T. Komesh (NU), Zh. Maksut (NU), B. Grossan (UCB, NU), Zh. Abdullayev (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 230228A, observing in Sloan g', r' and i' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We obtained 10x300 s frames starting at UT 2023-02-28 14:03:02, 8.2 hours after the BAT trigger. Observations were made under clear conditions, beginning with the target at an altitude of 45 deg. No new or changing sources consistent with the XRT position (Evans 2023, GCN 33379) were detected. Note that these observations provide essentially full-time coverage, simultaneous in all three bands. We report the following results:
start time t-t0(h) end time UL g' UL r' ULi' exposure_time (s)
------------ ----- ----------- ------ ------ ----- ------
14:03:02 8.2 14:53:02 19.9 19.6 19.5 300
start time is in UT. t-t0(h) gives the time since trigger, in hours. UL gives the 5 sigma upper limit sensitivity in magnitudes for images with individual exposure times. The given upper limit values are derived from the average calibration with only 3 standard stars per frame, and no other analysis or corrections.
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
FAI = Fesenkov Astrophysical Institute, Kazakhstan
This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870504). 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.