Neil Gehrels

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Gamma Ray Bursts First Results from Swift
Neil Gehrels NASA Goddard Space Flight
Center UCSC visit May 6, 2005
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Lecture Plan
Gamma-ray burst current understanding Building
the Swift mission New results from
Swift Afterglow observations understanding the
fireball Redshifts and promise of using GRBs for
early universe studies SGR 1806-20 giant
flare Other science SN2005am, ...
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First GRB Detection by Vela Satellites
First GRB
Ray Klebesadel
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Discoveries in the 1990's
CGRO 1991 - 2000
Isotropic on the sky
X-ray afterglow discovery
BeppoSAX 1996 - 2003
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Optical Afterglows
GRB 990123 - HST

• GRBs in distant galaxies
• Average distance z 1
• Energy 1051 ergs in g-ray flash

GRB 971214 - Keck
2 Duration Classes
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Theories of GRBs
Collapsar - Massive Star Explosion
Neutron Star Merger

• short time
• structure
• small size

.
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Collapsar Modeling
Woosley, Zhang Heger
MacFadyen Woosley
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Fireball Model of GRBs
Meszaros Rees '97
E 1051 ergs
G 200
G 5
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Key Questions - Swift Requirements
Many GRBs detected (large gamma-ray
detector) Afterglow measurements x-ray
optical (multi-instrument payload) Measurements
quickly following GRB (fast moving
spacecraft) Data quickly to ground (direct
downlink distribution system)
What causes GRBs? What are short GRBs and XRFs?
What is the physics of the fireball? What were
the first stars and galaxies like in the early
universe?
Swift
BeppSAX data
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Swift Observatory
Orbit 600 km x 28 inclination Data
Downlinks TDRSS rapid (2 kbps) ASI Malindi gnd
station Operations Ops Center _at_ Penn
State Science Center _at_ GSFC BAT New CdZnTe
detector 100 GRBs/yr XRT Arcsec GRB
positions CCD spectroscopy UVOT Sub-arcsec
positions Grism spectroscopy Spacecraft Autonomou
s slews 20-75s

Spacecraft (Spectrum Astro)
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Hardware Pictures
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BAT Performance
Imaging
Source Detections - 1 month
Individual BAT Spectra - 1 Module
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Building an Observatory
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Arrival at KSC
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Ready for Launch at Kennedy Space Center
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Florida Becomes Hurricane Alley
Hurricane Frances Sept. 4
Hurricane Charley Aug. 13
VAB Damage
Hurricane Jeanne Sept. 25
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Observatory in Fairing
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Swift ResultsBursts Detected and Imaged
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Swift Early Operation
First XRT image (Cas A)
Instruments spacecraft working and returning
beautiful data!!34 gamma-ray bursts detected
First UVOT image (M101 galaxy)
Count Rate vs Time
BAT GRB 041223
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GRBs Imaged by BAT
Also observed GRBs from HETE (1 GRB) INTEGRAL
(2 GRBs)
GRB rate 93 GRBs yr-1 measured, 100 yr-1
predicted BAT background 12 kcnts/s measured,
13-17 kcnts/s predicted Scott Barthelmy - BAT Lead
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Swift Data Public as of April 5
Rapid BAT position (15 sec) Arcsecond XRT
position (90 sec) UVOT image (2 min)
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GRB 050319
BAT Light Curves
BAT Spectrum
BAT Image
XRT Light Curve
XRT Image
XRT Spectrum
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Understanding the Fireball
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Pre-Swift Afterglow Data
Flux
Time (days)
Harrison et. al. 1999
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XRT Afterglow Observations
23/24 XRT detections Lightcurves for
all Arcsec positions for all
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Imaging Challenges
BAT Error Circle
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Simple Decaying Lightcurve
What is this?
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• Sari et al. 1999 Frail et al 2001
• 3.3 (tbreak/1day)3/8 ((1z)/2)-3/8
  (Eiso-g/1053 ergs)-1/8 (hg/0.2) (n/0.1 cm-3)1/8
  
• z 1.24 Eiso 1.3x1052 erg
  tbreak 8x104 sec 0.9 day
• q 3.9 degrees

Jet Breaks
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XRF 050408 HETE-2
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a1 0.85
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a2 1.9
3
2

• G-1

1
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GRB 050401
Shallow Component
a1 0.66
GRB 050128
a2 1.44
Zhang Meszaros '04
a1 0.45
a2 1.25
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Discovery of Bright Early Afterglow
a1 2.5
a2 0.7
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BAT Flows Into XRT
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Primary acceleration phase of GRBs lasts
minutes, not seconds!!
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Afterglow Diversity
GRB050219a
GRB050128
GRB050117a
GRB050319
GRB050406
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XRT burst summary
XRT Afterglow Summary (Dave Burrows - XRT Lead)

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UVOT Upper Limits
4/15 UVOT detections
Time After the Burst (days)
0.001
0.01
0.1
0.001
0.010
0.100
1.000
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UVOT pushing into unexplored parameter space
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R Magnitude
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Previous Limit Line
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UVOT Detections
GRB 050319 - Variability!
GRB 050318
Pete Roming - UVOT Lead
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UVOT - SN 2005am
Lighcurve
Image near peak, March 3, 2005

Spectra
Unique early UV observations of a nearby (36 Mpc)
SN Study related to standard candle assumptions
- dependence of lightcurve on metallicity
K-corr
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GRB 041219a
Time of IR flash

• Second Swift GRB
• One of brightest and longest GRBs expected
• Observed by ground-based telescopes
• IR optical flash discovered during GRB (Blake
  et al., Vestrand et al.)

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Swift Partner Observatories (Kevin Hurley)
Milagro Gamma-ray Obs. (New Mexico) NASA (IRTF,
Hubble Spitzer) NOAO (CTIO, KPNO) Nordic Optic
Telescope (La Palma) Okayama Observatory
(Japan) Rapid Eye Mount Telescope (Chile) RAPTOR
(New Mexico ROTSE-II (New Mexico) SARA
Observatory (Arizona) SIRTF South African Large
Telescope Super-LOTIS (Arizona) TAOS Telescope
(Taiwan) TAROT Telescope (France) Tenerife
Observatory U.S. Naval Observatory
(Arizona) VERITAS Observatory (Arizona) WASP
Telescope (La Palma) WIYN Observatory
(Arizona) Wyoming Infrared Observatory XMM Newton

• AEOS Telescope (Hawaii)
• ARAGO Telescope (Antarctica)
• ARC Telescope (New Mexico)
• Brera Observatory (Italy)
• Chandra
• ESO (La Silla, Paranal, VLT)
• ESAs INTEGRAL mission
• Fast Alert MachinE (Italy)
• Faulkes Telescopes (Hawaii Australia)
• Galileo National Telescope (La Palma)
• Hubble Space Telescope
• Hobby-Eberly Telescope (Texas)
• INTEGRAL
• Isaac Newton Telescopes (La Palma)
• KAIT (California)
• W. M. Keck Observatory (Hawaii)
• Large Binocular Telescope (Arizona)
• LIGO (Louisiana and Washington)
• Liverpool Telescope (La Palma)

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The Early Universe
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Swift seems to be detecting GRBs at higher z than
previous missions
Burst Redshift __________________
__________ GRB 050126 1.29 GRB 050315
1.9 GRB 050318 1.44 GRB 050319
3.24 GRB 050401 2.94
____ Swift average 2.2 Pre-Swift
average 1.2
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Soft Gamma RepeatersShort GRBs
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SGR 1806-20 Amazing Giant Flare
(David Palmer)
GEOTAIL - Main Pulse
RHESSI Lightcurve
BAT Tail Lightcurve
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SGRs and Short GRBs

• December 27 flare from magnetar SGR 1806-20
• 100 times luminosity of previous SGR giant flares
  Lg 1046 erg
• Model magnetic explosion due to stress relief
  in crust Bext1015 G, Bin1016 G, ?
  B2/2mo1049 erg
• Giant flares in"nearby" galaxies could explain
  short GRBs
• Swift would detect
• flare to 60 Mpc with BAT, tail to 20 Mpc with
  XRT

Short GRB detected by BAT (but without slew and
XRT) Detection rate 1 per 2-3 months
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Observatory Capabilities

• TOO response in 1 hour to any transient
• Transient searches over much of sky every orbit
  by BAT
• Multiwavelength campaigns available on single
  spacecraft
• 4 targets per 90 min. orbit - huge number of
  observations
• All Swift data are public. Enjoy!

John Nousek Operations Lead
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Swift Development Team
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Swift Institutions
GSFC

• Executive Committee
• G. Chincarini - Brera Obs.
• N. Gehrels - GSFC
• P. Giommi - ASI
• K. Mason - MSSL
• J. Nousek - PSU
• J. Osborne - U. Leicester
• A. Wells - U. Leicester
• N. White - GSFC