Luminosity dependence of the electron temperature in the bright hard state of the black hole candidate GX 339-4

作者：Miyakawa Takehiro^*; Yamaoka Kazutaka; Homan Jeroen; Saito Koji; Dotani Tadayasu; Yoshida Atsumasa; Inoue Hajime

来源：Publications of the Astronomical Society of Japan, 2008, 60(3): 637-651.

• accretion disks, black hole physics
• stars : individual (GX 339-4)
• X-rays : stars

We have analyzed 200 Rossi X-ray Timing Explorer observations of the black hole candidate GX 339-4, all from bright hard state periods between 1996 and 2005. The purpose of our study is to investigate the radiation mechanisms in the hard state of GX 339-4. The broadband 3-200keV spectra were successfully modeled by a simple analytic model, power-law with an exponential cut-off modified with a smeared edge. The obtained energy cut-off (E(cut)) was distributed over 50-200 keV, and the photon index over 1.4-1.7. We found a clear anti-correlation (E(cut) alpha L(-0.70 +/- 0.06)) between the X-ray luminosity (L) in 2-200 keV and E(cut), when L is larger than 7 x 10(37) erg s(-1) (assuming a distance of 8 kpc), while E(cut) is roughly constant at around 200 keV when L is smaller than 7 x 10(37) ergs(-1). This anti-correlation remained unchanged by adopting a more physical thermal Comptonization model, which resulted in an anti-correlation that can be expressed as kT(e) alpha L(-0.24 +/- 0.06). These anti-correlations can be quantitatively explained by a picture in which the energy-flow rate from protons to electrons balances with inverse Compton cooling.

• 出版日期2008