Issue A&A Volume 447, Number 2, February IV 2006 Page(s) 525 - 532 Section Galactic structure, stellar clusters and populations DOI 10.1051/0004-6361:20053437

A&A 447, 525-532 (2006)
DOI: 10.1051/0004-6361:20053437

Low frequency radio monitoring of Cygnus X-1 and Cygnus X-3

M. Pandey¹, A. P. Rao², G. G. Pooley³, P. Durouchoux⁴, R. K. Manchanda⁵ and C. H. Ishwara-Chandra<sup>2

1</sup>  Dept. of Physics, Mumbai University, Mumbai 400 098, India
    e-mail: mamta@ncra.tifr.res.in
²  NCRA, TIFR, Post Bag 3, Ganeshkhind, Pune 411 007, India
³  Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK
⁴  CNRS FRE 2591/CEA Saclay, DSM/DAPNIA/SAP, 91191 Gif-sur-Yvette Cedex, France
⁵  Tata Institute of Fundamental Research, Mumbai 400005, India

(Received 16 May 2005 / Accepted 4 October 2005)

Abstract
We present the results of monitoring observations of the micro-quasars Cygnus X-1 and Cygnus X-3 at 0.61 and 1.28 GHz. The observations were performed with the Giant Meter-wave Radio Telescope between 2003 June and 2005 January. Variable, unresolved sources were found in both cases. Cyg X-1 was detected in about half of the observations, with a median flux density about 7 mJy at each frequency. The variations in Cyg X-1 may be due to refractive interstellar scintillation. Cyg X-3 was detected in each observation, and varied by a factor of 4. For this source, models of the scintillation suggest a very long timescale (the order of 40 yr at 1.28 GHz), therefore, we believe that the variations are intrinsic to the source.

Key words: binaries: general -- ISM: jets and outflows -- radio continuum: stars -- accretion, accretion disks -- radiation mechanisms: general

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