gamma-ray bursts
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Gamma-Ray Bursts. as a prototype of multi-messenger/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 - PowerPoint PPT PresentationTRANSCRIPT
Gamma-Ray Bursts
as a prototype of multi-messenger/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
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Short GRB error boxes at nearby galaxiesShort GRB error boxes at nearby galaxies
Abbot et al. 2008, arXiv:0711.1163v2 Frederiks et al. 2007, arXiv:astro-ph/0609544v3
Andromeda Galaxy (2.5 million light years) M81/M82 Galaxy (12 million light years)
short GRB 070201• localized by IPN• No plausible
gravitational wave candidates within 180 s
• Exclude NS merger at <3.5 Mpc
magnetar flare!• chance
coincidence?
4Abbot et al. 2008, arXiv:0711.1163v2
Andromeda Galaxy (2.5 million light years)
Giant Flares of SGR (Soft Gamma Repeater )
•
5
SGR1806-20 (27 Dec 2004)
SGR0520-66 (5 Mar 1979)
sec
SGR1900+14 (27 Aug 1998)
8.1s• Intense spike (<0.5s) contains most of radiated energy (1044-1046 erg)
• followed by spin-modulated oscillation
• slow X-ray pulsar in quiescence
• Gal. plane or LMC: young NS
• Implied magnetic field 1014-1015 gauss (“magnetar”)
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Giant Flare of SGR 1806-20
Magnetic Field
Outer Core
CEMs MCP
X-r
ay c
ount
sNeutron Star
• Magnetic energy (>1046 erg) released in 0.1 s
• crust fracture? • No GW detected
corresponding to QPO in oscillating tail (Abbott et al. 2007)
Terasawa et al. 2005
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host galaxy of short GRB 050509
X-ray afterglow error circle
Subaru Prime Focus Camera (Kosugi, Takada, Furusawa, Kawai)
Association with an elliptical galaxy at z=0.225: probable, but not certain
Localization of GRB 050709
HETE: Light Curve & Localization
Redshift z=0.160
HST Images at 4 Epochs
(Fox et al., 2005)
Scale: 1” = 3 kpc
Hubble: Fading Optical
Counterpart
Chandra: X-ray Error Circle
(Villasenor et al., 2005)
HETE Error Circle
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 ergStrong beamingx100 unseen (off beam axis) short GRB!
• many more target events for GW!• no regular “GRB”: how to identify?
– may have delayed X-ray/optical afterglow9
Lessons from 40 years’ GRB study
• Location, location, location• Be open-minded• Be prompt• Be prepared• Get help• Be cooperative
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Discovery (Klebesadel et al. 1973)
• Unexpected, but …– destined to be discovered if even a small gamma-
ray 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)
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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, …
Discovery of X-ray afterglow (1997)
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gamma-ray trigger (GRBM)
WFC
NFI
GRBM
ground analysis of X-ray datafrom Wide Field Camera (WFC)
commanding satellite to pointX-ray telescope (Narrow field instrument) to GRB location
1997 Mar 31997 Feb 28
8 hours 3 daysCosta et al. 1997
2-8 hours
cf. “triangulation” using multiple spacecrafts took weeks to obtain location
Discovery of optical afterglow (1997)
• association to distant galaxies
• absorption spectrum in afterglow redshift
• power-law (~t-1) decay consistent with cosmological model
van Paradijs et al. 1997
HETE-2 (2000-2005) and Swift (2004-)
• 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 18
• 1st dedicated GRB satellite
• Rapid localization– 1 arcmin in 40 sec– enable early followup– established GRB-SN
connection– Wide band
spectroscopy of prompt emission
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Ground Station
Gamma-Ray Burst
Mission ops center
alert
GCN (gamma-ray burst coordinate network)
Internet
GRB satellites(Swift, AGILE, Fermi)
TDRS
GRB network
Observatories
notification in ~10s
response <1-10 min
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, …
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• Early afterglow– Requirements
• Rapid response• higher sensitivity
– Waveband– optical, X-ray
• prompt emission– Requirements
• instantaneous wide field coverage (> str)
• arcmin localization• high sensitivity
– Waveband– optical, X-ray– (gamma-ray)
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
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• 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?
Monitor of All-sky X-ray Image (X-ray All-Sky Monitor on the
ISS)
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)
carried to ISS by STS-127 on June 13, 2009
Sensitive WF monitor needed
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• wide-field X-ray monitor– sensitivity: ~10 mCrab/10 s
(modest for focusing instrument)– field of view
• ~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
• Dedicated satellite– e.g. “Virgo watcher”
DIOS4-stage X-ray mirror2.5 deg FoV
tens of X-rayconcentrator
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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