Multi-messenger studies of point sources using AMANDA/IceCube data and strategies

1. Multi-messenger studies of point sources using AMANDA/IceCube data and strategies Cherenkov 2005 27-29 April 2005 Palaiseau, France • Contents: • The AMANDA/IceCube detection principles • Search for High Energy neutrino point sources: • 4 years time-averaged signals • Transient (time-variable) signals • Observations of the Blazar 1ES1959+650 • Towards an extension of multi-wavelength • campaigns to neutrino observatories? Elisa Bernardini bernardi@ifh.de http://icecube.wisc.edu

2. The AMANDA Detection principles ~109 events/ year Up Down ~103 events/ year A few events/ year Neutrino candidates are selected up-going muon tracks, with good angular resolution Muons detected from Cherenkov light in ice

3. On-Source Off-Source Search for a neutrino signal from point sources:4 years time-averaged • ‘Blind-Analysis’: • Event selection and analysis procedures are optimized on • events with randomized right ascension and/or time • Background estimated from the data (off-source) Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris

4. Search for clusters of events in the Northern sky = 2.25°-3.75° = 807 days Declination averaged sensitivity, integrated in energy (E>10 GeV), dN/dE ~ E-2 : • Point Sources search: • Search for excesses of events compared to the background from: • A set of selected candidate sources • The fullNorthern Sky lim  0.6·10-8cm-2s-1 The data sample: 3369 neutrino candidates Event selection optimized for both dN/dE ~ E-2 and E-3 spectra 3329  observed 3438 expected atm. MC

5. Search for clusters of events in the Northern sky SensitivityFn/Fg~2 for 200 days of “high-state” and spectral results from HEGRA Crab Nebula: The chance probability of such an excess (or higher) given the number of trials is 64% Selected objects and full scan of the northern sky: No statistically significant effect observed Preliminary … out of 33 Sources Systematic uncertainties under investigation

6. Search for a neutrino signal from point sources:transient phenomena • ‘Enhance the detection chance by using the time information’: • Search for transient signals, still compatible with the • 4 years-averaged flux upper limits IMAGE CREDIT: NASA/Honeywell Max Q Digital Group, Dana Berry Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris

7. 1. Look at known periods (active states) • Search for events in coincidence with known periods of enhanced • electromagnetic emission: • Periods and sources selected on the basis of the available multi-wavelength information • Wavelengths investigated are possible indicators for a correlated neutrino emission (X-ray for Blazars and radio for Microquasars) Multi-wavelength information and theoretical knowledge of the time-correlation with the possible neutrino emission are meager: Search for neutrino flares without a-priori hypothesis on their time of occurrence

8. 2. Search for neutrino flares sliding window events = 40/20 days for Extragalactic/Galactic Objects = 2.25°-3.75° time Preliminary Search for excesses in time-sliding windows: No statistical significant effect observed … out of 12 Sources

9. Preliminary Triangles: event times Yellow bars: width of sliding search window “A posteriori”: 3 (of 5) events in 66 days Period of major outburst measured at different wavelengths in 2002 (and an “orphan flare”) Error bars: off-source background per 40 days

10. Red lines: AMANDA – 2.25o search bin “Orphan flare” (MJD 52429) Probability of a random coincidence with the “orphan flare” or the enhancedg-ray activityundefined: a-posteriori hypothesis relative to the test

11. Multi-messenger campaigns? • Overlap of interests between the high energy electromagnetic measurements and neutrino observations: • BL-Lac hadronic/mixed versus leptonic models: neutrino detection would discriminate scenarios  combined efforts may increase discovery potential • X-ray/g-ray time correlation: what is the “frequency” of orphan flares (bias from X-ray triggered g-ray observations?) • Does the “orphan-phenomenology” represent a “class” of cosmic accelerators or is it rather unique? • Data taking coordination: • Long-term monitoring of the electromagnetic emission of this source and similar (light curves and spectral information) • Target of opportunity triggered by AMANDA/IceCube on-line event filtering? • Data analysis coordination: • Identify common interests and guidelines for possible information exchange policy

12. Summary • No statistically significant effect observed in the search for point sources of neutrino with 4 years of AMANDA data • Observations of the Blazar 1ES1959+650 in coincidence with the “orphan flare”: no conclusive answers possible whether the observed events can be ascribed to the source or are accidental  future observations could shed light on the nature of the source emission (electromagnetic/hadronic) • The results from the point source analysis motivate new search strategies in AMANDA and IceCube • A collaboration between the multi-wavelength community and neutrino observatories could be of mutual benefit • A few “viable” scenarios have been mentioned: • Data taking coordination • Data analysis coordination

13. Neutrino Astrophysics : The new “Era” -- IceCube Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris

14. The IceCube Project • A km3-size detector at the South Pole: • Goals: • Sensitivity to look for neutrinos from AGNs, GRBs … • Study the “knee” region of the cosmic ray spectrum • … • AMANDA as Pilot project • Extensive technological development (e.g. digital readout) • Optimized for energies > TeV Design: 4800 Optical Modules 80 strings (@ 125 meters) Depth: ~ 1400-2400 m Extensive Air Shower Array @ surface: IceTop Instrumented volume: 1 km3 Installation: 2005-2010, started!

15. Analogy Quasar / Microquasar: SS433: Observational hints of hadronic acceleration from a-spectral lines Promising neutrino source candidate extra-galactic galactic

16. Search for n flares: Method • 2. Choose the window size: • Detection probability not “too-low” • Limited dependence on flare duration • Consideration from multi-wavelength observations: • Tflare(galactic) < Tflare(extragalactic) • Search for excesses of events in sliding time windows of fixed size (Dt): • Method: Compare observed and background events in Dt. • In what follows is shown how to: • Select the data sample: use the 4 years data sample (807 days) • Select the search window size (time duration): 40 d/ 20 d (**)  Depend on signal strength, spectrum and duration (unknown!) Constraints from steady point sources search results: • Upper limit: Flares of duration Dt >100 days are almost excluxed • Lower limit:Sensitivity ratio flares 10-day / 4-years: ~ 3 • Photon flux ratio flare/no-flare state: O(10) from multi-wavelength observations 1. Choose the data sample: Standard sample (3329 events): livetime ~ 800 days (0.04 = 32 d) Flare sample (~ 8000 events): different signal energy spectra are shown. • (**) 40 d: Extragalactic / 20 d Galactic sources

17. Neutrino-Production and Propagation • Most models: • Neutrinos produced in hadron-hadron (pp) and hadron-photon (pg) interactions followed by meson decay, with different energy yields. • A • A • Hadron spectrum at the source is expected to show a power-law • shape (Fermi acceleration)  power law spectrum for neutrinos • Neutrinos from neutron decay emerge with much lower multiplicity and energy. Production Spectrum Flavor ratio (case 1 and 2): e : m:  ~ 1:2:<10-5@ the source e : m:  ~ 1:1:1 @ the detector Propagation

18. The AMANDA medium Scattering Absorption ice bubbles dust dust Optical properties: Data from calibration light sources deployed along the strings and from cosmic rays. Effective scattering coefficient Absorption length A stable OMs sub-set operates as “SuperNova Watch” AMANDA contributes to SNEWS On average:

19. mAeff / km2 cos  Angular resolution (point source analysis), but using standard AMANDA reconstruction and selection procedures (improvement from full Waveform information) Effective Area vs. zenith angle after rejection of background from downgoing atmospheric Muons.

20. 2 x 1019 eV event in AMANDA and IceCube: PeV nt cascade events: capability to separate vertex cascade and t decay (“double bang” signature) above several PeV.

21. Penetrator HV board DOM main board 27 January 2005 First IceCube string (“string 21”) successfully deployed 60 Optical Modules in Ice ~300 Optical Modules built Optical Gel Mu-metal cage 8 IceTop tanks installed 2 Optical Modules per tank

22. A reference example: Blazars (Active Galactic Nuclei) Emission: Low energy (from radio up to UV / X-ray): non-coherent synchrotron radiation. High energy (up to TeV) under debate:leptonicversushadronicmodels. Neutrinos provide the only unambiguous way to discriminate scenarios. Proton Blazar models: simultaneous n production! Hadronic Markarian 421 Spectral Energy Distribution Leptonic http://veritas.sao.arizona.edu/VERITAS_whipple_science.html

23. First IceCube events An almost vertical event: 12 IceTop DOMs hit (out of 16) 30 IceCube DOMs hit (out of 36) powered at the time Direction reconstruction of the shower from IceTop hits Direction reconstruction including IceCube: different slope due to light delay (scattering)

24. Data filtering and event reconstruction 00-03 (*) “Moderate” CPU-time consumptive ~ 10-3 s/events for a 2.5 GHz CPU (**) Intensively CPU-time consumptive, up to ~ 1 s/events, First guess results as “seeds”, 32 iterations for up-going, 64 for down-going hypothesis

27. Unique observation of a high fluxg-rays flare without corresponding X-ray counterpart Results from the multi-wavelength campaign (a) Whipple and HEGRA (b-c) X-ray (d-f) optical (g-h) radio ApJ 601, 151 (2004)