e-VLBI observations of Circinus X-1: Monitoring of the quiescent and flaring radio emission on au scales

A. Moin, C. Reynolds, J. C.A. Miller-Jones, S. J. Tingay, C. J. Phillips, A. K. Tzioumis, G. D. Nicolson, R. P. Fender

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


A recent detection of the peculiar neutron star X-ray binary Circinus X-1 with electronic very long baseline interferometry (e-VLBI) prompted the suggestion that compact, non-variable radio emission persists through the entire 16.6-d orbit of the binary system. We present the results of a high angular resolution monitoring campaign conducted with the Australian Long Baseline Array in real-time e-VLBI mode. e-VLBI observations of Circinus X-1 were made on alternate days over a period of 20 d covering the full binary orbit. A compact radio source associated with Circinus X-1 was clearly detected at orbital phases following periastron passage, but no compact radio emission was detected at any other orbital phase, ruling out the presence of a persistent, compact emitting region at our sensitivity levels. The jet was not resolved at any epoch of our 1.4-GHz monitoring campaign, suggesting that the ultrarelativistic flow previously inferred to exist in this source is likely to be dark. We discuss these findings within the context of previous radio monitoring of Circinus X-1.

Original languageEnglish
Pages (from-to)3551-3556
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - Jul 2011
Externally publishedYes


  • Accretion, accretion discs
  • Stars: individual: Circinus X-1 stars: neutron
  • X-rays: binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'e-VLBI observations of Circinus X-1: Monitoring of the quiescent and flaring radio emission on au scales'. Together they form a unique fingerprint.

Cite this