摘要:

Some calculations relevant to &ggr;‐ray astronomy, carried out by the author and his collaborators, are reported: limits on the amounts of57Ni and44Ti in SN1987A and other similar Type II explosions; nucleosynthesis of26Al in massive stars and supernovae; the delayed denotation model for Type Ia supernovae and60Fe synthesis; explosion dynamics of Type Ib supernovae; and &ggr;‐ray bursts from collapsing bare white dwarfs. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.40944

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Data from the high‐resolution gamma‐ray spectroscopy experiment on HEAO 3 have been searched for line emission from the decay of44Ti created in recent galactic supernova explosions. Because the 78‐year mean life of44Ti is comparable to the average time between galactic supernovae, the gamma‐ray line emission from its decay should appear as a galactic point source. No evidence was found for such emission from a point source anywhere in the galactic plane, with a 1 &sgr; limit of 8.3×10−5photons cm−2s−1. A detailed model was developed to simulate the galactic gamma‐ray emission from the decay of44Ti produced in type I supernovae. This model was used with the measured gamma‐ray line limits to constrain the supernova yields and recurrence periods. For example, if the supernovae recurrence period is 36 years, the average44Ti yield per event must be <4×10−4M⊙at the 90% level of confidence.

ISSN:0094-243X    

DOI:10.1063/1.40945

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.40946

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The situation concerning the presence of features in gamma ray burst (GRB) spectra is analyzed taking into account recent results obtained especially with the PHOBOS probes and GINGA satellite. If the existence of cyclotron features seems now to be generally accepted the situation for the other features reported around 400‐500 keV is not completely clarified. The presence of such features is discussed. Moreover some aspects of the high and low energy variations in the GRB and on the characteristics of their total spectrum are also reviewed. Finally future missions which might have a great impact in the GRB spectral analysis will be shortly considered.

ISSN:0094-243X    

DOI:10.1063/1.40948

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

During the third flight of the FIGARO II experiment on July 9th 1990 the Crab pulsar PSR0531+21 has been kept in the axis of the telescope during 7.5 hours.On line analysis showed the pulsar light curve with only 5 minutes of data acquisition time.The complete analysis of the observation will probably help to search for gamma ray line in the pulsed part of the spectrum.Particularly a line around 450 keV has been previously detected by some experiments but at low statistical level and attributed ambiguously to the Nebula.

ISSN:0094-243X    

DOI:10.1063/1.40949

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We review the observations of transient &ggr;‐ray line and sporadic continuum emissions from the Crab over the last two decades and use these measurements to explore the emission mechanisms and regions. When examined in detail, the measurements require and emission region(s) considerably more complex than predicted by simple synchrotron models, suggesting behavior reminiscent of gamma‐ray bursts.

ISSN:0094-243X    

DOI:10.1063/1.40902

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The massive binary X‐ray source 4U 1700‐377 was observed three times in 1990 by the SIGMA telescope in the energy range 35 keV to 1.3 MeV. The source, which was detected up to 170 keV, exhibits a strong flaring activity, reaching the luminosity of the Crab Nebula in the 40‐77 keV energy band during nearly 20 min on September 12. Its spectrum has been found to be of thermal Bremsstrahlung type with a temperature kT≊50 keV.

ISSN:0094-243X    

DOI:10.1063/1.40903

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The region of the sky containing the high energy gamma‐ray source 2CG 135+01 was observed by SIGMA on 1990, July 28–30th. The images obtained were searched for positive emission from the known candidate counterparts. No significant excess was detected. Upper limits in the hard X‐ray range are presented and discussed in the light of the present observational status.

ISSN:0094-243X    

DOI:10.1063/1.40904

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The black‐hole candidate Cyg X‐1 has been one of the first targets of the SIGMA &ggr;‐ray telescope on board the Soviet GRANAT spacecraft. SIGMA, an imaging telescope based on the coded mask principle, operates in the 35 keV‐1.3 MeV energy range and, when used in ‘‘fast variability’’ mode, has a time resolution of one millisecond. We present here the preliminary results of a ‘‘fast variability’’ observation of Cyg X‐1 performed in March 1990.

ISSN:0094-243X    

DOI:10.1063/1.40905

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Observations with theSpacelab‐2and TTM coded mask telescope instruments identify GRS1758‐258 with a peak source detected in theExosatLE and hence lead to a very well defined position.

ISSN:0094-243X    

DOI:10.1063/1.40906

出版商:AIP    

年代:1991

数据来源: AIP