RICCI, ROBERTOROBERTORICCIEleonora TrojaBruni, GabrieleGabrieleBruniTatsuya MatsumotoPIRO, LUIGILUIGIPIROBrendan O'ConnorTsvi PiranNiloofar NavaieelavasaniAlessandra CorsiBruno GiacomazzoMark H. Wieringa2022-03-282022-03-2820210035-8711http://hdl.handle.net/20.500.12386/31983Neutron star mergers produce a substantial amount of fast-moving ejecta, expanding outwardly for years after the merger. The interaction of these ejecta with the surrounding medium may produce a weak isotropic radio remnant, detectable in relatively nearby events. We use late-time radio observations of short duration gamma-ray bursts (sGRBs) to constrain this model. Two samples of events were studied: four sGRBs that are possibly in the local (<200 Mpc) universe were selected to constrain the remnant non-thermal emission from the sub-relativistic ejecta, whereas 17 sGRBs at cosmological distances were used to constrain the presence of a proto-magnetar central engine, possibly re-energezing the merger ejecta. We consider the case of GRB~170817A/GW170817, and find that in this case the early radio emission may be quenched by the jet blast-wave. In all cases, for ejecta mass range of M_ej \lesssim 10^{-2} (5 * 10^{-2}) M_sun, we can rule out very energetic merger ejecta E_ej \gtrsim 5 * 10^{52}(10^{53}) erg, thus excluding the presence of a powerful magnetar as a merger remnant.STAMPAenArticle10.1093/mnras/staa32412-s2.0-85097488300http://arxiv.org/abs/2008.03659v2https://academic.oup.com/mnras/article/500/2/1708/5936666?login=trueFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation