Download description - Универзитет у Београду

TO THE COUNCIL FOR THE STUDIES WITHIN THE UNIVERSITY OF
BELGRADE (ВЕЋУ ЗА СТУДИЈЕ ПРИ УНИВЕРЗИТЕТУ У БЕОГРАДУ)
Studentski trg 1
Beograd
By a decision of the Council for studies within the University of Belgrade on 30. May
2012., an exaination committee is formed for public defend of master thesis entitled
“Physical Parameters of the Relativistic Shock Waves in a Sample of Gamma Ray
Bursts”, candidate Luca Grasitelli, bechelor of physics. The committee has the following
members:
- Prof. Dr Dejan Urošević, Faculty of Mathematics, University of Belgrade
- Prof. Dr Luka Č. Popović, Faculty of Mathematics, University in Belgrade
- Assistant prof. Dr Bojan Arbutina, Faculty of Mathematics, University in Belgrade
- Dr Saša Simić, Researcher, Faculty of science, University of Kragujevac
After detailed review of the master thesis, the Committee submits to the Council for
studies within the University of Belgrade the following
REPORT
on the master thesis evaluation
BASIC BIOGRAPHICAL DATA OF THE CANDIDATE
Luca Grasitteli is born on 15.05.1987. in Terlizzi (Italy), where he finished Scientific
High School Degree from Liceo Scientifico Orazio Tedone-Ruvo di Puglia (Italy) in 2006.
He got his bachelor degree at the University of Bari (Italy) Università degli Studi di Bari in
2010, successfully defending his thesis titled “Einstein, Podolsky, Rosen Paradox”.
In September 2010. he starts attending the course in Astrophysics in the frame of the
Erasmus Mundus Master Program in Astrophysics “Astromundus”. First semester he spent at
the University of Innsbruck (Austria), the second semester at the University of Padova, third
at the University of Goetingen (Germany) and the forth semester he spent the University of
Belgrade working on the master thesis research.
1
TABLE OF CONTENTS OF THE THESIS
1. Introduction
1.1. Overview of phenomena and historical aspects
2. Phenomenology of GRBs
2.1. Prompt emission
2.2. Progenitors
2.3. Afterglow
2.4. General Ingredients
3. Physics of GRBs
3.1. Relativistic effects
3.2. Relativistic shocks
3.3. Particle acceleration
3.4. Synchrotron radiation
3.5. Inverse Compton
4. Internal shock model
4.1. Fireball
4.2. Internal shocks
5. Models
5.1. Dynamics and Kinematics
5.2. Magnetic field and synchrotron radiation
6. Results
7. Conclusion
DESCRIPTION
This master thesis presents the original work of student Luca Grasitelli, caring the title
“Physical Parameters of the Relativistic Shock Waves in a Sample of Gamma Ray
Bursts”. It is separated in a five methodical parts, presenting the historical and
phenomenological overview of the GRB phenomena, main physical processes employed
general description of the current used model, modifications in dynamics and kinematics of
the internal shock scenario and a chapter about results. This work is presented on the 108
pages, with 25 figures and 6 tables. At the end there is a detailed list of quoted references.
2
In the first methodological part including the chapters (Introduction and
Phenomenology of GRBs) author gives very interesting details about accidental discovery
and initial attempts to explain the origin and purpose of the observed phenomena, as well as
the vast number of approaches used for theoretical explanation. Also, in the chapter 2 a
systematic overview of the physical and observational properties are presented, including the
details about prompt emission in gamma phase where specific retrospective view is given for
light curves recorded in the first minute of event.
In the next methodological unit (Physics of GRBs) basic physics of GRBs is
presented with the particular attention given to the relativistic effect reflected in the special
relativity contraction and dilatation effects, as well as on the relativistic Doppler Effect.
The most important and in front of all crucial for this thesis is the description of
central engine located in the core of GRBs. It is widely believed, on the basis of temporal
variability argument, that GRBs are compact objects expanding in the form of fireball or
collimated material ejection with ultra relativistic velocities. Author in this thesis within the
chapter (Internal shock model) address this issue with particular care, presenting the basics
of the fireball model and creation of the internal shocks during the first phase of the GRB
event. Also, it is stressed that the prompt emission observed in the gamma domain arises
from the mutual interaction of the shells with different velocities. Namely, in the frame of the
internal shock model, shock interaction creates the pulses in the lightcurve which are
superposed one to another creating the observed lightcurve. Then, with particular care, author
gives the description of the model used to evolve the relativistic shell expanding from the
inner engine outward (chapter Models). It is worth to mention the detailed derivation of the
basic system of differential equations necessary to solve in order to get basic variables of
expanding shocks.
At the end there is of most important chapter (Results) presenting the results author
get from the presented model, as well as the extracted parameters for the expanding shells in
the first phase of a GRB event. It is interesting to notice the hard work on fitting the 10 most
complex observed GRBs light curves. The ability to fit these light curves automatically
present the argument for claiming that all GRBs (or at least the long ones) belong to the same
type of event with the same progenitor. At the end as we mentioned there is a tabular
presentation of extracted shock model parameters.
In the Conclusion the author summarized and discussed the internal shock model
used in this thesis and outline the main results.
3
CONCLUSION
The Master thesis of the candidate Luca Grasitelli entitled “Physical Parameters of
the Relativistic Shock Waves in a Sample of Gamma Ray Bursts” describes very actual
problem of the gamma ray bursts, that still after more than 40 years of research present a
mystery. The selection of the theme, the conceptual approach using the scientific method and
presentation of the results, confirm that the author has invested much of hard working hours
during the calculation and writing the thesis.
On the basis of detailed analyze of the Master thesis of the candidate Luca Grasitelli,
entitled “Physical Parameters of the Relativistic Shock Waves in a Sample of Gamma
Ray Bursts”, members of the Examination Committee agree in their decision that this
research work is well done and the results are presented in a clear way.
Taking into account all stated above, the examination Committee concludes that the
Master thesis of the candidate Luca Grasitelli entitled “Physical Parameters of the
Relativistic Shock Waves in a Sample of Gamma Ray Bursts” satisfies all necessary
condition for a public defense.
Belgrade, 25. June 2012.
Examination committee:
1.Prof. Dr Dejan Urošević, mentor
2.Prof. Dr. Luka Č. Popović
3.Assis. Prof. Dr Dejan Arbutina
4. Dr Saša Simić, Researcher
4