A5010900695- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- High-pressure geophysics and materials
- Geophysics and Sensor Technology
- Statistical and numerical algorithms
- Seismic Waves and Analysis
- Atomic and Subatomic Physics Research
- Black Holes and Theoretical Physics
- Arctic and Antarctic ice dynamics
- Superconducting and THz Device Technology
- Advanced Frequency and Time Standards
- Seismology and Earthquake Studies
- Computational Physics and Python Applications
- Astronomical Observations and Instrumentation
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Biomedical and Engineering Education
- Galaxies: Formation, Evolution, Phenomena
- Genetics, Bioinformatics, and Biomedical Research
- Dark Matter and Cosmic Phenomena
University of Washington Bothell
2017-2024
Campbell Collaboration
2023
Humboldt-Universität zu Berlin
2021
Brownsville Public Library
2015-2021
University of Washington
2019-2020
Physical Sciences (United States)
2019
The University of Texas Rio Grande Valley
2016-2018
Montana Space Grant Consortium
2012
Montana State University
2007-2011
NOAA National Environmental Satellite Data and Information Service
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 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...
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 $\alpha -0.5 \pm 0.5$,...
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...
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 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...
The first terrestrial gravitational wave interferometers have dramatically underscored the scientific value of observing Universe through an entirely different window, and folding this new channel information with traditional astronomical data for a multimessenger view. Laser Interferometer Space Antenna (LISA) will broaden reach astronomy by conducting survey millihertz sky, detecting tens thousands individual astrophysical sources ranging from white-dwarf binaries in our own galaxy to...
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...
Pulsar timing array collaborations, such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), are seeking to detect nanohertz gravitational waves emitted by supermassive black hole binaries formed in aftermath of galaxy mergers. We have searched continuous from individual circular using NANOGrav's recent 12.5-year data set. created new methods accurately model uncertainties on pulsar distances our analysis, and we implemented techniques account a common red noise...
Gravitational-wave astronomy has revolutionized humanity's view of the universe, a revolution driven by observations that no other field can make. This white paper describes an observatory builds on decades investment National Science Foundation and will drive discovery for to come: Cosmic Explorer. Major discoveries in are three related improvements: better sensitivity, higher precision, opening new observational windows. Explorer promises all deliver order-of-magnitude greater sensitivity...
Abstract Recently we found compelling evidence for a gravitational-wave background with Hellings and Downs (HD) correlations in our 15 yr data set. These describe gravitational waves as predicted by general relativity, which has two transverse polarization modes. However, more metric theories of gravity can have additional modes, produce different interpulsar correlations. In this work, search the NANOGrav set quadrupolar HD scalar-transverse (ST) We find that are best fit to no significant...
Abstract We present the results of a Bayesian search for gravitational wave (GW) memory in NANOGrav 12.5 yr data set. find no convincing evidence any signals this Bayes factor 2.8 favor model that includes signal and common spatially uncorrelated red noise (CURN) compared to including only CURN. However, further investigation shows disproportionate amount support comes from three dubious pulsars. Using more flexible red-noise these pulsars reduces 1.3. Having found compelling evidence, we go...
Pulsar timing arrays (PTAs) use an array of millisecond pulsars to search for gravitational waves in the nanohertz regime pulse time arrival data. This paper presents rigorous tests PTA methods, examining their consistency across relevant parameter space. We discuss updates 15-year isotropic gravitational-wave background analyses and corresponding code representations. Descriptions internal structure flagship algorithms enterprise ptmcmcsampler are given facilitate understanding likelihood...
Abstract The microphysical characteristics, radiative impact, and life cycle of a long-lived, surface-based mixed-layer, mixed-phase cloud with an average temperature approximately −20°C are presented discussed. was observed during the Surface Heat Budget Arctic experiment (SHEBA) from 1 to 10 May 1998. Vertically resolved properties liquid ice phases retrieved using remote sensors, utilize adiabatic assumption for component, aided by validated aircraft measurements 4 7 May. radar...
The Mock LISA Data Challenges are a program to demonstrate data-analysis capabilities and encourage their development. Each round of challenges consists one or more datasets containing simulated instrument noise gravitational waves from sources undisclosed parameters. Participants analyze the report best-fit solutions for source Here we present results third challenge, issued in April 2008, which demonstrated positive recovery signals chirping galactic binaries, spinning...
Observations indicate that nearly all galaxies contain supermassive black holes (SMBHs) at their centers. When merge, component form SMBH binaries (SMBHBs), which emit low-frequency gravitational waves (GWs) can be detected by pulsar timing arrays (PTAs). We have searched the recently-released North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 11-year data set GWs from individual SMBHBs in circular orbits. As we did not find strong evidence our data, placed 95\% upper...
We search NANOGrav's 12.5-year data set for evidence of a gravitational wave background (GWB) with all the spatial correlations allowed by general metric theories gravity. find no substantial in favor existence such our data. that scalar-transverse (ST) yield signal-to-noise ratios and Bayes factors are higher than quadrupolar (tensor transverse, TT) correlations. Specifically, we ST ratio 2.8 preferred over TT (Hellings Downs correlations) Bayesian odds about 20:1. However, significance is...
The mergers of supermassive black hole binaries (SMBHBs) promise to be incredible sources gravitational waves (GWs). While the oscillatory part merger waveform will outside frequency sensitivity range pulsar timing arrays (PTAs), non-oscillatory GW memory effect is detectable. Further, any burst produce memory, making a useful probe unmodeled exotic and new physics. We searched North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 11-year data set memory. This dataset...
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 dataset. 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 methods bases...