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Illustration of a neutron star. Credit: NASA/Dana Berry There is good evidence that electron-positron pair formation is not present in that section of the pulsar open magnetosphere which is the source of coherent radio emission, but the possibility of two-photon pair creation in an outer gap remains. Calculation of transition rates for this process based on measured whole-surface temperatures, combined with a survey of gamma-ray, X-ray and optical luminosities, expressed per primary beam lepton, shows that few Fermi LAT pulsars have significant outer-gap pair creation. For radio-loud pulsars with positive polar-cap corotational charge density and an ion-proton plasma there must be an outward flow of electrons from some other part of the magnetosphere to maintain a constant net charge on the star. In the absence of pair creation, it is likely that this current is the source of GeV gamma-emission observed by the Fermi LAT and its origin is in the region of the outer gap. With n...

Figure - An artist's impression of an accreting Low Mass X-ray Binary. The donor star fills its Roche lobe and its material overflows the inner Lagrangian points and accretes on the relativistic star. Due to the large angular momentum of the infalling material an accretion disk is formed around the compact object. Credit: ESA, NASA, and Felix Mirabel (French Atomic Energy Commission and Institute for Astronomy and Space Physics/Conicet of Argentina) A low-mass X-ray binary (LMXB) contains a neutron star which is accreting material via Roche lobe overflow from a companion star. Due to the high angular momentum of the accretion flow an accretion disc is formed around the compact object. In a recent paper ( van den Berg & Homan 2016 ) the authors have determined an improved position for the luminous persistent neutron-star low-mass X-ray binary and atoll source GX 9+1 from archival Chandra X-ray Observatory data and they have identified a new near-infrared (NIR) counterpar...

Picture: These images show the merger of two neutron stars simulated using a new supercomputer model. Redder colors indicate lower densities. Green and white ribbons and lines represent magnetic fields. The orbiting neutron stars rapidly lose energy by emitting gravitational waves and merge after about three orbits, or in less than 8 milliseconds. The merger amplifies and scrambles the merged magnetic field. A black hole forms and the magnetic field becomes more organized, eventually producing structures capable of supporting the jets that power short gamma-ray bursts. Credit: NASA/AEI/ZIB/M. Koppitz and L. Rezzolla The LIGO and Virgo Collaborations recently reported the first direct detection of a gravitational-wave (GW) signal and demonstrated that it was produced by the inspiral and coalescence of a binary black hole (BHBH) system.

Image: Artist's impression of a magnetar. Credit: ESO/L. Calçada In a recent paper ( Lyutikov et al. 2016 ) the authors discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ~ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods.

Image: Artistic representation of Doulbe Neutron Stars. Credit: NASA/Goddard Space Flight Center Double Neutron Stars (DNS) have to survive two supernovae and still remain bound. For this reason these systems are a unique and rare population of neutron stars and sets strong limits on the nature of the second collapse. Moreover, DNS emit gravitational radiation and consequently their orbit decays and they merge. This make DNS systems prime candidates for detection of gravitational radiation.

Image: Crab nebula as seen by Chandra. Credit: NASA/CXC/SAO/F. Seward et al. In the center of several supernova remnants there are pulsars with significantly lower values of the dipolar magnetic field than the average radio-pulsar population (10^{ 12 }G). A possible explanation requires the slow rotation of the proto-neutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels.

Image Credit: David A. Hardy & PPARC Accreting neutron stars exhibit bursts due to nuclear burning of hydrogen/helium and rarely even carbon. The carbon flashes generate the superbusts. The carbon is produced during the hydrogen/helium flashes. However the amount of carbon produced in hydrogen/helium flashes is insufficient to power the superbursts.