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

Journal article

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. © 2010 The Authors. Journal compilation © 2010 RAS.

Authors: Casella, P; Maccarone, T; O'Brien, K; Fender, R; Russell, D

• Publication status: Published
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 404
• Issue: 1
• Pages: L21-L25
• Publication date: 2010-05-01
• DOI: 10.1111/j.1745-3933.2010.00826.x
• EISSN: 1745-3933
• ISSN: 0035-8711
• Language: English
• Keywords: X-rays: binaries; X-rays: individual: GX 339-4; black hole physics; stars: winds, outflows