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 the discovery of a further five recycled pulsar systems in the mid-Galactic latitude portion of the High Time Resolution Universe survey. The pulsars have rotational periods ranging from 2 to 66 ms, and four are in binary systems with orbital periods between 10.8 h and 9 d. Three of these binary systems are particularly interesting; PSR J1227–6208 has a pulse period of 34.5 ms and the highest mass function of all pulsars with near-circular orbits. The circular orbit suggests that the companion is not another neutron star, so future timing experiments may reveal one of the heaviest white dwarfs ever found (〉1.3 M ). Timing observations of PSR J1431–4715 indicate that it is eclipsed by its companion which has a mass indicating it belongs to the redback class of eclipsing millisecond pulsars. PSR J1653–2054 has a companion with a minimum mass of only 0.08 M , placing it among the class of pulsars with low-mass companions. Unlike the majority of such systems, however, no evidence of eclipses is seen at 1.4 GHz.

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: We report on the discovery of four millisecond pulsars (MSPs) in the High Time Resolution Universe (HTRU) pulsar survey being conducted at the Parkes 64 m radio telescope. All four MSPs are in binary systems and are likely to have white dwarf companions. In addition, we present updated timing solutions for 12 previously published HTRU MSPs, revealing new observational parameters such as five proper motion measurements and significant temporal dispersion measure variations in PSR J1017–7156. We discuss the case of PSR J1801–3210, which shows no significant period derivative P after four years of timing data. Our best-fitting solution shows a P of the order of 10 –23 , an extremely small number compared to that of a typical MSP. However, it is likely that the pulsar lies beyond the Galactic Centre, and an unremarkable intrinsic P is reduced to close to zero by the Galactic potential acceleration. Furthermore, we highlight the potential to employ PSR J1801–3210 in the strong equivalence principle test due to its wide and circular orbit. In a broader comparison with the known MSP population, we suggest a correlation between higher mass functions and the presence of eclipses in ‘very low mass binary pulsars’, implying that eclipses are observed in systems with high orbital inclinations. We also suggest that the distribution of the total mass of binary systems is inversely related to the Galactic height distribution. Finally, we report on the first detection of PSRs J1543–5149 and J1811–2404 as gamma-ray pulsars.

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: 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〉

Description: In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 +/- 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of OmegaIGM = 4.9 +/- 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short gamma-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keane, E F -- Johnston, S -- Bhandari, S -- Barr, E -- Bhat, N D R -- Burgay, M -- Caleb, M -- Flynn, C -- Jameson, A -- Kramer, M -- Petroff, E -- Possenti, A -- van Straten, W -- Bailes, M -- Burke-Spolaor, S -- Eatough, R P -- Stappers, B W -- Totani, T -- Honma, M -- Furusawa, H -- Hattori, T -- Morokuma, T -- Niino, Y -- Sugai, H -- Terai, T -- Tominaga, N -- Yamasaki, S -- Yasuda, N -- Allen, R -- Cooke, J -- Jencson, J -- Kasliwal, M M -- Kaplan, D L -- Tingay, S J -- Williams, A -- Wayth, R -- Chandra, P -- Perrodin, D -- Berezina, M -- Mickaliger, M -- Bassa, C -- England -- Nature. 2016 Feb 25;530(7591):453-6. doi: 10.1038/nature17140.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Square Kilometre Array Organisation, Jodrell Bank Observatory, SK11 9DL, UK. ; Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H29, PO Box 218, Victoria 3122, Australia. ; Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia. ; Commonwealth Science and Industrial Research Organisation (CSIRO), Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, New South Wales 1710, Australia. ; International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia. ; Instituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy. ; Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory 2611, Australia. ; Max-Planck-Institut fur Radioastronomie (MPIfR), Auf dem Hugel 69, D-53121 Bonn, Germany. ; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK. ; National Radio Astronomy Observatory, Socorro, New Mexico, USA. ; Department of Astronomy, the University of Tokyo, Hongo, Tokyo 113-0033, Japan. ; National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan. ; Department of Astronomical Science, SOKENDAI (Graduate University for the Advanced Study), Osawa, Mitaka 181-8588, Japan. ; Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, Hawaii 96720, USA. ; Institute of Astronomy, Graduate School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan. ; Kavli Institute for the Physics and Mathematics of the Universe (WPI), Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583, Japan. ; Department of Physics, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Kobe, Hyogo 658-8501, Japan. ; Cahill Center for Astrophysics, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA. ; Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA. ; National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Ganeshkhind, Pune 411 007, India. ; ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26911781" target="_blank"〉PubMed〈/a〉