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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.
An examination was made of black body emission as a possible radiation mechanism for cosmic ray bursts. It was suggested that black body radiation of variable temperature causes the bursts. Temperature variations are caused by cooling due to gamma ray emission.
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.
Detailed differential energy spectra from gamma ray bursts obtained by IMP-6 are presented. Observations cover times of occurance, photon flux, and temporal and spectral characteristics.
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.
A burst of X-rays was detected during the trans-earth coast phase of Apollo 16 on Apr. 27, 1972 at 10:68 UT, simultaneously with the observation of a transient event by a gamma-ray spectrometer aboard the same spacecraft. The two instruments provide a broad energy range of more than three orders of magnitude for describing the spectral distribution of this event. The conclusion that the incident flux was X-rays and not charged particles is based on the fact that the particle flux detectors in the Apollo gamma ray spectrometer and on the Vela 6A, which also observed the event, did not respond. The time variation of the total count rate in the X-ray range before and after corrections for detector geometry and the analysis for source direction is presented.
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.
Consideration of events by which both s- and r-process nucleosynthesis may occur on the surfaces of white-dwarf stars. The main requirement is that the accreted hydrogen be mixed with comparable numbers of C-12 (or other alpha nuclei) before a runaway capture of protons takes place. Subsequent events offer many possibilities for nucleosynthesis and stars of peculiar composition. A new mechanism for a surface s-process due to few-MeV protons is also described. Concluding comments concern cosmic gamma-ray bursts and the origin of anomalous low-energy galactic cosmic rays.
Expanding upon the authors' earlier work, Hoyle and Clayton (1974) have suggested that a thermonuclear runaway in a white dwarf envelope that consists of equal numbers of protons and C-12 nuclei will produce the s or r-process elements. The present work studies such a runaway and finds that these initial conditions cause a 'super' nova outburst that does not result in any s or r-process nucleosynthesis. However, the model is very interesting in that it reaches peak temperatures of 1.6 billion K and peak burning rates exceeding 2 times 10 to the 23rd erg/gm/sec. A shock forms and ejects 10 to the 29th grams moving with speeds up to 60,000 km/sec. The peak bolometric magnitude is -21.2 and this model will also produce a gamma-ray burst.
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.
The occurrence of intense bursts of 0.1- to 1.5-MeV photons from space has been confirmed with observations from IMP-6. This is the first positive result of an extensive data comparison, in which a search was made of OGO and IMP records for time coincidences between brief X- or gamma-ray increases and a variety of other transient phenomena. The IMP-6 measurements provided the first differential energy spectra of these events, the shapes of which indicate that photons predominantly in the gamma-ray domain are released into space. Whether these bursts originate in distant supernovae or in some new class of relatively nearby gamma-ray flare stars, they reveal a process which is new to high-energy astrophysics, not only because of the unusual spectrum, but also because of the brief time scales involved and because of the intense fluxes observed.
The OSO 7 scientific findings reveal hitherto unknown processes in solar flares and some remarkable properties of the corona. Gamma-ray emission lines provide evidence of nuclear reactions in solar flares. The measurements were made during the large flares of Aug. 4 and 7, 1972. The data clearly show line emission at energies of about 0.5 MeV (million electron volts) and 2.2 MeV, with weaker enhancements at 4.4 MeV and 6.1 MeV. It appears that the nuclear processes in flares as revealed by OSO 7 are probably thermal reactions. Some flare electron streams also produce bursts of hard X rays. Holes and poles in the corona, and coronal streams and the interplanetary blast were studied.
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.
Accomplishments in the fields of X-ray and gamma ray astronomy are discussed. Data obtained from IMP and OGO satellites are analyzed to determine the sources of interplanetary radiation bursts. The energy spectrum of cosmic gamma ray bursts as observed by IMP-6 is described. The application of cooling blackbody techniques as a method for examining cosmic gamma ray bursts is reported. The experimental results and theoretical interpretation of high energy diffuse gamma rays are investigated. The structure of the SAS-2 satellite is depicted and the accomplishments are examined. Other sources of gamma radiation to include galactic fermi, Cygnus X-1, supernovae, and the planet Jupiter are proposed. Data obtained from the Pioneer 10 space probe are presented in graph form.