We present a 50 ks observation of the gamma-ray binary LS I +61 303 carried out with the ACIS-I array aboard the Chandra X-ray Observatory. This is the highest resolution X-ray observation of the source conducted so far. Possible evidence of an extended structure at a distance between 5 ′′ and 12 ′′ towards the North of LS I +61 303 have been found at a significance level of 3.2σ. The asymmetry of the extended emission excludes an interpretation in the context of a dust-scattered halo, suggesting an intrinsic nature. On the other hand, while the obtained source flux, of F 0.3−10 keV = 7.1 +1.8 −1.4 × 10 −12 ergs cm −2 s −1 , and hydrogen column density, N H = 0.70 ± 0.06 × 10 22 cm −2 , are compatible with previous results, the photon index Γ = 1.25 ± 0.09 is the hardest ever found. In light of these new results, we briefly discuss the physics behind the X-ray emission, the location of the emitter, and the possible origin of the extended emission ∼0.1 pc away from LS I +61 303.

Abstract. We present XMM-Newton observations of the eclipsing, disc accreting, cataclysmic variable OY Car which were obtained as part of the performance verification phase of the mission. The star was observed 4 days after an outburst and then again 5 weeks later when it was in a quiescent state. There is a quasi-stable modulation of the X-rays at ∼2240 s, which is most prominent at the lowest energies. We speculate that this may be related to the spin period of the white dwarf. The duration of the eclipse ingress and egress in X-rays is 20-30 s. This indicates that the bulk of the X-ray emission originates from the boundary layer which has a negligible height above the surface of the white dwarf. The eclipse profile implies a white dwarf of mass M1 = 0.9−1.1 M and a secondary star of M2 = 0.08−0.11 M .

We propose a theory in which the Standard Model gauge symmetry is extended by a new SU (2) group acting nontrivially on the lepton sector which is spontaneously broken at the TeV scale. Under this SU (2) the ordinary leptons form doublets along with new lepton partner fields. This construction naturally contains a dark matter candidate, the partner of the right-handed neutrino, stabilized by a residual global U (1)χ symmetry. We show that one can explain baryogenesis through an asymmetric dark matter scenario, in which generation of related asymmetries in the dark matter and baryon sectors is driven by the SU (2) instantons during a first order phase transition in the early universe.

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