Transcript Future European Missions

X-ray Afterglows of Gamma-ray Bursts
David Burrows
The Pennsylvania State University
Swift X-Ray Telescope PI
GRB afterglows
Afterglow
E ~ 1053 ergs
PreBurst
Burst
Shock
Formation
T=0s
T ~ 102 s
R = 3 x 1012 cm
R = 106 cm
Γ~
103
T ~ 3 x 103 s
R = 1014 cm
T ~ 106 s
R = 3 x 1016 cm
LOCAL MEDIUM
Fireball model: synchrotron emission from power-law distribution of electrons
in highly relativistic outflows
GRBs and Swift
20 November 2004
Swift Instruments
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UVOT
BAT
BAT
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XRT
UVOT
XRT
Spacecraft
All Swift data are immediately public
http://swift.gsfc.nasa.gov/sdc/
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Burst Alert Telescope (BAT)
– 15-150 keV
– 2 sr field of view
– CdZnTe detectors
– Most sensitive gamma-ray
imager ever
– Detect ~100 GRBs per year
X-Ray Telescope (XRT)
– 0.2-10 keV
– Few arcsecond positions
– CCD spectroscopy
UV/Optical Telescope (UVOT)
– 170 – 650 nm
– Sub-arcsec positions
– Grism spectroscopy
– 6 UV/optical broad-band filters
– 22nd mag sensitivity (filtered)
Spacecraft
–
–
Autonomous re-pointing, 20 - 75 sec
Onboard and ground triggers
Swift GRBs (> 440 so far)
FRED
Short GRB
Fast Rise Exponential Decay
Short GRB
90% followed up with XRT observations
Swift X-ray Afterglows
> 370 Prompt X-ray LCs
GRB 060204B
GRB 060211A
GRB 060306
GRB 060413
GRB 060428A
GRB 060502A
GRB 060510A
GRB 060510B
GRB 060729
1e2
1e6
Key Swift Discoveries
GRBs
– ~90% of world X-ray afterglows
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Complex X-ray lightcurves and flares
Key Swift Discoveries
VLT
GRBs
– 80% of world X-ray afterglows
 Complex X-ray lightcurves and flares
 Jet breaks (or not…)
– First shock breakout from stellar
surface: GRB 060218 / SN2006aj
– Short GRBs with large and small redshifts
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GRB 071227
(D’Avanzo et al. 2007)
Arcsecond localizations => evidence for compact mergers
New data hints at subclasses in redshift, offset, and progenitors
Key Swift Discoveries
GRBs
– 80% of world X-ray afterglows
 Complex X-ray lightcurves and flares
 Jet breaks (or not…)
– First shock breakout from stellar
surface: GRB 060218 / SN2006aj
– Short GRBs with large and small redshifts
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Arcsecond localizations => evidence for compact mergers
New data hints at subclasses in redshift, offset, and progenitors
– Nearby long GRBs with and without SNe
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Possible new classes of GRBs
GRB 060614 at z=0.125
(Gal-Yam et al. 2006)
Key Swift Discoveries
GRBs
– 80% of world X-ray afterglows
 Complex X-ray lightcurves and flares
 Jet breaks (or not…)
– First shock breakout from stellar
surface: GRB 060218 / SN2006aj
– Short GRBs with large and small redshifts
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Arcsecond localizations => evidence for compact mergers
New
data hints at subclasses in redshift, offset, and progenitors
z=6.7
– Nearby long GRBs with and without SNe
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Possible new classes of GRBs
– Metallicities of star forming regions in galaxies
to record high redshift (z=8.2) using GRBs

Includes transitions never before seen
GRB 050730 at z=3.97
(Chen et al. 2005)
Canonical LC: GRB 050315
Vaughan et al. 2005
0
t -5.2
1
 -1.90.9
2
3
4
t -0.4
t -0.7
 -0.730.11
Zhang et al. 2006, ApJ, 642, 354
t -(2+β) ~ t -3 (Kumar & Panaitescu 2000)
Emergence of afterglow
X-ray Flares
GRB 050730
Burrows et al. 2005, Science, 309, 1833
Romano et al. 2006, A&A, 450, 59
Falcone et al. 2006, ApJ, 641, 1010
Liang et al. 2006, ApJ, 646, 351
Burrows et al. 2006, X-ray Universe (ESA SP-604), 877
Guetta et al. 2007, AIP Conf. Proc., 924, 17
Chincharini et al. 2007, ApJ, 671, 1903
Falcone et al. 2007, ApJ, 671, 1921
Kocevski, Butler, & Bloom 2007, ApJ, 667, 1024
Morris, D. 2008, PhD thesis
X-ray Flares
3x
X-ray Flares
• ~ ½ of bursts have X-ray flares
• typical time scale ~ hundreds of seconds
Power law slope ~ -1.1
Width distribution of flares
Flare durations are proportional to
time since burst (Chincarini et
al.; Kocevski et al.).
=> Flare models should reproduce
this.
Kocevski et al. 2007
Chincarini et al. 2007
Chincarini et al., Falcone et al. examined 77
flares in 33 bursts from first full year of XRT
operations.
Flare rise and fall times
Mechanisms:
1) Ambient density fluctuations
2) Patchy shell
3) Refreshed shocks
4) Restarted central engine
Kinematically allowed regions for afterglow variability
Only a restarted central engine is
consistent with all X-ray flares.
In context of internal shock model,
this probably requires fall-back
of material at quite late times.
Ioka et al. 2005; Chincarini et al. 2007
Flare Mechanisms
(D. Morris, PhD thesis, 2008)
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Compare each flare to required
characteristics of several models
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Reverse Shock IC: 1
Cloud Model I: 0
Cloud Model II: 3
Internal Shocks: 11
Afterglow Onset: 1
Energy Injection: 3
Implies IS most likely model for
any particular flare, but likely
need several models to explain
the entire collection of GRB Xray flares
X-ray Flare Mechanism
Internal Shocks?
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All of previous points are consistent with internal shocks.
Spectral evolution of flares consistent with spectral evolution of
prompt pulses
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Examination of post-flare decay slopes suggests that “clock” is reset
at beginning of each flare
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Burrows et al. (2005, Science, 309, 1833)
Falcone et al. (2005, ApJ, 641, 1010)
Pagani et al. (2006, ApJ, 645, 1613)
Burrows et al. (2007, Phil. Trans. Royal Soc. A., 365, 1213)
Butler & Kocevski (2007, ApJ, 668, 400)
Liang et al. (2006 , ApJ, 646, 351)
Requires late-time activity of central engine => central engine
restarts as late at 104 s after burst.
Upscattered emission?
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Panaitescu (2008, MNRAS, 383, 1143)
Plateau Phase
GRB 060729
Plateau phase
~ 40 ks
Plateau Phase
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Thought to be energy injection into the external
shock, either by
1. Delayed impacts of slower shocks created at the time of
the burst, or
2. Late-time ejection of relativistic shells from the central
engine
 Difficult to distinguish between these alternatives in most
cases.
The Plateau of GRB 070110
Rapid decline
Small flare
Plateau
???
t-9
Troja et al. 2007, ApJ, 665, 599
Plateau Phase
Comparison with GRB 050904:
Troja et al. 2007, ApJ, 665, 599
Plateau Phase
Other recent examples:
Plateau Phase
Other recent examples:
Plateau Phase
Drop-offs:
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Steep decline cannot be caused in external shock
Requires long-lived central engine activity
Could be explained by magnetar spin-down in some
cases
Plateau Phase
Drop-offs:
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Steep decline cannot be caused in external shock
Requires long-lived central engine activity
Could be explained by magnetar spin-down in some
cases
Other Possibilities:
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Recovery from intense photohadronic phase that
depletes internal GRB blast wave energy:
Dermer (2007, ApJ, 664, 384)
Up-scattered FS emission: Panaitescu (2008)
− May help explain chromatic breaks
GRB 090709
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BAT/XRT lightcurve
GRB 090709
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XRT lightcurve
GRB 090709
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BAT power spectrum
– confirmed by K-W and INTEGRAL SPI-APS, Suzaku WAM
Markwardt et al. 2009, GCNC 9645
P = 8.06 s
Q ~ 11
p ~ 10-6
GRB 090709
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Very bright burst: F~ 2.6e-5 ergs/cm2 (Sakamoto et
al., GCNC 9640)
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Afterglow detected in H, K, not in J => z > 8.5 ???
(Aoki et al., GCNC 9634; Morgan et al., GCNC 9635)
– But, reports of very early marginal detections in r’ suggest
low redshift (Cenko et al., GCNC 9646)
– NH measured by XRT suggests low redshift (Butler et al.,
GCNC 9639; Rowlinson et al., GCNC 9642)
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No galaxy found in deep optical obs (i’ > 25.2,
10.4m GTC) (Castro-Tirado et al., GCNC 9655)
– Nondetection of host galaxy, 8 s QPO, high b (200) and
high NH suggest Galactic magnetar
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No radio detection by WSRT or VLA
The Future of Swift
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Selected as #1 mission in the 2008 NASA Senior Review:
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In the next 3-4 years we will obtain
more high redshift GRBs
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more GRBs with good optical observations,
more short GRBs, and
more unusual cases (like 061007, 060614, 070110, …)
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GBM: will provide MeV-range spectral data for many Swift GRBs
LAT: will discover very high energy (GeV) GRBs that can be localized by Swift
Enhanced LIGO (2009)
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GRB 090709: QPO ???
Fermi / Swift synergy
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GRB 090423: z=8.2
Will double detection range, may permit detection of inspiral sirens
Long-term: Advanced LIGO (c. 2013)
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Simultaneous detection of short GRB by Swift and LIGO would provide “smoking
gun” for merger picture
NS-NS inspiral out to 300 Mpc – up to 3/d
NS-BH inspiral to 650 Mpc
Short GRBs
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Major discovery of Swift is
the first localizations of
short GRBs, and the
discovery that they occur
in different environments
than long GRBs
Consistent with origin from
different progenitors
(merging compact objects
rather than collapsar)
GRB 050509B
100x-1000x
fainter than
typical AG
BAT: t-1.3
XRT: t-1.1
Chandra
t90 = 0.04 s, Fluence = 2E-8 ergs/cm2
XRT counterpart in first 400 s, fades
rapidly. 11 photons total.
Location in cluster at z=0.226, near earlytype galaxy.
Possible NS-NS merger?
XRT error circle
on VLT image.
XRT position is
9.8” from a
bright elliptical
galaxy at
z=0.226
GRB 050724
WHT
t90 = 1 s by BATSE
definition. (But long
soft tail.)
30x brighter
thanidentified on
Optical
transient
GRBof050509B.
edge
object D, an early-type
2)
(6E-7 at
ergs/cm
galaxy
z=0.257,
L=1.7L*,
SFR < 0.02 Mo/yr.
Another old, nearby elliptical
galaxy associated with a short
GRB!!
Wiersema et al. 2005, GCN 3699
GRB 050724
Late-time bump (~1/2 day)
Possible evidence for NS-BH merger?
t-0.8
t90 = 1 s by BATSE
definition. (But long
soft tail.)
30x brighter than
GRB 050509B.
(6E-7 ergs/cm2)
No evidence of jet break,
θj > 0.5 rad for reasonable jet parameters
Slewed in 75 s. Very odd
X-ray lightcurve.
Grupe et al. 2006
Long-Term Future

Beyond Swift: the high z universe
– Swift may be detecting high z bursts, but ground-based
observations are required to identify them
– SVOM
– JANUS: identify high z GRBs and QSOs
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Reionization
Star formation at high z
– Xenia: High resolution spectroscopy of GRBs
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Reionization
First stars
Cosmic Structure
WHIM
Summary
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Swift has compiled a large database of bursts and their X-ray
and optical afterglows, discovering
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Swift has increasingly become the satellite of choice for
multiwavelength, rapid-response Targets of Opportunity
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Complex X-ray afterglows
X-ray flares, implying long-lived central engine activity
Prompt, accurate localization of short GRBs -> mergers
Bright, high-z bursts
CVs and novae
SNe
Galactic transients
AGN and blazars
http://www.swift.psu.edu/too.html
Future prospects:
– Swift/Fermi synergy
– Swift/LIGO synergy -> compact mergers
– JANUS, SVOM, and other proposed missions will focus on high-z