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Alexander Kappes Extra-Galactic sources workshop 13.-16. Jan. 2009, Heidelberg Gamma ray burst detection with IceCube
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 2 Outline Neutrino detection & neutrino telescopes at the South Pole Where we stand Final best flux limits from AMANDA Current status of IceCube GRB analyses Future perspectives with IceCube Planned analyses Optical follow up
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Principle of neutrino detection infrequently, a cosmic neutrino crashes into an atom in the ice and produces a nuclear reaction muon travels kilometers in the ice muon νμνμ nuclear reaction blue (Cherenkov) light emitted optical sensors capture (and map) the light cascade
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 4 Detection channels Muons: track of hits good angular resolution (IceCube 1 TeV) rather poor energy resolution (IceCube factor ~3) Cascades: concentric hits (almost) no direction information sensitive to all flavors low background better energy resolution achievable
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IceCube and AMANDA at the South Pole South Pole new South Pole station IceCube lab Skiway IceCube surface area AMANDA surface area
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The AMANDA and IceCube neutrino telescopes IceCube: 2004-2005: 1 string 2005-2006: 8 strings 2006-2007: 13 strings 2007-2008: 18 strings 2008-2009: ≥15 strings AMANDA: 1995-2000 19 strings 677 modules IceTop: Air shower detector 160 ice-tanks in surface array Threshold ~300 TeV 1450 m 2450 m InIce: 80 strings each with 60 modules 17 m between modules 125 m between strings Currently deployed: 55 strings 3300 modules 118 IceTop tanks
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 7 Backgrounds: Atmospheric muons & neutrinos Significantly higher sensitivity for up-going ν High-purity (atmospheric) up-going neutrino sample after cuts Up-going: ν-induced muons Down-going: atm. muons Up-going: ν-induced muons Backgrounds: Down-going μ Atmospheric ν Data-MC comparison (IceCube 22-strings)
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 8 preliminary Pointing accuracy: the Moon shadow Moon shadow observed in first 3 months of IceCube 40-string data Validates pointing capabilities: Angular resolution: IceCube 22 < 1.5° IceCube 80 < 1° on-moonoff-moon difference
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 9 Neutrino flux predictions precursorpromptafterglow Neutrino from GRBs (all flavors) all SNe→BH GRBs only average fluxes → large burst-to-burst fluctuations Meszaros & Waxman Phys.Rev.Lett. 90:241103 (H progenitors) Waxman & Bahcall 1997 Phys.Rev.Lett. 78:2292 Murase & Nagataki 2005 Phys.Rev.D73:063002 (Baryon loading 100) Razzaque etal 2003 (supranova) Phys.Rev. D68:083001 (all GRBs have SNR shell) Waxman 2002 astro-ph/021135
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 10 GCN-satellite triggered searches profit from known time (+ direction for muons) low # events per burst expected ➞ burst stacking Untriggered “sliding window” searches possibly large population of “choked “ GRBs not visible in γ-rays sliding window (typically 1 and 100 s): Search methods On-time (blind)Off-time T0T0 prompt precursor (~100 s) wide window O (-1 h to +3 h) background time 1 evt 2 evt 1 evt
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 11 Best flux limits from AMANDA (final) Neutrino flux limits from GRBs (all flavors) Cascades sliding window 562 d livetime Muons triggered, 419 bursts Precursor: not all SNe→BH have choked jet Prompt: not all GRBs have precursor SN sensitivity reaches Waxman/Bahcall, Murase/Nagataki fluxes References: Muons: A. Achterberg etal, ApJ 674:357, 2008 Cascades: A. Achterberg etal, ApJ 664:397, 2007
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 12 IceCube 22-strings: neutrino flux calculations June 2007 - April 2008 41 satellite-triggered northern bursts (mainly Swift) with usable IceCube data Calculation of individual burst spectra (Waxman-Bahcall GRB flux based on BATSE bursts)
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 13 Unbinned likelihood method Input: position+uncertainty, time and energy estimator Search windows: prompt: γ-ray emission from satellites precursor: 100 s before prompt emission wide window: -1h to +3h Expected events (prompt): average WB ~0.7 individual spectra ~0.5 Unblinding of results soon IceCube 22-strings: muon analyses Discovery potential for average WB burst Effective muon neutrino area
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 14 IceCube: perspectives for stacked analyses Planned analyses: Muons: search for neutrinos from southern GRBs (reduced sensitivity; cross check with ANTARES) Cascades: triggered Prospects: Expect that IceCube 80-strings will be 3-4 times more sensitive than IceCube 22-strings With Fermi number of observed GRBs will be ~3 times larger (200-300 per year) IceCube will be able to detect Waxman-Bahcall or similar GRB fluxes within the next years
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 15 March 19, 06:12:49 UT (duration ~70 s) Position: RA = 217.9°, Dec = +36.3° Brightest (optical) GRB ever observed: z = 0.94 (D A = 1.6 Gpc) Large number of observations in γ-ray, X-ray and optical ➞ calculation of individual neutrino spectrum (fireball model) GRB 080319B: the “naked-eye” GRB Γ = 500 average WB GRB Γ = 1400 Neutrino spectrum GRB 080319B Γ = 300
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 16 GRB 080319B: IceCube analysis Detector was running in maintenance mode (9 out of 22 strings taking data) Expect 0.1 events for Γ = 300 No neutrino candidate near GRB position after cuts ➞ 90% upper flux limit (publication soon) Γ = 300 Would expect O (1) event from similar burst in IceCube 80-strings!
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 17 Model-independent GRB analysis Neutrinos might arrive significantly (up to hours?) earlier or later than prompt γ-ray emission Energy spectrum might be quite different than expected Only close spatial correlation with GRB guaranteed ➞ event weight Algorithm: Start with small time window Sum weights for events in window ➞ p-value Successively increase time window ➞ take best p-value (idea Nathan Whitehorn)
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 18 Toy MC 3 signal events injected Model-independent GRB analysis Toy MC studies: 10 Million AMANDA-like background events Several million time windows Trial factors only 5-10 for several hour time windows (windows strongly correlated) Application to IceCube data planned
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 19 Optical follow-up Potentially large fraction of core-collapse SNe has mildly relativistic jets that don’t emerge (no γ-ray signal) 30 neutrino events expected in IceCube for SN @ 10 Mpc (Ando & Beacom, PRL (2005), Razzaque, Meszaros & Waxman, PRL (2005)) Use IceCube coincidence to trigger optical follow-up angular window 4° time window 100 s significant increase in sensitivity with optical coincidence ~30 random doublets per year
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 20 Expected sensitivities (Ando & Beacom model): Optical follow-up active since several weeks (ROTSE) Optical follow-up
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Alexander Kappes, extra-Galactic sources workshop, Heidelberg Jan. 2009 21 Summary AMANDA sensitivity already constrains/touches neutrino flux predictions IceCube more than half-way completed (completion in 2011) Current IceCube GRB analyses: Upper limit on neutrino flux from GRB 080319B Analysis of IceCube 22-string data almost finished (triggered prompt + precursor + wide-window searches) With growing IceCube detector + Fermi/Swift good chances to identify first cosmic neutrino(s) Model dependent + independent searches Muon + cascade channel Optical follow-up observations Otherwise exclude Waxman-Bahcall by factor ~10
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