TITLE: GCN CIRCULAR NUMBER: 32381 SUBJECT: GRB 220711B: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary) DATE: 22/07/13 06:42:29 GMT FROM: Toktarkhan Komesh at Nazarbayev University T. Komesh (NU), B. Grossan (UCB, NU), Z. Maksut (NU), M. Krugov (FAI), report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 220711B on receipt of an automated GCN / BAT position alert, observing in Sloan g', r' and i' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We received the alert at UT 2022-07-11 18:16:50, 22 seconds after  the BAT trigger time, and started observations at UT 18:17:02, 12 s after receipt, 34 s after the BAT trigger. Observations were made under partially cloudy conditions. No new or changing sources consistent with the XRT position (Beardmore 2022, GCN 32370) were detected. The observations fully cover the UVOT/XRT observation time interval and partly cover the prompt emission time (D'Ai 2022, GCN 32366). Note that these observations provide essentially full-time coverage, simultaneous in all three bands. We report the following results: start time t-t0(s) end time UL g' UL r' ULi' exposure_time (s) ------------ -------- ----------- ------ ------ ----- ------ 18:17:02 34 18:18:02 18.3 18.1 17.7 60 18:18:17 109 18:23:17 19.2 18.9 18.7 300 start time is in UT. t-t0(s) gives the time since trigger, in seconds. UL gives the 5 sigma upper limit sensitivity in magnitudes, for images co-added to the given exposure time. The first row in the table corresponds to co-adds of an initial short exposure image sequence of 0.3 s (these sub-second exposures are read-noise suppressed by our EMCCD cameras, with high gain electron multiplication active; other images are taken in conventional CCD operation mode) for g' and r', and 7.5 s for i'. The second row corresponds to co-adds from a continuing series of 3 s exposures for g' and r', and 15 s exposures for i'.  Calibration was done with 4 bright Pan-STARRS catalog stars on our images. We caution the reader that these are preliminary results, without color or other corrections. Please also note that times are approximate. ---------------------------------- NU = Nazarbayev University, Nur-Sultan, Kazakhstan UCB = University of California, Berkeley, USA HKUST = Hong Kong University of Science and Technology FAI = Fesenkov Astrophysical Institute, Kazakhstan The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.