Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “gamma-ray detection”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

A study of the temporal and spectral characteristics of gamma ray bursts

Gamma-ray burst data obtained from the ISEE-3 Gamma Ray Burst Spectrometer and the Solar Maximum Mission's Hard X-ray Burst Spectrometer (HXRBS) were analyzed to yield information on burst temporal and spectral characteristics. A Monte Carlo approach was used to simulate the HXRBS response to candidate spectral models. At energies above about 100 keV, the spectra are well fit by exponential forms. At lower energies, 30 keV to 60 keV, depressions below the model continua are apparent in some bursts. The depressions are not instrumental or data-reduction artifacts. The event selection criterion of the ISEE-3 experiment is based on the time to accumulate a present number of photons rather than the photon count per unit time and is consequently independent of event duration for a given burst intensity, unlike most conventional systems. As a result, a significantly greater percentage of fast, narrow events have been detected. The ratio of count rates from two ISEE-3 detectors indicates that bursts with durations or approx. one second have much softer spectra than longer bursts.

Norris, J.↗
NASA NTRS1982

Persistent X-ray emission from a gamma-ray burst source

A quiescent X-ray source detected with the Einstein X-ray Observatory in a location consistent with that of an intense gamma ray burst is shown to be also consistent with the location of the 1928 optical transient, the likely optical counterpart of the gamma ray burst source GBS0117-29. The system appears to be underluminous in X-rays by a factor of 10; possible reasons for this are discussed. The observed X-ray flux would require an accretion rate of about 10 to the -14th (d/1 kpc/)-squared solar masses per year, which is probably too low to be consistent with published nuclear flash models for gamma bursts, unless the distance is substantially greater than about 1 kpc or the burst recurrence time is greater than about 50 yrs, or the accretion rate is highly variable. Such a long recurrence time appears to be inconsistent with the detection of the optical burst.

Grindlay, J. E.↗
NASA NTRS1983

Advances in gamma-ray line astronomy

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.↗
NASA NTRS1983

Constraints on gamma-ray bursters from soft X-ray transients

The Columbia Astrophysics Laboratory's Einstein imaging proportional counter database has been searched for possible X-ray counterparts to gamma ray bursts. The limiting sensitivity was about 10 to the 10th erg/sq cm with a total exposure of about 3 x 10 to the 6th s divided among about 1000 1 deg x 1 deg fields. Four events with a pointlike spatial distribution were detected but their extremely soft spectra makes them unlikely candidates for gamma ray burst counterparts. The results are used to place limits on the X-ray and gamma ray luminosity ratio and log(number)N-log(flux)S relation for gamma ray bursts. The constraints placed on models for their origin are commented on.

Helfand, D. J.↗
NASA NTRS1983

HEAO 1 high-energy X-ray observations of Centaurus X-3

Pulsations of 4.8 sec were detected up to energies above 38 keV by the present High Energy X-ray and Low Energy Gamma-Ray HEAO 1 satellite experiment observations of Cen X-3, and an analysis of the X-ray spectrum as a function of pulse phase indicates that the spectrum hardens during an interval of about 1.2 sec which lags the pulse peak by about 0.6 sec. The results of correlated observations of pulse period and X-ray intensity include (1) the detection of a high intensity state during which the pulse period is on the average increasing, (2) the measurement of comparable high intensities during episodes of both period increase and decrease, (3) the detection of X-ray pulsations at a much reduced level during a period of low intensity, and (4) the detection of a transition between spin-down, and spin-up episodes that coincides with a rapid decrease in X-ray intensity.

Howe, S. K.↗
NASA NTRS1983

Characteristics of gamma-ray line flares

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.↗
NASA NTRS1985

Soft-spectrum gamma-ray bursts

A typical gamma to ray burst (GRB), when observed over the approximately 30 keV to 1 MeV range, has a 1 to 10 s duration and a spectrum describable in terms of a several-hundred-keV exponential function. However, KONUS data indicate that some GRBs may belong to a separate class of short (approximately 0.1 s), soft (kT 50 keV) events. This result has been questioned because the KONUS experiments, with only 4 s spectral time resolution and a lack of information approximately 30 keV, are not particularly well suited for the detection and study of these bursts. The UC Berkely/Los Alamos Solar X-Ray Spectrometer/GRB experiment on the International Cometry Explorer (ICE), with nearly continuous coverage of approxiomately one-sixth of the sky down to 5 keV at 0.5 s resolution, is better designed for such a task. Using ICE data, it was confirmed that soft-spectrum events do indeed exist, apparently with properties that set them apart from the general GRB population. Results from the ICE experiment are presented.

Laros, J. G.↗
NASA NTRS1985

Evidence for long-term variability in the ultra high energy photon flux from Cygnus X-3

A time-correlation analysis of atmospheric Cerenkov pulses by a wide-angle photomultiplier system was previously shown to have present in it a nonrandom component which seemed associated with the Right Ascension (RA) range approx. 20+or-04h. A recent examination of multi-muon events recorded by a photon-decay detector shows a similar time-dependent effect, closely matching the previous results, supporting the suggestion that the effect is of cosmic origin. However, even though Cyg. X-3 lies well inside the region of peak intensity, it does not seem possible to ascribe to it the whole effect, for the implied photon flux appears too large to be reconciled to various gamma-ray measurements of Cyg. X-3. The original data were subjected to a phase-histogram analysis and it as found that only 2.5% of overall recorded data are compatible with a phase-dependent emission from Cyg. X-3. Assuming these events to be gamma rays yields a detected flux of (2.6 + or - 0.3) x 10 to the minus 12th power gamma cm -2s-1 above 5 x 10 to the 14th power eV. Comparing this value with more recent ultra high energy (UHE) photon data from the same source, it is suggested that the available data generally favor a long-term reduction in the Cyg. X-3 inferred luminosity ( 10 to the 13th power eV) by a factor of (1.8 + or - 0.3) per year.

Bhat, C. L.↗
NASA NTRS1985

A model for the UHE gamma-rays from Hercules X-1

An outburst of gamma rays with energies E gamma 10 to the 12th power eV was recently detected from the X-ray pulsar Hercules X-1. The outburst had a 3 minute duration and occurred at a time during the 35 day X-ray modulation that is associated with X-ray turnon. The gamma rays also have the same 1.24 second modulation that is observed at X-ray energies. Subsequently a 40 minute outburst was detected at E gamma 10 to the 14th power eV. The interaction of ultrahigh energy particles with a precessing accretion disk explain the observed gamma ray light curve. The constraints one can place on acceleration mechanisms and the possibility that the UHE particles are accelerated by shocks in an accretion flow are explained.

Eichler, D.↗
NASA NTRS1985

Search for periodicities near 59 s in the COS-B gamma-ray data of 2CG195+04 (Geminga)

The COS-B data relating to five observations in the general direction of Geminga, spanning 6.7 years, were searched for pulsation near 59 s. The SAS-2 indication is not confirmed. An indication of a 59 s pulsation in the gamma ray emission from 2CG195+04 (Geminga) was reported. Early analysis of COS-B data supported the result while later improved statistics did not confirm it. Subsequently, detection of a 59 s pulsation in the emission from the direction of Geminga at ultra high gamma and X-rays was reported. Geminga was identified with the X-ray source 1E0630+128. The final COS-B data on Geminga which was observed five times for a total of 214 days are reported.

Buccheri, R.↗
NASA NTRS1985

The gamma-ray telescope Gamma-1

French and Soviet specialists have designed and built the gamma-ray telescope GAMMA-1 to detect cosmic gamma rays above 50 MeV. The sensitive area of the detector is 1400 sq cm, energy resolution is 30% at 300 MeV, and angular resolution 1.2 deg at 300 MeV (and less than 20' arc when a coded aperture mask is used). Results on calibration of the qualification model and Monte-Carlo calculations are presented.

Akimov, V. V.↗
NASA NTRS1985

A method to improve observations of gamma-ray sources near 10 (15) eV

Now that sources of gamma rays near 10 to the 15th power eV have been identified, there is a need for telescopes which can study in detail the high energy gamma ray emissions from these sources. The capabilities of a Cerenkov detector which can track a source at large zenith angle (small elevation angle) are analyzed. Because the observed showers must then develop far from the detector, the effective detection area is very large. During a single half-hour hot phase of Cygnus X-3, for example, it may be possible to detect 45 signal showers compared with 10 background showers. Time structure within the hot phase may then be discernible. The precise capabilities of the detector depend on its mirror size, angular acceptance, electronic speed, coincidence properties, etc. Calculations are presented for one feasible design using mirrors of an improved Fly's Eye type.

Sommers, P.↗
NASA NTRS1985

Characteristics of gamma-ray line flares

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.↗
NASA NTRS1986

Results from the solar maximum mission

The major results from SMM (Solar Max Mission) are presented as they relate to the understanding of the energy release and particle transportation processes that led to the high energy X-ray aspects of solar flares. Evidence is reviewed for a 152- to 158-day periodicity in various aspects of solar activity including the rate of occurrence of hard X-ray and gamma-ray flares. The statistical properties of over 7000 hard X-ray flares detected with the Hard X-Ray Burst Spectrometer are presented including the spectrum of peak rates and the distribution of the photo number spectrum. A flare classification scheme is used to divide flares into three different types. Type A flares have purely thermal, compact sources with very steep hard X-ray spectra. Type B flares are impulsive bursts which show double footpoints in hard X-rays, and soft-hard-soft spectral evolution. Type C flares have gradually varying hard X-ray and microwave fluxes from high altitudes and show hardening of the X-ray spectrum through the peak and on the decay. SSM data are presented for examples of Type B and Type C events. New results are presented showing coincident hard X rays, O V, and UV continuum observations in Type B events with a time resolution of 128 ms. The subsecond variations in the hard X-ray flux during 10% of the stronger events are discussed and the fastest observed variation in a time of 20 ms is presented. The properties of Type C flares are presented as determined primarily from the non-imaged hard X-ray and microwave spectral data. A model based on the association of Type C flares and coronal mass ejections is presented to explain many of the characteristics of these gradual flares.

Dennis, B. R.↗
NASA NTRS1985

Remote sensing technologies for Space Missions in the second half of the nineties' decade

The remote sensing research and technology to be used in the development of future NASA missions are discussed, with consideration given to earth sciences, planetary sciences, solar physics, and astrophysics. The remote sensing missions planned in the four application areas, their payload packages, and the particular instruments that will make up these packages are described. The advanced technologies to be used include systems and devices that address the detection of radiation in the radio, microwave, millimeter wave, submillimeter wave, IR, visible, UV, X-ray, and gamma-ray parts of the spectrum, including supporting technologies, such as optics, liquid cryogen transfer systems, and 'smart' sensors.

Sokoloski, M. M.↗
NASA NTRS1985

Solar hard X-ray bursts

The major results from the Solar Maximum Mission (SMM) are presented as they relate to our understanding of the energy release and particle transportation processes that lead to the high-energy X-ray aspects of solar flares. Evidence is reviewed for a 152-158 day periodicity in various aspects of solar activity, including the rate of occurence of hard X-ray and gamma-ray flares. The statistical properties of over 7000 hard X-ray flares detected with the Hard X-Ray Burst Spectrometer are presented, including the spectrum of peak rates and the distribution of the photon number spectrum. A flare classification scheme introduced by Tanaka is used, and characteristics of the different types (types A, B, and C) are noted. A model based on the association of type C flares and coronal mass ejections is presented to explain many of the characteristics of these gradual flares.

Dennis, B. R.↗
NASA NTRS1986

Double layers and circuits in astrophysics

A simple circuit is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the Sun's axis which may give radiations detectable from earth. Double layers in space should be classified as a new type of celestial object. It is suggested that X-ray and gamma-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). The way the most used textbooks in astrophysics treat concepts like double layers, critical velocity, pinch effects and circuits was studied. It is found that students using these textbooks remain essentially ignorant of even the existence of these, although some of the phenomena were discovered 50 yr ago.

Alfven, Hannes↗
NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗