TITLE:   GCN CIRCULAR
NUMBER:  29769
SUBJECT: GRB 210406A: Konkoly Obs. optical upper limit
DATE:    21/04/07 00:42:09 GMT
FROM:    Jozsef Vinko at Konkoly Observator  <vinko@konkoly.hu>

J. Vinko (Konkoly/ELTE/U Szeged), R. Szakats, L. Kriskovics, A. Pal and K. Vida (Konkoly)
report on behalf of the "Transient Astrophysical Objects" project:

We observed the field of GRB 210406A (Mereghetti, GCN29767; Lipunov et al. GCN29766) with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory through SDSS r' and i' filters on 2021 Apr 06.86 UT
(MJD 59310.86, 3h 31.6m after the trigger). The total exposure time was 1800 s. The frames were tied
to PS1-photometry of local stellar sources. No optical counterpart for the GRB has been detected
above the 5-sigma upper limit of 21.9 AB-mag, which is consistent with other reports of non-detection
(Hu et al. GCN29768).