BL Lac Identification for the Ultraluminous X-ray Source Observed in the   Direction of NGC 4698
  We report the identification of the optical and radio counterparts of the ultraluminous X-ray (ULX) source XMMU J124825.9+083020 (NGC4698-ULX1). The optical spectrum taken with the VLT yields a redshift of z=0.43, which implies that the ULX is not associated with the nearby galaxy NGC4698. The spectral energy distribution calculated from the available data indicates that the source is likely to be a BL Lac object. The possible synchrotron peak at X-ray energies suggests that this source may be a gamma-ray emitter. 
L. Foschini, L.C. Ho, N. Masetti, M. Cappi, M. Dadina, L. Bassani, G.   Malaguti, E. Palazzi, G. Di Cocco, P. Martini, S. Ra...