University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Spring 1986 ON THE SPECTRA OF GAMMA-RAY BURSTS AT HIGH ENERGIES STEVEN MICHAEL MATZ University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation MATZ, STEVEN MICHAEL, "ON THE SPECTRA OF GAMMA-RAY BURSTS AT HIGH ENERGIES" (1986). Doctoral Dissertations. 1483. https://scholars.unh.edu/dissertation/1483 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a manuscript sent to us for publication and microfilming. 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Zeeb Road, Ann Arbor, Ml 48106 Copyright 1986 by Matz, Steven Michael All Rights Reserved ON THE SPECTRA OF GAMMA-RAY BURSTS AT HIGH ENERGIES BY STEVEN MICHAEL MATZ AB, University of Chicago, 1979 A DISSERTATION Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Physics May 1986 This dissertation has been examined and approved. Edward L. Chupp Professor of Physics Roger L. Arnoldy Professor of Physics John F. Dawson rofessor of Physics QjUh.. Robert E. Houston, Jr. Professor of Physics Lyman slower Professor of Physics ALL RIGHTS RESERVED © 1986 Steven Michael Matz To my parents ACKNOWLEDGEMENTS I would like to express my thanks to my advisor, E. L. Chupp, for his support, especially in giving me access to the rich GRS data set and in allowing me to pursue my research with a great deal of independence. I also gratefully acknowledge my debt to Dave Forrest for much instruction in how to do real physics and for insight into the working of the instrument. I am also grateful to Tom Vestrand for useful discussions and seminal suggestions. I also thank Sherry Palmer for fast and professional drafting of the figures. This dissertation was printed by T^jX on a QMS Lasergrafix800, courtesy of Prof. John Dawson and the Nuclear Physics Group at the University of New Hampshire. Finally, I thank the taxpayers of the United States, who supported this work under NASA contracts NAS5-23761 and NAS5-28609, and NASA research grant NGL30-002-021. v TABLE OF CONTENTS DEDICATION ..................................................................................................................... iv ACKNOWLEGDEMENTS .............................................................................................. v LIST OF TABLES ..............................................................................................................ix LIST OF FIGURES .......................................................................................................... x ABSTRACT ..................................................................................................................... xv INTRODUCTION ............................................................................................................. 1 Characteristics of the Source Object ..................................................................... 3 Burst Timescales and Source Size ................................................................. 3 Surface Gravity.....................................................................................................4 Magnetic Field .................................................................................................. 6 Source Luminosity at Other Wavelengths...................................................... 7 Where Are They? .................................................................................................... 10 Statistical Treatment ..................................................................................... 10 Individual Source Locations.......................................................................... 12 Summary of Conclusions................................................................................ 14 Theories of GammarRay Bursts .......................................................................... 15 Energy Production and Release................................................................... 15 Radiation Mechanisms................................................................................... 17 Summary .................................................................................................................... 18 I. SMM/GRS GAMMA-RAY BURSTS ..................................................................... 20 The SMM Gamma-Ray Spectrometer................................................................... 20 Gain Stabilization System ............................................................................ 22 The GRS as a Gamma-Ray Burst Detector ............................................. 25 Gamma-Ray Bursts in the GRS Data S et............................................................ 26 Detection of Events............................................................................................26 Identification of Gamma-Ray Bursts .......................................................... 28 GRS Bursts and the Class of Classical Gamma-Ray Bursts ................. 33 H. HIGH-ENERGY EMISSION IN GAMMA-RAY BURSTS .............................. 36 Presence of High-Energy Emission in Bursts.................................................... 37 D ata ................................................................................................................... 37 Instrument Sensitivity and Detectability .................................................. 41 A nalysis................................................................................................................ 42 Discussion and Conclusions .......................................................................... 47 Energetic Importance of > 1 MeV Emission.................................................... 49 Fraction of Total Burst Energy in > 1 MeV Photons............................ 49 Conclusions ...................................................................................................... 52 m . HIGH-ENERGY EMISSION AND SPECTRAL MODELS .......................... 53 Review of Spectral Models of Gamma-Ray Bursts ......................................... 54 Fitted Spectral Parameters, 0.3-9 M eV ................................................................60 Average Fitted Parameters .......................................................................... 60 Comparisons for Individual Events ............................................................. 65 Acceptability of M odels....................................................................................66 Tests of Models at High Energies ......................................................................... 73 Discussion and Conclusions............................... 76 Effects of Spectral Evolution......................................................................... 76 Conclusions ...................................................................................................... 79 vii IV. MAGNETIC FIELD, PAIR PRODUCTION, AND BEAMING ................... 82 Previous Estimates of the Magnetic Field Strength ....................................... 83 Confinement of High-Temperature Plasma ............................................... 85 Low-Energy Spectral Features ..................................................................... 85 Conclusions ...................................................................................................... 89 Single-Photon Pair Production