K-band image of the infrared counterpart of HESS J1943+213 (25′′× 25′′). The image at the top left is centered on 2MASS J19435624+2118233, the prospective infrared counterpart of the VHE gamma-ray source. The next 3 panels show residuals after subtracting, at the top right, a point source, at the bottom row from left to right, an exponential surface brightness profile, and a surface brightness profile with Sérsic index 7. The package galfit was used to determine the best-fitting free parameters (magnitude and, for the extended profiles, half-light radius). Bright, neighboring stars were also subtracted to avoid confusion. The prominent residual after subtracting a point source clearly demonstrates that the infrared counterpart to HESS J1943+213 is extended (to be compared with the residual from the bright star directly below HESS J1943+213). Furthermore, a high-Sérsic index profile leaves a smaller residual than an exponential profile, indicating that the surface brightness profile of HESS J1943+213 follows that of a typical, massive elliptical galaxy more closely than that of a disk galaxy. The moderate residual for the high-Sérsic index model hints at the presence of a central point source, but imaging with higher resolution is needed to confirm this.