TITLE:   GCN CIRCULAR
NUMBER:  30390
SUBJECT: GRB 210704A: RATIR optical upper limits
DATE:    21/07/06 11:51:23 GMT
FROM:    Eleonora Troja at NASA/GSFC/UMD  <eleonora@umd.edu>

Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G.
Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC),
Josh Bloom (UCB), Antonino Cucchiara (UVI), Owen Littlejohns (ASU),
Enrico Ramirez-Ruiz (UCSC), Jesus González (UNAM), Carlos
Roman-Zuniga (UNAM), Harvey Moseley (GSFC), John Capone (UMD),
V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210704A (Berretta et al. GCN 30375,
Ursi et al. GCN 30372, Malacaria et al. GCN 30380) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m
Harold Johnson Telescope at the Observatorio Astronomico Nacional on
Sierra San Pedro Martir. The target was visible from 2021/07 6.17 to
2021/07 6.18 UTC (30.72 to 31.18 hours after the BAT trigger), and we
obtained a total of 0.37 hours exposure in the r and i bands.

No source is detected at the position of the candidate optical counterpart
(Kim et al. GCN 30384, D'Avanzo et al. GCN 30385). In comparison with the
SDSS DR9 catalog, we obtain the following upper limits (3-sigma):

  r > 22.4
  i > 22.1

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.

Further observations are planned.