LS I + 61 303 - DIAS

Known gamma-ray binariesGamma-ray binaries are stellar binaries formed by a compactobject (a neutron star or a black holes) and a donor star. All ofthem were detected first as X-ray binaries.So far, the detected gamma-ray binaries are: PSR B1259-63(Aharonian et al. 2005a), LS 5039 (Aharonian et al. 2005b), LSI +61 303 (Albert et al. 2006), and Cygnus X-1 (Albert et al.2007). All of them are variable at gamma-rays.PSR B1259-63 is a confirmed pulsar/Be system and Cygnus X-1is a confirmed microquasar. The nature of both LS 5039 and LSI +61 303 is matter of controvery at present (see Romero et al.2007) .

MODELS FOR GAMMA-RAY BINARIESMirabel (Science 309, 714, 2006)1) IC by e - in the jets on stellar or synchrotron photons (Bosch-Ramon et al. 2006)or hadrons in the jets (Romero et al. 2003, 2005) with matter of the stellar wind.2) IC by e - accelerated at a colliding wind region (e.g. PSR B1259-63, Maraschi &Treves, 1981; Tavani et al. 1994, Kirk et al. 1999, Khangulyan et al. 2007)

A case of study: LSI +61 303Ten points at equal phase intervals from φ = 0 to φ = 0.9, with MAGIC observations(where available) on the right. The periastron is at φ = 0.2.

Extended X-ray structure?Paredes et al. (2007)

Tidal interactionand accretion disksimulations

Accretion rateSimsBondi-Hoyle

Opacity to gamma-ray propagationVer Romero et al. (2007) for details

ConclusionsThe morphology of the radio emission does not correspond towhat is expected from a pulsar/Be colliding wind model.Colliding wind models cannot reproduce the lightcurve or thegamma-ray luminosity of the source.The decretion disc of the Be star is truncated and accretion ontothe compact object is different from what can be expected in asimple Bondi-Hoyle model.The accretion rate is a small fraction of Eddington limit.The microquasar model still offers the best hipothesis for thenature of LS I +61 303.For a colliding wind sims of PSR 1259-63 seethe poster by Bogovalov et al.