Linking jet emission and X-ray properties in the peculiar neutron star X-ray binary Circinus X-1 |
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| Authors: | Paolo Soleri Valeriu Tudose Rob Fender Michiel van der Klis Peter G Jonker |
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| Institution: | Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, the Netherlands;Astronomical Institute of the Romanian Academy, Cutitul de Argint 5, RO-040557 Bucharest, Romania;Research Center for Atomic Physics and Astrophysics, Atomistilor 405, RO-077125 Bucharest, Romania;Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands;School of Physics and Astronomy, University of Southampton, Hampshire SO17 1BJ;SRON, Netherlands Institute for Space Research, 3584 CA Utrecht, the Netherlands;Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA |
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| Abstract: | We present the results of simultaneous X-ray and radio observations of the peculiar Z-type neutron star X-ray binary Cir X-1, observed with the Rossi X-ray Timing Explorer satellite and the Australia Telescope Compact Array in 2000 October and 2002 December. We identify typical Z-source behaviour in the power density spectra as well as characteristic Z patterns drawn in an X-ray hardness–intensity diagram. Power spectra typical of bright atoll sources have also been identified at orbital phases after the periastron passage, while orbital phases before the periastron passage are characterized by power spectra that are typical neither of Z nor of atoll sources. We investigate the coupling between the X-ray and the radio properties, focusing on three orbital phases when an enhancement of the radio flux density has been detected, to test the link between the inflow (X-ray) and the outflow (radio jet) to/from the compact object. In two out of three cases, we associate the presence of the radio jet to a spectral transition in the X-rays, although the transition does not precede the radio flare, as detected in other Z sources. An analogous behaviour has recently been found in the black hole candidate GX 339-4. In the third case, the radio light curve shows a similar shape to the X-ray light curve. We discuss our results in the context of jet models, considering also black hole candidates. |
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| Keywords: | accretion accretion discs stars: individual: Cir X-1 stars: neutron ISM: jets and outflows X-rays: binaries |
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