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

and strategies

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

and strategiesCherenkov 200527-29 April 2005 Palaiseau, France

Elisa Bernardinibernardi@ifh.de

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?

http://icecube.wisc.edu

2/12

The AMANDA Detection principles

Up Down

~109 events/

year

~103 events/

yearA few events/

year

Neutrino candidates

are selected up-going muon tracks, with good angular

resolution

Muons detected

from Cherenkov light in ice

Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris 3/12

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)

On-Source

Off-Source

4/12

Search for clusters of events in the Northern skyThe data sample:3369 neutrino candidatesEvent selection optimized for both dN/dE ~ E-2 and E-3 spectra

Point Sources search:Search for excesses of events compared to the background from:• A set of selected candidate sources• The full Northern Sky

Declination averaged sensitivity, integrated in energy (E>10 GeV),

dN/dE ~ E-2 :

lim 0.6·10-8 cm-2s-1

= 2.25°-3.75°

= 807 days

3329 observed3438 expected atm. MC

5/12

Search for clusters of events in the Northern sky

Source Nr. of events

(4 years)

Expected

backgr.(4

years)

Flux Upper Limit

90%(E>10 GeV)

[10-8cm-2s-1]

Markarian 421

6 5.58 0.68

1ES1959+650

5 3.71 0.38

SS433 2 4.50 0.21

Cygnus X-3 6 5.04 0.77

Cygnus X-1 4 5.21 0.40

Crab Nebula 10 5.36 1.25

Selected objects and full scan of the northern sky:

No statistically significant effect observed

… out of 33 Sources

Systematic uncertainties under investigation

Crab Nebula: The chance

probability of such an excess

(or higher) given the number of trials is 64%

Sensitivity ~2for 200 days of “high-state” and spectral results from HEGRA

Preliminary

Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris 6/12IMAGE CREDIT: NASA/Honeywell Max Q Digital Group, Dana Berry

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

7/12

1. Look at known periods (active states)

Source EM light curve source

Livetime in periods of

high activity

Nr. of events in

high state

Expected backgr. in high state

Markarian 421

ASM/RXTE 141 days 0 1.63

1ES1959+650 ASM/RXTE 283 days 2 1.59

Cygnus X-3 Ryle Telesc. 114 days 2 1.37

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

8/12

2. Search for neutrino flares

Source Nr. of events

(4 years)

Expectedbackgr.

(4 years)

Period duration

Nr. of doublets

Probability for highest multiplicity

Markarian 421 6 5.58 40 days 0 Close to 1

1ES1959+650 5 3.71 40 days 1 0.34

3EG J1227+4302 6 4.37 40 days 1 0.43

QSO 0235+164 6 5.04 40 days 1 0.52

Cygnus X-3 6 5.04 20 days 0 Close to 1

GRS 1915+105 6 4.76 20 days 1 0.32

GRO J0422+32 5 5.12 20 days 0 Close to 1

Search for excesses in time-sliding windows:No statistical significant effect observed

Preliminary

= 2.25°-3.75°

… out of 12 Sources

= 40/20 days for Extragalactic/Galactic Objects

events

time

sliding window

9/12

“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

backgroundper 40 days

Yellow bars: width of

sliding search window

PreliminaryTriangles: event times

10/12

Red lines:AMANDA – 2.25o search bin

Probability of a random coincidence with the “orphan flare” or the enhanced -ray activity undefined: a-posteriori hypothesis relative to the test

“Orphan flare”(MJD 52429)

11/12

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/-ray time correlation: what is the “frequency” of

orphan flares (bias from X-ray triggered -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

12/12

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

Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris 13/12

Neutrino Astrophysics :The new “Era” -- IceCube

14/12

The IceCube Project

Design:4800 Optical Modules80 strings (@ 125 meters)Depth: ~ 1400-2400 m Extensive Air Shower Array @ surface: IceTopInstrumented volume: 1 km3

Installation: 2005-2010, started!

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 projectExtensive technological development (e.g. digital readout) Optimized for energies > TeV

15/12

SS433: Observational hints of hadronic acceleration from -spectral linesPromising neutrino source candidate

galactic

Analogy Quasar / Microquasar:

extra-galactic

16/12

Search for flares: MethodSearch for excesses of events in sliding time windows of fixed

size (t):Method: Compare observed and background events in t.In what follows is shown how to:

1. Select the data sample: use the 4 years data sample (807 days)

2. 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 t >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 spectraare shown.

2. Choose the window size:

• Detection probability not “too-low”• Limited dependence on flare duration

Consideration from multi-wavelength observations:• Tflare(galactic) < Tflare(extragalactic)

(**) 40 d: Extragalactic / 20 d Galactic sources

17/12

Neutrino-Production and Propagation

Most models:• Neutrinos produced in hadron-hadron (pp) and hadron-photon (p)

interactions followed by meson decay, with different energy yields.

1.A

2.A

• Hadron spectrum at the source is expected to show a power-law shape (Fermi acceleration) power law spectrum for neutrinos

Flavor ratio (case 1 and 2):

e : : ~ 1:2:<10-5 @ the source

e : : ~ 1:1:1 @ the detector Pro

pag

ati

on

Sp

ectr

um

0

....

pnp

e

pp

e

Pro

du

cti

on

Neutrinos from neutron decay emerge with much lower

multiplicity and energy.

18/12

The AMANDA medium

Absorption

dust

ice

Scattering

bubbles

dust

Optical properties:Data from calibration light sources deployed along the strings and from cosmic rays.

Absorption length

@ 400 nm

Eff. Scattering length

@ 400 nm

110 m 20 m

Noise Rate from Optical Modules

< 1.5 kHz

A stable OMs sub-set

operates as “SuperNova

Watch”AMANDA

contributes to SNEWS

Effective scattering coefficientAbsorption length

On average:

19/12

cos

Aeff

/ km

2

Effective Area vs. zenith angle after rejection of background from downgoing atmospheric Muons.

Angular resolution (point source analysis), but using standard AMANDA reconstruction and selection procedures (improvement from fullWaveform information)

20/12

PeVcascade events: capability to separate vertex cascade and decay (“double bang” signature) above several PeV.

2 x 1019 eV event in AMANDA and IceCube:

21/12

~300 Optical Modules built

2 Optical Modules per

tank

27 January 200527 January 2005First IceCube stringFirst IceCube string

(“string 21”) (“string 21”) successfully successfully

deployeddeployed60 Optical Modules in 60 Optical Modules in

IceIce8 IceTop tanks

installed

HV board

DOM main board

Penetrator

Mu-metal cageOptical Gel

22/12

http://veritas.sao.arizona.edu/VERITAS_whipple_science.html

Markarian 421 Spectral Energy Distribution

Had

ron

icLep

ton

ic

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: leptonic versus hadronic models.

Neutrinos provide the only unambiguous way to discriminate scenarios.

Proton Blazar models:simultaneous production!

23/12

First IceCube events

An almost vertical event:12 IceTop DOMs hit (out of 16)30 IceCube DOMs hit (out of 36) powered at the timeDirection reconstruction of the showerfrom IceTop hitsDirection reconstruction including IceCube: different slope due to light delay (scattering)

24/12

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

Filtering/Fit Event Selection

P.Rate

7.14 billion events

L1 Hit & Optical Module selection Two fast first-guess reconstructions (*): Direct-Walk JAMS

ZenithDW>70o

1

3.7%

L2Cross-talk hit-filterUp-going Likelihood (UL) reconstruction (**)

ZenithJAMS>80o

0.39%0.39%

L3Topological parameters calculation

Hits distributions along the tracksSingle track angular resolution

ZenithUL>80o 0.11%

Down-going Likelihood (DL) reconstruction (**)

7.85 million muon tracks

25/12

Source Total Nr.Events

TotalBackgr

.

Period duratio

n

Nr. of doublet

s

Probability for highest significanc

e

Markarian 421 6 5.58 40 days 0 Close to 1

1ES1959+650 5 3.71 40 days 1 0.34

3EG J1227+4302 6 4.37 40 days 1 0.43

3EG J0450+1105 6 4.67 40 days 1 0.47

QSO 0235+164 6 5.04 40 days 1 0.52

QSO 0528+134 4 4.98 40 days 0 Close to 1

Cygnus X-3 6 5.04 20 days 0 Close to 1

Cygnus X-1 4 5.21 20 days 0 Close to 1

GRS 1915+105 6 4.76 20 days 1 0.32

GRO J0422+32 5 5.12 20 days 0 Close to 1

3EG J1828+1928 3 3.32 20 days 0 Close to 1

3EG J1928+1733 7 5.01 20 days 1 0.35

26/12

27/12

Results from the multi-wavelength campaign

(a) Whipple and HEGRA

(b-c) X-ray(d-f) optical(g-h) radioApJ 601, 151 (2004)

Unique observation of a high flux -rays flare without

corresponding X-ray counterpart