TITLE: GCN CIRCULAR NUMBER: 20714 SUBJECT: LIGO/Virgo G274296: Asiago 1.82m Optical Observations DATE: 17/02/21 15:22:15 GMT FROM: Enzo Brocato at INAF-OA Roma L. Tomasella, E. Cappellaro (INAF OAPd), G. Greco (Urbino University/INFN Firenze), A. Rossi, E. Palazzi (INAF-IASF Bo), M. Branchesi (Urbino University/INFN Firenze), L. Amati (INAF-IASF Bo), L. A. Antonelli, S. Ascenzi (INAF-OAR), M.T. Botticella (INAF-OAC), S. Campana, S. Covino, P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-ASDC), F. Getman, A. Grado, L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), A. Melandri (INAF-OAB), L. Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), S. Piranomonte, L. Pulone (INAF-OAR), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), S. Yang (INAF-OAPD), E. Brocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm (GRAWITA) report: We carried out optical follow-up observations of the LIGO/Virgo GW trigger G274296 (LVC GCN Circ. 20689) with the Copernico 1.82m telescope (INAF OAPd, Asiago-Ekar, Italy). The observations were carried out starting on 2017 Feb 17 from 20:56:11.7 UT, until 2017 Feb 18, 03:22:58.5 UT, using Sloan g-band. We observed several 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 (30%) of the skymap (with the exception of the first three follow-up observations in the field of NGC4096, after GCN 20688) and taking into account the airmass: p01 12:06:00.60 +47:28:39 NGC4096 (follow-up after GCN 20688) p02 12:06:00.59 +47:28:45 NGC4096 (follow-up after GCN 20688) p03 12:06:00.55 +47:39:59 Norther of NGC4096 (GCN 20688) p04 10:51:20.65 +32:46:00 NGC3413 p05 10:56:19.93 +31:16:10 2MASX J10562004+3116126 p06 10:12:53.15 +22:43:15 MCG+04-24-018 p07 10:32:17.28 +27:40:10 NGC3274 p08 11:52:55.65 +36:59:16 NGC3941 p09 11:51:45.69 +38:00:55 NGC3930 p10 10:11:08.79 +23:52:31 LEDA 1695322 p11 10:17:39.63 +22:48:33 2MASX J10173965+2248358 p12 10:11:16.68 +24:03:56 AGC 721972 p13 09:21:00.10 +11:03:39 LEDA 26453 p14 09:21:00.12 +11:03:39 LEDA 26453 p15 09:21:01.14 +11:03:39 LEDA 26453 p16 09:55:48.15 +16:24:48 UGC5332 p17 10:31:48.30 +25:18:26 SDSS J103149.00+251816.0 p18 11:58:29.99 +38:04:34 UGC6955 p19 10:10:33.29 +22:00:36 LEDA 139255 p20 10:27:13.83 +24:09:44 LEDA 1701087 p21 10:23:44.64 +27:06:44 LEDA 1798058 p22 10:31:56.20 +28:01:37 LEDA 1824266 p23 12:03:53.89 +38:54:11 LEDA 2139249 p24 09:14:58.10 +06:00:17 SDSS J091457.31+060016.7 p25 10:27:16.93 +28:30:42 SDSS J102716.85+283039.6 p26 10:24:14.30 +24:25:46 AGC 731449 p27 10:32:18.79 +27:39:57 SDSS J103217.21+274007.7 p28 10:35:11.18 +25:27:00 SDSS J103511.05+252704.0 p29 10:28:58.61 +25:17:07 AGC 731454 p30 10:20:00.21 +24:25:55 SDSS J102002.81+242615.0 p31 10:19:59.99 +24:47:32 SDSS J101959.88+244724.6 p32 09:58:17.18 +21:05:19 SDSS J095816.17+210520.4 p33 09:33:44.60 +09:42:35 SDSS J093344.10+094239.0 p34 09:21:15.41 +09:42:55 SDSS J092114.97+094352.2 p35 09:29:51.95 +11:55:41 SDSS J092951.83+115535.7 The upper limit of the measured g-band magnitudes is 20.5-21.0 (AB mag, 3sigma). Based on comparison with SDSS field templates we detected a SN candidate at RA=10:27:28.025, Dec=+24:12:45.85 with magnitude g = 19.31 +/- 0.05 mag (AB). The object is hosted in a faint field galaxy SDSS J102727.87+241249.9, with photometric redshift photoZ=0.074 (SDSS DR13). Assuming the above redshift, the absolute magnitude is around -18.3. Few other transients are likely faint variable stars, since they are already visible in the SDSS images.