neutrinos as probes of gamma-ray bursts
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Neutrinos as probes of gamma-ray bursts. Hylke Koers. Service de physique théorique, UL Brussels. Based on work in collaboration with: Ralph Wijers (API Amsterdam) Asaf Pe’er (Giacconi fellow, Hubble Space Telescope Science Institute) - PowerPoint PPT PresentationTRANSCRIPT
Hylke Koers, Service de Physique Théorique, UL Brussels
Neutrinos as probes ofgamma-ray bursts
Hylke Koers
Based on work in collaboration with:Ralph Wijers (API Amsterdam)Asaf Pe’er (Giacconi fellow, Hubble Space Telescope Science Institute)Dimitrios Giannios (Max-Planck-Institute for Astrophysics Garching)
Service de physique théorique, UL Brussels
Hylke Koers, Service de Physique Théorique, UL Brussels
Outline
Fireball neutrino cooling
Neutrino production in np collisions
Neutrino emission from choked GRBs
A gamma-ray burst primer
Hylke Koers, Service de Physique Théorique, UL Brussels
Motivation
Interesting for modelling: unresolved observations and extreme properties
Candidate sources of cosmic rays
Candidate sources of neutrinos
Probes of the universe up to z ~ 5, constraining DM and DE
Speculative ideas: constraining Lorentz invariance through arrival times, ... (?)
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: observational landmarks
Some observational landmarks:
’60s: Discovery of very energetic flashes of gamma rays. (military VELA satellites) – distance scale?
>1991: Isotropic distribution found (BATSE all-sky monitor from CGRO)
1997: Afterglow observations establish cosmological scales (BeppoSAX satellite)
1998: First identification of a contemporaneous SN – GRB (BeppoSAX / BATSE)
2004: SWIFT satellite observes shallow decay phase, late
energetic flares, and other unexpected phenomena
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: prompt emission
Key features of the prompt emission
Irregular lightcurves:“if you’ve seen one GRB...”
Rapid varibility, up to 10-3 sec.
Duration from 10-2 s – 103 s, subdivided intolong GRBs (~20 sec) and short GRBs (~0.2 sec)
Non-thermal spectrum (broken power-law),peaking around ~250 keV; occasionally extending to very high energies (> GeV... TeV?)
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: afterglow
Key features of the afterglow
Broad-band spectrum over many decades inenergy (radio, optical/IR, X-ray)
Characteristic break energies compatible with synchrotron emission
Slowly declining (typically power-law) lightcurve(sometimes detectable up to years
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: the fireball model
Acceleratingphase(108 cm)
Fireball accelerates to relativistic velocities ~ 300by radiation pressure; stops due to energy constraints(baryonic load)
Initial phase(106.5 cm)
Catastrophic event: core-collapse of a massive star (long GRB): Formation of black hole + accretion disk system which launches a fireball
Interaction with external environment: afterglowAfterglowphase (1016 cm)
Coastingphase (1012 cm)
Energy dissipation (shock acceleration):gamma-ray burst
[Cavallo & Rees 1978; Paczynski 1986; Mészáros & Rees 1992, 1993]
Key featuresTotal energy ~ 1052 erg
Lorentz factors ~ 300Collimation
Small baryonic load
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: open questions
Neutrinos are expected to be very useful probes to gain insight in these issues!
A GRB primer: open questions
Hylke Koers, Service de Physique Theorique, UL Brussels
Important (partly) unsolved questions:
How are the jets formed?
What is the nature of the outflow?Dominated by thermal energy (=fireball?)or by electromagnetic energy?
How is shock-acceleration realized?
Hylke Koers, Service de Physique Théorique, UL Brussels
A GRB primer: open questions
Hylke Koers, Service de Physique Théorique, UL Brussels
Outline
Fireball neutrino cooling
Neutrino production in np collisions
Neutrino emission from choked GRBs
Can neutrino cooling stop a developing GRB?[Koers & Wijers, MNRAS, 364, 934, 2005]
A gamma-ray burst primer
Hylke Koers, Service de Physique Théorique, UL Brussels
Fireball cooling: the fireball
fire· ball [‘fIr-”bol]: A tightly coupled plasma of photons, electron-positron pairs and neutrinos(with a small baryonic load)
Environment Temperature: T ~ 1011 K (20 MeV) Electrons, positrons: ne ~ 1035 cm-3
Baryons: nB ~ 1032 cm-3
Neutrino physics dominated by leptonic processes
DynamicsThe fireball expands by radiation pressure to relativistic velocities.
e±
pn
Hylke Koers, Service de Physique Théorique, UL Brussels
Fireball cooling: neutrino phase diagram
[HK & Wijers 2005]
rapid cooling
The fireball is transparant in regions of fast neutrino creation. Here neutrinos just follow the usual hydrodynamic evolution.
Roughly 30% of the initial energy is released as a burst of ~60 MeV neutrinos
Hylke Koers, Service de Physique Théorique, UL Brussels
Outline
Can we use neutrinos (or gamma rays) from nucleonic collisions to discriminate between models?[Koers & Giannios, A&A, 471, 395, 2007]
Fireball neutrino cooling
Neutrino production in np collisions
Neutrino emission from choked GRBs
A gamma-ray burst primer
Hylke Koers, Service de Physique Théorique, UL Brussels
NP decoupling: characteristic radii
Accelerating phase Coasting phase
Fireball model:
AC (magnetic) model:
Hylke Koers, Service de Physique Théorique, UL Brussels
NP decoupling: neutrinos and gamma rays
fluence fromburst at z=0.1
peak energy
AC modelFireball (FB) model
Both fluence and energy are below IceCube sensitivity!
prompt GRB(internal shocks)
np gamma rays(fireball only!)
~100 keV ~10 GeV
Hylke Koers, Service de Physique Théorique, UL Brussels
Outline
Can neutrino emission indicate the existenceof choked GRBs?[Koers & Wijers, arXiv: 0711.4791]
Fireball neutrino cooling
Neutrino production in np collisions
Neutrino emission from choked GRBs
A gamma-ray burst primer
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRBs: model
Motivation:Observed SN – GRB connection
Missing ingredient in SN modelling Ubiquity of astrophysical jets
Hypothesis: suppose that a (large) fraction of supernovae is accompanied by GRB-like outflows that stops below the surface [Mészáros & Waxman 2002]
No gamma-ray emission Potential source of neutrinos
(largely unconstrained)
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRBs: protons
Proton energy losses
Synchrotron radiation Photopion ...
Proton shock acceleration
[Razzaque, Mészáros & Waxman 2003, 2004, 2005; Ando & Beacom 2005]
Scheme: accelerate protons, create mesons,decay to neutrinos
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRBs: protons
Maximum energy (in jet frame)
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRB: mesons
Cooling break
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRB: mesons
Cooling break
Maximum energy(in jet frame)
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRBs: neutrino spectrum
Neutrino spectrum from meson (and muon) decay:
cooling break maximum energy
(at Earth)
Strong increase in high-energy neutrinos!
Hylke Koers, Service de Physique Théorique, UL Brussels
Choked GRBs: detection prospects
NB: optimistic case ofefficient meson injection
Hylke Koers, Service de Physique Théorique, UL Brussels
Conclusions
Neutrino emission is an interesting and promising way to probe the physics of GRBs.
However it remains a challenging task to identify concrete realizations of this potential.