(KAIT). Their image subtraction against previous (2007, 2008) KAIT observations revealed no evidence of an optical transient, with limiting magnitudes of 19.5-20.0.

We obtained images with the CTIO 4-meter telescope using the ISPI infrared imager on Aug. 2-4, 2009 in the J and K bands (Fig. \[fig:ISPI\]). The total exposure times were 12 min and 8 min per night, giving theoretical magnitude limits of 19.5 and 18 in J and K respectively (with a signal to noise ratio of 10). The airmass was around 1.1 and the seeing was 1” the first night, increasing to 1.5” the last night. The images have been taken using a dithered pattern and an offset blank field has been observed to estimate the sky contribution to the emission. We used IRAF common packages and the PANIC package [@Martini04] to reduce the data, and then Sextractor/Scamp [@Bertin06] to calibrate the astrometry and photometry of the image, using the 2MASS catalog as a reference [@Skrutskie06]. Based on the detection of sources around NGC 6440 X-2, a source of magnitude K=17 and J=18.5 would have been detected.

![ \[fig:optical\] Optical images of NGC 6440, plotting an 0.8” (4$\sigma$) error circle for NGC 6440 X-2. Upper left, archival 