Bibcode
Armstrong, R. P.; Fender, R. P.; Nicolson, G. D.; Ratcliffe, S.; Linares, M.; Horrell, J.; Richter, L.; Schurch, M. P. E.; Coriat, M.; Woudt, P.; Jonas, J.; Booth, R.; Fanaroff, B.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 433, Issue 3, p.1951-1957
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8
2013
Citations
14
Refereed citations
8
Description
Circinus X-1 is a bright and highly variable X-ray binary which displays
strong and rapid evolution in all wavebands. Radio flaring, associated
with the production of a relativistic jet, occurs periodically on a
˜17-d time-scale. A longer term envelope modulates the peak radio
fluxes in flares, ranging from peaks in excess of a Jansky in the 1970s
to a historic low of milliJanskys during the years 1994-2006. Here, we
report first observations of this source with the MeerKAT (Karoo Array
Telescope) test array, KAT-7, part of the pathfinder development for the
African dish component of the Square Kilometre Array, demonstrating
successful scientific operation for variable and transient sources with
the test array. The KAT-7 observations at 1.9 GHz during the period 2011
December 13 to 2012 January 16 reveal in temporal detail the return to
the Jansky-level events observed in the 1970s. We compare these data to
contemporaneous single-dish measurements at 4.8 and 8.5 GHz with the
HartRAO 26-m telescope and X-ray monitoring from MAXI. We discuss
whether the overall modulation and recent dramatic brightening is likely
to be due to an increase in the power of the jet due to changes in
accretion rate or changing Doppler boosting associated with a varying
angle to the line of sight.
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Montserrat
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