Swift Latest Results Torun 2005

1

ly Searching the Sky The First
Three Years of the Swift Gamma-Ray Burst Explorer
John Nousek (Penn State University)
III Cosmic Ray Astrophysics School - Arequipa,
Peru 1 Sep 2008
2
Talk Outline

• GRBs Pre-Swift
• GRB Phenomenon
• Pre-Swift GRB Paradigm
• Swift Era
• Swift satellite
• Swift discoveries
• Challenges to the GRB Paradigm
• Short GRBs
• Canonical X-ray light curves
• Lack of jet breaks/chromatic jet breaks
• X-ray flares
• Swift GRB science in the future
• What to do with Swift for the next four years?

3

GRBs Pre-Swift
What did we know about GRBs before Swift?
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History of GRBs

• GRBs discovered in 1969 by Ray Klebesadel of LANL
• Vela satellites monitored Nuclear Test Ban
  treaty
• Data published in 1973

• Compton Gamma-Ray Observatory launched on 5
  April 1991

• BATSE 2609 bursts in 8.5 years

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Compton Observatory Era
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Beppo-SAX HETE-2 Era
GRB 970228 - BeppoSAX
GRB 971214 - Keck
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The Time Gap
Swift
Beppo SAX data
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GRB Progenitors
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The Swift Era
What have we learned so far from Swift?
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Swift launch 20 Nov 2004 !!
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MOC Facility
Located in State College, PA 4 km. from Penn
State campus Flight Operations Team (FOT)
responsible for observatory Health
Safety Science Operations Team (SOT) -
responsible for scientific operation of Swift
Has continuously operated Swift successfully from
L80 minutes to now!
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Observing Scenario
1. Burst Alert Telescope triggers on GRB,
calculates position on sky to 1 arcmin
2. Spacecraft autonomously slews to GRB position
in 20-70 s
3. X-Ray Telescope determines position to 2-3
arcseconds
4. UV/Optical Telescope images field, transmits
finding chart to ground
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BAT GRB Position Accuracy
GRB 050215b
GRB 050319
GRB 050315
XRT
BAT FSW (3 radius)
GRB 050406
GRB 050416a
GRB 050509a
Mean BAT position error 52 arcseconds
T. Sakamoto
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300 GRB discovered 85 with X-ray detections
95 with XRT _at_ Tlt200 ks 60 with optical
detection (UVOT ground) 9 short
GRBs
Swift Statistics
gt400 non-GRB TOOs gt100,000 slews
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Redshift and Time Distributions

• Average Redshift
• Pre-Swift z 1.2
• Swift z 2.3

Analysis by Neil Gehrels
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2.20 050922C 2.17 070810 2.15 071020 2.04 070611 1
.95 050315 1.56 050801 1.55 051111 1.55 070125 1.5
1 060502A 1.50 070306 1.49 060418 1.44 050318 1.31
061121 1.29 050126 1.26 061007 1.17 070208 1.16 0
61126 0.98 071010 0.97 070419A 0.95 071010B 0.94 0
51016B 0.84 060814 0.84 070318 0.83 050824 0.78 06
0202 0.76 061110A 0.70 060904B 0.65 050416A 0.61 0
50525A 0.59 050223 0.54 060729 0.44 060512 0.30 05
0826 0.125 060614 0.089 060505 0.033 060218
6.29 050904 5.47 060927 5.3 050814 5.11 060522
4.9 060510B 4.41 060223A 4.27 050505 4.05 060206 3
.97 050730 3.91 060210 3.71 060605 3.69 060906 3.6
3 070721B 3.53 060115 3.44 061110B 3.43 060707 3.3
6 061222B 3.34 050908 3.24 050319 3.22 060526 3.20
060926 3.08 060607A 2.95 070411 2.90 050401 2.82
050603 2.71 060714 2.69 071031 2.68 060604 2.61 05
0820A 2.50 070529 2.45 070802 2.43 060908 2.35 051
109A 2.35 070110 2.31 070506 2.30 060124
72 Swift Long GRB Redshifts
lt z gt 2.3
Number
Gehrels et al. 2007
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GRBs now in the Swift era
How has the paradigm changed with the Swift
discoveries?
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Short vs Long GRBs
Short GRB
Long GRB
Cnts/s
Cnts/s
Swift first to discover counterpart to short GRB!
GRB 990123 - BeppoSAX HST Image
GRB 050509B - Swift VLT Image
Short GRBs in non-SF galaxies/regions
Long GRBs in SF galaxies
GRB
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Comparing Short and Long GRBs
Norris et al. 2006
GRB 061121 brightest long GRB GRB 061210
brightest short GRB
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Comparing Short and Long GRBs
Short GRB 051221A
GRB 061121 brightest long GRB GRB 061210
brightest short GRB
Kouveliotou et al. 1993
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Prompt vs Afterglow Correlation Analysis
Gehrels et al. 2007
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Short GRBs - Opportunity
Short bursts versus Long bursts -
Different physics - Different environments
- Different population of stars -
Different ages distances New tool for
studying stellar evolution binary
formation Direct tie-in to emerging GW
field CHALLENGE Short GRBs are weak in g,
X, opt Current knowledge from few events
GRBs with afterglow - special subclass? Which
are short, which are long? Needed more short
GRBs rapid, sensitive
follow-up high resolution
optical imaging
Progress on short GRBs - a tough nut to crack!
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Pre-Swift X-ray light curve
Swift
Beppo SAX data
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Canonical Swift XRT Light Curve
(steep due to light delay effects from end of
prompt emission)
Flare
(plateau due to energy injection into
external shock)
(normal external shock)
Jet Break
GRB060428A Courtesy of D. Burrows
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Jet Break
Jet
Relativistic beaming ? G-1
Torus
Frail et al. 2001, ApJ, 562, L55
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Jet Break
Jet break knowledge is critical for GRB
energetics E ? Eiso(1-cos ?j)
Frail et al. 2001, ApJ, 562, L55
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GRB050416A
GRB060729 is also still going with no jet break
after 2 months!
a 0.81
gt 58 Days
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Jet Break
For some Swift bursts there is either no jet
break, or there is a chromatic break ? Either jet
angle is very wide or Density is very low
or Basic model is wrong
Jet
Relativistic beaming ? G-1
Torus
Frail et al. 2001, ApJ, 562, L55
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Giant X-ray Flare GRB 060526
gt 100x increase!
Peak 220 s
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Giant X-ray Flare GRB 050502B

500x increase!
GRB Fluence 8E-7 ergs/cm2 Flare Fluence 9E-7
ergs/cm2
Peak 700 s
Burrows et al. 2005, Science Falcone et al.
2005, ApJ
Note establishment of AG before flare begins.
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Swift XRT X-ray Flares
116 prompt afterglow detections 50 have X-ray
flares Typically in first 20 min. Dynamic
range 1.3x 500x
GRB 050726
GRB 050730
Flare analysis courtesy of Dave Burrows
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Flares in Short GRBs
?
Mechanism for flares must also operate in the
context of short GRBs.
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The Future
What to do with Swift for the next four years?
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High-z GRB - Opportunity
Prediction - 7 - 10 of Swift GRBs at zgt5
(Bromm Loeb, Jakobbson et al., Lamb
Reichart) - 0.5 at zgt10 Swift measurements
- 4 out of 72 6
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
GRBs are bright !
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High-z GRB - Opportunity
GRBs are briefly the most luminous sources in
the universe .... across the E-M
spectrum! High-z GRBs offer unique tool for
studying - Reionization era -
Abundance history of universe - First stars
first light - Star formation rate
history - Gas and dust content of early
galaxies CHALLENGE Difficult to determine
redshift for high-z bursts Bursts not detected
in optical can be common dark GRBs or rare
high-z events. Needed rapid response, large
telescope, IR spectrograph Needed redshift
indicators, good position on sky for follow-up
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GRB 060218 GRB Supernova
Super-long GRB - 35 minutes BAT, XRT,
UVOT during GRB z 0.033 d 145 Mpc
SN 2006aj SN Ib/c Eiso few x 1049 erg
- underluminous Epeak 4.9 keV -
XRF
Pian et al. 2006
Campana et al., Mazzali et al., Pian et al.,
Soderberg et al.
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Underluminous GRBs - Opportunity
Observations of nearby GRBs leading to
breakthroughs in understanding of - GRB
central engine - Jet outflows - CC
supernovae CHALLENGE Data are scarce and
puzzling 6 events, all different -
980425 underluminous - 031203
underluminous - 030329 normal GRB -
060219 XRF underluminous - 060505 no SN
- 060614 no SN Needed better detection
of faint GRBs
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The Year of High-z Bursts
Alerts from Swift data - BAT T90,
variability, spectrum (Ukwatta Sakamoto 2007)
- X-ray light curve flaring (Morris et al.
2007) - X-ray NH correlations (Grupe et
al. 2007) - UVOT photometric data (Vanden
Berk 2007) Sun Angle - 50 of time with
Swift pointing gt9hr from sun Follow-up
Community - Small medium telescopes to
identify candidates - Large telescope for
spectra of likely candidates
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Sun Angle
Pointing angle relative to Sun
Advantage of high sun angle
Sakamoto 2007
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BAT Low Threshold Experiment
Lower BAT thresholds 2 triggers slews per
day Observe with NFIs for 2 ks Trigger is
deemed a GRB if afterglow is detected No
Notices or Circulars for triggers without
afterglow Observers can sign up to receive all
triggers, with suitable warnings Experiment to
last 1 month
Barthelmy, Palmer, Fenimore
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Opportunities for Joint Observations
AGILE GLAST H.E. g-rays
JWST (2013) IR
ALMA (2012) radio mm/submm
ICECUBE (2009 -2011) neutrinos
LIGO (2014 - ALIGO) gravitational wave 30
NS-NS mergers per year
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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