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1. Accuracy, reproducibility, and uncertainty analysis of thyroid-probe-based activity measurements for determination of dose calibrator settings

Author

Marjorie Gonzalez, Anna Celler, Jesse Tanguay, Pedro L. Esquinas, Urs O. Häfeli, Milan Vuckovic, and Cristina Rodríguez-Rodríguez

Subjects
Physics, Reproducibility, Dose Calibrator, business.industry, Calibration curve, Coefficient of variation, General Medicine, 3. Good health, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, 0302 clinical medicine, 030220 oncology & carcinogenesis, Ionization chamber, Calibration, Dosimetry, Nuclear medicine, business, Uncertainty analysis
Abstract

Purpose: In the nuclear medicine department, the activity of radiopharmaceuticals is measured using dose calibrators (DCs) prior to patient injection. The DC consists of an ionization chamber that measures current generated by ionizing radiation (emitted from the radiotracer). In order to obtain an activity reading, the current is converted into units of activity by applying an appropriate calibration factor (also referred to as DC dial setting). Accurate determination of DC dial settings is crucial to ensure that patients receive the appropriate dose in diagnostic scans or radionuclide therapies. The goals of this study were (1) to describe a practical method to experimentally determine dose calibrator settings using a thyroid-probe (TP) and (2) to investigate the accuracy, reproducibility, and uncertainties of the method. As an illustration, the TP method was applied to determine 188Re dial settings for two dose calibrator models: Atomlab 100plus and Capintec CRC-55tR. Methods: Using the TP to determine dose calibrator settings involved three measurements. First, the energy-dependent efficiency of the TP was determined from energy spectra measurements of two calibration sources (152Eu and 22Na). Second, the gamma emissions from the investigated isotope (188Re) were measured using the TP and its activity was determined using γ-ray spectroscopy methods. Ambient background, scatter, and source-geometry corrections were applied during the efficiency and activity determination steps. Third, the TP-based 188Re activity was used to determine the dose calibrator settings following the calibration curve method [B. E. Zimmerman et al., J. Nucl. Med. 40, 1508–1516 (1999)]. The interobserver reproducibility of TP measurements was determined by the coefficient of variation (COV) and uncertainties associated to each step of the measuring process were estimated. The accuracy of activity measurements using the proposed method was evaluated by comparing the TP activity estimates of 99mTc, 188Re, 131I, and 57Co samples to high purity Ge (HPGe) γ-ray spectroscopy measurements. Results: The experimental 188Re dial settings determined with the TP were 76.5 ± 4.8 and 646 ± 43 for Atomlab 100plus and Capintec CRC-55tR, respectively. In the case of Atomlab 100plus, the TP-based dial settings improved the accuracy of 188Re activity measurements (confirmed by HPGe measurements) as compared to manufacturer-recommended settings. For Capintec CRC-55tR, the TP-based settings were in agreement with previous results [B. E. Zimmerman et al., J. Nucl. Med. 40, 1508–1516 (1999)] which demonstrated that manufacturer-recommended settings overestimate 188Re activity by more than 20%. The largest source of uncertainty in the experimentally determined dial settings was due to the application of a geometry correction factor, followed by the uncertainty of the scatter-corrected photopeak counts and the uncertainty of the TP efficiency calibration experiment. When using the most intense photopeak of the sample's emissions, the TP method yielded accurate (within 5% errors) and reproducible (COV = 2%) measurements of sample's activity. The relative uncertainties associated with such measurements ranged from 6% to 8% (expanded uncertainty at 95% confidence interval, k = 2). Conclusions: Accurate determination/verification of dose calibrator dial settings can be performed using a thyroid-probe in the nuclear medicine department.

Published
2016
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2. Characteristics of Bremsstrahlung emissions of 177 Lu, 188 Re, and 90 Y for SPECT/CT quantification in radionuclide therapy

Author

Marjorie Gonzalez, Anna Celler, Pedro L. Esquinas, and Carlos Uribe

Subjects
Single Photon Emission Computed Tomography Computed Tomography, Monte Carlo method, Biophysics, General Physics and Astronomy, Lutetium, Single-photon emission computed tomography, Imaging phantom, 030218 nuclear medicine & medical imaging, law.invention, Nuclear physics, 03 medical and health sciences, 0302 clinical medicine, law, Beta particle, medicine, Humans, Computer Simulation, Yttrium Radioisotopes, Radiology, Nuclear Medicine and imaging, Radioisotopes, Physics, medicine.diagnostic_test, Phantoms, Imaging, Bremsstrahlung, Water, Collimator, General Medicine, Rhenium, Positron emission tomography, Positron-Emission Tomography, 030220 oncology & carcinogenesis, Radionuclide therapy, Monte Carlo Method
Abstract

Purpose Beta particles emitted by radioisotopes used in targeted radionuclide therapies (TRT) create Bremsstrahlung (BRS) which may affect SPECT quantification when imaging these isotopes. The purpose of the current study was to investigate the characteristics of Bremsstrahlung produced in tissue by three β-emitting radioisotopes used in TRT. Methods Monte Carlo simulations of 177 Lu, 188 Re, and 90 Y sources placed in water filled cylinders were performed. BRS yields, mean energies and energy spectra for (a) all photons generated in the decays, (b) photons that were not absorbed and leave the cylinder, and (c) photons detected by the camera were analyzed. Next, the results of simulations were compared with those from experiments performed on a clinical SPECT camera using same acquisition conditions and phantom configurations as in simulations. Results Simulations reproduced relatively well the shapes of the measured spectra, except for 90 Y which showed an overestimation in the low energy range. Detailed analysis of the results allowed us to suggest best collimators and imaging conditions for each of the investigated isotopes. Finally, our simulations confirmed that the BRS contribution to the energy spectra in quantitative imaging of 177 Lu and 188 Re could be ignored. Conclusions For 177 Lu and 188 Re, BRS contributes only marginally to the total spectra recorded by the camera. Our analysis shows that MELP and HE collimators are the best for imaging these two isotopes. For 90 Y, HE collimator should be used.

Published
2016
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3. Tests of gravitational symmetries with pulsar binary J1713+0747

Author

Michael Kramer, Kang Liu, Robert D. Ferdman, Lina Levin, P. Lazarus, Marjorie Gonzalez, Michael T. Lam, Gemma H. Janssen, Kejia Lee, Timothy Dolch, Norbert Wex, Scott M. Ransom, Kathryn Crowter, A. Jessner, Ramesh Karuppusamy, J. K. Swiggum, Andrew Lyne, K. Lazaridis, M. L. Jones, Gregory Desvignes, J. W. McKee, Gilles Theureau, Ismaël Cognard, R. Smits, Maura McLaughlin, A. Krieger, Weiwei Zhu, M. Burgay, D. J. Champion, Timothy T. Pennucci, Delphine Perrodin, Caterina Tiburzi, L. Lentati, Kevin Stovall, Joris P. W. Verbiest, A. Possenti, Christine Jordan, Glenn Jones, G. Shaifullah, E. Graikou, J. A. Ellis, David J. Nice, R. N. Caballero, Ingrid H. Stairs, Stefan Oslowski, Jason W. T. Hessels, C. G. Bassa, Emmanuel Fonseca, Benjamin Stappers, S. A. Sanidas, Zaven Arzoumanian, Lucas Guillemot, Paul Demorest, High Energy Astrophys. & Astropart. Phys (API, FNWI), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Centre National de la Recherche Scientifique ( CNRS ) -Université d'Orléans ( UO ) -Institut national des sciences de l'Univers ( INSU - CNRS ), Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Univers et Théories ( LUTH ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Zhu, W, Desvignes, G, Wex, N, Caballero, R, Champion, D, Demorest, P, Ellis, J, Janssen, G, Kramer, M, Krieger, A, Lentati, L, Nice, D, Ransom, S, Stairs, I, Stappers, B, Verbiest, J, Arzoumanian, Z, Bassa, C, Burgay, M, Cognard, I, Crowter, K, Dolch, T, Ferdman, R, Fonseca, E, Gonzalez, M, Graikou, E, Guillemot, L, Hessels, J, Jessner, A, Jones, G, Jones, M, Jordan, C, Karuppusamy, R, Lam, M, Lazaridis, K, Lazarus, P, Lee, K, Levin, L, Liu, K, Lyne, A, Mckee, J, Mclaughlin, M, Osłowski, S, Pennucci, T, Perrodin, D, Possenti, A, Sanidas, S, Shaifullah, G, Smits, R, Stovall, K, Swiggum, J, Theureau, G, Tiburzi, C, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
General relativity, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astronomy, FOS: Physical sciences, Astrophysics, Lorentz covariance, 01 natural sciences, Binary pulsar, Gravitation, stars: neutron, General Relativity and Quantum Cosmology, Pulsar, Gravitational field, 0103 physical sciences, pulsars: individual (PSR J1713+0747), 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy and Astrophysics, Gravitational constant, European Pulsar Timing Array, binaries: general, Space and Planetary Science, [SDU]Sciences of the Universe [physics], gravitation, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Symmetries play an important role in modern theories of gravity. The strong equivalence principle (SEP) constitutes a collection of gravitational symmetries which are all implemented by general relativity. Alternative theories, however, are generally expected to violate some aspects of SEP. We test three aspects of SEP using observed change rates in the orbital period and eccentricity of binary pulsar J1713+0747: 1. the gravitational constant's constancy as part of locational invariance of gravitation; 2. the post-Newtonian parameter $\hat{\alpha}_3$ in gravitational Lorentz invariance; 3. the universality of free fall (UFF) for strongly self-gravitating bodies. Based on the pulsar timing result of the combined dataset from the North American Nanohertz Gravitational Observatory (NANOGrav) and the European Pulsar Timing Array (EPTA), we find $\dot{G}/G = (-0.1 \pm 0.9) \times 10^{-12}\,{\rm yr}^{-1}$, which is weaker than Solar system limits, but applies for strongly self-gravitating objects. Furthermore, we obtain the constraints $|\Delta|< 0.002$ for the UFF test and $-3\times10^{-20} < \hat{\alpha}_3 < 4\times10^{-20}$ at 95% confidence. These are the first direct UFF and $\hat{\alpha}_3$ tests based on pulsar binaries, and they overcome various limitations of previous tests., Comment: 11 pages, 6 figures, and 1 table; submitted to MNRAS

Published
2019
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4. Determination of gamma camera calibration factors for quantitation of therapeutic radioisotopes

Author

Marjorie Gonzalez, Yuni K. Dewaraja, Xinchi Hou, Anna Celler, Carlos Uribe, Jean-Mathieu Beauregard, Wei Zhao, and Pedro L. Esquinas

Subjects
lcsh:Medical physics. Medical radiology. Nuclear medicine, Point source, lcsh:R895-920, Monte Carlo method, Biomedical Engineering, Gamma camera calibration, Imaging phantom, 030218 nuclear medicine & medical imaging, law.invention, 03 medical and health sciences, 0302 clinical medicine, law, Spect imaging, Quantification, Calibration, Radiology, Nuclear Medicine and imaging, Iodine-131, Instrumentation, Gamma camera, Original Research, Physics, Radiation, business.industry, Rhenium-188, 030220 oncology & carcinogenesis, TEW, Lutetium-177, Nuclear medicine, business, Correction for attenuation, Camera resectioning
Abstract

Background: Camera calibration, which translates reconstructed count map into absolute activity map, is a prerequisite procedure for quantitative SPECT imaging. Both planar and tomographic scans using different phantom geometries have been proposed for the determination of the camera calibration factor (CF). However, there is no consensus on which approach is the best. The aim of this study is to evaluate all these calibration methods, compare their performance, and propose a practical and accurate calibration method for SPECT quantitation of therapeutic radioisotopes. Twenty-one phantom experiments (Siemens Symbia SPECT/CT) and 12 Monte Carlo simulations (GATE v6.1) using three therapy isotopes (131I, 177Lu, and 188Re) have been performed. The following phantom geometries were used: (1) planar scans of point source in air (PS), (2) tomographic scans of insert(s) filled with activity placed in non-radioactive water (HS + CB), (3) tomographic scans of hot insert(s) in radioactive water (HS + WB), and (4) tomographic scans of cylinders uniformly filled with activity (HC). Tomographic data were reconstructed using OSEM with CT-based attenuation correction and triple energy window (TEW) scatter correction, and CF was determined using total counts in the reconstructed image, while for planar scans, the photopeak counts, corrected for scatter and background with TEW, were used. Additionally, for simulated data, CF obtained from primary photons only was analyzed. Results: For phantom experiments, CF obtained from PS and HS + WB agreed to within 6% (below 3% if experiments performed on the same day are considered). However, CF from HS + CB exceeded those from PS by 4–12%. Similar trend was found in simulation studies. Analysis of CFs from primary photons helped us to understand this discrepancy. It was due to underestimation of scatter by the TEW method, further enhanced by attenuation correction. This effect becomes less important when the source is distributed over the entire phantom volume (HS + WB and HC). Conclusions: Camera CF could be determined using planar scans of a point source, provided that the scatter and background contributions are removed, for example using the clinically available TEW method. This approach is simple and yet provides CF with sufficient accuracy (~ 5%) to be used in clinics for radiotracer quantification.

Published
2018

5. From spin noise to systematics: stochastic processes in the first International Pulsar Timing Array data release

Author

R. van Haasteren, Scott M. Ransom, S. Babak, Antoine Petiteau, Paul Demorest, L. Toomey, Gemma H. Janssen, Alberto Sesana, Marjorie Gonzalez, Sourav Chatterjee, A. Lassus, Ryan Shannon, Justin A. Ellis, Glenn Jones, E. Graikou, J. W. McKee, Kang Liu, Kejia Lee, Matthew Kerr, Sarah Burke-Spolaor, William A. Coles, Maura McLaughlin, G. Shaifullah, Stephen Taylor, Weiwei Zhu, P. Lazarus, S. A. Sanidas, D. J. Champion, Delphine Perrodin, R. N. Caballero, Kevin Stovall, Joris P. W. Verbiest, Benetge Perera, Richard N. Manchester, C. G. Bassa, Emmanuel Fonseca, Jonathan R. Gair, George Hobbs, D. R. Madison, R. Smits, Alberto Vecchio, Daniel R. Stinebring, Michael T. Lam, Daniel J. Reardon, X. P. You, Zaven Arzoumanian, Paul D. Lasky, Yue-Fei Wang, Lucas Guillemot, R. S. Lynch, Pablo Rosado, Lina Levin, Xing-Jiang Zhu, Chiara M. F. Mingarelli, L. Lentati, Benjamin Stappers, A. Possenti, T. J. W. Lazio, Robert D. Ferdman, Stefan Oslowski, J. K. Swiggum, X. Siemens, Gregory Desvignes, Gilles Theureau, Ramesh Karuppusamy, Ismaël Cognard, M. Burgay, Timothy T. Pennucci, Michele Vallisneri, J. B. Wang, James M. Cordes, Sean T. McWilliams, David J. Nice, P. Brem, W. van Straten, Caterina Tiburzi, N. D. R. Bhat, Shi Dai, Jason W. T. Hessels, Ingrid H. Stairs, Timothy Dolch, Michael Kramer, Michael Keith, Lentati, L, Shannon, R, Coles, W, Verbiest, J, van Haasteren, R, Ellis, J, Caballero, R, Manchester, R, Arzoumanian, Z, Babak, S, Bassa, C, Bhat, N, Brem, P, Burgay, M, Burke-Spolaor, S, Champion, D, Chatterjee, S, Cognard, I, Cordes, J, Dai, S, Demorest, P, Desvignes, G, Dolch, T, Ferdman, R, Fonseca, E, Gair, J, Gonzalez, M, Graikou, E, Guillemot, L, Hessels, J, Hobbs, G, Janssen, G, Jones, G, Karuppusamy, R, Keith, M, Kerr, M, Kramer, M, Lam, M, Lasky, P, Lassus, A, Lazarus, P, Lazio, T, Lee, K, Levin, L, Liu, K, Lynch, R, Madison, D, Mckee, J, Mclaughlin, M, Mcwilliams, S, Mingarelli, C, Nice, D, Osłowski, S, Pennucci, T, Perera, B, Perrodin, D, Petiteau, A, Possenti, A, Ransom, S, Reardon, D, Rosado, P, Sanidas, S, Sesana, A, Shaifullah, G, Siemens, X, Smits, R, Stairs, I, Stappers, B, Stinebring, D, Stovall, K, Swiggum, J, Taylor, S, Theureau, G, Tiburzi, C, Toomey, L, Vallisneri, M, van Straten, W, Vecchio, A, Wang, J, Wang, Y, You, X, Zhu, W, Zhu, X, High Energy Astrophys. & Astropart. Phys (API, FNWI), Cavendish Laboratory, University of Cambridge [UK] (CAM), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of California, University of California (UC), Max-Planck-Institut für Radioastronomie (MPIFR), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft, Netherlands Institute for Radio Astronomy (ASTRON), Curtin University [Perth], Planning and Transport Research Centre (PATREC), INAF - Osservatorio Astronomico di Cagliari (OAC), Istituto Nazionale di Astrofisica (INAF), National Radio Astronomy Observatory (NRAO), Center for Radiophysics and Space Research [Ithaca] (CRSR), Cornell University [New York], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Department of Astronomy [Ithaca], Department of Physics, Hillsdale College, Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), University of British Columbia (UBC), Vancouver Coastal Health, Department of Nuclear Medicine, Netherlands Institute for Radio Astronomy ( ASTRON ), ARC Centre of Excellence for Coral Reef Studies (CoralCoE), James Cook University (JCU), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], National Radio Astronomy Observatory [Green Bank] (NRAO), Jodrell Bank Centre for Astrophysics (JBCA), Department of Physics, West Virginia University, West Virginia University, Theoretical Astrophysics [Pasadena] (TAPIR), California Institute of Technology (CALTECH), Physics Department, Lafayette College, Lafayette College [Easton], Department of Astronomy [Charlottesville], University of Virginia, APC - Gravitation (APC-Gravitation), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Anton Pannekoek Institute for Astronomy, University of Amsterdam [Amsterdam] (UvA), University of Wisconsin - Milwaukee, Department of Physics and Astronomy, University of British Columbia, Department of Physics and Astronomy [Oberlin], Oberlin College, Institute of Meteoritics [Albuquerque] (IOM), The University of New Mexico [Albuquerque], Department of Physics and Astronomy, West Virginia University, West Virginia University [Morgantown], Birmingham City University (BCU), Xinjiang Astronomical Observatory, Chinese Academy of Sciences [Beijing] (CAS), Huazhong University of Science and Technology [Wuhan] (HUST), School of Physical Science and Technology, Southwest University [Chongqing], Australian Research Council Discovery Project DP140102578NASA through Einstein Fellowship grant PF3-140116West Light Foundation of CAS XBBS201322 and NSFC project no.11403086National Science Fundation of China (NSFC) award number 11503007NNSF of China (U1231120) and FRFCU (XDJK2015B012), European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), European Project: 227947,EC:FP7:ERC,ERC-2008-AdG,LEAP(2009), European Project: 610058,EC:FP7:ERC,ERC-2013-SyG,BLACKHOLECAM(2014), Cornell University, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Division of Physics, Mathematics and Astronomy [Pasadena], California Institute of Technology (CALTECH)-California Institute of Technology (CALTECH), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), California Institute of Technology (CALTECH)-NASA, Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Virginia [Charlottesville], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, data analysis, pulsars: general [methods], FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Methods: Data analysi, Astrophysics, Astronomy & Astrophysics, general [pulsars], 01 natural sciences, General Relativity and Quantum Cosmology, pulsars:individual, Binary pulsar, Pulsar, 0103 physical sciences, data analysis [methods], Coherence (signal processing), Sensitivity (control systems), Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Stochastic process, Noise (signal processing), Model selection, Pulsars: General, Astronomy and Astrophysics, methods: data analysis, LIGO, Computational physics, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astronomical and Space Sciences
Abstract

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 PTA data sets. For example, we show that PSR J1643$-$1224 has, in addition to DM variations, significant band-dependent noise that is coherent between PTAs which we interpret as coming from time-variable scattering or refraction in the ionised interstellar medium. Failing to model these different contributions appropriately can dramatically alter the astrophysical interpretation of the stochastic signals observed in the residuals. In some cases, the spectral exponent of the spin noise signal can vary from 1.6 to 4 depending upon the model, which has direct implications for the long-term sensitivity of the pulsar to a stochastic gravitational-wave (GW) background. By using a more appropriate model, however, we can greatly improve a pulsar's sensitivity to GWs. For example, including system and band-dependent signals in the PSR J0437$-$4715 data set improves the upper limit on a fiducial GW background by $\sim 60\%$ compared to a model that includes DM variations and spin-noise only., Comment: 29 pages. 16 figures. Accepted for publication in MNRAS

Published
2016
Full Text
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6. The International Pulsar Timing Array: First data release

Author

Lucas Guillemot, Sourav Chatterjee, N. Garver-Daniels, D. R. Madison, Scott M. Ransom, J. K. Swiggum, Daniel R. Stinebring, Delphine Perrodin, Ingrid H. Stairs, Alberto Vecchio, Timothy Dolch, X. Siemens, Gregory Desvignes, Antoine Petiteau, Gilles Theureau, W. van Straten, J. B. Wang, X. P. You, Jason W. T. Hessels, Renée Spiewak, R. N. Caballero, Alberto Sesana, Stefan Oslowski, R. S. Lynch, Xing-Jiang Zhu, C. G. Bassa, Emmanuel Fonseca, Daniel J. Reardon, Yue-Fei Wang, Chiara M. F. Mingarelli, Benjamin Stappers, Kejia Lee, Stanislav Babak, Benetge Perera, Pablo Rosado, Zaven Arzoumanian, Richard N. Manchester, Paul Demorest, A. Brazier, Jonathan R. Gair, R. van Haasteren, Nipuni Palliyaguru, Lina Levin, R. Smits, Joseph Simon, P. Brem, Michele Vallisneri, Michael Kramer, James M. Cordes, Andrew Lyne, L. Lentati, Weiwei Zhu, Matthew Kerr, Peter A. Gentile, Michael Keith, A. Possenti, D. J. Champion, Caterina Tiburzi, T. J. W. Lazio, N. D. R. Bhat, A. Lassus, Stephen Taylor, Linqing Wen, Ryan Shannon, Glenn Jones, Shi Dai, E. Graikou, Gemma H. Janssen, S. J. Chamberlin, Kevin Stovall, Kang Liu, P. Lazarus, Ramesh Karuppusamy, S. A. Sanidas, Ismaël Cognard, George Hobbs, Robert D. Ferdman, Timothy T. Pennucci, M. Burgay, Sean T. McWilliams, David J. Nice, B. Christy, G. Shaifullah, L. Toomey, Justin A. Ellis, J. W. McKee, Maura McLaughlin, Paul D. Lasky, Michael T. Lam, Sarah Burke-Spolaor, Joris P. W. Verbiest, Marjorie Gonzalez, High Energy Astrophys. & Astropart. Phys (API, FNWI), Verbiest, J, Lentati, L, Hobbs, G, van Haasteren, R, Demorest, P, Janssen, G, Wang, J, Desvignes, G, Caballero, R, Keith, M, Champion, D, Arzoumanian, Z, Babak, S, Bassa, C, Bhat, N, Brazier, A, Brem, P, Burgay, M, Burke-Spolaor, S, Chamberlin, S, Chatterjee, S, Christy, B, Cognard, I, Cordes, J, Dai, S, Dolch, T, Ellis, J, Ferdman, R, Fonseca, E, Gair, J, Garver-Daniels, N, Gentile, P, Gonzalez, M, Graikou, E, Guillemot, L, Hessels, J, Jones, G, Karuppusamy, R, Kerr, M, Kramer, M, Lam, M, Lasky, P, Lassus, A, Lazarus, P, Lazio, T, Lee, K, Levin, L, Liu, K, Lynch, R, Lyne, A, Mckee, J, Mclaughlin, M, Mcwilliams, S, Madison, D, Manchester, R, Mingarelli, C, Nice, D, Osłowski, S, Palliyaguru, N, Pennucci, T, Perera, B, Perrodin, D, Possenti, A, Petiteau, A, Ransom, S, Reardon, D, Rosado, P, Sanidas, S, Sesana, A, Shaifullah, G, Shannon, R, Siemens, X, Simon, J, Smits, R, Spiewak, R, Stairs, I, Stappers, B, Stinebring, D, Stovall, K, Swiggum, J, Taylor, S, Theureau, G, Tiburzi, C, Toomey, L, Vallisneri, M, van Straten, W, Vecchio, A, Wang, Y, Wen, L, You, X, Zhu, W, Zhu, X, Max-Planck-Institut für Radioastronomie (MPIFR), Cavendish Laboratory, University of Cambridge [UK] (CAM), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), National Radio Astronomy Observatory [Socorro] (NRAO), National Radio Astronomy Observatory (NRAO), Netherlands Institute for Radio Astronomy (ASTRON), Xinjiang Astronomical Observatory, Chinese Academy of Sciences [Beijing] (CAS), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], NASA Goddard Space Flight Center (GSFC), Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft, Curtin University [Perth], Planning and Transport Research Centre (PATREC), Cornell Center for Astrophysics and Planetary Science (CCAPS), Cornell University [New York], INAF - Osservatorio Astronomico di Cagliari (OAC), Istituto Nazionale di Astrofisica (INAF), Pennsylvania State University (Penn State), Penn State System, Center for Radiophysics and Space Research [Ithaca] (CRSR), University of Maryland [College Park], University of Maryland System, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Department of Astronomy [Ithaca], Department of Physics, Hillsdale College, University of British Columbia (UBC), University of Edinburgh, Department of Physics and Astronomy, West Virginia University, West Virginia University [Morgantown], Vancouver Coastal Health, Department of Nuclear Medicine, Department of Physics, Columbia University, Columbia University [New York], Monash Centre for Astrophysics (MoCA), Monash University [Clayton], Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], National Radio Astronomy Observatory [Green Bank] (NRAO), Theoretical Astrophysics [Pasadena] (TAPIR), Division of Physics, Mathematics and Astronomy [Pasadena], California Institute of Technology (CALTECH)-California Institute of Technology (CALTECH), Physics Department, Lafayette College, Lafayette College [Easton], Physics Department, Texas Tech University, Texas Tech University [Lubbock] (TTU), Department of Astronomy [Charlottesville], University of Virginia [Charlottesville], APC - Gravitation (APC-Gravitation), AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Anton Pannekoek Institute for Astronomy, University of Amsterdam [Amsterdam] (UvA), University of Wisconsin - Milwaukee, Center for Gravitation, Cosmology and Astrophysics, Netherlands Institute for Radio Astronomy ( ASTRON ), Department of Physics and Astronomy, University of British Columbia, Department of Physics and Astronomy [Oberlin], Oberlin College, Department of Physics and Astronomy [Albuquerque], The University of New Mexico [Albuquerque], Birmingham City University (BCU), School of Physics [HUST], Huazhong University of Science and Technology [Wuhan] (HUST), School of Physics (University of Western Australia), Université, School of Physical Science and Technology, Southwest University [Chongqing], European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), Max-Planck-Institut für Radioastronomie, Cavendish Laboratory - University of Cambridge, University of Cambridge [UK] ( CAM ), CSIRO Astronomy and Space Science, PO BOX 76, NSW 1710, Australia, Jet Propulsion Laboratory ( JPL ), NASA-California Institute of Technology ( CALTECH ), National Radio Astronomy Observatory [Socorro] ( NRAO ), National Radio Astronomy Observatory ( NRAO ), Netherlands Institute for Radio Astronomy, Chinese Academy of Sciences [Beijing] ( CAS ), NASA Goddard Space Flight Center ( GSFC ), Albert Einstein Institute, Max-Planck-Institut für Gravitationsphysik, Curtin University, Perth, Australia, Cornell Center for Astrophysics and Planetary Science ( CCAPS ), Cornell University, MPI for Gravitational Physics (Albert Einstein Institute), INAF-Osservatorio di Cagliari, PennState University [Pennsylvania] ( PSU ), Center for Radiophysics and Space Research [Ithaca] ( CRSR ), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), University of British Columbia ( UBC ), University of Edimburgh, Kavli Institute for Astronomy and Astrophysics, National Radio Astronomy Observatory [Green Bank] ( NRAO ), Commonwealth Scientific and Industrial Research Organisation [Canberra] ( CSIRO ), TAPIR (Theoretical Astrophysics), California Institute of Technology, Texas Tech University [Lubbock] ( TTU ), Osservatorio Astronomico di Cagliari, Ist Nazl Astrofis, Osservatorio Astronomico di Cagliari, APC - Gravitation ( APC-Gravitation ), AstroParticule et Cosmologie ( APC - UMR 7164 ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Max-Planck-Institut-Max-Planck-Institut, Centre for Astrophysics and Supercomputing [Swinburne] ( CAS ), Anton Pannekoek Institute for Astronomy, University of Amsterdam, Max Planck Institut für Gravitationsphysik, Albert Einstein Institut, Physics and Astronomy Department [Oberlin], Center for Gravitational Wave Astronomy, The University of Texas at Brownsville and Texas Southmost College, Birmingham City University ( BCU ), School of Physics, Huazhong University of Science and Technology, Huazhong University of Science and Technology, School of Physics ( University of Western Australia ), European Project : 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET ( 2014 ), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), University of Virginia, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI)

Subjects
data analysis, data analysis, pulsars: general [methods], FOS: Physical sciences, Methods: Data analysi, general [pulsars], 01 natural sciences, 7. Clean energy, Set (abstract data type), Pulsar timing array, Pulsar, 0103 physical sciences, data analysis [methods], Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, instrumentation, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Gravitational wave, Astrophysics::Instrumentation and Methods for Astrophysics, Pulsars: General, Astronomy, Astronomy and Astrophysics, methods: data analysis, Data set, European Pulsar Timing Array, Neutron star, gravitational waves, Space and Planetary Science, pulsars, Measurement uncertainty, Astrophysics - Instrumentation and Methods for Astrophysics, [ SDU.ASTR.SR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Algorithm, astro-ph.IM
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., 25 pages, 6 tables, 5 figures. Accepted for publication in MNRAS

Published
2016
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7. Studying the Solar system with the International Pulsar Timing Array

Author

R. S. Lynch, L. Toomey, Paul Demorest, J. K. Swiggum, X. Siemens, Gregory Desvignes, A. Possenti, T. J. W. Lazio, Gilles Theureau, D. R. Madison, Lucas Guillemot, Joseph Simon, Renée Spiewak, Kejia Lee, Alberto Sesana, Andrea N. Lommen, Gemma H. Janssen, Ramesh Karuppusamy, Xing-Jiang Zhu, Ismaël Cognard, Chiara M. F. Mingarelli, Benjamin Stappers, Stefan Oslowski, Sean T. McWilliams, Scott M. Ransom, S. A. Sanidas, David J. Nice, Kang Liu, G. Shaifullah, Marjorie Gonzalez, Y J Guo, Caterina Tiburzi, Robert D. Ferdman, James M. Cordes, P. Lazarus, N. D. R. Bhat, Jonathan R. Gair, Daniel R. Stinebring, George Hobbs, Sarah Burke-Spolaor, Nipuni Palliyaguru, Benetge Perera, Daniel J. Reardon, Richard N. Manchester, Shi Dai, Michael Kramer, Ryan Shannon, A. Brazier, R. van Haasteren, Joris P. W. Verbiest, Zaven Arzoumanian, M. Burgay, Timothy T. Pennucci, W. van Straten, Lina Levin, K. Plant, Ingrid H. Stairs, Peter A. Gentile, Duncan R. Lorimer, E. Graikou, Weiwei Zhu, N. Garver-Daniels, D. J. Champion, Matthew Bailes, S. J. Chamberlin, Delphine Perrodin, Sourav Chatterjee, Kevin Stovall, Michael Keith, Matthew Kerr, Timothy Dolch, J. B. Wang, R. N. Caballero, C. G. Bassa, Emmanuel Fonseca, Michael T. Lam, Stephen Taylor, Paul D. Lasky, J. W. McKee, Maura McLaughlin, Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Caballero, R, Guo, Y, Lee, K, Lazarus, P, Champion, D, Desvignes, G, Kramer, M, Plant, K, Arzoumanian, Z, Bailes, M, Bassa, C, Bhat, N, Brazier, A, Burgay, M, Burke-Spolaor, S, Chamberlin, S, Chatterjee, S, Cognard, I, Cordes, J, Dai, S, Demorest, P, Dolch, T, Ferdman, R, Fonseca, E, Gair, J, Garver-Daniels, N, Gentile, P, Gonzalez, M, Graikou, E, Guillemot, L, Hobbs, G, Janssen, G, Karuppusamy, R, Keith, M, Kerr, M, Lam, M, Lasky, P, Lazio, T, Levin, L, Liu, K, Lommen, A, Lorimer, D, Lynch, R, Madison, D, Manchester, R, Mckee, J, Mclaughlin, M, Mcwilliams, S, Mingarelli, C, Nice, D, Osłowski, S, Palliyaguru, N, Pennucci, T, Perera, B, Perrodin, D, Possenti, A, Ransom, S, Reardon, D, Sanidas, S, Sesana, A, Shaifullah, G, Shannon, R, Siemens, X, Simon, J, Spiewak, R, Stairs, I, Stappers, B, Stinebring, D, Stovall, K, Swiggum, J, Taylor, S, Theureau, G, Tiburzi, C, Toomey, L, van Haasteren, R, van Straten, W, Verbiest, J, Wang, J, Zhu, X, and Zhu, W

Subjects
Solar System, Dwarf planet, FOS: Physical sciences, Astrophysics, Ephemeris, 01 natural sciences, Jovian, Pulsar, pulsars: general, 0103 physical sciences, Sensitivity (control systems), ephemerides, 010303 astronomy & astrophysics, Physics, Earth and Planetary Astrophysics (astro-ph.EP), methods: statistical, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy and Astrophysics, Planetary system, Ephemeride, methods: data analysis, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Methods: data analysi, Reference frame, Astrophysics - Earth and Planetary Astrophysics
Abstract

Pulsar-timing analyses are sensitive to errors in the solar-system ephemerides (SSEs) that timing models utilise to estimate the location of the solar-system barycentre, the quasi-inertial reference frame to which all recorded pulse times-of-arrival are referred. Any error in the SSE will affect all pulsars, therefore pulsar timing arrays (PTAs) are a suitable tool to search for such errors and impose independent constraints on relevant physical parameters. We employ the first data release of the International Pulsar Timing Array to constrain the masses of the planet-moons systems and to search for possible unmodelled objects (UMOs) in the solar system. We employ ten SSEs from two independent research groups, derive and compare mass constraints of planetary systems, and derive the first PTA mass constraints on asteroid-belt objects. Constraints on planetary-system masses have been improved by factors of up to 20 from the previous relevant study using the same assumptions, with the mass of the Jovian system measured at 9.5479189(3)$\times10^{-4}$ $M_{\odot}$. The mass of the dwarf planet Ceres is measured at 4.7(4)$\times10^{-10}$ $M_{\odot}$. We also present the first sensitivity curves using real data that place generic limits on the masses of UMOs, which can also be used as upper limits on the mass of putative exotic objects. For example, upper limits on dark-matter clumps are comparable to published limits using independent methods. While the constraints on planetary masses derived with all employed SSEs are consistent, we note and discuss differences in the associated timing residuals and UMO sensitivity curves., Comment: Accepted for publication by the Monthly Notices of the Royal Astronomical Society

Published
2018
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8. THE NANOGRAV NINE-YEAR DATA SET:MASS and GEOMETRIC MEASUREMENTS of BINARY MILLISECOND PULSARS

Author

Kathryn Crowter, Scott M. Ransom, Joseph K. Swiggum, Paul Demorest, Michael T. Lam, Timothy Dolch, Ingrid H. Stairs, Zaven Arzoumanian, Kevin Stovall, Justin A. Ellis, Glenn Jones, Lina Levin, Maura McLaughlin, Emmanuel Fonseca, Weiwei Zhu, Robert D. Ferdman, David J. Nice, Timothy T. Pennucci, Megan L. Jones, and Marjorie Gonzalez

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Orbital elements, Physics, Mass distribution, close [binaries], 010308 nuclear & particles physics, Gravitational wave, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Shapiro delay, general [pulsars], Binary pulsar, Orbital inclination, neutron [stars], Pulsar, Space and Planetary Science, Millisecond pulsar, gravitation, evolution [stars], 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

We analyze 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. We make fourteen significant measurements of Shapiro delay, including new detections in four pulsar-binary systems (PSRs J0613$-$0200, J2017+0603, J2302+4442, and J2317+1439), and derive estimates of the binary-component masses and orbital inclination for these MSP-binary systems. We find a wide range of binary pulsar masses, with values as low as $m_{\rm p} = 1.18^{+0.10}_{-0.09}\text{M}_{\odot}$ for PSR J1918$-$0642 and as high as $m_{\rm p} = 1.928^{+0.017}_{-0.017}\text{M}_{\odot}$ for PSR J1614$-$2230 (both 68.3\% credibility). We make an improved measurement of the Shapiro timing delay in the PSR J1918$-$0642 and J2043+1711 systems, measuring the pulsar mass in the latter system to be $m_{\rm p} = 1.41^{+0.21}_{-0.18}\text{M}_{\odot}$ (68.3\% credibility) for the first time. We measure secular variations of one or more orbital elements in many systems, and use these measurements to further constrain our estimates of the pulsar and companion masses whenever possible. In particular, we used the observed Shapiro delay and periastron advance due to relativistic gravity in the PSR J1903+0327 system to derive a pulsar mass of $m_{\rm p} = 1.65^{+0.02}_{-0.02}\text{M}_{\odot}$ (68.3\% credibility). We discuss the implications that our mass measurements have on the overall neutron-star mass distribution, and on the "mass/orbital-period" correlation due to extended mass transfer., Comment: Fixed typos, added Table 5 and analysis of PSR J2145-0750. Accepted by ApJ on 24 September 2016

Published
2016
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9. The NANOGrav 11 yr Data Set: Arecibo Observatory Polarimetry and Pulse Microcomponents

Author

Paul Demorest, Zaven Arzoumanian, Renée Spiewak, Glenn Jones, Duncan R. Lorimer, Timothy T. Pennucci, Cherry Ng, Lina Levin, Marjorie Gonzalez, Ryan S. Lynch, Joseph K. Swiggum, Kathryn Crowter, Megan L. Jones, Paul S. Ray, Weiwei Zhu, Scott M. Ransom, Ingrid H. Stairs, Timothy Dolch, David J. Nice, Robert D. Ferdman, Megan E. DeCesar, Emmanuel Fonseca, Elizabeth C. Ferrara, Kevin Stovall, Peter A. Gentile, Michael T. Lam, Justin A. Ellis, and Maura McLaughlin

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Polarimetry, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Pulse (physics), Data set, Space and Planetary Science, 0103 physical sciences, Arecibo Observatory, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present the polarization pulse profiles for 28 pulsars observed with the Arecibo Observatory by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) timing project at 2.1 GHz, 1.4 GHz, and 430 MHz. These profiles represent some of the most sensitive polarimetric millisecond pulsar profiles to date, revealing the existence of microcomponents (that is, pulse components with peak intensities much lower than the total pulse peak intensity). Although microcomponents have been detected in some pulsars previously, we present microcomponents for PSRs B1937+21, J1713+0747, and J2234+0944 for the first time. These microcomponents can have an impact on pulsar timing, geometry, and flux density determination. We present rotation measures for all 28 pulsars, determined independently at different observation frequencies and epochs, and find the Galactic magnetic fields derived from these rotation measures to be consistent with current models. These polarization profiles were made using measurement equation template matching, which allows us to generate the polarimetric response of the Arecibo Observatory on an epoch-by-epoch basis. We use this method to describe its time variability, and find that the polarimetric responses of the Arecibo Observatory's 1.4 and 2.1 GHz receivers vary significantly with time., Comment: 41 pages, 20 figures

Published
2018
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10. The NANOGrav Nine-Year Data Set: Excess Noise in Millisecond Pulsar Arrival Times

Author

James M. Cordes, Robert D. Ferdman, Marjorie Gonzalez, David J. Nice, Paul Demorest, Timothy T. Pennucci, Ryan Shannon, Glenn Jones, Lina Levin, Kathryn Crowter, Megan L. Jones, X. Siemens, Joseph K. Swiggum, Scott M. Ransom, Shami Chatterjee, Kevin Stovall, Wei Zhu, Ingrid H. Stairs, Timothy Dolch, Dustin R. Madison, Emmanuel Fonseca, Michael T. Lam, Zaven Arzoumanian, Justin A. Ellis, and Maura McLaughlin

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Gravitational-wave astronomy, Pulsar timing array, Pulsar, Space and Planetary Science, Observatory, Millisecond pulsar, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Noise (radio)
Abstract

Gravitational wave astronomy using a pulsar timing array requires high-quality millisecond pulsars, correctable interstellar propagation delays, and high-precision measurements of pulse times of arrival. Here we identify noise in timing residuals that exceeds that predicted for arrival time estimation for millisecond pulsars observed by the North American Nanohertz Observatory for Gravitational Waves. We characterize the excess noise using variance and structure function analyses. We find that 26 out of 37 pulsars show inconsistencies with a white-noise-only model based on the short timescale analysis of each pulsar and we demonstrate that the excess noise has a red power spectrum for 15 pulsars. We also decompose the excess noise into chromatic (radio-frequency-dependent) and achromatic components. Associating the achromatic red-noise component with spin noise and including additional power-spectrum-based estimates from the literature, we estimate a scaling law in terms of spin parameters (frequency and frequency derivative) and data-span length and compare it to the scaling law of Shannon \& Cordes (2010). We briefly discuss our results in terms of detection of gravitational waves at nanohertz frequencies., 20 pages, 16 figures, to be published in ApJ

Published
2016
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11. Testing theories of gravitation using 21-year timing of Pulsar Binary J1713+0747

Author

Timothy Dolch, Kathryn Crowter, Megan L. Jones, Joseph K. Swiggum, Marjorie Gonzalez, Scott M. Ransom, Justin A. Ellis, Lina Levin, Emmanuel Fonseca, Maura McLaughlin, Paul Demorest, Zaven Arzoumanian, Glenn Jones, Weiwei Zhu, Michael T. Lam, Ingrid H. Stairs, Kevin Stovall, Timothy T. Pennucci, David J. Nice, and Robert D. Ferdman

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, White dwarf, Astronomy and Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, Orbital period, General Relativity and Quantum Cosmology, Gravitational constant, Gravitation, Neutron star, Pulsar, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Circular orbit, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract

We report 21-yr timing of one of the most precise pulsars: PSR J1713+0747. Its pulse times of arrival are well modeled by a comprehensive pulsar binary model including its three-dimensional orbit and a noise model that incorporates correlated noise such as jitter and red noise. Its timing residuals have weighted root mean square $\sim 92$ ns. The new dataset allows us to update and improve previous measurements of the system properties, including the masses of the neutron star ($1.31\pm0.11$ $M_{\odot}$) and the companion white dwarf ($0.286\pm0.012$ $M_{\odot}$) and the parallax distance $1.15\pm0.03$ kpc. We measured the intrinsic change in orbital period, $\dot{P}^{\rm Int}_{\rm b}$, is $-0.20\pm0.17$ ps s$^{-1}$, which is not distinguishable from zero. This result, combined with the measured $\dot{P}^{\rm Int}_{\rm b}$ of other pulsars, can place a generic limit on potential changes in the gravitational constant $G$. We found that $\dot{G}/G$ is consistent with zero [$(-0.6\pm1.1)\times10^{-12}$ yr$^{-1}$, 95\% confidence] and changes at least a factor of $31$ (99.7\% confidence) more slowly than the average expansion rate of the Universe. This is the best $\dot{G}/G$ limit from pulsar binary systems. The $\dot{P}^{\rm Int}_{\rm b}$ of pulsar binaries can also place limits on the putative coupling constant for dipole gravitational radiation $\kappa_D=(-0.9\pm3.3)\times10^{-4}$ (95\% confidence). Finally, the nearly circular orbit of this pulsar binary allows us to constrain statistically the strong-field post-Newtonian parameters $\Delta$, which describes the violation of strong equivalence principle, and $\hat{\alpha}_3$, which describes a breaking of both Lorentz invariance in gravitation and conservation of momentum. We found, at 95\% confidence, $\Delta, Comment: 14 pages, 6 figures. Published on ApJ, 809, 41 (2015)

Published
2015

12. Spatially Resolved Spectroscopy of theChandraField Containing the Supernova Remnant G292.2−0.5

Author

Samar Safi-Harb and Marjorie Gonzalez

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Pulsar wind nebula, Luminosity, Neutron star, Pulsar, Space and Planetary Science, Black-body radiation, Advanced CCD Imaging Spectrometer, Supernova remnant, Spectroscopy, Astrophysics::Galaxy Astrophysics
Abstract

We present observations with the Chandra Advanced CCD Imaging Spectrometer (ACIS-S) of the western interior of the supernova remnant (SNR) G292.2-0.5 associated with the high magnetic field pulsar (PSR) J1119-6127. Chandra's excellent resolution revealed 18 point sources on the S3 chip and allowed the study of the diffuse emission from G292.2-0.5 independently from these point sources. The diffuse emission from G292.2-0.5 can be adequately fitted with nonequilibrium ionization models; however, these fits result in an unrealistically high temperature (kT > 3 keV), indicating the presence of a hard nonthermal component. By performing a spatially resolved spectroscopic study of the remnant, we identify the nonthermal emission as originating from the region closer to the pulsar. Its spectrum is well described with a power law with a photon index of Γ ~ 1-2. As a result of the flat spectrum and location close to the pulsar, we propose that this nonthermal emission arises from the injection of high-energy particles originating from PSR J1119-6127 and its pulsar wind nebula (PWN) into the SNR shell. As for the 18 point sources revealed by Chandra, only 3 sources have previously known counterparts at other wavelengths. Two of these sources exhibit enough counts to extract a spectrum, one being a new source CXOU J111911.8-613026 and the other being the X-ray counterpart of PSR J1119-6127 studied by us in a previous work. The spectrum of the new source CXOU J111911.8-613026 is soft (power-law photon index Γ ~ 3.6-4.6 or blackbody temperature kT ~ 0.2-0.36 keV) with a luminosity comparable to that of faint radio-quiet neutron stars. The nature of CXOU J111911.8-613026, however, cannot be determined with the present data and has to await further observations.

Published
2005
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13. The NANOGrav Nine-Year Data Set: Noise Budget for Pulsar Arrival Times on Intraday Timescales

Author

Paul Demorest, Robert D. Ferdman, Lina Levin, Timothy Dolch, Justin A. Ellis, Zaven Arzoumanian, Glenn Jones, Marjorie Gonzalez, Scott M. Ransom, Maura McLaughlin, Joseph K. Swiggum, Ingrid H. Stairs, Shami Chatterjee, Emmanuel Fonseca, Kevin Stovall, Michael T. Lam, Kathryn Crowter, Megan L. Jones, J. M. Cordes, X. Siemens, Timothy T. Pennucci, Weiwei Zhu, Dustin R. Madison, and David J. Nice

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Line-of-sight, 010308 nuclear & particles physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, 7. Clean energy, Pulse (physics), Amplitude, Pulsar, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Impulse response, Noise (radio), Jitter
Abstract

The use of pulsars as astrophysical clocks for gravitational wave experiments demands the highest possible timing precision. Pulse times of arrival (TOAs) are limited by stochastic processes that occur in the pulsar itself, along the line of sight through the interstellar medium, and in the measurement process. On timescales of seconds to hours, the TOA variance exceeds that from template-fitting errors due to additive noise. We assess contributions to the total variance from two additional effects: amplitude and phase jitter intrinsic to single pulses and changes in the interstellar impulse response from scattering. The three effects have different dependencies on time, frequency, and pulse signal-to-noise ratio. We use data on 37 pulsars from the North American Nanohertz Observatory for Gravitational Waves to assess the individual contributions to the overall intraday noise budget for each pulsar. We detect jitter in 22 pulsars and estimate the average value of RMS jitter in our pulsars to be $\sim 1\%$ of pulse phase. We examine how jitter evolves as a function of frequency and find evidence for evolution. Finally, we compare our measurements with previous noise parameter estimates and discuss methods to improve gravitational wave detection pipelines., Comment: 22 pages, 11 figures, published in ApJ

Published
2015
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14. The NANOGrav Nine-year Data Set: Astrometric Measurements of 37 Millisecond Pulsars

Author

Paul Demorest, Lina Levin, Weiwei Zhu, Michael T. Lam, Scott M. Ransom, Marjorie Gonzalez, Justin A. Ellis, Maura McLaughlin, Zaven Arzoumanian, Timothy Dolch, Glenn Jones, Kathryn Crowter, Emmanuel Fonseca, Joseph K. Swiggum, Kevin Stovall, Robert D. Ferdman, Ingrid H. Stairs, Timothy T. Pennucci, David J. Nice, Megan L. Jones, and A. M. Matthews

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics, 01 natural sciences, Pulsar, Millisecond pulsar, 0103 physical sciences, Arecibo Observatory, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), education.field_of_study, 010308 nuclear & particles physics, Gravitational wave, Green Bank Telescope, Astrophysics::Instrumentation and Methods for Astrophysics, Velocity dispersion, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Neutron star, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena
Abstract

Using the nine-year radio-pulsar timing data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), collected at Arecibo Observatory and the Green Bank Telescope, we have measured the positions, proper motions, and parallaxes for 37 millisecond pulsars. We report twelve significant parallax measurements and distance measurements, and eighteen lower limits on distance. We compare these measurements to distances predicted by the NE2001 interstellar electron density model and find them to be in general agreement. We use measured orbital-decay rates and spin-down rates to confirm two of the parallax distances and to place distance upper limits on other sources; these distance limits agree with the parallax distances with one exception, PSR J1024-0719, which we discuss at length. Using the proper motions of the 37 NANOGrav pulsars in combination with other published measurements, we calculate the velocity dispersion of the millisecond pulsar population in Galactocentric coordinates. We find the radial, azimuthal, and perpendicular dispersions to be 46, 40, and 24 km s-1, respectively, in a model that allows for high-velocity outliers; or 81, 58, and 62 km s-1 for the full population. These velocity dispersions are far smaller than those of the canonical pulsar population, and are similar to older Galactic disk populations. This suggests that millisecond pulsar velocities are largely attributable to their being an old population rather than being artifacts of their birth and evolution as neutron star binary systems. The components of these velocity dispersions follow similar proportions to other Galactic populations, suggesting that our results are not biased by selection effects., Comment: Accepted by ApJ

Published
2015
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15. Texture and shape analysis on high and low spatial resolution emission images

Author

Vesna Sossi, Marjorie Gonzalez, Arman Rahmim, Ivan S. Klyuzhin, and Stephan Blinder

Subjects
Physics, medicine.diagnostic_test, business.industry, Single-photon emission computed tomography, Gaussian filter, Dihydrotetrabenazine, symbols.namesake, chemistry.chemical_compound, chemistry, Region of interest, Positron emission tomography, Image noise, symbols, medicine, Computer vision, Artificial intelligence, business, Image resolution, Shape analysis (digital geometry)
Abstract

Texture and shape analysis applied to positron emission tomography (PET) or single photon emission computed tomography (SPECT) imaging is a technique based on the characterization of the spatial distribution of a radio tracer using texture and shape descriptors. It has been shown in recent studies to provide functional disease related information. Applied to high resolution PET images of patients suffering from Parkinson's disease (PD), a good correlation has been found between 3D moment invariants (3DMI) which are shape metrics and Parkinson's disease severity. Given the wide availability of SPECT cameras in clinical environments, could texture and shape analysis provide comparable results on lower resolution images to those obtained with state-of-the-art PET cameras? The aim of the present study is to investigate the applicability and robustness of the texture and shape analysis in the specific context of images displaying localized spatial distribution of the tracer with disease induced spatial abnormalities. Applicability and robustness of the method was tested against: i) the choice of the texture and shape descriptors, ii) the image spatial resolution, iii) the image noise level and iv) the definition of the region of interest (ROI). Methods: a magnetic resonance imaging (MRI) scan to provide anatomical information for ROIs placement and a high resolution PET scan providing a dynamic sequence of [11C]dihydrotetrabenazine (DTBZ) images were acquired for 13 PD patients and 6 healthy controls. To simulate the lower spatial resolutions, the reconstructed PET images were smoothed with a 3D Gaussian filter with a full width at half maximum (FWHM) ranging from 2 mm to 20 mm. As an evaluation criterion, Spearman's correlation was calculated between texture and shape metrics and disease severity assessed either by the unified Parkinson's disease rating scale (UPDRS) scores or by the disease duration. Results and conclusion: this study has shown that texture and shape analysis can provide relevant disease related information when applied to images of tracers displaying a localized spatial distribution with disease dependent heterogeneity and/or shape characteristics. In the specific case of Parkinson's disease imaged with the PET tracer [11C]DTBZ, we have shown that the MEAN intensity metric and the 3D moment invariant metrics are strongly correlated with disease severity and that the strength of the correlation persisted on images ranging from the highest spatial resolutions achievable by state-of-the-art PET cameras to the lowest resolutions achievable by any modern clinical SPECT camera.

Published
2014
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16. Limits on the Stochastic Gravitational Wave Background from the North American Nanohertz Observatory for Gravitational Waves

Author

Zaven Arzoumanian, Andrea N. Lommen, Joseph K. Swiggum, Paul Demorest, Scott M. Ransom, S. Giampanis, S. J. Chamberlin, David J. Nice, V. M. Kaspi, Sarah Burke-Spolaor, A. Brazier, Fredrick A. Jenet, Joseph Lazio, J. M. Cordes, Nipuni Palliyaguru, Ryan Shannon, Paulo C. C. Freire, Ingrid H. Stairs, X. Siemens, Marjorie Gonzalez, Robert D. Ferdman, Justin A. Ellis, Lee Samuel Finn, Maura McLaughlin, Daniel R. Stinebring, Delphine Perrodin, and Weiwei Zhu

Subjects
Physics, Supermassive black hole, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010308 nuclear & particles physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Pulse (physics), Radio telescope, Gravitational wave background, Pulsar, Space and Planetary Science, Observatory, 0103 physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Dispersion (water waves), 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green Bank and Arecibo radio telescopes. We analyze these data using standard pulsar timing models, with the addition of time-variable dispersion measure and frequency-variable pulse shape terms. Sub-microsecond timing residuals are obtained in nearly all cases, and the best root-mean-square timing residuals in this set are ~30-50 ns. We present methods for analyzing post-fit timing residuals for the presence of a gravitational wave signal with a specified spectral shape. These optimally take into account the timing fluctuation power removed by the model fit, and can be applied to either data from a single pulsar, or to a set of pulsars to detect a correlated signal. We apply these methods to our dataset to set an upper limit on the strength of the nHz-frequency stochastic supermassive black hole gravitational wave background of h_c (1 yr^-1) < 7x10^-15 (95%). This result is dominated by the timing of the two best pulsars in the set, PSRs J1713+0747 and J1909-3744., To be submitted to ApJ

Published
2012
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17. The International Pulsar Timing Array project: using pulsars as a gravitational wave detector

Author

Matthew Bailes, V. M. Kaspi, David Champion, Kejia Lee, Ryan Shannon, X. P. You, M. Burgay, K. Lazaridis, Michael Kramer, M. B. Purver, D. R. B. Yardley, Duncan R. Lorimer, Paul Demorest, Andrea N. Lommen, Alberto Sesana, Joseph Lazio, William A. Coles, Fredrick A. Jenet, Christine Jordan, Jason W. T. Hessels, M. Pilia, Gregory Desvignes, Scott M. Ransom, S. Sanidas, Gilles Theureau, Ismaël Cognard, Andrea Possenti, David J. Nice, Daniel R. Stinebring, Paulo C. C. Freire, Ben Stappers, Ingrid H. Stairs, Robert D. Ferdman, Lee Samuel Finn, Anne M. Archibald, R. van Haasteren, George Hobbs, Stefan Oslowski, John Reynolds, Xavier Siemens, J. M. Cordes, Richard N. Manchester, Gemma H. Janssen, Zaven Arzoumanian, Yuri Levin, John Sarkissian, V. I. Kondratiev, Andrew Lyne, W. van Straten, Ryan S. Lynch, Sarah Burke-Spolaor, A. Jessner, Maura McLaughlin, Joris P. W. Verbiest, N. D. R. Bhat, Marjorie Gonzalez, Aidan Hotan, Donald C. Backer, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics, Gravitational-wave observatory, Physics and Astronomy (miscellaneous), 010308 nuclear & particles physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Binary number, Astrophysics, Galaxy merger, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, General Relativity and Quantum Cosmology, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, International Pulsar Timing Array
Abstract

The International Pulsar Timing Array project combines observations of pulsars from both Northern and Southern hemisphere observatories with the main aim of detecting ultra-low frequency (~10^-9 to 10^-8 Hz) gravitational waves. Here we introduce the project, review the methods used to search for gravitational waves emitted from coalescing supermassive binary black-hole systems in the centres of merging galaxies and discuss the status of the project., accepted by Classical and Quantum Gravity. Review talk for the Amaldi8 conference series

Published
2010
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18. New Constraints on the Energetics, Progenitor Mass, and Age of the Supernova Remnant G292.0+1.8 Containing PSR J1124-5916

Author

Samar Safi-Harb and Marjorie Gonzalez

Subjects
Physics, Spectral index, Solar mass, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Radius, 01 natural sciences, Pulsar wind nebula, Supernova, Pulsar, 13. Climate action, Space and Planetary Science, Nucleosynthesis, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present spatially resolved spectroscopy of the supernova remnant (SNR) G292.0+1.8 with the Chandra X-ray observatory. This SNR contains the 135 ms pulsar, J1124-5916. We apply non-equilibrium ionization (NEI) models to the data. By comparing the derived abundances with those predicted from nucleosynthesis models, we estimate a progenitor mass of 30-40 solar masses. We also derive the intrinsic parameters of the supernova explosion such as its energy, the age of the SNR, the blast wave velocity, and the swept-up mass. In the Sedov interpretation, our estimated SNR age of 2,600 years is close to the pulsar's characteristic age of 2,900 years. This confirms the pulsar/SNR association and relaxes the need for the pulsar to have a non-canonical value for the braking index, a large period at birth or a large transverse velocity. We discuss the properties of the pulsar wind nebula (PWN) in the light of the Kennel and Coroniti model and estimate the pulsar wind magnetization parameter. We also report the first evidence for steepening of the power law spectral index with increasing radius from the pulsar., Comment: 5 pages, 3 figures. To appear in ApJL, Feb 1 2003 (submitted Oct 9 2002, accepted Dec 19 2002)

Published
2003
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19. DEEP X-RAY OBSERVATIONS OF THE YOUNG HIGH-MAGNETIC-FIELD RADIO PULSAR J1119–6127 AND SUPERNOVA REMNANT G292.2–0.5

Author

Victoria M. Kaspi, Chi-Yung Ng, Ryan Shannon, Wynn C. G. Ho, Slavko Bogdanov, Marjorie Gonzalez, and Patrick Weltevrede

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Hot spot (veterinary medicine), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Magnetar, 01 natural sciences, Magnetic field, law.invention, Telescope, Pulsar, Space and Planetary Science, Observatory, law, Ionization, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010306 general physics, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

High-magnetic-field radio pulsars are important transition objects for understanding the connection between magnetars and conventional radio pulsars. We present a detailed study of the young radio pulsar J1119-6127, which has a characteristic age of 1900yr and a spin-down-inferred magnetic field of 4.1e13G, and its associated supernova remnant G292.2-0.5, using deep XMM-Newton and Chandra X-ray Observatory exposures of over 120ks from each telescope. The pulsar emission shows strong modulation below 2.5keV, with a single-peaked profile and a large pulsed fraction of 0.48+/-0.12. Employing a magnetic, partially ionized hydrogen atmosphere model, we find that the observed pulse profile can be produced by a single hot spot of temperature 0.13keV covering about one third of the stellar surface, and we place an upper limit of 0.08keV for an antipodal hot spot with the same area. The nonuniform surface temperature distribution could be the result of anisotropic heat conduction under a strong magnetic field, and a single-peaked profile seems common among high-B radio pulsars. For the associated remnant G292.2-0.5, its large diameter could be attributed to fast expansion in a low-density wind cavity, likely formed by a Wolf-Rayet progenitor, similar to two other high-B radio pulsars., Comment: 11 pages, 4 figures, accepted for publication in ApJ

Published
2012
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20. CHANDRAANDXMM-NEWTONSTUDIES OF THE SUPERNOVA REMNANT G292.2-0.5 ASSOCIATED WITH THE PULSAR J1119-6127

Author

Harsha S. Kumar, Marjorie Gonzalez, and Samar Safi-Harb

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Solar mass, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Spectral line, Supernova, Pulsar, 13. Climate action, Space and Planetary Science, Nucleosynthesis, Ionization, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010306 general physics, Ejecta, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present the first detailed imaging and spatially resolved spectroscopic study of the Galactic supernova remnant G292.2-0.5, associated with the high-magnetic field radio pulsar J1119-6127, using Chandra and XMM-Newton. The high-resolution X-ray images reveal a partially limb-brightened morphology in the west, with diffuse emission concentrated towards the interior of the remnant unlike the complete shell-like morphology observed at radio wavelengths. The spectra of most of the diffuse emission regions within the remnant are best described by a thermal+non-thermal model. The thermal component is described by a plane-parallel, non-equilibrium ionization plasma model with a temperature ranging from 1.3 keV in the western side of the remnant to 2.3 keV in the east, a column density increasing from 1.0e22 cm^-2 in the west to 1.8e22 cm^-2 in the east, and a low ionization timescale ranging from 5.7e9 cm^-3 s in the SNR interior to 3.6e10 cm^-3 s in the western side - suggestive of expansion of a young remnant in a low-density medium. The spatial and spectral differences across the SNR are consistent with the presence of a dark cloud in the eastern part of the SNR, absorbing the soft X-ray emission. The spectra from some of the regions also show slightly enhanced metal abundances from Ne, Mg and Si, hinting at the first evidence for ejecta heated by the reverse shock. Comparing our inferred metal abundances to core-collapse nucleosynthesis models yields, we estimate a high progenitor mass of ~30 solar mass suggesting a type Ib/c supernova. We confirm the presence of non-thermal hard X-ray emission from regions close to the pulsar. We estimate an SNR age range between 4.2 kyr (free expansion phase) and 7.1 kyr (Sedov phase), a factor of a few higher than the measured pulsar's age upper limit of 1.9 kyr., 17 pages, 7 figures, 4 tables; Abstract abridged. Accepted for publication in the Astrophysical Journal

Published
2012
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21. The NANOGrav Nine-year Data Set: Monitoring Interstellar Scattering Delays

Author

Timothy Dolch, Robert D. Ferdman, Justin A. Ellis, Glenn Jones, Nipuni Palliyaguru, Maura McLaughlin, Daniel R. Stinebring, T. Joseph W. Lazio, Ingrid H. Stairs, Scott M. Ransom, Marjorie Gonzalez, Kathryn Crowter, Lina Levin, Emmanuel Fonseca, Zaven Arzoumanian, Michael T. Lam, Joseph K. Swiggum, James M. Cordes, David J. Nice, Timothy T. Pennucci, Megan L. Jones, Weiwei Zhu, Shami Chatterjee, Kevin Stovall, and Paul Demorest

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Scintillation, Proper motion, 010308 nuclear & particles physics, Gravitational wave, Scattering, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Interstellar medium, Pulsar, Space and Planetary Science, Millisecond pulsar, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Noise (radio)
Abstract

We report on an effort to extract and monitor interstellar scintillation parameters in regular timing observations collected for the NANOGrav pulsar timing array. Scattering delays are measured by creating dynamic spectra for each pulsar and observing epoch of wide-band observations centered near 1500 MHz and carried out at the Green Bank Telescope and the Arecibo Observatory. The ~800-MHz wide frequency bands imply dramatic changes in scintillation bandwidth across the bandpass, and a stretching routine has been included to account for this scaling. For most of the 10 pulsars for which the scaling has been measured, the bandwidths scale with frequency less steeply than expected for a Kolmogorov medium. We find estimated scattering delay values that vary with time by up to an order of magnitude. The mean measured scattering delays are similar to previously published values and slightly higher than predicted by interstellar medium models. We investigate the possibility of increasing the timing precision by mitigating timing errors introduced by the scattering delays. For most of the pulsars, the uncertainty in the time of arrival of a single timing point is much larger than the maximum variation of the scattering delay, suggesting that diffractive scintillation remains only a negligible part of their noise budget., 14 pages, 5 figures, 3 tables. Accepted for publication in ApJ

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