Anthony J. Beasley

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Multifrequency observations from the VLA, VLBA and OVRO Millimeter Array of a major radio outburst of Cygnus X-3 in 2001 September are presented, measuring the evolution of the spectrum of the source over three decades in frequency, over a period of six days. Following the peak of the flare, as the intensity declines the high-frequency spectrum at frequency(More)
A new technique has been developed to remove the ionosphere’s distorting effects from low frequency VLBI data. By fitting dispersive and non-dispersive components to the phases of multifrequency data, the ionosphere can be effectively removed from the data without the use of a priori calibration information. This technique, along with the new gating(More)
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ∼15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in(More)
We present multifrequency VLA and VLBA observations at 8.4 GHz of the RS CVn system AR Lac, that were performed in autumn 1997 simultaneously with X-ray observations obtained from Rodonò et al. (1999). Our VLBA data indicate a resolved source with dimension close to the system separation, while the study of the flux density curve evidences a small amplitude(More)
We present the first milli-arcsecond resolution radio images of a radio-quiet quasar, detecting a high brightness temperature core with data from the VLBA. On maps made with lower-frequency data from MERLIN and the VLA jets appear to emanate from the core in opposite directions, which correspond to radio-emission on arcsecond scales seen with the VLA at(More)
The OH 1667 MHz maser in the circumstellar shell around the Mira variable U Her has been observed with the NRAO Very Long Baseline Array (VLBA) at 6 epochs, spread over 4 years. Using phase referencing techniques the position of the most blue-shifted maser spot was monitored with respect to two extra-galactic radio sources. The absolute radio positions of(More)
As part of a wider search for radio emission from nearby systems known or suspected to contain extrasolar planets Eridani was observed by the Jansky Very Large Array (VLA) in the 2-4 GHz and 4-8 GHz frequency bands. In addition, as part of a separate survey of thermal emission from solarlike stars, Eri was observed in the 8-12 GHz and the 12-18 GHz bands of(More)
We present simulated images of Supernova 1993J at 8.4 GHz using Very Long Baseline Interferometry (VLBI) techniques. A spherically symmetric source model is convolved with realistic uv-plane distributions, together with standard imaging procedures, to assess the extent of instrumental effects on the recovered brightness distribution. In order to facilitate(More)