ALBERT

Description: We analyse the stochastic properties of the 49 pulsars that comprise the first International Pulsar Timing Array (IPTA) data release. We use Bayesian methodology, performing model selection to determine the optimal description of the stochastic signals present in each pulsar. In addition to spin-noise and dispersion-measure (DM) variations, these models can include timing noise unique to a single observing system, or frequency band. We show the improved radio-frequency coverage and presence of overlapping data from different observing systems in the IPTA data set enables us to separate both system and band-dependent effects with much greater efficacy than in the individual pulsar timing array (PTA) data sets. For example, we show that PSR J1643–1224 has, in addition to DM variations, significant band-dependent noise that is coherent between PTAs which we interpret as coming from time-variable scattering or refraction in the ionized interstellar medium. Failing to model these different contributions appropriately can dramatically alter the astrophysical interpretation of the stochastic signals observed in the residuals. In some cases, the spectral exponent of the spin-noise signal can vary from 1.6 to 4 depending upon the model, which has direct implications for the long-term sensitivity of the pulsar to a stochastic gravitational-wave (GW) background. By using a more appropriate model, however, we can greatly improve a pulsar's sensitivity to GWs. For example, including system and band-dependent signals in the PSR J0437–4715 data set improves the upper limit on a fiducial GW background by ~60 per cent compared to a model that includes DM variations and spin-noise only.

Description: Pulsars are born with subsecond spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Abdo, A A -- Ackermann, M -- Ajello, M -- Atwood, W B -- Axelsson, M -- Baldini, L -- Ballet, J -- Barbiellini, G -- Baring, M G -- Bastieri, D -- Baughman, B M -- Bechtol, K -- Bellazzini, R -- Berenji, B -- Bignami, G F -- Blandford, R D -- Bloom, E D -- Bonamente, E -- Borgland, A W -- Bregeon, J -- Brez, A -- Brigida, M -- Bruel, P -- Burnett, T H -- Caliandro, G A -- Cameron, R A -- Camilo, F -- Caraveo, P A -- Carlson, P -- Casandjian, J M -- Cecchi, C -- Celik, O -- Charles, E -- Chekhtman, A -- Cheung, C C -- Chiang, J -- Ciprini, S -- Claus, R -- Cognard, I -- Cohen-Tanugi, J -- Cominsky, L R -- Conrad, J -- Corbet, R -- Cutini, S -- Dermer, C D -- Desvignes, G -- de Angelis, A -- de Luca, A -- de Palma, F -- Digel, S W -- Dormody, M -- do Couto e Silva, E -- Drell, P S -- Dubois, R -- Dumora, D -- Edmonds, Y -- Farnier, C -- Favuzzi, C -- Fegan, S J -- Focke, W B -- Frailis, M -- Freire, P C C -- Fukazawa, Y -- Funk, S -- Fusco, P -- Gargano, F -- Gasparrini, D -- Gehrels, N -- Germani, S -- Giebels, B -- Giglietto, N -- Giordano, F -- Glanzman, T -- Godfrey, G -- Grenier, I A -- Grondin, M H -- Grove, J E -- Guillemot, L -- Guiriec, S -- Hanabata, Y -- Harding, A K -- Hayashida, M -- Hays, E -- Hobbs, G -- Hughes, R E -- Johannesson, G -- Johnson, A S -- Johnson, R P -- Johnson, T J -- Johnson, W N -- Johnston, S -- Kamae, T -- Katagiri, H -- Kataoka, J -- Kawai, N -- Kerr, M -- Knodlseder, J -- Kocian, M L -- Kramer, M -- Kuss, M -- Lande, J -- Latronico, L -- Lemoine-Goumard, M -- Longo, F -- Loparco, F -- Lott, B -- Lovellette, M N -- Lubrano, P -- Madejski, G M -- Makeev, A -- Manchester, R N -- Marelli, M -- Mazziotta, M N -- McConville, W -- McEnery, J E -- McLaughlin, M A -- Meurer, C -- Michelson, P F -- Mitthumsiri, W -- Mizuno, T -- Moiseev, A A -- Monte, C -- Monzani, M E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nolan, P L -- Norris, J P -- Nuss, E -- Ohsugi, T -- Omodei, N -- Orlando, E -- Ormes, J F -- Paneque, D -- Panetta, J H -- Parent, D -- Pelassa, V -- Pepe, M -- Pesce-Rollins, M -- Piron, F -- Porter, T A -- Raino, S -- Rando, R -- Ransom, S M -- Ray, P S -- Razzano, M -- Rea, N -- Reimer, A -- Reimer, O -- Reposeur, T -- Ritz, S -- Rochester, L S -- Rodriguez, A Y -- Romani, R W -- Roth, M -- Ryde, F -- Sadrozinski, H F W -- Sanchez, D -- Sander, A -- Saz Parkinson, P M -- Scargle, J D -- Schalk, T L -- Sgro, C -- Siskind, E J -- Smith, D A -- Smith, P D -- Spandre, G -- Spinelli, P -- Stappers, B W -- Starck, J L -- Striani, E -- Strickman, M S -- Suson, D J -- Tajima, H -- Takahashi, H -- Tanaka, T -- Thayer, J B -- Thayer, J G -- Theureau, G -- Thompson, D J -- Thorsett, S E -- Tibaldo, L -- Torres, D F -- Tosti, G -- Tramacere, A -- Uchiyama, Y -- Usher, T L -- Van Etten, A -- Vasileiou, V -- Venter, C -- Vilchez, N -- Vitale, V -- Waite, A P -- Wallace, E -- Wang, P -- Watters, K -- Webb, N -- Weltevrede, P -- Winer, B L -- Wood, K S -- Ylinen, T -- Ziegler, M -- New York, N.Y. -- Science. 2009 Aug 14;325(5942):848-52. doi: 10.1126/science.1176113.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science Division, Naval Research Laboratory,Washington, DC 20375, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19574349" target="_blank"〉PubMed〈/a〉

Description: Pulsars are remarkable clocklike celestial sources that are believed to be rotating neutron stars formed in supernova explosions. They are valuable tools for investigations into topics such as neutron star interiors, globular cluster dynamics, the structure of the interstellar medium, and gravitational physics. Searches at radio and x-ray wavelengths over the past 5 years have resulted in a large increase in the number of known pulsars and the discovery of new populations of pulsars, posing challenges to theories of binary and stellar evolution. Recent images at radio, optical, and x-ray wavelengths have revealed structures resulting from the interaction of pulsar winds with the surrounding interstellar medium, giving new insights into the physics of pulsars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Manchester, R N -- New York, N.Y. -- Science. 2004 Apr 23;304(5670):542-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Australia Telescope National Facility, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Post Office Box 76, Epping, New South Wales 1710, Australia. dick.manchester@csiro.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15105491" target="_blank"〉PubMed〈/a〉

Description: The clocklike properties of pulsars moving in the gravitational fields of their unseen neutron-star companions have allowed unique tests of general relativity and provided evidence for gravitational radiation. We report here the detection of the 2.8-second pulsar J0737-3039B as the companion to the 23-millisecond pulsar J0737-3039A in a highly relativistic double neutron star system, allowing unprecedented tests of fundamental gravitational physics. We observed a short eclipse of J0737-3039A by J0737-3039B and orbital modulation of the flux density and the pulse shape of J0737-3039B, probably because of the influence of J0737-3039A's energy flux on its magnetosphere. These effects will allow us to probe magneto-ionic properties of a pulsar magnetosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lyne, A G -- Burgay, M -- Kramer, M -- Possenti, A -- Manchester, R N -- Camilo, F -- McLaughlin, M A -- Lorimer, D R -- D'Amico, N -- Joshi, B C -- Reynolds, J -- Freire, P C C -- New York, N.Y. -- Science. 2004 Feb 20;303(5661):1153-7. Epub 2004 Jan 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jodrell Bank Observatory, University of Manchester, Macclesfield SK11 9DL, UK. agl@jb.man.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14716022" target="_blank"〉PubMed〈/a〉

Description: The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They are also known to have much higher mean orbital velocities and accelerations than those of other binary pulsars. The system is therefore a good candidate for testing Einstein's theory of general relativity and alternative theories of gravity in the strong-field regime. We report on precision timing observations taken over the 2.5 years since its discovery and present four independent strong-field tests of general relativity. These tests use the theory-independent mass ratio of the two stars. By measuring relativistic corrections to the Keplerian description of the orbital motion, we find that the "post-Keplerian" parameter s agrees with the value predicted by general relativity within an uncertainty of 0.05%, the most precise test yet obtained. We also show that the transverse velocity of the system's center of mass is extremely small. Combined with the system's location near the Sun, this result suggests that future tests of gravitational theories with the double pulsar will supersede the best current solar system tests. It also implies that the second-born pulsar may not have formed through the core collapse of a helium star, as is usually assumed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kramer, M -- Stairs, I H -- Manchester, R N -- McLaughlin, M A -- Lyne, A G -- Ferdman, R D -- Burgay, M -- Lorimer, D R -- Possenti, A -- D'Amico, N -- Sarkissian, J M -- Hobbs, G B -- Reynolds, J E -- Freire, P C C -- Camilo, F -- New York, N.Y. -- Science. 2006 Oct 6;314(5796):97-102. Epub 2006 Sep 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of Manchester, Jodrell Bank Observatory, Macclesfield SK11 9DL, UK. mkramer@jb.man.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16973838" 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〉