GRB200925B

We observed the location of the SWIFT GRB 200925B (trigger number #997453) with 0,7 m NUTTelA-TAO telescope at Assy-Turgen observatory, Almaty, Kazakhstan. The telescope started observation of the field of GRB 200925B 45 s after GRB trigger time (2020-09-25 21:50:37 UT).

Additional analysis of aperture photometry gives the following for the very early light curve in 45 s co-adds, where a negative mag is 5 sigma upper limit:

tc-t0    g’      sigma  r’     sigma  i’     sigma

67.5    -17.65  0.000 -18.40  0.000  18.32  0.303

136.5   -18.17  0.000  18.50  0.127  17.60  0.088

181.5   -17.80  0.000 -18.52  0.000  18.22  0.245

226.5   -18.27  0.000  18.04  0.084  17.50  0.076

271.5   -18.24  0.000  18.07  0.086  17.54  0.077

316.5   -18.32  0.000  18.23  0.097  17.52  0.079

361.5   -18.37  0.000  18.33  0.107  17.71  0.084

406.5   -18.18  0.000  18.29  0.117  17.61  0.088

Note well these values are not color corrected.

Note that the uncertainties have not been proven for all conditions and ranges of brightness.

Further reduction – improving uncertainty estimates and doing color corrections, is ongoing.