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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3

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