Environment of The Gamma-Ray Burst GRB971214 : A Giant H II Region surrounded by A Galactic Supershell

Among a number of gamma ray bursts whose host galaxies are known, GRB971214 stands out for its high redshift $z\ge 3$ and the Ly$\alpha$ emission line having a P-Cygni type profile, which is interpreted to be a direct consequence of the expanding supershell. From a profile fitting analysis we estimate the expansion velocity of the supershell v_{exp} = 1500\kms and the neutral column density N_{HI}=10^{20}\cm^{-2}. The redshift $z=3.418$ of the host galaxy proposed by Kulkarni et al. (1998) has been revised to be $z=3.425$ from our profile analysis. The observed Ly$\alpha$ profile is fitted well by a Gaussian curve, which yields the Ly$\alpha$ luminosity L_{Ly\alpha}=(1.8\pm0.8)\times10^{42}\ergs \s^{-1}. Assuming that the photon source is a giant H II region, we deduce the electron number density in the H II region n_e=(40\pm10) ({R \over {100 \pc}})^{-1.5}\cm^{-3}, which corresponds to the illumination by about $10^4$ O5 stars. We estimate the star-formation rate to be R_{SF} = (7\pm3){\rm M}_\odot\yr^{-1} with the internal and the Galactic extinction corrected. The theory on the evolution of supernova remnants is used to propose that the supershell is at the adiabatic phase, with its radius R = 18 E_{53}^{1/2} \pc, its age $t = 4.7\times10^3\ E_{53}^{1/2} \yrs$, and the density of the ambient medium$n_1 = 5.4\ E_{53}^{-1/2}\cm^{-3}$, where$E_{53}= E/10^{53}\ergs$.And we estimate the kinetic energy of the supershell to be$E_k=7.3\times10^{52} E_{53} \ergs$. These values are consistent with the hypothesis that the supershell is the remnant of a gamma ray burst.Comment: 5 papges, 3 figures, Accepted for publication in Astrophysical Journal Letter

Human Capital Spending, Inequality, and Growth in Middle-Income Asia

Asia’s rapid population aging fortifies the case for strengthening human capital investments. Further, the experience of the newly industrialized economies suggests that human capital investments will be a vital ingredient of the transition from middle income to high income. Those investments can also affect equity and public finances. In this paper, we use data from the National Transfer Accounts to empirically analyze the effect of human capital investment in Asian countries on economic growth, inequality, and fiscal balance. Our empirical evidence suggests that human capital investments have a positive effect on labor productivity and, hence, output. The positive effect is stronger for poorer households and, hence, beneficial for equity. We also find that such investments can generate sufficient tax revenues to improve the fiscal balance. Overall, our evidence points to a positive effect of human capital on growth, equity, and fiscal balance in Asia

Multi-beam range imager for autonomous operations

For space operations from the Space Station Freedom the real time range imager will be very valuable in terms of refuelling, docking as well as space exploration operations. For these applications as well as many other robotics and remote ranging applications, a small potable, power efficient, robust range imager capable of a few tens of km ranging with 10 cm accuracy is needed. The system developed is based on a well known pseudo-random modulation technique applied to a laser transmitter combined with a novel range resolution enhancement technique. In this technique, the transmitter is modulated by a relatively low frequency of an order of a few MHz to enhance the signal to noise ratio and to ease the stringent systems engineering requirements while accomplishing a very high resolution. The desired resolution cannot easily be attained by other conventional approaches. The engineering model of the system is being designed to obtain better than 10 cm range accuracy simply by implementing a high precision clock circuit. In this paper we present the principle of the pseudo-random noise (PN) lidar system and the results of the proof of experiment