X-ray and γ-ray spectra and variability of the black hole candidate GX 339-4

Grzegorz Wardziński (Lead / Corresponding author), Andrzej A. Zdziarski, Marek Gierliński, J. Eric Grove, Keith Jahoda, W. Neil Johnson

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


We analyse five observations of the X-ray binary GX 339-4 by the soft γ-ray OSSE detector on board CGRO simultaneous with either Ginga or RXTE observations. The source was bright during four of them, with the luminosity of L ∼ 1037 erg s-1 and the spectrum typical for hard states of accreting black holes, and it was in an off state during the fifth one, with L ∼ 1035 erg s-1. Our broad-band spectral fits show the mean electron energy of electrons in the Comptonizing plasma decreasing with increasing luminosity within the hard (bright) state. For the observation with the best statistics at soft γ-rays, ∼1/4 of energy in the Comptonizing plasma is probably carried by non-thermal electrons. Then, considering the efficiency of Comptonized hybrid synchrotron emission allows us to obtain an upper limit on the strength of the magnetic field in the X-ray source. Furthermore, this synchrotron emission is capable of producing the optical spectrum observed in an optically-high state of GX 339-4. In the off state, the hard X-ray spectrum is consistent with being dominated by bremsstrahlung. The unusually strong Fe Kα line observed by the RXTE/PCA during that state is found not to be intrinsic to the source but to originate mostly in the Galactic diffuse emission.

Original languageEnglish
Pages (from-to)829-839
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - 11 Dec 2002


  • Accretion, accretion discs
  • Binaries: general
  • Gamma-rays: observations
  • Gamma-rays: theory
  • Stars: individual: GX 339-4
  • X-rays: stars

ASJC Scopus subject areas

  • Space and Planetary Science


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