Kathryn Crowter
A5047363564- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Advanced Frequency and Time Standards
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Atomic and Subatomic Physics Research
- Black Holes and Theoretical Physics
- Geophysics and Sensor Technology
- High-pressure geophysics and materials
- GNSS positioning and interference
- Superconducting and THz Device Technology
- Seismology and Earthquake Studies
- Image Processing Techniques and Applications
- Geological and Geophysical Studies
- Dark Matter and Cosmic Phenomena
- Ionosphere and magnetosphere dynamics
- Mechanical and Optical Resonators
- CCD and CMOS Imaging Sensors
- Statistical and numerical algorithms
University of British Columbia
2015-2024
Campbell Collaboration
2023
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...
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...
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...
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...
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...
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...
Symmetries play an important role in modern theories of gravity. The strong equivalence principle (SEP) constitutes a collection gravitational symmetries which are all implemented by general relativity. Alternative theories, however, generally expected to violate some aspects SEP. We test three SEP using observed change rates the orbital period and eccentricity binary pulsar J1713+0747: 1. constant's constancy as part locational invariance gravitation; 2. post-Newtonian parameter...
We analyze dispersion measure (DM) variations of 37 millisecond pulsars in the 9-year NANOGrav data release and constrain sources these variations. Variations are significant for nearly all pulsars, with characteristic timescales comparable to or even shorter than average spacing between observations. Five have periodic annual variations, 14 monotonically increasing decreasing trends, 13 show both effects. Several correlations DM excesses lines sight that pass close Sun. Mapping as a...
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 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...
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...
We report 21-year timing of one the most precise pulsars: PSR J1713+0747. Its pulse times arrival are well modeled by a comprehensive pulsar binary model including its three-dimensional orbit and noise that incorporates short- long-timescale correlated such as jitter red noise. residuals have weighted root mean square ∼92 ns. The new data set allows us to update improve previous measurements system properties, masses neutron star (1.31 ± 0.11 M⊙) companion white dwarf (0.286 0.012 their...
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...