Explanipedia

Deep Synoptic Array Science: Searching for Long Duration Radio Transients with the DSA-110 Open

Myles B. Sherman, Nikita Kosogorov, Casey Law, Vikram Ravi, Jakob T. Faber , et al. · 2025

We describe the design and commissioning tests for the DSA-110 Not-So-Fast Radio Burst (NSFRB) search pipeline, a 1.4 GHz image-plane single-pulse search sensitive to 134 ms-160.8 s radio bursts. Extending the pulse width range of the Fast…

A HyperFlash and ÈCLAT view of the local environment and energetics of the repeating FRB 20240619D Open

O. S. Ould-Boukattine, A J Cooper, J. W. T. Hessels, D. M. Hewitt, Stella Koch Ocker , et al. · 2025

Time-variable propagation effects provide a window into the local plasma environments of repeating fast radio burst (FRB) sources. Here we report high-cadence observations of FRB 20240619D, as part of the HyperFlash and ÉCLAT programs. We …

ASKAP J144834−685644: a newly discovered long period radio transient detected from radio to X-rays Open

Akash Anumarlapudi, D. L. Kaplan, N. Rea, Nicolas Erasmus, Daniel D. Kelson , et al. · 2025

Long-period radio transients (LPTs) are an emerging group of radio transients that show periodic polarized radio bursts with periods varying from a few minutes to a few hours. Fewer than a dozen LPTs have been detected so far, and their or…

Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars Open

Stella Koch Ocker, Mandy C. Chen, S. Peng Oh, Prateek Sharma · 2025

The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, whic…

The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2025

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…

The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327 Open

Abra Geiger, J. M. Cordes, Michael T. Lam, Stella Koch Ocker, Shami Chatterjee , et al. · 2025

Free electrons in the interstellar medium refract and diffract radio waves along multiple paths, resulting in angular and temporal broadening of radio pulses that limits pulsar timing precision. We determine multifrequency, multiepoch scat…

The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327 Open

Abra Geiger, James M. Cordes, Michael T. Lam, Stella Koch Ocker, Shami Chatterjee , et al. · 2025

Free electrons in the interstellar medium refract and diffract radio waves along multiple paths, resulting in angular and temporal broadening of radio pulses that limits pulsar timing precision. We determine multifrequency, multiepoch scat…

Detection of X-ray emission from a bright long-period radio transient Open

Ziteng Wang, N. Rea, Tong Bao, D. L. Kaplan, E. Lenc , et al. · 2025

Recently, a class of long-period radio transients (LPTs) has been discovered, exhibiting emission thousands of times longer than radio pulsars^1-5. These findings, enabled by advances in wide-field radio surveys, challenge existi…

The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2025

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…

The NANOGrav 15-year Data Set: Search for Gravitational Wave Memory Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2025

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…

The emission of interpulses by a 6.45-h-period coherent radio transient Open

Yong-Sam Lee, Manisha Caleb, Tara Murphy, E. Lenc, D. L. Kaplan , et al. · 2025

The NANOGrav 15 yr Data Set: Running of the Spectral Index Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2025

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…

The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2025

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…

The NANOGrav 15 yr Data Set: Looking for Signs of Discreteness in the Gravitational-wave Background Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2024

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…

Detection of X-ray Emission from a Bright Long-Period Radio Transient Open

Ziteng Wang, Nanda Rea, Tong Bao, David L. Kaplan, E. Lenc , et al. · 2024

Recently, a class of long-period radio transients (LPTs) has been discovered, exhibiting emission on timescales thousands of times longer than radio pulsars. Several models had been proposed implicating either a strong magnetic field neutr…

The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2024

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…

The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations Open

Gabriella Agazie, J. G. Baier, P. T. Baker, B. Bécsy, Laura Blecha , et al. · 2024

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…

Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries Open

Yifan Chen, Matthias Daniel, Daniel J. D’Orazio, Andrea Mitridate, Laura Sagunski , et al. · 2024

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…

Probing the Low-velocity Regime of Nonradiative Shocks with Neutron Star Bow Shocks Open

Stella Koch Ocker, Maren Cosens · 2024

Nonradiative shocks accelerate particles and heat astrophysical plasmas. While supernova remnants are the most well-studied example, neutron star (NS) bow shocks are also nonradiative and Balmer dominated. NS bow shocks are likely ubiquito…

Bow Shock and Local Bubble Plasma Unveiled by the Scintillating Millisecond Pulsar J0437$-$4715 Open

Daniel J. Reardon, Robert Main, Stella Koch Ocker, R. M. Shannon, M. Bailes , et al. · 2024

The ionized interstellar medium contains au-scale (and below) structures that scatter radio waves from pulsars, resulting in scintillation. Power spectral analysis of scintillation often shows parabolic arcs, with curvatures that encode th…

Implications for Galactic Electron Density Structure from Pulsar Sightlines Intersecting H ii Regions Open

Stella Koch Ocker, L. D. Anderson, T. Joseph W. Lazio, J. M. Cordes, Vikram Ravi · 2024

Recent radio surveys have revealed pulsars with dispersion and scattering delays induced by ionized gas that are larger than the rest of the observed pulsar population, in some cases with electron column densities (or dispersion measures, …

A gas-rich cosmic web revealed by the partitioning of the missing baryons Open

Liam Connor, Vikram Ravi, Kritti Sharma, Stella Koch Ocker, Jakob T. Faber , et al. · 2024

Approximately half of the Universe's dark matter resides in collapsed halos; significantly less than half of the baryonic matter (protons and neutrons) remains confined to halos. A small fraction of baryons are in stars and the interstella…

Correction to: Searching for magnetar binaries disrupted by core-collapse supernovae Open

Myles B. Sherman, Vikram Ravi, Kareem El-Badry, Kritti Sharma, Stella Koch Ocker , et al. · 2024

Preferential Occurrence of Fast Radio Bursts in Massive Star-Forming Galaxies Open

Kritti Sharma, Vikram Ravi, Liam Connor, Casey Law, Stella Koch Ocker , et al. · 2024

Fast Radio Bursts (FRBs) are millisecond-duration events detected from beyond the Milky Way. FRB emission characteristics favor highly magnetized neutron stars, or magnetars, as the sources, as evidenced by FRB-like bursts from a galactic …

Probing the low-velocity regime of non-radiative shocks with neutron star bow shocks Open

Stella Koch Ocker, Maren Cosens · 2024

Non-radiative shocks accelerate particles and heat astrophysical plasmas. While supernova remnants are the most well-studied example, neutron star (NS) bow shocks are also non-radiative and Balmer-dominated. NS bow shocks are likely ubiqui…

A Cyclic Spectroscopy Scintillation Study of PSR B1937+21. I. Demonstration of Improved Scintillometry Open

Jacob E. Turner, Timothy Dolch, J. M. Cordes, Stella Koch Ocker, Daniel R. Stinebring , et al. · 2024

We use cyclic spectroscopy to perform high-frequency resolution analyses of multihour baseband Arecibo observations of the millisecond pulsar PSR B1937+21. This technique allows for the examination of scintillation features in far greater …

The NANOGrav 15 yr Data Set: Running of the Spectral Index Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2024

The NANOGrav 15-year data provides 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 i…

Erratum: “The NANOGrav 15 yr Data Set: Search for Signals from New Physics” (2023, ApJL 951 L11) Open

Adeela Afzal, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian , et al. · 2024

Erratum: "The NANOGrav 15 yr Data Set: Search for Signals from New Physics" (2023, ApJL 951 L11), Adeela Afzal, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, Paul T. Baker, Bence Bécsy, Jose Juan Blanco-Pillad…

The NANOGrav 15 yr data set: Posterior predictive checks for gravitational-wave detection with pulsar timing arrays Open

Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, J. G. Baier , et al. · 2024

Pulsar-timing-array experiments have reported evidence for a stochastic background of nanohertz gravitational waves consistent with the signal expected from a population of supermassive--black-hole binaries. Their analyses assume power-law…

Implications for Galactic Electron Density Structure from Pulsar Sightlines Intersecting HII Regions Open

Stella Koch Ocker, L. D. Anderson, J. Lazio, J. M. Cordes, Vikram Ravi · 2024

Recent radio surveys have revealed pulsars with dispersion and scattering delays induced by ionized gas that are larger than the rest of the observed pulsar population, in some cases with electron column densities (or dispersion measures; …

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