TITLE: GCN CIRCULAR NUMBER: 24666 SUBJECT: LIGO/Virgo S190521r: CNEOST follow-up observations DATE: 19/05/27 05:24:28 GMT FROM: Dong Xu at NAOC/CAS Dong Xu, Zi-pei Zhu, Bang-Yao Yu, Chen-zhou Cui, Hui-juan Wang (NAOC), Bin Li, Hai-bin Zhao (PMO), Tian-meng Zhang, Xu Zhou (NAOC), Xue-feng Wu, Zhi-ping Jin, Tian-rui Sun, Hao Lu, Ge-tu Zhaori, Ren-quan Hong, Long-fei Hu (PMO), Xiao-feng Wang, Wen-xiong Li (THU), Li-fan Wang (PMO/TAMU), Jin-zhong Liu (XAO), Ji-rong Mao, Jin-ming Bai (YNAO), report on behalf of the CNEOST collaboration We performed the search for the optical counterpart of LIGO/Virgo S190521r (LVC, GCN 24632) with the Chinese Near Earth Object Survey Telescope (CNEOST) at Xuyi, Jiangsu, China. The 3 x 3 deg^2 imager scanned high probability regions of the LVC localization that are accessible to CNEOST. Following are statistics of the tiled observations: StartTime (UT): 2019-05-21T15:41:24.772 EndTime (UT): 2019-05-21T18:58:17.206 Skycover (Square Degree): 558.0 #id CentRA(D) CentDEC(D) LimiteMag3_sig 5_sig 10_sig Filter 1 256.829041 -6.872913 18.906 17.909 17.240 VR 2 263.413177 -1.295197 18.800 17.806 17.101 VR 3 266.871521 4.283368 18.938 17.940 17.189 VR 4 260.596588 1.530886 18.954 17.973 17.259 VR 5 254.027359 -6.888728 18.816 17.862 17.191 VR 6 255.475098 -12.495871 18.512 17.530 16.844 VR 7 258.430573 -4.105478 18.924 17.890 17.219 VR 8 263.388000 1.514573 18.899 17.867 17.125 VR 9 264.045441 4.303978 18.962 17.958 17.209 VR 10 257.776398 -1.294184 18.856 17.902 17.240 VR 11 253.024246 -9.658165 18.851 17.853 17.180 VR 12 255.829697 -9.686105 18.821 17.822 17.170 VR 13 260.619476 -1.281923 18.921 17.919 17.255 VR 14 266.239868 1.524753 18.916 17.893 17.176 VR 15 261.243134 4.316584 18.997 17.975 17.204 VR 16 255.604233 -4.063662 18.796 17.848 17.179 VR 17 252.588333 -12.481894 18.730 17.778 17.132 VR 18 270.061768 9.874986 19.504 18.502 17.592 VR 19 278.463013 12.668616 19.556 18.571 17.582 VR 20 277.198456 18.282120 19.539 18.579 17.618 VR 21 269.861023 12.686904 19.543 18.561 17.643 VR 22 268.135651 7.094193 19.438 18.450 17.563 VR 23 272.937866 9.901986 19.409 18.434 17.513 VR 24 278.957642 15.476604 19.641 18.638 17.682 VR 25 277.198456 18.282120 19.539 18.579 17.618 VR 26 269.861023 12.686904 19.543 18.561 17.643 VR 27 268.135651 7.094193 19.438 18.450 17.563 VR 28 272.937866 9.901986 19.409 18.434 17.513 VR 29 278.957642 15.476604 19.641 18.638 17.682 VR 30 276.081696 15.470144 19.592 18.620 17.690 VR 31 267.238159 9.903188 19.570 18.565 17.649 VR 32 283.112885 18.275036 19.572 18.647 17.462 VR 33 293.939850 23.857258 19.854 18.915 17.552 VR 34 295.872009 29.443975 19.790 18.872 16.935 VR 35 284.753967 23.871096 19.637 18.700 17.547 VR 36 285.074524 21.086744 19.661 18.703 17.557 VR 37 293.939850 23.857258 19.854 18.915 17.552 VR 38 295.872009 29.443975 19.790 18.872 16.935 VR 39 288.274506 26.684416 19.757 18.806 17.457 VR 40 282.108063 21.065495 19.696 18.709 17.592 VR 41 287.858276 23.898252 19.692 18.740 17.593 VR 42 294.522736 26.683321 19.925 19.008 17.375 VR 43 292.672424 29.453629 19.845 18.924 17.228 VR 44 284.753967 23.871096 19.637 18.700 17.547 VR 45 301.318268 32.231853 19.783 18.872 17.461 VR 46 311.219604 35.047432 19.731 18.844 17.486 VR 47 321.477234 35.044441 19.787 18.838 17.540 VR 48 321.120056 32.208073 19.759 18.821 17.537 VR 49 311.248566 32.256496 19.797 18.881 17.570 VR 50 299.083832 29.438494 19.977 19.067 17.377 VR 51 304.624878 32.250858 19.814 18.893 17.764 VR 52 314.688507 35.058681 19.851 18.874 17.503 VR 53 324.914825 35.024250 19.810 18.847 17.540 VR 54 317.852173 32.231461 19.811 18.805 17.484 VR 55 307.892761 32.248425 19.958 18.992 17.790 VR 56 299.083832 29.438494 19.977 19.067 17.377 VR 57 304.624878 32.250858 19.814 18.893 17.764 VR 58 314.688507 35.058681 19.851 18.874 17.503 VR 59 324.914825 35.024250 19.810 18.847 17.540 VR 60 317.852173 32.231461 19.811 18.805 17.484 VR 61 307.892761 32.248425 19.958 18.992 17.790 VR 62 299.083832 29.438494 19.977 19.067 17.377 VR Apart from our previously reported optical transient (OT), OPEM-19ki in GCN 24647, which was also observed by RATIR (GCN 24650) and ATLAS (GCN 24653), we discovered another OT as well. Both of them are finally found unrelated with LIGO/Virgo S190521r.