R. S. Wharton

R. S. Wharton
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R. S. Wharton
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High Energy Astrophysical Phenomena (12)
 
Cosmology and Nongalactic Astrophysics (3)
 
Instrumentation and Methods for Astrophysics (2)
 
General Relativity and Quantum Cosmology (1)
 
Astrophysics of Galaxies (1)

Publications Authored By R. S. Wharton

Plasma lenses in the host galaxies of fast radio bursts (FRBs) can strongly modulate FRB amplitudes for a wide range of distances, including the $\sim $ Gpc distance of the repeater FRB121102. To produce caustics, the lens' dispersion-measure depth (${\rm DM}_{\ell}$), scale size ($a$), and distance from the source ($d_{\rm sl}$) must satisfy ${\rm DM}_{\ell} d_{\rm sl} / a^2 \gtrsim 0.65~ {\rm pc^2 \ AU^{-2} \ cm^{-3}}$. Read More

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities orders of magnitude larger than any other kind of known short-duration radio transient. Thus far, all FRBs have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. Read More

2017Jan
Affiliations: 1JIVE, 2JIVE, 3ASTRON, 4JIVE, 5JIVE, 6Carleton College, 7ASTRON, 8Columbia U, 9ASIAA, 10NRAO Socorro, 11NRAO Socorro, 12JIVE, 13Cornell U, 14Cornell U, 15NRAO Socorro, 16U. of Manchester, 17NAIC Arecibo, 18McGill U, 19UC Berkeley, 20NASA JPL, 21U. of West Virginia Dept. of Physics and Astronomy, 22NRAO CV, 23NAIC Arecibo, 24DRAO, 25NAIC Arecibo, 26UC Berkeley, 27MPIfR, 28McGill U, 29Cornell U

The millisecond-duration radio flashes known as Fast Radio Bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (~ 100mas precision) of FRB121102 using the VLA has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. However, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. Read More

2017Jan
Affiliations: 1McGill U., 2ASTRON, 3Cornell U., 4ASIAA, 5UC Berkeley, 6Cornell U., 7ASTRON, 8Columbia U., 9NRAO, WVU, 10NRAO, 11NRAO, 12ASTRON, API, 13McGill U., 14JPL, 15ASTRON, 16JIVE, 17WVU, 18JIVE, 19NRAO, 20DRAO, 21Arecibo, 22MPIfR, 23JIVE, Leiden, 24Cornell U.

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability $p\lesssim3\times10^{-4}$) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended ($0.6^{\prime\prime}-0. Read More

The Galactic center has some of the highest stellar densities in the Galaxy and a range of interstellar scattering properties that may aid in the detection of new radio-selected transient events. Here we describe a search for radio transients in the Galactic center using over 200 hours of archival data from the Very Large Array (VLA) at 5 and 8.4 GHz. Read More

We report on the discovery and timing observations of 29 distant long-period pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, confirmation and timing observations of these pulsars over several years at Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation and radiation properties. We have used multi-frequency data to measure the interstellar scattering properties of some of these pulsars. Read More

We report the discovery of two long-term intermittent radio pulsars in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, extended observations of these pulsars over several years at Jodrell Bank Observatory have revealed the details of their rotation and radiation properties. PSRs J1910+0517 and J1929+1357 show long-term extreme bi-modal intermittency, switching between active (ON) and inactive (OFF) emission states and indicating the presence of a large, hitherto unrecognised, underlying population of such objects. Read More

We analyze plasma dispersion and scattering of fast radio bursts (FRBs) to identify the dominant locations of free electrons along their lines of sight and thus constrain the distances of the burst sources themselves. We establish the average $\tau$-DM relation for Galactic pulsars and use it as a benchmark for discussing FRB scattering. Though scattering times $\tau$ for FRBs are large in the majority of the 17 events we analyze, they are systematically smaller than those of Galactic pulsars that have similar dispersion measures (DMs). Read More

We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this source. Read More

Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Read More

The detection of radio pulsars within the central few parsecs of the Galaxy would provide a unique probe of the gravitational and magneto-ionic environments in the Galactic Center (GC) and, if close enough to Sgr A*, precise tests of general relativity in the strong-field regime. While it is difficult to find pulsars at radio wavelengths because of interstellar scattering, the payoff from detailed timing of pulsars in the GC warrants a concerted effort. To motivate pulsar surveys and help define search parameters for them, we constrain the pulsar number and spatial distribution using a wide range of multiwavelength measurements. Read More