Fast infrared variability from a relativistic jet in GX 339-4

P. Casella, T. J. Maccarone, K. O'Brien, R. P. Fender, D. M. Russell, M. van der Klis, A. Pe'er, D. Maitra, D. Altamirano, T. Belloni, G. Kanbach, M. Klein-Wolt, E. Mason, P. Soleri, A. Stefanescu, K. Wiersema, R. Wijnands

Research output: Contribution to journalLetterpeer-review


We present the discovery of fast infrared/X-ray correlated variability in the black hole transient GX 339-4. The source was observed with subsecond time resolution simultaneously with Very Large Telescope/Infrared Spectrometer And Array Camera and Rossi X-ray Timing Explorer/Proportional Counter Array in 2008 August, during its persistent low-flux highly variable hard state. The data show a strong correlated variability, with the infrared emission lagging the X-ray emission by 100 ms. The short time delay and the nearly symmetric cross-correlation function, together with the measured brightness temperature of ~2.5 × 106 K, indicate that the bright and highly variable infrared emission most likely comes from a jet near the black hole. Under standard assumptions about jet physics, the measured time delay can provide us a lower limit of Γ > 2 for the Lorentz factor of the jet. This suggests that jets from stellar-mass black holes are at least mildly relativistic near their launching region. We discuss implications for future applications of this technique.

Original languageEnglish (US)
Pages (from-to)L21-L25
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - May 2010


  • Black hole physics
  • Stars: winds, outflows
  • X-rays: binaries
  • X-rays: individual: GX 339-4

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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