4U 1957+11: a persistent low-mass X-ray binary and black hole candidate in the high state?

Rudy Adam Dirk Wijnands, JM Miller, M van der Klis

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18 Citations (Scopus)

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 languageEnglish
Pages (from-to)pp.60-70.
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume331
Issue number1
Publication statusPublished - 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

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