Reverse Shock Emission as a Probe of GRB Ejecta

We calculate the reverse shock (RS) synchrotron emission in the optical and the radio wavelength bands from electron-positron pair enriched gamma-ray burst ejecta with the goal of determining the pair content of GRBs using early time observations. We take into account an extensive number of physical effects that influence radiation from the reverse-shock heated GRB ejecta. We find that optical/IR flux depends very weakly on the number of pairs in the ejecta, and there is no unique signature of ejecta pair enrichment if observations are confined to a single wavelength band. It may be possible to determine if the number of pairs per proton in the ejecta is > 100 by using observations in optical and radio bands; the ratio of flux in the optical and radio at the peak of each respective reverse-shock light curve is dependent on the number of pairs per proton. We also find that over a large parameter space, RS emission is expected to be very weak; GRB 990123 seems to have been an exceptional burst in that only a very small fraction of the parameter space produces optical flashes this bright. Also, it is often the case that the optical flux from the forward shock is brighter than the reverse shock flux at deceleration. This could be another possible reason for the paucity of prompt optical flashes with a rapidly declining light curve at early times as was seen in 990123 and 021211. Some of these results are a generalization of similar results reported in Nakar & Piran (2004).Comment: 12 pages, 6 figures, 2 tables, accepted to MNRA

A study of the reactions of third grade pupils to the various types of children's literature that were available during three specific periods: 1900-1920; 1920-1940; 1940-1953

Thesis (Ed.M.)--Boston Universit

Direct-write, focused ion beam-deposited,7 K superconducting C-Ga-O nanowire

We have fabricated C-Ga-O nanowires by gallium focused ion beam-induced deposition from the carbon-based precursor phenanthrene. The electrical conductivity of the nanowires is weakly temperature dependent below 300 K, and indicates a transition to a superconducting state below Tc = 7 K. We have measured the temperature dependence of the upper critical field Hc2(T), and estimate a zero temperature critical field of 8.8 T. The Tc of this material is approximately 40% higher than that of any other direct write nanowire, such as those based on C-W-Ga, expanding the possibility of fabricating direct-write nanostructures that superconduct above liquid helium temperaturesComment: Accepted for AP

COLA and Cartoons: A Showcase of Freshman Research At UNLV

ACKNOWLEDGEMENTS: Professor McMahon and the students of his COLA 100 section wish to acknowledge the kind support this project received from the following members of the Lied Library staff: Patricia Iannuzzi (Dean, University Libraries) Vicki A. Nozero (Director, User Services) Dan Werra (Media and Computer Services) Priscilla Finley (Humanities Librarian