Specifying the Environments around GRB, Explaining the Fe line in the X-Ray Afterglow of GRB000214

We present a model explaining the Fe K alpha line and the continuum in the afterglow of GRB000214. We pose the importance to seek the physically natural environment around GRB000214. For the reproduction of the observation, we need the ring-like remnant around the progenitor like that of SN 1987A produced by the mass-loss of the progenitor and the fireball spread over in every directions. The observation of GRB000214, in which the continuum power law spectrum decreased faster than the line, motivated us to consider the two independent systems for the line emission and the continuum spectrum. At first, the continuum spectrum can be fitted by the afterglow emission of the fireball pointing toward the observer which does not collide with the ring because the emission of GRB and the afterglow are highly collimated to the observer by the relativistic beaming effect. Secondly, the line can be fitted by the fluorescence of the Fe atoms in the ring illuminated by the X-ray afterglow. The significance of this study is that our model may constrain strongly the GRB model. Although the Supranova model assumes the extreme-ring-like remnant produced by the usual supernova explosion, this may not be probable. It is because the supernova remnants are known to be shell-like. The model also assumes two steps of explosions, on the other hand, we need only one explosion of the progenitor. In this sense, our scenario is more natural. Moreover, in the numerical simulations of Hypernova, the jet of the opening angle of only 1 degree is generated. In our model, the fireball which spreads over in every directions reconciles with the observation of 1 percent of the polarization in the observation of SN1998bw which showed the explosion might not be so collimated.Comment: 26 pages and 2 postscript figures. to appear in Publications of the Astronomical Society of Japan. In this revision, we added some discussions and changed several English expresson

Chemical Evolution in the Large Magellanic Cloud

We present a new input parameter set of the Pagel model (Pagel & Tautvai$\rm \breve{s}$ien$\rm \dot{e}$ 1998) for the Large Magellanic Cloud (LMC) in order to reproduce the observations, including the star formation rate (SFR) history. It is concluded that the probability for (3-8)$M_{\odot}$ stars to explode as SNe Ia has to be quite high ($\sim 0.17$) in the LMC. As a result, a steep initial mass function (IMF) slope and existence of the outflow are not needed in order to attain the low [O/Fe] ratio in the LMC. As for the current supernova ratio, a high ratio ($\sim 1.3$) is concluded by the new parameter set, which is consistent with the recent X-ray observations.Comment: 20 pages, gzipped tar file including LaTeX text and 8 postscript figures. submitted to Publication of the Astronomical Society of Japa

Pulsar Kick and Asymmetric Iron Velocity Distribution in SN 1987A

We have investigated the relation of the direction of the momentum among the matter, neutrino, and proto-neutron star in a collapse-driven supernova in order to discuss the pulsar kick. In particular, we have investigated the effects of the pulsar motion on the explosion, which are neglected in the previous study. As a result, it is suggested that the direction of the total momentum of the matter and neutrino is opposite to that of the momentum of the proto-neutron star in the asymmetric explosion models. This is because the center of the explosion deviates from the center of the progenitor due to the pulsar motion. This picture is common among the asymmetric explosion models. So if we assume that the pulsar motion is caused by an asymmetric supernova explosion, the neutron star born in SN 1987A, which has not been found yet, will be moving in the southern part of the remnant. In other words, if we can find one neutron star in SN 1987A on the south part of the remnant, asymmetric explosion models will be supported by the observation better than the binary models.Comment: 10 pages and 4 postscript figure

Very High Energy Neutrinos Originating from Kaons in Gamma-Ray Bursts

We simulate neutrino production in a gamma-ray burst (GRB) with the most detailed method to date. We show that the highest energy neutrinos from GRBs mainly come from kaons. Although there is little chance to detect such neutrinos, attempts of detection are very important to prove physical conditions in GRBs.Comment: 4 figures. Accepted for publication in ApJ

Anisotropic e+e−e^+ e^- pressure due to the QED effect in strong magnetic fields and the application to the entropy production in neutrino-driven wind

We study the equation of state of electron in strong magnetic fields which are greater than the critical value $B_c \simeq 4.4 \times 10^{13}$ Gauss. We find that such a strong magnetic field induces the anisotropic pressure of electron. We apply the result to the neutrino-driven wind in core-collapse supernovae and find that it can produce large entropy per baryon, $S \sim 400 k_B$. This mechanism might successfully account for the production of the heavy nuclei with mass numbers A = 80 -- 250 through the r-process nucleosynthesis.Comment: 4 pages, using REVTeX and 3 postscript figure

Rapid-Process Nucleosynthesis in Neutrino-Magneto-Centrifugally Driven Winds

We have studied whether the rotation and magnetic fields in neutrino-driven winds can be key processes for the rapid-process (r-process) nucleosynthesis. We have examined the features of a steady and subsonic wind solutions which extend the model of Weber and Davis (1967), which is a representative solar wind model. As a result, we found that the entropy per baryon becomes lower and the dynamical timescale becomes longer as the angular velocity becomes higher. These results are inappropriate for the production of the r-process nuclei. As for the effects of magnetic fields, we found that a solution as a steady wind from the surface of the proto-neutron star can not be obtained when the strength of the magnetic field becomes $\ge$ $10^{11}$ G. Since the magnetic field in normal pulsars is of order $10^{12}$ G, a steady wind solution might not be realized there, which means that the models in this study may not be adopted for normal proto-neutron stars. In this situation, we have little choice but to conclude that it is difficult to realize a successful r-process nucleosynthesis in the wind models in this framework.Comment: 20 pages and 4 postscript figures. submitted to Publications of the Astronomical Society of Japa

Initial Shock Waves for Explosive Nucleosynthesis in Type II Supernova

We have performed 1-dimensional calculations for explosive nucleosynthesis in collapse-driven supernova and investigated its sensitivity to the initial form of the shock wave. We have found the tendency that the peak temperature becomes higher around the mass cut if the input energy is injected more in the form of kinetic energy rather than internal energy. Then, the mass cut becomes larger, and, as a result, neutron-rich matter is less included in the ejecta; this is favorable for producing the observational data compared with a previous model. Our results imply that the standard method to treat various processes for stellar evolution, such as convection and electron capture during the silicon burning stage, are still compatible with the calculation of explosive nucleosynthesis.Comment: 20 pages, 6 figures, LaTe

High Energy neutrino signals from the Epoch of Reionization

We perform a new estimate of the high energy neutrinos expected from GRBs associated with the first generation of stars in light of new models and constraints on the epoch of reionization and a more detailed evaluation of the neutrino emission yields. We also compare the diffuse high energy neutrino background from Population III stars with the one from "ordinary stars" (Population II), as estimated consistently within the same cosmological and astrophysical assumptions. In disagreement with previous literature, we find that high energy neutrinos from Population III stars will not be observable with current or near future neutrino telescopes, falling below both IceCube sensitivity and atmospheric neutrino background under the most extreme assumptions for the GRB rate. This rules them out as a viable diagnostic tool for these still elusive metal-free stars.Comment: 9 pages, 5 figures