16206012
Giant pulses from PSR B1937+21 with widths ≤15 nanoseconds and Tb ≥ 5 × 1039 K, the highest brightness temperature observed in the universe
Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70 m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65,000 Jy with widths ≤15 ns, corresponding to a brightness temperature of Tb ≥ 5 × 1039 K, the highest observed in the universe. The vast majority of these pulses occur in 5.8 and 8.2 μs windows at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur, in general, with a single spike. Only in one case of 309 was the structure clearly more complex. The cumulative distribution is fitted by a power law with index -1.40 ± 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the directivity factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensities or energies of the main pulses and interpulses themselves. Their radiation energy density can exceed 300 times the plasma energy density at the surface of the neutron star and can even exceed the magnetic field energy density at that surface. We therefore do not think that the generation of giant pulses is linked to the plasma mechanisms in the magnetosphere. Instead we suggest that it is directly related to discharges in the polar cap region of the pulsar.
119110916
DISCOVERY OF THE OPTICAL/ULTRAVIOLET/GAMMA-RAY COUNTERPART TO THE ECLIPSING MILLISECOND PULSAR J1816+4510
The energetic, eclipsing millisecond pulsar J1816+4510 was recently discovered in a low-frequency radio survey with the Green Bank Telescope. With an orbital period of 8.7?hr and a minimum companion mass of 0.16?M ?, it appears to belong to an increasingly important class of pulsars that are ablating their low-mass companions. We report the discovery of the ?-ray counterpart to this pulsar and present a likely optical/ultraviolet counterpart as well. Using the radio ephemeris, we detect pulsations in the unclassified ?-ray source 2FGL J1816.5+4511, implying an efficiency of ~25% in converting the pulsar's spin-down luminosity into ?-rays and adding PSR J1816+4510 to the large number of millisecond pulsars detected by Fermi. The likely optical/UV counterpart was identified through position coincidence (<01) and unusual colors. Assuming that it is the companion, with R = 18.27 ? 0.03?mag and effective temperature 15,000?K, it would be among the brightest and hottest of low-mass pulsar companions and appears qualitatively different from other eclipsing pulsar systems. In particular, current data suggest that it is a factor of two larger than most white dwarfs of its mass but a factor of four smaller than its Roche lobe. We discuss possible reasons for its high temperature and odd size, and suggest that it recently underwent a violent episode of mass loss. Regardless of origin, its brightness and the relative unimportance of irradiation make it an ideal target for a mass, and hence a neutron star mass, determination.
118484572
Pulsars with the Australian square kilometre array pathfinder
The Australian Square Kilometre Array Pathfinder (ASKAP) is a 36‐element array with a 30‐square‐degree field of view being built at the proposed SKA site in Western Australia. We are conducting a Design Study for pulsar observations with ASKAP, planning both timing and search observations. We provide an overview of the ASKAP telescope and an update on pulsar‐related progress.
4468698
A millisecond pulsar in a stellar triple system
Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13), where is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15) and 0.4101(3)), as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.
11211511
The shape of the radio wavefront of extensive air showers as measured with LOFAR
Extensive air showers, induced by high energy cosmic rays impinging on the Earth's atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parametrization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle.
119267370
A new interpretation of Giant radio pulses from the Crab pulsar
The Crab pulsar experienced a major flare in 2010 as observed by Fermi LAT. Observations by the Hubble Space Telescope indicate that the flare was accompanied by a structural change in the anvil region of the Crab Nebula. In the framework of a photometric analysis we reconstruct the energetics of this event. Reconnection zones near the light cylinder are expected to release energy by accelerating beams of electrons, leading to flares of varying amplitude. In this case the major flare would have reduced the magnetic energy stored in the reconnection zones, and would thus have had an impact on the properties of the giant radio flares presumably originating from these regions. We test this scenario by observing giant radio pulses with the Westerbork Synthesis Radio Telescope.
121572324
Results of in-beam tests of an MCP-based vacuum sector prototype of the T0/centrality detector for ALICE
AbstractWereportonresultsofeﬃciencytestsforMIPsandtimingresolutionstudiesobtainedwithdiﬀerentlayoutsofmicro-channelplate(MCP)detectorprototypesatCERNPStestbeams.ThedetectoriscomposedofanMCPstackand multipad readout anodes integrated with a passive isochronal summator. Several types of setups were tested,includingMCPswithdiﬀerentgain.Also,averyﬁrsttestoftheMicroSpherePlatesdetectorwasperformed.TheperformanceoffastelectronicsincludingDoubleThresholdDiscriminatorsandafastmultiplicitydiscriminatorforshort2nssignalswasstudied.Currently,thebestexperimentalresultsforMCPdetectorsshow75pstimingresolutionobtainedat75%eﬃciencyfortheregistrationofasinglemuon.Weexpectfurtherenhancements,mostlythroughimprovementsinthefastelectronics.r 2002ElsevierScienceB.V.Allrightsreserved. 1. IntroductionA Micro-Channel Plate (MCP) disk detectorsystem with integrated isochronal signal readoutandprecisetimingcapabilitiesisconsideredasoneof the options for the ALICE pre-trigger T0/centralitydetector.MCPsareawell-knowndevicefor the registration of charged particles due totheir excellent timing properties (20–50ps), highinternalgain(10
119799578
200 and 300 MeV/nucleon nuclear reactions responsible for single-event effects in microelectronics
An experimental study of nuclear reactions between Si-28 nuclei at 200 and 300 MeV/nucleon and hydrogen or deuterium target nuclei was performed at the CELSIUS storage ring in Uppsala, Sweden, to collect information about the reactions responsible for single-event effects in microelectronics. Inclusive data on Si-28 fragmentation, as well as data on correlations between recoils and spectator protons or alpha particles are compared to predictions from the Dubna cascade model and the Japan Atomic Energy Research Institute version of the quantum molecular dynamics model. The comparison shows satisfactory agreement for inclusive data except for He fragments where low-energy sub-barrier fragments and recoiling fragments with very large momenta are produced much more frequently than predicted. The yield of exclusive data are also severely underestimated by the models whereas the charge distributions of recoils in these correlations compare well. The observed enhancement in He emission, which may well be important for the description of single-event effects, is most likely to be attributed to alpha clustering in Si-28 nuclei.