Jonathan I. Katz, Professor
[my last name]@wuphys.wustl.edu
Professor Katz's work centers on gamma-ray bursts, the most energetic explosions in the universe. These events appear to release as much energy as is contained in 1% of the rest mass of the Sun and produce streams of matter moving outward at between 99.99% and 99.9999% of the speed of light. Investigating the shocks which result when this fast and energetic stream collides with surrounding matter, or with other streams, Professor Katz was able to predict the low frequency asymptotic spectrum of the emitted radiation and the occurrence of radio and visible "afterglows" to gamma-ray bursts. The predicted spectrum has a spectral density proportional to the 1/3 power of the frequency, a result familiar from laboratory synchrotrons but never before seen in astronomical objects. It was predicted in gamma-ray bursts because of the unprecedented particle distribution function found in relativistic shocks and has since been observed at frequencies ranging from millimeter waves to soft gamma rays.
In the early stages of a gamma-ray burst afterglow the radiating region is small, and it was possible to predict that the radio-frequency radiation would be self-absorbed. This prediction was verified empirically, confirming the basic theory of gamma-ray bursts and their afterglows. More detailed studies of this self-absorbed radiation may make it possible to follow the expansion of a gamma-ray burst "fireball" in detail and to compare this expansion to theoretical predictions.
Several important questions about gamma-ray bursts remain unresolved. For example, there is evidence that their radiation is strongly beamed. This is permitted by their relativistic expansion. Strong beaming would imply that the total energy released is less than might otherwise be inferred. Because beaming will vary with time in an afterglow and with frequency of observation, it may explain the observation that some strong bursts have weak afterglows, and some comparatively weak bursts have stronger afterglows.
Prof. Katz also works on a number of diverse topics in applied physics, biophysics and materials science. Consult his complete publication list for details.
Selected Publications on Gamma-Ray Bursts:
"Two Models and Populations of Gamma-Ray Bursts," J. I. Katz, Astrophysical Journal 422, 248 (1994)
"Delayed Hard Photons from Gamma-Ray Bursts," J. I. Katz, Astrophysical Journal (Lett.) 432, L27 (1994)
"Low Frequency Spectra of Gamma-Ray Bursts," J. I. Katz, Astrophysical Journal (Lett.) 432, L107 (1994)
"Yet Another Model of Gamma-Ray Bursts," J. I. Katz, Astrophysical Journal 490, 633 (1997)
"Persistent Counterparts to GRB." J. I. Katz and T. Piran, Astrophysical Journal 490, 772 (1997)
"Implications of the Visible and X-Ray Counterparts to GRB970228," J. I. Katz, T. Piran and R. Sari, Physical Review Letters 80, 1580 (1998)
"The Biggest Bangs," J. I. Katz, Oxford U. Press (2002); this popular book is now available. To see excerpts (the Table of Contents and a sample chapter) click on your preferred format: postscript pdf.
High Energy Astrophysics (Addison-Wesley, 1987)
Other items of possible interest: (These represent my personal views alone. Washington University would never take an official position which might deviate from the ``politically correct'' line. I don't know how they find out what the line is each day, but they sure keep up-to-date.)
Washington University Press Policy
Limiting the Nuclear Club---Iraq, North Korea, et al. 1994 article published in Strategic Review advocating pre-emptive strike against North Korea's nuclear weapons project
Anyone Who Bombs Baghdad [when Saddam was in power] Gets My Vote
Diversity is the Last Refuge of a Scoundrel
What's New at Washington University
Earthquake-safe Housing for Iran and Elsewhere
A Student's View of Washington University
What is Political Correctness?
Deception and Denial in Iraq and the Intelligent Adversary Corollary
Hurricane Mitigation with Surfactants