The double AGN in NGC 6240 revealed through 3-5 micron spectroscopy
  We present 3-5 micron spectroscopy of the interacting system NGC 6240, showing the presence of two active galactic nuclei. The brightest (southern) nucleus shows up with a starburst-like emission, with a prominent 3.3 micron emission feature. However, the presence of an AGN is revealed by the detection of a broad Br alpha emission line, with a width of ~1,800 km/s. The spectrum of the faintest (northern) nucleus shows typical AGN features, such as a steep continuum and broad absorption features in the M-band. We discuss the physical properties of the dusty absorbers/emitters, and show that in both nuclei the AGN is dominant in the 3-5 micron band, but its contribution to the total luminosity is small (a few percent of the starburst emission). 
G. Risaliti (1,2), E. Sani (3), R. Maiolino (1), A. Marconi (1), S.   Berta (4), V. Braito (5), R. Della Ceca (5), A. France...