TITLE: GCN CIRCULAR NUMBER: 30283 SUBJECT: GRB 210619B: SRG/ART-XC detection DATE: 21/06/21 06:37:17 GMT FROM: Sergey Molkov at Space Research Inst., Moscow V. Levin, S. Molkov, I. Mereminskiy, А. Lutovinov, A. Semena and E. Filippova (IKI RAN) report on behalf of SRG/ART-XC team: At 23:59:21 UT on 19/06/2021 the Mikhail Pavlinsky ART-XC telescope on board the Spektr-RG observatory detected a short peak in the 40-120 keV count rate. This peak is associated with the luminous GRB210619B registered simultaneously by other space-bourne missions (Swift/BAT (D'Avanzo et al. 2021, GCN 30261), GECAM (Zhao et al. 2021, GCN 30264), Fermi-LAT (Axelsson et al. 2021, GCN 30270), Konus-Wind (Svinkin et al. 2021, GCN 30276), Fermi/GBM (Poolakkil and Meegan 2021, GCN  30279)). The burst light curve is similar to what observed by other telescopes, with a prominent initial peak (that lasted for 6 s and having a typical fast rise exponential decay form) and several consecutive peaks, roughly coincident with ones detected by Konus-Wind. The angle between telescope axis and the burst was 45 degrees, which means that the burst emission had penetrated through the side shield of ART-XC detectors. This significantly complicates the spectral analysis, which will be presented elsewhere. The Mikhail Pavlisky ART-XC is an X-ray telescope working in the  hard X-ray band (above 4 keV) in the Langrangian point L2. It could observe brightest GRBs through its side/back shielding, providing an additional leverage for the  IPN-like triangulation of such events.