Finding Extremely Compact Sources Using the ASKAP VAST Survey

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Citation of Original Publication

Bignall, Hayley E.; Jauncey, David L.; Lovell, James E. J.; Ojha, Roopesh; Reynolds, Cormac; Finding Extremely Compact Sources Using the ASKAP VAST Survey; IVS 2010 General Meeting Proceedings, p.325–329 (2010);


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VLBI observations of intraday variable (IDV) quasars found in the MASIV (Micro-Arcsecond Scintillation-Induced Variability) 5 GHz VLA Survey of 500 flat-spectrum sources in the northern sky have shown that these sources are extremely compact, often unresolved, on milliarcsecond scales, and more core-dominated than their non-IDV counterparts. VAST: an ASKAP Survey for Variables and Slow Transients, proposes to observe 10,000 square degrees of southern sky daily for 2 years in the VAST-Wide survey component. This is expected to reveal of order 30,000 compact sources brighter than 10 mJy showing refractive interstellar scintillation (the cause of centimeter-wavelength IDV) at the survey frequency of about 1.4 GHz. Many of these sources may be suitable astrometric calibrators for VLBI at higher frequencies.