1. April 1st, 2009SASS1 Gamma-Ray Bursts Aurélien Bouvier

2. SASS2 about me… If you pretend being interested in the stuff about me, I’ll click on the link below: Video - Name: Aurélien Bouvier - Nationality: bloody french - Position: slave for the Fermi team - Interest: jumping out of a perfectly functioning airplane

3. SASS3 Outline A bit of history… GRB observations up to year 2000 On the theory side… (as if I understood) Beginning of a new era: Swift-Fermi observations

4. SASS4 GRBs - Discovery (1967-1973) US Vela Nuclear test detection satellites

5. SASS5 GRB, tell me who you are… GRBs remained a complete mystery for almost 30 years ! More than 150 different theories: Magnetic flares Black Hole evaporation Anti-matter accretion Deflected AGN jet Magnetars, Soft Gamma-Ray Repeaters (SGRs) Mini BH devouring NS ….. message from the Aliens

6. SASS6 Compton Gamma-Ray Observatory (CGRO) CGRO launched in 1991(orbit above atmospheric absorption) BATSE (20 keV-1 MeV): extremely sensitive gamma-ray detector () extremely sensitive gamma-ray detector ( scintillator ) EGRET (20 MeV-30 GeV): Pair production detector Pair production detector looked at the whole sky looked at the whole sky GRB detection rate ~ 1 GRB/day GRB detection rate ~ 1 GRB/day thousands of GRBs detected over the whole mission thousands of GRBs detected over the whole mission

7. SASS7 BATSE results 2 populations of GRBs: Short-Hard / Long-Soft Bursts Burst durationHardness-duration diagram

8. SASS8 GRB lightcurve / spectrum Non thermal prompt emission Best spectral fit: smoothly joining broken power law Compactness problem: Emitting region optically thin if emitting material has Lorentz factor > 100 -> Ultrarelativistic outflow (fastest bulk flow in the universe) Briggs et al. 1999

9. SASS9 BATSE results Isotropic distribution: -> rules out most galactic model Galactic (SGRs in a halo surrounding our galaxy) Versus Extragalactic origin

10. SASS10 Galactic vs Cosmological origin BeppoSAX: GRB 970228 1st X-ray/Optical afterglows detected Host galaxy was identified at z ~ 0.7 ! GRBs are extragalactic !

11. SASS11 Consequence of cosmological origin of GRBs Tremendous isotropic-equivalent energy: 10 50 -10 54 ergs released in a short time scale only in the form of gamma-rays. (sun: 10 33 erg/sec; supernova: 10 51 ergs on a month time scale) GRBs have been observed up to z ~ 6.3 -> hope to use GRB as cosmological tool (similar as Type Ia supernovae)

12. SASS12 Evidence of a jet Energetic argument: the release of isotropic energy in the form of gamma-rays is a real theoretical nightmare Evidence of jet-like emission in the optical afterglow lightcurve (but not so widespread): Rate of GRBs ~ 1 GRB/galaxy/100,000 years

13. SASS13 High energy behavior Little is known about GRB emission above 10 MeV EGRET detected a handful of burst but statistics is quite poor to draw any paradigm from it GRB940217‏: 18 GeV photons detected up to 90 minutes after trigger

14. SASS14 Progenitors Long-Soft bursts: Collapsar model Death of a massive (> 40 Msun), rotating, low-metallicity star: Massive for a core- collapse forming a BH Rotating to drive a pair of jet along the rotation axis Rotating to drive a pair of jet along the rotation axis Low-metallicity to retain mass an angular momentum Low-metallicity to retain mass an angular momentum

15. SASS15 Evidence for the core collapse model Long-Soft Bursts located in star forming region (irregular galaxies, arms of spiral galaxies) were massive stars are always found Supernovae connection: Bump observed in the optical afterglow Connection with Type Ib/c (core-collapse supernovae)

16. SASS16 Progenitors Short-Hard Bursts: NS-NS (NS-BH) merger NS-NS (NS-BH) in a binary system will loose energy through gravitational waves NS-NS (NS-BH) in a binary system will loose energy through gravitational waves The 2 objects will get closer until tidal forces rip the NS apart and matter falls into a BH. The 2 objects will get closer until tidal forces rip the NS apart and matter falls into a BH. The process has ms timescale The process has ms timescale Evidence for the merger model are less striking: Afterglow localized outside older galaxies Good candidate for gravitational wave detection Other progenitor still possible (giant magnetar flares…)

17. SASS17 Fireball model Prompt outburst phase (gamma-ray/x-ray): internal shocks in the relativistic blast wave. Afterglow (x-ray, optical, radio): external shock of the cooling fireball with the surrounding medium. Note: this is independent of the type of progenitor Note 2: this is just the leading candidate (for good reasons?), many more are out there…

18. SASS18 What else are GRB useful for? GRB is one of the leading candidate for the production of Ultra-relativistic CR (>10 18 eV-10 20 eV)

19. SASS19 What’s now? Swift : Very fast X-ray/optical afterglow observations Short GRBs Detection of flares… Naked eye bursts: Peak magnitude ~ 5.8 TeV telescopes (Magic, Veritas, HESS…), gravitational wave interferometers (LIGO, LISA), Neutrino detectors (Amanda, ANTARES…)

20. SASS20 Fermi Fermi: CGRO big brother GBM (~BATSE): 10 keV-20 MeV LAT (~EGRET): 20 MeV- 300 GeV

21. SASS21 Fermi: GRB results 7 GRBs detected with the LAT instrument The big one: GRB 080916C Lots of >100 MeV emission Delayed high-energy emission No significant rising HE component Long high-energy extended emission (up to 23 min after onset) 8 keV – 260 keV 260 keV – 5 MeV LAT raw LAT > 100 MeV LAT > 1 GeV T0T0

22. SASS22 Some cool stuff this allows us to do… Constraint on minimum bulk Lorentz factor (from opacity argument):  min ~ 860 (+/-40) Quantum gravity: test for possible energy dependence of the speed of light 13.2 GeV photon detected 16.5 sec after trigger – Conservative lower limit on the quantum gravity mass (assuming linear energy scaling): M QG > (1.50 +/- 0.20) x 10 18 GeV/c 2 min M QG (GeV) 10 16 10 17 10 18 10 15 1.8x10 15 Pulsar (Kaaret 99) 0.9x10 16 1.8x10 17 7.2x10 17 4x10 16 GRB (Ellis 06) GRB (Boggs 04) AGN (Biller 98) AGN (Aharonian 08) GRB080916CPlanck mass 10 19 1.5x10 18 1.2x10 19

23. SASS23 Philosophical note Some studies show that Gamma-Ray Bursts might have been responsible for Mass Extinction of life on Earth ! And there’s still people telling me my research is useless !!! Well ok maybe it is… :)