Showing papers by "Richard Dodson published in 2010"
Swinburne University of Technology1, University of California, Berkeley2, Australia Telescope National Facility3, Cornell University4, University of Sydney5, California Institute of Technology6, National Radio Astronomy Observatory7, University of Western Australia8, University of Southampton9, United States Naval Research Laboratory10, University of British Columbia11, University of Manchester12, Los Alamos National Laboratory13
TL;DR: In this paper, the authors present a purely commensal survey experiment for fast (<5 s) transient radio sources, which covers the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view.
Abstract: We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
107 citations
TL;DR: In this article, the authors present a purely commensal survey experiment for fast (<5s) transient radio sources, which covers the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view.
Abstract: We are developing a purely commensal survey experiment for fast (<5s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
95 citations
TL;DR: In this paper, the authors used the Very Long Baseline Array and the European VLBI Network to observe the 22.2 GHz water and 6.7 GHz methanol masers in IRAS 20126+4104 at a number of epochs.
Abstract: IRAS 20126+4104 is one of the best candidates for a high-mass (proto)star surrounded by an accretion disk. Such a fact may be used to set constraints on theories of high-mass star formation, but requires confirmation that the mass and luminosity of IRAS 20126+4104 are indeed typical of a B0.5 star, which in turn requires an accurate estimate of the distance. We used the Very Long Baseline Array and the European VLBI Network to observe the 22.2 GHz water and 6.7 GHz methanol masers in IRAS 20126+4104 at a number of epochs suitably distributed in time. The absolute positions of the maser features were established with respect to reference quasars, which allowed us to derive absolute proper motions. From the parallax of the water masers we obtain a distance of 1.64 \pm 0.05 kpc, which is very similar to the value adopted so far in the literature (1.7 kpc) and confirms that IRAS 20126+4104 is a high-mass (proto)star. From the methanol masers we derive the component in the plane of the sky of the systemic velocity of the disk+star system (-16 km/s in right-ascension and +7.6 km/s in declination). Accurate knowledge of the distance and systemic velocity allows us to improve on the model fit to the water maser jet presented in a previous study. Finally, we identify two groups of methanol maser features, one undergoing rotation in the disk and possibly distributed along a narrow ring centered on the star, the other characterised by relative proper motions indicating that the features are moving away from the disk, perpendicular to it. We speculate that the latter group might be tracing the disk material marginally entrained by the jet.
4 citations
08 Sep 2010
TL;DR: The Commensal Realtime ASKAP Fast Transient Survey (CRAFT) as discussed by the authors uses GPUs as a simple highly parallel compute-engine to monitor the full field of view with a 5σ sensitivity of ∼Jy for a millisecond event covering the astronomically significant range of DMs.
Abstract: The Commensal Realtime ASKAP Fast Transient Survey (CRAFT[5]) will search the ASKAP data stream for fast (< 5sec) transient events, associated with the most extreme conditions in the Universe. The CRAFT search will run in parallel with all normal observing on ASKAP, giving a tremendous advance in the transient parameter space which can be searched. ASKAP offers high sensitivity, high resolution, and continous observations of a significant portion of the sky. However, to search across the wide field of view and at the data rates which are being provided by ASKAP is extremely challenging. Nevertheless, as reported here, we are on track to achieve the goals as laid out in the Survey Science Proposal. Using GPUs as a simple highly parallel compute-engine we can monitor the full field of view with a 5σ sensitivity of ∼Jy for a millisecond event covering the astronomically significant range of DMs. After that trigger detection we can download the beamformer data-buffer and image the sky at full sensitivity and spatial resolution with an arbitary frequency and time resolution.
01 Dec 2010
TL;DR: In this paper, the authors discuss the application of a new VLBI astrometric method named "Source/Frequency Phase Referencing" to measurements of "core-shifts" in radio sources used for geodetic observations.
Abstract: We discuss the application of a new VLBI astrometric method named "Source/Frequency Phase Referencing" to measurements of "core-shifts" in radio sources used for geodetic observations. We detail the reasons that astrometrical observations of 'core-shifts' have become critical in the era of VLBI2010. We detail how this new method allows the problem to be addressed at the highest frequencies and outline its superior compensation of tropospheric errors.