X-ray and near-infrared observations of GX 339-4 in the low/hard state with Suzaku and IRSF

Megumi Shidatsu, Yoshihiro Ueda, Fumie Tazaki, Tatsuhito Yoshikawa, Takahiro Nagayama, Tetsuya Nagata, Nagisa Oi, Kazutaka Yamaoka, Hiromitsu Takahashi, Aya Kubota, Jean Cottam, Ronald Remillard, Hitoshi Negoro

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

X-ray and near-infrared (J -H-Ks) observations of the galactic black-hole binary GX 339-4 in the low/hard state were performed with Suzaku and IRSF in 2009 March. The spectrum in the 0.5-300 keV band is dominated by thermal Comptonization of multicolor disk photons, with a small contribution from a direct disk component, indicating that the inner disk is almost fully covered by hot corona with an electron temperature of ≅175 keV. The Comptonizing corona has at least two optical depths, τ ≅ 1, 0.4. Analysis of the iron-K line profile yields an inner-disk radius of (13.3+6.4 -6.0)Rg (Rg represents the gravitational radius GM=c2), with the best-fit inclination angle of ≅50°. This radius is consistent with that estimated from the continuum fit by assuming the conservation of photon numbers in Comptonization. Our results suggest that the standard disk of GX 339-4 is likely truncated before reaching the innermost stable circular orbit (for a non-rotating black hole) in the low/hard states at ∼1% of the Eddington luminosity. The one-day averaged near-infrared light curves are found to be correlated with hard X-ray flux with FKs ∝ F 0.45 X . The flatter near-infrared νFν spectrum than the radio one suggests that the optically thin synchrotron radiation from the compact jets dominates the near-infrared flux. Based on a simple analysis, we estimate the magnetic field and size of the jet base to be 5 × 104G and 6 × 108 cm, respectively. The synchrotron self Compton component is estimated to be approximately 0.4% of the total X-ray flux.

Original languageEnglish
Pages (from-to)S785-S801
JournalPublications of the Astronomical Society of Japan
Volume63
Issue numberSPEC. ISSUE 3
DOIs
Publication statusPublished - 2011 Nov 25

Keywords

  • Accretion, accretion disks
  • Black hole physics
  • Infrared: Stars
  • Stars: Individual (GX 339-4)
  • X-rays: Binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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