Paiano, S.S.PaianoFalomo, R.R.FalomoPadovani, P.P.PadovaniGiommi, PaoloPaoloGiommiGargiulo, A.A.GargiuloUslenghi, M.M.UslenghiRossi, A.A.RossiTreves, A.A.Treves2024-04-162024-04-162021https://hdl.handle.net/20.500.13025/6359The BL Lac object 4FGL J0955.1+3551 has been suggested as a possible source of ultra-energetic neutrinos detected by the IceCube observatory. The target was observed in 2020 January at the Large Binocular Telescope. Our spectroscopy (4100-8500 Å) yields a firm redshift z = 0.557 as deduced by the absorption lines of the host galaxy. The upper limit of the minimum equivalent width on emission lines is ∼0.3 Å. From the source image, we are able to resolve the host galaxy for which we measure an absolute magnitude M(R) = −22.9 and Re = 8 kpc, which are values which are typical of the host galaxies of BL Lacs. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Societyenjournal article10.1093/MNRASL/SLAA056https://academic.oup.com/mnrasl/article/495/1/L108/5820823