High-energy gamma-ray and neutrino emission from the microquasar LSI +61 303

Gustavo E. Romero, Instituto Argentino de Radioastronomía (IAR)

Department of Astronomy and Geophysics, University of La Plata, Argentina

Mariana OrellanaInstituto Argentino de Radioastronomía (IAR)

Department of Astronomy and Geophysics, University of La Plata, Argentina

LSI +61 303

Primary star B0VCompact object ? Distance 2 kpcPorb 26.5 d e 0.72 ± 0.15

β apar ≥ 0.4Phase of periastron 0.23

Paredes, J.M. [astroph:0501576]

3EG J0241+6103 ?

Orbital parameters: Casares et al. 2005

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m M

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i et

al.

20

03

Massi et al. 2004

MAGIC detection of LSI +61 303

MAGIC detection of LSI +61 303

Albert et al. 2006

MAGIC detection of LSI +61 303

Up-dated SED

Sidoli et al. 2006

Gamma-ray emission from MQs:Models Leptonic (Aharonian & Atoyan 1999; Bosch-Ramon et al. 2005, 2006; Dermer & Boettcher 2006, Bednarek 2006) Hadronic (Romero et al. 2003, 2005; Aharonian et al. 2006)In microquasars with high-mass stars, the stellar wind can provide a matter

field for interactions with relativistic protons from the jet

Pure leptonic channels also result from the decay of secondary particles

Secondary leptons

Model: interactions between relativistic protons from the jet and cold protons form the wind

Romero, G.E. et al 2003, A&A, 410, L1

Spherically symmetric wind

Circular orbit

Orbital phases for LS I +61 303

Massi 2004

Evolution of some parameters with the orbital phase

with n=3.2 (Gregory & Neish 2002).

Accretion rate onto the compact object

The model is dependent on the accretion rate and hence instrinsically time dependent

Some assumptions

• Magnetic field is determined from equipartition with the kinetic energy of the jet, hence it is phase dependent.

• Protons are accelerated by shocks in the inner jet to a power law of index p. Radiative losses are negligible so size constraints impose the upper limit on the proton energy.

• There is a phenomenological “mixing factor” which accounts for the fraction of relativistic protons that interact with cold protons (typically fm~0.1).

Main parameters for the model

Photon-photon absorption due to the star

Dubus 2006

Photon-photon absorption

Total photon-photon absorption

Light curve @ 200 GeV

Spectral energy distribution at different phases

Cascades close to the periastron passage

qj=1

Synchroton emission from secondary pairs

Neutrino emission

The estimated neutrino flux from LS I +61 303 on Earth is 4-5 muon-type neutrinos per km-squared per year (Christinasen, Orellana & Romero 2006). It could be detectable by IceCube .

1400 m

2400 m

Ice top

Southern Hemisphere ICECUBE

Conclusions

Jet models where the jet power depends on a variable accretion rate will produce variable gamma-ray emission.

In the case of LS I +61 303, opacity effects due to the radiation fields of the primary star and the circumstellar disk result in a maximum at ~0.5. This is independent of the gamma-ray production mechanism.

A hadronic model for the gamma-ray emission at high-energies cannot be ruled out by the current observations.

Future neutrino observations of LSI +61 303 could be crucial to establish the nature of the radiative mechanism in the source.