A Variable Infrared Counterpart to the Soft Gamma-Ray Repeater SGR 1806–20

We present K'-band (2.12 μm) imaging observations of the SGR 1806-20 field taken during its very active phase in mid-2004; these observations reveal brightening of sources within the Chandra X-ray error circle when compared with earlier images obtained in 2002. One source brightened by more than a factor of 2, and so we consider this to be the probable infrared counterpart to SGR 1806-20. The other two sources are located in close proximity to the probable counterpart and show marginal brightening, which may suggest that the high-energy photons emitted from the soft gamma-ray repeater (SGR) during its active phase have induced dust sublimation or brightening of the unresolved background around the SGR.

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