Title:	Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield array
Authors:	Loi, Shyeh Tjing Murphy, Tara Deshpande, A.A. Prabu, T. Udaya Shankar, N. Srivani, K.S. Subrahmanyan, Ravi +28 Co-authors
Keywords:	interferometers radio continuum
Issue Date:	Nov-2015
Publisher:	Oxford University Press for the RAS
Citation:	Monthly Notices of the Royal Astronomical Society , 2015, Vol. 453, p 2731-2746
Abstract:	Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10–20 arcsec) at 154 MHz are small enough that search radii of 1–2 arcmin should be sufficient for cross-matching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1–3 per cent for the various nights. For sources fainter than ∼1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz.
Description:	Open Access
URI:	http://hdl.handle.net/2289/6390
ISSN:	1365-2966 - (online) 0035-8711
Alternative Location:	http://adsabs.harvard.edu/abs/2015MNRAS.453.2731L http://arxiv.org/abs/1508.00965 http://dx.doi.org/ 10.1093/mnras/stv1808
Copyright:	2015 The authors & the Royal Astronomical Society.
Appears in Collections:	Research Papers (A&A)

Items in RRI Digital Repository are protected by copyright, with all rights reserved, unless otherwise indicated.