Simultaneous radio and X-ray observations of Galactic Centre low mass X-ray binaries

Abstract

We have performed simultaneous X-ray and radio observations of thirteen Galactic centre low-mass X-ray binaries in 1998 April using the Wide-Field Cameras onboard BeppoSAX and the Australia Telescope Compact Array, the latter simultaneously at 4.8 and 8.64 GHz. We detect two Z sources, GX 17+2 and GX 5-1, and the unusual `hybrid' source GX 13+1. Upper limits, which are significantly deeper than previous non-detections, are placed on the radio emission from two more Z sources and seven atoll sources. Hardness-Intensity diagrams constructed from the Wide-Field Camera data reveal GX 17+2 and GX 5-1 to have been on the lower part of the horizontal branch and/or the upper part of the normal branch, at the time of the observations, and the two non-detected Z sources, GX 340+0 and GX 349+2, to have been on the lower part of the normal branch. This is consistent with the previous empirically-determined relation between radio and X-ray emission from Z sources, in which radio emission is strongest on the Horizontal branch and weakest on the Flaring branch. For the first time we have information on the X-ray state of atoll sources, which are clearly radio-quiet relative to the Z sources, during periods of observed radio upper limits. We place limits on the linear polarisation from the three detected sources, and use accurate radio astrometry of GX 17+2 to confirm that it is probably not associated with the optical star NP Ser. Additionally we place strong upper limits on the radio emission from the X-ray binary 2S 0921-630, disagreeing with suggestions that it is a Z-source viewed edge-on.

Accepted for publication in MNRAS

References in corpus (6)

• Quenching of the radio jet during the X-ray high state of GX 339-4
• The radio luminosity of persistent X-ray binaries
• The very flat radio - millimetre spectrum of Cygnus X-1
• High resolution optical and infrared spectroscopic observations of Cir X-1
• The infrared counterpart of the Z source GX5-1
• Infrared Candidates for the Intense Galactic X-ray Source GX 17+2

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• Peculiar spectral and power spectral behaviour of the LMXB GX 13+1
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• A model for the Z-track phenomenon in GX 5-1 and observational evidence for the physical origins of the kHz QPO
• The X-ray Halo of GX5-1
• Super-Orbital Variability in Hard X-rays
• Simultaneous X-ray/optical observations of GX 9+9 (4U 1728-16)
• Discovery of the near-infrared counterpart to the luminous neutron-star low-mass X-ray binary GX 3+1
• A Multi-wavelength Study of the X-ray Sources in NGC 5018
• A Lack of Radio Emission from Neutron Star Low Mass X-ray Binaries
• Spectroscopic Identification of the Infrared Counterpart to GX5-1
• Anti-Correlated lags in a Neutron star Z source GX 5-1: AstroSat's View
• X-ray polarization of Z-type neutron star low-mass X-ray binaries -- I. Model-independent, time-resolved X-ray polarimetry
• On the origin of the near-infrared emission from the neutron-star low-mass X-ray binary GX 9+1