Gamma Ray Burst Discoveries with Swift

1
Gamma Ray Burst Discoveries with Swift (and
Fermi)
Neil Gehrels NASA-GSFC June 26, 2009 XXIth
Rencontres de Blois
2
Outline

• ??? GRB background Swift
• ? Long GRBs
• - Explosions at high low redshift
• - Black hole birth
• ? Enigmatic short GRBs
• - Stellar mergers
• - Gravitational waves
• ? Fermi GRBs
• ? ? AF 447

Annual Reviews 2009 Gehrels, Ramirez-Ruiz and
Fox
3
GRB Spectra
ARAA 2009
4
GRB 990123 - HST
The GRB Phenomenon
Kouveliotou et al. 1993
Energy 1051 ergs in 30s flash of
g-rays ( 200 x MEarth c2) Distance lt
z gt 2.3 (Swift long GRBs) 11 Gyr light
travel time Jet Outflow highly relativistic
(G gt 100) 5 beams Variability msec time
structure in prompt burst Power source
gravitational infall on new-born BHs
Fruchter et al. 1999
Collapsar Model
5
Swift Mission
3 instruments, each with - images
- spectra - lightcurves Rapid slewing
spacecraft 100 GRBs per year
XRT Position - 5 arcsec
BAT Position - 2 arcmin
UVOT Position - lt 1 arcsec
.
.
Tlt10 sec
Tlt90 sec
Tlt2 min
6
Swift Mission
3 instruments, each with - images
- spectra - lightcurves Rapid slewing
spacecraft 100 GRBs per year
XRT Position - 5 arcsec
BAT Position - 2 arcmin
UVOT Position - lt 1 arcsec
.
.
Tlt10 sec
Tlt90 sec
Tlt2 min
7
BAT
32,000 CZT detectors
XRT
UVOT
8
August 2004
9
August 2004
November 2004
10
XRT lightcurve
What Swift Does
GRB 090530
BAT lightcurve
UVOT image
11
Long GRBs
12
GRBs from the Early Universe
z GRB Optical Brightness
6.29 050904 J 18 _at_ 3 hrs
5.6 060927 I 16 _at_ 2 min 5.3 050814
K 18 _at_ 23 hrs 5.11 060522 R
21 _at_ 1.5 hrs
GRB 050904 z 6.29 (12.8 billion year)
100,000 times brighter than galaxies at that
distance
GRBs brightest high redshift sources
Cusumano et al. 2005
13
Blast from the past! GRB 090423
GRB 050505 Spectroscopy
z 8.3 13.0 billion light years
Metallicity vs Redshift
GROND camera Grenier et al
Tanvir et al. 2009 Salvaterra et al. 2009
Savaglio 2006
14
GRB 090423
8.3
15
Long GRB Scenario
Massive star with H He envelope stripped Rapidl
y rotating
16
Long GRB Scenario
Massive star Rapid rotation Proto-neutron
star Collapse t lt 1 sec
17
Long GRB Scenario

• Accretion onto
• new black hole
• t 10's sec
• Jet emergence
• t 10 sec

MacFadyen Woosley
18
Short GRBs
19
BAT - 30 millisecond duration Spacecraft
slew in 52 sec XRT - faint source, fading
Host - Elliptical galaxy - low star
formation rate - z 0.225 No supernova to deep
limits
Cracking the Short Burst Problem
GRB 050509B
VLT image
20
Short vs Long Host Galaxies
GRB
Only in star forming galaxies Accompanied by
supernovae Collapsar model well supported
All types galaxies No supernovae
detected Neutron star merger model
21
Short GRBs Compared to Long GRB
43 short GRBs detected by Swift/BAT
Lower Redshifts lt z gt 0.4 short lt
z gt 2.3 long Weaker Afterglows
lt FX gt 7x10-10 erg cm-2 s-1 short lt
FX gt 3x10-9 erg cm-2 s-1 long Less Jet
Collimation ? 10 (wide spread) short
5 (wide spread) long Less Total
Energy 1049 ergs short 1051 ergs
long
Racusin et al. 2009
22
Implications for GW Detections
If all short GRBs due to NS-NS mergers ?
NS-NS merger rate is gt300 Gpc-3 yr-1
Consistent with NS-NS population synthesis
modeling O'Shaughnessy et al. (2005) For
aLIGO NS-NS merger sensitivity distance is 170 -
300 Mpc aLIGO detection rate is 6 - 30 yr-1
aLIGO on line in 2014 Swift will be in orbit
until gt 2020
(K. Thorne)
23
Black hole formation through binary neutron star
mergers
24
Fermi Gamma Ray Mission
Large Area Telescope (LAT)
Gamma-ray Burst Monitor (GBM)
LAT - 20 MeV - gt300 GeV GBM - 10
keV - 25 MeV
25
LAT GRB 080916C
XRT
Long GRB z 4.35 Extended emission
Lag in MeV/GeV onset Highly luminous
Lorentz factor (jet) gt 860 (?? absorption
argument)
LAT Collaboration, Science 2009
26
LAT GRBs
GRB 080825C GRB 080916C z 4.35
/-0.15 (GROND/photometric) GRB 081024B
short-duration burst GRB 081215A GRB
090217 GRB 090323 z 3.6
(Gemini/spectroscopic) GRB 090328 z
0.736 (Gemini/spectroscopic) GRB 090510
short-duration burst z 0.9 (VLT)
27
The Future is Bright
Continued Swift and Fermi gamma rays (to
2020)
JWST (2013) infrared
ALMA (2012) radio mm/submm
ICECUBE (2009 -2011) neutrinos
LIGO/VIRGO (2014 - ALIGO) gravitational wave
EXIST (2018) GRBs NIR HXR survey
28
Air France 447
29
Did AF 447 Encounter a TGF?
Pitot tube explanation does not make sense.
More likely cause is a Terrestrial ?-ray Flash
Similar to sprites, elves blue jets
also RHESSI, Fermi