Narrow Results

We have recently proposed three paradigms for the theoretical interpretation of gamma-ray bursts (GRBs). (1) The relative space–time transformation (RSTT) paradigm emphasizes how the knowledge of the entire world-line of the source from the moment of gravitational collapse is a necessary condition in order to interpret GRB data.¹ (2) The interpretation of the burst structure (IBS) paradigm differentiates in all GRBs between an injector phase and a beam-target phase.² (3) The GRB-supernova time sequence (GSTS) paradigm introduces the concept of induced supernova explosion in the supernovae-GRB association.³ The RSTT and IBS paradigms are enunciated and illustrated using our theory based on the vacuum polarization process occurring around an electromagnetic black hole (EMBH) theory. The results are summarized using figures, diagrams and a complete table with the space–time grid, the fundamental parameters and the corresponding values of the Lorentz gamma factor for GRB 991216 used as a prototype. In the following sections the detailed treatment of the EMBH theory needed to understand the results of the three above paradigms is presented. We start from the considerations on the dyadosphere formation. We then review the basic hydrodynamic and rate equations, the equations leading to the relative space–time transformations as well as the adopted numerical integration techniques. We then illustrate the five fundamental eras of the EMBH theory: the self acceleration of the e⁺e^- pair-electromagnetic plasma (PEM pulse), its interaction with the baryonic remnant of the progenitor star, the further self acceleration of the e⁺e^- pair-electromagnetic radiation and baryon plasma (PEMB pulse). We then study the approach of the PEMB pulse to transparency, the emission of the proper GRB (P-GRB) and its relation to the "short GRBs". Particular attention is given to the free parameters of the theory and to the values of the thermodynamical quantities at transparency. Finally the three different regimes of the afterglow are described within the fully radiative and radial approximations: the ultrarelativistic, the relativistic and the nonrelativistic regimes. The best fit of the theory leads to an unequivocal identification of the "long GRBs" as extended emission occurring at the afterglow peak (E-APE). The relative intensities, the time separation and the hardness ratio of the P-GRB and the E-APE are used as distinctive observational test of the EMBH theory and the excellent agreement between our theoretical predictions and the observations are documented. The afterglow power-law indexes in the EMBH theory are compared and contrasted with the ones in the literature, and no beaming process is found for GRB 991216. Finally, some preliminary results relating the observed time variability of the E-APE to the inhomogeneities in the interstellar medium are presented, as well as some general considerations on the EMBH formation. The issue of the GSTS paradigm will be the object of a forthcoming publication while the relevance of the iron-lines observed in GRB 991216 is shortly reviewed. The general conclusions are then presented based on the three fundamental parameters of the EMBH theory: the dyadosphere energy, the baryonic mass of the remnant, the interstellar medium density. An in depth discussion and comparison of the EMBH theory with alternative theories is presented as well as indications of further developments beyond the radial approximation, which will be the subject of paper II in this series. Future needs for specific GRB observations are outlined.

We discuss the inhomogeneous behavior of gamma-ray burst afterglow light curves in optic. We use well-sampled light curves based on mostly our own observations to find and identify deviations (inhomogeneities) from broken power law. By the inhomogeneous behavior we mean flashes, bumps, slow deviations from power law (wiggles) in a light curve. In particular we report parameters of broken power law, describe phenomenology, compare optical light curves with X-ray ones and classify the inhomogeneities. We show that the duration of the inhomogeneities correlates with their peak time relative to gamma-ray burst (GRB) trigger and the correlation is the same for all types of inhomogeneities.

A new green emitting long-lasting phosphor Ca₂ZnSi₂O₇:Eu²⁺ has been synthesized through the high temperature solid-state method. The excitation spectrum of shows a broadband attributed to ⁸S_7/2–4f⁶5d¹ transition of Eu²⁺ ions. Both of the fluorescence and phosphorescence spectra showed a broadband centered at 528 nm, corresponding the only one Ca²⁺ site in Ca₂ZnSi₂O₇. The relationship of emission wavelength and Eu–O distance is investigated. Its afterglow can be seen with the naked eye in the dark clearly for 2 h after removal of the excitation source. Oxygen vacancy and zinc vacancy , two different kinds of traps are proposed and their contrary influence on afterglow is discussed.

The afterglow time of typical red-emitting phosphors is much shorter than those of green- or blue-emitting phosphors which afterglow time were longer than 1000 min. CaS has been used as an effective host material for afterglow phosphors because trapping centers can be easily created in the host by doping with an activator. This study reports on the effect of a reducing atmosphere on the afterglow properties of a red-emitting CaS:Eu²⁺,Pr³⁺ phosphor. The phosphor was prepared by reduction under an Ar-H₂ (5%) or H₂S atmosphere from a CaSO₄:Eu³⁺,Pr³⁺ phosphor prepared using a liquid phase method. Heating the CaSO₄:Eu³⁺,Pr³⁺ phosphor for 2 h under an Ar-H₂ (5%) atmosphere at 1050°C gave CaO as by-product in addition to CaS. The resulting phosphor exhibited red-emission at 646 nm originating from Eu²⁺ ions upon visible light irradiation, and gave some afterglow after cessation of visible light irradiation. Addition of Li⁺ ions extended the afterglow time of the phosphor as a result of a slight change in the CaS host structure. For preparation of a CaSO₄:Eu³⁺,Pr³⁺ phosphor under a H₂S atmosphere, a CaS monophase was obtained. The emission and afterglow of the phosphor were similar to that prepared under the Ar-H₂ (5%) atmosphere, but the afterglow time resulting from the CaS monophase was longer. The longest afterglow time obtained was about 60 min for a phosphor prepared under a H₂S atmosphere with an initial Li/Ca atomic ratio of 0.04.

Trap types of the yellow emitting long-persistent phosphor Ca₂BO₃Cl: ${\text{Eu}}^{2+}$, ${\text{Dy}}^{3+}$ were analyzed in this study. ${\text{Eu}}^{2+}$ acting as luminescent centers produced a broad emission band located at 580nm, which ascribes to the 5d-4f transitions. Four kinds of traps in this afterglow phosphor were detected by thermoluminescence spectra. Electron paramagnetic resonance spectroscopy, which is a considerable testing method, was used to identify the traps caused by different reasons. Based on it, detailed processes and traps analyses were examined and discussed.

Many short Gamma-Ray Bursts (sGRBs) have a prolonged plateau in the X-ray afterglow lasting up to tens of thousands of seconds. A central engine injecting energy into the remnant may fuel the plateau. A simple analytic model describing the interaction of the magnetized relativistic wind from a rapidly-rotating magnetar with the surrounding environment can reproduce X-ray plateaux and instantaneous spectra. The model is analogous to classic, well-established models of young supernova remnants and applies the underlying physics to sGRB remnants. The light curve and spectra produced by the model are compared to observations of GRB 130603B. The spectra are also used to estimate parameters of the magnetar including its poloidal field strength and angular frequency. If combined with a gravitational wave signal, this model could provide insight into multimessenger astronomy and neutron star physics.