M. J. Keith
A5073994859- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Advanced Frequency and Time Standards
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- GNSS positioning and interference
- Superconducting Materials and Applications
- Stellar, planetary, and galactic studies
- High-pressure geophysics and materials
- Astronomy and Astrophysical Research
- Geophysics and Sensor Technology
- Particle Accelerators and Free-Electron Lasers
- Inertial Sensor and Navigation
- Seismic Waves and Analysis
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Statistical and numerical algorithms
- Atomic and Subatomic Physics Research
- Policing Practices and Perceptions
- Distributed and Parallel Computing Systems
- Antiplatelet Therapy and Cardiovascular Diseases
University of Manchester
2016-2025
SKA Observatory
2007-2023
University of Bristol
2022-2023
University of Oxford
2022
Max Planck Society
2015
Max Planck Institute for Radio Astronomy
2011-2015
Australia Telescope National Facility
2008-2014
Commonwealth Scientific and Industrial Research Organisation
2008-2013
Astronomy and Space
2010-2013
Osservatorio Astronomico di Cagliari
2011
Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey pulsars and fast transients we have uncovered four millisecond-duration radio all more than 40{\deg} from the Galactic plane. The bursts' properties indicate they celestial rather terrestrial origin. Host galaxy intergalactic medium models suggest cosmological redshifts 0.5 to 1, distances up 3 gigaparsecs. No temporally coincident x- or gamma-ray...
We present the results of search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using second data release European Pulsar Timing Array (EPTA) 25 millisecond pulsars and a combination with first Indian (InPTA). analysed (i) full 24.7-year EPTA set, (ii) its 10.3-year subset based on modern observing systems, (iii) set InPTA ten commonly timed pulsars, (iv) data. These combinations allowed us to probe contributions instrumental noise interstellar...
A "pulsar timing array" (PTA), in which observations of a large sample pulsars spread across the celestial sphere are combined, allows investigation "global" phenomena such as background gravitational waves or instabilities atomic timescales that produce correlated residuals array. The Parkes Pulsar Timing Array (PPTA) is an implementation PTA concept based on with 64-m radio telescope. 20 millisecond being observed at three radio-frequency bands, 50cm (~700 MHz), 20cm (~1400 MHz) and 10cm...
Placing bounds on gravitational wave detection Gravitational waves are expected to be generated by the interaction of massive bodies in black-hole binary systems. As distort spacetime, it should possible verify their existence as they interfere with pulses emitted millisecond pulsars. However, after monitoring 24 pulsars Parkes radio telescope for 12 years, Shannon et al. found no detectable variation pulsar records. This nondetection result indicates that a new strategy is needed. Science ,...
The highly stable spin of neutron stars can be exploited for a variety (astro)physical investigations. In particular, arrays pulsars with rotational periods the order milliseconds used to detect correlated signals such as those caused by gravitational waves. Three ‘pulsar timing arrays’ (PTAs) have been set up around world over past decades and collectively form ‘International’ PTA (IPTA). this paper, we describe first joint analysis data from three regional PTAs, i.e. IPTA set. We available...
We present timing models for 20 millisecond pulsars in the Parkes Pulsar Timing Array. The precision of parameter measurements these has been improved over earlier results by using longer data sets and modelling non-stationary noise. describe a new noise procedure demonstrate its effectiveness simulated data. Our methodology includes addition annual dispersion measure (DM) variations to some pulsars. first significant parallax PSRs J1024−0719, J1045−4509, J1600−3053, J1603−7202, J1730−2304,...
We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by theory of General Relativity using six radio millisecond pulsars Data Release 2 (DR2) European Pulsar Timing Array (EPTA) covering timespan up to 24 years. A GWB manifests itself long-term low-frequency signal common all pulsars, red (CRS), with characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which...
Abstract The detection of five new fast radio bursts (FRBs) found in the 1.4-GHz High Time Resolution Universe high-latitude survey at Parkes, is presented. rate implied 7$^{+5}_{-3}\times 10^3$ (95 per cent) FRBs sky−1 d−1 above a fluence 0.13 Jy ms for an FRB 0.128 duration to 1.5 16 duration. One these has two-component profile, which each component similar known population single and two components are separated by 2.4 ± 0.4 ms. All appear be unresolved following deconvolution with...
We searched for an isotropic stochastic gravitational wave background in the second data release of International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns North America, Europe, and Australia. In our reference search power law strain spectrum form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence spectrally-similar low-frequency process amplitude $A 3.8^{+6.3}_{-2.5}\times10^{-15}$ spectral index $\alpha -0.5 \pm 0.5$,...
In this paper, we describe the International Pulsar Timing Array second data release, which includes recent pulsar timing obtained by three regional consortia: European Array, North American Nanohertz Observatory for Gravitational Waves, and Parkes Array. We analyse where possible combine high-precision 65 millisecond pulsars are regularly observed these groups. A basic noise analysis, including processes both correlated uncorrelated in time, provides models ephemerides pulsars. find that...
Pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1 - 100 nanohertz), which is intimately connected to number markers that can uniquely trace formation and evolution Universe. We present dataset results analysis from second data release European Timing Array (EPTA). The contains high-precision pulsar 25 millisecond pulsars collected with five largest radio telescopes in Europe, as well Large for Pulsars. forms foundation search waves by EPTA, presented...
Abstract We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ array that currently operates 580–1 670 MHz can produce tied-array beams suitable observations. This paper presents MeerTime Large Survey Project commissioning with PTUSE. Highlights include...
The European Pulsar Timing Array (EPTA) and Indian (InPTA) collaborations have measured a low-frequency common signal in the combination of their second first data releases, respectively, with correlation properties gravitational wave background (GWB). Such may its origin number physical processes including cosmic population inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, strings, tensor mode generation by non-linear evolution scalar perturbations early...
The European Pulsar Timing Array (EPTA) and Indian (InPTA) collaborations have measured a low-frequency common signal in the combination of their second first data releases respectively, with correlation properties gravitational wave background (GWB). Such may its origin number physical processes including cosmic population inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, strings tensor mode generation by non-linear evolution scalar perturbations early...
Abstract We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on Fermi Gamma-ray Space Telescope. Another 33 millisecond (MSPs) discovered deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with also harbor gamma-ray MSPs. This catalog thus reports roughly 340 and candidates, 10% all known pulsars, compared to ≤11 before Fermi. Half...
Aims. The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of ensemble waves emitted predominantly by a large population coalescing supermassive black hole binaries in the centres merging galaxies. Pulsar timing arrays (PTAs), which are ensembles extremely stable pulsars at approximately kiloparsec distances precisely monitored for decades, most precise experiments capable detecting this background. However, subtle imprints that GWB induces on pulsar data...
ABSTRACT The International Pulsar Timing Array 2nd data release is the combination of sets from worldwide collaborations. In this study, we search for continuous waves: gravitational wave signals produced by individual supermassive black hole binaries in local universe. We consider on circular orbits and neglect evolution orbital frequency over observational span. find no evidence such set sky averaged 95 per cent upper limits their amplitude h95. most sensitive 10 nHz with h95 = 9.1 ×...
Pulsar Timing Array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing an ensemble galactic millisecond radio pulsars. With second data release European Array, we focus on most robust scenario, in which interacts only gravitationally with ordinary baryonic matter. Our results show that masses 10^{-24.0} eV≲m≲10^{-23.3} eV cannot constitute 100% measured local density, but can have at density ρ≲0.3 GeV/cm^{3}.
We present the results of a search for continuous gravitational wave signals (CGWs) in second data release (DR2) European Pulsar Timing Array (EPTA) Collaboration. The most significant candidate event from this has frequency 4–5 nHz. Such signal could be generated by supermassive black hole binary (SMBHB) local Universe. follow-up analysis using both Bayesian and frequentist methods. gives Bayes factor 4 favour presence CGW over common uncorrelated noise process. In contrast, estimates...
We have embarked on a survey for pulsars and fast transients using the 13-beam multibeam receiver Parkes Radio Telescope. Installation of digital backend allows us to record 400 MHz bandwidth each beam, split into 1024 channels sampled every 64 μs. Limits package restrict 340 observing band centred at 1352 MHz. The factor 8 improvement in frequency resolution over previous surveys probe deeper Galactic plane short-duration signals such as pulses from millisecond pulsars. plan entire southern...
We present precise phase-connected pulse timing solutions for 16 gamma-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on Fermi Gamma-ray Space plus one very faint radio pulsar (PSR J1124-5916) that is more effectively timed with LAT. describe analysis techniques including a maximum likelihood method determining times of arrival from unbinned photon data. A major result this work improved position determinations, which are crucial multi-wavelength follow up. For...
Signals from radio pulsars show a wavelength-dependent delay due to dispersion in the interstellar plasma. At typical observing wavelength, this can vary by tens of microseconds on five-year time scales, far excess signals interest pulsar timing arrays, such as that induced gravitational-wave background. Measurement these variations is not only crucial for detection signals, but also provides an unparallelled measurement turbulent plasma at au scales. In paper we demonstrate without...
Using observations of pulsars from the Parkes Pulsar Timing Array (PPTA) project we develop first pulsar-based timescale that has a precision comparable to uncertainties in international atomic timescales.Our ensemble provides an Ensemble Scale (EPS) analogous free Échelle Atomique Libre (EAL).The EPS can be used detect fluctuations timescales and therefore lead new realisation Terrestrial Time, TT(PPTA11).We successfully follow features known affect frequency International Atomic Timescale...
Timing observations from the Parkes 64-m radio telescope for 165 pulsars between 1990 and 2011 have been searched period glitches. A total of 107 glitches were identified in 36 pulsars, where 61 previously reported 46 are new discoveries. Glitch parameters measured by fitting timing residual data. Observed relative glitch sizes \Delta\nu_g/\nu range 10^-10 10^-5, \nu = 1/P is pulse frequency. We confirm that distribution bimodal with peaks at approximately 10^-9 10^-6. Glitches mostly...
We report on the discovery of \geq 100 MeV {\gamma} rays from binary system PSR B1259-63/LS 2883 using Large Area Telescope (LAT) board Fermi. The comprises a radio pulsar in orbit around Be star. LAT observations near apastron to ~ 60 days after time periastron, tp, 2010 December 15. No {\gamma}-ray emission was detected this source when it far periastron. Faint appeared as approached At tp + 30d, flux increased over period few peak 20-30 times that seen during pre-periastron period, but...