Gamma-ray Transients Research Articles

SIGMA observations of two new hard X-ray and soft gamma-ray transients: GX 354-0 and Nova Persei

We report the first detection of two soft gamma ray transients GX 354-0 and Nova Persei (GRO J0422+32) by the coded-mask telescope SIGMA. Only preliminary results are presented with regard to Nova Persei while special emphasis is given to the data on GX 354-0 which has been monitored during the 1992 February–April survey of the Galactic Center. GX 354-0 underwent two flares of about two week duration and its average spectrum is well described by a thermal Bremsstrahlung model or a broken power law whereas the Nova Persei spectrum seems to be similar to the one observed for GRS 1124-684 in Musca.

SMM Observations of Gamma-Ray Transients. I. A Search for Variable Emission at MeV Energies from Five Galactic and Extragalactic Sources

Transient emission at energies near 1 MeV has been reported by previous experiments on time scales of weeks to months from the Galactic center, the Crab Nebula, and Cyg X-1, and on shorter time-scales from NGC 4151 and Cen A. The spectra of these events call into two broad classes: a broad line-like feature centered near 1 MeV, and continuum emission (or a very broad feature) extending from ∼600 keV up to several MeV. These features have been interpreted theoretically in terms of emission from hot pair-dominated plasmas, which may be the necessary positron source implied by reports of narrow e - e + annihilation lines from Cyg X-1 and the Galactic center

Concept of an all-directional high-energy cosmic gamma ray telescope

Point sources in the region of hard gamma rays 30 MeV-10 GeV were identified with single young pulsars, like Crab; transient gamma ray sources and bright quasars. The main problem in this region is the small number of the photons, registrated from the source. In order to overcome this problem the new construction of a gamma telescope is proposed, which registers quanta from all directions simultaneously. In this way it is possible to increase the sensitivity by more than an order of magnitude with the same size and smaller weight, in comparison with EGRET. Analyses have shown, that such a telescope must stay without the calorimeter, what reduces its spectral resolution. The estimated number of point sources which could be discovered by such a telescope could approach one thousand. Results of Monte Carlo simulations are presented.

A study of focusing telescopes for soft gamma rays

A study is presented on the feasibility of using Bragg diffraction from crystals to focus soft gamma-rays in the energy range up to 2 MeV. For astrophysics this band contains several very interesting gamma-ray lines from novae, supernovae and X- and gamma-ray transients.

The ground support equipment for the transient gamma-ray spectrometer

We describe the function and implementation of the ground support equipment (GSE) for the transient gamma-ray spectrometer (TGRS), to be flown on-board

New insights on cosmic gamma-ray bursts from the APEX experiment

The Soviet-French experiment APEX (Barat et al., 1989. Instruments and Methods far Space Studies (Edited by Balebanov, V. M.), pp. 213–218) was designed to record cosmic gamma-ray transients in the 64 keV–9.2 MeV energy range. Between July 1988 and February 1989 about 80 cosmic gamma-ray bursts (GRBs) were detected, of which 50 were sufficiently strong to allow a study of their fine time/energy structure. This paper reviews the first results obtained at the time of the Phobos meeting, its goal is to point out interesting features appearing in the APEX data for 13 bursts. A detailed analysis of these observations is now under way, and results will be published in the near future. Although GRB time histories generally involve series of peaks with characteristic durations of several seconds, rich multi-pulse time structures on timescales down to several milliseconds are often observed within pulses. With a time resolution of several tens of milliseconds we have obtained evidence for fast spectral evolution ; various spectral components are found to vary on this scale. The observations show the previously known (Mazets et al., 1981. Nature 290, 378) absorption-like features below 100 keV as well as spectral features (either broad or line-like) in the range 200–1200 keV. A general conclusion is drawn that both multi-pulse time histories and multi-component energy spectra reflect the complex time/energy behaviour of cosmic GRBs. The observations could be explained by the superposition of variable elementary sources radiating gamma-rays in the vicinity of a neutron star.

TL Dosimetry Using Bricks and Tiles for Measurement of Transient Gamma Ray Dose in Inhabited Areas

Abstract The pre-dose TL technique was used to measure accrued dose in three brick samples removed from houses in a community which was formerly the site of a uranium mill. The samples were analysed using a variety of pre-dose methods, including thermal activation characteristic (both multiple activation and additive dose), the multiple activation method, modified additive dose method, modified additive dose with anneal, and additive dose method. Results reveal no significant differences between the two laboratories or between methods with the exception of the multiple activation method, which showed signs of non-linearity by one method of analysis. The additive dose method displayed the highest level of uncertainty and produced the highest dose estimates in two of the three samples. Changes in degree of sensitisation resulting from heating effects and shifts in thermal activation characteristics are examined in detail. None of the samples revealed accrued doses which were significantly higher than background dose measurements.

TL Dosimetry Using Bricks and Tiles for Measurement of Transient Gamma Ray Dose in Inhabited Areas

TL Dosimetry Using Bricks and Tiles for Measurement of Transient Gamma Ray Dose in Inhabited Areas

Fast transient X-rays and gamma ray bursts—are they stellar flares?

Short period transient X-ray emissions (FTX) have been observed from several sources in the sky and the largest single group of objects identified with such sources are active stars - flare stars and RS CVn binaries. We study the number, source and flux distribution of the fast transient X-ray sources and show that all the FTX emission can be treated as flares in the interbinary regions of active stars. We further suggest that the FTX emission is a common feature of the gamma ray bursts (GRBs). We discuss the evidence for the similarity between the hard X-ray flares and GRBs. We examine the possibility that the gamma ray bursts are the impulsive precursors of FTX originating from active stars with large scale magnetic activity.

GAMMA RAY LINES FROM THE GALACTIC CENTER AND GAMMA RAY TRANSIENTS*

The observations and interpretations of cosmic (nonsolar) gamma ray lines are discussed. The most prominent of these lines is the e(+)e(-) annihilation line which was observed from the Galactic Center and from several gamma ray transients. At the Galactic Center the e(+)e(-) pairs are probably produced by an accreting massive black hole (solar mass of approximately one million) and annihilate within the central light year to produce a line at almost exactly 0.511 MeV. In gamma ray transients the annihilation line is redshifted by factors consistent with neutron star surface redshifts. Other observed transient gamma ray lines appear to be due to cyclotron absorption in the strong magnetic fields of neutron stars, and nuclear deexcitations and neutron capture, which could also occur on or around these objects.

A search for radio emission associated with the 1978 November 19 gamma-ray burster

view Abstract Citations (34) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A search for radio emission associated with the 1978 november 19 gamma-ray burster. Hjellming, R. M. ; Ewald, S. P. Abstract VLA maps of the field of the gamma-ray transient of 1978 November 19 show a number of radio sources, some of which are candidates for association with the gamma-ray source. The two strongest, linearly polarized (3%) sources may be the outer double of a Sco X-1-like triple radio source, whose central source is inside the error region of the gamma-ray transient. These three radio sources, and a fourth weak source inside the error region for the location of the gamma-ray source, are not coincident with any optical image on ESO prints. The locations of these four radio sources deserve further searches for time variability, proper motion, more Sco X-1-like characteristics, or association with weak X-ray sources or very faint stars. Publication: The Astrophysical Journal Pub Date: June 1981 DOI: 10.1086/183570 Bibcode: 1981ApJ...246L.137H Keywords: Astronomical Maps; Gamma Ray Bursts; Radio Emission; Radio Sources (Astronomy); Neutron Stars; Position (Location); Astronomy full text sources ADS | data products SIMBAD (18)

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.

Atmospheric fluorescence as a means of detecting X-ray and gamma ray transients

The possibility of detecting some of the recently reported X-ray and gamma ray bursts by their atmospheric fluorescence in the near ultraviolet is considered. It is shown that some of these phenomena may be detectable with the large optical detectors now under construction.