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 galaxies Abbot et al. 2008, arXiv: v2 Frederiks et al. 2007, arXiv:astro-ph/ v3 Andromeda Galaxy (2.5 million light years) M81/M82 Galaxy (12 million light years)

short GRB 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: v2 Andromeda Galaxy (2.5 million light years)

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

6 Giant Flare of SGR Magnetic Field Outer Core CEMs MCP X-ray counts Neutron Star Magnetic energy (>10 46 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 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  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 –Fermi LAT detected many GeV photons (GCN 9334, 9340) –Swift X-ray afterglow -- good position  host redshift z=0.903 (GCN9353)  E iso =4x10 52 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

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 ( ) 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 ) –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 ( ) Explosion of population in the field –Santa Cruz  Taos  Huntsville CGRO/BATSE: –Isotropy increasingly more evident –non-Euclidean (, 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 ( ) HETE lost due to launch failure (Nov. 1996) “All-Sky X-Ray Observations of the Next Decade”, RIKEN, Wako, Japan, 3-5 March –X-ray afterglow announced by Piro BeppoSAX breakthrough –Optical transients (ground and HST) –First redshift: GRB (z=0.8) –High redshift: GRB (z=3.4) –SN 1998bw/GRB association??? –Optical flash: GRB (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 data from Wide Field Camera (WFC) commanding satellite to point X-ray telescope (Narrow field instrument) to GRB location 1997 Mar Feb 28 8 hours 3 days Costa et al 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 ( ) 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 1 st 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 (7) 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:LOFARSKA? 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?

M onitor of A ll-sky X -ray I mage (X-ray All-Sky Monitor on the ISS) Kibo ISS motion MAXI Operation5 Sigma Limit 1 orbit20 mCrab 1 day2 mCrab 1 week1 mCrab 6 months0.2 mCrab (Source Confusion Limit) Monitor >90% of sky every 90 min instantaneous coverage: 2% of sky x10 sensitivity over RXTE ASM Energy range: 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” DIOS 4-stage X-ray mirror 2.5 deg FoV tens of X-ray concentrator

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