gamma-ray bursts as a prototype of multi- messenger/time-domain astronomy, and the lessons we...
TRANSCRIPT
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
2
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”)
6
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
7
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
11
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
12
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)
13
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
14
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”,…
15
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)
16
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
19
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, …
20
• 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)
21
missions/facilities
22
• 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
24
• 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
25
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