摘要:

We review the theoretical arguments leading to the thermal synchrotron model of cosmic gamma ray bursts. We propose a magnetic flare‐resonant absorption mechanism for the production of the hot electrons that can account for most of the unusual properties of the emission layer.

ISSN:0094-243X    

DOI:10.1063/1.34565

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We calculate self‐consistent model atmospheres of bursting neutron stars. It is found that for effective temperatures &thgr;e≡kT/mc2∼0.1, the equilibrium density ofe−‐e+pairs in the atmosphere is one to few hundred times larger than the proton density. However, the effect of photon production by pair annihilations on the emergent spectrum is only marginal. For &thgr;e≲0.1, this spectrum is roughly described by a black body with reduced intensity due to the increased Thomson optical depth of thee−‐e+pairs.

ISSN:0094-243X    

DOI:10.1063/1.34566

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The synchrotron radiation spectra of mildly relativistic elecrons injected into strong fields (B∼1012G) are calculated by a Monte Carlo technique. The energy losses, extremely rapid for such field strengths, are taken into account self‐consistently. For photon energies below 1 MeV, the results are well fit by the product of a power law and an exponential, and the exponent and characteristic energy are tabulated with field strength and injection energy.

ISSN:0094-243X    

DOI:10.1063/1.34567

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Positron‐electron pair densities for a thermal plasma in the steady‐state equilibrium where pair production balances pair annihilation are found as a function of temperature kT/mc2≲1 source size R and magnetic field strength B. When the plasma is strongly magnetized, B≳1012G, the important processes are synchrotron radiation, one‐photon (magnetic) pair production and two‐photon pair annihilation. An analytic solution for the equilibrium pair density, found under certain simplifying assumptions, shows that optically thin equilibria exist only for sufficiently small source sizes.

ISSN:0094-243X    

DOI:10.1063/1.34568

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We review here the first observations of solar hard X‐ray bursts obtained with a combination of a high spectral resolution, ≲1 keV, germanium spectrometer and a large area, low background, NaI/CsI phoswich scintillation detector. In observations of a large flare, the Ge spectrometer was able to identify for the first time a superhot, ≳3×1070K thermal component whose spectrum is too steep for measurement by scintillation detectors. With the high sensitivity of this detector complement, a total of ∼25 solar hard X‐ray bursts with peak fluxes ∼10‐102times smaller than in solar flare hard X‐ray bursts were observed in 141 minutes of observation. These hard X‐ray microflares last a few to a few tens of seconds. The integral number of bursts varies as the inverse of the peak flux down to the sensitivity limit of the measurements. These observations suggest that even small transient releases of energy by the Sun may be non‐thermal in character.

ISSN:0094-243X    

DOI:10.1063/1.34569

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The theory of neutron and gamma‐ray production in flares is reviewed and comparisons of the calculations with data are made. The principal conclusions pertain to the accelerated proton and electron numbers and spectra in flares and to the interaction site of these particles in the solar atmosphere. For the June 21, 1980 flare, from which high‐energy neutrons and high‐energy (≳10 MeV) photons were seen, the electron‐to‐proton ratio is energy dependent and much smaller than unity at energies greater than 1 MeV. The interaction site of these particles appears to be the solar chromosphere.

ISSN:0094-243X    

DOI:10.1063/1.34570

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Near the end of this decade, the X‐ray Timing Explorer (XTE) will provide X‐ray astronomers with a tool of unprecedented sensitivity for the study of compact X‐ray sources. The principal instruments, a 1 m2proportional counter array and a 2000 cm2phoswich array, will view the sky through coaligned one‐degree collimators and provide high sensitivity over a 2‐200 keV energy range. During the course of each satellite orbit, the entire sky will be scrutinized by the sky monitor experiment to a sensitivity of 0.05 Crab.

ISSN:0094-243X    

DOI:10.1063/1.34572

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The Burst and Transient Source Experiment (BATSE) is a sensitive, all‐sky monitor for the Gamma‐Ray Observatory (GRO). The eight scintillation detector modules of BATSE are positioned around the GRO spacecraft to provide a complete view of the entire sky above the horizon. Each module is 50.8 cm (20 in.) in diameter, 1.27 cm (0.5 in.) thick, and operates in the energy range from 40 to 600 keV. Rough burst locations can be derived from the relative counting rates of the detectors; longer‐lived (≳ 100 min) transient sources can be detected and located by Earth occultations. The data system contains mass memory to allow storage of large amounts of burst data in short time intervals. Data are sorted onboard in various ways into programmable energy, time, and detector domains. Details of the design and capabilities of the BATSE are presented.

ISSN:0094-243X    

DOI:10.1063/1.34573

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The scattering of &ggr;‐rays (energy greater than 20 keV) from an astronomical point source in the earth’s atmosphere is simulated using Monte Carlo methods. The intensity of scattered &ggr;‐rays is estimated as a function of energy, direction, altitude, and geographic location. A few examples of the calculated flux are presented, averaging over direction to simulate the response of a BATSE detector to the scattered radiation.

ISSN:0094-243X    

DOI:10.1063/1.34574

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The Explosive Transient Camera (ETC) is a wide field (∼3 steradians) electronic camera array which can detect coincident optical flashes with durations of ∼10−1to 10+2seconds. It is anticipated (but not yet conclusively demonstrated) thatsimultaneousoptical flashes will be associated with certain classes of gamma ray bursts (GRBs). For the ETC, each array element is a 20°×30° FOV, cooled CCD detector, developed at MIT. An optical transient as faint asB=+11 (1 second duration) can be detected withS/N≥20, and its position determined to an accuracy of ±10 arc seconds. Thus, candidate events ∼103times fainter than the archived event (plate taken in 1928) reported for the 19 November 1978 gamma ray burst (GRB) by Schaefer (1981) should be detectable inreal time. In addition to detecting GRBs, the ETC is expected to catalog large numbers of flare stars, as well as potentially new classes of astronomical transients.The coordinates established by the ETC will be immediately transmitted (∼1 second delay) to the Rapidly Moving Telescope (RMT) under development at NASA/GSFC (Teegarden, Cline and von Rosenvinge 1983), which can further refine the position of a flash and follow its (presumed) subsequent decline. Communications to other rapid response radio or IR instruments will also be provided for, as well as time comparisons to gamma ray events detected by the International GRB Satellite Network (Hurley 1981).A prototype camera element was first tested in April 1982 to establish sky background levels and spurious event rejection schemes. A 1/2 steradian test version of the ETC is planned for operation in early 1984. Expansion to the full 3 steradian complement of 16 detectors at each of two sites is planned during the 1984‐1985 period. (Work supported in part by NASA under grants to MIT).

ISSN:0094-243X    

DOI:10.1063/1.34575

出版商:AIP    

年代:1984

数据来源: AIP