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The VLBI Global Observing System, which is the next generation of geodetic VLBI and is called VGOS, observes simultaneously at four frequency bands in the range 3.0--10.7 GHz (expected to be extended to 14 GHz). Because source structure…

Astrophysics of Galaxies · Physics 2022-07-20 Ming H. Xu , Tuomas Savolainen , James M. Anderson , Niko Kareinen , Nataliya Zubko , Susanne Lunz , Harald Schuh

Precision astrometry is an integral component of successful pulsar timing campaigns. Astrometric parameters are commonly derived by fitting them as parameters of a timing model to a series of pulse times of arrival (TOAs). TOAs measured to…

High Energy Astrophysical Phenomena · Physics 2013-12-12 D. R. Madison , S. Chatterjee , J. M. Cordes

We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q,…

Given the possible repetitive nature of fast radio bursts (FRBs), their cosmological origin, and their high occurrence, detection of strongly lensed sources due to intervening galaxy lenses is possible with forthcoming radio surveys. We…

High Energy Astrophysical Phenomena · Physics 2017-09-27 Liang Dai , Wenbin Lu

The following results of dissertation are submitted for defense: 1. Precise measurements of coordinates and proper motion of the pulsar PSR 0329+54 using the VLBI method. 2. Establishing of the reason for the discrepancy between the…

Instrumentation and Methods for Astrophysics · Physics 2024-01-25 Alexander Evgenievich Rodin

This paper considers the problem of accurate measurement of circular polarization in imaging spectral-line VLBI observations in the lambda=7 mm and lambda=3 mm wavelength bands. This capability is especially valuable for the full…

Instrumentation and Methods for Astrophysics · Physics 2015-05-28 A. J. Kemball , L. Richter

The VLBI technique can image compact radio sources with resolutions of the order of the milliarcsecond and can determine astrometrically relative positions with submilliarcsecond precisions. We determined the angular separations among the…

Astrophysics · Physics 2009-10-31 E. Ros , J. M. Marcaide , J. C. Guirado , M. A. Perez-Torres

The ionospheric path delay impacts single-band very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously at two…

Instrumentation and Methods for Astrophysics · Physics 2023-04-12 Leonid Petrov

The high angular resolution and sensitivity of Very Long Baseline Interferometry (VLBI) offer a unique tool to identify and study active galactic nuclei and star-formation activity over cosmic time. However, despite recent technical…

Astrophysics of Galaxies · Physics 2024-12-05 Célestin Herbé-George , J. P. Mckean , Raffaella Morganti , Jack F. Radcliffe

Very Long Baseline Interferometry (VLBI) combines the signals of telescopes distributed across thousands of kilometres to provide some of the highest angular resolution images of astrophysical phenomena. Due to computational expense,…

Instrumentation and Methods for Astrophysics · Physics 2025-04-30 Jack F. Radcliffe , J. P. McKean , C. Herbé-George , L. Coetzer , T. Matsepane

We investigate circular polarization in pulsar radio emission through simultaneous observations of PSR B1133+16 at two frequencies. In particular, we investigate the association of the handedness of circular polarization with the orthogonal…

Astrophysics · Physics 2009-11-07 A. Karastergiou , S. Johnston , M. Kramer

We present a novel two-stage approach which combines unsupervised and supervised machine learning to automatically identify and classify single pulses in radio pulsar search data. In the first stage, we identify astrophysical pulse…

Instrumentation and Methods for Astrophysics · Physics 2018-08-07 Di Pang , Katerina Goseva-Popstojanova , Thomas Devine , Maura McLaughlin

We present here the results of the first part of the VLBI Ecliptic Plane Survey (VEPS) program. The goal of the program is to find all compact sources within $7.5^\circ$ of the ecliptic plane which are suitable as calibrators for…

Instrumentation and Methods for Astrophysics · Physics 2017-06-12 Fengchun Shu , Leonid Petrov , Wu Jiang , Bo Xia , Tianyu Jiang , Yuzhu Cui , Kazuhiro Takefuji , Jamie McCallum , Jim Lovell , Sang-oh Yi , Longfei Hao , Wenjun Yang , Hua Zhang , Zhong Chen , Jinling Li

Fast radio bursts (FRBs) are extremely bright, millisecond duration cosmic transients of unknown origin. The growing number of wide-field and high-time-resolution radio surveys, particularly with next-generation facilities such as the SKA…

While conventional imaging in VLBI provides information only about the relative position between different features of a given source, phase-referenced observations can provide precise positional information with respect to an external…

Astrophysics · Physics 2007-05-23 Eduardo Ros

Radio source localization can benefit many fields, including wireless communications, radar, radio astronomy, wireless sensor networks, positioning systems, and surveillance systems. However, accurately estimating the position of a radio…

Robotics · Computer Science 2023-12-07 Asanka Perera , Vu Phi Tran , Sreenatha Anavatti , Kathryn Kasmarik , Matthew Garratt

Global VLBI observations at 5 GHz have been performed to study the source morphology in 10 compact steep-spectrum (CSS) sources selected from the Peacock & Wall catalogue with the aim of finding asymmetric structures produced by the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 D. Dallacasa , M. Orienti , C. Fanti , R. Fanti , C. Stanghellini

We present the results of several multi-station Very Long Baseline Interferometry (VLBI) experiments conducted with the ESA spacecraft Venus Express as a target. To determine the true capabilities of VLBI tracking for future planetary…

Instrumentation and Methods for Astrophysics · Physics 2012-05-15 Dmitry A. Duev , Guifre Molera Calves , Sergei V. Pogrebenko , Leonid I. Gurvits , Giuseppe Cimo , Tatiana Bocanegra Bahamon

We present a study of single pulses from nine bright northern pulsars to investigate the behaviour of circular polarisation, V. The observations were conducted with the Effelsberg 100-m radio telescope at 1.41 GHz and 4.85 GHz and the…

Astrophysics · Physics 2009-11-10 A. Karastergiou , S. Johnston , D. Mitra , A. G. J. van Leeuwen , R. T. Edwards