Engineering topics

Klebesadel, R. W.

Publications and source records attributed to Klebesadel, R. W..

At least 55 records · Page 3

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 NTRS1980

Gamma-ray burst observations from the UCB/LASL experiment of ISEE-3

The University of California at Berkeley (UCB)/Los Alamos Scientific Laboratory (LASL) gamma-ray burst experiment on board ISEE-3 is described and initial results of the experiment are presented. The instrument consists of an X-ray spectrometer originally designed to monitor solar emission continuously over the energy range 4.8-1264 keV with additional electronics to record data from the intense, short-lived gamma ray bursts at a very high rate and with good timing accuracy. Since the launch of ISEE-3 into a heliocentric orbit at the inner Lagrangian point in August, 1978, the UCB/LASL experiment has detected and recorded 12 gamma-ray bursts, including the unusually intense burst of November 4, 1978, which exhibited most of the classical gamma-ray burst characteristics, the intense burst of November 19, 1978, with an atypical time history and an unusually hard spectrum, and the extended burst of March 7, 1979. The spectral and temporal data demonstrate the diverse nature of the gamma-ray burst phenomenon, and are currently being combined with those of the Pioneer Venus Orbiter and Venera 11 and 12 to obtain accurate burst locations.

Evans, W. D.↗

NASA NTRS1980

Directivity of 50-100 keV X-ray emission from impulsive solar flares

Stereoscopic observations of 50-100 keV solar X-rays, made with two spacecraft in heliocentric orbit, have been used to measure the directivity of impulsive solar X-ray bursts. The observations are consistent with an essentially isotropic emission of 50-100 keV X-rays over observation angles between 13 and 79 deg.

Kane, S. R.↗

NASA NTRS1980

Periodicity of the gamma-ray transient event of 5 March 1979

An unusual gamma-ray burst event was observed on 5 March 1979 by nine different spacecraft. The position of the event has been accurately determined as r.a. = 5 h 25.95 min, dec = -66 deg 07.1 arcmin (epoch 1950.0), coincident with the location of the supernova remnant N49 in the Large Magellanic Cloud. The burst was of very high intensity, and if isotropic and located at the distance (approximately 55 kpc) of N49 had a peak luminosity of greater than 10 to the 44th erg/sec. Even more interesting is the obvious 8-s periodicity of the event, following the initial very intense outburst. The time history and power spectrum of this event as determined from Pioneer Venus Orbiter data is here reported.

Terrell, J.↗

NASA NTRS1980

Detection of a fast, intense and unusual gamma-ray transient

An unusual transient pulse of greater than approximately 50 keV photons was detected on March 5, 1979 by the gamma-ray burst sensor network using nine space probes and satellites. Its characteristics are unlike those of the known variety of gamma-ray bursts and therefore suggest that it was formed either by a completely different origin species or in a very different manner. In a companion Letter it is identified with the LMC supernova remnant N49.

Cline, T. L.↗

NASA NTRS1980

Location of the gamma-ray transient event of 1979 March 5

The paper discusses the gamma event of Mar. 5, 1979, the most intense burst of nonsolar high-energy photons ever recorded, which was observed by 12 gamma burst instruments on nine spacecraft. The fast rise time of the event and ephemeris and absolute time information from the spacecraft are considered, and a unique and redundantly determined 1 x 2 arcmin error box centered at R.A. = 5h 25.95m, decl. = -66 deg 07.1 arcmin (equinox 1950.0) is found. Statistical arguments favor identification with the SNR N49, located within the box. It is suggested that if N49 was the source of the transient, then peak gamma-ray and hard X-5ay luminosity was between 10 to the 44th and 10 to the 45th ergs/s, and the total radiated energy was between 10 to the 43rd and 10 to the 44th ergs.

Evans, W. D.↗

NASA NTRS1980

The Pioneer Venus Orbiter Gamma Burst Detector

The Orbiter Gamma Burst Detector was designed to record the temporal and spectral characteristics of cosmic gamma-ray bursts. The primary mission of the experiment is the accurate determination of the directions to the sources of such bursts through a technique of triangulation as a member of a widely spaced array of similar instruments. The system consists of a pair of scintillation spectrometers sensitive in the range of energies between 100 and 2000 keV, together with logic and data storage to provide a capability for recording these events. Nineteen events which have been verified as cosmic gamma-ray bursts were recorded within the first year's operation.

Klebesadel, R. W.↗

NASA NTRS1980

Gamma-ray burst source locations

Instrumentation for observing cosmic gamma-ray bursts has been provided for widely separated spacecraft, including the Pioneer Venus Orbiter, ISEE-3, Helios-B, Venera 10 and 11, and Prognoz 7. Simultaneous observations have been made of several gamma bursts with various combinations of these spacecraft and near-earth satellites. Locations of the gamma-burst sources have been calculated for those events where precise timing and ephemeris data are available. The results of optical and HEAO-B observations of the resultant error boxes will be discussed.

Evans, W. D.↗

NASA NTRS1979

Observation of an impulsive solar X-ray burst from a coronal source

Observations of the spatial, spectral, and temporal structure of an impulsive hard X-ray source in a behind-the-limb solar flare have been made with high-time-resolution hard X-ray detectors aboard two spacecraft, the International Sun Earth Explorer 3 (ISEE 3) and the Pioneer Venus Orbiter (PVO), which were separated in heliographic longitude by about 12.5 deg. The principal findings are that (1) the coronal part of the X-ray source is about 600 times less intense than the lower-altitude part of the source; and (2) the coronal X-ray observations are consistent with a power-law electron spectrum which extends down to about 5 keV.

Kane, S. R.↗

NASA NTRS1979

Detection of a fast, intense and unusual gamma ray transient

An unusual transient pulse of approximately 50 keV was detected by the gamma-ray burst sensor network using nine space probes and satellites. Its characteristics are unlike those of the known variety of gamma-ray bursts and therefore suggest that it was formed either by a completely different origin species or in a very different manner. It is identified with the LMC supernova remnant N49.

Cline, T. L.↗

NASA NTRS1979

Gamma-ray burst observations from Helios 2

Observations of five gamma-ray bursts made with the solar orbiter Helios 2 are reported. Wavefront timing from Helios 2, at distances of up to 1.98 AU, to Vela 5A and 6A, in earth orbit, provides source location bands as narrow as 2 arcmin, although several degrees in length. The burst intensities and time profiles measured in interplanetary space by Helios 2 are the same as those observed near the earth, ruling out a narrow-beam interplanetary origin model. Also, the source direction bands for these events are inconsistent with the directions of all known celestial X-ray objects, X-ray bursters, and high-energy gamma-ray source regions. The gamma-ray burst source objects therefore appear to form a class distinct from all lower-energy X-ray or higher energy gamma-ray emitters.

Cline, T. L.↗

NASA NTRS1979

Gamma-ray burst observations by Pioneer Venus Orbiter

The Pioneer Venus Orbiter gamma burst detector is an astrophysics experiment for monitoring cosmic gamma-ray bursts. It is included in this planetary mission to provide a long baseline for accurately locating the sources of these bursts in order to identify them with specific astronomical objects. Responses to 14 gamma-ray burst events were examined; these events were verified from data acquired by other systems. Preliminary locations are proposed for three events, based on data from the Pioneer Venus Orbiter, ISEE C, and Vela spacecraft. These locations will be improved, and additional locations will be determined by including in the analyses data from Helios B and the Russian Venera 11, Venera 12, and Prognoz 7 spacecraft.

Evans, W. D.↗

NASA NTRS1979

Gamma-ray burst observations from Helios-2

Observations of five gamma-ray bursts made with the solar orbiter Helios-2 are reported. Wavefront timing from Helios-2, at distances of up to 1.98 AU, to Vela-5A and -6A, in Earth orbit, provides source location bands as narrow as 2 arc minutes, although several degrees in length. The burst intensities and time profiles measured in interplanetary space by Helios-2 are the same as those observed near the earth, ruling out a narrow-beam interplanetary origin model. Also, the source direction bands for these events are inconsistent with the directions of all known celestial X-ray objects, X-ray bursters and high-energy gamma-ray source regions. The gamma-ray burst source objects therefore appear to form a distinct class from all lower energy X-ray or higher energy gamma ray emitters.

Cline, T. L.↗

NASA NTRS1979

Helios-2 Vela-Ariel-5 gamma-ray burst source position

The gamma-ray burst of 28 January 1976, one of 18 events thus far detected in interplanetary space with Helios-2, was also observed with the Vela-5A, -6A and the Ariel-5 satellites. A small source field is obtained from the intersection of the region derived from the observed time delays between Helios-2 and Vela-5A and -6A with the source region independently found with the Ariel-5 X-ray detector. This area contains neither any steady X-ray source as scanned by HEAO-A nor any previously catalogued X-ray, radio or infrared sources, X-ray transients, quasars, seyferts, globular clusters, flare stars, pulsars, white dwarfs or high energy gamma-ray sources. The region is however, within the source field of a gamma-ray transient observed in 1974, which exhibited nuclear gamma-ray line structure.

Cline, T. L.↗

NASA NTRS1978

X-ray spectrometer experiment aboard the ISEE-C /Heliocentric/ spacecraft

This experiment is designed to provide continuous coverage of solar flare X-ray bursts and transient cosmic gamma-ray bursts. A proportional counter and a scintillation detector together cover the energy range from 5 to 228 keV with good sensitivity, large dynamic range, and high temporal resolution. This experiment provides data storage capability and good absolute timing so that in conjunction with similar experiments on other spacecraft, accurate source locations can be obtained for cosmic gamma-ray bursts.

Anderson, K. A.↗

NASA NTRS1973

The direction and spectral variability of a cosmic gamma-ray burst

Description of the simultaneous observations of a gamma-ray event by five different satellites on May 14, 1972 in widely differing geomagnetic environments. The direction of the source was unambiguously determined, and it is concluded that the event was real and not caused by some unexplained spurious or instrumental effects. Since the obtained direction is far from the earth and the sun, the conclusion is that this gamma-ray event was almost certainly of cosmic origin. The total energy at the earth in this event was about .0005 ergs/sq cm from 11 to 1500 keV.

Wheaton, W. A.↗

NASA NTRS1973

Energy spectra of cosmic gamma-ray bursts.

Spectral measurements of six cosmic gamma-ray bursts ranging in energy from 0.1 to 1.2 MeV are reported. These measurements, obtained by means of a semiomnidirectional X-ray detector on the IMP-6 satellite, confirm the hard X-ray or gamma-ray nature of the bursts, as inferred from the original observations by Klebesadel et al. (1973), and show that their maximum energy release is of this several-hundred keV magnitude.

Cline, T. L.↗

NASA NTRS1973

Energy spectra of cosmic gamma-ray bursts

Spectral measurements of six cosmic gamma-ray bursts in the energy region of 0.1 to 1.2 MeV, made using a semi-omnidirectional X-ray detector on IMP-6 are reported. These measurements confirm the hard X-ray or gamma-ray nature of the bursts, as inferred from the original observations by Klebesadel et al., (1973), and show that their maximum energy release is in this several hundred keV region. Each burst consists of several 1 or 2-second pulses each with the characteristic spectrum of approximately 150-keV exponential, followed by a softer decay. There is no evidence of line structure in this energy region, or for a marked change in the energy spectrum within a given pulse. Event size spectra are estimated for galactic and extragalactic models; the total emission is consistent with present measurements of the diffuse background, and unlikely to account for any spectral feature in the few-MeV region.

Cline, T. L.↗