TITLE:   GCN CIRCULAR
NUMBER:  31711
SUBJECT: GRB 220306B: Tautenburg observations
DATE:    22/03/08 17:35:24 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

S. Klose, A. Nicuesa Guelbenzu, B. Stecklum, S. Melnikov, F. Ludwig (all 
TLS Tautenburg) report:

We observed the field of the Swift/Fermi GRB 220306B (Caputo et al., GCN 
31697; Wood et al., GCN 31782) with the Tautenburg 1.34m Schmidt telescope 
equipped with the TAUKAM 6kx6k CCD camera. Observations were performed on 
March 8, 2022, between 00:03 and 00:34 UT, about 30 hours after the burst.

Inside the enhanced XRT error circle (Evans et al., GCN 31700) we do not 
detect any source. Close to the error circle we detect two sources.

Source 1 lies at RA, DEC (J2000) = 00:21:33.42, +71:21:46.7 (+/- 0.5 
arcsec) and is located at the south-eastern border of the XRT error 
circle. For this source we measure the following AB magnitudes:

r = 21.33 +/- 0.16,
i = 20.67 +/- 0.10,
z = 20.28 +/- 0.16,

calibrated against the Pan-STARRS catalog.

This source was already detected and discussed by Belkin et al. (GCN 
31705). Our r-band data confirm that it is fading and that light from an 
underlying permanent object starts to dominate.

Source 2 lies at at RA, DEC (J2000) = 00:21:33.52, +71:21:51.9 and is 
located at the north-eastern border of the enhanced XRT error circle. For 
this source we measure r > 22.2 (3 sigma), i = 21.27 +/- 0.17, z = 20.83 
+/- 0.25. The nature of this source is uncertain; obviously it is 
unrelated to the GRB.