B2 0954+25A: a typical Fermi blazar or a γ-ray loud Narrow Line Seyfert 1≟


E-mail: giorgio.calderone@mib.infn.it


B2 0954+25A, detected by the Fermi satellite, is a blazar with interesting observational properties: it has been observed to transit from a jet-dominated to a disc-dominated state; its radio spectrum appears flat at all observing frequencies (down to 74 MHz); optically, the Hβ line profile is asymmetric. The flatness of the radio spectrum suggests that the isotropic emission from radio lobes is very weak, despite the large size of its jet (≳500 kpc). Its broad-band spectral energy distribution is surprisingly similar to that of the prototypical γ-ray, radio-loud, type 1 narrow-line Seyfert (γ-NLS1) galaxy PMN J0948+0022. In this work, we revisit the mass estimates of B2 0954+25A considering only the symmetric component of the Hβ line and find (1–3) × 108 M. In light of our composite analysis, we propose to classify the source as a transition object between the classes of flat spectrum radio quasars and γ-NLS1 galaxies. A comparison with two members of each class (3C 273 and PMN J0948+0022) is discussed.