The γ-ray burst phenomenon treated as the collapse of a QED magnetized vacuum bubble: analogy with sonoluminescence

We treat the phenomenon of a γ -ray burst as the non-linear collapse of a magnetic cavity surrounding a neutron star with extremely large magnetic field B ∼10¹⁵–10¹⁶ G due to the process of bubble shape instability in the resonant MHD field of an accreting plasma or on a neutron star surface. The QED effect of vacuum polarizability by a strong magnetic field is taken into a consideration. We develop an analogy with the phenomenon of sonoluminescence in which the gas bubble is located in a surrounding liquid with a driven sound intensity.     

Status of the ROTSE‐III telescope network

ROTSE‐III is a homogeneous worldwide array of 4 robotic telescopes. They were designed to provide optical observations of γ ‐ray burst (GRB) afterglows as close as possible to the start of γ ‐ray emission. ROTSE‐III is fulfilling its potential for GRB science, and provides optical observations for a variety of astrophysical sources in the interim between GRB events. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

2.6--3.8 GHz太阳微波爆发中的精细结构

根据1994年lslike＆Benz给出的1－3GHz频带上的微波III型爆发和微波尖峰辐射的分类定义,分析北京天文台26－3．8GHz频带上观测到的微波爆发的精细结构．通过分析发现该定义有局限性．本文重新定义了该波段上的微波III型爆发和微波尖峰辐射,并讨论了这种分类定义与设备时间分辨率的关系     

Dense star clusters as the sources of gamma-ray-burst progenitors

Two independent sets of arguments lead us to conclude that the progenitors of superintense bursts (with an energy yield larger than that for ordinary supernovae by one or two orders of magnitude) are born in massive dense star clusters, but generally flare up only after they have left the cluster; these are the same objects that are the progenitors of gamma-ray bursts (GRBs). Each of the giant stellar arcs which are grouped into multiple systems of stellar complexes in the LMC and NGC 6946 could only be produced by a single powerful energy release near its center. The progenitors of these systems of arc-shaped stellar complexes must have had a common source nearby, and it could only be a massive star cluster. Such clusters are actually known near both systems. On the other hand, calculations of the dynamical evolution of star clusters show that close binary systems of compact objects are formed in the dense central parts of the clusters and are then ejected from them during triple encounters. Mergers of the components of such systems are believed to be responsible for GRBs. Since their progenitors are ejected from the cluster before merging, the arc-shaped stellar complexes produced by GRBs are observed near (but not around) the parent clusters. If a considerable fraction of the GRB progenitors are formed as a result star encounters in massive star clusters, and if the GRBs themselves trigger star formation near the parent clusters, then observations of GRBs in star-forming regions are consistent with their origin during mergers of pairs of compact objects.     

Discovery of an optical flare from GRB 060926 by the MASTER robotic telescope: Possible formation of a marginally rotating black hole

The MASTER robotic telescope has obtained the first optical images of GRB 060926. We have discovered an optical flare from GRB 060926, a recurrent brightening that closely follows its behavior in the X-ray range. We have determined the spectral slope for GRB 060926 from the X-ray to optical range in the first minutes. Based on the spinar model, we show that the parameters of the optical and X-ray flares suggest that the gamma-ray burst resulted from the core collapse of a 7M _⊙ star with an initial effective Kerr parameter of 7.6 and an initial magnetic-to-gravitational energy ratio of 10^?4.     

Discovery of an optical afterglow from the cosmic GRB 920925C

A systematic study of the archival images for the error boxes of cosmic gamma-ray bursts (GRBs) obtained at the Palomar (USA) and Siding Spring (Australia) Observatories during the DSS allsky survey has revealed an optical transient with a magnitude of 17.8 within the error circle of the bright event GRB 920925C on the plate taken 6 h after the burst. The position of the object falls within the IPN error box for the burst. Analysis of the event properties suggests that the detected transient is most likely the optical afterglow from GRB 920925C. This event occurred 4.5 yr before GRB 970228, which has been considered to be the first optically identified GRB up until now.     

Unusual stripes in emission and absorption in solar radio bursts: Ropes of fibers in the meter wave band

Based on data from the spectrographs of IZMIRAN and Tremsdorf station (Astronomical Institute, Potsdam), we analyze the ropes of narrow-band fibers in the spectra of solar radio bursts in the meter wave band by invoking events of satellite data (SOHO/LASCO, EIT, MDI) for the analysis. We consider in detail basic properties of the ropes in four events in comparison with previously known data. The fibers in ropes are more commonly observed with an overlap in time and frequency, but occasionally (more often at the end of the ropes) they can follow with a separation in time. The fiber duration and recurrence period seldom remain stable and, in general, increase from 0.3–0.5 s at the beginning to several seconds at the end of the rope. The relative values of the instantaneous and total fiber frequency bandwidths change only slightly in different events; δ f / f ≈ 0.003–0.005 and Δf / f ≈ 0.02–0.03. Most of the ropes exhibit a low-frequency absorption. The fibers in ropes are similar to ordinary intermediate drift bursts (fiber bursts), but they drift in a narrow frequency band and have a more frequent recurrence in some events. The ropes of fibers are usually observed in the time interval when the shock front catches up with the leading edge of a coronal mass ejection. Under the condition of a unified approach to interpreting the ropes of fibers in all events, their basic properties can be explained in terms of the model of fiber bursts. The connection of fibers with the developed zebra pattern is shown within the framework of a unified approach to the formation theory of stripes in emission and absorption in the model on whistlers.     

恒星初始质量分布函数对伽玛暴爆发率的影响

伽玛射线暴的产生机制比较公认的是:长暴产生于大质量恒星死亡;短暴产生于密近双星合并.因此人们很自然地推测长暴和恒星形成率直接成比例,但是最近数据分析表明这并不能很好地拟合观测.考虑到只有质量大于某一临界质量的大质量恒星才可能产生长暴,因此恒星初始质量分布函数对长暴的产生率会有较大影响.考虑用恒星初始质量分布函数来解释长暴观测个数随红移的分布,得到了比较好的结果.     

United classification of cosmic gamma-ray bursts and their counterparts

This paper establishes united classification of gamma-ray bursts and their counterparts on the basis of measured characteristics: photon energy E and emission duration T. We find that the interrelation between these characteristics is such that as the energy increases, the duration decreases (and vice versa). The given interrelation reflects the nature of the phenomenon and forms the E–T diagram, which represents a natural classification of all observed events in the energy range from about 10⁹ to 10⁻⁶ eV and in the corresponding interval of durations from about 10⁻² up to 10⁸ s. The proposed classification results from our findings, which are principal for the theory and practical study of the phenomenon.     

Energetics–spectral correlations versus the BATSE gamma-ray bursts population

The proposed correlations between the energetics of gamma-ray bursts (GRBs) and their spectral properties, namely the peak energy of their prompt emission, can broadly account for the observed fluence distribution of all 'bright' BATSE GRBs, under the hypothesis that the GRB rate is proportional to the star formation rate and that the observed distribution in peak energy is independent of redshift. The correlations can also be broadly consistent with the properties of the whole BATSE long GRB population for a peak energy distribution smoothly extending towards lower energies, and in agreement with the properties of a sample at 'intermediate' fluences and with the luminosity functions inferred from the GRB number counts. We discuss the constraints that this analysis imposes on the shape of such peak energy distribution, the opening angle distribution and the tightness of the proposed correlations.