Paul Demorest
A5059638806- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Advanced Frequency and Time Standards
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Superconducting and THz Device Technology
- Stellar, planetary, and galactic studies
- Superconducting Materials and Applications
- Astronomical Observations and Instrumentation
- Particle accelerators and beam dynamics
- Geophysics and Sensor Technology
- Galaxies: Formation, Evolution, Phenomena
- GNSS positioning and interference
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Computational Physics and Python Applications
- Magnetic confinement fusion research
- Space Science and Extraterrestrial Life
- Planetary Science and Exploration
- Relativity and Gravitational Theory
National Radio Astronomy Observatory
2015-2024
Campbell Collaboration
2023
Cornell University
2013-2018
Max Planck Institute for Radio Astronomy
2015
Max Planck Society
2015
University of Wisconsin–Milwaukee
2015
Netherlands Institute for Radio Astronomy
2011
University of Virginia
2011
Eureka Scientific
2011
University of California, Berkeley
2004-2010
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 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.
The precise localization of the repeating fast radio burst (FRB 121102) has provided first unambiguous association (chance coincidence probability $p\lesssim3\times10^{-4}$) an FRB with optical and persistent counterpart. We report on imaging spectroscopy counterpart find that it is extended ($0.6^{\prime\prime}-0.8^{\prime\prime}$) object displaying prominent Balmer [OIII] emission lines. Based spectrum line ratios, we classify as a low-metallicity, star-forming, $m_{r^\prime} = 25.1$ AB...
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...
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...
The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with unique combination of high angular resolution ($\approx$2.5"), sensitivity (a 1$\sigma$ goal 70 $\mu$Jy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). first observations began September 2017, observing for will finish 2024. VLASS use approximately 5500 hours on Karl G. Jansky (VLA) to cover whole visible VLA (Declination $>-40^{\circ}$), total...
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...
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...
ABSTRACT We analyze 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. make 14 significant measurements of Shapiro delay, including new detections four pulsar-binary systems (PSRs J0613−0200, J2017+0603, J2302+4442, and J2317+1439), derive estimates binary-component masses orbital inclination these MSP-binary systems. find a wide range pulsar masses, with values as low <?CDATA...
Abstract The millisecond-duration radio flashes known as fast bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (∼100 mas precision) of FRB 121102 using Very Large Array has led to its unambiguous association with persistent and optical counterparts, identification host galaxy. However, even more precise is needed in order probe direct physical relationship between millisecond themselves associated emission. Here, we report...
We present an analysis of high-precision pulsar timing data taken as part the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. have observed 17 pulsars a span roughly five years using Green Bank and Arecibo radio telescopes. analyze these standard models, with addition time-variable dispersion measure frequency-variable pulse shape terms. Sub-microsecond residuals are obtained in nearly all cases, best rms this set ∼30–50 ns. methods analyzing post-fit...
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...
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...
The NANOGrav 15-year data set shows evidence for the presence of a low-frequency gravitational-wave background (GWB). While many physical processes can source such gravitational waves, here we analyze signal as coming from population supermassive black hole (SMBH) binaries distributed throughout Universe. We show that astrophysically motivated models SMBH binary populations are able to reproduce both amplitude and shape observed spectrum. multiple model variations GWB spectrum at our current...
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...
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 search for an isotropic stochastic gravitational-wave background (GWB) in the 12.5 yr pulsar-timing data set collected by North American Nanohertz Observatory Gravitational Waves. Our analysis finds strong evidence of a process, modeled as power law, with common amplitude and spectral slope across pulsars. Under our fiducial model, Bayesian posterior f −2/3 power-law spectrum, expressed characteristic GW strain, has median 1.92 × 10 −15 5%–95% quantiles 1.37–2.67 at reference...
We present results of the coordinated observing campaign that made first subarcsecond localization a Fast Radio Burst, FRB 121102. During this campaign, we simultaneous detection an burst by multiple telescopes: VLA at 3 GHz and Arecibo Observatory 1.4 GHz. Of nine bursts detected Very Large Array GHz, four had coverage other observatories. use multi-observatory constraints modeling seen only to confirm earlier showing spectra are not well modeled power law. find characterized ~500 MHz...