The `off' state of GX339-4
Abstract
We report BeppoSAX and optical observations of the black hole candidate GX339-4 during its X-ray `off' state in 1999. The broad-band (0.8-50keV) X-ray emission can be fitted by a single power law with spectral index, α~1.6. The observed luminosity is 6.6x1033ergs-1 in the 0.5-10keV band, which is at the higher end of the flux distribution of black hole soft X-ray transients in quiescence, comparable to that seen in GS2023+338 and 4U1630-47. An optical observation just before the BeppoSAX observation shows the source to be very faint at these wavelengths as well (B=20.1,V=19.2). By comparing with previously reported `off' and low states (LS), we conclude that the `off' state is actually an extension of the LS, i.e. an LS at lower intensities. We propose that accretion models such as the advection-dominated accretion flows are able to explain the observed properties in such a state.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2000
- DOI:
- 10.1046/j.1365-8711.2000.03334.x
- arXiv:
- arXiv:astro-ph/0001158
- Bibcode:
- 2000MNRAS.312L..49K
- Keywords:
-
- ACCRETION;
- ACCRETION DISCS;
- BLACK HOLE PHYSICS;
- BINARIES: CLOSE;
- STARS: INDIVIDUAL: GX339-4;
- X-RAYS: STARS;
- Astrophysics
- E-Print:
- Accepted for publication in MNRAS