Doctoral Dissertation Defense - Gopal Bhatta

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Venue:CP 220

UNIVERSITY GRADUATE SCHOOL BULLETIN ANNOUNCEMENT

Florida International University University Graduate School

Doctoral Dissertation Defense

Abstract

The Nature of Microvariability in Blazar 0716+714

by

Gopal P. Bhatta

We organized an international campaign to observe the blazar 0716+714 in the optical. The observations took place from February 24, 2009 to February 26, 2009. The global campaign was carried out by observers from more that sixteen countries and resulted in an extended light curve nearly seventy-eight hours long. The analysis and the modeling of this light curve form the main work of this dissertation project. In the first part of this work, we present the time series and noise analyses of the data. The time series analysis utilizes discrete Fourier transform and wavelet analysis routines to search for periods in the light curve. We then present results of the noise analysis which is based on the idea that each microvariability curve is the realization of the same underlying stochastic noise processes in the blazar jet. Neither reoccuring periods nor random noise can successfully explain the observed optical fluctuations. Hence in the second part, we propose and develop a new model to account for the microvarability we see in blazar 0716+714. We propose that the microvariability is due to the emission from turbulent regions in the jet that are energized by the passage of relativistic shocks. Emission from each turbulent cell forms a pulse of emission, and when convolved with other pulses, yields the observed light curve. We use the model to obtain estimates of the physical parameters of the emission regions in the jet. The study showed that the distribution of the sizes of the turbulent region in the jet centers within 60 AU. This puts a constraint on magneto-hydrodynamical models of blazar jet. Besides, it supports our initial assumption that shock wave encountering a laminar flow of relativistic plasma may not produce microvariability.

Date: November 07, 2012 Department: Physics Time: 09.00 a.m. Major Professor: James R Webb Place: Modesto Maidique Campus, CP 220