihilation line which was observed from the Galactic Center and from several gamma ray transients. At the Galactic Center the e(+)e(-) pairs are probably produced by an accreting massive black hole (solar mass of approximately one million) and annihilate within the central light year to produce a line at almost exactly 0.511 MeV. In gamma ray transients the annihilation line is redshifted by factors consistent with neutron star surface redshifts. Other observed transient gamma ray lines appear to be due to cyclotron absorption in the strong magnetic fields of neutron stars, and nuclear deexcitations and neutron capture, which could also occur on or around these objects.

Ramaty, R.; Leiter, D.; Lingenfelter, R. E.

1981-01-01

356

Studying the High Energy Gamma Ray Sky with Gamma Ray Large Area Space Telescope (GLAST)  

NASA Technical Reports Server (NTRS)

Building on the success of the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the Gamma Ray Large Area Space Telescope (GLAST) will make a major step in the study of such subjects as blazars, gamma Ray bursts, the search for dark matter, supernova remnants, pulsars, diffuse radiation, and unidentified high energy sources. The instrument will be built on new and mature detector technologies such as silicon strip detectors, low-power low-noise LSI, and a multilevel data acquisition system. GLAST is in the research and development phase, and one full tower (of 25 total) is now being built in collaborating institutes. The prototype tower will be tested thoroughly at Stanford Linear Accelerator Center (SLAC) in the fall of 1999.

Kamae, T.; Ohsugi, T.; Thompson, D. J.; Watanabe, K.

1998-01-01

357

Observations of cosmic gamma ray sources and their contribution to the diffuse gamma ray background  

SciTech Connect

The objective is to study soft gamma ray emission in the 0.1 to 10 MeV energy band for selected active galactic nuclei and explore how much they contribute to the total diffuse gamma ray background. A series of imaging observations of extragalactic objects in the low energy gamma-ray region were carried out by the Coded Aperture Directional Gamma-ray Telescope (DGT). The DGT was successfully flown at stratospheric balloon altitudes, and observations were made of the Crab, NGC 1275, MKN 421, and NGC 4151. The measured Crab spectrum is consistent with a featureless power-law of the form. Significant emission was detected up to 500 keV from the Seyfert galaxy, NGC 4151. To increase the total sky exposure the extragalactic field images were analyzed, including the 3C 273 region, obtained by the DGT.

Bhattacharya, D.

1990-01-01

358

Advanced Modeling of Prompt Fission Neutrons and Gamma Rays  

NASA Astrophysics Data System (ADS)

Prompt fission neutrons and gamma rays are computed using a Monte Carlo treatment of the statistical evaporation of the excited primary fission fragments. The assumption of two fragments in thermal equilibrium at the time of neutron emission is addressed by studying the neutron multiplicity as a function of fragment mass. Results for the neutron-induced fission of 235U are discussed, for incident neutron energies from 0.5 to 5.5 MeV. Recent experimental data on the fission fragment yields as a function of mass and total kinetic energy are used as input data.

Talou, P.; Kawano, T.

2010-03-01

359

Photon-photon refraction for TeV gamma rays  

E-print Network

The propagation of TeV gamma rays can be strongly modified by B-field induced conversion to axion-like particles. The conversion rate depends on the photon dispersion relation which, at such high energies, is dominated by the B-field itself through the QED photon-photon interaction. However, ambient photons also contribute and the cosmic microwave background (CMB) dominates when B electron+positron it is the extra-galactic background light. Local radiation fields, e.g., the galactic star light, can be more important for dispersion than the CMB.

Alexandra Dobrynina; Alexander Kartavtsev; Georg Raffelt

2014-12-15

360

Investigations in cosmic and gamma ray astronomy and nuclear instruments  

NASA Technical Reports Server (NTRS)

The Nuclear Radiation Monitor (NRM) is flying on the Spacelab 2 vehicle as part of a set of instrumentation designed to measure the ambient physical environment on Spacelab in orbit. The NRM measures the natural and induced gamma ray activity. The instrument is constituted of a 25 sq in (NaI (T1)) crystal viewed with a single phototube and surrounded by a plastic anticoincidence shield. It is mounted on a pedestal and placed, with its electronics, on the Spacelab pallet. The detector head was designed and a development model fabricated and tested. Extensive software studies for on board and GSE microprocessors for use with the NRM were also made.

Gregory, J. C.

1982-01-01

361

The origin and implications of gamma rays from solar flares  

NASA Technical Reports Server (NTRS)

Solar flares studied in the gamma ray region provide essential information on accelerated nuclei that can be obtained in no other way. A multitude of physical processes, such as particle acceleration, nuclear reactions, positron and neutron physics, and kinematical line broadening, come into consideration at gamma ray energies. Gamma ray observations are complementary to hard X ray observations, since both provide information on accelerated particles. It appears that only in the gamma ray region do these particles produce distinct spectral lines.

Ramaty, R.

1975-01-01

362

Simultaneous optical/gamma-ray observations of GRBs  

NASA Technical Reports Server (NTRS)

Details on the project to search for serendipitous time correlated optical photographic observations of Gamma Ray Bursters (GRB's) are presented. The ongoing photographic observations at nine observatories are used to look for plates which were exposed simultaneously with a gamma ray burst detected by the gamma ray instrument team (BATSE) and contain the burst position. The results for the first two years of the gamma ray instrument team operation are presented.

Greiner, J.; Wenzel, W.; Hudec, R.; Moskalenko, E. I.; Metlov, V.; Chernych, N. S.; Getman, V. S.; Ziener, Rainer; Birkle, K.; Bade, N.

1994-01-01

363

Gamma-ray astronomy--A status report  

NASA Technical Reports Server (NTRS)

Gamma-rays provide us with powerful insight into the highest energy processes occurring in the cosmos. This review highlights some of the progress in our understanding of gamma-ray astronomy that has been enabled by new data from GRANAT and the Compton Gamma-Ray Observaatory, and suggests requirements for future progress. In particular, the unique role of the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) mission and concurrent multiwavelength observations is highlighted.

Holt, Stephen S.

1994-01-01

364

Fermi Gamma-Ray Imaging of a Radio Galaxy  

Microsoft Academic Search

The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; J. Bregeon; A. Brez; M. Brigida; P. Bruel; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; E. Cavazzuti; C. Cecchi; . elik; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; S. Colafrancesco; L. R. Cominsky; J. Conrad; L. Costamante; S. Cutini; D. S. Davis; C. D. Dermer; A. de Angelis; F. de Palma; S. W. Digel; E. do Couto e Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; J. Finke; W. B. Focke; P. Fortin; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; M. Georganopoulos; S. Germani; B. Giebels; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; I. A. Grenier; J. E. Grove; L. Guillemot; S. Guiriec; Y. Hanabata; A. K. Harding; M. Hayashida; E. Hays; R. E. Hughes; M. S. Jackson; Jhannesson G; S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Kndlseder; M. L. Kocian; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; M. N. Mazziotta; W. McConville; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; D. Parent; V. Pelassa; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rain; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; T. Reposeur; S. Ritz; L. S. Rochester; A. Y. Rodriguez; R. W. Romani; M. Roth; F. Ryde; H. F.-W. Sadrozinski; R. Sambruna; D. Sanchez; A. Sander; P. M. Saz Parkinson; J. D. Scargle; C. Sgr; J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; J.-L. Starck; L. Stawarz; M. S. Strickman; D. J. Suson; H. Takahashi; T. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Usher Uchiyama T. L; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; E. Wallace; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler; M. J. Hardcastle; D. Kazanas

2010-01-01

365

Gamma-ray line investigations with the Durham gamma-ray spectrometer  

Microsoft Academic Search

A description is presented of a program undertaken to investigate gamma-ray lines with the aid of an actively shielded high purity Ge detector cooled by liquid nitrogen. The active NaI(Tl) shielding elements limit the opening angle of the telescope to 5.2 deg. The basic crystal has a gamma-ray detection efficiency of 23% relative to a standard 3 in. x 3

C. A. Ayre; A. Owens; W. M. Summers; M. G. Thompson; P. N. Bhat

1981-01-01

366

CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy  

Microsoft Academic Search

We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and

T. H. Prettyman; W. C. Feldman; K. R. Fuller; S. A. Storms; S. A. Soldner; David J. Lawrence; M. C. Browne; C. E. Moss

2001-01-01

367

Gamma-ray burst observations by the HEAO3 high-resolution gamma-ray spectrometer  

Microsoft Academic Search

Observations of cosmic gamma-ray bursts with the JPL High-Resolution Gamma-Ray Spectrometer on HEAO-3 are discussed. Two bursts seen on 1979 November 16 are of particular interest. The first event occurred at 14:16:41 UT and lasted for eight seconds. This event was detected only by the instruments five CsI shield segments. The second event occurred 61 sec later, at 14:17:42 UT,

Wm. A. Wheaton; James C. Ling; William A. Mahoney; Guenter R. Riegler; Allan S. Jacobson

1982-01-01

368

Gamma-Ray Lenses for Astrophysicsand the Gamma-Ray Imager Mission GRI  

Microsoft Academic Search

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear

Cornelia B. Wunderer; Peter v. Ballmoos; Nicolas Barriere; Angela Bazzano; Steven E. Boggs; Finn Christensen; Filippo Frontera; Margarida Hernanz; Jrgen Knodlseder; Andreas Zoglauer

2009-01-01

369

Gamma ray spectroscopy in astrophysics: Solar gamma ray astronomy on solar maximum mission. [experimental design  

NASA Technical Reports Server (NTRS)

The SMM gamma ray experiment and the important scientific capabilities of the instrument are discussed. The flare size detectable as a function of spectrum integration time was studied. A preliminary estimate indicates that a solar gamma ray line at 4.4 MeV one-fifth the intensity of that believed to have been emitted on 4 August 1972 can be detected in approximately 1000 sec with a confidence level of 99%.

Forrest, D. J.

1978-01-01

370

The project EGRET (energetic gamma-ray experiment telescope) on NASA's Gamma-Ray Observatory GRO  

Microsoft Academic Search

The Gamma Ray Observatory (GRO) is currently planned for a launch from the space shuttle in 1990. After the long hiatus in high-energy gamma-ray astronomy since the end of the COS-B mission in 1982, the Soviet missions Granat and Gamma-1 and the NASA mission GRO will resume observations in the energy range from below 100 keV and extending to above

G. Kanbach; D. L. Bertsch; A. Favale; C. E. Fichtel; R. C. Hartman; R. Hofstadter; E. B. Hughes; S. D. Hunter; B. W. Hughlock; D. A. Kniffen; Y. C. Lin; H. A. Mayer-Hasselwander; P. L. Nolan; K. Pinkau; H. Rothermel; E. Schneid; M. Sommer; D. J. Thompson

1989-01-01

371

Gamma-ray Emission from the gamma-ray-loud BL Lac Objects  

Microsoft Academic Search

Using the HST observation data of BL Lac objects by Urry et al. and gamma-ray observation data, we find that there is a correlation between Fgamma and Fnuclei for gamma-ray-loud BL Lac objects (correlation coefficients: gamma=0.63, p=4.0 10-2), but no correlation between Fgamma and FOhost, where FOnuclei and FOhost are the fluxes of nuclei and host galaxy in V-band.

Guang-Zhong Xie; Ben-Zhong Dai; En-Wei Liang; Zhao-Hua Xie

2001-01-01

372

Lunar Elemental Abundances from Gamma-Ray and Neutron Measurements  

NASA Astrophysics Data System (ADS)

The determination of elemental abundances is one of the highest science objectives of most lunar missions. Such multi-element abundances, ratios, or maps should include results for elements that are diagnostic or important in lunar processes, including heat-producing elements (such as K and Th), important incompatible elements (Th and rare earth elements), H (for polar deposits and regolith maturity), and key variable elements in major lunar provinces (such as Fe and Ti in the maria). Both neutron and gamma-ray spectroscopy can be used to infer elemental abundances; the two complement each other. These elemental abundances need to be determined with high accuracy and precision from measurements such as those made by the gamma-ray spectrometer (GRS) and neutron spectrometers (NS) on Lunar Prospector. As presented here, a series of steps, computer codes, and nuclear databases are needed to properly convert the raw gamma-ray and neutron measurements into good elemental abundances, ratios, and/or maps. Lunar Prospector (LP) is the first planetary mission that has measured neutrons escaping from a planet other than the Earth. The neutron spectrometers on Lunar Prospector measured a wide range of neutron energies. The ability to measure neutrons with thermal (E < 0.1 eV), epithermal (E about equal 0.1 - 1000 eV), and fast (E about 0.1-10 MeV) energies maximizes the scientific return, being especially sensitive to both H (using epithermal neutrons) and thermal-neutron-absorbing elements. Neutrons are made in the lunar surface by the interaction of galactic-cosmic-ray (GCR) particles with the atomic nuclei in the surface. Most neutrons are produced with energies above about 0.1 MeV. The flux of fast neutrons in and escaping from the Moon depends on es the intensity of the cosmic rays (which vary with solar activity) and the elemental composition of the surface. Variations in the elemental composition of the lunar surface can affect the flux of fast neutrons by about 25% , with Ti and Fe emitting more fast neutrons than light elements like O and Si. Most elements moderate neutrons to thermal energies at similar rates. The main exception is when neutrons scatter from H, in which case neutrons can be rapidly thermalized. The cross sections for the absorption of thermal neutrons can vary widely among elements, with major elements like Ti and Fe having high-capture cross sections. Some trace elements, such as Sm and Gd, have such large neutron-absorption cross sections that, despite their low abundances, can absorb significant amounts of thermal neutrons in the Moon. Because the processes affecting neutrons are complicated, good modeling is needed to properly extract elemental information from measured neutron fluxes. The LAHET Code System (LCS) can be use to calculate neutron fluxes from GCR interactions in the Moon. Lunar Gamma-Ray Spectroscopy: The main sources of planetary gamma-rays are the decay of the naturally occurring radioactive isotopes of K, Th, and U and the interactions of GCRs with atomic nuclei in the planet's surface. Most "cosmogenic" gamma-rays are produced by fast and thermal neutrons made in the planet's surface by GCRs, and their production rates can vary with time. Over 300 gamma-ray lines have been identified that can be emitted from planetary surfaces by a variety of production mechanisms. There exist nuclear databases that can be used to identify and quantify other gamma-ray lines. Use will be made of gamma-rays from major elements, particularly those from Si and O, that have not been routinely used in the past. The fluxes of gamma-rays from a given element can vary depending on many factors besides the concentration of that element. For example, the fluxes of neutron-capture gamma-rays in the planetary region of interest depend on (1) the total cross section for elements to absorb thermalized neutrons and (2) the H content of the top meter of the surface. The fluxes of the fast neutrons that induce inelastic-scattering and other nonelastic-scattering reactions can vary with the composition of

Reedy, R. C.; Vaniman, D. T.

1999-01-01

373

BASIC GAMMA-RAY DATA FOR ART HEAT DEPOSITION CALCULATIONS  

Microsoft Academic Search

Heat deposition rates from gamma rays in the ART were required for ; thermal stress calculations. The basic physical data necessary in determining ; these rates are reported. U²³⁵ prompt gamma rays, capture and decay gammas ; in the fuel and reflector, aad gamma rays from inelastic scattering of neutrons ; are included. Buildup factors and absorption coefficients are considered.

H. W. Bertini; C. M. Copenhaver; A. M. Perry; R. B. Stevenson

1956-01-01

374

Gamma-Ray Telescopes: 400 Years of Astronomical Telescopes  

NASA Technical Reports Server (NTRS)

The last half-century has seen dramatic developments in gamma-ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as gamma-ray bursts, blazars, Galactic transients, and the Galactic distribution of Al-26.

Gehrels, Neil; Cannizzo, John K.

2010-01-01

375

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-print Network

as it was happening, which had been the holy grail of gamma-ray burst astronomy for a quarter of a century. FromThe Biggest Bangs The Mystery of Gamma-Ray Bursts, The Most Violent Explosions in The Universe J. I. Did a Gamma-Ray Burst Kill the Dinosaurs? Will a Burst Kill Us? #15; Glossary #15; Sources #15; Index

Katz, Jonathan I.

376

Gamma-Ray Bursts Nuclear Test Ban Treaty, 1963  

E-print Network

Lecture 18 Gamma-Ray Bursts #12;Nuclear Test Ban Treaty, 1963 First Vela satellite pair launched and their predecessors, Vela 4, discovered the first gamma-ray bursts. The discovery was announced by Klebesadel, Strong, and Olson (ApJ, 182, 85) in 1973. #12;First Gamma-Ray Burst The Vela 5 satellites functioned from July, 1969

Harrison, Thomas

377

The Compton Effect--Compton Scattering and Gamma Ray Spectroscopy  

E-print Network

The Compton Effect-- Compton Scattering and Gamma Ray Spectroscopy by Dr. James E. Parks Department and procedures for measuring gamma-ray energy distributions, (7) to learn about photomultipliers the interactions of high energy, electromagnetic photon radiation with materials in general. Gamma rays are high

Dai, Pengcheng

378

Very High-Energy Gamma-Ray Sources.  

ERIC Educational Resources Information Center

Discusses topics related to high-energy, gamma-ray astronomy (including cosmic radiation, gamma-ray detectors, high-energy gamma-ray sources, and others). Also considers motivation for the development of this field, the principal results to date, and future prospects. (JN)

Weekes, Trevor C.

1986-01-01

379

MUTATIONS INDUCED BY URBAN AIR AND DRINKING WATER: DO THEY LEAVE A MUTATIONAL SIGNATURE IN HUMAN TUMORS?  

EPA Science Inventory

Mutations Induced by Urban Air and Drinking Water: Do They Leave a Mutational Signature in Human Tumors? Mutation spectra of complex environmental mixtures have been determined thus far only in Salmonella. We have determined mutation spectra for the particulate organics ...

380

Gamma-ray emitting radio galaxies  

NASA Astrophysics Data System (ADS)

A number of radio galaxies has been detected by Fermi/LAT in the gamma-ray domain. The question remains why these objects, where the relativistic jet is not pointed at the observer, are observable gamma-ray emitters in the first place, and what distinguishes them from the vast majority of gamma-ray silent radio galaxies. In some cases, like Cen A and M 87, these objects have been seen even in the TeV range by Cherenkov telescopes. Whereas the gamma-ray emission is likely to be connected with the non-thermal jet emission, dominating also the radio band, the situation is less clear at hard X-rays. While the smoothly curved continuum emission and the overall spectral energy distribution indicate non-thermal emission, other features such as the iron line emission and the low variability appear to be rather of Seyfert type, i.e. created in the accretion disk and corona around the central black hole. We analysed the case of the 15 gamma-ray detected radio galaxies known so far. Using X-ray data from the soft X-ray band (e.g. Chandra, XMM-Newton, Suzaku/XIS) to the hard X-ray band (e.g. Suzaku/PIN, INTEGRAL, Swift) we determine the emission processes dominant between 0.5 keV and several 100 keV. In the case of M87 we report, for the first time, a detection in the 10-50 keV band. In most cases, the X-ray band of gamma-ray detected radio galaxies is produced in the inverse Compton branch, which can be seen in the fact that most have X-ray spectrum with a photon index <2.0 (i.e. a rising spectral energy distribution). Three different origins of the X-ray flux can be identified. The emission can be purely non-thermal and caused by the jet, as in the case of M 87, or thermal inverse Compton emission from the Seyfert type core (Cen A), or appears to be a superposition of non-thermal and thermal inverse Compton emission, as we observe in 3C 111. The iron fluorescence line Fe Kalpha is visible in the X-ray spectra of some, but not all radio galaxies. In three cases (OH-342, M87, and 3C 78) the X-ray emission is dominated by synchrotron processes, as indicated by X-ray photon indices >2.0. Gamma-ray bright radio galaxies host all kinds of AGN cores, Seyfert 1 and 2, BL Lacs, and also LINER, and can appear as FR-I and FR-II types. But the overall emission as seen in the spectral energy distribution can be modeled by a simple synchrotron self Compton model as typical for BL Lac objects, i.e. no additional strong photon field giving rise to an external Compton component is required. This indicates that the site of the gamma-ray emission is not exposed to a luminous broad line region or other dense photon field, as observed for example in FSRQ. Based on the number counts, it appears that within the Fermi/LAT data there are a dozen gamma-ray bright radio galaxies already detected but not yet identified as radio galaxies.

Beckmann, Volker; Soldi, Simona; De Jong, Sandra

381

Simulation of prompt gamma-ray emission during proton radiotherapy  

NASA Astrophysics Data System (ADS)

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector designs. Also, the gamma production cross-sections may be incorporated as prior knowledge in the reconstruction of the proton range from the measurements. In this work, we performed simulations of proton-induced nuclear reactions with the main elements of human tissue, carbon-12, oxygen-16 and nitrogen-14, using the nuclear reaction models of the GEANT4 and MCNP6 Monte Carlo codes and the dedicated nuclear reaction codes TALYS and EMPIRE. For each code, we made an effort to optimize the input parameters and model selection. The results of the models were compared to available experimental data of discrete gamma line cross-sections. Overall, the dedicated nuclear reaction codes reproduced the experimental data more consistently, while the Monte Carlo codes showed larger discrepancies for a number of gamma lines. The model differences lead to a variation of the total gamma production near the end of the proton range by a factor of about 2. These results indicate a need for additional theoretical and experimental study of proton-induced gamma emission in human tissue.

Verburg, Joost M.; Shih, Helen A.; Seco, Joao

2012-09-01

382

Simulation of prompt gamma-ray emission during proton radiotherapy.  

PubMed

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector designs. Also, the gamma production cross-sections may be incorporated as prior knowledge in the reconstruction of the proton range from the measurements. In this work, we performed simulations of proton-induced nuclear reactions with the main elements of human tissue, carbon-12, oxygen-16 and nitrogen-14, using the nuclear reaction models of the GEANT4 and MCNP6 Monte Carlo codes and the dedicated nuclear reaction codes TALYS and EMPIRE. For each code, we made an effort to optimize the input parameters and model selection. The results of the models were compared to available experimental data of discrete gamma line cross-sections. Overall, the dedicated nuclear reaction codes reproduced the experimental data more consistently, while the Monte Carlo codes showed larger discrepancies for a number of gamma lines. The model differences lead to a variation of the total gamma production near the end of the proton range by a factor of about 2. These results indicate a need for additional theoretical and experimental study of proton-induced gamma emission in human tissue. PMID:22864267

Verburg, Joost M; Shih, Helen A; Seco, Joao

2012-09-01

383

A Search for Gamma-Ray Bursts and Pulsars, and the Application of Kalman Filters to Gamma-Ray Reconstruction  

Microsoft Academic Search

Part I describes the analysis of periodic and transient signals in EGRET data. A method to search for the transient flux from gamma-ray bursts independent of triggers from other gamma-ray instruments is developed. Several known gamma-ray bursts were independently detected, and there is evidence for a previously unknown gamma-ray burst candidate. Statistical methods using maximum likelihood and Bayesian inference are

Brian Jones

2002-01-01

384

Active Neutron and Gamma-Ray Instrumentation for In Situ Planetary Science Applications  

NASA Technical Reports Server (NTRS)

We describe the development of an instrument capable of detailed in situ bulk geochemical analysis of the surface of planets, moons, asteroids, and comets. This instrument technology uses a pulsed neutron generator to excite the solid materials of a planet and measures the resulting neutron and gamma-ray emission with its detector system. These time-resolved neutron and gamma-ray data provide detailed information about the bulk elemental composition, chemical context, and density distribution of the soil within 50 cm of the surface. While active neutron scattering and neutron-induced gamma-ray techniques have been used extensively for terrestrial nuclear well logging applications, our goal is to apply these techniques to surface instruments for use on any solid solar system body. As described, experiments at NASA Goddard Space Flight Center use a prototype neutron-induced gamma-ray instrument and the resulting data presented show the promise of this technique for becoming a versatile, robust, workhorse technology for planetary science, and exploration of any of the solid bodies in the solar system. The detection of neutrons at the surface also provides useful information about the material. This paper focuses on the data provided by the gamma-ray detector.

Parsons, A.; Bodnarik, J.; Evans, L.; Floyd, A.; Lim, L.; McClanahan, T.; Namkung, M.; Nowicki, S.; Schweitzer, J.; Starr, R.; Trombka, J.

2011-01-01

385

Gamma-ray production cross sections from neutron interactions with iron.  

SciTech Connect

The initial purpose of this experiment was to provide a consistent data base of neutron-induced gamma-ray production cross sections over a large energy range for use in estimating elemental composition of the martian surface by observing gamma rays produced by cosmic ray interactions on the planet's surface [Bo02]. However, these data should be useful for other projects such as oil-well logging, accelerator transmutation of nuclear waste, shielding calculations, gamma-ray heating for nuclear reactors and verification of nuclear model calculations and databases. The goal of the measurements was to collect data on the strongest gamma rays from many samples of interest. Because of the available beam time this meant that many of the measurcments were rather short. Despite the short running time the large samples used and the good beam intensity resulted in very satisfactory results. The samples, chosen mainly as common constituents of rock and soil and measured in the same few week period, include: B&, BN, C, Al, Mg, Si, S, Cay Ti, Cr, Mn, and Fe. Be was also used as a neutron scatterer that only produces one gamma ray (478 keV from 7Li) with appreciable intensity. Thus Be can serve as a measure of neutron-induced backgrounds. In this first paper we present results for Fe.

Nelson, R. O. (Ronald O.); Laymon, C. M. (Charles M.); Wender, S. A. (Stephen A.); Drake, D. M. (Darrell M.); Drosg, Manfred; Bobias, S. G. (S. George); McGrath, C. A. (Christopher A.)

2002-01-01

386

Gamma-Ray Bursts: A Mystery Story  

NASA Technical Reports Server (NTRS)

With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or colliding compact objects in distant galaxies. The pieces of the puzzle are beginning to fall into place and yet the story isn't quite finished. I will frame the history of gamma-ray bursts as a mystery story and will end with a description of what we still don't know and what we'll have to do to get the next clues.

Parsons, Ann

2007-01-01

387

The Universe Viewed in Gamma-Rays 1 Galactic Diffuse Gamma-ray Spectrum from Cosmic-ray In-  

E-print Network

The Universe Viewed in Gamma-Rays 1 Galactic Diffuse Gamma-ray Spectrum from Cosmic-ray In- teractions with Gas Clouds Michiko OHISHI and Masaki MORI Institute for Cosmic Ray Research, University, Australia Abstract Gamma-ray spectra from cosmic-ray proton and electron interactions with gas clouds have

Mori, Masaki

388

The Universe Viewed in Gamma-Rays 1 Evidence of TeV Gamma-Ray Radiation in Binary  

E-print Network

The Universe Viewed in Gamma-Rays 1 Evidence of TeV Gamma-Ray Radiation in Binary CYGNUS X-3 V-ALATOO mountain observatory (altitude 3338m), has been collecting Very High Energy gamma-ray data from Galactic structure on micro and macro scales. The gamma-astronomy is a unique experimental possibility of high

Enomoto, Ryoji

389

Tracking and imaging gamma ray experiment (TIGRE) for 1 to 100 MeV gamma ray astronomy  

Microsoft Academic Search

A large international collaboration from the high energy astrophysics community has proposed the Tracking and Imaging Gamma Ray Experiment (TIGRE) for future space observations. TIGRE will image and perform energy spectroscopy measurements on celestial sources of gamma rays in the energy range from 1 to 100 MeV. TIGRE is both a double scatter Compton and gamma-ray pair telescope with direct

A. Alpar; D. Bhattacharya; R. Buccheri; K. Dotson; D. Forrest; W. N. Johnson; G. Kanbach; U. Kiziloglu; R. Kroeger; J. Kurfess; M. McConnell; H. gelman; B. O'Neill; T. O'Neill; A. Owens; B. Pi; B. Pierce; J. Ryan; B. Sacco; G. Simnett; T. Tmer; W. Wheaton; R. S. White; A. Zych

1994-01-01

390

Gamma ray irradiated silicon nanowires: An effective model to investigate defects at the interface of Si/SiOx  

SciTech Connect

The effect of gamma ray irradiation on silicon nanowires was investigated. Here, an additional defect emerged in the gamma-ray-irradiated silicon nanowires and was confirmed with electron spin resonance spectra. {sup 29}Si nuclear magnetic resonance spectroscopy showed that irradiation doses had influence on the Q{sup 4} unit structure. This phenomenon indicated that the unique core/shell structure of silicon nanowires might contribute to induce metastable defects under gamma ray irradiation, which served as a satisfactory model to investigate defects at the interface of Si/SiOx.

Yin, Kui; Zhao, Yi; Liu, Liangbin; Lee, Shuit-Tong; Shao, Mingwang, E-mail: wxlthefirst@gmail.com, E-mail: xuegi@nju.edu.cn, E-mail: mwshao@suda.edu.cn [Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices and Collaborative Innovation, Center of Suzhou Nano Science and Technology, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou 215123 (China); Wang, Xiaoliang, E-mail: wxlthefirst@gmail.com, E-mail: xuegi@nju.edu.cn, E-mail: mwshao@suda.edu.cn; Xue, Gi, E-mail: wxlthefirst@gmail.com, E-mail: xuegi@nju.edu.cn, E-mail: mwshao@suda.edu.cn [State Key Laboratory of Co-ordination Chemistry, Department of Polymer Science and Engineering, Nanjing University, No. 20, Hankou Road, Nanjing 210093 (China)

2014-01-20

391

Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system  

DOEpatents

A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

2013-02-12

392

A White Dwarf Merger Paradigm for Supernovae and Gamma-Ray Bursts  

E-print Network

Gamma-ray bursts can appear to be a hundred times as luminous as supernovae, but their underlying energy source(s) have remained a mystery. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of Type Ib and Ic, a fact which has been exploited by a number of models, to explain the gamma-ray burst phenomenon. Here we interpret the results of basic observations of SN 1987A and of pulsars in globular clusters, to propose the energy source, which powers at least some long-duration gamma-ray bursts, as core-collapse following the merger of two white dwarfs, either as stars or stellar cores. The beaming and intrinsic differences among gamma-ray bursts arise, at least in part, from differing amounts and composition of the gas in the merged stellar common envelopes, with the more energetic bursts resulting from mergers within less massive envelopes. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN 1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core-collapse, or the beams/jets themselves must clear their own path. The core-collapse produces supernovae of Type Ib, Ic, or II (as with SN 1987A, a SNa IIp), leaving a weakly magnetized neutron star remnant with a spin period near 2 milliseconds. There is no compelling reason to invoke any other model to account for gamma-ray bursts. Far from being an unusual event, SN 1987A is typical, having the same merger source of initiation as 95% of all supernovae, the rare exceptions being Ia's induced via gradual accretion from a binary companion, and Fe catastrophe II's.

John Middleditch

2003-12-17

393

THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT  

E-print Network

and prospect of gamma ray astronomy. Emission of gamma rays are due to copious production of electron to gamma rays, linking the gamma ray data to the other bands. A new telescope for VHE gamma ray astronomy of VHE gamma ray astronomy that provides us with the probe for the nonthermal high energy phenomena

Enomoto, Ryoji

394

Intergalactic thermonuclear gamma-ray line  

NASA Technical Reports Server (NTRS)

The possibility of thermonculear reactions occurring in dilute space is briefly considered. X-ray emission from clusters of galaxies demonstrates that perhaps as much as 10 to the 14th solar masses of hot gas (T of about 100 million K) may often surround galaxies in clusters with a density of perhaps 0.004/cu cm. If the ion temperature is 100 million K, the thermonuclear reaction p + d to He-3 + gamma ray should emit gamma rays at a rate of roughly 4 x 10 to the 41st/sec with energy 5.516 + or -0.016 MeV. Such a source in teh virgo cluster at 15.7 Mpc would present a line flux of 1 x 10 to the -11th/sq cm/sec.

Clayton, D. D.

1985-01-01

395

Fissile interrogation using gamma rays from oxygen  

DOEpatents

The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

Smith, Donald; Micklich, Bradley J.; Fessler, Andreas

2004-04-20

396

Ground-Based Gamma-Ray Astronomy  

E-print Network

Ground-based gamma-ray astronomy has become an active astrophysical discipline with four confirmed sources of TeV gamma rays, two plerionic supernova remnants (SNRs) and two BL Lac objects (BL Lacs). An additional nine objects (one plerion, three shell-type SNRs, one X-ray binary, and four BL Lacs) have been detected but have not been confirmed by independent detections. None of the galactic sources require the presence of hadronic cosmic rays, so definitive evidence of their origin remains elusive. Mrk 421 and Mrk 501 are weak EGRET sources but they exhibit extremely variable TeV emission with spectra that extend beyond 10 TeV. They also exhibit correlations with lower energy photons during multi-wavelength campaigns, providing tests of emission models. Next generation telescopes like VERITAS hold the promise of moving this field dramatically forward.

Michael Catanese

1999-11-09

397

Lorentz violation from gamma-ray bursts  

NASA Astrophysics Data System (ADS)

The constancy of light speed is a basic assumption in Einsteins special relativity, and consequently the Lorentz invariance is a fundamental symmetry of space-time in modern physics. However, it is speculated that the speed of light becomes energy-dependent due to the Lorentz invariance violation (LV) in various new physics theories. We analyse the data of the energetic photons from the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find more events to support the energy dependence in the light speed with both linear and quadratic form corrections. We provide two scenarios to understand all the new-released Pass 8 data of bright GRBs by the Fermi-LAT Collaboration, with predictions from such scenarios being testable by future detected GRBs.

Zhang, Shu; Ma, Bo-Qiang

2015-02-01

398

The diffuse galactic gamma ray emission  

NASA Technical Reports Server (NTRS)

The EGRET (Energetic Gamma-Ray Experiment Telescope) detector will provide a much more detailed view of the diffuse galactic gamma ray intensity in terms of higher resolution, greater statistical significance, and broader energy range than earlier missions. These observations will furnish insight into a number of very important questions related to the dynamics and structure of the Galaxy. A diffuse emission model is being developed that incorporates the latest information on matter distribution and source functions. In addition, it is tailored to the EGRET instrument response functions. The analysis code of the model maintains flexibility to accommodate the quality of the data that is anticipated. The discussion here focuses on the issues of the distributions of matter, cosmic rays, and radiation fields, and on the important source functions that enter into the model calculation of diffuse emission.

Bertsch, David L.

1990-01-01

399

The gamma ray north-south effect  

NASA Technical Reports Server (NTRS)

Theoretical calculations are presented that explain the balloon observations by O'Neill et al. (1987) of a strong north-south anisotropy of atmospheric gamma rays over the Southern Hemisphere, and to predict the north-south ratios. It is shown that the gamma rays that originate at the longest distances from the telescopes give the largest north-south ratios. Comparisons are made of the experimental north-south ratios measured on balloons launched from Alice Springs, Australia, and from Palestine, Texas, U.S., and predictions are made for ratios at other geomagnetic latitudes and longitudes. It is pointed out that observers who measure backgrounds for celestial sources may be misled unless they correct for the north-south effect.

White, R. S.; O'Neill, T. J.; Tumer, O. T.; Zych, A. D.

1988-01-01

400

The Compton Gamma Ray Observatory: mission status.  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and continue to be made. The authors describe the capabilities of the four scientific instruments and the observing programs for the first three years of the mission. During Phases 2 and 3 of the mission a Guest Investigator program has been in progress with the Guest Observers' time share increasing from 30% to over 50% for the later mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

401

The GAMCIT gamma ray burst detector  

NASA Technical Reports Server (NTRS)

The GAMCIT payload is a Get-Away-Special payload designed to search for high-energy gamma-ray bursts and any associated optical transients. This paper presents details on the design of the GAMCIT payload, in the areas of battery selection, power processing, electronics design, gamma-ray detection systems, and the optical imaging of the transients. The paper discusses the progress of the construction, testing, and specific design details of the payload. In addition, this paper discusses the unique challenges involved in bringing this payload to completion, as the project has been designed, constructed, and managed entirely by undergraduate students. Our experience will certainly be valuable to other student groups interested in taking on a challenging project such as a Get-Away-Special payload.

Mccall, Benjamin J.; Grunsfeld, John M.; Sobajic, Srdjan D.; Chang, Chinley Leonard; Krum, David M.; Ratner, Albert; Trittschuh, Jennifer E.

1993-01-01

402

Nucleosynthesis and astrophysical gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

The HEAO-3 gamma ray spectrometer has provided evidence in the quest for the understanding of complex element formation in the universe with the discovery of Al-26 in the interstellar medium. It has demonstrated that the synthesis of intermediate mass nuclei is currently going on in the galaxy. This discovery was confirmed by the Solar Maximum Mission. The flux is peaked near the galactic center and indicates about 3 solar masses of Al-26 in the interstellar medium, with an implied ratio of Al-26/Al-27 = .00001. Several possible distributions were studied but the data gathered thus far do not allow discrimination between them. It is felt that only the spaceflight of a high resolution gamma ray spectrometer with adequate sensitivity will ultimately resolve the issue of the source of this material.

Jacobson, Allan S.

1987-01-01

403

Gamma Ray Bursts from Binary Black Holes  

NASA Astrophysics Data System (ADS)

We consider a scenario for the longest duration gamma ray bursts, resulting from the collapse of a massive rotating star in a close binary system with a companion black hole (BH). The primary BH born during the core collapse is first being spun up and increases its mass during the fallback of the stellar envelope just after its birth. As the companion BH enters the outer envelope, it provides an additional angular momentum to the gas. After the infall and spiral-in toward the primary, the two BHs merge inside the circumbinary disk. The second episode of mass accretion and high final spin of the postmerger BH prolongs the gamma ray burst central engine activity. The observed events should have two distinct peaks in the electromagnetic signal, separated by the gravitational wave emission. The gravitational recoil of the burst engine is also possible.

Janiuk, A.; Bejger, M.; Charzynski, S.

2014-07-01

404

SuperAGILE and Gamma Ray Bursts  

SciTech Connect

The solid-state hard X-ray imager of AGILE gamma-ray mission -- SuperAGILE -- has a six arcmin on-axis angular resolution in the 15-45 keV range, a field of view in excess of 1 steradian. The instrument is very light: 5 kg only. It is equipped with an on-board self triggering logic, image deconvolution, and it is able to transmit the coordinates of a GRB to the ground in real-time through the ORBCOMM constellation of satellites. Photon by photon Scientific Data are sent to the Malindi ground station at every contact. In this paper we review the performance of the SuperAGILE experiment (scheduled for a launch in the middle of 2006), after its first onground calibrations, and show the perspectives for Gamma Ray Bursts.

Pacciani, Luigi; Costa, Enrico; Del Monte, Ettore; Donnarumma, Immacolata; Evangelista, Yuri; Feroci, Marco; Frutti, Massimo; Lazzarotto, Francesco; Lapshov, Igor; Rubini, Alda; Soffitta, Paolo; Tavani, Marco [IASF-INAF Rome (Italy); Barbiellini, Guido [INFN Trieste (Italy); Mastropietro, Marcello [CNR Montelibretti (Italy); Morelli, Ennio [IASF-INAF-Bologna (Italy); Rapisarda, Massimo [ENEA Frascati (Italy)

2006-05-19

405

Characteristics of Double Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Double gamma-ray bursts (DGRBs) have two well-separated sub-bursts in the main prompt emission and the typical time interval between them is in the hundreds of seconds. Among DGRBs, gamma-ray bursts (DGRBs) 110801A and 120716A are the ones with known redshifts. However, unlike GRB 110801A, we show that the two sub-bursts of GRB 120716A is severally similar to the short- and long-duration GRBs, thus it is difficult to explain the origin of GRB 120716A by the popular models on the central engine of GRBs. We suggest that some mechanisms of x-ray flares in GRBs, i.e., a post-merger millisecond pulsars or the jet precession in a black hole hyperaccretion system may produce the DGRB.

Liu, Tong; Sun, Mou-Yuan; Hou, Shu-Jin; Li, Ang; Zhang, Fu-Wen; Gu, Wei-Min; Lu, Ju-Fu

2014-11-01

406

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen.

Stone, Edward C.; Mewaldt, Richard A.; Prince, Thomas A.

1992-01-01

407

Nuclear isomer suitable for gamma ray laser  

NASA Technical Reports Server (NTRS)

The operation of gamma ray lasers (gasers) are studied. It is assumed that the nuclear isomers mentioned in previously published papers have inherent limitations. It is further assumed that the judicious use of Bormann effect or the application of the total external reflection of low energy gamma radiation at grazing angle of incidence may permit the use of a gaser crystal sufficiently long to achieve observable stimulated emission. It is suggested that a long lived 0(+) isomer decaying by low energy gamma ray emission to a short lived 2(+) excited nuclear state would be an attractive gaser candidate. It is also suggested that the nuclear isomer be incorporated in a matrix of refractory material having an electrostatic field gradient whose principal axis lies along the length of the medium. This results in the preferential transmission of electric quadrupole radiation along the length of the medium.

Jha, S.

1979-01-01

408

Gamma-Ray Polarimetry with Compton Telescope  

SciTech Connect

Compton telescope is a promising technology to achieve very high sensitivity in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics. Compton kinematics also enables polarization measurement which will open new windows to study gamma-ray production mechanism in the universe. CdTe and Si semiconductor technologies are key technologies to realize the Compton telescope in which their high energy resolution is crucial for high angular resolution and background rejection capability. We have assembled a prototype module using a double-sided silicon strip detector and CdTe pixel detectors. In this paper, we present expected polarization performance of a proposed mission (NeXT/SGD). We also report results from polarization measurements using polarized synchrotron light and validation of EGS4 MC simulation.

Tajima, H

2004-07-06

409

Neutron-driven gamma-ray laser  

DOEpatents

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 .ANG. when subjected to an intense neutron flux of about 400 eV neutrons. A 250 .ANG. thick layer of Be is provided between two layers of 100 .ANG. thick layer of .sup.57 Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux .sup.57 Co becomes .sup.58 Co by neutron absorption. The .sup.58 Co then decays to .sup.57 Fe by 1.6 MeV proton emission. .sup.57 Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the .sup.57 Fe from the .sup.57 Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

Bowman, Charles D. (Los Alamos, NM)

1990-01-01

410

Physical constraints on models of gamma-ray bursters  

SciTech Connect

This report deals with the constraints that can be placed on models of gamma-ray burst sources based on only the well-established observational facts and physical principles. The premise is developed that the very hard x-ray and gamma-ray continua spectra are well-established aspects of gamma-ray bursts. Recent theoretical work on gamma-ray bursts are summarized with emphasis on the geometrical properties of the models. Constraints on the source models which are implied by the x-ray and gamma-ray spectra are described. The allowed ranges for the luminosity and characteristic dimension for gamma-ray burst sources are shown. Some of the deductions and inferences about the nature of the gamma-ray burst sources are summarized. 67 refs., 3 figs.

Epstein, R.I.

1985-01-01

411

Gamma rays from extragalactic radio sources  

NASA Technical Reports Server (NTRS)

It is proposed that the important connection between 3C 273 and 3C 279, the first two extragalactic sources detected at greater than 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a radiation mechanism that focuses gamma rays in the superluminal direction, due to Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet.

Dermer, Charles D.; Schlickeiser, Reinhard; Mastichiadis, Apostolos

1992-01-01

412

Gamma rays from active galactic nuclei  

NASA Technical Reports Server (NTRS)

The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed.

Kazanas, Demosthenes

1990-01-01

413

Gamma-Ray Attenuation-Coefficient Measurements  

Microsoft Academic Search

Total gamma-ray attenuation coefficients have been measured at nine energies in the range of 88 keV to 2.75 MeV for the following elements: Be, C, Mg, Al, S, Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Ag, Sn, La, Gd, Hf, W, Au, Pb, Th, U, and Pu. Radioactive isotopes were used as sources of monoenergetic gamma radiation in a

A. L. Conner; H. F. Atwater; Elizabeth H. Plassmann; J. H. McCrary

1970-01-01

414

Supernovae and Gamma-Ray Bursts  

Microsoft Academic Search

I review the observational status of the Supernova\\/Gamma-Ray Burst (GRB) connection. Available data suggest that Supernovae (SNe) associated with GRBs form an heterogeneous class of objects including bright and faint hypernovae (Hyp) and perhaps also `standard' Ib\\/c events. Current estimates of SN and GRB rates and beaming angles yield ratios GRB\\/SNe-Ibc ?2% and GRB\\/Hyp ?25%. In the few SN\\/GRB associations

Massimo Della Valle

2006-01-01

415

The cannonball model of gamma ray bursts  

E-print Network

The cannonball model (CB) of gamma ray bursts (GRBs) is incredibly more successful than the standard blast-wave models (SM) of GRBs, which suffer from profound inadequacies and limited predictive power. The CB model is falsifiable in its hypothesis and results. Its predictions are summarized in simple analytical expressions, derived, in fair approximations, from first principles. It provides a good description on a universal basis of the properties of long-duration GRBs and of their afterglows (AGs).

Arnon Dar

2003-01-20

416

Short-hard gamma-ray bursts  

Microsoft Academic Search

Two types of gamma-ray bursts (GRBs) are observed: short-duration hard spectrum GRBs and long-duration soft spectrum GRBs. For many years long GRBs were the focus of intense research while the lack of observational data limited the study of short-hard GRBs (SHBs). In 2005 a breakthrough occurred following the first detections of SHB afterglows, longer wavelength emission that follows the burst

Ehud Nakar

2007-01-01

417

Observations of short gamma-ray bursts  

Microsoft Academic Search

We review recent observations of short-hard gamma-ray bursts and their afterglows. The launch and successful ongoing operations of the Swift satellite, along with several localizations from the High-Energy Transient Explorer mission, have provoked a revolution in short-burst studies: first, by quickly providing high-quality positions to observers; and second, via rapid and sustained observations from the Swift satellite itself. We make

Derek B. Fox; Peter W. A. Roming

2007-01-01

418

Modeling Terrestrial Gamma-Ray Flashes  

NASA Astrophysics Data System (ADS)

Upward positive intra-cloud (IC) lightning may drive the large-scale electric fields inside thunderclouds above the relativistic feedback threshold, causing the production of relativistic runaway electron avalanches (RREAs) to become self-sustaining through the generation of backward propagating runaway positrons and back-scattered x-rays. This causes the number of runaway electrons, and the resulting x-ray and gamma-ray emission, to grow exponentially until ionization causes the electric field to discharge, bringing the field below the relativistic feedback threshold again and causing the number of runaway electrons to decline. A new transport code is presented that models runaway electron avalanche growth along with the positron and x-ray feedback processes. Specifically, the model includes the production, propagation, diffusion and avalanche multiplication of runaway electrons, the production and propagation of x-rays and gamma-rays, and the production, propagation and annihilation of runaway positrons. In the model, the large scale electric fields are calculated self-consistently from the charge motion of the drifting low-energy electrons and ions, produced from the ionization of air by the runaway electrons, including 2 and 3-body electron attachment and recombination. Simulation results will be presented that show that when relativistic feedback is taken into account, bright gamma-ray flashes are a natural consequence of upward +IC lightning propagating in large scale thundercloud fields. Furthermore, these flashes have the same time structures, intensities, current-moments, and energy spectra as the terrestrial gamma-ray flashes (TGFs) measured by the RHESSI and Fermi spacecraft.

Dwyer, J. R.

2011-12-01

419

EBT-P gamma ray shielding analysis  

Microsoft Academic Search

First, a one-dimensional scoping study was performed for the gamma ray shield of the ELMO Bumpy Torus proof-of-principle device to define appropriate shielding material and determine the required shielding thickness. The dose equivalent results are analyzed as a function of the radiation shield thickness for different shielding options. A sensitivity analysis for the pessimistic case is given. The recommended shielding

Gohar

1983-01-01

420

Are Gamma-Ray Bursts Standard Candles?  

E-print Network

By dividing a sample of 48 long-duration gamma-ray bursts (GRBs) into four groups with redshift from low to high and fitting each group with the Amati relation log Eiso = a + b log Epeak, I find that parameters a and b vary with the mean redshift of the GRBs in each group systematically and significantly. The results suggest that GRBs evolve strongly with the cosmic redshift and hence are not standard candles.

Li-Xin Li

2007-05-30

421

Terrestrial gamma ray flashes and lightning discharges  

Microsoft Academic Search

Analysis of ELF\\/VLF broadband data from Palmer Station, Antarctica indicates that 76% Terrestrial Gamma-ray Flashes (TGFs) detected on the RHESSI spacecraft occur in association with lightning-generated radio atmospherics arriving from near the footprint of RHESSI and within a few ms of the TGF. The remaining TGFs are not associated with any radio atmospheric, thus by implication CG lightning. The peak

M. B. Cohen; R. K. Said; D. M. Smith; L. I. Lopez

2006-01-01

422

Gamma-Ray Line Observations with RHESSI  

E-print Network

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been observing gamma-ray lines from the Sun and the Galaxy since its launch in February 2002. Here I summarize the status of RHESSI observations of solar lines (nuclear de-excitation, neutron capture, and positron annihilation), the lines of $^{26}$Al and $^{60}$Fe from the inner Galaxy, and the search for positron annihilation in novae.

David M. Smith

2004-04-30

423

Cosmological parametrization of gamma ray burst models  

E-print Network

Using three parametrizations of the gamma ray burst count data comparison is made to cosmological source models. While simple models can fit and faint end slope constraints, the addition of a logarithmic count range variable describing the curvature of the counts shows that models with no evolution or evolution power law in redshift with index less than 10 fail to satisfy simultaneously all three descriptors of the burst data. The cosmological source density that would be required for a fit is illustrated.

Eric V. Linder

1996-07-02

424

Ground-based gamma-ray astronomy  

Microsoft Academic Search

SummaryThis report covers developments in the field of gamma-ray astronomy, essentially in the energy range 300 GeV to 300 TeV, reported\\u000a at the XXIV International Cosmic-Ray Conference in Rome in 1995. Highlights which receive the main attention are the failure\\u000a of several experiments to detect TeV photons from several supernova remnants at the level predicted on current models of shock

A. M. Hillas

1996-01-01

425

The Tools of Gamma Ray Astronomy  

NSDL National Science Digital Library

NASA scientist, Neil Gehrels, serves as your guide to this online lesson on gamma ray tools, which focuses on advances in detector technologies since the 1980s that have enabled us to capture and image high-energy phenomena. Dr. Gehrels explains different methods for detecting and imaging high-energy particles, how they work, and the advantages and disadvantages of each, using examples and imagery from NASA missions.

426

The AGILE gamma-ray astronomy mission  

Microsoft Academic Search

We describe the AGILE gamma-ray astronomy satellite which has recently been selected as the first Small Scientific Mission of the Italian Space Agency. With a launch in 2002, AGILE will provide a unique tool for high-energy astrophysics in the 30 MeV-50 GeV range before GLAST. Despite the much smaller weight and dimensions, the scientific performances of AGILE are comparable to

S. Mereghetti; G. Barbiellini; G. Budini; P. Caraveo; E. Costa; V. Cocco; G. Di Cocco; M. Feroci; C. Labanti; F. Longo; E. Morelli; A. Morselli; A. Pellizzoni; F. Perotti; P. Picozza; M. Prest; P. Soffitta; L. Soli; M. Tavani; E. Vallazza; S. Vercellone

2000-01-01

427

Gamma ray astronomy with IceCube  

Microsoft Academic Search

We demonstrate that the South Pole kilometre-scale neutrino observatory IceCube can detect multi-TeV gamma rays continuously over a large fraction of the southern sky. While not as sensitive as pointing atmospheric Cerenkov telescopes, IceCube can roughly match the sensitivity of Milagro. Also, IceCube is complementary to Milagro because it will observe, without interruption, a relatively poorly studied fraction of the

Francis Halzen; Dan Hooper

2003-01-01

428

Gamma-ray bursts: a Centauro's cry?  

Microsoft Academic Search

A new candidate for the gamma-ray bursts central engine is proposed: if in\\u000asome energetic cosmic event a macroscopic amount of bubbles of the disoriented\\u000achiral condensate can be formed, then their subsequent decays will produce a\\u000arelativistic fireball without the baryon loading problem. The neutron star to\\u000astrange star transition is considered as a candidate example of such cosmic

Z. K. Silagadze

2003-01-01

429

The Swift Gamma-Ray Burst Mission  

Microsoft Academic Search

The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts yr-1 and performing detailed X-ray and UV\\/optical

N. Gehrels; G. Chincarini; P. Giommi; K. O. Mason; J. A. Nousek; A. A. Wells; N. E. White; S. D. Barthelmy; D. N. Burrows; L. R. Cominsky; K. C. Hurley; F. E. Marshall; P. Mszros; P. W. A. Roming; L. Angelini; L. M. Barbier; T. Belloni; S. Campana; P. A. Caraveo; M. M. Chester; O. Citterio; T. L. Cline; M. S. Cropper; J. R. Cummings; A. J. Dean; E. D. Feigelson; E. E. Fenimore; D. A. Frail; A. S. Fruchter; G. P. Garmire; K. Gendreau; G. Ghisellini; J. Greiner; J. E. Hill; S. D. Hunsberger; H. A. Krimm; S. R. Kulkarni; P. Kumar; F. Lebrun; N. M. Lloyd-Ronning; C. B. Markwardt; B. J. Mattson; R. F. Mushotzky; J. P. Norris; J. Osborne; B. Paczynski; D. M. Palmer; H.-S. Park; A. M. Parsons; J. Paul; M. J. Rees; C. S. Reynolds; J. E. Rhoads; T. P. Sasseen; B. E. Schaefer; A. T. Short; A. P. Smale; I. A. Smith; L. Stella; G. Tagliaferri; T. Takahashi; M. Tashiro; L. K. Townsley; J. Tueller; M. J. L. Turner; M. Vietri; W. Voges; M. J. Ward; R. Willingale; F. M. Zerbi; W. W. Zhang

2004-01-01

430

A gamma-ray discriminating neutron scintillator  

SciTech Connect

A neutron scintillator has been developed at Pacific Northwest Laboratory which responds directly to as little as 10 mrem/hour dose equivalent rate fast neutron fields. The scintillator is composed of CaF{sub 2}:Eu or of NaI grains within a silicone rubber or polystyrene matrix, respectively. Neutrons colliding with the plastic matrix provide knockon protons, which in turn deposit energy within the grains of phosphor to produce pulses of light. Neutron interactions are discriminated from gamma-ray events on the basis of pulse height. Unlike NE-213 liquid scintillators, this solid scintillator requires no pulseshape discrimination and therefore requires less hardware. Neutron events are anywhere from two to three times larger than the gamma-ray exposures are compared to 0.7 MeV gamma-ray exposures. The CaF{sub 2}:Eu/silicone rubber scintillator is nearly optically transparent, and can be made into a very sizable detector (4 cm x 1.5 cm) without degrading pulse height. This CaF{sub 2}:Eu scintillator has been observed to have an absolute efficiency of 0.1% when exposed to 5-MeV accelerator-generated neutrons (where the absolute efficiency is the ratio of observed neutron events divided by the number of fast neutrons striking the detector).

Eschbach, P.A.; Miller, S.D.; Cole, M.C. [Pacific Northwest Lab., Richland, WA (United States)] [and others

1994-12-31

431

Afterglow Radiation from Gamma Ray Bursts  

SciTech Connect

Gamma-ray bursts (GRB) are huge fluxes of gamma rays that appear randomly in the sky about once a day. It is now commonly accepted that GRBs are caused by a stellar object shooting off a powerful plasma jet along its rotation axis. After the initial outburst of gamma rays, a lower intensity radiation remains, called the afterglow. Using the data from a hydrodynamical numerical simulation that models the dynamics of the jet, we calculated the expected light curve of the afterglow radiation that would be observed on earth. We calculated the light curve and spectrum and compared them to the light curves and spectra predicted by two analytical models of the expansion of the jet (which are based on the Blandford and McKee solution of a relativistic isotropic expansion; see Sari's model [1] and Granot's model [2]). We found that the light curve did not decay as fast as predicted by Sari; the predictions by Granot were largely corroborated. Some results, however, did not match Granot's predictions, and more research is needed to explain these discrepancies.

Desmond, Hugh; /Leuven U. /SLAC

2006-08-28

432

The Most Remote Gamma-Ray Burst  

NASA Astrophysics Data System (ADS)

ESO Telescopes Observe "Lightning" in the Young Universe Summary Observations with telescopes at the ESO La Silla and Paranal observatories (Chile) have enabled an international team of astronomers [1] to measure the distance of a "gamma-ray burst", an extremely violent, cosmic explosion of still unknown physical origin. It turns out to be the most remote gamma-ray burst ever observed . The exceedingly powerful flash of light from this event was emitted when the Universe was very young, less than about 1,500 million years old, or only 10% of its present age. Travelling with the speed of light (300,000 km/sec) during 11,000 million years or more, the signal finally reached the Earth on January 31, 2000. The brightness of the exploding object was enormous, at least 1,000,000,000,000 times that of our Sun, or thousands of times that of the explosion of a single, heavy star (a "supernova"). The ESO Very Large Telescope (VLT) was also involved in trail-blazing observations of another gamma-ray burst in May 1999, cf. ESO PR 08/99. PR Photo 28a/00 : Sky field near GRB 000131 . PR Photo 28b/00 : The fading optical counterpart of GRB 000131 . PR Photo 28c/00 : VLT spectrum of GRB 000131 . What are Gamma-Ray Bursts? One of the currently most active fields of astrophysics is the study of the mysterious events known as "gamma-ray bursts" . They were first detected in the late 1960's by instruments on orbiting satellites. These short flashes of energetic gamma-rays last from less than a second to several minutes. Despite much effort, it is only within the last few years that it has become possible to locate the sites of some of these events (e.g. with the Beppo-Sax satellite ). Since the beginning of 1997, astronomers have identified about twenty optical sources in the sky that are associated with gamma-ray bursts. They have been found to be situated at extremely large (i.e., "cosmological") distances. This implies that the energy release during a gamma-ray burst within a few seconds is larger than that of the Sun during its entire life time (about 10,000 million years). "Gamma-ray bursts" are in fact by far the most powerful events since the Big Bang that are known in the Universe. While there are indications that gamma-ray bursts originate in star-forming regions within distant galaxies, the nature of such explosions remains a puzzle. Recent observations with large telescopes, e.g. the measurement of the degree of polarization of light from a gamma-ray burst in May 1999 with the VLT ( ESO PR 08/99), are now beginning to cast some light on this long-standing mystery. The afterglow of GRB 000131 ESO PR Photo 28a/00 ESO PR Photo 28a/00 [Preview - JPEG: 400 x 475 pix - 41k] [Normal - JPEG: 800 x 949 pix - 232k] [Full-Res - JPEG: 1200 x 1424 pix - 1.2Mb] ESO PR Photo 28b/00 ESO PR Photo 28b/00 [Preview - JPEG: 400 x 480 pix - 67k] [Normal - JPEG: 800 x 959 pix - 288k] [Full-Res - JPEG: 1200 x 1439 pix - 856k] Caption : PR Photo 28a/00 is a colour composite image of the sky field around the position of the gamma-ray burst GRB 000131 that was detected on January 31, 2000. It is based on images obtained with the ESO Very Large Telescope at Paranal. The object is indicated with an arrow, near a rather bright star (magnitude 9, i.e., over 1 million times brighter than the faintest objects visible on this photo). This and other bright objects in the field are responsible for various unavoidable imaging effects, caused by optical reflections (ring-shaped "ghost images", e.g. to the left of the brightest star) and detector saturation effects (horizontal and vertical straight lines and coloured "coronae" at the bright objects, and areas of "bleeding", e.g. below the bright star). PR Photo 28b/00 shows the rapid fading of the optical counterpart of GRB 000131 (slightly left of the centre), by means of exposures with the VLT on February 4 (upper left), 6 (upper right), 8 (lower left) and March 5 (lower right). It is no longer visible on the last photo. Techni

2000-10-01

433

Fission-fragment gamma-ray multiplicities  

SciTech Connect

The gamma ray multiplicity (M{gamma}) of fission fragments is a valuable experimental clue to the physics of the fission process in particular and the dynamics of heavy-ion collisions in general. Apparatus for measuring M{gamma} as a function of mass asymmetry was constructed and commissioned. The apparatus consisted of a time-of-flight telescope with a time resolution for fission fragments of {approx}1.5 ns and a solid angle of some 0.04 strad. The telescope was constructed using a micro-channel plate start detector and a parallel plate avalanche counter as a stop detector. Gamma rays from the fragments were detected in an array of three 5{double prime} {times} 6{double prime} NaI(Tl) detectors placed approximately 55 cm from the target. When used in beam this apparatus provided sufficient mass resolution for the detected fission fragments and allowed excellent separation of the {gamma}-rays and neutrons from the reaction on the basis of their time-of-flight.

Hook, D.E.

1987-01-01

434

The HEAO 3 gamma-ray spectrometer  

NASA Technical Reports Server (NTRS)

The third High Energy Astronomy Observatory (HEAO 3), successfully launched into low earth orbit on September 20, 1979, carries a large high-resolution gamma-ray spectrometer designed for cosmic nuclear spectroscopy. This gamma-ray spectrometer (the HEAO C-1 experiment) consists of a cluster of four coaxial high-purity germanium detectors, each with a volume of approximately 100 cu cm. Surrounding the germanium detectors is a 6.6-cm thick CsI shield operating in active anticoincidence with the central detectors and defining a field of view of about 30 deg FWHM. An initial energy resolution of 3 keV FWHM at 1.46 MeV was achieved for each detector. All valid events in the germanium detectors are individually analyzed by an 8192-channel pulse area analyzer and transmitted at a maximum rate of 15.6 evens/s for each detector. During a 6-month mission, the experiment will perform a complete sky survey for narrow cosmic gamma-ray line emission to the sensitivity level of about 0.0001 photons/sq cm s over an operating energy range of 0.05-10 MeV.

Mahoney, W. A.; Ling, J. C.; Jacobson, A. S.; Tapphorn, R. M.

1980-01-01

435

Solar gamma rays. [in solar flares  

NASA Technical Reports Server (NTRS)

The theory of gamma ray production in solar flares is treated in detail. Both lines and continuum are produced. Results show that the strongest line predicted at 2.225 MeV with a width of less than 100 eV and detected at 2.24 + or - 2.02 MeV, is due to neutron capture by protons in the photosphere. Its intensity is dependent on the photospheric He-3 abundance. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear deexcitation lines. The strongest prompt lines are at 4.43 MeV from c-12 and at approximately 6.2 from 0-16 and N-15. The gamma ray continuum, produced by electron bremsstrahlung, allows the determination of the spectrum and number of accelerated electrons in the MeV region. From the comparison of the line and continuum intensities a proton-to-electron ratio of about 10 to 100 at the same energy for the 1972, August 4 flare. For the same flare the protons above 2.5 MeV which are responsible for the gamma ray emission produce a few percent of the heat generated by the electrons which make the hard X rays above 20 keV.

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1974-01-01

436

Positron annihilation in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Emission features appear at energies of 350 to 450 keV in the spectra of a number of gamma ray burst sources. These features were interpreted as electron-positron annihilation lines, redshifted by the gravitational field near the surface of a neutron star. Evidence that gamma ray bursts originate at neutron stars with magnetic field strengths of approx. 10(exp 12) Gauss came from recent observations of cyclotron scattering harmonics in the spectra of two bursts. Positrons could be produced in gamma ray burst sources either by photon-photon pair production or by one-photon pair production in a strong magnetic field. The annihilation of positrons is affected by the presence of a strong neutron star magnetic field in several ways. The relaxation of transverse momentum conservation causes an intrinsic broadening of the two-photon annihilation line and there is a decrease in the annihilation cross section below the free-space value. An additional channel for one-photon annihilation also becomes possible in high magnetic fields. The physics of pair production and annihilation near strongly magnetized neutron stars will be reviewed. Results from a self-consistent model for non-thermal synchrotron radiation and pair annihilation are beginning to identify the conditions required to produce observable annihilation features from strongly magnetized plasmas.

Harding, Alice K.

1990-01-01

437

Positron annihilation in gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Emission features appear at energies of 350 to 450 keV in the spectra of a number of gamma ray burst sources. These features were interpreted as electron-positron annihilation lines, redshifted by the gravitational field near the surface of a neutron star. Evidence that gamma ray bursts originate at neutron stars with magnetic field strengths of approx. 1012 Gauss came from recent observations of cyclotron scattering harmonics in the spectra of two bursts. Positrons could be produced in gamma ray burst sources either by photon-photon pair production or by one-photon pair production in a strong magnetic field. The annihilation of positrons is affected by the presence of a strong neutron star magnetic field in several ways. The relaxation of transverse momentum conservation causes an intrinsic broadening of the two-photon annihilation line and there is a decrease in the annihilation cross section below the free-space value. An additional channel for one-photon annihilation also becomes possible in high magnetic fields. The physics of pair production and annihilation near strongly magnetized neutron stars will be reviewed. Results from a self-consistent model for non-thermal synchrotron radiation and pair annihilation are beginning to identify the conditions required to produce observable annihilation features from strongly magnetized plasmas.

Harding, Alice K.

1990-01-01

438

The Properties of Gamma-ray Binaries  

NASA Astrophysics Data System (ADS)

There are a small but growing number of high mass X-ray binaries (HMXBs) that also exhibit emission above 100 MeV. All of these "gamma-ray binaries" exhibit variable emission across the electromagnetic spectrum, from radio to TeV energies, that is modulated with the binary orbital period. The optical stellar companions in these gamma-ray binaries fall into a range of spectral classes: Wolf-Rayet, O main sequence, B supergiant, and Be. Their high energy emission is probably powered by the collision of stellar wind or disk outflows with relativistic pulsar winds in a shock region. These sources present a unique opportunity to study particle acceleration in nearby, Galactic sources. I will review the observed multiwavelength properties of known gamma-ray binaries and discuss the population in the context of the late stages of massive star evolution. I am grateful for support from the Fermi Cycle 4 program through NASA grant NNX11AO41G and from NSF grant AST-1109247.

McSwain, M. Virginia

2013-06-01

439

Gamma Ray Astronomy with Underground Detectors  

E-print Network

Underground detectors measure the directions of up-coming muons of neutrino origin. They can also observe down-going muons made by gamma rays in the Earth's atmosphere. Although gamma ray showers are muon-poor, they produce a sufficient number of muons to detect the sources observed by GeV and TeV telescopes. With a threshold higher by one hundred and a probability of muon production of about $1\\%$ for the shallower AMANDA and Lake Baikal detectors, these instruments can, for a typical GRO source, match the detection efficiency of a GeV satellite detector since their effective area is larger by a factor $10^4$. The muons must have enough energy for accurate reconstruction of their direction. Very energetic muons on the other hand are rare because they are only produced by higher energy gamma rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy in the 100~GeV energy region which nicely matches the threshold energies of the AMANDA and Lake Baikal detectors.

F. Halzen; T. Stanev

1995-07-20

440

VERITAS Observations of Gamma-Ray Blazars  

NASA Astrophysics Data System (ADS)

We report on very high energy (VHE) gamma-ray observations of several active galaxies of the blazar class with VERITAS located at the Fred Laurence Whipple Observatory in Southern Arizona. The VERITAS (Very Energetic Radiation Imaging Telescope Array System) experiment consisting of four Imaging Atmospheric Cherenkov Telescopes (12m diameter each) is the most sensitive instruments in the northern hemisphere for the measurement of VHE gamma-rays in the energy range between 100 GeV to greater than 10 TeV. VERITAS has discovered VHE emission from several blazars and measured their spectral and temporal behavior. Of particular interest are the ``intermediate'' BL Lac objects, a sub-class of blazars not previously detected in VHE gamma rays by ground-based experiments. One of the main scientific goals of VERITAS is understanding VHE phenomena in the vicinity of accreting black holes, and studying particle acceleration in extragalactic astrophysical sources such as blazars. Here we present results on the time variability and spectral properties of the blazars, and discuss implications of the data.

Mukherjee, Reshmi

2009-05-01

441

Gamma-ray burster counterparts - Archival data  

NASA Technical Reports Server (NTRS)

This paper reports on the results of a search for optical transient images associated with gamma-ray bursters based on the collection of archival photographs at the Harvard College Observatory. This study searched through over 32,000 plates showing 16 gamma-ray burst error regions. The primary result is the identification of three optical transient images. The recurrence time scale for optical events with a gamma-ray to optical fluence ratio of less than 1000 is estimated to be 1.3 yr (with a 99-percent confidence interval of between 0.41 and 4.8 yr). A control study was simultaneously made where regions of the sky with no bursters were examined. The control region was 15.6 times larger than the burst search region, yet no optical transients were found. This paper describes in detail the methodology and the statistical results. Close attention is paid to a detailed analysis of the three optical transient images.

Schaefer, Bradley E.

1990-01-01

442

Gamma Ray Burst All-Sky Spectrometer  

NASA Astrophysics Data System (ADS)

The Gamma Ray Burst All-Sky Spectrometer Experiment (GASE) is designed to detect radio emission from gamma ray bursts (GRB's). Radio emission from GRB's could help us better understand the plasma physics of the blast and might also help us measure dark energy. GASE uses short-baseline interferometry with eight dipole antennas located at the MIT Haystack Observatory. These antennas measure the radiofrequency sky at 30 MHz over a 4 MHz bandwidth and are able to collect information from the entire sky. Since the entire sky is surveyed, radio frequency interference occurring at the horizon can be eliminated as a transient source. Along with the SWIFT satellite and the Gamma Ray Burst Coordinate system, we will be able measure blast time, duration and position. We are currently designing techniques to calibrate and image the full sky in radio. In addition to locating and measuring GRB's, GASE may be able to measure dark energy due to the dispersion by the IGM. The pulse of radio emission is delayed as it travels through the intergalactic plasma, with longer wavelengths taking longer to arrive than shorter wavelengths. With the known free electron density (?m) we will use the dispersion measure to calculate the line of sight distance to the GRB and compare to the observed redshift to measure dark energy.

Steger, Arielle

2011-05-01

443

Inflammation-Induced Cell Proliferation Potentiates DNA Damage-Induced Mutations In Vivo  

E-print Network

Mutations are a critical driver of cancer initiation. While extensive studies have focused on exposure-induced mutations, few studies have explored the importance of tissue physiology as a modulator of mutation susceptibility ...

Kiraly, Orsolya

444

Implications of Gamma-Ray Transparency Constraints in Blazars: Minimum Distances and Gamma-Ray Collimation  

NASA Technical Reports Server (NTRS)

We develop a general expression for the gamma - gamma absorption coefficient, alpha(sub gamma(gamma)) for gamma-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R(sub 0), and the inner radius, R(sub ms) which is the radius of marginal stability for a Schwarzschild black hole. We use our result for alpha(sub gamma(gamma)) to calculate the gamma - gamma optical depth, tau(sub gamma(gamma)) for gamma - rays created at height z and propagating at angle Phi relative to the disk axis, and we show that for Phi = 0 and z greater than or approx equal to R(sub 0), tau(sub gamma(gamma)) proportional to Epsilon(sup alpha)z(sup -2(alpha) - 3), where alpha is the X-ray spectral index and Epsilon is the gamma - ray energy. As an application, we use our formalism to compute the minimum distance between the central black hole and the site of production of the gamma-rays detected by EGRET during the 1991 June flare of 3C 279. In order to obtain an upper limit, we assume that all of the X-rays observed contemporaneously by Ginga were emitted by the disk. Our results suggest that the observed gamma - rays may have originated within less than or approx equal to 45 GM/sq c from a black hole of mass greater than or approx equal to 10(exp 9) solar mass, perhaps in active plasma located above the central funnel of the accretion disk. This raises the possibility of establishing a direct connection between the production of the observed gamma - rays and the accretion of material onto the black hole. We also consider the variation of the optical depth as a function of the angle of propagation Phi. Our results indicate that the "focusing" of the gamma - rays along the disk axis due to pair production is strong enough to explain the observed degree of alignment in blazar sources. If the gamma - rays are produced isotropically in gamma - ray blazars, then these objects should appear as bright MeV sources when viewed along off-axis lines of sight.

Becker, Peter A.; Kafatos, Menas

1995-01-01

445

Cosmic gamma-ray background from structure formation in the intergalactic medium  

PubMed

The Universe is filled with a diffuse background of gamma-ray radiation, the origin of which remains one of the unsolved puzzles of cosmology. Less than one-quarter of the gamma-ray flux can be attributed to unresolved discrete sources, such as active galactic nuclei; the remainder appears to constitute a truly diffuse background. Here we show that the shock waves induced by gravity in the gas of the intergalactic medium, during the formation of large-scale structures like filaments and sheets of galaxies, produce a population of highly relativistic electrons. These electrons scatter a small fraction of the cosmic microwave background photons in the local Universe up to gamma-ray energies, thereby providing the gamma-ray background. The predicted diffuse flux agrees with the observed background across more than four orders of magnitude in photon energy, and the model predicts that the gamma-ray background, though generated locally, is isotropic to better than five per cent on angular scales larger than a degree. Moreover, the agreement between the predicted and observed background fluxes implies a mean cosmological density of baryons that is consistent with Big Bang nucleosynthesis. PMID:10821264

Loeb; Waxman

2000-05-11

446

The axion-photon interaction and gamma ray signals of dark matter  

NASA Astrophysics Data System (ADS)

We explore two scenarios where the axion-photon interaction could induce additional astrophysical gamma ray signals for the dark matter. In the first scenario, dark compact objects made of axions, named axion stars, could collide with neutron stars. The whole energy of the axion star can be dissipated in the magnetized conducting medium of the neutron star generating gamma rays. The second scenario is an indirect method for observing self-annihilating dark matter trapped in stars: Gamma rays produced by the self-annihilation of neutralinos in the interior of the Sun can be transformed into axions due to photon-axion conversion. Then, the axion will travel freely in the Sun and be converted into photons again. This process is often referred as 'shine light through walls', in this case, the wall will be the solar interior. Hence, GeV gamma rays might pass through the Sun. We may conclude that observation of GeV photons by gamma-ray observatories like HAWC, coming from the Sun, may be a signal of annihilation of neutralinos in the interior of the Sun.

Barranco, J.; Carrillo Monteverde, A.; Delepine, D.

2014-03-01

447

The Gamma-ray Large Area Space Telescope and Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high energy gamma-ray sky. The main instrument on GLAST, the Large Area Telescope (LAT) is a pair-conversion telescope that will survey the sky from 20 MeV to greater than 300 GeV. With the GLAST launch in 2007, the LAT will open a new and important window on a wide variety of high energy phenomena, including supermassive black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and cosmic ray acceleration and dark matter. A second instrument, the GLAST Burst Monitor (GBM), greatly enhances GLAST s capability to study GRB by providing important spectral and timing information in the 10 keV to 30 MeV range. We describe how the instruments, spacecraft and ground system work together to provide observations of gamma-ray bursts from 8 keV - 300 GeV and to provide rapid notification of bursts to the wider gamma-ray burst community.

McEnery, Julie; Ritz, Steve

2006-01-01

448

The solar gamma ray and neutron capabilities of COMPTEL on the Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The imaging Compton telescope COMPTEL on the Gamma Ray Observatory (GRO) has unusual spectroscopic capabilities for measuring solar gamma-ray and neutron emission. The launch of the GRO is scheduled for June 1990 near the peak of the sunspot cycle. With a 30 to 40 percent probability for the Sun being in the COMPTEL field-of-view during the sunlit part of an orbit, a large number of flares will be observed above the 800 keV gamma-ray threshold of the telescope. The telescope energy range extends to 30 MeV with high time resolution burst spectra available from 0.1 to 10 MeV. Strong Compton tail suppression of instrumental gamma-ray interactions will facilitate improved spectral analysis of solar flare emissions. In addition, the high signal to noise ratio for neutron detection and measurement will provide new neutron spectroscopic capabilities. Specifically, a flare similar to that of 3 June 1982 will provide spectroscopic data on greater than 1500 individual neutrons, enough to construct an unambiguous spectrum in the energy range of 20 to 200 MeV. Details of the instrument and its response to solar gamma-rays and neutrons will be presented.

Ryan, James M.; Lockwood, John A.

1989-01-01

449

A link between prompt optical and prompt gamma-ray emission in gamma-ray bursts.  

PubMed

The prompt optical emission that arrives with the gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium. PMID:15889084

Vestrand, W T; Wozniak, P R; Wren, J A; Fenimore, E E; Sakamoto, T; White, R R; Casperson, D; Davis, H; Evans, S; Galassi, M; McGowan, K E; Schier, J A; Asa, J W; Barthelmy, S D; Cummings, J R; Gehrels, N; Hullinger, D; Krimm, H A; Markwardt, C B; McLean, K; Palmer, D; Parsons, A; Tueller, J

2005-05-12

450

Neutron and gamma-ray dose-rates from the Little Boy replica  

SciTech Connect

We report dose-rate information obtained at many locations in the near vicinity of, and at distances out to 0.64 km from, the Little Boy replica while it was operated as a critical assembly. The measurements were made with modified conventional dosimetry instruments that used an Anderson-Braun detector for neutrons and a Geiger-Mueller tube for gamma rays with suitable electronic modules to count particle-induced pulses. Thermoluminescent dosimetry methods provide corroborative data. Our analysis gives estimates of both neutron and gamma-ray relaxation lengths in air for comparison with earlier calculations. We also show the neutron-to-gamma-ray dose ratio as a function of distance from the replica. Current experiments and further data analysis will refine these results. 7 references, 8 figures.

Plassmann, E.A.; Pederson, R.A.

1984-01-01

451

The emission of Gamma Ray Bursts as a test-bed for modified gravity  

E-print Network

The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining the huge energy emission of Gamma Ray Bursts. Specifically, we investigate the emission of radiation by charged particles non-minimally coupled to the gravitational background where higher order curvature invariants are present. The coupling gives rise to an additional force inducing a non-geodesics motion of particles. This fact allows a strong emission of radiation by gravitationally accelerated particles. As we will show with some specific model, the energy emission is of the same order of magnitude of that characterizing the Gamma Ray Burst physics. Alternatively, strong curvature regimes can be considered as a natural mechanism for the generation of highly energetic astrophysical events.

Capozziello, Salvatore

2015-01-01

452

Cosmic-ray and gamma-ray constraints on dark matter stability  

NASA Astrophysics Data System (ADS)

We examine different constraints on dark matter stability from cosmic-ray and gamma-ray observations and their complementarity through higher-order effects. Two-body and three-body decays of dark matter particles into charged leptons and quarks generically induce decays into monochromatic photons at the quantum level, giving rise to distinct signatures. We also present a general model-independent analysis of hadronic constraints in the mass-lifetime parameter space and compare those constraints to current and projected limits on gamma-ray lines. Furthermore, we discuss how the production of monochromatic photons can be enhanced by kinematic effects, potentially giving rise to observable lines in the gamma-ray sky.

Tran, David

2014-03-01

453

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background  

NASA Technical Reports Server (NTRS)

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Venters, T. M.; Pavlidou, V.

2013-01-01

454

Gamma-ray astronomy with a large muon detector in the ARGO-YBJ experiment  

SciTech Connect

The ARGO-YBJ experiment, currently under construction at the YangBaJing Laboratory (Tibet, P.R. China, 4300 m a.s.l.), could be upgraded with a large ({approx} 2500 m2) muon detector both to extend the sensitivity to {gamma}-ray sources to energies greater than {approx} 20 TeV and to perform a cosmic ray primary composition study. In this paper we present an evaluation of the rejection power for proton-induced showers achievable with the upgraded ARGO-YBJ detector. Minimum detectable {gamma}-ray fluxes are calculated for different experimental setups.

Di Sciascio, G.; Di Girolamo, T.; Megna, R.; Saggese, L. [INFN, sez. di Napoli (Italy); Dipartimento di Scienze Fisiche dell Universita di Napoli (Italy); Fratini, K. [INFN, sez. di Roma 3 (Italy); Dipartimento di Fisica dell Universita di Roma 3 (Italy)

2005-02-21

455

SHORT GAMMA-RAY BURSTS AND DARK MATTER SEEDING IN NEUTRON STARS  

SciTech Connect

We present a mechanism based on internal self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars that may trigger full or partial conversion into a quark star. We explain how this effect may induce a gamma-ray burst (GRB) that could be classified as short, according to the usual definition based on time duration of the prompt gamma-ray emission. This mechanism differs in many aspects from the most discussed scenario associating short GRBs with compact object binary mergers. We list possible observational signatures that should help distinguish between these two possible classes of progenitors.

Perez-Garcia, M. Angeles [Department of Fundamental Physics and IUFFyM, University of Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain); Daigne, F.; Silk, J., E-mail: mperezga@usal.es, E-mail: daigne@iap.fr, E-mail: j.silk1@physics.ox.ac.uk [UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014 Paris (France)

2013-05-10

456

CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy.  

SciTech Connect

We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and neutron spectroscopy. The spectrometer can be flown either on the instrument deck of the spacecraft or on a boom. For deck-mounted systems, a BGO anticoincidence shield is included in the design to suppress the response of the CdZnTe detector to gamma rays that originate in the spacecraft. The BGO shield also serves as a backup spectrometer, providing heritage from earlier planetary science missions and reducing the risk associated with the implementation of new technology.

Prettyman, T. H. (Thomas H.); Feldman, W. C. (William C.); Fuller, K. R. (Kenneth R.); Storms, S. A. (Steven A.); Soldner, S. A.; Lawrence, David J. (David Jeffery),; Browne, M. C. (Michael C.); Moss, C. E. (Calvin E.)

2001-01-01

457

Development of neutron shields for gamma-ray telescopes in space and observation of galactic center sources by a balloon-borne gamma-ray telescope, GRATIS  

Microsoft Academic Search

First, this thesis introduces the supershield---a new shield concept to address the neutron-induced background problem for future gamma-ray telescopes in space. Neutron-induced background has become increasingly important, as detector\\/active-shield technology improves. We model the basic designs of supershields by Monte Carlo simulations and verify the performance of supershields through laboratory experiments. We also discuss their future applications. Second, this thesis

Jaesub Hong

2002-01-01

458

{gamma}-ray spectroscopy of {sup 163}Ta  

SciTech Connect

Excited states in {sup 163}Ta have been identified for the first time using the {sup 106}Cd({sup 60}Ni,3p) fusion evaporation reaction. {gamma} rays were detected using the JUROGAM {gamma}-ray spectrometer and recoil discrimination was achieved using the recoil ion transport unit (RITU) gas-filled separator in conjunction with the GREAT spectrometer situated at the focal plane of the RITU. The yrast states are assigned to a strongly coupled rotational band based on a {pi}h{sub 11/2} configuration. This structure exhibits large signature splitting at low spins that disappears after the paired band crossing because of the alignment of a pair of i{sub 13/2} neutrons. This effect is ascribed to triaxial shape changes induced by the core-polarizing properties of the deformation-aligned h{sub 11/2} proton and the rotation-aligned i{sub 13/2} neutrons. Two additional strongly coupled band structures have been established and are discussed in terms of octupole-vibrational and two-quasiparticle excitations built on the yrast structure. The experimental results are compared with predictions from cranked-shell-model and total-Routhian-surface calculations.

Sandzelius, M. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Department of Physics, University of Jyvaeskylae, FIN-40014 Jyvaeskylae (Finland); Cederwall, B.; Andgren, K.; Baeck, T.; Hadinia, B.; Johnson, A.; Khaplanov, A.; Wyss, R. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Ganioglu, E. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Science Faculty, Physics Department, Istanbul University, 34459 Istanbul (Turkey); Thomson, J.; Bianco, L.; Joss, D. T.; Page, R. D. [Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S. [Department of Physics, University of Jyvaeskylae, FIN-40014 Jyvaeskylae (Finland)] (and others)

2009-11-15

459

A Test for Epistasis Among Induced Mutations in Caenorhabditis elegans  

Microsoft Academic Search

Synergistic epistasis, in which deleterious mutations tend to magnify each other's effects, is a necessary component of the mutational deterministic hypothesis for the maintenance of sexual production. We tested for epistasis for life-history traits in the soil nematode Caenorhabditis elegans by inducing mutations in two genetic backgrounds: a wild-type strain and a set of genetically loaded lines that contain large

Andrew D. Peters; Peter D. Keightley

2000-01-01

460

Tobacco Induced Mutations: A Fun, Visually Impressive Experiment  

ERIC Educational Resources Information Center

A modified version "Tobacco Induced Mutations" of Ames assay experiment provides a meaningful context for students to learn about the concept of mutations by using a known carcinogen that is tobacco. This experiment shows toxicological concept of the dose/response relationship and visually demonstrates when a mutation have occurred in bacteria

Milholland, Rebecca B. R.; Hines, Stefani D.

2004-01-01

461

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect

Star formation in galaxies is observed to be associated with gamma-ray emission, presumably from non-thermal processes connected to the acceleration of cosmic-ray nuclei and electrons. The detection of gamma rays from starburst galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity. Since star formation is known to scale with total infrared (8-1000 {mu}m) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star-forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study, we apply the functional relationships between gamma-ray luminosity and radio and IR luminosities of galaxies derived by the Fermi Collaboration to a sample of the best candidate galaxy clusters for detection in gamma rays in order to place low