X-Ray Binaries as Gamma-Ray Sources Binary systems of a compact object (neutron star or black hole) and a stellar companion Matter is flowing over from the stellar companion onto the compact object. Angular momentum conservation => Formation of an accretion disk Matter in the accretion disk heats up to ~ 106 K => X-ray emission

X-Ray Binaries (cont.) As in most accretion disk systems, this results in the formation of collimated outflows: Mildly relativistic jets: G ~ 2 Generally identified as radio jets X-ray binary spectra typically consist of a thermal disk component plus a hard power-law.

X-Ray Emission from Microquasar Jets(?) Markoff et al. (2005)

g-Ray Emission from Microquasar Jets LS 5039: H.E.S.S. (Aharonian et al. 2005)

g-Ray Emission from Microquasar Jets LS I +61o 303: MAGIC (Albert et al. 2006) → Analogy to blazars!?

High-Energy Emission Model for Microquasar Jets Synchrotron emission Relativistic jet outflow with G ≈ 2 Injection, acceleration of ultrarelativistic electrons nFn n Compton emission g-q Qe (g,t) g1 g2 g Leptonic Models nFn Injection over finite length near the base of the jet. n Seed photons: Synchrotron (SSC), Accr. Disk + BLR (EC) Additional contribution from gg absorption along the jet → Include abs. by companion star light! + Companion star light

Microquasar Jet Model for LS 5039 Problems with GeV – TeV spectral shape → EGRET (GeV) source may not be associated with LS 5039 Bosch-Ramon et al. (2005) Böttcher & Dermer (2005) Dermer & Böttcher (2006) Gupta et al. (2006)

Orbital Modulation in LS I +61 303 MAGIC (> 400 GeV) Radio (15 GHz) Albert et al. (2006)

Fit to LSI +61o303 Orbital modulation of VHE g-rays can be explained by gg absorption alone!