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GCN Circular 31417

Subject
GRB 220107B: Nanshan/NEXT optical upper limits and host galaxy candidate
Date
2022-01-09T04:04:47Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
S.Q. Jiang, S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), 
X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 220107B detected by Fermi (Arimoto et al., 
GCN 31409; Veres & Meegan, GCN 31414) and AstroSat (Suresh et al., GCN 
31412), using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. We obtained 6x300 s frames in the Sloan r-band and 5x300 s frames 
in Sloan z-band, starting at 21:30:31 UT on 2022-01-08.

No optical source is detected in our stacked images at the Swift-XRT 
position (Gropp et al., GCN 31411). Preliminary photometric results are 
as follows:

Tmid-T0 (hr)  Filter   Upper Limit(5-sigma)
    26.97           r          >21.3
    27.44           z          >19.3

calibrated with the nearby PanSTARRS field.

In addition, from Legacy Survey there exists a faint source at the 
border of the Swift-XRT error circle at coordinates R.A. (J2000) = 
14:25:37.66 and Dec. (J2000) = +20:10:17.01, and magnitudes of g ~ 
24.62, r ~ 24.51, z ~ 23.32 as well as a photo_redshift = 1.13 +/- 0.23. 
The source is not present in SDSS and PanSTARR, and might be the host of 
the burst.
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