TITLE:   GCN CIRCULAR
NUMBER:  30188
SUBJECT: GRB 210610B: Photometry and phot-redshift from Legacy Survey, PanSTAR, and SDSS
DATE:    21/06/11 03:47:08 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

S.Y. Fu, Z.P. Zhu, D. Xu, X. Liu (NAOC) report on behalf of a larger 
collaboration:

We checked the archives of Legacy Survey (LS), PanSTAR, and SDSS for GRB 
210610B (Page et al., GCN 30170). From the LS, the GRB optical afterglow 
(e.g., Page et al., GCN 30170) is positionally located in a bright 
nucleus, which lies in the south-eastern part of an extended source in 
the direction of NorthWest-SouthEast.

The source has the multi-band photometric magnitudes g = 22.97, r = 
22.87, z = 22.57, and a redshift z_ph = 0.96 +/- 0.44 from LS, and also 
PSF magnitudes g = 24.32 +/- 0.5 , r = 23.09 +/- 0.12, i = 24.33 +/- 
0.47, z = 23.61 +/- 0.69 from PanSTAR. The source is marginally detected 
by SDSS, and we measure its magnitude r ~22.8. The r-band magnitudes 
from three surveys are basically consistent with each other, considering 
difference of photometric methods. The LS's z_ph = 0.96 +/- 0.44 is also 
consistent with the spectroscopic tentative redshift z=1.13 of the GRB 
optical afterglow from the NOT (Fynbo et al., GCN 30182).

We thus think the source is likely the host galaxy of the GRB.