2000MNRAS.318..599B -
Mon. Not. R. Astron. Soc., 318, 599-605 (2000/October-3)
Simultaneous radio and X-ray observations of Galactic Centre low-mass X-ray binaries.
BERENDSEN S.G.H., FENDER R., KUULKERS E., HEISE J. and VAN DER KLIS M.
Abstract (from CDS):
We have performed simultaneous X-ray and radio observations of 13 Galactic Centre low-mass X-ray binaries in 1998 April using the Wide Field Cameras on board BeppoSAX and the Australia Telescope Compact Array, the latter simultaneously at 4.8 and 8.64GHz. 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 polarization 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.
Abstract Copyright:
2000, Royal Astronomical Society
Journal keyword(s):
polarization - astrometry - binaries: close - radio continuum: stars - X-rays: stars
CDS comments:
table 4: VLA J1751-253/B1748-253 = [GR92] 1748-253.
Simbad objects:
22
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