TITLE:   GCN CIRCULAR
NUMBER:  28338
SUBJECT: GRB 200829A: Swift/UVOT-XRT photometric redshift
DATE:    20/09/01 11:55:48 GMT
FROM:    Samantha Oates at MSSL  <samantha.oates@alumni.ucl.ac.uk>

S. R. Oates (U.Birmingham), N.P.M. Kuin (MSSL-UCL),
M. De Pasquale (Istanbul U.), S. Campana (INAF-OAB),
A. Tohuvavohu (U Toronto) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift
Observatory Team:

We have performed a joint spectral analysis of Swift UVOT and XRT
observations of GRB 200829A (Siegel et al., GCN Circ. 28307; Kuin et al.
GCN Circ. 28311, Goad et al., GCN Circ. 28313), based on the methodology
of Schady et al. (2010, MNRAS, 401, 2773). Using this method, we created
an SED at 900s after the BAT trigger consisting of 6 UVOT filters and
WT mode XRT data. The model with the best fit, broken power-law with a
Milky Way extinction curve for the host extinction, gives a photometric
redshift for GRB 200829A of 1.25 +\- 0.02 (1 sigma uncertainty;
chi^2/dof = 586/538).

This circular is an official product of the Swift team.