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arXiv · 0811.1494

A variable near-infrared counterpart to the neutron-star low-mass X-ray binary 4U 1705-440

Jeroen Homan·David L. Kaplan·Maureen van den Berg·Andrew J. Young
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Abstract

We report the discovery of a near-infrared (nIR) counterpart to the persistent neutron-star low-mass X-ray binary 4U 1705-440, at a location consistent with its recently determined Chandra X-ray position. The nIR source is highly variable, with K_s-band magnitudes varying between 15.2 and 17.3 and additional J- and H-band observations revealing color variations. A comparison with contemporaneous X-ray monitoring observations shows that the nIR brightness correlates well with X-ray flux and X-ray spectral state. We also find possible indications for a change in the slope of the nIR/X-ray flux relation between different X-ray states. We discuss and test various proposed mechanisms for the nIR emission from neutron-star low-mass X-ray binaries and conclude that the nIR emission in 4U 1705-440 is most likely dominated by X-ray heating of the outer accretion disk and the secondary star.

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Jeroen Homan, David L. Kaplan, Maureen van den Berg, Andrew J. Young. 2008-11-10. A variable near-infrared counterpart to the neutron-star low-mass X-ray binary 4U 1705-440. https://doi.org/10.1088/0004-637x%2F692%2F1%2F73

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