Results 81 to 90 of about 6,025 (156)

Refractive interstellar scintillation in 1741-038

The Astrophysical Journal, 1986
A year of VLA observations of the radio source 1741-038 show that it exhibits pronounced variability at 1.49, 15, and 22 GHz, and somewhat reduced activity at 4.9 GHz. We interpret the unusually strong 1.49 GHz variability as due to refractive interstellar scintillation, and the high-frequency variability as being intrinsic to the source.
R. M. Hjellming, Ramesh Narayan
openaire   +1 more source

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

The Astrophysical Journal
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.
Abra Geiger, James M. Cordes, Michael T. Lam, Stella Koch Ocker, Shami Chatterjee, Zaven Arzoumanian, Ava L. Battaglia, Harsha Blumer, Paul R. Brook, Olivia A. Combs, H. Thankful Cromartie, Megan E. DeCesar, Paul B. Demorest, Timothy Dolch, Justin A. Ellis, Robert D. Ferdman, Elizabeth C. Ferrara, Emmanuel Fonseca, Nate Garver-Daniels, Peter A. Gentile, Deborah C. Good, Megan L. Jones, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Maura A. McLaughlin, Cherry Ng, David J. Nice, Timothy T. Pennucci, Nihan S. Pol, Scott M. Ransom, Renée Spiewak, Ingrid H. Stairs, Kevin Stovall, Joseph K. Swiggum, Sarah J. Vigeland   +35 more
doaj   +1 more source

Observations of Intrahour Variable Quasars: Scattering in our Galactic Neighbourhood

, 2007
Interstellar scintillation (ISS) has been established as the cause of the random variations seen at centimetre wavelengths in many compact radio sources on timescales of a day or less.
A. K. Tzioumis, Cimo G., D. L. Jauncey, H. E. Bignall, J. E. J. Lovell, J.-P. Macquart, L. Kedziora-Chudczer, Witzel A.   +7 more
core   +1 more source

Plasma Lensing Modeling of Substructures on Pulsar Scintillation Screens

The Astronomical Journal
Radio pulsars, as highly coherent point sources, serve as powerful probes of the ionized interstellar medium (IISM). Pulsar scintillation observations have revealed inverted arclets on the secondary spectrum, indicating quasilinearly aligned images ...
Zhu Xu, Xun Shi
doaj   +1 more source

Resolving the Emission Regions of the Crab Pulsar’s Giant Pulses. II. Evidence for Relativistic Motion

The Astrophysical Journal, 2023
The Crab Pulsar is the prime example of an emitter of giant pulses. These short, very bright pulses are thought to originate near the light cylinder, at ∼1600 km from the pulsar.
Rebecca Lin, Marten H. van Kerkwijk, Robert Main, Nikhil Mahajan, Ue-Li Pen, Franz Kirsten   +5 more
doaj   +1 more source

Stokes Phenomena in Lensing

The Astrophysical Journal
As lensing of coherent astrophysical sources, e.g., pulsars, fast radio bursts, and gravitational waves, becomes observationally relevant, the mathematical framework of Picard–Lefschetz theory has recently been introduced to fully account for wave optics
Xun Shi
doaj   +1 more source

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

The Astrophysical Journal
We use the upgraded Giant Metrewave Radio Telescope (uGMRT) to measure scintillation arc properties in six bright canonical pulsars with simultaneous dual-frequency coverage.
Jacob E. Turner, Bhal Chandra Joshi, Maura A. McLaughlin, Daniel R. Stinebring   +3 more
doaj   +1 more source

Size of the Vela Pulsar's Emission Region at 18 cm Wavelength

, 2012
We present measurements of the linear diameter of the emission region of the Vela pulsar at observing wavelength lambda=18 cm. We infer the diameter as a function of pulse phase from the distribution of visibility on the Mopra-Tidbinbilla baseline. As we
A. K. Tzioumis, B. Carlson, Bevington, C. R. Gwinn, C. S. Flanagan, Cheng, D. del Rizzo, D. L. Jauncey, Dodson, Dyks, Flatté, Gangadhara, Goodman, Gruzinov, Gupta, Gwinn, Gwinn, Gwinn, Gwinn, Gwinn, Gwinn, H. Hirabayashi, H. Kobayashi, Harding, Hirano, J. E. Reynolds, J. F. H. Quick, Johnson, Johnston, Kern, Lai, Lyutikov, M. D. Johnson, Macquart, Manchester, Muslimov, P. G. Edwards, P. M. McCulloch, Press, Romani, S. Dougherty, Spitkovsky, Thompson, Y. Murata   +43 more
core   +1 more source

Lensing Point-spread Function of Coherent Astrophysical Sources and Nontrivial Wave Effects

The Astrophysical Journal
Most research on astrophysical lensing has been conducted using the geometric optics framework, where there exists a clear concept of lensing images. However, wave optics effects can be important for coherent sources, e.g., pulsars, fast radio bursts ...
Xun Shi
doaj   +1 more source

A Direct Measurement of the Electron Density Turbulence Parameter C1 and Implications for the Emission Size of Magnetar XTE J1810-197

The Astrophysical Journal Letters
We report a direct measurement of the electron density turbulence parameter C _1 , enabled by 550–750 MHz baseband observations with the upgraded Giant Metrewave Radio Telescope.
Visweshwar Ram Marthi, Yogesh Maan
doaj   +1 more source