TITLE:   GCN CIRCULAR
NUMBER:  29310
SUBJECT: ZTF21aaeyldq: NOT optical observations
DATE:    21/01/17 13:37:47 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC, HUST), J. P. U. Fynbo (DAWN/NBI), D. A. Perley (LJMU), 
S.Y. Fu, D. Xu (NAOC) report on behalf of a larger collaboration:

We observed the field of ZTF21aaeyldq/AT2021any (Ho et al., GCN 29305) 
using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. We did photometry in the Sloan g-/r-/i- filters, and the source, 
presumably an orphan GRB afterglow (e.g., A. de Ugarte Postigo et al., 
GCN 29307), is clearly detected in each of our images.

Preliminary photometry of the source is as follows:

T_start(UT)         Tmid-T0(day) Exptime(s) Filter    Mag     MagErr
2021-01-17T02:18:24     0.812    5x300    sdss-g   22.28     0.05
2021-01-17T02:45:53     0.831    5x300    sdss-r    21.86     0.04
2021-01-17T03:13:26     0.850    5x300    sdss-i    21.65     0.03

T0 is 06:59:45.6 UT on 2021-01-16, first ZTF detection of ZTF21aaeyldq, 
and calibrated with nearby Pan-STARRS stars.