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Rapid optical and X-ray timing observations of GX 339-4: flux correlations at the onset of a low/hard state
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Gandhi, P., Makishima, K., Durant, M., Fabian, A. C., 1948-, Dhillon, V. S., Marsh, T. R., Miller, J. M., Shahbaz, T. and Spruit, H. C.. (2008) Rapid optical and X-ray timing observations of GX 339-4: flux correlations at the onset of a low/hard state. Monthly Notices of the Royal Astronomical Society, Vol.390 (No.1). L29-L33. ISSN 0035-8711
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Official URL: http://dx.doi.org/10.1111/j.1745-3933.2008.00529.x
Abstract
We present the discovery of optical/X-ray flux correlations on rapid time-scales in the low/hard state of the Galactic black hole GX339-4. The source had recently emerged from outburst and was associated with a relatively faint counterpart with mag V approximate to 17. The optical [ Very Large Telescope (VLT)/ULTRACAM] and X-ray (Rossi X-ray Timing Explorer) data show a clear positive cross-correlation function (CCF) signal, with the optical peak lagging X-rays by similar to 150 ms, preceded by a shallow rise and followed by a steep decline along with broad anticorrelation dips. An examination of the light curves shows that the main CCF features are reproduced in superpositions of flares and dips. The CCF peak is narrow and the X-ray autocorrelation function (ACF) is broader than the optical ACF, arguing against reprocessing as the origin for the rapid optical emission. X-ray flaring is associated with spectral hardening, but no corresponding changes are detected around optical peaks and dips. The variability may be explained in the context of synchrotron emission with interaction between a jet and a corona. The complex CCF structure in GX 339-4 has similarities to that of another remarkable X-ray binary XTE J1118+480, in spite of showing a weaker maximum strength. Such simultaneous multiwavelength, rapid timing studies provide key constraints for modelling the inner regions of accreting stellar sources.
| Item Type: | Journal Article |
|---|---|
| Subjects: | Q Science > QB Astronomy |
| Divisions: | Faculty of Science > Physics |
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society |
| Publisher: | Wiley |
| ISSN: | 0035-8711 |
| Date: | 11 October 2008 |
| Volume: | Vol.390 |
| Number: | No.1 |
| Number of Pages: | 5 |
| Page Range: | L29-L33 |
| Identification Number: | 10.1111/j.1745-3933.2008.00529.x |
| Status: | Peer Reviewed |
| Publication Status: | Published |
| Access rights to Published version: | Restricted or Subscription Access |
| Funder: | STFC, JSPS, RIKEN, Spanish Ministry |
| Grant number: | PP/D002370/1, AYA2004 02646, AYA2007 66887 |
| URI: | http://wrap.warwick.ac.uk/id/eprint/29066 |
Data sourced from Thomson Reuters' Web of Knowledge
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