Damien Dornic, VLVNT08

Individual GRB sensitivity of the

cubic-kilometre deep-sea neutrino

telescope KM3NeT

Damien Dornic(CPPM/Marseille)

VLVNT08 - 23/04/2008

Damien Dornic, VLVNT08

Gamma ray bursts

…Powerful (among the most luminous sources in the Universe, up to Lγ~1052 erg/s) and highly variable (between few 10 ms to few minutes) sources of gamma rays that indicate the existence of cosmic particle accelerators

Detection: - detected first by X-ray satellites - then follow with OT

- others instruments (cherenkov telescope, neutrino telescope …)

Damien Dornic, VLVNT08

• Neutrino telescopes are well adapted to study prompt emission mechanisms: – Continuous data taking

– Special trigger based on GCN alert with a low threshold…

Neutrinos detection from GRBs

Time constrain+

Positionning~ Background free

Damien Dornic, VLVNT08

Prompt emission spectra

[D.Band et al, Astrophys. J. 413, 281 (1993)][D.Guetta et al, Astropart. Phys. 20, 429 (2004)]

Ep = 720 keV

= -0.6

= -3.1

Characteristic parameters of γ-spectra: - photon fluence - photon break Energy Eb

- low-energy spectral coefficient α - high-energy spectral coefficient β

Band function

Large parameters variability from burst to burst

All GRB photon-spectra described using a broken power-law

Damien Dornic, VLVNT08

“Fire ball” phenomenology

Prompt gamma ray (GRB it self) is due to the synchrotron radiation of electron acceleration by DSA in the internal shocks in the jet

Then, interaction with ISM → afterglow

Damien Dornic, VLVNT08

• Hadronic models suppose that protons are accelerated along with electrons ( mainly by Fermi acceleration)

→ With a power law spectrum with an index equal to -2

• We suppose also an equipartition of the energy between electrons (or photons) and protons

Neutrino production

• Shock-accelerated proton can directly interact with synchrotron gamma-ray photon (few 10 keV – MeV) in the fireball wind→ High energy neutrino (few 10 TeV – PeV)

)()( npEEif thpcm

ee

Damien Dornic, VLVNT08

Muon neutrino spectrum

90

2

10ln8 T

fF

dE

dNE

e

21

1

1

bb

b

b

EE

E

E

bEif

bb Eif

bEif

bb

: Neutrino break energy

: Pion synchrotron break energy

: Photon fluence (erg.cm-2)

: Proton efficiencyF

f: Burst duration90T

To determine the neutrino flux, the redshift is needed

Damien Dornic, VLVNT08

SWIFT data (from dec 2004 to yesterday):

297 GRBs detected by SWIFT

only 112 with a measured redshift

only 58 visible as up-going event in Antares site

Application to SWIFT data

Damien Dornic, VLVNT08

First step: determine the γ-spectrum parameters– BAT measures energy only between 15 and 150 keV

– We need to extrapolate to higher energy (→ MeV) using the knowledge of BATSE

• Used a fixed β index :

• Energy break: 100 and 800 keV

• Corrected the γ-ray fluence

– Propagate all instrumental and from the estimation errors

Gamma ray spectrum

7.03.03.2

GRB071227 → z = 0.383 → Fγ = 2.2 10-7 erg.cm-2

→ T90 = 1.8s

Maximum spectrum

Minimum spectrum

Damien Dornic, VLVNT08

Neutrino spectrum

GRB071227 → z = 0.383 → Fγ = 2.2 10-7 erg.cm-2

→ T90 = 1.8 s → Lγ = 9.83 1049 erg/s → Γ = 125 +/- 30 → fπ = 0.22

GRB080411 → z = 1.03 → Fγ = 2.63 10-5 erg.cm-2

→ T90 = 56 s → Lγ = 2.81 1051 erg/s → Γ = 228 +/- 30 → fπ = 0.34 {0.1-1}

Atmospheric neutrino: Volkova & al

Damien Dornic, VLVNT08

Event rate for a km3 detector

90

,T EE

effevent

th

dtdEtEdE

dNtEAN

Number of events per GRB →

Eth: Threshold in energy (1-10 TeV)

Neutrino effective area, Aeff →

To take into account the atmospheric neutrino background:

- Punctual source

- Angular resolution: ~0.2°

Damien Dornic, VLVNT08

Event rate for a km3-scale detector

For the 58 GRBs with a redshift and visible as up-going in the ANTARES site

For individual burst : Event : ~ 5.10-3

Background: ~ 3 10-6

Signal Noise

Rate: ~3 GRBs/day → 0.5 GRB/ (Gpc3.yr)

With an error bar of ~ ±1 order of magnitude

Damien Dornic, VLVNT08

Criteria to detect an individual burst

Minimal fluence to detect a single GRB →24 .104~ cmergF

Hypothesis: for long GRB, the luminosity is ~ 1051 erg/s

Mean redshift between 1 and 3

Use a mean for all the others parameters

→ recalculate the gamma-ray fluence

Damien Dornic, VLVNT08

Criteria to detect an individual burst

SWIFT BATSE

Some GRBs passed the minimal fluence criteria: BATSE ~ 6 / 2704 SWIFT ~ 1 / 297 (GRB080319B)

For a standard GRB (Lγ ~ 1051 erg/s) → « Horizon of detection » ~ 150 Mpc

Minimal fluence to detect a single GRB →24 .104~ cmergF

Damien Dornic, VLVNT08

Summary

• Detection of even a small number of neutrinos correlating with GRBs can prove without ambiguity presence of hadronic acceleration to UHE

• It is surely possible to detect individually some GRBs with a km3-scale detector (with almost a background free search)

• Contribution to the neutrino diffuse flux (by meaning all the neutrino spectrum for all the detected bursts and corrected to the solid angle) → the result is near the WB prediction (taking into account the UHECR flux)

•All this work is consistent with previous study based on BATSE