We have collected and analyzed the complete archive of XMM-Newton (116), Chandra (151), and RXTE (952) observations of the Small Magellanic Cloud (SMC), spanning 1997-2014. The resulting observational library provides a comprehensive view of the physical, temporal and statistical properties of the SMC pulsar population across the luminosity range of L X = 10 31.2 -10 38 erg s −1 . From a sample of 67 pulsars we report ∼1654 individual pulsar detections, yielding ∼1260 pulse period measurements. Our pipeline generates a suite of products for each pulsar detection: spin period, flux, event list, high time-resolution light-curve, pulse-profile, periodogram, and spectrum. Combining all three satellites, we generated complete histories of the spin periods, pulse amplitudes, pulsed fractions and X-ray luminosities. Some pulsars show variations in pulse period due to the combination of orbital motion and accretion torques. Long-term spin-up/down trends are seen in 12/11 pulsars respectively, pointing to sustained transfer of mass and angular momentum to the neutron star on decadal timescales. Of the sample 30 pulsars have relatively very small spin period derivative and may be close to equilibrium spin. The distributions of pulse-detection and flux as functions of spin-period provide interesting findings: mapping boundaries of accretion-driven X-ray luminosity, and showing that fast pulsars (P <10 s) are rarely detected, which yet are more prone to giant outbursts. Accompanying this paper is an initial public release of the library so that it can be used by other researchers. We intend the library to be useful in driving improved models of neutron star magnetospheres and accretion physics.

We analyze previous results on the stability of uniformly and di erentially rotating, self{gravitating, gaseous and stellar, axisymmetric systems to derive a new stability criterion for the appearance of toroidal, m = 2 Intermediate or I{modes and bar modes. In the process, we demonstrate that the bar modes in stellar systems and the m = 2 I{modes in gaseous systems have many common physical characteristics and only one substantial di erence: because of the anisotropy of the stress tensor, dynamical instability sets in at lower rotation in stellar systems. This di erence is re ected also in the new stability criterion.The new stability parameter = T J =jWj is formulated rst for uniformly rotating systems and is based on the angular momentum content rather than on the energy content of a system. (T J L J =2, L is the total angular momentum, J is the Jeans frequency introduced by self{gravity, and W is the total gravitational potential energy.)For stability of stellar systems 0:254{0.258 while 0:341{0.354 for stability of gaseous systems.For uniform rotation, one can write = (ft=2) 1=2 , where t T=jWj, T is the total kinetic energy due to rotation, and f is a function characteristic of the topology/connectedness and the geometric shape of a system. Equivalently, = t= , where = J and is the rotation frequency. Using these forms, can be extended to and calculated for a variety of di erentially rotating, gaseous and stellar, axisymmetric disk and spheroidal models whose equilibrium structures and stability characteristics are known. In this paper, we also estimate for gaseous toroidal models and for stellar disk systems embedded in an inert or responsive \halo." We nd that the new stability criterion holds equally well for all these previously published axisymmetric models.

The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1%. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism and subsequently injected into intergalactic space by the jet outflows.

Context. Helical magnetic fields embedded in the jets of active galactic nuclei (AGNs) are required by the broad range of theoretical models that advocate for electromagnetic launching of the jets. In most models, the direction of the magnetic field is random, but if the axial field is generated by a Cosmic Battery generated by current in the direction of rotation in the accretion disk, there is a correlation between the directions of the spin of the AGN accretion disk and of the axial field, which leads to a specific direction for the axial electric current, azimuthal magnetic field, and the resulting observed transverse Faraday-rotation (FR) gradient across the jet, due to the systematic change in the line-of-sight magnetic field. Aims. We consider new observational evidence for the presence of a nested helical magnetic-field structure such as would be brought about by the operation of the Cosmic Battery, and make predictions about the expected behavior of transverse FR gradients observed on decaparsec and kiloparsec scales. Methods. We have jointly considered 27 detections of transverse FR gradients on parsec scales, four reports of reversals in the directions of observed transverse FR gradients observed on parsec-decaparsec scales, and five detections of transverse FR gradients on decaparsec-kiloparsec scales, one reported here for the first time. We also consider seven tentative additional examples of transverse FR gradients on kiloparsec scales, based on an initial visual inspection of published Very Large Array FR maps of 85 extragalactic radio sources, for three of which we have carried out quantitative analyses in order to quantitatively estimate the significances of the gradients. Results. The data considered indicate a predominance of transverse FR gradients in the clockwise direction on the sky (i.e., net axial current flowing inward in the jet) on parsec scales and in the counter-clockwise direction on the sky (i.e., net axial current flowing outward) on scales greater than about 10 pc, consistent with the expectations for the Cosmic Battery. The predominance of counter-clockwise FR gradients on larger scales has been established at the 3σ confidence level. Conclusions. The collected results provide evidence for a reversal in the direction of the net azimuthal magnetic field determining the ordered component of the observed FR images, with distance from the jet base. This can be understood if the dominant azimuthal field on parsec scales corresponds to an axial electric current flowing inward along the jet, whereas the (weaker) dominant azimuthal field on kiloparsec scales corresponds to a outward-flowing current in the outer sheath of the jet and/or an extended disk wind. This is precisely the current/magnetic field structure that should be generated by the Cosmic Battery.

We have combined the published observations of high-mass X-ray binary (HMXB) pulsars in the Magellanic Clouds with a new processing of the complete archival data sets from the XMM-Newton and Chandra observatories in an attempt to trace the lowest propeller line below which accretion to polar caps is inhibited by the centrifugal force and the pulsations from the most weakly magnetized pulsars cease. Previously published data reveal that some of the faster-spinning pulsars with spin periods of P S  < 12 s, detected at relatively low X-ray luminosities L X , appear to define such a line in the P S –L X diagram, characterized by a magnetic moment of μ = 3 × 1029 G cm3. This value implies the presence of surface magnetic fields of B ≥ 3 × 1011 G in the compact objects of this class. Only a few quiescent HMXBs are found below the propeller line: LXP4.40 and SXP4.78, for which XMM-Newton and Chandra null detections respectively placed firm upper limits on their X-ray fluxes in deep quiescence; and A0538-66, for which many sub-Eddington detections have never measured any pulsations. On the other hand, the data from the XMM-Newton and Chandra archives show clearly that, during routine observation cycles, several sources have been detected below the propeller line in extremely faint, nonpulsating states that can be understood as the result of weak magnetospheric emission when accretion to the poles is centrifugally stalled or severely diminished. We also pay attention to the anomalous X-ray pulsar CXOU J010043.1-721134 that was reported in HMXB surveys. Its pulsations and locations near and above the propeller line indicate that this pulsar could be accreting from a fossil disk.

Context. Neutron-star and black-hole X-ray binaries (XRBs) exhibit radio jets, whose properties depend on the X-ray spectral state and history of the source. In particular, black-hole XRBs emit compact, steady radio jets when they are in the so-called hard state. These jets become eruptive as the sources move toward the soft state, disappear in the soft state, and then re-appear when the sources return to the hard state. The jets from neutron-star X-ray binaries are typically weaker radio emitters than the black-hole ones at the same X-ray luminosity and in some cases radio emission is detected in the soft state. Aims. Significant phenomenology has been developed to describe the spectral states of neutron-star and black-hole XRBs, and there is general agreement about the type of the accretion disk around the compact object in the various spectral states. We investigate whether the phenomenology describing the X-ray emission on one hand and the jet appearance and disappearance on the other can be put together in a consistent physical picture. Methods. We consider the so-called Poynting-Robertson cosmic battery (PRCB), which has been shown to explain in a natural way the formation of magnetic fields in the disks of AGNs and the ejection of jets. We investigate whether the PRCB can also explain the formation, destruction, and variability of jets in XRBs. Results. We find excellent agreement between the conditions under which the PRCB is efficient (i.e., the type of the accretion disk) and the emission or destruction of the radio jet. Conclusions. The disk-jet connection in XRBs can be explained in a natural way using the PRCB.

The relative phasing of the X-ray eclipse ephemeris and optical radial velocity (RV) curve for the X-ray binary IC10 X-1 suggests the He[λ4686] emission-line originates in a shadowed sector of the stellar wind that avoids ionization by X-rays from the compact object. The line attains maximum blueshift when the wind is directly toward us at mid X-ray eclipse, as is also seen in Cygnus X-3. If the RV curve is unrelated to stellar motion, evidence for a massive black hole evaporates because the mass function of the binary is unknown. The reported X-ray luminosity, spectrum, slow QPO, and broad eclipses caused by absorption/scattering in the WR wind are all consistent with either a low-stellar-mass BH or a NS. For a NS, the centre of mass lies inside the WR envelope whose motion is then far below the observed 370 km/s RV amplitude, while the velocity of the compact object is as high as 600 km/s. The resulting 0.4% doppler variation of X-ray spectral lines could be confirmed by missions in development. These arguments also apply to other putative BH binaries whose RV and eclipse curves are not yet phase-connected. Theories of BH formation and predicted rates of gravitational wave sources may need revision.

We reinvestigate the generation and accumulation of magnetic flux in optically thin accretion flows around active gravitating objects. The source of the magnetic field is the azimuthal electric current associated with the PoyntingRobertson drag on the electrons of the accreting plasma. This current generates magnetic field loops that open up because of the differential rotation of the flow. We show through simple numerical simulations that what regulates the generation and accumulation of magnetic flux near the center is the value of the plasma conductivity. Although the conductivity is usually considered to be effectively infinite for the fully ionized plasmas expected near the inner edge of accretion disks, the turbulence of those plasmas may actually render them much less conducting due to the presence of anomalous resistivity. We have discovered that if the resistivity is sufficiently high throughout the turbulent disk while it is suppressed inside its inner edge, an interesting steady state process is established: accretion carries and accumulates magnetic flux of one polarity inside the inner edge of the disk, whereas magnetic diffusion releases magnetic flux of the opposite polarity to large distances. In this scenario, magnetic flux of one polarity grows and accumulates at a steady rate in the region inside the inner edge and up to the point of equipartition when it becomes dynamically important. We argue that this inward growth and outward expulsion of oppositely directed magnetic fields that we propose could account for the $30 minute cyclic variability observed in the Galactic microquasar GRS 1915+105.