How to make a mature accreting magnetar

Several candidates for accreting magnetars have been proposed recently by different authors. Existence of such systems contradicts the standard magnetic field decay scenario where a large magnetic field of a neutron star reaches $\lesssim$ few$\times 10^{13}$G at ages $\gtrsim 1$ Myr. Among other sources, the high mass X-ray binary 4U0114+65 seems to have a strong magnetic field around $10^{14}$ G. We develop a new Bayesian estimate for the kinematic age and demonstrate that 4U0114+65 has kinematic age 2.4-5 Myr ($95\%$ credential interval) since the formation of the neutron star. We discuss which conditions are necessary to explain the potential existence of magnetars in accreting high-mass binaries with ages about few Myrs and larger. Three necessary ingredients are: the Hall attractor to prevent rapid decay of dipolar field, relatively rapid cooling of the crust in order to avoid Ohmic decay due to phonons, and finally, low values of the parameter $Q$ to obtain long Ohmic time scale due to impurities. If age and magnetic field estimates for proposed accreting magnetars are correct, then these systems set the strongest limit on the crust impurity for a selected sample of neutron stars and provide evidence in favour of the Hall attractor.Comment: 8 pages, 3 figures, accepted to MNRAS on September 2

Choosing effective methods for design diversity - How to progress from intuition to science

Design diversity is a popular defence against design faults in safety critical systems. Design diversity is at times pursued by simply isolating the development teams of the different versions, but it is presumably better to "force" diversity, by appropriate prescriptions to the teams. There are many ways of forcing diversity. Yet, managers who have to choose a cost-effective combination of these have little guidance except their own intuition. We argue the need for more scientifically based recommendations, and outline the problems with producing them. We focus on what we think is the standard basis for most recommendations: the belief that, in order to produce failure diversity among versions, project decisions should aim at causing "diversity" among the faults in the versions. We attempt to clarify what these beliefs mean, in which cases they may be justified and how they can be checked or disproved experimentally

Unifying neutron stars: getting to GUNS

The variety of the observational appearance of young isolated neutron stars must find an explanation in the framework of some unifying approach. Nowadays it is believed that such scenario must include magnetic field decay, the possibility of magnetic field emergence on a time scale $\lesssim 10^4$--$10^5$ yrs, significant contribution of non-dipolar fields, and appropriate initial parameter distributions. We present our results on the initial spin period distribution, and suggest that inconsistences between distributions derived by different methods for samples with different average ages can uncover field decay or/and emerging field. We describe a new method to probe the magnetic field decay in normal pulsars. The method is a modified pulsar current approach, where we study pulsar flow along the line of increasing characteristic age for constant field. Our calculations, performed with this method, can be fitted with an exponential decay for ages in the range $8\times 10^4$--$3.5 \times 10^5$ yrs with a time scale $\sim 5 \times 10^5$ yrs. We discuss several issues related to the unifying scenario. At first, we note that the dichotomy, among local thermally emitting neutron stars, between normal pulsars and the Magnificent Seven remains unexplained. Then we discuss the role of high-mass X-ray binaries in the unification of neutron star evolution. We note, that such systems allow to check evolutionary effects on a time scale longer than what can be probed with normal pulsars alone. We conclude with a brief discussion of importance of discovering old neutron stars accreting from the interstellar medium.Comment: 6 pages, submitted to AN, proceedings of the workshop "The Fast and the Furious: Energetic Phenomena in Isolated Neutron Stars, Pulsar Wind Nebulae and Supernova Remnants" ESAC, Madrid, Spain 22nd - 24th May 201

Polarization of the electron and positron produced in combined Coulomb and strong laser fields

The process of $e^+e^-$ production in the superposition of a Coulomb and a strong laser field is considered. The pair production rate integrated over the momentum and summed over the spin projections of one of the particles is derived exactly in the parameters of the laser field and in the Born approximation with respect to the Coulomb field. The case of a monochromatic circularly polarized laser field is considered in detail. A very compact analytical expression of the pair production rate and its dependence on the polarization of one of the created particles is obtained in the quasiclassical approximation for the experimentally relevant case of an undercritical laser field. As a result, the polarization of the created electron (positron) is derived.Comment: 16 pages, no figure

Statistical properties of Klauder-Perelomov coherent states for the Morse potential

We present in this paper a realistic construction of the coherent states for the Morse potential using the Klauder-Perelomov approach . We discuss the statistical properties of these states, by deducing the Q- and P-distribution functions. The thermal expectations for the quantum canonical ideal gas of the Morse oscillators are also calculated

On Systematic Design of Protectors for Employing OTS Items

Off-the-shelf (OTS) components are increasingly used in application areas with stringent dependability requirements. Component wrapping is a well known structuring technique used in many areas. We propose a general approach to developing protective wrappers that assist in integrating OTS items with a focus on the overall system dependability. The wrappers are viewed as redundant software used to detect errors or suspicious activity and to execute appropriate recovery when possible; wrapper development is considered as a part of system integration activities. Wrappers are to be rigorously specified and executed at run time as a means of protecting OTS items against faults in the rest of the system, and the system against the OTS item's faults. Possible symptoms of erroneous behaviour to be detected by a protective wrapper and possible actions to be undertaken in response are listed and discussed. The information required for wrapper development is provided by traceability analysis. Possible approaches to implementing “protectors” in the standard current component technologies are briefly outline