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Gamma-Ray Bursts

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

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Gamma-Ray Bursts

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  1. Gamma-Ray Bursts as a prototype of multi-messenger/time-domain astronomy,and the lessons we learned from unexpected discovery Nobuyuki Kawai (Tokyo Tech)

  2. 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

  3. Short GRB error boxes at nearby galaxies Andromeda Galaxy (2.5 million light years) M81/M82 Galaxy (12 million light years) Abbot et al. 2008, arXiv:0711.1163v2 Frederiks et al. 2007, arXiv:astro-ph/0609544v3

  4. short GRB070201 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? Abbot et al. 2008, arXiv:0711.1163v2

  5. Giant Flares of SGR (Soft Gamma Repeater ) 8.1s SGR0520-66 (5 Mar 1979) • Intense spike(<0.5s) contains most of radiated energy (1044-1046 erg) • followed by spin-modulated oscillation SGR1900+14 (27 Aug 1998) • slow X-ray pulsar in quiescence • Gal. plane or LMC: young NS • Implied magnetic field 1014-1015 gauss (“magnetar”) sec SGR1806-20 (27 Dec 2004)

  6. Giant Flare of SGR 1806-20 Terasawa et al. 2005 Neutron Star CEMs MCP X-ray counts • Magnetic energy (>1046 erg) released in 0.1 s • crust fracture? • No GW detected corresponding to QPO in oscillating tail (Abbott et al. 2007) Outer Core Magnetic Field

  7. host galaxy of short GRB 050509 Association with an elliptical galaxy at z=0.225: probable, but not certain X-ray afterglow error circle Subaru Prime Focus Camera (Kosugi, Takada, Furusawa, Kawai)

  8. HETE: Light Curve & Localization • Chandra: X-ray Error Circle Localization of GRB 050709 HETE Error Circle HST Images at 4 Epochs (Villasenor et al., 2005) Scale: 1” = 3 kpc (Fox et al., 2005) • Hubble: Fading Optical Counterpart Redshift z=0.160

  9. 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

  10. 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, …

  16. Discovery of X-ray afterglow (1997) gamma-ray trigger (GRBM) NFI ground analysis of X-ray datafrom Wide Field Camera (WFC) WFC GRBM commanding satellite to pointX-ray telescope (Narrow field instrument) to GRB location 2-8 hours cf. “triangulation” using multiple spacecrafts took weeks to obtain location 1997 Feb 28 1997 Mar 3 3 days 8 hours Costa et al. 1997

  17. 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

  18. 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 • 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. (7) Internet GRB network Gamma-Ray Burst alert GRB satellites (Swift, AGILE, Fermi) TDRS response <1-10 min Ground Station Observatories notification in ~10s Mission ops center GCN (gamma-ray burst coordinate network)

  20. 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, … • 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)

  21. 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)

  22. 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?

  23. Kibo ISS motion 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 • 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)

  24. Sensitive WF monitor needed tens of X-ray concentrator • 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 technologye.g. hundred 10cm Schmidt telescopes in space • Dedicated satellite • e.g. “Virgo watcher” DIOS 4-stage X-ray mirror 2.5 deg FoV

  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

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