Transcript Nobuyuki Kawai

Gamma-Ray Bursts
as a prototype of multimessenger/time-domain astronomy,
and the lessons we learned from
unexpected discovery
Nobuyuki Kawai (Tokyo Tech)
outline
• short GRB from the local universe?
• magnetar flare, and lack of GW
detection
• Lessons learned in GRB study
• prospects for EM counterpart of GW
event
2
Short GRB error boxes at nearby galaxies
Andromeda Galaxy (2.5 million light years)
Abbot et al. 2008, arXiv:0711.1163v2
M81/M82 Galaxy (12 million light years)
3
Frederiks et al. 2007, arXiv:astro-ph/0609544v3
short GRB 070201
Andromeda Galaxy (2.5 million light years)
• localized by IPN
• No plausible
gravitational wave
candidates within
180 s
• Exclude NS merger
at <3.5 Mpc
 magnetar flare!
• chance coincidence?
4
Abbot et al. 2008, arXiv:0711.1163v2
Giant Flares of SGR
•
(Soft Gamma Repeater )
8.1s
• Intense spike (<0.5s)
SGR0520-66 (5 Mar 1979)
contains most of
radiated energy (10441046 erg)
• followed by spinmodulated oscillation
SGR1900+14 (27 Aug 1998)
• slow X-ray pulsar in
quiescence
sec • Gal. plane or LMC:
young NS
SGR1806-20 (27 Dec 2004)
• Implied magnetic
field 1014-1015
gauss (“magnetar”)
5
Giant Flare of
SGR 1806-20
Neutron Star
Outer Core
Magnetic Field
X-ray counts
Terasawa et al. 2005
CEMs
MCP
• Magnetic energy
(>1046 erg) released
in 0.1 s
• crust fracture?
• No GW detected
corresponding to
QPO in oscillating
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tail (Abbott et al. 2007)
host galaxy of short GRB 050509
X-ray afterglow error circle
Association with an
elliptical galaxy at
z=0.225:
probable, but not certain
Subaru Prime Focus Camera (Kosugi, Takada, Furusawa, Kawai)
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Localization of GRB 050709
HETE Error Circle
HST Images at 4 Epochs
(Villasenor et al., 2005)
 HETE: Light Curve & Localization
Scale: 1” = 3 kpc
 Chandra: X-ray Error Circle
(Fox et al., 2005)
 Hubble: Fading Optical Counterpart
Redshift z=0.160
news on short GRB?
• GRB 090510
– Fermi LAT detected many GeV photons
(GCN 9334, 9340)
– Swift X-ray afterglow -- good position
•  host redshift z=0.903(GCN9353)
 Eiso=4x1052 erg
Strong beaming
x100 unseen (off beam axis) short GRB!
• many more target events for GW!
• no regular “GRB”: how to identify?
– may have delayed X-ray/optical afterglow
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Lessons from 40 years’ GRB study
• Location, location, location
• Be open-minded
• Be prompt
• Be prepared
• Get help
• Be cooperative
Discovery
(Klebesadel et al. 1973)
• Unexpected, but …
– destined to be discovered if even a small gammaray detector is placed in orbit for months
– new observing window  discovery
• cf. first X-ray source (1962), though few-minute rocket
flight was sufficient for finding Sco X-1
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Mystery for ¼ century (1973-1997)
• No idea on distance
– farther than Jupiter, based on TOA triangulation
• No association to objects of known class
– intrinsic difficulty of localization in gamma-ray
– transient, short lived
– (similar difficulty awaiting for GW!)
• Red herring: Galactic neutron star?
– X-ray bursts (thermonuclear flash on NS, discovered in 1972)
– Giant flare on 5 March 1979 (GRB 970305)
– Cyclotron lines (independent reports)
12
Insights in the dark age
• Santa Cruz meeting 1984
(Woosley, Lamb, Fenimore, …)
– Priority: location good enough for counterpart search
– Mission concept (High Energy Transient Experiment)
• HETE re-started by Ricker in 1990
• If HETE was launched in 1980’s…?
• Relativistic jets in GRB (Epstein ’85)
– needed to overcome compactness problem
– radio afterglow predicted
• Origin at cosmological distances (Paczynski ’86)
– original arguments not strictly valid (hindsight)
– proposed test: isotropy
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Era of the great debate (1992-1997)
• Explosion of population in the field
– Santa Cruz Taos Huntsville
• CGRO/BATSE:
– Isotropy increasingly more evident
– non-Euclidean (<V/Vmax>, log N-log S, …)
• Light curve, energy spectra
– bursts with a long pause
– duration vs. flux, spectral hardness vs. flux, …
• “No-host problem” for IPN locations
• implied high-redshift (z>1) difficult to believe
• theoretical frameworks in place
– Fireball scenario, relativistic shells, “failed SN”,…
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Afterglow Era (1997-2004)
• HETE lost due to launch failure (Nov. 1996)
• “All-Sky X-Ray Observations of the Next Decade”,
RIKEN, Wako, Japan, 3-5 March 1997.
– X-ray afterglow announced by Piro
• BeppoSAX breakthrough
–
–
–
–
–
Optical transients (ground and HST)
First redshift: GRB 970508 (z=0.8)
High redshift: GRB 971214 (z=3.4)
SN 1998bw/GRB 980425 association???
Optical flash: GRB 990123 (z=1.6)
(Bacodine+BeppoSAX+ROTSE III)
– Link to formation of massive stars
• hosts, location, …
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Discovery of X-ray afterglow (1997)
gamma-ray trigger (GRBM)
NFI
ground analysis of X-ray data
from Wide Field Camera (WFC)
WFC
GRBM
commanding satellite to point
X-ray telescope (Narrow field
instrument) to GRB location
2-8 hours
1997 Feb 28
Costa et al. 1997
8 hours
1997 Mar 3
3 days
cf. “triangulation” using multiple
spacecrafts took weeks to obtain
location
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Discovery of optical afterglow (1997)
van Paradijs et al. 1997
• association to distant
galaxies
• absorption spectrum in
afterglow  redshift
• power-law (~t-1) decay
consistent with
cosmological model
HETE-2 (2000-2005) and Swift (2004-)
• 1st dedicated GRB
satellite
• Rapid localization
– 1 arcmin in 40 sec
– enable early followup
– established GRB-SN
connection
– Wide band
spectroscopy of prompt
emission
• Autonomous slew
to GRB
– highly sensitive BAT
• 100 GRBs/yr
• high-z and short GRB
– afterglow obs. with
XRT and UVOT
• arcsec position in a
few minutes
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GRB network
Gamma-Ray Burst
alert
GRB satellites
(Swift, AGILE,
Fermi)
TDRS
response <1-10 min
Ground Station
Internet
Observatories
notification in ~10s
Mission ops center
GCN (gamma-ray
burst coordinate
network)
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EM counterpart search of GW event
• Purpose
– obtain good location for
• quiescent counterpart search (host galaxy, cluster, SNR, …)
• Trigger more sensitive follow-up
• Measurements: light curve, spectra, …
• prompt emission
– Requirements
• instantaneous wide field
coverage (> str)
• arcmin localization
• high sensitivity
– Waveband
– optical, X-ray
– (gamma-ray)
• Early afterglow
– Requirements
• Rapid response
• higher sensitivity
– Waveband
– optical, X-ray
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GW detection/Localization
• accuracy?
• 10 deg – special wide-field instrument
• 1 deg – wide-field telescope
• arcmin – normal telescope
• how rapid?
• How long for intercontinental triangulation
• incremental refinement with time
• directional bias? (accuracy, detection frequency)
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missions/facilities
• Wide field (prompt/simultaneous)
–
–
–
–
–
HE gamma-ray: Fermi
Hard X-ray: Swift EXIST
soft X-ray: (MAXI) (needed)
optical/NIR: (some) (needed)
radio:
LOFAR
SKA?
• Rapid follow up (afterglow)
–
–
–
–
–
gamma-ray: (Fermi, INTEGRAL)
Hard X-ray: (Swift) EXIST
soft X-ray: (XMM, RXTE) need big one
optical/NIR: many ground, (Swift/UVOT) EXIST/NIRT
radio:
LOFAR, ALMA?
SKA?
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Monitor of All-sky X-ray Image (X-ray All-Sky Monitor on the ISS)
carried to ISS by STS-127 on June 13, 2009
Kibo
ISS motion
MAXI Operation
5 Sigma Limit
1 orbit
20 mCrab
1 day
2 mCrab
1 week
1 mCrab
6 months
0.2 mCrab
(Source Confusion Limit)
• Monitor >90% of sky every 90 min
• instantaneous coverage: 2% of sky
• x10 sensitivity over RXTE ASM
• Energy range: 0.5-30 keV
• >2 years mission life (5 yr or more likely)
Sensitive WF monitor needed
• wide-field X-ray monitor
– sensitivity: ~10 mCrab/10 s
(modest for focusing instrument)
– field of view
tens of X-ray
concentrator
• ~10 deg to cover Virgo cluster
• ~1 steradian to cover significant
fraction of the sky
– Need technology in X-ray optics
• Wide-field optical monitor
– modest technology
e.g. hundred 10cm Schmidt
telescopes in space
DIOS
4-stage X-ray mirror
2.5 deg FoV
• Dedicated satellite
– e.g. “Virgo watcher”
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Conclusions
• We should prepare for unexpected GW
transients of new class
• Localization and EM counterpart search is
essential (…25 years of failure for GRB)
• Rapid & accurate localization of GW transient
• Need sensitive wide field monitor
– X-ray : XRT sensitivity with BAT field of view
– optical: 100 small Schmidt telescopes in space
• Big facilities (space or ground) should have
rapid response capabilities
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