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Understanding The Mechanisms Behind GammaRay Bursts

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Title: Understanding The Mechanisms Behind GammaRay Bursts


1
Understanding The Mechanism(s) Behind Gamma-Ray
Bursts
  • Chris Fryer (Univ. of Arizona/LANL)

2
10 Lectures
  • Lecture 3 Extrapolating from the Observations
    to the Engine Fireball Physics. A review of
    how relativistic jets produce GRBs.
  • Lecture 4 GRB Engines (Past and Current).
    Review of GRB models.
  • Lecture 5 Black Hole Accretion Disk Models.
    Black Hole accretion and jet production.
  • Lecture 1 GRBs the Historical Perspective. A
    review of the discovery of GRBs up to the first
    localization of a GRB
  • Lecture 2 Observational Constraints on the
    Central Engine. GRBs in the afterglow era
    (constraints on the GRB engine).

3
10 Lectures
  • Lecture 8 Why Supernovae Fail. Review of SN
    engine (NS and BH formation).
  • Lecture 9 Supernova/GRB connection.
  • Lecture 10 Prospects for the future. Future
    models and future observational missions.
  • Lecture 6 Physics of Compact Object Mergers. A
    review of current progress on NS/NS, BH/NS and
    BH/WD mergers.
  • Lecture 7 Physics behind collapsars. A review
    of the collapsar (a.k.a. hypernova, failed
    supernova model).

4
GRBs The Historical Perspective
  • 1967 Discovery Vela Satellites
  • 1972-1991 Golden Age for Theorists - no
    constraints and a world of proposals
  • 1991 Constraining the theories CGRO (BATSE)
    finds isotropic distribution
  • 1996 Localization BeppoSAX localizes bursts
    to get redshifts and host-galaxy information

5
Gamma-rays are photons with energy above roughly
100keV, corresponding to temperatures above 109
K. The Earths atmosphere is optically thick to
gamma-rays. Gamma-ray studies require balloons,
rockets, or satellites.
6
   
Gamma-Ray Bursts and the Cold War
In the 1950s, the US and USSR decided to ban The
testing of nuclear weapons.
How do we check?
  • Seismic Waves
  • Low Frequency Sound Waves
  • Gamma-Rays

Crashed Balloon Became Roswell Alien!
Mogul Project
7
Gamma Rays in the Cold WarVela Satellites
Stats e.g. Vela 5A
  • Scintillation X-ray Detectors
    3-12keV,6-12keV Area 26cm2
  • CsI Gamma-Ray Detectors -
    150-750keV Volume 60 cm3

8
Vela Satellites
  • 105 km Orbits
  • Launched in pairs launched 1963-1965
  • Operated until 1979
  • All satellites allowed for some localization.

9
First Detected Gamma-Ray Burst
10
Vela Satellites - Results
  • 73 Bursts in Gamma-Rays over 10 years
  • Not from the Earth (not weapons tests) and not in
    the plane of solar system

Ray Klebasadel
11
GRBs The Golden Age for Theory
What Theorists Know Constraints on Theory
What we know/dont know from observations
  • Not Russian tests!
  • Lots of gamma-ray emission
  • No distances Total energy and location unknown!
  • Too few objects to get spatial distribution!
  • Cant be thermal emission alone!
  • Options I)
    Relativistic Boosting from jet or compact object!
    II) Nuclear Lines
    (e.g. Nickel Decay)
  • III) Magnetic Fields.

12
Creativity of Theorists
With so few constraints, theorists came up with
all Sorts of models relying on a range of physics.
Three Classes based on location
Galactic
SS
  • Solar System
  • Galactic
  • Cosmological (outside of the Milky Way)

Energy Observed Flux d2
Energy Requirements Vary over 20 orders Of
magnitude!
Cosmological
13
The first gamma- Ray burst model Appeared
before The Vela results Were published! By 1992,
over 100 models Existed! Despite this Number,
the Currently favored Model is not on This list!
14
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15
Gamma-Ray Bursts in the Solar System
  • Lightning in the Earths atmosphere (High
    Altitude)
  • Relativistic Iron Dust Grains
  • Magnetic Reconnection in the Heliopause

Red Sprite Lightning
16
Gamma-Ray Bursts in the Milky Way
  • Accretion Onto White Dwarfs
  • Accretion onto neutron stars
    I) From binary companion
    II) Comets
  • Neutron Star Quakes
  • Magnetic Reconnection

X-ray Novae
17
Galactic Gamma-Ray Bursts Soft Gamma-Ray
Repeaters
  • One Class of GRBs
  • Is definitely Galactic
  • Soft gamma-ray
  • Repeaters (SGRs)
  • Characteristics
  • Repeat Flashes
  • Photon Energy
  • Distribution lower
  • Energy than other
  • GRBs (hard x-rays)

X-ray map of N49 SN remnant. The white Box shows
location of the March 5th event
18
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19
The Soft Gamma-Ray Repeater/Anomalous X-ray
Pulsar Connection
SGR-like Bursts from the AXP 1E 2259586 Kaspi,
Gavriil, Woods (2002)
Chryssa Kouvelioutou
SGRs were believed to be neutron stars, but
observations of an Anomalous X-ray Pulsar with
SGR-like bursts made this connection irrefutable.
Vicky Kaspi
20
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21
Models for SGRs
  • Accretion I) Binary Companion
    - no companion seen II) SN Fallback Too long
    after explosion
  • Magnetic Fields
  • 1015 G Fields -Magnetars

22
If normal GRBs are also neutron stars, GRBs
should Also center around the Galactic
Equator. This is a Prediction of the Galactic
Models!
Plane of the Milky Way Galaxy
23
Extragalactic Models
  • Large distances means large energy requirement
    (1051erg)
  • Event rate rare (10-6-10-5 per year in an L
    galaxy) Object can be exotic

24
Cosmological Models
  • Collapsing WDs
  • Stars Accreting on AGN
  • White Holes
  • Cosmic Strings
  • Black Hole Accretion Disks
    I) Binary Mergers II)
    Collapsing Stars

25
Black-Hole Accretion Disk (BHAD) Models Binary
merger or Collapse of rotating Star
produces Rapidly accreting Disk (0.1 solar Mass
per second!) Around black hole.
26
Compact Object Mergers
MaxRuffert
27
Massive Star Collapse
Stan Woosley
Collapsar Model Collapse of a Rotating Massive
Star into a Black Hole
Main Predictions Beamed Explosion,
Accompanying supernova-like explosion
28
Compton Gamma-Ray Observatory
April 5, 1991 June 4, 2000
CGRO Had Four Instruments Covering A range of
Wavelengths And opening Angles!
29
BATSE - Burst And Transient Spectrometer
Experiment
BATSE Module
BATSE Consists of two NaI(TI) Scintillation
Detectors Large Area Detector (LAD) For
sensitivity and the Spectroscopy Detector (SD)
for energy coverage
8 Detectors Almost Full Sky Coverage Few
Degree Resolution 20-600keV
30
BATSE Results - Isotropy
31
Galactic Models
32
BATSE Results IsotropyCosmological Models
Favored!
33
Gamma-Ray Burst Lightcurves
GRB990316
GRB Lightcurves have A broad range of
Characteristics
Fast Rise Exponential Decay FREDs
GRB970508
34
Gamma-Ray Burst Lightcurves
GRB990123
Double bursts and Extended Structures
No standard shape Exists!
GRB980703
35
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36
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37
Gamma-Ray Burst Durations
Two Populations Short 0.03-3s Long
3-1000s Possible third Population 1-10s
38
Gamma-Ray Burst Duration vs. Energy Spectrum
39
BATSE - Summary
  • GRBs are Isotropic The beginning of the end for
    Galactic Models, but persistent theorists move
    the Galactic Models to the Halo
  • GRBs come in all shapes and sizes but two obvious
    subgroups exist - I)
    Short, Hard Bursts
    II) Long, Soft Bursts

40
BeppoSAX
Italian-Dutch Satellite Launch April 30,
1996 Goal Positional Accuracy Honoring Giuseppe Occhialini
41
High Pressure Gas Scintillation Proportional
Counter
WFC 40o x 40o, 2-28keV
42
BeppoSAX Instruments
HPGSPC(Phoswitch)
LECS/MECS
  • Xenon Gas Scintillator
  • Energy Range .1-1keV (1-10keV)
  • 1 arc minute resolution
  • Goal Localize Object
  • HPGSPC - High Pressure Xenon/He Gas
  • Phoswitch - NaI(Tl), CsI(Na) Scintillators
  • 4-120keV (15-300keV)
  • Goal Broad Energy resolution in X-ray narrow
    field

43
GRB970228 first good localization
44
GRB070228 Optical Counterpart Discovered (with
corresponding optical localization!)
45
GRB 970228 host galaxy observed?
This blob, a peculiar Galaxy to be sure, Is in
the same position As the Burst! Could it have
been the GRBs host? The galaxy has a Redshift
of 0.695.
46
GRB 970508 Optical Counterpart
BeppoSAX X-ray Localization Allowed a The
Optical Transient to Be detected While still on
The rise. OT allowed Spectral Measurement!
47
GRB970508 Absorption Lines z0.835
flux
Metzger et al. 1997
Wavelength
Optical Emission
Absorption
Mg II
Mg II I
Fe II
flux
Fe II
Wavelength
48
Host Galaxy Detected for GRB970508
Z0.835
flux
Wavelength
49
Radio Twinkling can also be used to estimate the
GRB distance consistent with z0.835
Just as the Earths Atmosphere Causes light To
scatter Causing point Sources to twinkle, the
Interstellar Medium causes Radio emission To
twinkle. When The burst gets Large enough, Like
planets, the Twinkling stops.
50
Waxman, Kulkarni, Frail 1997
Tt, rc t Where c is speed of light
T0, point Source
ISM Scattering
Twinkle, Twinkle
Observer Always Sees Part of Burst
51
A crash Course in Scintillations
Scintillations determine the size of the source
in a model independent way. The size (1017cm)
is in a perfect agreement with the prediction of
the Fireball model.
52
Bursts Definitely Outside of Milky Way
This irrefutable Redshift forces The last
Stubborn Supporters (Don Lamb, Ed Fenimore,
Chris Fryer, Stirling Colgate) Of
Galactic Gamma-ray Bursts to accept That at
least Some bursts are Cosmological.
GRB970805 Nail in the Coffin For Galactic GRB
Models
53
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54
GRB Redshifts (2000)
55
But we only know about long-duration GRBs
56
BeppoSAX
  • First Good Localizations of GRBs
  • Opens up Afterglow science! Much more on this
    tomorrow!
  • Limited to Long-Duration Bursts

57
Summary
  • Vela Satellites Discovery of bursts of
    gamma-rays. Not man-made! First Burst in 1967,
    Published in 1972.
  • 1972-1991 Golden Age for Theorists no
    constraints, models can be anything! Two primary
    classes Galactic (Milky Way) and Cosmological.

58
Summary
  • 1991 CGRO launched (BATSE instrument 8
    detectors with nearly full sky coverage but
    limited spatial resolution.)
  • GRBs are isotropic the first rats begin jumping
    of the Galactic GRB ship.
  • Two distinct populations of burst durations
    long (1-1000s), soft and short (0.01-1s), hard)

59
Summary
  • 1996 BeppoSAX Gamma-ray and X-ray Instruments
    good localization!
  • 1997 - Afterglows Detected. Redshifts detected
    distances and energies (assuming explosion
    isotropy) of bursts now known for long-duration
    bursts.
  • Death of Galactic Models for long duration models
    (at least)!
  • Localizations open up the possibility to learn
    much much more!

60
Tomorrow Observational Constraints on the
Central Engine
  • GRB observations in the afterglow era
  • Host Galaxies
  • SN/GRB Connection
  • Energetics
  • Prompt Emission
  • Using GRBs as Cosmological Probes
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