Combining Gamma and Neutrino Observations Christian Spiering, DESY

C. Spiering CTA Meeting Berlin May 4, 2006 Capabilities of Neutrino Telescopes AMANDA-II, ANTARES class –Effective area : TeV ~ TeV –Angular resolution AMANDA ~ 2.2° –Angular resolution ANTARES < 1° (Note: angle ( , ) ~ 1 TeV, 10 TeV ) IceCube –Ama + 9 strings (2007 configuration): ~ 2-3  AMANDA sensitivity –full array (2011) ~ 30  AMANDA sensitivity –angular resolution °

AMANDA (neutrinos) Sensitivity of Gamma ray telescopes IceCube (neutrinos) Sensitivity (2π sr, 100% ontime): Modified plot following Albrecht Karle TeV 3 years exposure, 5 sigma 90% U.L. AMANDA-II, ANTARES class –Sensitivity ~ / (cm² s) above 1 TeV IceCube –Sensitivity ~ / (cm² s) above 1 TeV

C. Spiering CTA Meeting Berlin May 4, 2006 AMANDA Sky events equatorial coordinates

C. Spiering CTA Meeting Berlin May 4, 2006 Significance Map equatorial coordinates AMANDA Highest significance: 3.4σ σ Compatible with statistical fluctuations of a smooth background of atmospheric neutrinos

C. Spiering CTA Meeting Berlin May 4, 2006 Reduce Trial Factor by Source Selection Five TeV-Blazars Seven GeV-Blazars Eight Microquasars Four SNRs Six other selected objects Three CR triplets TOTAL : 33 SOURCES

C. Spiering CTA Meeting Berlin May 4, 2006 Highest significance: CRAB Compatible with statistical fluctuation Adding year 2004 does not increase significance 33 tested sources Excess Probabilities

C. Spiering CTA Meeting Berlin May 4, 2006 Source stacking of gamma-selected AGN classes No excess for any of the classes  upper limits

C. Spiering CTA Meeting Berlin May 4, 2006 Transient Sources „Cluster Search“ Approach: Search for time clusters of events from directions of 12 sources which are known to flare „Flare Search“ Approach: For 4 sources: search for coincidences of events with observed high states of these sources  enhancement of signal/background ~ 1 neutrino/(search bin  year)

C. Spiering CTA Meeting Berlin May 4, 2006 A Curious Coincidence Year MayJuneJuly Flux of TeV photons (arb. units) WHIPPLE Arrival time of neutrinos from the direction of ES orphan flare

C. Spiering CTA Meeting Berlin May 4, 2006 Could that have been a „signal“ ? We cannot judge significance since defini- tion a for flare was „TeV gamma + X-ray“  orphan flare realized only a posteriori Exercise: –Assume a source with 1% flaring rate (The big unknown. Need long-term monitoring ! ) –3, one coinciding with a flare: P~0.03 –3, two coinciding with a flare:P~0.001 –3, three coinciding with a flare: P~ –(trial factor for multi-source analysis to be included) 2 neutrinos would correspond to a flux ~ 50 times higher than most models predict. Some models allow higher fluxes!

C. Spiering CTA Meeting Berlin May 4, 2006 Could that have been a „signal“ ?

C. Spiering CTA Meeting Berlin May 4, 2006 This Coincidence Triggered Many Ideas and Questions Need long-term monitoring in order to catch as many flares as possible Observation of coincidence can boost the significance considerably Significance is poorly quantifiable since the flaring rate is poorly known Need long-term monitoring also in order to better quantify flaring rate

C. Spiering CTA Meeting Berlin May 4, 2006 More … What do we call a flare ? (Threshold, duration,….) What are typical flare lengths ? (this defines reasonable coincidence windows) What is the relation between gamma and neutrino flux, and between typical gamma energies and neutrino energies ? Can neutrino telescopes trigger Cherenkov telescopes (ToO, Target of opportunity trigger) ?

C. Spiering CTA Meeting Berlin May 4, 2006 Small, dedicated telescopes for long-term monitoring –Better understanding of long-term behaviour of the sources –Get a larger statistics for orphan flares –Benefit for neutrino  gamma flare coincidences: long-term monitoring of time TeV energies allows better calculation of significances of coincidences. –Background reduction w. r. t. neutrino observation –Northern Site vs. Southern Site ? –Distributed vs. Single Site ?

C. Spiering CTA Meeting Berlin May 4, 2006 Target of Opportunity Trigger : The Idea Trigger gamma telescopes by neutrinos Alternative trigger to X-ray trigger Advantage: „Hadronic Trigger“ Disadvantages: mostly atmospheric neutrinos (improves with angular resolution and, for hard spectra, energy threshold)

C. Spiering CTA Meeting Berlin May 4, 2006 Target of Opportunity Trigger: How might it work ? Select a few sources with flary behaviour Preferently, these sources should be those which the Gamma telescopes observe anyway from time to time If IceCube (AMANDA) detects a neutrino from one of the selected sources, it generates an alert (within ~20 minutes) A Gamma Telescope points to the source, if the source is in its FoV within, say, 24 h

C. Spiering CTA Meeting Berlin May 4, 2006 Target of Opportunity Trigger: Questions (1) How many false triggers due to atmospheric ? –AMANDA: search window 2-3°, ~2 atmospheric in 365 days –IceCube: search window ~1°, ~6 atmospheric in 365 days –For 5 selected sources and 30% probability that the Gamma telescope can point to the source within 24 h, this translates to 3 (AMANDA) and 9 (IceCube) „false“ observations per year. –IceCube: request 2 coincident ? This reduces background essentially to zero, but signal efficiency is also decreasing.

C. Spiering CTA Meeting Berlin May 4, 2006 Target of Opportunity Trigger: Questions (2) What are the signal expectations ? How can neutrino telecopes avoid to violate their blindness criteria ? Should we run a test with AMANDA ? –depends much on how we judge the ES1959 coincidence … –We should not create non-justified hopes –Good test for common campaigns, start to link communities

C. Spiering CTA Meeting Berlin May 4, 2006 Neutrinos would give strongest proof of hadronic contributions Knowledge of gamma flux variations can considerably increase the significance of neutrino observations Neutrino community would profit from long-term monitoring of selected, flaring sources Possibility of ToO trigger under investigation Initiate vigorous program on phenomenology of sources Summary

C. Spiering CTA Meeting Berlin May 4, 2006 Backup slides

C. Spiering CTA Meeting Berlin May 4, 2006 Possible Scheme for a ToO Trigger