摘要:

Since the discovery of transient optical objects on archival photographic plates1inside or near the error boxes of &ggr;‐ray bursts (GRB) the question of possible optical counterparts of GRB has been continuously under debate. Using reflected light microscopy it is shown that two of the three objects are definite plate defects, and that there are serious doubts about the reality of the third one.

ISSN:0094-243X    

DOI:10.1063/1.42806

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

If a gamma‐ray burst (GRB) occurs in a neutral medium, ionizing radiation associated with the burst will flash‐photoionize a region surrounding the source. Detection of the line emission from this ionized region can constrain the flux of ionizing radiation accompanying the GRB and the density and ionization state of the environment surrounding the burst source. If the medium is sufficiently dense then the ionized region will recombine and fade on human timescales, aiding in the detection of the burst location and further constraining the density of the medium. However, dust within the dense medium may attenuate the line flux; the burst is unlikely to melt the dust along the line‐of‐sight. Astronomically interesting flux limits can be established by observations with reasonable integration times on a major telescope (e.g., 3 meter or larger).

ISSN:0094-243X    

DOI:10.1063/1.42841

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The Explosive Transient Camera (ETC), an automatic wide‐field sky monitor sensitive to short‐timescale optical transients, has been operating in conjunction with BATSE since the launch of GRO. In this paper, we discuss the probability and implications of the ETC monitoring a part of the sky in which BATSE detects a gamma‐ray burst.

ISSN:0094-243X    

DOI:10.1063/1.42807

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This paper describes the gamma‐ray burst detection capability of the gamma‐ray spectrometer on board the Mars Observer spacecraft. The instrument is designed to respond to significant bursts by suspending its observation of the martian surface in favor of optimizing the collection of pre‐burst, burst, and post‐burst data. The results are expected to contribute to our understanding of gamma‐ray bursts through a high‐energy resolution search for line emission, by the examination of spectral shapes and by comprising one leg of an arrival time network to determine the direction of origin.

ISSN:0094-243X    

DOI:10.1063/1.42808

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.42809

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The Burst and Transient Source Experiment (BATSE) has measured homogeneity and isotropy parameters from an increasingly large sample of observed gamma‐ray bursts (GRBs), while also maintaining a summary of the way in which the sky has been sampled. Measurement of both of these are necessary for any study of the BATSE data statistically, as they take into account the most serious observational selection effects known in the study of GRBs: beam‐smearing and inhomogeneous, anisotropic sky sampling. Knowledge of these effects is important to analysis of GRB angular and intensity distributions. In addition to determining that the bursts are local, it is hoped that analysis of such distributions will allow boundaries to be placed on the true GRB spatial and luminosity distributions is direct. The technique for studying GRB spatial and luminosity distributions is direct. Results of BATSE analyses are compared to Monte Carlo models parameterized by a variety of spatial and luminosity characteristics. Statistical analysis of model homogeneity and isotropy are made via the ⟨V/Vmax⟩ test, the log(N≳C) vs. log(C) test, multipole analysis, and two‐point angular correlation analysis. Comparisons of Monte Carlo test results to those of BATSE (all adjusted to account for selection effects) return confidence levels that given models explain BATSE observations.

ISSN:0094-243X    

DOI:10.1063/1.42810

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We recently discovered 217 ‘‘new’’ celestial gamma‐ray burst candidates from the ‘‘new’’ burst search of the PVO real time data base.1The burst search covered the time period from September 1978 to July 1988. Sixty were confirmed by at lest on other spacecraft, e.g., ISEE‐3, V‐11, V‐12, etc. None triggered the PVO high time resolution memory. In this paper we describe a new algorithm based ont eh relationship between time widthTwand hardness ratioHR, to distinguish cosmic gamma‐ray bursts from solar flares without knowing the directions of the events. The criteria for identification as a gamma‐ray burst candidate are: IfTww≤athenHR≥bTw, orTw≳athenHR≳c. Otherwise, the event is a solar flare candidate. Here,a,b, andcare parameter which differ for different gamma‐ray burst detectors. For PVO,a=18.8 s,b=(1.38/18.8) s−1, andc=1.38. This algorithm was tested with 83 triggered and 60 nontriggered confirmed gamma‐ray burst and 30 confirmed solar flares from PVO.

ISSN:0094-243X    

DOI:10.1063/1.42811

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The BATSE on‐board burst system has been triggered by over 400 terrestrial electron precipitation events. These are the single largest cause of false triggers. Bremsstrahlung is generated as the precipitating electrons interact in the Earth’s atmosphere, or in the spacecraft, and this radiation is detected by the Large Area Detectors, often triggering the instrument into burst model. Several examples of such events are presented here, and the different classes of events are described. A possible correlation of events to strong magnetospheric activity is presented, and the association of a sub‐set of events to a powerful VLF transmitter on the western coast of Australia is described.

ISSN:0094-243X    

DOI:10.1063/1.42765

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This is a continuation of work presented at the Second GRO Science Workshop.1It includes computations with much reduced timing errors as well as those for the PVO/Ulysses/GRO/GRANAT configuration. These could be done so quickly because the general coplanar problem of Taff’s2method is explicitly solvable. Given this, and the nearness of any actual spacecraft configuration to alignment with the ecliptic, both an initial guess and a rapidly converging numerical algorithm for the general situation can be formulated. Finally, since the timing errors dominate the observational errors, one can analytically compute the error distributions. Thus, Taff’s method is shown to be numerically robust, accurate, and analytically convenient.

ISSN:0094-243X    

DOI:10.1063/1.42766

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The Burst and Transient Source Experiment (BATSE) consists of eight anisotropic &ggr;‐ray spectrometers at the corners of the Compton Gamma Ray Observatory. BATSE monitors the full sky from a fixed orientation and determines the direction of &ggr;‐ray bursts with an accuracy appropriate for studying the bursts’ celestial distribution. We describe the calculation of &ggr;‐ray burst directions from measurements made by BATSE. We present a sample of calculated directions from BATSE’s measurement of solar flares and compare the calculated directions with the solar direction. We describe the systematic errors apparent in these data and discuss ongoing efforts to correct them.

ISSN:0094-243X    

DOI:10.1063/1.42839

出版商:AIP    

年代:1991

数据来源: AIP