Spingola, C.C.SpingolaDallacasa, D.D.DallacasaOrienti, M.M.OrientiGIROLETTI, MARCELLOMARCELLOGIROLETTIMcKean, J. P.J. P.McKeanCheung, C. C.C. C.CheungHovatta, T.T.HovattaCiprini, S.S.CipriniD'AMMANDO, FILIPPOFILIPPOD'AMMANDOFalco, E.E.FalcoLarsson, S.S.LarssonMax-Moerbeck, W.W.Max-MoerbeckOjha, R.R.OjhaReadhead, A. C. S.A. C. S.ReadheadRichards, J. L.J. L.RichardsScargle, J.J.Scargle2020-04-272020-04-2720160035-8711http://hdl.handle.net/20.500.12386/24249We present results on multifrequency Very Long Baseline Array (VLBA) monitoring observations of the double-image gravitationally lensed blazar JVAS B0218+357. Multi-epoch observations started less than one month after the γ-ray flare detected in 2012 by the Large Area Telescope on board Fermi, and spanned a 2-month interval. The radio light curves did not reveal any significant flux density variability, suggesting that no clear correlation between the high-energy and low-energy emission is present. This behaviour was confirmed also by the long-term Owens Valley Radio Observatory monitoring data at 15 GHz. The milliarcsecond-scale resolution provided by the VLBA observations allowed us to resolve the two images of the lensed blazar, which have a core-jet structure. No significant morphological variation is found by the analysis of the multi-epoch data, suggesting that the region responsible for the γ-ray variability is located in the core of the active galactic nuclei, which is opaque up to the highest observing frequency of 22 GHz.STAMPAenArticle10.1093/mnras/stw1362-s2.0-84963527861000373580500086https://academic.oup.com/mnras/article/457/2/2263/9716622016MNRAS.457.2263SFIS/05 - ASTRONOMIA E ASTROFISICAScienze Fisiche Settori ERC (ERC) di riferimento::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation