Gamma-Ray Burst Seminar

Pawan Kumar


This seminar series is intended for anyone interested in gamma-ray burst, and its relation to other fields in astrophysics such as supernovae, star formation and cosmology. No prior knowledge of GRBs is needed to attend the seminars. We shall meet on Mondays at 3:30 pm. The first meeting, on January 28th, will provide an overview of the field and the main unsolved problems. In the following weeks we shall cover various topics, outlined below, systematically. The format of the meeting will be a 10-15 minute lecture providing a summary of the main points of the topic for the week. This will be followed by a discussion of the topic for about 30 minutes.

Toward the end of each meeting we hope to spend at least 5-10 minutes describing and discussing research problems related to the topic of the week. It is expected that participants will read the "suggested readings" and will actively participate in the discussions.


Week #1 Jan 28

Overview of main results

Basic observational properties of gamma-ray bursts will be discussed. We will also discuss the reason as to why the material ejected in these explosions should have high Lorentz factor and provide an overview of GRBs and its connection with star formation, cosmology etc.

Suggested reading:

1. Fishman & Meegan, 1995 ARA&A, 33, pp. 415-437 + section 6
2. Meegan et al., 1992, Nature 355, 143
3. Piran, 1999, Physics Reports, vol. 314, pp. 575-667

Week #2 Feb 4

Basic Relativistic hydrodynamics

Relativistic hydrodynamics and relativistic shock will be discussed.

Suggested reading:

1. Landau & Lifshitz (1982 Edition), Vol. 6, sections 125 & 126 (including the problems; especially #4)
2. Blandford & McKee, 1976, The Physics of Fluids, Vol. 19, 1130, sections 1, 2, 3, 4a & 4b

Week #3 Feb 11

Fireball Model (initial acceleration and shock)

We will discuss how radiation drives relativistic expansion i.e. when large amount of energy (say 1053 erg) is deposited in a small
region of space of radius ~ 100 km, relativistic expansion follows. We will also discuss the subsequent dynamics of the expanding material.

Suggested reading:

1. Bohdan Paczynski, 1986, ApJ 308, L43-46
2. Jeremy Goodman, 1986, ApJ 308, L47-50
3. Sari & Piran, 1995, ApJ 455, L143 (section 2 only)

Week #4 Feb 18

Radiative processes: Synchrotron & Inverse Compton

A brief survey of the main radiative processes relevant for GRBs will be discussed in this session. Attempt will be made to discuss the
generation of magnetic field behind shock and particle acceleration; these are major unsolved problems.

Suggested reading:

1. Rybicki & Lightman sections 5.1 & 5.2
2. Rybicki & Lightman sections 6.1-6.5 & 6.8
3. Rybicki & Lightman sections 7.1-7.6

Week #5 Feb 25

Afterglow from a spherical relativistic explosion

We will discuss how to calculate light-curves from a spherical,
relativistic, shock front.

Suggested reading:

1. Summary of the latest observational results on the afterglow discussed by Kumar.
2. Wijers, Rees and Meszaros, 1997, MNRAS 288, L51-L56.


Week #6 March 4

Afterglow from non-spherical explosions

We will consider a non-spherical relativistic outflow and calculate
light-curve resulting from the interaction of this outflow with ISM.

Suggested reading:

1. James Rhoads, 1997, ApJ 487, L1
2. Kumar & Panaitescu, 2000, ApJ 541, L9
3. Kulkarni et al., 1999, Nature 398, 389 (astro-ph/9902272)
4. Harrison et al., 1999, astro-ph/9905306
5. Dai and Lu, 1999, ApJ 519, L155 (steepening of LC due to nonrelativistic transition)

Week #7 March 18

Properties of GRBs from afterglow light-curves

We will discuss what we have learned about GRBs, the energy in the explosion, the jet angle, the property of the surrounding medium,
this week. The low density for ISM we find will also be discussed.

Suggested reading:

1. Panaitescu & Kumar, 2001, ApJ 560, L49
2. Piran, Kumar, Panaitescu & Piro, 2001, ApJ 560, L167
3. Frail et al., 2001, ApJ 562, L55
4. Scalo & Wheeler, astro-ph/0105369


Week #8 March 25

Collapsar & Neutron star merger models for GRBs

Suggested reading:

1. Narayan, Paczynski & Piran, 1992, ApJ 395, L83
2. MacFadyen & Woosley, 1999, ApJ 524, 262
3. MacFadyen et al., 2001, ApJ 550, 410


Week #9 April 1

Supernova explosion, non-spherical explosion

Led by Craig Wheeler

Suggested reading:

1. Craig Wheeler, Jan 2002, Sky and Telescope article.
2. Hvflich, Wheeler & Wang, 1999, ApJ, 521, 179
3. Khokhlov, Hvflich, Oran, E. S., Wheeler, Wang, L. & Chtchelkanova, 1999, ApJ, 524L, 107
4. Wheeler, Yi, Hvflich & Wang, 2000, ApJ, 537, 810
5. Wheeler, Meier, and Wilson, 2001, astro-ph/0112020


Week #10 April 8

Prompt gamma-ray light-curves and various correlations
Led by Brad Schaefer

Topics: gamma-ray spectrum; evolution of spectrum within a pulse and as a function of time. Correlation between GRB duration and
spectral hardness, and other correlations.

Suggested reading:

1. Liang & Kargatis, 1996, Nature, 381, 49 (Spectral evolution)
2. Walker, Schaefer, & Fenimore, 2000, ApJ 537, 264 (Blackbody spectra during bursts).
3. Mallozzi et al. 1995, ApJ, 454, 597 (E_peak distribution).


Week #11 April 15

Iron lines? Connection of GRBs with star formation etc.

Suggested reading:

1.Piro et al., 2000, Science, vol. 290, p. 955
2.Bloom et al., 2002, to appear in AJ in March, astro-ph/0010176

Week #12 April 22

Gamma-ray bursts as probe of cosmology

Topics: Lag & Variability as distance indicators; GRB Hubble diagrams. Star formation rates out to z~10. GRBs as light sources.
Ionization history of the Universe. Extreme limits on variations of speed of light from GRBs.

Suggested reading:

1.Reichart and Lamb, 2000, ApJ 536, 1-18
2.Reichart and Lamb, astro-ph/0109037 (Texas Symposium)


Week #13 April 29

Research problems in GRB