TITLE: GCN CIRCULAR NUMBER: 40307 SUBJECT: GRB 250430A: NUTTelA-TAO Early Measurements DATE: 25/05/01 17:08:43 GMT FROM: Toktarkhan Komesh at Nazarbayev University toktarkhan.komesh@nu.edu.kz
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:
The 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).
We 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:
filter tc-t0(s) mag err exposure_time (s) ------------------------------------------------------------------------------- r' 59 18.44 0.13 54 g' 55 UL18.10 45 r’ 162 18.56 0.14 120 g’ 227 19.23 0.11 300 … … … …
tc-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 We welcome opportunities for collaboration and data-sharing.
---------------------------------- NU = Nazarbayev University, Astana, 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. 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.
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