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.)

Generally identified as radio jets

As in most accretion disk systems, this results in the formation of collimated outflows:

Mildly relativistic jets: ~ 2

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)

Ray Emission from Microquasar Jets

LS 5039: H.E.S.S. (Aharonian et al. 2005)

Ray Emission from Microquasar Jets

→ Analogy to blazars!?

LS I +61o 303: MAGIC (Albert et al. 2006)

High-Energy Emission Model for Microquasar Jets

Injection, acceleration of ultrarelativistic

electrons

Qe (

,t)

Synchrotron emission

F

Compton emission

F

-q

Seed photons:

Synchrotron (SSC), Accr. Disk + BLR (EC)

Injection over finite length near the base of the jet.

Additional contribution from absorption along the jet

Leptonic Models

Relativistic jet outflow with ≈ 2

+ Companion star light→ Include abs. by companion star light!

Microquasar Jet Model for LS 5039

Dermer & Böttcher (2006)

Gupta et al. (2006)

Bosch-Ramon et al. (2005)

Böttcher & Dermer (2005)

Problems with GeV – TeV

spectral shape → EGRET

(GeV) source may not be

associated with LS 5039

Orbital Modulation in LS I +61 303

Albert et al. (2006)

MAGIC (> 400 GeV) Radio (15 GHz)

Fit to LSI +61o303

Orbital modulation of VHE -rays can be explained by absorption alone!