A connection between the X-ray spectral branches and the radio brightness in GX17 + 2
Abstract
GX17 + 2 (4U 1813 - 14) is a bright X-ray binary1,2 in which matter is accreting on to a neutron star from a nearby companion. X-ray bursts, which are due to thermonuclear flashes on the surface of the neutron star3, are sometimes observed4-6, as well as quasiperiodic oscillations in the X-ray flux. The frequencies of the quasiperiodic oscillations depend on the spectral state of the source7-13, which manifests itself as three distinct spectral 'branches' in an X-ray colour-colour diagram. GX17 + 2 is also a variable radio source14-20 there is no believable optical counterpart21-23. We report here on simultaneous X-ray and radio observations which showed a connection between the spectral branches and the radio brightness. The 6-cm and 20-cm flux density increased by factors of 30 +/- 5 and 40 +/- 10, respectively, as the X-ray state changed from the so-called 'flaring branch' to the 'horizontal branch'. We suspect that this X-ray/radio connection is common among bright low-mass X-ray binaries.
- Publication:
-
Nature
- Pub Date:
- November 1988
- DOI:
- 10.1038/336146a0
- Bibcode:
- 1988Natur.336..146P
- Keywords:
-
- Neutron Stars;
- Radio Sources (Astronomy);
- Stellar Mass Accretion;
- X Ray Binaries;
- Horizontal Branch Stars;
- Radiant Flux Density;
- Stellar Color;
- Stellar Oscillations;
- Very Large Array (Vla);
- Astrophysics