TITLE: GCN CIRCULAR NUMBER: 24139 SUBJECT: LIGO/Virgo S190408an: INTEGRAL follow-up observations DATE: 19/04/21 23:30:53 GMT FROM: Alexander Lutovinov at Space Research Inst.,IKI A. Lutovinov, S. Molkov (IKI, Russia) V. Savchenko, C. Ferrigno, E. Bozzo, T. Courvoisier (ISDC/UniGE, Switzerland) E. Kuulkers (ESTEC/ESA, The Netherlands) C. Sanchez (ESAC/ESA, Spain) S. Mereghetti (INAF IASF-Milano, Italy) D. Götz, Ph. Laurent, S. Schanne, B. Cordier (CEA, France) S.Antier, A. Coleiro, A. Goldwurm (APC, France) J. Rodi, A. Bazzano, L. Natalucci, F. Panessa, F. Onori, P. Ubertini (IAPS/INAF, Italy) J. Chenevez, S. Brandt (DTU, Denmark) R. Diehl, A. von Kienlin (MPE, Germany) A. Domingo, J. M. Mas-Hesse (CAB/CSIC-INTA, Spain) L. Hanlon, A. Martin-Carrillo, M.Doyle (UCD, Ireland) R. Sunyaev (IKI, Russia) J.-P. Roques, E. Jourdain, P. von Ballmoos (IRAP, France) report: The INTEGRAL observatory performed follow-up observations of the LIGO/Virgo compact binary merger candidate S190408an (GCN #24069) in the form of the fast TOO operational test. The observations were carried out from 2019-04-10 11:13:07 to 2019-04-10 17:10:47 in the staring and hexagonal dithering modes with a total observing time of approximately 18 ks. They were centred on the coordinates RA=350.2, Dec=-56.0 and covered ~42% of the LIGO/Virgo localization probability with the highest sensitivity. We do not detect any new sources in the complete IBIS/ISGRI (25-60 keV)  mosaicked image with the best sensitivity of 16.5 mCrab (1.6e-10 erg/cm2/s, 3-sigma upper level) in this energy range.