SIMBAD references

B2 0828+32 is one of the few radio galaxies with two double lobe radio structures of different ages and oriented at widely different angles, indicating that the direction of the radio jet has changed with time. Recent spectral index maps set an age for the particles in the old lobes of 70Myears which is therefore also the maximum age of the young lobes. This sets a constraint on the time scale of the phenomenon which caused the change of radio axis direction. We have obtained deep CCD images, in V and R, of the host galaxy of B2 0828+32 in a search for signatures of a recent merger event. We find that the galaxy shows a regular morphology with no signs of a recent major merger. It has no double core or companion brighter than M_V=-16.7, within 38kpc. This is in contrast with the best known radio galaxies of this type, 3C 315 and B2 0055+26, which both belong to a close pair of ellipticals. The luminosity profile follows the de Vaucouleurs r^1/4 profile with some discrepancy at radii less than ∼15arcsec which could be a weak sign of a merger ≲10⁸years ago. We consider the scenario where the radio source is powered by a rotating black hole and the radio axis is aligned along the spin axis of the black hole. We discuss the case where the change of the radio axis direction was caused by accretion by the black hole following a merger event. The direction of the radio axis is changed when the accreted material arrives at the black hole with an angular momentum axis very different from the spin axis of the black hole and is at least equal to the initial black hole mass. The minimum mass doubling time of a black hole corresponds to the Eddington accretion rate and is t ∼31Myears (independent of the mass). The maximum age of the young lobes, 70Myears, constrains the accretion rate to be of the order of the Eddington rate. The present luminosity of the radio galaxy is much below the Eddington luminosity of even a small 10⁶M_☉ black hole, suggesting that the fuel is now exhausted.