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Cosmic Rays: what we do (not) know 95 years after the discovery Adrian Biland, ETH Zurich Graz, 29.Nov.2007 Graz, 29.Nov.2007 A.Biland: Cosmic Rays 1 - History - Direct CR Observations; ‘low’ Energy - Indirect CR Observations; ‘high’ Energy - Possible CR Sources & Accelerators Graz, 29.Nov.2007 A.Biland: Cosmic Rays 2 CR History 1896 Bequerel discovers Radioactivity (birth of Nuclear Physics) 1900 Wilson measures conductivity of air (postulates extraterr. radiation that ionizes air) 1910 . 1911 . Gockel shows that air in 4000m still conductive F.Zwicky postulates Supernovae as source of radiation (since few years, we know the ‘crazy swiss’ had been [partially] correct once more) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 3 CR History 1912 Hess measures height-dependency of conductivity => more ionization at high altitudes ==> can’t be terrestrial radiation ‘Birth of CRPhysics’ 1936 Nobel Prize Graz, 29.Nov.2007 A.Biland: Cosmic Rays 4 CR History 1919 1926 . 1927 . Kolhoerster: Energy > known radioact.Elem. Int. Physics Symposium accepts existence of ‘ultraradiation of unknown origin’ Clay: less radiation at aequator than at pole => must be affected by magnetic field => must be charged particles (*) 1930 Rossi: Air-showers; soft and hard component . (absorbed by 1cm Pb | penetrates 1m Pb) 1931 Dirac postulates e+ (from QED) 1932 Anderson identifies e+ in air showers ‘Birth of Particle Physics’ Graz, 29.Nov.2007 A.Biland: Cosmic Rays 5 (*) Clay indicated in 1926 that CR must be charged particles. But (at least in USA) dispute about charged particles vs. gamma-rays continued for many years Millikan vs. Compton ==> The New York Times headline in Dec. 1932: Graz, 29.Nov.2007 A.Biland: Cosmic Rays 6 CR History 1935 1937 . . 1938 . Yukawa postulates ‘Meson’ (m ~300me) Anderson & Neddermeyer find ‘Mesotron’ in showers (m ~50-1000me) (- 1947) can’t be Yukawa particle Auger detects ‘large showers’ >500m2 ==> Energy >1000 TeV (LHC: 14TeV) 1947 +- found in showers =>Yukawa part. . ==> Mesotron is new particle class: 1949 0 found in showers Graz, 29.Nov.2007 A.Biland: Cosmic Rays 7 ~ 40 km Primary cosmic particle ~ 15 km Atmosphere Air shower (secondary particles) ± ± o -> e+e- -> … Graz, 29.Nov.2007 A.Biland: Cosmic Rays 8 Since ~1950: - Accelerators ----> SM - Understanding of shower development (Monte Carlo) - Satellites ==> more Information about Primary cosmic Radiation: -Mainly p and charged Ions -Power law, but ‘knee’ ~1015eV and ‘ankle’ ~1018eV Energy range >12 decades Flux range >32 decades Graz, 29.Nov.2007 A.Biland: Cosmic Rays 9 Since ~1950: - Accelerators ---> SM - Understanding of shower development (Monte Carlo) - Satellites I(E) ~ E– ==> more Information about Primary cosmic Radiation: -Mainly p and charged Ions -Power law, but ‘knee’ ~1015eV and ‘ankle’ ~1018eV Energy range >12 decades Flux range >32 decades Graz, 29.Nov.2007 A.Biland: Cosmic Rays 10 ( History ) 1930: Pauli postulates 1956: Cowan & Reines find (Reactor) Since 1965: Davis searches for solar flux factor ~3 too low (Astro) 1987: first (only) extrasolar (extragalagtic) -source seen: SN-1987A (Astro) 1989: exist three generations <45GeVAcceler. 1998: -oszillation ==> -mass from air-shower !!! (CR !!!) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 11 - History - Direct CR Observations; ‘low’ Energy - Indirect CR Observations; ‘high’ Energy - Possible CR Sources & Accelerators Graz, 29.Nov.2007 A.Biland: Cosmic Rays 12 Direct CR Observation CR-particles with E < ~10TeV can (and should) be observed above atmosphere Direct observations Solar modulation Below 20 GeV: ‘solar modulation’ shielding by the (variable) solar wind and B-field must be taken into account Graz, 29.Nov.2007 A.Biland: Cosmic Rays 13 Effect of Solar Shielding measured proton flux above (south) pole compared to calculated flux outside Heliosphere Depending on solar activity, CR flux <20GeV can vary by more than 20% ==> difficult to compare measurements... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 14 CR Abundance Chemical composition of CR shows good agreement with ‘metal’ ratios in interplanetary matter [IPM] CR ~85% p ~12% He ~ 2% e~ 1% ‘metals’ ( E < 3GeV) even/odd structure: Binding Energy Large disagreement @ ‘solar system’ (IPM) Li, Be, B, F, ‘sub-Fe’ too much in CR or too few in IPM ? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 15 Abundance vs. Solar Activity Solar minimum integr. CR flux Solar maximum While total CR flux varies with solar activity, rel. abundance stays constant ==> difference not from solar modulation ... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 16 lifespan of a star with 25 solar masses: <107 y Graz, 29.Nov.2007 A.Biland: Cosmic Rays 17 Production of Heavy Elements Main fusion-processes in (heavy) stars: 4He 12C 14N 16O 20Ne 4He 23Na p 24Mg 16O +16O 28Si 4He 31P p 32S + e-,e+,,.. … 4p 3 4He 12C +2p 12C +4He 12C +12C Graz, 29.Nov.2007 No (major) process to produce Li,Be,B,F Suppressed in ‘standard’ matter Do CR-sources produce nonstandard matter? A.Biland: Cosmic Rays 18 Our Galaxy 1pc=3.26Ly <Bgal> ~3G p: 10GeV r ~ 10-5pc 1015eV r ~ rgal (low-energy) CR trapped in Galaxy ‘Rigidity’: momentum / charge [GV] particles with same rigidity follow same trajectory in B-field Interstellar Matter [ISM]: ISM ~ 1 1H/cm3 Graz, 29.Nov.2007 A.Biland: Cosmic Rays 19 Spallation CR does not travel in vacuum: e.g. 12C CR ‘primary’ + 1HISM 10B CR + ‘secondary’ X (X: p, 0, ++me+em) known cross-section (measured in lab): need ~6 g/cm2 ISM to be traversed to explain CR abundance (C/B ratio) ISM~ 2 10-24g/cm3 ==> CR travels ~3 1024cm ~1 Mpc Graz, 29.Nov.2007 A.Biland: Cosmic Rays 20 Propagation Model Goal: One model should explain all ratios, as well as antiproton- and positronrates and diffuse gamma-flux (0) Unknown details about our galaxy (exact ISM distribution, B-field, …) and CR-sources do automatically cancel if looking only at ratios !!! Graz, 29.Nov.2007 A.Biland: Cosmic Rays 21 Leaky Box Model Occurrence for each Isotope i at Energy E: Acceleration at Source(s) Energy dependent leaking out of magn. Bottle Isotope loss by: Collision | Radioact. with ISM | decay Isotope creation by Spallation or radioact. decay from Isotope k Higher Energy particles can escape B-field easier, i.e. average ‘age’ of high-energy CR lower less secondaries Graz, 29.Nov.2007 A.Biland: Cosmic Rays 22 ‘extended’ Models ‘Nested Leaky-Box’: Strong B-field close to sources CR must first leak-out source region (probably > ISM) ‘Reacceleration’: CR that is accelerated at sources does already contain secondaries from ‘older’ sources Graz, 29.Nov.2007 A.Biland: Cosmic Rays 23 ‘extended’ Models ‘Diffusion Model’: assume more physical escapemechanism than just ‘leakage’ predict (small) density gradients expect (small) anisotropies Others (E-loss by Ionisation, Radiation, …) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 24 B/C Ratio Reference fit, to be applied to other ratios Problems: -large experim. errors -disagreement between exp. ==> can not really test models Graz, 29.Nov.2007 A.Biland: Cosmic Rays 25 Calculated Abundances ~1GeV/Z no Li, Be, B at source >50% of C,O,Mg Si,... destroyed by spallation Graz, 29.Nov.2007 A.Biland: Cosmic Rays 26 Direct Measurement of CR Age Secondary Isotopes with lifetime ~esc can be used to directly measure the age of CR e.g.CR could stay for long time in regions with low ISM and high B ? need more precise measurements ... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 27 Some Actual Results excess ??? Positron Flux need more precise measurements ... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 28 Some Actual Results e+ and anti-p could also be produced in decays of (hypothetical) dark-matter particles; should result in different energy spectra than in CR predictions ==> need much more precise measurements ... [even if most CR physicists are more interested on the highest energy questions ... ] Graz, 29.Nov.2007 A.Biland: Cosmic Rays 29 Balloons (mainly in Antarctica) e.g.: BESS direct cosmic ray (since 1992, ~3d/year 100d/y planned) AMS@ISS (20XY) put particle physics detectors outside of the atmosphere Satellites: PAMELA (on russian Satellite; launch 15.June 2006) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 30 AMS-02 p-flux He-flux Predicted performance … Graz, 29.Nov.2007 A.Biland: Cosmic Rays 31 AMS-02 ==> search for new Physics Graz, 29.Nov.2007 A.Biland: Cosmic Rays 32 Differential Fluxes Heavy elements (Fe) should show harder spectrum than light elements (He, C) because of shorter interaction length Are high-energy CR dominated by Fe instead of H ? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 33 - History - Direct CR Observations; ‘low’ Energy - Indirect CR Observations; ‘high’ Energy - Possible CR Sources & Accelerators Graz, 29.Nov.2007 A.Biland: Cosmic Rays 34 Primary CR-Spectrum Above few 10 TeV: no longer possible to directly measure CR-particles: Flux too low ==> need too large detector CR-spectrum looks boring/feature-less except: Graz, 29.Nov.2007 A.Biland: Cosmic Rays 35 Primary CR-Spectrum ~ 20 events..? galactic ? extragalactic ? confined Graz, 29.Nov.2007 not confined by gal.B-field A.Biland: Cosmic Rays 36 ‘Air-Calorimeter’ Cannot use satellites or balloons to measure CR > 100 TeV: Use atmosphere as a ‘calorimeter’ Problems: - not constant density not constant temperature not constant composition (e.g. clouds) … (and everything varies with time) how to read it out ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 37 Atmosphere Total atmosphere ~ 1000 g/cm2 side remark: at 40km, still few g/cm2 left For detailed calculations, have to take into account some local temperature and pressure variations (e.g: winter/summer !) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 38 CR + Atmosphere ? produce mainly 0, +, - do full MC study, but: Graz, 29.Nov.2007 A.Biland: Cosmic Rays 39 0 in Atmosphere ? Decays immediately into 2, [ c=25.1nm ] producing electromagnetic (sub)showers pair-production Bremsstrahlung R~9/7 X0~45g/cm2 Graz, 29.Nov.2007 A.Biland: Cosmic Rays (in air, 20oC) 40 +- in Atmosphere ? decay: + --> + lifetime: c ~ 8m Mass: 0.13 GeV ==> 150 GeV +-: d=c=1150x8m ~9km ==> most would reach earth before decay but nuclear interaction (same as p or n) attenuation length in air: p,n ~120 g/cm2 +- ~160 g/cm2 ==> production of new p,n, +-0 Graz, 29.Nov.2007 A.Biland: Cosmic Rays 41 +- in Atmosphere ? Upper atmosphere ~isothermal ==> ‘depth’[g/cm2] ~ X e(-h/H) , H~6.5km ==> E+- >> 10 GeV: interaction before decay <~ 10 GeV: [ d < 600m ] decay before interaction ==> atmospheric , Graz, 29.Nov.2007 A.Biland: Cosmic Rays 42 +- in Atmosphere ? decay: + --> ee+ ==> atmospheric e lifetime: c ~ 600m Mass: 0.105GeV ==> 2 GeV +-: d=c=19x600m ~11km ==> reach earth before decaying energy-loss: (Ionization, …) loose ~ 2GeV in atmosphere (1000g/cm2) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 43 500 GeV Showers: Graz, 29.Nov.2007 A.Biland: Cosmic Rays 44 100 TeV Showers: (>1GeV) Graz, 29.Nov.2007 (>1GeV) A.Biland: Cosmic Rays 45 How to Readout ‘Calorimeter’ - Measure (at sea-level or underground) - Measure shower-tails (at high altitudes) - Ionization --> Recombination Fluorescence light - Shower-particles relativistic ==> emit Cherenkov light (300-700nm) - (sound waves; radio waves; … ???) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 46 atmospheric Best detectors: go to accelerator experim. also disadvantages: - not homogen. shielding (large access-shafts) - not homogen. inside (‘unneeded’ calorimeters) - … L3@LEP Graz, 29.Nov.2007 needed >10y to convince community to add cosmic-extensions A.Biland: Cosmic Rays 47 atmospheric Some results: -spectrum (includ. syst. errors) 10 Graz, 29.Nov.2007 102 103 p[GeV] A.Biland: Cosmic Rays 48 atmospheric Some results: compared with some nuclear interaction models predictions: Models or primary rate not correct ? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 49 atmospheric Some results: comparison with models predictions: (DELPHI) Similar results from L3+C & CosmoAleph Graz, 29.Nov.2007 All models fail to predict highest multiplicity events ?!?!? (assumption: all primary are Protons or Iron ) A.Biland: Cosmic Rays 50 Shower Tail: e.g. KASCADE Forschungszentrum Karlsruhe Graz, 29.Nov.2007 A.Biland: Cosmic Rays 51 KASCADE: array Graz, 29.Nov.2007 Liquid scintillator plus photmultiplier for e, Lead-absorber plus scintillator for A.Biland: Cosmic Rays 52 KASCADE some results Measured secondary flux vs. distance from shower center Graz, 29.Nov.2007 A.Biland: Cosmic Rays 53 KASCADE some results Unfolding of chemical composition for two nuclearinteraction models ==> disagreement Graz, 29.Nov.2007 A.Biland: Cosmic Rays 54 shower maximum p or Fe Primaries ??? Difficult to judge … Graz, 29.Nov.2007 A.Biland: Cosmic Rays 55 AGASA Similar principle as KASCADE, but much larger area (less dense sampling) ==> measure >>1015eV Graz, 29.Nov.2007 A.Biland: Cosmic Rays 56 GZK-cutoff ? Interaction of CR-protons with CMB: pUHE + CMB --> + --> p + 0 --> n + + Ethreshold ~ 1020 eV ~ 2x10-28 cm2 CMB ~ 400 cm-3 ==> must come from ‘near’ sources (few Mpc) 15 evts ??? (i.e. local cluster ???) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 57 Fly’s Eye / HiRes Completely different technique: Measure fluorescence of shower 1981-1993 shower particles ionize air ==> recombinat. ==> fluorescence light (emitted in all directions) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 58 Fly’s Eye / HiRes First proposal: 1967 Major improvement: stereo measurements Graz, 29.Nov.2007 A.Biland: Cosmic Rays 59 Fly’s Eye / HiRes HiRes does not confirm high trans-GZK flux observed by AGASA ?!!!!?!!! Could be, one of the observation techniques not well enough understood ???? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 60 AUGER (south) Hybrid: - 1600 water tanks (cherenkov) 1.5 km separation between neighbours 3000km2 Status Oct.2007 - 4x6 fluorescence telescopes Graz, 29.Nov.2007 A.Biland: Cosmic Rays 61 AUGER (south) One of 1600 ‘ground stations’ 3000 gallons water, 3 Photomultipl., Electronics shower particles hitting station: produce cherenkov light in water; signal incl. GPS-time transmit. to center ==> shower reconstruction Graz, 29.Nov.2007 A.Biland: Cosmic Rays 62 AUGER (south) One of 4x6 fluorescence telescopes: 440 Photomultipliers each 11m2 reflect. Graz, 29.Nov.2007 A.Biland: Cosmic Rays 63 AUGER (south) Science,9.11.07 black circles: all events >1018eV seen by AUGER (3o error) red stars: position of nearby AGNs (<200Mpc) ==> seem correlated ==> nearby AGNs could be sources of >1018eV particles ==> no problem with GZK Graz, 29.Nov.2007 A.Biland: Cosmic Rays 64 even larger ... Planned experiments: -Telescope Array TA (extend HiRes with ground stations similar to AUGER, but in north -AUGER North (3x larger than South) (similar to TA ... groups do not want to combine ... -EUSO (@ISS) search for fluorescence light from space huge area, but light-pollution problematic Graz, 29.Nov.2007 A.Biland: Cosmic Rays 65 EUSO Look from ISS to earth Catch Fluores.& Cherenkov light from showers Graz, 29.Nov.2007 A.Biland: Cosmic Rays 66 - History - Direct CR Observations; ‘low’ Energy - Indirect CR Observations; ‘high’ Energy - Possible CR Sources & Accelerators Graz, 29.Nov.2007 A.Biland: Cosmic Rays 67 Key Questions Location of sources: nearby (solar system) ? galactic? extragalactic? universal? Distribution of sources: - few bright point-like sources ? - many faint sources/ diffuse ? Type of sources: - astrophysical (“stars”,fields) ? - new physics (decay of heavy part.)? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 68 Main Problem charged particles are deflected by all kinds of magnetic fields ==> can not be traced back to their origin Graz, 29.Nov.2007 A.Biland: Cosmic Rays 69 Location of Sources From p+X --> 0+Y , 0 --> Search for with characteristic spectra (mainly at rather low energies...) ==> 1) ~same CR everywhere in our Galaxy ==> (probably) not local/solar origin 2) far less CR in LMC (Large Magellanic Cloud) ==> not extragalactic/universal origin Graz, 29.Nov.2007 A.Biland: Cosmic Rays 70 Location of Sources From magnetic field strengths: ==> [for GeV … TeV energies] 1) CR can enter/escape solar system ==> (probably) not solar origin 2) CR confined/shielded by galactic field ==> not extragalactic origin Graz, 29.Nov.2007 A.Biland: Cosmic Rays 71 Location of Sources Most probably, main component of CR has galactic origin (arguments not valid for highest energies: - low contribution to 0 production - can escape/enter galactic field ==> highest energy CR probably extragal.) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 72 CR Power Requirements Power needed to maintain galactic CR: CR Energy-density: ~1eV / cm3 CR age (@few GeV): ~107 years (CR density ~stable >108 years ) L = (Volume)*(E-density)/(lifetime) ~ (15kpc)2(200pc) * 1eVcm-3 / 107y ~ 5 1040 erg/s = 5 1033 J/s Graz, 29.Nov.2007 A.Biland: Cosmic Rays 73 Supernova (SN) Already 1911 (before Hess showed extraterrestrial origin !) Zwicky postulated SN as sources for CR ! Kinetic Energy emitted by typ-II SN: Typically, ~10Mo ejected, v~5 108 cm/s On average: 1 SN / 30 years in our Galaxy ==> LSN ~ 3 1042 erg/s = 3 1035 J/s ==> have to convert few% of kinetic SN Energy into CR-Energy (reasonable ?) (more than 99% of total SN Energy emitted in form of neutrinos ==> Astronomy?!) But SN do not accelerate to CR energies.. Graz, 29.Nov.2007 A.Biland: Cosmic Rays 74 Supernova Remnant (SNR) Models show that (type-II) Supernovae usually produce two shock waves; (shell-type SNR) Energy loss at outer shock: E1 = 2m(-v1v+v12) Energy gain at inner shock: E2 = 2m(v2v+v22) E=E1+E2=2m(v12+v22+v(v2-v1)) E/E ~ (v2+v1)/v Graz, 29.Nov.2007 A.Biland: Cosmic Rays 75 Supernova Remnant Shock waves from SN have typical lifetime ~ 1000y Energy gain per cycle: En+1=En(1+) Escape Probab. per cycle: P ===> spectral index ~ P/ ... ===> Supernova Remnants (SNR) seem excellent accelerators up to ~100 TeV (B-field ~0.1G ==> larmor radius too large...) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 76 Neutron Star / Pulsar Rotational Energy: Energy loss Erot ~ 1043 J (deceleration): E~ -0.3 1028J/s Lifetime: ~ 108 y #NS in Galaxy: n ~ 106 ==> total Energy emitted: nE ~ 1034J/s compare ECR ~ 5 1033J/s ==> NS could maintain CR (if acceleration!) (but Pulsars expected to emit this energy mainly by gravity waves..) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 77 Neutron Star / Pulsar Fast rotation, huge B-field (1012-1015G) If B tilted relative to ==> spinning B-field --> strong E-field max. value: E ~ 15 10 V/m i.e. charged particle can gain 1000TeV/m ! NS can transform Erot into Ekin … But: can CR escape NS region ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 78 Neutron Star / Pulsar Problem: huge B-field ==> Larmor-radius) r[km] = E[MeV] / 30*B[G] i.e. E = 100 TeV = 100 106 MeV B = 1012G r = 3 10-5km = 3mm !!! ==> particles can not escape ! (?) But: ‘polar cap’ and ‘outer gap’ models ... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 79 Binary Neutron Star (BNS) Macroscopic mass-flow from normal (or giant) star to companion Neutron Star Graz, 29.Nov.2007 A.Biland: Cosmic Rays 80 Binary Neutron Star Constant matter flux from star speeds up the rotation of Pulsar ->‘millisecond Pulsar’ Known to emit ~1031 J/s (per system) in X-ray If similar amount of Energy emitted in CR ==> few 100 Binaries could make major contribution to total CR Energy Graz, 29.Nov.2007 A.Biland: Cosmic Rays 81 Binary Neutron Star Energy gain in Binary system: Gravitational acceleration of proton: RNS E = -∫G mpMNS/r2 dr = G mpMNS/RNS Inf. ~ 70 MeV But mass flow >>1030 protons / second ==> huge total energy to be emitted ev. secondary acceleration in shockwaves? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 82 Pulsar Wind Nebula (PWN) Many Supernove remnants look not shell-type, but rather chaotic (e.g. Crab) Shell structure disturbed by outflow from central pulsar But shock waves still exist (or even enhanced) ==> PWN cosmic accelerators like SNR, but also possibility for additional processes at NS PWN from old pulsars could also collide with far away clouds ==> shock waves ==> acceleration Graz, 29.Nov.2007 A.Biland: Cosmic Rays 83 Starburst Regions (SB) Galactic regions with high gas density: ==> many new stars created locally ==> high star density ==> combined stellar wind ? ==> many heavy stars ==> many SN / Pulsars / Binaries ==> stronger CR flux than average ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 84 Active Galactic Nucleii (AGN) Mass flow into huge black hole (M~109m) in the center of a large galaxy (black hole in center of our galaxy: M~2.5 106m) Accretion disk and two jets observed in several AGNs (jets > megaparsec ! ) ‘Blazar’: jet pointing to observer Graz, 29.Nov.2007 A.Biland: Cosmic Rays 85 Starburst Galaxies Galaxies with very high star-forming rate (probably: high density/turbulent gas regions induced by recent galaxy-collision) ==> much higher CR flux, high leakage ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 86 Gamma Ray Bursts (GRB) -Very short flash of extremely high X-ray flux [highest energy phenomena since Big Bang...] -Observe: ~1 GRB/day -Extragalactic Origin many have huge redshifts One GRB class seems correlated with SN (---> Black Hole ?) Other models: - Neutron Star mergers; - Black Hole mergers; - … Enormous energy released, but not known if also able to accelerate to CR energies ... Graz, 29.Nov.2007 A.Biland: Cosmic Rays 87 Galaxy Clusters High density of (large) Galaxies ==> combined ‘Galactic Wind’ could form intense shock waves with IGM ==> high extragalactic CR flux ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 88 Cosmic Accelerators Problem: What is accelerating? But also: Why so little structure in CR spectrum ??? Graz, 29.Nov.2007 A.Biland: Cosmic Rays 89 Cosmic Accelerators Different classes of accelerators might act on completely different time scales: Typical values: GRB: AGN (flares): SNR: Neutron Stars/PWN: ~10-7 y (if accelerator) ~10-3 y ~103 y ~107 y (remind: CR flux featureless and ~stable since 108 y) (probably also different energy scales ....) Graz, 29.Nov.2007 A.Biland: Cosmic Rays 90 Conclusion • CR were (and still are) important tools to investigate physics at unprecedented energy • learned a lot about the physics of CR since their discovery • many important experiments going on • but still many open questions and much room for good peoples with brilliant ideas [ ?!!? entering ‘decade of astro-particle physics’ ?!!? ] Graz, 29.Nov.2007 A.Biland: Cosmic Rays 91