A variable mid-infrared synchrotron break associated with the compact jet in GX 339-4

P. Gandhi, A. W. Blain, D. M. Russell, P. Casella, J. Malzac, S. Corbel, P. D'Avanzo, F. W. Lewis, S. Markoff, M. Cadolle Bel, P. Goldoni, S. Wachter, D. Khangulyan, A. Mainzer

Research output: Contribution to journalArticle

Abstract

Many X-ray binaries remain undetected in the mid-infrared, a regime where emission from their compact jets is likely to dominate. Here, we report the detection of the black hole binary GX 339-4 with the Wide-field Infrared Survey Explorer (WISE) during a very bright, hard accretion state in 2010. Combined with a rich contemporaneous multiwavelength data set, clear spectral curvature is found in the infrared, associated with the peak flux density expected from the compact jet. An optically thin slope of ∼-0.7 and a jet radiative power of >6 × 1035ergs-1 (d/8 kpc)2 are measured. A ∼24hr WISE light curve shows dramatic variations in mid-infrared spectral slope on timescales at least as short as the satellite orbital period ∼95 minutes. There is also significant change during one pair of observations spaced by only 11s. These variations imply that the spectral break associated with the transition from self-absorbed to optically thin jet synchrotron radiation must be varying across the full wavelength range of ∼3-22 μm that WISE is sensitive to, and more. Based on four-band simultaneous mid-infrared detections, the break is constrained to frequencies of ≈4.6+3.5 - 2.0 × 1013Hz in at least two epochs of observation, consistent with a magnetic field B ≈1.5(± 0.8) × 104 G assuming a single-zone synchrotron emission region. The observed variability implies that either B or the size of the acceleration zone above the jet base is being modulated by factors of 10 on relatively short timescales.

Original languageEnglish (US)
Article numberL13
JournalAstrophysical Journal Letters
Volume740
Issue number1
DOIs
StatePublished - Oct 10 2011

Keywords

  • X-rays: binaries
  • accretion, accretion disks
  • infrared: general
  • radiation mechanisms: non-thermal
  • stars: individual (GX339-4)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Gandhi, P., Blain, A. W., Russell, D. M., Casella, P., Malzac, J., Corbel, S., D'Avanzo, P., Lewis, F. W., Markoff, S., Cadolle Bel, M., Goldoni, P., Wachter, S., Khangulyan, D., & Mainzer, A. (2011). A variable mid-infrared synchrotron break associated with the compact jet in GX 339-4. Astrophysical Journal Letters, 740(1), [L13]. https://doi.org/10.1088/2041-8205/740/1/L13