{
  "eventId": "GRB 250430A",
  "submitter": "Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh@nu.edu.kz>",
  "circularId": 40307,
  "format": "text/plain",
  "createdOn": 1746119323612,
  "subject": "GRB 250430A: NUTTelA-TAO  Early Measurements",
  "submittedHow": "web",
  "bibcode": "2025GCN.40307....1K",
  "body": "T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), B. Grossan (UCB, NU), D. Berdikhan (NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory:\n\nThe Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 250430A on receipt of an automated GCN / BAT position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).\n\nWe started observations at 17:31:53 UT on 2025-04-30, 32 s after the BAT trigger. Observations were made in clear conditions for the first ~1 hour, followed by cloudy weather. Note that these observations provide essentially full-time coverage, simultaneous in two bands. A new and changing source consistent with the XRT/EP position (T. M. Parsotan et al., GCN 40292; C. Y. Wang et al., GCN 40299) was detected. We report the results for the earliest co-added images, without color corrections or corrections for galactic reddening, as following:\n\nfilter \ttc-t0(s) \tmag \terr \t\texposure_time (s)\n-------------------------------------------------------------------------------     \nr' \t59 \t\t18.44 \t0.13 \t        54 \ng' \t55\t\tUL18.10\t\t\t45\nr’\t162\t\t18.56\t0.14\t\t120\ng’\t227\t\t19.23\t0.11\t\t300\n…\t…\t\t…\t\t…\t\t\n\ntc-t0 = image center time minus trigger time. Calibration was done with 4 bright Pan-STARRS catalog stars on our images. A light curve of the optical transient is presented in Figure 1:  https://ecl.nu.edu.kz/research/observations/gamma-ray-bursts/grb250430a \nWe welcome opportunities for collaboration and data-sharing.\n\n----------------------------------\nNU = Nazarbayev University, Astana, Kazakhstan\nUCB = University of California, Berkeley, USA\nFAI = Fesenkov Astrophysical Institute, Kazakhstan\n\nThis research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). 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.\n"
}