GW from GRBs Gravitational Radiation from Gamma-Ray Bursts Tsvi Piran Racah Inst. of Jerusalem, Israel Dafne Guetta,, Ehud Nakar, Reem Sari
Once or twice a day we see a burst of low energy gamma-rays from the outer space lasting for a few seconds. The energy released during a burst (~10 51 erg within a few seconds) is only a few orders of magnitude below the energy released by the rest of the Universe at the same time! GRBs are the (electromagnetically) brightest objects in the Universe. Only ~8 orders of magnitude less then the theoretically maximal * luminosity (c 5 /G)~10 59 erg/sec. * Up to relativistic corrections. 2 Mc GM / c 3
bad GRBs are good for many thing: Determining the high redshift history of the universe? Destroy Life on Earth (mass extinction)?? Creat Life on Earth (trigger planet formation)? Measuring quantum gravity effects?
GRBs are good for many thing: Determining the high redshift history of the universe? Destroy Life on Earth (mass extinction)?? Creat Life on Earth (trigger planet formation)? Measuring quantum gravity effects? Accompany sources of Gravitational Radiation (Kochanek & Piran, 1993).
Observations The Fireball Model OUTLINE Gravitational Radiation from GRBs Sources Rates Digression to Lorentz Invariance Violation (time permitting) Conclusions and prospects
THE DISCOVERY GRBs were discovered accidentally by Klebesadal Strong and Olson in 1967 using the Vela satellites (defense satellites sent to monitor the outer space treaty). The discovery was reported for the first time only in 1973. There was an invited prediction Colgate (1967) predicted GRBs from (galactic) supernovae.
Properties Duration 0.01-1000s Two populations (long and short) ~10-2000keV photons (non n thermal spectrum) (very high energy tail, up to GeV, 500GeV?) Rapid variability (less than 10ms)
The Internal-External Fireball Model γ-rays Afterglow Inner Engine Relativistic Outflow Internal Shocks External Shock 10 6 cm 10 13-10 15 cm 10 16-10 18 cm
ATERGLOW The bursts are followed by multiwavelength afterglow: X-ray, radio, Optical BeppoSAX
Duration ~30 sec accretion time scale. Variability 0.1 sec fluctuation time scale. Short lived accretion disk
Routes to a short BH-Disk-Jet NS/BH-NS merger BH-WD merger NS/BH-He core merger Collapsar - LONG - SHORT Long Davies et al, 94 Woosley et al, 99
Long Duration GRBs: Massive Stars & Sne GRB host galaxies are star- forming galaxies High column density/extincted extincted bursts In regions of very high star formation (Fruchter( Fruchter). Association with type Ibc SNe But SNe are not seen in some GRBs? 011030 990123 990712 990123
Rates of Long Bursts The observed rates of long BAT GRBs is 1 per day on BATSE (20-300KeV, 0.25 photons/cm2/sec, 1/3 sky coverage) An observed burst per galaxy in 2 107 years 3 105 years/galaxy with a beaming correction of ~50 This rate is a factor of >1000 below the rate of SNe. Does not follow the SFR requires more distant bursts! UVOT XRT
~ 1/3 of BATSE long bursts. ~1/10 of Swift long bursts. Lower total energy and weaker afterflows. Short Bursts
Are Short GRB Extragalactic HyperGiantFlares from SGRs? NO! Nakar, GalYam, TP, Fox, 05?
Host of GRB 060724 Keck/LGSAO/Narrow Camera K band Evidence for an old population Red elliptical z=0.258 L=1.6 L* SFR<0.03 M yr-1 GRB 050813 Kulkarni & Cameron GRB 050709 From Nakar, Gal Yam & Fox 05
Rates of Short GRBs Rate from the observed redshifts Too few known Dominated by unknown selection effects Rate from the flux distribution Ambiguity Rate from Fluxes + Check with the redshift distribution
Rates from Fluxes N(>F) Number of bursts with flux >F { n(z) Rate as a function of z φ(l) Luminosity function
Rates from Flux N ( > F ) =! 0 Z max ( L, F, p) dz n( z)! 0 " dl #( L) Number of bursts with flux >F Rate as a function of z Luminosity function Maximal redshift for detection of a burst with a luminosity L given the detector s s sensitivity p.
Guetta Tsvi Piran & TAU TP March 05a,b 07
? X? X X?? X X XX A comparison with Swift short bursts (Guetta & Piran,, 06) Does not follow the SFR Need more nearby bursts
From Nakar, Gal Yam & Fox 05
Time lag p(τ) probability for a time lag τ TP 92, Ando 2004
Within the context of NS mergers expect p(τ) 1/ 1/τ (TP 92)
Intermediate Short Long Selection effects? Guetta & Piran 05
Typical Delays:
Two populations???
Luminosity function and Rates ~10 /Gpc 3 /yr 80 mergers /Myr/ Galaxy* *Assuming a beaming factor of 30 Comparable to the estimated rate of mergers (e.g( Kalogera 04) L*~2 10 50 erg/sec
Luminosity function and Rates Weakly constrained by current detectors L*~2 10 50 erg/sec ~10 4 /Gpc 3 /yr 8 10 4 mergers /Myr/ Galaxy Nakar, Gal-Yam, Fox 05, See also Tanvir 05
80 Myr/Galaxy 20 (0.5) events/yr within 200Mpc 10 5 Myr/Galaxy 20 (1) events/yr within 40Mpc 1 out of 30 in coincidence with a (short) GRB!
Gravitational Radiation from jet acceleration? Regardless of the nature of the inner engine the fireball model predicts gravitational radiation from the acceleration of ~10 51 ergs to relativistic velocity (Piran, 00). γ-rays Acceleration to Γ>>1 within δt Acceleration to Γ>>1 γ-rays 33
No Coincidence between this Gravitational Radiation and the GRB Gravitational waves γ-rays Acceleration to Γ>>1 Afterglow Afterglow γ-rays Acceleration to Γ>>1 Gravitational waves 34
Summary Long GRBs are associated with powerful SNe (hypernovae)) and produce GW. Rate LGRB <1000 Rate SNe unimportant for GW detection. Short bursts NS-NS or NS-BH mergers. Rate SGRB > 20 events/year up to 200 Mpc Rate SGRB Note uncertainty in the beaming factor (30). A much higher rate is possible but is highly uncertain. GRB coincidences enhance the significance of GW detection but only 1 in 30 events. The canonical GRB mechanism itself is not a likely source of detectable GW emission.