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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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.