TITLE: GCN CIRCULAR NUMBER: 20693 SUBJECT: LIGO/Virgo G274296: REM optical/NIR observations DATE: 17/02/18 13:27:08 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OAB), G. Greco (Urbino University/INFN Firenze), A. Rossi (INAF-IASF Bo), A. Melandri, D. Fugazza, S. Covino, (INAF-OAB), E. Palazzi (INAF-IAFS Bo), M. Branchesi (Urbino University/INFN Firenze), L. Amati (INAF-IASF Bo), L. A. Antonelli, (INAF-OAR), S. Ascenzi (INAF-OAR), M.T. Botticella (INAF-OAC), S. Campana (INAF-OAB), E. Cappellaro (INAF-OAPD), V. D'Elia (INAF-ASDC), F. Getman (INAF-OAC), A. Grado (INAF-OAC), L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), L. Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), S. Piranomonte (INAF-OAR), L. Pulone (INAF-OAR), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), L . Tomasella (INAF-OAPD), S. Yang (INAF-OAPD), E. Brocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm report: We carried out optical/NIR follow-up observations of the LIGO/Virgo GW trigger G274296 (LVC GCN Circ. 20689) with the 60-cm robotic telescope REM located at the La Silla Observatory (Chile). The observations were carried out on 2017 Feb 18 from 00:23:52 UT to 03:09:11 UT, simultaneously in the g, r, i, z and H bands. We observed nine nearby (< 20 Mpc) galaxies within the LIGO cWB probability map. The pointing sequence was generated using the GWsky script (https://github.com/ggreco77/GWsky) starting from the high probability region of the skymap and taking into account the airmass: RA(J2000) Dec(J2000) galaxy_name Distance (Mpc) 137.0445 5.9276 UGC04797 17.3 137.5837 7.0379 NGC2775 17.3 143.6863 6.4256 PGC027228 7.78 146.1825 9.6161 IC0559 7.68 148.9515 16.4139 UGC05332 16.1 151.7796 15.9838 UGC05453 12.43 137.1523 5.2914 PGC2807128 5.7 143.4337 9.7108 SDSSJ093344.10+094239.0 16.4 144.5559 7.7234 SDSSJ093813.40+074324.2 12.94 A preliminary analysis (also based on visual comparison with the available SDSS fields) reveals no obvious optical/NIR candidate counterpart in the above galaxies down to the following magnitudes: r > 20, H > 17 (AB, 3sigma UL). Further analysis is in progress.