TITLE: GCN CIRCULAR NUMBER: 29767 SUBJECT: GRB 210406A: A long GRB detected by INTEGRAL DATE: 21/04/06 17:58:19 GMT FROM: Sandro Mereghetti at IASF-Milano/INAF S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC, Versoix) and J.Borkowski (CAMK, Torun) report: a gamma ray burst lasting about 60 s has been detected by IBAS in the IBIS/ISGRI data at 17:11:22 UT of April 6, 2021. The refined coordinates (J2000) are: R.A.= 132.4589 deg DEC.= +76.5322 deg with an uncertainty of 1.5 arcmin (90% c.l.). Due to telemetry saturation, we can derive only lower limits on the fluence and peak flux (20-200 keV). These are >1.2e-6 erg/cm2 and >1.6 ph/cm2/s (1-s integration time), respectively. A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html