ALBERT

Description: We present initial results from the low-latitude Galactic plane region of the High Time Resolution Universe pulsar survey conducted at the Parkes 64-m radio telescope. We discuss the computational challenges arising from the processing of the terabyte-sized survey data. Two new radio interference mitigation techniques are introduced, as well as a partially coherent segmented acceleration search algorithm which aims to increase our chances of discovering highly relativistic short-orbit binary systems, covering a parameter space including potential pulsar–black hole binaries. We show that under a constant acceleration approximation, a ratio of data length over orbital period of 0.1 results in the highest effectiveness for this search algorithm. From the 50 per cent of data processed thus far, we have redetected 435 previously known pulsars and discovered a further 60 pulsars, two of which are fast-spinning pulsars with periods less than 30 ms. PSR J1101–6424 is a millisecond pulsar whose heavy white dwarf (WD) companion and short spin period of 5.1 ms indicate a rare example of full-recycling via Case A Roche lobe overflow. PSR J1757–27 appears to be an isolated recycled pulsar with a relatively long spin period of 17 ms. In addition, PSR J1244–6359 is a mildly recycled binary system with a heavy WD companion, PSR J1755–25 has a significant orbital eccentricity of 0.09 and PSR J1759–24 is likely to be a long-orbit eclipsing binary with orbital period of the order of tens of years. Comparison of our newly discovered pulsar sample to the known population suggests that they belong to an older population. Furthermore, we demonstrate that our current pulsar detection yield is as expected from population synthesis.

Description: We present a polarimetric analysis of 49 long-period pulsars discovered as part of the High Time Resolution Universe (HTRU) southern survey. The sources exhibit the typical characteristics of ‘old’ pulsars, with low fractional linear and circular polarization and narrow, multi-component profiles. Although the position angle swings are generally complex, for two of the analysed pulsars (J1622–3751 and J1710–2616) we obtained an indication of the geometry via the rotating vector model. We were able to determine a value of the rotation measure (RM) for 34 of the sources which, when combined with their dispersion measures (DM), yields an integrated magnetic field strength along the line of sight. With the data presented here, the total number of values of RM associated with pulsars discovered during the HTRU southern survey sums to 51. The RMs are not consistent with the hypothesis of a counter-clockwise direction of the Galactic magnetic field within an annulus included between 4 and 6 kpc from the Galactic Centre. A partial agreement with a counter-clockwise sense of the Galactic magnetic field within the spiral arms is, however, found in the area of the Carina-Sagittarius arm.

Description: Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Champion, David J -- Ransom, Scott M -- Lazarus, Patrick -- Camilo, Fernando -- Bassa, Cees -- Kaspi, Victoria M -- Nice, David J -- Freire, Paulo C C -- Stairs, Ingrid H -- van Leeuwen, Joeri -- Stappers, Ben W -- Cordes, James M -- Hessels, Jason W T -- Lorimer, Duncan R -- Arzoumanian, Zaven -- Backer, Don C -- Bhat, N D Ramesh -- Chatterjee, Shami -- Cognard, Ismael -- Deneva, Julia S -- Faucher-Giguere, Claude-Andre -- Gaensler, Bryan M -- Han, Jinlin -- Jenet, Fredrick A -- Kasian, Laura -- Kondratiev, Vlad I -- Kramer, Michael -- Lazio, Joseph -- McLaughlin, Maura A -- Venkataraman, Arun -- Vlemmings, Wouter -- New York, N.Y. -- Science. 2008 Jun 6;320(5881):1309-12. doi: 10.1126/science.1157580. Epub 2008 May 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada. David.Champion@atnf.csiro.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18483399" target="_blank"〉PubMed〈/a〉

Description: Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period; the pulsar likely has closely aligned magnetic and spin axes. The massive computing power provided by volunteers should enable many more such discoveries.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Knispel, B -- Allen, B -- Cordes, J M -- Deneva, J S -- Anderson, D -- Aulbert, C -- Bhat, N D R -- Bock, O -- Bogdanov, S -- Brazier, A -- Camilo, F -- Champion, D J -- Chatterjee, S -- Crawford, F -- Demorest, P B -- Fehrmann, H -- Freire, P C C -- Gonzalez, M E -- Hammer, D -- Hessels, J W T -- Jenet, F A -- Kasian, L -- Kaspi, V M -- Kramer, M -- Lazarus, P -- van Leeuwen, J -- Lorimer, D R -- Lyne, A G -- Machenschalk, B -- McLaughlin, M A -- Messenger, C -- Nice, D J -- Papa, M A -- Pletsch, H J -- Prix, R -- Ransom, S M -- Siemens, X -- Stairs, I H -- Stappers, B W -- Stovall, K -- Venkataraman, A -- New York, N.Y. -- Science. 2010 Sep 10;329(5997):1305. doi: 10.1126/science.1195253. Epub 2010 Aug 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Albert-Einstein-Institut, Max-Planck-Institut fur Gravitationsphysik, D-30167 Hannover, Germany. benjamin.knispel@aei.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20705813" target="_blank"〉PubMed〈/a〉

Description: Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey for pulsars and fast transients, we have uncovered four millisecond-duration radio transients all more than 40 degrees from the Galactic plane. The bursts' properties indicate that they are of celestial rather than terrestrial origin. Host galaxy and intergalactic medium models suggest that they have cosmological redshifts of 0.5 to 1 and distances of up to 3 gigaparsecs. No temporally coincident x- or gamma-ray signature was identified in association with the bursts. Characterization of the source population and identification of host galaxies offers an opportunity to determine the baryonic content of the universe.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thornton, D -- Stappers, B -- Bailes, M -- Barsdell, B -- Bates, S -- Bhat, N D R -- Burgay, M -- Burke-Spolaor, S -- Champion, D J -- Coster, P -- D'Amico, N -- Jameson, A -- Johnston, S -- Keith, M -- Kramer, M -- Levin, L -- Milia, S -- Ng, C -- Possenti, A -- van Straten, W -- New York, N.Y. -- Science. 2013 Jul 5;341(6141):53-6. doi: 10.1126/science.1236789.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, UK. thornton@jb.man.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23828936" target="_blank"〉PubMed〈/a〉

Description: The detection of five new fast radio bursts (FRBs) found in the 1.4-GHz High Time Resolution Universe high-latitude survey at Parkes, is presented. The rate implied is 7 $^{+5}_{-3}\times 10^3$ (95 per cent) FRBs sky –1 d –1 above a fluence of 0.13 Jy ms for an FRB of 0.128 ms duration to 1.5 Jy ms for 16 ms duration. One of these FRBs has a two-component profile, in which each component is similar to the known population of single component FRBs and the two components are separated by 2.4 ± 0.4 ms. All the FRB components appear to be unresolved following deconvolution with a scattering tail and accounting for intrachannel smearing. The two-component burst, FRB 121002, also has the highest dispersion measure (1629 pc cm –3 ) of any FRB to-date. Many of the proposed models to explain FRBs use a single high-energy event involving compact objects (such as neutron-star mergers) and therefore cannot easily explain a two-component FRB. Models that are based on extreme versions of flaring, pulsing, or orbital events, however, could produce multiple component profiles. The compatibility of these models and the FRB rate implied by these detections is discussed.

Description: Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7-millisecond pulsar, was detected in a recent survey with the Parkes 64-meter radio telescope. We show that this pulsar is in a binary system with an orbital period of 2.2 hours. The mass of its companion is near that of Jupiter, but its minimum density of 23 grams per cubic centimeter suggests that it may be an ultralow-mass carbon white dwarf. This system may thus have once been an ultracompact low-mass x-ray binary, where the companion narrowly avoided complete destruction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bailes, M -- Bates, S D -- Bhalerao, V -- Bhat, N D R -- Burgay, M -- Burke-Spolaor, S -- D'Amico, N -- Johnston, S -- Keith, M J -- Kramer, M -- Kulkarni, S R -- Levin, L -- Lyne, A G -- Milia, S -- Possenti, A -- Spitler, L -- Stappers, B -- van Straten, W -- New York, N.Y. -- Science. 2011 Sep 23;333(6050):1717-20. doi: 10.1126/science.1208890. Epub 2011 Aug 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Astrophysics and Supercomputing and ARC Centre for All-Sky Astrophysics (CAASTRO), Swinburne University of Technology, Post Office Box 218 Hawthorn, VIC 3122, Australia. mbailes@swin.edu.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21868629" target="_blank"〉PubMed〈/a〉

Description: The formation and growth processes of supermassive black holes (SMBHs) are not well constrained. SMBH population models, however, provide specific predictions for the properties of the gravitational-wave background (GWB) from binary SMBHs in merging galaxies throughout the universe. Using observations from the Parkes Pulsar Timing Array, we constrain the fractional GWB energy density (Omega(GW)) with 95% confidence to be Omega(GW)(H0/73 kilometers per second per megaparsec)(2) 〈 1.3 x 10(-9) (where H0 is the Hubble constant) at a frequency of 2.8 nanohertz, which is approximately a factor of 6 more stringent than previous limits. We compare our limit to models of the SMBH population and find inconsistencies at confidence levels between 46 and 91%. For example, the standard galaxy formation model implemented in the Millennium Simulation Project is inconsistent with our limit with 50% probability.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shannon, R M -- Ravi, V -- Coles, W A -- Hobbs, G -- Keith, M J -- Manchester, R N -- Wyithe, J S B -- Bailes, M -- Bhat, N D R -- Burke-Spolaor, S -- Khoo, J -- Levin, Y -- Oslowski, S -- Sarkissian, J M -- van Straten, W -- Verbiest, J P W -- Wang, J-B -- New York, N.Y. -- Science. 2013 Oct 18;342(6156):334-7. doi: 10.1126/science.1238012.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Commonwealth Scientific and Industrial Research Organisation (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24136962" target="_blank"〉PubMed〈/a〉

Description: Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be 〈1.0 x 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shannon, R M -- Ravi, V -- Lentati, L T -- Lasky, P D -- Hobbs, G -- Kerr, M -- Manchester, R N -- Coles, W A -- Levin, Y -- Bailes, M -- Bhat, N D R -- Burke-Spolaor, S -- Dai, S -- Keith, M J -- Oslowski, S -- Reardon, D J -- van Straten, W -- Toomey, L -- Wang, J-B -- Wen, L -- Wyithe, J S B -- Zhu, X-J -- New York, N.Y. -- Science. 2015 Sep 25;349(6255):1522-5. doi: 10.1126/science.aab1910.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia. International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia. ; Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Post Office Box 218, Hawthorn, Victoria 3122, Australia. ; Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK. ; Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Post Office Box 27, Victoria 3800, Australia. ; Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia. ; Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA 92093, USA. ; International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia. ; National Radio Astronomical Observatory, Array Operations Center, Post Office Box O, Socorro, NM 87801-0387, USA. ; Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia. Department of Astronomy, School of Physics, Peking University, Beijing 100871, China. ; Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL, UK. ; Department of Physics, Universitat Bielefeld, Universitatsstrasse 25, D-33615 Bielefeld, Germany. Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany. ; Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, Xinjiang 830011, China. ; School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia. ; School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26404832" target="_blank"〉PubMed〈/a〉