Explanipedia

Upper Limits on Radio Emission from the K2-18 System Open

Chenoa D. Tremblay, Alex Andersson, Megan G. Li, R. J. Beswick, J. F. Radcliffe , et al. · 2025

Stellar and planetary magnetic fields play a crucial role in the habitability of a planet and the integrity of its atmosphere. The recently claimed detection of biosignatures, methane, carbon dioxide and dimethyl sulfide/disulfide, in the …

Evidence for a Hot Galactic Halo around the Andromeda Galaxy Using Fast Radio Bursts along Two Sightlines Open

Reshma Anna-Thomas, Casey Law, Eric W. Koch, Alexa C. Gordon, Kritti Sharma , et al. · 2025

Fast radio bursts (FRBs) are millisecond-duration radio transients that serve as unique probes of ionizedextragalactic matter. We report the discovery and localization of two FRBs piercing the Andromeda galaxy (M31) with the realfast trans…

CHIME-o-Grav: Wideband Timing of Four Millisecond Pulsars from the NANOGrav 15-yr dataset Open

Gabriella Agazie, D. L. Kaplan, Abhimanyu Susobhanan, I. H. Stairs, Deborah C. Good , et al. · 2025

Wideband timing of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) datasets, where a single time-of-arrival (TOA) and a single dispersion measure (DM) are measured using the entire bandwidth of each observation,…

Searching for Exotrojans in Pulsar Binary Systems Open

Jacob Taylor, Emmanuel Fonseca, Lankeswar Dey, S. V. Zharikov, A. Yu. Kirichenko , et al. · 2025

Trojan asteroids are found in the equilateral triangle Lagrange points of the Sun-Jupiter system in great number, though they also exist less prolifically in other Sun-planet systems. Despite up to planetary mass Trojans being predicted in…

The NANOGrav 15-Year Data Set: Improved Timing Precision With VLBI Astrometric Priors Open

Sophia V. Sosa Fiscella, Michael T. Lam, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald , et al. · 2025

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…

Pulsar Cyclic Spectroscopy in the Partial-deconvolution Regime: Benefits and Limitations Open

Jacob E. Turner, Timothy Dolch, Paul Demorest, Ryan S. Lynch, Daniel R. Stinebring , et al. · 2025

We explore possible advantages of cyclic spectroscopy for observations of pulsars in instances where full cyclic deconvolution is not possible. We compute cyclic merits and full-deconvolution regime boundaries for pulsars observed by NANOG…

Long-term Astrometric Monitoring of the Galactic Center Magnetar PSR J1745−2900 Open

Geoffrey C. Bower, Adam T. Deller, Paul Demorest, Jason Dexter, A. Brunthaler , et al. · 2025

We present new astrometric observations of the Galactic center magnetar PSR J1745−2900 with the Very Long Baseline Array. Combined with previously published measurements in 10 epochs that spanned 477 days, the complete data set consists of…

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…

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

Michael T. Lam, D. L. Kaplan, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald , et al. · 2025

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 …

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…

Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open

William Fiore, M. A. McLaughlin, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald , et al. · 2025

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…

The Anomalous Acceleration of PSR J2043+1711: Long-period Orbital Companion or Stellar Flyby? Open

Thomas Donlon, Sukanya Chakrabarti, Michael T. Lam, Daniel Huber, Daniel Hey , et al. · 2025

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 …

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…

COSMIC’s Large-scale Search for Technosignatures during the VLA Sky Survey: Survey Description and First Results Open

Chenoa D. Tremblay, J. Sofair, Lucille Steffes, Talon Myburgh, Daniel Czech , et al. · 2025

Developing algorithms to search through data efficiently is a challenging part of searching for signs of technology beyond our solar system. We have built a digital signal processing system and computer cluster on the backend of the Karl G…

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…

Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open

William Fiore, M. A. McLaughlin, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald , et al. · 2024

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…

Exploring Pulsar Timing Precision: A Comparative Study of Polarization Calibration Methods for NANOGrav Data from the Green Bank Telescope Open

Lankeswar Dey, M. A. McLaughlin, Haley M. Wahl, Paul Demorest, Zaven Arzoumanian , et al. · 2024

Pulsar timing array experiments have recently uncovered evidence for a nanohertz gravitational wave background by precisely timing an ensemble of millisecond pulsars. The next significant milestones for these experiments include characteri…

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…

An Unidentified Fermi Source Emitting Radio Bursts in the Galactic Bulge Open

Reshma Anna-Thomas, Sarah Burke-Spolaor, Casey Law, F. K. Schinzel, K.K. Aggarwal , et al. · 2024

We report on the detection of radio bursts from the Galactic bulge using the real-time transient detection and localization system, realfast . The pulses were detected commensally on the Karl G. Jansky Very Large Array during a survey of u…

The NANOGrav 15 yr Data Set: Chromatic Gaussian Process Noise Models for Six Pulsars Open

Bjorn Larsen, Chiara M. F. Mingarelli, Jeffrey S. Hazboun, A. Chalumeau, Deborah C. Good , et al. · 2024

Pulsar timing arrays (PTAs) are designed to detect low-frequency gravitational waves (GWs). GWs induce achromatic signals in PTA data, meaning that the timing delays do not depend on radio frequency. However, pulse arrival times are also a…

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…

PINT: Maximum-likelihood Estimation of Pulsar Timing Noise Parameters Open

Abhimanyu Susobhanan, D. L. Kaplan, Anne M. Archibald, Jing Luo, Paul S. Ray , et al. · 2024

PINT is a pure-Python framework for high-precision pulsar timing developed on top of widely used and well-tested Python libraries, supporting both interactive and programmatic data analysis workflows. We present a new frequentist framework…

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…

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