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GCN Circular 35287

GRB 231205B: NUTTelA-TAO / BSTI Early Optical Limits
2023-12-06T09:54:28Z (6 months ago)
Toktarkhan Komesh at Nazarbayev University <>
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T. Komesh (NU), B. Grossan (UCB, NU), Zh. Maksut (NU), Zh. Abdullayev (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) observed the field of GRB 231205B, 10 s after receipt 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 started observations at 16:45:33 UT on 2023-12-05, 94 s after the BAT trigger. Observations were made in clear conditions. No source consistent with the XRT (J.P. Osborne et al., GCN Circ. 35275) was detected. We report the following results:

start time  t-t0(s)  end time    UL g'   UL r'  ULi'   exposure_time (s)
16:45:33     94     16:46:29     19.9     19.5    18.3          52.5
16:46:43    164     16:49:13 	 20.3     19.9    19.0          150

start time is in UT. t-t0(s) gives the time since trigger, in seconds. UL i', 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 0.5 s for g' and r' (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), 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 for i'.  Calibration was done with the 3 bright Pan-STARRS catalog stars on our images.

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.
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