TITLE:   GCN CIRCULAR
NUMBER:  27267
SUBJECT: GRB 200228B: RATIR Optical Observations
DATE:    20/02/28 21:07:26 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

Margarita Pereyra (UNAM), 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), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM),
Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and
Vicki Toy (UMD) report:

We observed the field of GRB 200228B (Laha et al., GCN Circ. 27254) with
the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on
the 1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional
on Sierra San Pedro M��rtir from 2020/02 28.48 to 2020/02 28.53 UTC (0.27 to
1.52 hours after the BAT trigger), obtaining a total of 0.62 hours exposure
in the r and i bands.

For a source within the Swift-XRT enhanced error circle (Evans et al., GCN
Circ. 27256), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain
the following upper limits (3-sigma):

  r > 21.48
  i > 21.40

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 Astron��mico Nacional in San Pedro
M��rtir.


-- 
*Dr. Margarita Pereyra *

*FFTF, Schlumberger Foundation Alumnae*
----------------------------------------------------------------------------------------------------------------

*Catedr��tico Conacyt*

*Instituto de Astronom��a de la UNAM,*

*Km. 107 Carretera Tijua**na-Ensenada, *

*Ensenada Baja California, M��xico. C.P. 22860*

Oficina: 405

Skype: margarita-pereyra