Paul S. Ray
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View article: The NANOGrav 15-Year Data Set: Improved Timing Precision With VLBI Astrometric Priors
The NANOGrav 15-Year Data Set: Improved Timing Precision With VLBI Astrometric Priors Open
Accurate pulsar astrometric estimates play an essential role in almost all high-precision pulsar timing experiments. Traditional pulsar timing techniques refine these estimates by including them as free parameters when fitting a model to o…
View article: The NANOGrav 15-year Data Set: Search for Gravitational Scattering of Pulsars by Free-Floating Objects in Interstellar Space
The NANOGrav 15-year Data Set: Search for Gravitational Scattering of Pulsars by Free-Floating Objects in Interstellar Space Open
Free-floating objects (FFOs) in interstellar space$-$rogue planets, brown dwarfs, and large asteroids that are not gravitationally bound to any star$-$are expected to be ubiquitous throughout the Milky Way. Recent microlensing surveys have…
View article: The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory
The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory Open
We present the results of a search for nonlinear gravitational-wave (GW) memory in the NANOGrav 15 yr data set. We find no significant evidence for memory signals in the data set, with a maximum Bayes factor of 3.1 in favor of a model incl…
View article: A NICER view of the 1.4 solar-mass edge-on pulsar PSR J0614--3329
A NICER view of the 1.4 solar-mass edge-on pulsar PSR J0614--3329 Open
Four neutron star radius measurements have already been obtained by modeling the X-ray pulses of rotation-powered millisecond pulsars observed by the Neutron Star Interior Composition ExploreR (NICER). We report here the radius measurement…
View article: The NANOGrav 15-Year Data Set: A Case Study for Simplified Dispersion Measure Modeling for PSR J1455-3330 and the Impact on Gravitational Wave Sensitivity
The NANOGrav 15-Year Data Set: A Case Study for Simplified Dispersion Measure Modeling for PSR J1455-3330 and the Impact on Gravitational Wave Sensitivity Open
Evidence for a low-frequency gravitational-wave background using pulsar timing arrays has generated recent interest into its underlying contributing sources. However, multiple investigations have seen that the significance of the evidence …
View article: The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations
The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations Open
Pulsar timing array observations have found evidence for an isotropic gravitational-wave background with the Hellings–Downs angular correlations between pulsar pairs. This interpretation hinges on the measured shape of the angular correlat…
View article: Discovery and Timing of Four <i>γ</i>-Ray Millisecond Pulsars
Discovery and Timing of Four <i>γ</i>-Ray Millisecond Pulsars Open
We discovered four millisecond pulsars (MSPs) in searches of 80 γ -ray sources conducted from 2015 to 2017 with the Murriyang radio telescope of the Parkes Observatory. We provide an overview of the survey and focus on the results of a fol…
View article: Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data
Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open
Pulse profile stability is a central assumption of standard pulsar timing methods. Thus, it is important for pulsar timing array experiments such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) to account for…
View article: The Anomalous Acceleration of PSR J2043+1711: Long-period Orbital Companion or Stellar Flyby?
The Anomalous Acceleration of PSR J2043+1711: Long-period Orbital Companion or Stellar Flyby? Open
Based on the rate of change of its orbital period, PSR J2043+1711 has a substantial peculiar acceleration of 3.5 ± 0.8 mm s –1 yr –1 , which deviates from the acceleration predicted by equilibrium Milky Way (MW) models at a 4 σ level. The …
View article: The NANOGrav 15-year Data Set: Search for Gravitational Wave Memory
The NANOGrav 15-year Data Set: Search for Gravitational Wave Memory Open
We present the results of a search for nonlinear gravitational wave memory in the NANOGrav 15-year data set. We find no significant evidence for memory signals in the dataset, with a maximum Bayes factor of 3.1 in favor of a model includin…
View article: PSR J1947−1120: A New Huntsman Millisecond Pulsar Binary
PSR J1947−1120: A New Huntsman Millisecond Pulsar Binary Open
We present the discovery of PSR J1947–1120, a new huntsman millisecond pulsar with a red giant companion star in a 10.3 day orbit. This pulsar was found via optical, X-ray, and radio follow-up of the previously unassociated γ -ray source 4…
View article: PSR J1947-1120: A New Huntsman Millisecond Pulsar Binary
PSR J1947-1120: A New Huntsman Millisecond Pulsar Binary Open
We present the discovery of PSR J1947-1120, a new huntsman millisecond pulsar with a red giant companion star in a 10.3 d orbit. This pulsar was found via optical, X-ray, and radio follow-up of the previously unassociated gamma-ray source …
View article: The NANOGrav 15 yr Data Set: Running of the Spectral Index
The NANOGrav 15 yr Data Set: Running of the Spectral Index Open
The NANOGrav 15 yr data provide compelling evidence for a stochastic gravitational-wave (GW) background at nanohertz frequencies. The simplest model-independent approach to characterizing the frequency spectrum of this signal consists of a…
View article: The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array
The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open
Evidence has emerged for a stochastic signal correlated among 67 pulsars within the 15 yr pulsar-timing data set compiled by the NANOGrav collaboration. Similar signals have been found in data from the European, Indian, Parkes, and Chinese…
View article: The NANOGrav 15 yr Data Set: Looking for Signs of Discreteness in the Gravitational-wave Background
The NANOGrav 15 yr Data Set: Looking for Signs of Discreteness in the Gravitational-wave Background Open
The cosmic merger history of supermassive black hole binaries (SMBHBs) is expected to produce a low-frequency gravitational wave background (GWB). Here we investigate how signs of the discrete nature of this GWB can manifest in pulsar timi…
View article: Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data
Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open
Pulse profile stability is a central assumption of standard pulsar timing methods. Thus, it is important for pulsar timing array experiments such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) to account for…
View article: The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array
The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open
Evidence has emerged for a stochastic signal correlated among 67 pulsars within the 15-year pulsar-timing data set compiled by the NANOGrav collaboration. Similar signals have been found in data from the European, Indian, Parkes, and Chine…
View article: The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations
The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations Open
Pulsar timing array observations have found evidence for an isotropic gravitational wave background with the Hellings-Downs angular correlations, expected from general relativity. This interpretation hinges on the measured shape of the ang…
View article: The STROBE-X wide field monitor instrument
The STROBE-X wide field monitor instrument Open
International audience
View article: Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries
Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries Open
The detection of a stochastic gravitational wave background by pulsar timing arrays suggests the presence of a supermassive black hole binary population. Although the observed spectrum generally matches predictions for orbital evolution dr…
View article: A NICER View of PSR J1231−1411: A Complex Case
A NICER View of PSR J1231−1411: A Complex Case Open
Recent constraints on neutron star mass and radius have advanced our understanding of the equation of state (EOS) of cold dense matter. Some of them have been obtained by modeling the pulses of three millisecond X-ray pulsars observed by t…
View article: Sharp Periodic Flares and Long-term Variability in the High-mass X-Ray Binary XTE J1829−098 from RXTE PCA, Swift BAT, and MAXI Observations
Sharp Periodic Flares and Long-term Variability in the High-mass X-Ray Binary XTE J1829−098 from RXTE PCA, Swift BAT, and MAXI Observations Open
XTE J1829−098 is a transient X-ray pulsar with a period of ∼7.8 s. It is a candidate Be star system, although the evidence for this is not yet definitive. We investigated the twenty-year-long X-ray light curve using the Rossi X-ray Timing …
View article: The STROBE-X Wide Field Monitor Instrument
The STROBE-X Wide Field Monitor Instrument Open
The Wide Field Monitor (WFM) is one of the three instruments on the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) mission, which was proposed in response to the NASA 2023 call for a probe class mission. Th…
View article: The STROBE-X Low Energy Modular Array (LEMA) Instrument
The STROBE-X Low Energy Modular Array (LEMA) Instrument Open
The Low Energy Modular Array (LEMA) is one of three instruments that compose the STROBE-X mission concept. The LEMA is a large effective-area, high throughput, non-imaging pointed instrument based on the X-ray Timing Instrument of the Neut…
View article: STROBE-X High Energy Modular Array (HEMA)
STROBE-X High Energy Modular Array (HEMA) Open
The High Energy Modular Array (HEMA) is one of three instruments that compose the STROBE-X mission concept. The HEMA is a large-area, high-throughput non-imaging pointed instrument based on the Large Area Detector developed as part of the …
View article: Front-End ASIC for the STROBE-X HEMA and WFM Detectors: Concept and Design
Front-End ASIC for the STROBE-X HEMA and WFM Detectors: Concept and Design Open
This paper presents the NSX front-end ASIC, being developed to read charge signals from the HEMA and WFM X-ray detectors for the STROBE-X mission. The ASIC reads out signals from up to 64 anodes of linear Silicon Drift Detectors (SDDs). Wh…