D. R. Lorimer
A5048953157- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- High-pressure geophysics and materials
- Stellar, planetary, and galactic studies
- Geophysics and Sensor Technology
- GNSS positioning and interference
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Advanced Frequency and Time Standards
- Superconducting Materials and Applications
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Magnetic confinement fusion research
- Astro and Planetary Science
- Superconducting and THz Device Technology
- Scientific Research and Discoveries
- Atomic and Subatomic Physics Research
- Statistical and numerical algorithms
- Cold Atom Physics and Bose-Einstein Condensates
West Virginia University
2015-2024
National Postdoctoral Association
2024
Albert Einstein College of Medicine
2024
Campbell Collaboration
2023
West Virginia University Hospitals
2015-2018
National Radio Astronomy Observatory
2008-2017
Max Planck Institute for Radio Astronomy
1996-2015
Max Planck Society
1996-2015
Franklin & Marshall College
2015
University of Oxford
2013-2014
The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They also known to have much higher mean orbital velocities and accelerations than those of other binary therefore a good candidate for testing Einstein's theory general relativity alternative theories gravity the strong-field regime. We report on precision timing observations taken over 2.5 years since its discovery present four independent tests relativity. These use...
Abstract We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by North American Nanohertz Observatory Gravitational Waves. The correlations follow Hellings–Downs pattern expected gravitational-wave background. presence such background with power-law spectrum favored over model only independent noises Bayes factor in excess 10 14 , and this same an uncorrelated common factors 200–1000, depending on...
The clocklike properties of pulsars moving in the gravitational fields their unseen neutron-star companions have allowed unique tests general relativity and provided evidence for radiation. We report here detection 2.8-second pulsar J0737-3039B as companion to 23-millisecond J0737-3039A a highly relativistic double neutron star system, allowing unprecedented fundamental physics. observed short eclipse by orbital modulation flux density pulse shape J0737-3039B, probably because influence...
We present and analyse a catalogue of 233 pulsars with proper motion measurements. The sample contains wide variety including recycled objects those associated globular clusters or supernova remnants. After taking the most precise motions for which multiple measurements are available, majority (58%) derived from pulsar timing methods, 41% using interferometers remaining 1% optical telescopes. Many 1-D 2-D speeds (referring to measured in one coordinate only magnitudes transverse velocities...
The International Pulsar Timing Array project combines observations of pulsars from both northern and southern hemisphere observatories with the main aim detecting ultra-low frequency (∼ 10−9–10−8 Hz) gravitational waves. Here we introduce project, review methods used to search for waves emitted coalescing supermassive binary black-hole systems in centres merging galaxies discuss status project.
Abstract We present high-precision timing data over time spans of up to 11 years for 45 millisecond pulsars observed as part the North American Nanohertz Observatory Gravitational Waves (NANOGrav) project, aimed at detecting and characterizing low-frequency gravitational waves. The were with Arecibo and/or Green Bank Telescope frequencies ranging from 327 MHz 2.3 GHz. Most approximately monthly cadence, six high-timing-precision weekly. All widely separated each observing epoch in order fit...
Radio pulsars with millisecond spin periods are thought to have been spun up by transfer of matter and angular momentum from a low-mass companion star during an X-ray-emitting phase. The the neutron stars in several such X-ray binary (LMXB) systems shown be regime, but no radio pulsations detected. Here we report on detection follow-up observations nearby pulsar (MSP) circular orbit optically identified star. Optical indicate that accretion disk was present this system within last decade....
Abstract The 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) shows positive evidence presence of a low-frequency gravitational-wave (GW) background. In this paper, we investigate potential cosmological interpretations signal, specifically cosmic inflation, scalar-induced GWs, first-order phase transitions, strings, and domain walls. We find that, with exception stable strings field theory origin, all these models can...
[ABRIDGED] We present the discovery and follow-up observations of 142 pulsars found in Parkes 20-cm multibeam pulsar survey Galactic plane. These new discoveries bring total number by to 742. In addition tabulating spin astrometric parameters, along with pulse width flux density information, we orbital characteristics for 13 binary which form part sample. Combining these results from another recent at high latitudes, have a sample 1008 normal use carry out determination their distribution...
Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; may also be linked new source classes. Until now, however, all so-called fast (FRBs) detected Parkes telescope and its 13-beam receiver, casting some concern about...
We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released $11$-year dataset from North American Nanohertz Observatory Gravitational Waves (NANOGrav). While we find no significant evidence a GWB, place constraints on GWB population of supermassive black-hole binaries, cosmic strings, and primordial GWB. For first time, that upper limits detection statistics are sensitive to Solar System ephemeris (SSE) model used, SSE errors can mimic signal. developed...
We compute upper limits on the nanohertz-frequency isotropic stochastic gravitational wave background (GWB) using 9-year data release from North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. set a GWB supermassive black hole binaries under power law, broken and free spectral coefficient GW spectrum models. place 95\% limit strain amplitude (at frequency of yr$^{-1}$) in law model $A_{\rm gw} < 1.5\times 10^{-15}$. For model, we priors derived simulations...
The discovery that at least some Fast Radio Bursts (FRBs) repeat has ruled out cataclysmic events as the progenitors of these particular bursts. FRB~121102 is most well-studied repeating FRB but despite extensive monitoring source, no underlying pattern in repetition previously been identified. Here, we present results from a radio campaign using 76-m Lovell telescope. Using pulses detected data along with literature, report detection periodic behaviour source over span five years data. We...
We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating transients (RRATs) fast bursts, at 350 MHz using the Green Bank Telescope. With Ultimate Pulsar Processing Instrument, we record 100 bandwidth divided into 4096 channels every 81.92 μs. This survey will cover entire sky visible to Telescope (δ > −40°, or 82% sky) outside Galactic Plane be sensitive enough detect slow low dispersion measure (<30 pc cm−3) millisecond (MSPs) with a 0.08...
We present high-precision timing observations spanning up to nine years for 37 millisecond pulsars monitored with the Green Bank and Arecibo radio telescopes as part of North American Nanohertz Observatory Gravitational Waves (NANOGrav) project. describe observational instrumental setups used collect data, methodology applied calculating pulse times arrival; these include novel methods measuring offsets characterizing low signal-to-noise ratio results. The time arrival data are fit a...
Abstract We present observations and timing analyses of 68 millisecond pulsars (MSPs) comprising the 15 yr data set North American Nanohertz Observatory for Gravitational Waves (NANOGrav). NANOGrav is a pulsar array (PTA) experiment that sensitive to low-frequency gravitational waves (GWs). This NANOGrav’s fifth public release, including both “narrowband” “wideband” time-of-arrival (TOA) measurements corresponding models. have added 21 MSPs extended our baselines by 3 yr, now spanning nearly...
Abstract Since the discovery of first fast radio burst (FRB) in 2007, and their confirmation as an abundant extragalactic population 2013, study these sources has expanded at incredible rate. In our 2019 review on subject, we presented a growing, but still mysterious, FRBs—60 unique sources, 2 repeating FRBs, only 1 identified host galaxy. However, few short years, new observations discoveries have given us wealth information about sources. The total FRB now stands over 600 published 24...