The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna groundspace radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

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The ejecta composition is an open question in gamma-ray bursts (GRB) physics 1 . Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis 2 , suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the "Band" function 3-5 , consistent with a synchrotron radiation origin 5,6 and suggesting that the jet is Poynting-flux-dominated at the central engine and likely in the emission region as well 7,8 . There are also bursts showing a subdominant thermal component and a dominant synchrotron component 9 , suggesting a likely hybrid jet composition 10 . Here we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-rays and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each "sub-burst" being ∼ 0.8 s, 35 s, and 212 s, respectively. Its high brightness (with isotropic peak luminosity L p,iso ∼ 4 × 10 53 erg/s) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet.

In this article we revise the problem of anomalous values of pulsar braking indices nobs and frequency second derivatives arising in observations. The intrinsic evolutionary braking is buried deep under superimposed irregular processes, which prevent direct estimations of its parameters for the majority of pulsars. We re‐analyse the distribution of ‘ordinary’ radio pulsars on –, –ν, –ν and nobs–τch diagrams assuming their spin‐down to be the superposition of a ‘true’ monotonic term and a symmetric oscillatory term. We demonstrate that their effects may be clearly separated using simple ad hoc arguments. Using the maximum‐likelihood estimator, we derive the parameters of both components. We find characteristic time‐scales of such oscillations to be of the order of 103–104 yr, while their amplitudes are large enough to modulate the observed spin‐down rate up to 0.5–5 times and completely dominate the second frequency derivatives. On the other hand, pulsar secular evolution is consistent with the classical magnetodipolar model with braking index n≈ 3. Therefore, observed pulsar characteristic ages (and similar estimators that depend on the observed ) are also affected by long‐term cyclic processes and differ up to 0.5–5 times from their monotonic values. This fact naturally resolves the discrepancy of characteristic and independently estimated physical ages of several objects, as well as explaining the very large, up to 108 yr, characteristic ages of some pulsars. We discuss the possible physical connection of long‐term oscillation with complex neutron star rotation relative to its magnetic axis due to the influence of the near‐field part of the magnetodipolar torque.

We have developed a method for analyzing the kinematic association of isolated relativistic objects possible remnants of disrupted close binary systems. We investigate pairs of fairly young radio pulsars with known proper motions and estimated distances (dispersion measures) that are spaced no more than 2-3 kpc apart. Using a specified radial velocity distribution for these objects, we have constructed 100-300 thousand trajectories of their possible motion in the Galactic gravitational field on a time scale of several million years. The probabilities of their close encounters at epochs consistent with the age of the younger pulsar in the pair are analyzed. When these probabilities exceed considerably their reference values obtained by assuming a purely randomencounter between the pulsars under consideration, we conclude that the objects may have been gravitationally bound in the past. As a result, we have detected six pulsar pairs (J0543+2329/J0528+2200, J1453-6413/J1430-6623, J2354+6155/J2321+6024, J1915+1009/J1909+1102, J1832-0827/J1836-1008, and J1917+1353/J1926+1648) that are companions in disrupted binary systems with a high probability. Estimates of their kinematic ages and velocities at binary disruption and at the present epoch are provided.