[vsnet-grb-info 28252] GRB 210702A: Swift/UVOT redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30355
SUBJECT: GRB 210702A: Swift/UVOT redshift
DATE:    21/07/02 23:27:24 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

N. P. M. Kuin (UCL-MSSL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT obtained a 49s grism spectrum of GRB 210702A
starting 282 s after the BAT trigger (Lien et al., GCN Circ. 30351).
The spectrum shows a clear break at 2011 Angstrom, and absorption features
attributable to Ly-alpha and Ly-beta suggesting
a redshift of z=1.1757+/-0.0093. An possible intervening system is present
at
z=1.050 based on a weaker line seen at 2492A.

The wavelength anchor/zeropoint in the uv grism is uncertain by typically
15A, which translates to an uncertainty as quoted in the redshift above.