Optical search for gamma-ray bursts

The preliminary results from optical search for light pulses associated with gamma ray bursts by means of the Czechoslovak Fireball Network plate collection at the Ondřejov observatory are given. Optical monitoring represents more than 7700 hours, but no real optical counterpart was found. Problems associated with the optical search for gamma ray bursts are discussed.     

Developments in high-precision gamma-ray burst source studies

The first interplanetary gamma-ray burst spacecraft network is making possible the precise determination of gamma-ray burst source locations. This network is an international cooperation involving the Helios-2, Pioneer Venus, Venera-11, Venera-12, ISEE-3 and Prognoz-7 spacecraft. The celestial regions that have been defined, with one exception, have no correlations either to known x-ray emitters or to steady optical counterparts, to ～ 22nd mag. The event of 1979 March 5 has a very small source field located within the contour of the supernova remnant N49 in the LMC; the possibility of this measurement as a source identification, the 55 kpc distance of N49 as opposed to the nearby source distances assumed for typical bursts, and the very different characteristics of this event, however, are three arguments for its separate classification. The recent identification of an archived, 50-year old, optical transient within the high-precision source field of a typical burst [1] suggests both that events may repeat and that sources may be localized with even greater accuracy optically.This review outlines the precise source location data being produced by the first and the second spacecraft networks, the possibilities of additional networks and of related studies in other disciplines, and the prospects both for real-time optical transient observations and for the definition of gamma-ray burst sources by optical transient astronomy.     

Multilateration Error Ellipsoids

Formulas are derived for the lengths and direction cosines of the semiaxes of error ellipsoids in three-dimensional multilateration, in terms of the rms errors and direction cosines of the distance measurements, for the case in which random measurement errors are normally distributed and systematic errors are negligible. Two-dimensional error ellipses also are discussed.     

A high-resolution Ge spectrometer for Gamma-Ray burst astronomy

The Transient Gamma-Ray Spectrometer (TGRS) to be flown aboard the WIND spacecraft is primarily designed to perform high resolution spectroscopy of transient -ray events, such as cosmic -ray bursts and solar flares over the energy range 25 keV to 8.2 MeV with an expected spectroscopic resolution of 3 keV at 1 MeV. The detector itself consists of a 215 cm³ high purityn-type Ge crystal kept at cryogenic temperatures by a passive radiative cooler. The geometric field of view defined by the cooler is 1.8 steradian. To avoid continuous triggers by soft solar events, a thin BeCu Sun-shield around the sides of the cooler has been provided. A passive Mo/Pb occulter, which modulates signals from within ±5° of the ecliptic plane at the spacecraft spin frequency, is used to identify and study solar flares, as well as emission from the galactic plane and center. Thus, in addition to transient event measurements, the instrument will allow the search for possible diffuse background lines and monitor the 511 keV positron annihilation radiation from the galactic center. In order to handle the typically large burst count rates, which can be in excess of 100 kHz, burst data are stored directly in an onboard 2.75 Mbit burst memory with an absolute timing accuracy of ±1.5 ms after ground processing. The memory is capable of storing the entire spectral data set of all but the largest bursts. WIND is scheduled to be launched on a Delta II launch vehicle from Cape Canaveral on November 1, 1994. After injection into a phasing orbit, the spacecraft will execute a double lunar swing-by before being moved into a controlled halo orbit about theL1 Lagrangian point (250R _e towards the Sun). This will provide a 5 light-second light travel time with which to triangulate gamma-ray burst sources with Earth-orbiting systems, such as those on-board the Gamma-Ray Observatory (GRO). The response of instrument to transient -ray events such as GRB's and solar flares will be presented as well as the expected response to steady state point sources and galactic center line emission.     

Konus-W gamma-ray burst experiment for the GGS Wind spacecraft

The Konus-W experiment to be flown on board the GGS-Wind spacecraft is designed to observe gamma-ray bursts and solar flares with moderate spectral and high time resolution. Two large scintillators are used to provide omnidirectional sensitivity. The primary scientific objectives are the study of the continuum energy spectra and spectral features of these events in the energy range of 10 keV to 10 MeV, as well as their time histories in soft, medium, and hard energy bands, with a time resolution to 2 ms.