Adam Brazier
A5057680253- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Scientific Computing and Data Management
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Advanced Frequency and Time Standards
- Computational Physics and Python Applications
- Superconducting and THz Device Technology
- Black Holes and Theoretical Physics
- Distributed and Parallel Computing Systems
- Calibration and Measurement Techniques
- CCD and CMOS Imaging Sensors
- Satellite Image Processing and Photogrammetry
- Superconducting Materials and Applications
- Seismology and Earthquake Studies
- Cloud Computing and Resource Management
- Software Engineering Techniques and Practices
- Local Government Finance and Decentralization
Cornell University
2015-2024
Planetary Science Institute
2019-2024
Campbell Collaboration
2023
Space Science Institute
2018
Hansard Society
2009-2011
Imperial College London
2005
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...
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...
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...
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 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...
Pulsar timing arrays (PTAs) are galactic-scale gravitational wave detectors. Each individual arm, composed of a millisecond pulsar, radio telescope, and kiloparsecs-long path, differs in its properties but, aggregate, can be used to extract low-frequency (GW) signals. We present noise sensitivity analysis accompany the NANOGrav 15-year data release associated papers, along with an in-depth introduction PTA models. As first step our analysis, we characterize each pulsar set three types white...
Abstract Evidence for a low-frequency stochastic gravitational-wave background has recently been reported based on analyses of pulsar timing array data. The most likely source such is population supermassive black hole binaries, the loudest which may be individually detected in these data sets. Here we present search individual binaries NANOGrav 15 yr set. We introduce several new techniques, enhance efficiency and modeling accuracy analysis. uncovered weak evidence two candidate signals,...
Abstract The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has reported evidence the presence of an isotropic nanohertz gravitational-wave background (GWB) in its 15 yr data set. However, if GWB is produced by a population inspiraling supermassive black hole binary (SMBHB) systems, then predicted to be anisotropic, depending on distribution these systems local Universe and statistical properties SMBHB population. In this work, we search anisotropy using multiple...
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 ×...
Abstract The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform comparison GWB individual noise parameters across results reported from PTAs constitute International Pulsar Timing Array (IPTA). We show despite making choices, there is no significant...
Abstract The NANOGrav 15 yr data provide compelling evidence for a stochastic gravitational-wave (GW) background at nanohertz frequencies. simplest model-independent approach to characterizing the frequency spectrum of this signal consists simple power-law fit involving two parameters: an amplitude A and spectral index γ . In Letter, we consider next logical step beyond minimal model, allowing running (i.e., logarithmic dependence) index, <mml:math...
We report the discovery and initial follow-up of a double neutron star (DNS) system, PSR J1946$+$2052, with Arecibo L-Band Feed Array pulsar (PALFA) survey. J1946$+$2052 is 17-ms in 1.88-hour, eccentric ($e \, =\, 0.06$) orbit $\gtrsim 1.2 M_\odot$ companion. have used Jansky Very Large to localize precision 0.09 arcseconds using new phase binning mode. searched multiwavelength catalogs for coincident sources but did not find any counterparts. The improved position enabled measurement spin...
In the modern era of big data, many fields astronomy are generating huge volumes analysis which can sometimes be limiting factor in research. Fortunately, computer scientists have developed powerful data-mining techniques that applied to various fields. this paper, we present a novel artificial intelligence (AI) program identifies pulsars from recent surveys by using image pattern recognition with deep neural nets—the PICS (Pulsar Image-based Classification System) AI. The AI mimics human...
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project currently observes 43 pulsars using the Green Bank and Arecibo radio telescopes. In this work we use a subset of 17 timed span roughly five years (2005--2010). We analyze these data standard pulsar timing models, with addition time-variable dispersion measure frequency-variable pulse shape terms. Within data, perform search continuous gravitational waves from individual supermassive black hole binaries in...
We report here the Einstein@Home discovery of PSR J1913+1102, a 27.3-ms pulsar found in data from ongoing Arecibo PALFA survey. The is 4.95-hr double neutron star (DNS) system with an eccentricity 0.089. From radio timing 305-m telescope, we measure rate advance periastron to be 5.632(18) deg/yr. Assuming general relativity accurately models orbital motion, this corresponds total mass 2.875(14) solar masses, similar most massive DNS known date, B1913+16, but much smaller eccentricity. small...