Abstract
We report on several pointed Rossi X-ray Timing Explorer observations of the enigmatic low-mass X-ray binary (LMXB) 4U 1957+11 at different X-ray luminosities. The luminosity of the source varied by more than a factor of 4 on time-scales of months to years. The spectrum of the source tends to become harder when its luminosity increases. Only very weak (1-2 per cent rms amplitude, 0.001-10 Hz, 2-60 keV) rapid X-ray variability was observed during the observations. A comparison of the spectral and temporal. behaviour of 4U 1957+11 with other X-ray binary systems, in particular LMC X-3, indicates that 4U 1957+11 is likely to be a persistent LMXB harbouring a black hole and it is persistently in the black hole high state. If confirmed, it would be the only such system known.
| Original language | English |
|---|---|
| Pages (from-to) | pp.60-70. |
| Number of pages | 11 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 331 |
| Issue number | 1 |
| Publication status | Published - 21 Mar 2002 |
Keywords
- accretion, accretion discs
- binaries : close
- stars : individual : 4U 1957+11
- X-rays : stars
- LMC X-3
- SPECTRAL BEHAVIOR
- NEUTRON-STARS
- SPACED DATA