Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “gamma rays”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

X-ray and optical observations of the November 19, 1978 gamma-ray burst source region

The Nov. 19, 1978 gamma-ray burst (GRB) has a very well determined error box, 10 square arcmin (Cline et al., 1981). An 8000-sec IPC exposure with the Einstein Observatory detected, at a 3.4-sigma level, one low intensity (less than 3 x 10 to the -13th erg/sq cm per sec) X-ray source inside the error box. The probability of a serendipitous detection was 0.01. Inside the X-ray source error box there are two weak radio sources, one of them highly polarized (Hjellming and Ewald, 1981), and two 20-magnitude objects, not coincident with the radio sources visible in the ESO/SRC J and R plates. With the exception of N49, this is the first possible detection of X-ray emission inside a GRB box. Its low intensity justifies, in fact, the lack of detection for other events.

Pizzichini, G.↗
NASA NTRS1988

Gamma-ray and hard X-ray imaging of solar flares

The scientific and technical aspects of high-resolution gamma-ray and X-ray imaging of solar flares are discussed. The scientific necessity for imaging observations of solar flares and the implications of future observations for the study of solar flare electrons and ions are considered. Performance parameters for a future hard X-ray and gamma-ray imager are summarized. Techniques for high-energy photon imaging including direct collimation imaging, coded apertures, and modulation collimators are surveyed. The technique of Fourier-transform imaging is examined. The options for detectors and grid fabrication are reviewed. Several planned future high-energy imagers are described.

Prince, T. A.↗
NASA NTRS1995

The LXeCAT instrument for gamma-ray astrophysics

The Liquid Xenon Coded Aperture Telescope (LXeCAT) and its capability to image astrophysical gamma-ray sources in the MeV region is described. The gamma-ray detector is a Liquid Xenon Time Projection Chamber (LXeTPC) triggered by the primary scintillation light. Effective background rejection is a direct consequence of the intrinsic three-dimensional imaging capability of the LXeTPC. Initial results with a 10 liter prototype confirm an energy resolution of 6% FWHM, a position resolution of 1 mm RMS and a light triggering efficiency higher than 90% for 1 MeV gamma-rays.

Aprile, E.↗
NASA NTRS1996

BATSE Observations of Gamma-Ray Burst Spectra: Low-Energy Behavior of Time-Averaged Spectra - Part 3

We analyze time-averaged spectra from 86 bright gamma-ray bursts from the first 5 years of the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory to determine whether the lowest energy data are consistent with a standard spectra form fit to the data at all energies. The BATSE Spectroscopy Detectors have the capability to observe photons as low as 5 keV. Using the gamma-ray burst locations obtained with the BATSE Large Area Detectors, the Spectroscopy Detectors' low-energy response can be modeled accurately. This, together with a postlaunch calibration of the lowest energy Spectroscopy Detector discriminator channel, which can lie in the range 5-20 keV, allows spectral deconvolution over a broad energy range, approx. 5 keV to 2 MeV. The additional coverage allows us to search for evidence of excess emission, or for a deficit, below 20 keV. While no burst has a significant (greater than or equal to 3 sigma) deficit relative to a standard spectra model, we find that 12 bursts have excess low-energy emission, ranging between 1.2 and 5.8 times the model flux, that exceeds 5 sigma in significance. This is evidence for an additional low-energy spectral component in at least some bursts, or for deviations from the power-law spectral form typically used to model gamma-ray bursts at energies below 100 keV.

Preece, R. D.↗
NASA NTRS1978

Observational evidence for extraterrestrial gamma-ray line sources

During the 1974 balloon flight of a high spectral resolution gamma-ray telescope, observing in the energy range of about 50 keV to 10 Mev, evidences were gathered for two cosmic sources of gamma-ray lines. These are a 73 keV line feature superimposed on a power law continuum spectrum in the 55 to 300 keV range from the Crab nebula; and a flare-like event lasting about twenty minutes, during which four intense gamma-ray lines were measured at .41, 1.79, 2.22 and 5.95 MeV. The properties and operation of the detector used are described. The measured spectrum and count rate are discussed.

Jacobson, A. S.↗
NASA NTRS2003

The Burst and Transient Source Experiment(BATSE)Earth Occultation Catalog of Low-Energy Gamma-Ray Sources. Short title: BATSE Earth Occultation Catalog v2.0

The Burst and Transient Source Experiment (BATSE), aboard the Compton Gamma Ray Observatory (CGRO), provided a record of the low-energy gamma-ray sky (approx. 20-1000 keV) between 1991 April and 2000 May (9.1y). BATSE monitored the high energy sky using the Earth occultation technique (EOT) for point sources whose emission extended for times on the order of the CGRO orbital period (approx. 92m) or greater. Using the EOT to extract flux - 2 - information, a catalog of sources using data from the BATSE large area detectors has been prepared. The first part of the catalog consists of results from the all-sky monitoring of 58 sources, mostly Galactic, with intrinsic variability on timescales of hours to years. For these sources, we have included tables of flux and spectral data, and outburst times for transients. Light curves (or flux histories) covering the entire nine mission are being placed on the world wide web. We then performed a deep-sampling of these 58 objects, plus a selection of 121 more objects, combining data from the entire 9.ly BATSE dataset. Source types considered were primarily accreting binaries, but a small number of representative active galaxies, X-ray-emitting stars, and supernova remnants were also included. The sample represents a compilation of sources monitored and/or discovered with BATSE and other high energy instruments between 1991 and 2000, known sources taken from the HEAO 1 A-4 (Levine et al. 1984) and Macomb and Gehrels (1999) catalogs. The deep sample results include definite detections of 82 objects and possible detections of 36 additional objects. The definite detections spanned three classes of sources: accreting black hole and neutron star binaries, active galaxies and supernova remnants. The average fluxes measured for the fourth class, the X-ray emitting stars, were below the confidence limit for definite detection. Flux data for the deep sample are presented in four energy bands: 20-40, 40-70, 70-160, and 160-430 keV. The limiting average flux level (9.1 y) for the sample varies from 3.5 to 20 mCrab (5delta) between 20 and 430 keV, depending on systematic error, which in turn is primarily dependent on the sky location. To strengthen the credibility of detection of weaker sources (approx.5-25 mCrab), we generated Earth occultation images, searched for periodic behavior using FFT and epoch folding methods, and critically evaluated the energy-dependent emission in the four flux bands. The deep sample results are intended for guidance in performing future all-sky surveys or pointed observations in the hard X-ray and low-energy gamma-ray band, as well as more detailed studies with the BATSE EOT.

Harmon, B. A.↗
NASA NTRS1977

Galactic gamma rays and the cosmic-ray halo problem

Detailed models of diffused halos of various sizes are considered. In such models, the scale perpendicular to the plane has a strong effect in determining the distribution of cosmic rays. Radial distributions were calculated for cylindrical coordinate models. The implied gamma-ray longitude distributions were then calculated and compared with the SAS-2 data. Assuming the sources to be supernova remnants or pulsars, only cosmic-ray nucleon halo models with an upper limit scale height of about 3 kpc provide a good fit to the gamma ray data. Consideration of the gamma-ray latitude data gives a half thickness of 2 + or - 2 kpc for the cosmic ray electron halo.

Stecker, F. W.↗
NASA NTRS1978

The gamma ray observatory

A large, free-flying space observatory is planned for (1) locating and characterizing gamma ray sources, in particular peculiar objects such as pulsars; (2) studying diffuse gamma ray emission, both from our galaxy and from extragalactic space, (3) investigating other galaxies, especially radio galaxies, Seyfert galaxies and QSOs; and (4) understanding the origin of gamma ray bursts. The spacecraft will weight about 10,000 kg, with about 6,500 kg available for scientific instruments, providing about 400 watts of power to the instruments, and about 12,000 bits per second of telemetry. The spacecraft which will be launched by the space shuttle into a 400 to 500 km circular orbit, inclined at 28.5 deg to the equator, will be three-axis stabilized, with orientation capability of about 20 arc minutes and aspect determination of 2 arc minutes. Absolute timing of 0.1 millisecond will be provided by the spacecraft. The instruments will be co-aligned along one axis of the spacecraft to optimize the spectral coverage of a particular region. A two-year mission is planned with launch in 1984. Possible retrieval by the shuttle at the end of the mission is considered.

Opp, A. G.↗
NASA NTRS1993

Gamma ray constraints on the Galactic supernova rate

Most Galactic optical supernovae are hidden due to severe extinction in the disk, but could be detectable through their gamma-ray afterglow. Ti-44 is among the potentially detectable isotopes in supernova ejecta. HEAO 3 and SMM sky surveys have not detected gamma-ray lines from the decay of Ti-44, thus constraining SN rates and nucleosynthesis. We perform Monte Carlo simulations of the gamma-ray signatures of SN occurring during the last millenium to interpret the gamma-ray paucity.

Hartmann, D.↗
NASA NTRS1999

Multiwavelength Studies of the Peculiar Gamma-ray Source 3EG J1835+5918

The source 3EG J1835+5918 was discovered early in the CGRO (Compton Gamma Ray Observatory) mission by EGRET as a bright unidentified gamma-ray source outside the galactic plane. Especially remarkable, it has not been possible to identify this object with any known counterpart in any other wavelengths band since then. Analyzing our recent ROSAT HRI observation, for the first time we are able to suggest X-ray counterparts of 3EG J1835+5918. The discovered X-ray sources were subject of deep optical investigations in order to reveal their nature and conclude on the possibility of being counterparts for this peculiar gamma-ray source.

Reimer, O.↗
NASA NTRS1975

Recent observations of cosmic gamma-ray bursts

The paper summarizes current knowledge of cosmic gamma ray bursts obtained from recent spaceborne observations. Three facts lie at the basis of interpreting gamma ray burst observations: (1) all measured event differential energy spectra appear to be alike, (2) there is no evidence that the event integral size spectrum departs from a -1.5 power law, and (3) the temporal structures of most events are consistent with a continuous flutter down to at least 30 msec throughout the event histories. Event-average spectra of 9 bursts observed with IMP-7 are presented, and the Vela size spectrum is compared with IMP-7 points, SAS-2 events, and balloon experiment limits.

Cline, T. L.↗
NASA NTRS1993

Effects of location uncertainties on the observed distribution of gamma-ray bursts detected by BATSE

The Burst and Transient Source Experiment (BATSE) on NASA's Compton Gamma-Ray Observatory has shown that the sources of gamma-ray bursts have an angular distribution consistent with isotropy, yet the bursts are spatially inhomogeneous. Detection of a statistically significant deviation from isotropy in the burst distribution would provide a clue to the distance of the burst sources. BATSE's ability to detect slight deviations of the angular distribution from isotropy is, in part, dependent on the accuracy of the computed burst locations. Using bursts whose locations have been determined accurately and independently, we estimate BATSE's location uncertainties and incorporate them into 3D Monte Carlo simulations of the burst distributions to show that, despite individual burst location uncertainties of about 5 deg, the ability of BATSE to place stringent limits on the anisotropy present in the angular distribution of the gamma-ray bursts is not significantly degraded. Observational effects of possible galactic halo distributions of the burst sources are noted.

Horack, J. M.↗
DOE OSTI2024

Supernova Axions Convert to Gamma Rays in Magnetic Fields of Progenitor Stars

It has long been established that axions could have been produced within the nascent proto-neutron star formed following the type II supernova SN1987A, escaped the star due to their weak interactions, and then converted to gamma rays in the Galactic magnetic fields; the nonobservation of a gamma-ray flash coincident with the neutrino burst leads to strong constraints on the axion-photon coupling for axion masses m a ≲10 –10 eV. In this Letter, we use SN1987A to constrain higher mass axions, all the way to m a ~10 –3 eV, by accounting for axion production from the Primakoff process, nucleon bremsstrahlung, and pion conversion along with axion-photon conversion on the still-intact magnetic fields of the progenitor star. Moreover, we show that gamma-ray observations of the next Galactic supernova, leveraging the magnetic fields of the progenitor star, could detect quantum chromodynamics axions for masses above roughly 50 μ⁢eV, depending on the supernova. We propose a new full-sky gamma-ray satellite constellation that we call the GALactic AXion Instrument for Supernova (GALAXIS) to search for such future signals along with related signals from extragalactic neutron star mergers.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1988

High energy gamma-ray observations of SN 1987A

Results are presented from observations of SN 1987A made with a combined high energy gamma ray and hard X-ray payload carried on a balloon flight over Alice Springs, Australia on April 5, 1988. The payload instrumentation is described, emphasizing the characteristics of the gamma-ray detector. The gamma-ray emission profile is illustrated and the preliminary results of the observations are summarized.

Sood, R. K.↗
NASA NTRS1976

Local and large scale galactic gamma-ray emission

A study of the gas-to-dust ratio suggests that interstellar reddening may provide an accurate way of assessing column densities in various directions in the Galaxy. A gamma ray intensity of 7.25 x 10 to the -5th E sub B-V photon/sq cm/s/sterad is predicted for regions of the Galaxy where the medium cosmic ray density is equal to that observed close to the sun. It is found that in the longitude range of about 0-180 degrees, the large scale cosmic ray distribution producing the gamma rays follows that of extreme population I stars put in evidence by giant H II regions, and that of molecular hydrogen traced by carbon monoxide emission. The gamma-ray production exhibits a maximum at R roughly equal to 5 kpc, and practically vanishes at R not less than 11 kpc, beyond the location of the outermost H II regions.

Puget, J. L.↗
NASA NTRS2006

Gamma-ray Observations with Swift and their Impact on the TeV Community

The Swift gamma-ray burst explorer was launched on Nov. 20, 2004 from Cape Canaveral, Florida. The first instrument onboard became fully operational less than a month later. Since that time the Burst Alert Telescope (BAT) on Swift has detected more than 150 gamma-ray bursts (GRBs), most of which have also been observed within two minutes by the Swift narrow-field instruments: the X-Ray Telescope (XRT) and the Ultra-Violet and Optical Telescope (UVOT). Swift trigger notices are distributed worldwide within seconds of the trigger through the Gamma-ray burst Coordinates Network (GCN) and a substantial fraction of GRBs have been followed up by ground and space-based telescopes, ranging in wavelength from radio to TeV. Results have included the first rapid localization of a short GRB and further validation of the theory that short and long bursts have different origins; detailed observations of the power-law decay of burst afterglows leading to an improved understanding of the fireball and afterglow models; and detection of the most distant GRB ever found. Swift is also a sensitive X-ray observatory with capabilities to monitor galactic and extragalactic transients on a daily basis, carry out the first all-sky hard X-ray survey since HEAO-1, and study in detail the spectra of X-ray transients. The talk will emphasize the connection between Swift/BAT GRB observations and source monitoring and TeV observations.

Krimm, Hans↗
DOE OSTI2022

The Quest for New Correlations in the Realm of the Gamma-Ray Burst—Supernova Connection

Gamma-ray bursts (GRBs) are very energetic cosmological transients. Long GRBs are usually associated with Type Ib/c supernovae (SNe), and we refer to them as GRB-SNe. Since the associated SN for a given GRB is observed only at low redshift, a possible selection effect exists when we consider intrinsically faint sources that cannot be observed at high redshift. Thus, it is important to explore the possible relationships between GRB and SN parameters after these have been corrected for astrophysical biases due to the instrumental selection effects and redshift evolution of the variables involved. So far, only GRB prompt emission properties have been checked against the SN Ib/c properties without considering the afterglow (AG). This work investigates the existence of relationships among GRBs’ prompt and AG and associated SN properties. We investigate 91 bidimensional correlations among the SN and GRB observables before and after their correction for selection biases and evolutionary effects. As a result of this investigation, we find hints of a new correlation with a Pearson correlation coefficient >0.50 and a probability of being drawn by chance <0.05. This correlation is between the luminosity at the end of the GRB optical plateau emission and the rest-frame peak time of the SN. According to this relation, the brightest optical plateaus are accompanied by the largest peak times. This correlation is corrected for selection biases and redshift evolution and may provide new constraints for the astrophysical models associated with the GRB-SN connection.

79 ASTRONOMY AND ASTROPHYSICS↗