This is an odd LBV (Luminous Blue Variable) in NGC 2403. According to the supernova website run by David Bishop the LBV was first discovered in December 2013. It was imaged in May 2014, November 2014, August 2015 and December 2015 having a brightness of 18 to 18.5 mag. My image is from March 2015 and shows the star at almost the same brightness compared to the images shown on the supernova website. In April 2016 another image showed up showing the LBV at 18 mag which is almost the same level as it has since the end of 2013. However, this was called a new outburst and given the designation AT2016ccd. I am not yet convinced that it is really a new outburst and not the ongoing outburst from December 2013.

By the way, this letter combination of the designation 2016ccd is somewhat funny since the images are indeed taken with cameras having ccd sensors.

The supernova website also offers images taken by the Nordic Optical Telescope (NOT) and Hubble Space Telescope (HST). A few matching stars are marked by black boxes and the LBV by a cyan circle. I enlarged my image 800x and marked the relevant stars in the same colours (bottom). I also labeled the stars with letters A to D. The LBV is clearly much brighter than the dim star (marked C) northwest of it. However, in the HST image the dim star C is much brighter than the LBV.