LIVIVO - Das Suchportal für Lebenswissenschaften

switch to English language
Erweiterte Suche

Ihre letzten Suchen

  1. AU="Lentati, L"
  2. AU="Cyriac, Sanju"
  3. AU="Axtmayer, Jossette"
  4. AU="Sato, Shusuke"
  5. AU="Debasis Mondal"
  6. AU="Hollingsworth, Neal A"
  7. AU=Restifo Nicholas P AU=Restifo Nicholas P
  8. AU="Farmer, Claire"
  9. AU="Hyeong, Seok-Ki"
  10. AU=Sathananthan A Henry
  11. AU="Ross D. Pollock"
  12. AU="Abouelkhair, Mohamed A"
  13. AU="Draia, Ahmed N"
  14. AU="Martins, Paulo"
  15. AU=Elliott P
  16. AU="Gill, J L"
  17. AU="Marmé, Dieter"
  18. AU=St John Ashley L
  19. AU="Macpherson, Catherine Fiona"
  20. AU=Malloy Giovanni S P
  21. AU="Bovino, Antonio"
  22. AU="Deseri, Luca"
  23. AU="Cunningham, C W"
  24. AU="Haas, Brian"
  25. AU="Raia, Anais"
  26. AU=Gollin Susanne M
  27. AU="Xie, Hong-Guang"
  28. AU="Ford, Paul Leicester"
  29. AU="Garver-Daniels, N. E."
  30. AU="De Pisapia, Nicola"
  31. AU="Inoue, Kazunori"
  32. AU="Tüzün, Funda"
  33. AU="McDonough, John"
  34. AU="Puche-Cañas, Emilio"
  35. AU="Rahim, Faraan O"
  36. AU="Barritt, Andrew W"

Suchergebnis

Treffer 1 - 7 von insgesamt 7

Suchoptionen

  1. Buch ; Online: Profile Stochasticity in PSR J1909-3744

    Lentati, L. / Shannon, R. M.

    2015  

    Abstract: We extend the recently introduced Bayesian framework `Generative Pulsar Timing Analysis' to incorporate both pulse jitter (high frequency variation in the arrival time of the pulse) and epoch to epoch stochasticity in the shape of the pulse profile. This ...

    Abstract We extend the recently introduced Bayesian framework `Generative Pulsar Timing Analysis' to incorporate both pulse jitter (high frequency variation in the arrival time of the pulse) and epoch to epoch stochasticity in the shape of the pulse profile. This framework allows for a full timing analysis to be performed on the folded profile data, rather than the site arrival times as is typical in most timing studies. We apply this extended framework both to simulations, and to an 11 yr, 10 cm data set for PSR J1909$-$3744. Using simulations, we show that temporal profile variation can induce timing noise in the residuals that when performing a standard timing analysis is highly covariant with the signal expected from a gravitational wave (GW) background. When working in the profile domain, these variations are de-correlated from the expected GW signal, resulting in significant improvement in the obtained upper limits. Using the PSR J1909$-$3744 data set from the Parkes Pulsar Timing Array project, we find significant evidence for systematic high-frequency profile variation resulting from non-Gaussian noise in the oldest observing system, but no evidence for either detectable pulse jitter, or low-frequency profile shape variation. Using our profile domain framework we therefore obtain upper limits on a red noise process with a spectral index of $\gamma = 13/3$ of $1\times10^{-15}$, consistent with previously published limits.

    Comment: 16 pages, 13 figures, 2 tables
    Schlagwörter Astrophysics - Instrumentation and Methods for Astrophysics
    Thema/Rubrik (Code) 612
    Erscheinungsdatum 2015-09-24
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Zusatzmaterialien

    Kategorien

  2. Buch ; Online: All correlations must die

    Taylor, S. R. / Lentati, L. / Babak, S. / Brem, P. / Gair, J. R. / Sesana, A. / Vecchio, A.

    Assessing the significance of a stochastic gravitational-wave background in pulsar-timing arrays

    2016  

    Abstract: We present two methods for determining the significance of a stochastic gravitational-wave (GW) background affecting a pulsar-timing array, where detection is based on evidence for quadrupolar spatial correlations between pulsars. Rather than ... ...

    Abstract We present two methods for determining the significance of a stochastic gravitational-wave (GW) background affecting a pulsar-timing array, where detection is based on evidence for quadrupolar spatial correlations between pulsars. Rather than constructing noise simulations, we eliminate the GWB spatial correlations in the true datasets to assess detection significance with all real data features intact. In our first method, we perform random phase shifts in the signal-model basis functions. This phase shifting eliminates signal phase coherence between pulsars, while keeping the statistical properties of the pulsar timing residuals intact. We then explore a method to null correlations between pulsars by using a "scrambled" overlap-reduction function in the signal model for the array. This scrambled function is orthogonal to what we expect of a real GW background signal. We demonstrate the efficacy of these methods using Bayesian model selection on a set of simulated datasets that contain a stochastic GW signal, timing noise, undiagnosed glitches, and uncertainties in the Solar system ephemeris. Finally, we introduce an overarching formalism under which these two techniques are naturally linked. These methods are immediately applicable to all current pulsar-timing array datasets, and should become standard tools for future analyses.

    Comment: 14 pages, 8 figures, 1 table. Updated to match published version
    Schlagwörter Astrophysics - Instrumentation and Methods for Astrophysics ; General Relativity and Quantum Cosmology ; High Energy Physics - Experiment
    Thema/Rubrik (Code) 612
    Erscheinungsdatum 2016-06-29
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Zusatzmaterialien

    Kategorien

  3. Buch ; Online: TempoNest

    Lentati, Lindley / Alexander, Paul / Hobson, Michael P. / Feroz, Farhan / van Haasteren, Rutger / Lee, Kejia / Shannon, Ryan M.

    A Bayesian approach to pulsar timing analysis

    2013  

    Abstract: A new Bayesian software package for the analysis of pulsar timing data is presented in the form of TempoNest which allows for the robust determination of the non-linear pulsar timing solution simultaneously with a range of additional stochastic ... ...

    Abstract A new Bayesian software package for the analysis of pulsar timing data is presented in the form of TempoNest which allows for the robust determination of the non-linear pulsar timing solution simultaneously with a range of additional stochastic parameters. This includes both red spin noise and dispersion measure variations using either power law descriptions of the noise, or through a model-independent method that parameterises the power at individual frequencies in the signal. We use TempoNest to show that at noise levels representative of current datasets in the European Pulsar Timing Array (EPTA) and International Pulsar Timing Array (IPTA) the linear timing model can underestimate the uncertainties of the timing solution by up to an order of magnitude. We also show how to perform Bayesian model selection between different sets of timing model and stochastic parameters, for example, by demonstrating that in the pulsar B1937+21 both the dispersion measure variations and spin noise in the data are optimally modelled by simple power laws. Finally we show that not including the stochastic parameters simultaneously with the timing model can lead to unpredictable variation in the estimated uncertainties, compromising the robustness of the scientific results extracted from such analysis.

    Comment: 21 pages, 12 Figures
    Schlagwörter Astrophysics - Instrumentation and Methods for Astrophysics ; Astrophysics - Astrophysics of Galaxies
    Thema/Rubrik (Code) 612
    Erscheinungsdatum 2013-10-08
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Zusatzmaterialien

    Kategorien

  4. Artikel ; Online: Limits on Anisotropy in the Nanohertz Stochastic Gravitational Wave Background.

    Taylor, S R / Mingarelli, C M F / Gair, J R / Sesana, A / Theureau, G / Babak, S / Bassa, C G / Brem, P / Burgay, M / Caballero, R N / Champion, D J / Cognard, I / Desvignes, G / Guillemot, L / Hessels, J W T / Janssen, G H / Karuppusamy, R / Kramer, M / Lassus, A /
    Lazarus, P / Lentati, L / Liu, K / Osłowski, S / Perrodin, D / Petiteau, A / Possenti, A / Purver, M B / Rosado, P A / Sanidas, S A / Smits, R / Stappers, B / Tiburzi, C / van Haasteren, R / Vecchio, A / Verbiest, J P W

    Physical review letters

    2015  Band 115, Heft 4, Seite(n) 41101

    Abstract: The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses suboptimal. We present the first constraints on the angular ... ...

    Abstract The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses suboptimal. We present the first constraints on the angular distribution of a nanohertz stochastic GWB from circular, inspiral-driven SMBHBs using the 2015 European Pulsar Timing Array data. Our analysis of the GWB in the ~2-90 nHz band shows consistency with isotropy, with the strain amplitude in l>0 spherical harmonic multipoles ≲40% of the monopole value. We expect that these more general techniques will become standard tools to probe the angular distribution of source populations.
    Sprache Englisch
    Erscheinungsdatum 2015-07-24
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.115.041101
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

  5. Artikel ; Online: Gravitational waves from binary supermassive black holes missing in pulsar observations.

    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 / Osłowski, S / Reardon, D J / van Straten, W / Toomey, L / Wang, J-B /
    Wen, L / Wyithe, J S B / Zhu, X-J

    Science (New York, N.Y.)

    2015  Band 349, Heft 6255, Seite(n) 1522–1525

    Abstract: 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. ...

    Abstract 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 × 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.
    Sprache Englisch
    Erscheinungsdatum 2015-09-25
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.aab1910
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

  6. Artikel ; Online: The intense starburst HDF 850.1 in a galaxy overdensity at z ≈ 5.2 in the Hubble Deep Field.

    Walter, Fabian / Decarli, Roberto / Carilli, Chris / Bertoldi, Frank / Cox, Pierre / Da Cunha, Elisabete / Daddi, Emanuele / Dickinson, Mark / Downes, Dennis / Elbaz, David / Ellis, Richard / Hodge, Jacqueline / Neri, Roberto / Riechers, Dominik A / Weiss, Axel / Bell, Eric / Dannerbauer, Helmut / Krips, Melanie / Krumholz, Mark /
    Lentati, Lindley / Maiolino, Roberto / Menten, Karl / Rix, Hans-Walter / Robertson, Brant / Spinrad, Hyron / Stark, Dan P / Stern, Daniel

    Nature

    2012  Band 486, Heft 7402, Seite(n) 233–236

    Abstract: The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time. An early map of the Hubble Deep Field at a wavelength of 850 micrometres, ... ...

    Abstract The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time. An early map of the Hubble Deep Field at a wavelength of 850 micrometres, which is sensitive to dust emission powered by star formation, revealed the brightest source in the field, dubbed HDF 850.1 (ref. 2). For more than a decade, and despite significant efforts, no counterpart was found at shorter wavelengths, and it was not possible to determine its redshift, size or mass. Here we report a redshift of z = 5.183 for HDF 850.1, from a millimetre-wave molecular line scan. This places HDF 850.1 in a galaxy overdensity at z ≈ 5.2, corresponding to a cosmic age of only 1.1 billion years after the Big Bang. This redshift is significantly higher than earlier estimates and higher than those of most of the hundreds of submillimetre-bright galaxies identified so far. The source has a star-formation rate of 850 solar masses per year and is spatially resolved on scales of 5 kiloparsecs, with an implied dynamical mass of about 1.3 × 10(11) solar masses, a significant fraction of which is present in the form of molecular gas. Despite our accurate determination of redshift and position, a counterpart emitting starlight remains elusive.
    Sprache Englisch
    Erscheinungsdatum 2012-06-13
    Erscheinungsland England
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 120714-3
    ISSN 1476-4687 ; 0028-0836
    ISSN (online) 1476-4687
    ISSN 0028-0836
    DOI 10.1038/nature11073
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

  7. Buch ; Online: The International Pulsar Timing Array

    Verbiest, J. P. W. / Lentati, L. / Hobbs, G. / van Haasteren, R. / Demorest, P. B. / Janssen, G. H. / Wang, J. -B. / Desvignes, G. / Caballero, R. N. / Keith, M. J. / Champion, D. J. / Arzoumanian, Z. / Babak, S. / Bassa, C. G. / Bhat, N. D. R. / Brazier, A. / Brem, P. / Burgay, M. / Burke-Spolaor, S. /
    Chamberlin, S. J. / Chatterjee, S. / Christy, B. / Cognard, I. / Cordes, J. M. / Dai, S. / Dolch, T. / Ellis, J. A. / Ferdman, R. D. / Fonseca, E. / Gair, J. R. / Garver-Daniels, N. E. / Gentile, P. / Gonzalez, M. E. / Graikou, E. / Guillemot, L. / Hessels, J. W. T. / Jones, G. / Karuppusamy, R. / Kerr, M. / Kramer, M. / Lam, M. T. / Lasky, P. D. / Lassus, A. / Lazarus, P. / Lazio, T. J. W. / Lee, K. J. / Levin, L. / Liu, K. / Lynch, R. S. / Lyne, A. G. / Mckee, J. / McLaughlin, M. A. / McWilliams, S. T. / Madison, D. R. / Manchester, R. N. / Mingarelli, C. M. F. / Nice, D. J. / Oslowski, S. / Palliyaguru, N. T. / Pennucci, T. T. / Perera, B. B. P. / Perrodin, D. / Possenti, A. / Petiteau, A. / Ransom, S. M. / Reardon, D. / Rosado, P. A. / Sanidas, S. A. / Sesana, A. / Shaifullah, G. / Shannon, R. M. / Siemens, X. / Simon, J. / Smits, R. / Spiewak, R. / Stairs, I. H. / Stappers, B. W. / Stinebring, D. R. / Stovall, K. / Swiggum, J. K. / Taylor, S. R. / Theureau, G. / Tiburzi, C. / Toomey, L. / Vallisneri, M. / van Straten, W. / Vecchio, A. / Wang, Y. / Wen, L. / You, X. P. / Zhu, W. W. / Zhu, X. -J.

    First Data Release

    2016  

    Abstract: The highly stable spin of neutron stars can be exploited for a variety of (astro-)physical investigations. In particular arrays of pulsars with rotational periods of the order of milliseconds can be used to detect correlated signals such as those caused ... ...

    Abstract The highly stable spin of neutron stars can be exploited for a variety of (astro-)physical investigations. In particular arrays of pulsars with rotational periods of the order of milliseconds can be used to detect correlated signals such as those caused by gravitational waves. Three such "Pulsar Timing Arrays" (PTAs) have been set up around the world over the past decades and collectively form the "International" PTA (IPTA). In this paper, we describe the first joint analysis of the data from the three regional PTAs, i.e. of the first IPTA data set. We describe the available PTA data, the approach presently followed for its combination and suggest improvements for future PTA research. Particular attention is paid to subtle details (such as underestimation of measurement uncertainty and long-period noise) that have often been ignored but which become important in this unprecedentedly large and inhomogeneous data set. We identify and describe in detail several factors that complicate IPTA research and provide recommendations for future pulsar timing efforts. The first IPTA data release presented here (and available online) is used to demonstrate the IPTA's potential of improving upon gravitational-wave limits placed by individual PTAs by a factor of ~2 and provides a 2-sigma limit on the dimensionless amplitude of a stochastic GWB of 1.7x10^{-15} at a frequency of 1 yr^{-1}. This is 1.7 times less constraining than the limit placed by (Shannon et al. 2015), due mostly to the more recent, high-quality data they used.

    Comment: 25 pages, 6 tables, 5 figures. Accepted for publication in MNRAS
    Schlagwörter Astrophysics - Instrumentation and Methods for Astrophysics
    Thema/Rubrik (Code) 333
    Erscheinungsdatum 2016-02-11
    Erscheinungsland us
    Dokumenttyp Buch ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Zusatzmaterialien

    Kategorien

Zum Seitenanfang