摘要:

The observation of OTs connected to GRBs seems to have confirmed the cosmological hypothesis. However, a detailed knowledge of the source behavior in different spectral bands, with high time resolution and maximum possible bandwidth, before and during the GRB emission is necessary to understand the nature of these sources. In order to obtain this goal, the use of very large, wide fieldbadmirrors is proposed and justified. The dependence of detection limits from size, beam aperture, transparency, background level, time exposition, and detector quantum efficiency are considered for huge Cˇerenkov telescopes; the possibility of a contemporaneous observation in the optical band and in the VHE band with the same mirror, by using two different mirror/detector configurations, is suggested. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361636

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Four Soft Gamma Repeaters (SGRs) have now been identified with certainty, and a fifth has possibly been detected. I will review their X-ray and gamma-ray properties in both outburst and quiescence. The magnetar model accounts fairly well for the observations ofSGR1806−20andSGR1900+14,but data are still lacking forSGR1627−41andSGR0525−66.The locations of the SGRs with respect to their supernova remnants suggest that they are high-velocity objects. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361637

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The extraordinary giant flare of 1998 August 27 fromSGR&hthinsp;1900+14was the most intense event ever detected from this or any other cosmic source (even more intense than the famous 1979 March 5th event). It was longer than any previous burst fromSGR1900+14by more than one order of magnitude, and it displayed the same 5.16-s periodicity in hard X-rays that was detected in the low-energy X-ray flux of its quiescent counterpart. The event was detected by several gamma-ray experiments in space, among them theUlyssesgamma-ray burst detector and theBeppoSAXGamma Ray Burst Monitor. These instruments operate in different energy ranges, and a comparison of their data shows that the event emitted a strongly energy-dependent flux, and displayed strong spectral evolution during the outburst, itself. Here we present a joint analysis of theBeppoSAXandUlyssesdata, in order to identify the energy-dependent features of this event and understand some of the physical conditions in the environment of the neutron star which generated this flare. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361638

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We present evidence for burst emission fromSGR&hthinsp;1900+14with a power-law high-energy spectrum extending beyond 500 keV. Not only is the emission hard, but the spectra are better fit by Band’s GRB function rather than by the traditional optically-thin thermal bremsstrahlung model. We find that the spectral evolution within these hard events obeys a hardness/intensityanti-correlation. Temporally, these events are distinct from typical SGR burst emissions in that they are longer (∼1 s) and have relatively smooth profiles. Despite a difference in peak luminosity of≳1011between these bursts fromSGR&hthinsp;1900+14and cosmological GRBs, there are striking temporal and spectral similarities between the two kinds of bursts, aside from spectral evolution. We outline an interpretation of these events in the context of the magnetar model. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361639

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We have analyzedRXTEPCA observations of the pulsed emission fromSGR&hthinsp;1900+14during September 1996, June–October 1998, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 years. We find significant deviations from a steady spin-down trend during quiescence and the burst active interval. BATSE observations of the burst emission are presented and correlations between the burst activity and spin-down rate ofSGR&hthinsp;1900+14are discussed. We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor ∼2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or “braking glitch” at the time of the giant flare on 27 August 1998. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361640

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Deep searches for X-ray pulsations fromSGR&hthinsp;1627−41andSGR&hthinsp;0526−66were performed with ASCA.SGR&hthinsp;1806−20and1900+14were previously established as X-ray pulsars.SGR&hthinsp;0526−66is suspected to be a strong candidate for a magnetar, but X-ray pulsation has not been confirmed yet. Detection of X-ray pulsations fromSGR&hthinsp;1627−41andSGR&hthinsp;0526−66,is the key issue to the unified magnetar model of the SGRs. Although ASCA has done the deepest observations of ∼80 ks for both of them, we did not detect pulsations. The long-term period history ofSGR&hthinsp;1900+14is compared with a very similar change of the AXP pulsar1E1048.1−5937.©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361641

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

SGR bursts come from systems that accumulate a continuous energy input and release it as discrete bursts. This behavior is analogous to the tectonic systems that produce earthquakes. The fact that these systems can be detected by examining the relationship between burst times and fluences has additional implications, e.g., that burst emission is isotropic. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361642

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

BATSE detected 200 bursts fromSGR&hthinsp;1900+14between May 1998 and January 1999. The reactivation of the bursts initiated a series of RXTE observations within which more than 800 bursts were observed. Here we study statistical characteristics ofSGR&hthinsp;1900+14bursts using BATSE and RXTE observations. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361643

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

I-band imaging of the G337.0-0.1 region [1] limited by the IPN annulus reported by Hurley [2] were obtained on 25 June 1998, just 7.2-hr prior to a burst detected by Ulysses and Konus. A comparison image was obtained in late August 1998. No variable source was detected above a limiting magnitude ofI∼20.©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361644

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The primary mission of the Robotic Optical Transient Search Experiment (ROTSE) is to search for contemporaneous optical emission from GRBs. Among the triggers ROTSE receives via the GRB Coordinates Network (GCN), there are a number from Soft-Gamma Repeater (SGR) events. Since beginning operations in March 1998, ROTSE-I has triggered on 16 observable SGR events. Ten of these events had useful data, eight events fromSGR&hthinsp;1900+14and two events fromSGR&hthinsp;1806−20.The error regions for these SGRs are a small fraction of the ROTSE16°×16°field of view and have been searched for new or variable objects. Limits on optical transient counterparts are in the rangemROTSE≈12.5–15.5during the period 10 seconds to 1 hour after the observed SGR events. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361645

出版商:AIP    

年代:1900

数据来源: AIP