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 journalLetter


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 1 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

Cite this

Casella, P., Maccarone, T. J., O'Brien, K., Fender, R. P., Russell, D. M., van der Klis, M., Pe'er, A., Maitra, D., Altamirano, D., Belloni, T., Kanbach, G., Klein-Wolt, M., Mason, E., Soleri, P., Stefanescu, A., Wiersema, K., & Wijnands, R. (2010). Fast infrared variability from a relativistic jet in GX 339-4. Monthly Notices of the Royal Astronomical Society: Letters, 404(1), L21-L25.