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Transcript
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 6 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) 7 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 9 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 11 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 13 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”,… 14 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, … 15 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 16 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 18 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) 19 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 20 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 • 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? 22 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” 24 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 25