Gamma-rays, neutrinos and cosmic rays from microquasars Gustavo E. Romero (IAR – CONICET & La Plata University, Argentina) Grupo de Astrofísica Relativista y Radioastronomía (GARRA) Trondheim, June 2009

Microquasars Microquasars (MQs) are accreting binaries formed by a compact object and a donor star. The compact object can be a neutron star (e.g. as in Sco X-1) or a black hole (e.g. Cygnus X-1). The donor star can be of an early type or a low-mass star. MQs present non-thermal jets. This means that there are relativistic particles in the jets. In the environment of a MQ the presence of relativistic particles can result in the production of detectable gamma-rays and neutrinos (e.g. Levinson & Blandford 1996, Romero et al. 2003).

› Compact object › Donor star › Accretion disk › Hot corona › Relativistic jets Main components of a microquasar

 Low-hard  High-soft › › › Spectral states

MQs display different X-ray spectral states: - Low/hard state (a.k.a. power-law state). Compact radio jet. - High/soft state (a.k.a. thermal-dominant state). No radio emission. - Intermediate and very high states  transitions. Transient radio emission. (Fender 2001) MQs states and types of jets

SS433: a precessing microquasar with heavy jets  Jets with high kinetic power: L k =10 39 erg/s  Fe lines from detected from jets (Migliari et al. 2002)  Jets and extended disk wind in precession (P prec =162 d)  Potential neutrino source (Eichler 1980, Reynoso et al. 2008) VLBA

Evidence for relativistic hadrons in MQ jets Migliari et al. 2002; Kotani 1994, 1996 Migliari et al SS433

a cartoon…

Relativistic particles in the jets  Local magnetic field:  Shock acceleration of electrons and protons Rate: Power in relativistic particles:  One-zone approximation (e.g. Khangulyan et al. 2007) Acceleration zone z0z0z0z0 Jet BH and Injection function: ( GeV -1 cm -3 s -1 sr -1 ) L rel is a fraction q rel of kinetic power

Content of relativistic particles Initial magnetic field Simple model Compact acceleration/emission region located where the field falls below equipartition Mildly relativistic outflow, G =1.5 Conical jet, perpendicular to binary orbit Viewing angle q=30º, moderate Falcke & Biermann (1995) Körding et al. (2006)

Particle distributions  “one-zone” approximation diffusive shock acceleration ~ 2.2 ( Khangulyan et al. 2007)

Interaction of relativistic p and e - with magnetic field radiation fields in the jet Synchrotron radiation Inverse Compton (IC) Photohadronic interactions (pg) Proton-proton inelastic collisions p + p  p + p + a  0 + b(  + +  - ) The proton microquasr jet model (Romero & Vila, A&A 485, 623 (2008), also Romero & Vila, A&A, ) The proton microquasr jet model (Romero & Vila, A&A 485, 623 (2008), also Romero & Vila, A&A, 494, L33 (2009) )

Particle losses

Proton escape  Protons with energies beyond 1PeV can be produced.  Main losses for protons are synchrotron but locally produced energetic neutrons can escape:  Then, the neutrons decay outside the region of high magnetic field injecting protons, electrons and anti-neutrinos

Case of SS 433 Reynoso, Romero & Christiansen, MNRAS 387, 1747, 2008

Romero & Vila, A&A, 494, L33 (2009)

Magnetic field effects on neutrino production Reynoso & Romero A&A, 493, 1 (2009)

Charged pions and muon distributions

Magnetic field effects on neutrino production Reynoso & Romero A&A, 493, 1 (2009)

SS 433: Differential Neutrino flux at Earth

SS 433: Integrated neutrino flux Here, q rel = 10 -3

Gamma-ray absorption in MQs  γ-rays can be absorbed by:  Optical depth Differential optical depth Reynoso et al. APh, 28, 565 (2008)

Gamma-ray absorption in SS433: Absorption due to γγ interactions  Target photons from the star :  Differential optical depth (Gould & Schreder 1967) with T ✹ =8500 K for SS433 with T ✹ =8500 K for SS433  Target photons from the extended disk  UV emission: Black body with T= K, (10 3 Å < λ <10 4 Å) R UV = 33 R ✹ (Gies et al. 2002) R UV = 33 R ✹ (Gies et al. 2002)  IR emission:, (2µm < λ <12 µm) R IR = 50 R ✹ (Fuchs et al. 2005) R IR = 50 R ✹ (Fuchs et al. 2005)

γγ absorption γγ absorption Starlight contribution Gamma-ray absorption in SS433:

γγ absorption γγ absorption Contribution due to IR emission Contribution due to UV emission Gamma-ray absorption in SS433:

Absorption due to γN interactions  Optical depth Cross section Density of the star : Density of the extended disk : absorption Gamma-ray absorption in SS433:

γN optical depth Gamma-ray absorption in SS433:

Total optical depth For γ-rays originated at jet base Gamma-ray absorption in SS433:

Effects on a gamma signal Gamma-ray absorption in SS433:

Integrated gamma-ray fluxes for SS 433

Positrons are copiously produced by internal absorption and charged muon decays INTEGRAL results (Weidenspointener et al., Nature 451, 159 (2008) Annihilation line distribution LMXRBs distribution Models with a=100 produces around positrons/s

Lepto/hadronic models for LMXRB (Vila & Romero, in preparation) GX 339-4

PAMELA positron fraction

Final comments  The consistency of the models presented can be tested with present and future neutrino and gamma-ray observations.  MQs can be sources of comic rays up to energies of the order of the knee.  MQs can also be an important source of positrons in the Galaxy  A more realistic treatment is necessary to refine predictions: e.g. go beyond the one-zone approximation.

Thank you!

Parameters of the model for SS433