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Discussions are presented of the associations between cosmic gamma ray bursts and transient X-ray sources, and the release of gravitational binding energy during the formation of neutron stars. The model for studying the associations is described along with the release of neutrinos during the collapse of white dwarfs.
The gamma-ray bursts reported by Klebesadel et al. (1973) are considered. It is suggested that these outbursts are simply giant versions of the X-ray bursts typically seen in solar flares. The time scale, mean photon energy, and energy spectrum shape for both the solar and nonsolar bursts are found to be strikingly similar. However, the nonsolar bursts that have been observed have a much greater intrinsic intensity than their solar counterparts.
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.
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.
Several experiments are outlined which are designed for investigating cosmic gamma ray bursts; they form a research program that includes balloon experiments currently under development and satellite experiments proposed for future missions. The satellite proposals, in most cases, are either suggested for payloads that are presently defined as to experimental complement, or are for hypothetical spacecraft. Thus, these proposals at present serve to indicate, at least, the possible usefulness of various space missions for cosmic gamma-ray burst studies. Taken as a whole, this program of gamma ray burst experiments should improve on the present observations of the temporal variations, size spectrum, energy spectra, polarizations, directional locations and distribution of source directions, each by several orders of magnitude of improved resolution or of dynamic range.
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.
The discovery of soft gamma ray bursts has led to the speculation that these bursts are caused by the bremsstrahlung of electrons accelerated to high energies in a stellar flare event. If the stellar flare hypothesis is verified, it may imply a significant source of low energy cosmic rays in the solar neighborhood, depending on the frequency and intensity of the flares.
Cosmic soft gamma ray bursts are discussed, and the stellar super-flare hypothesis is supported. Previous predictions and observations of gamma ray bursts are cited. Studies show that it is plausible that the bursts are caused by the bremsstrahlung of electrons accelerated to high energies in a stellar flare event. Possible observational consequences are listed for the stellar flare hypothesis.
The occurrence of intense, short bursts of 0.1 to 1.2 MeV cosmic gamma rays, recently found using multiple Vela satellites was confirmed with measurements from the IMP-6 satellite. Observations regarding times of occurrence, photon flux, and temporal and spectral characteristics of the bursts are outlined. In particular, since the IMP-6 instrument incorporates a hard X-ray detector with active particle rejection and full-time omnidirectional particle intensity monitoring, the results fully confirm and establish the hard X-ray or gamma-ray nature of the incident flux. Detailed differential energy spectra were obtained with the IMP-6 for six of the eight known events occurring during the March 1971 to September 1972 lifetime of the instrument. All of these are multiple-pulse events, with several seconds separation between distinct pulses of one or two seconds duration. The pulse spectra do not obey single-index power laws in energy, but can be represented by exponentials in photon flux throughout the 100 to 1200 KeV region.
Data are reported that show observations made by IMP-6 may make it possible to detect a number of cosmic gamma ray bursts in addition to those previously cataloged. Selection criteria are based on consistent time scale and observable intensity only. In addition, a differential energy analyzer with simultaneous storage was used making it possible to search for intensity increases simultaneously in several channels.
Possible alternatives to the supernovae theory on the orgin of cosmic ray bursts are examined. In particular, the possibility that these outbursts are simply giant versions of the X-ray burst typically seen in solar flares is investigated. It was suggested that the outbursts are caused by the bresstrahlung of electrons accelerated to high energies in a stellar flare event.
The possibility that soft gamma ray bursts are versions of X-ray bursts typically seen in solar flares and not products of supernovae events is investigated. Results show that the bursts have longer time scales that those predicted for supernovae events. It was suggested that the bursts result from the acceleration of electron bremsstrahlung to high energies in a stellar flare event.
The StarBurst Multimessenger Pioneer is a small satellite mission serving as a wide-field gamma-ray observatory designed to capture the initial emissions of short gamma-ray bursts, electromagnetic signatures of neutron star mergers. This paper presents the final thermal design and analysis of the StarBurst Instrument, comprising the bus-to-instrument interface plate, control electronics, and twelve crystal detector units, which form the core of the mission’s science capability. The passive thermal control system design requires consideration of restrictive keep-out zones, unknown orbital parameters, and narrow temperature limits of the detectors. Also summarized is the instrument level thermal vacuum cycle test, correlated model refinements, and updated model results. Following successful completion of the instrument test campaign, the hardware was integrated with the spacecraft bus for spacecraft level testing, including additional thermal vacuum testing. The results from the spacecraft level thermal vacuum test will further inform the instrument thermal model, ensuring accurate flight temperature predictions. StarBurst launches as a secondary payload in 2027 and has a mission duration of at least one year.
The StarBurst Multimessenger Pioneer is a small satellite mission serving as a wide-field gamma-ray observatory designed to capture the initial emissions of short gamma-ray bursts, electromagnetic signatures of neutron star mergers. This paper presents the final thermal design and analysis of the StarBurst Instrument, comprising the bus-to-instrument interface plate, control electronics, and twelve crystal detector units, which form the core of the mission’s science capability. The passive thermal control system design requires consideration of restrictive keep-out zones, unknown orbital parameters, and narrow temperature limits of the detectors. Also summarized is the instrument level thermal vacuum cycle test, correlated model refinements, and updated model results. Following successful completion of the instrument test campaign, the hardware was integrated with the spacecraft bus for spacecraft level testing, including additional thermal vacuum testing. The results from the spacecraft level thermal vacuum test will further inform the instrument thermal model, ensuring accurate flight temperature predictions. StarBurst launches as a secondary payload in 2027 and has a mission duration of at least one year.
Gamma-ray fluxes between 25 keV and 6 MeV were observed by instruments aboard the Environmental Research Satellite-18 (ERS-18)during the great solar flares of May 21 and May 23, 1967. Measurements were made with a 6.35-cm-diameter by 7.65-cm-long Nal scintillation counter with five differential channels between 0.25 and 6.0 MeV. Data obtained during the event at 1945 UT on May 23, 1967, can be fitted by a two-part, power-law, differential-number spectrum. One part is of spectral index 3.2 between 8 keV and 0.6 MeV, and the other is of spectral index 1.2 above 0.6 MeV. An upper limit of 0.52 photons is set for 2.23 MeV line strength for this event. In all three bursts, tentatively associated with white light flares, the MeV-range fluxes declined more slowly than the 25-keV fluxes.
Gamma ray astronomy in the 50 kev to 3 mev region
The sensitivity of a directional gamma ray detector, which relies on blocking a source to determine its direction and energy spectrum, is calculated and compared to the more conventional well-shaped shielded detectors. It is shown that such an anticollimator detection system provides a basis for measuring the celestial diffuse gamma ray background, gamma ray sources and bursts with good energy, angular, and time resolution, and that additionally the system is 20 to 50 times as sensitive as conventional detectors when compared on a per unit mass basis.
The sensitivity of a directional gamma ray detector, which relies on blocking a source to determine its direction and energy spectrum, is calculated and compared to the more conventional well shaped shielded detectors. It is shown that such an anticollimator detection system provides a basis for measuring the celestial diffuse gamma ray background, gamma ray sources and bursts with good energy, angular, and time resolution, and that additionally the system is 20 to 50 times as sensitive as conventional detectors when compared on a per unit mass basis.