[vsnet-grb-info 25089] GRB 200224A: RATIR Optical Observations and Confirmation of the Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27189
SUBJECT: GRB 200224A: RATIR Optical Observations and Confirmation of the Afterglow
DATE:    20/02/25 00:49:46 GMT
FROM:    Rosa Leticia Becerra Godinez at Inst. de Astronoma,UNAM  <rbecerra at astro.unam.mx>

Rosa L. Becerra (UNAM), Margarita Pereyra (UNAM), Alan M. Watson (UNAM),
 Nat Butler (ASU), 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), Jesús González (UNAM),
Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD),
V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 200224A (Palmer D., et al., GCN 27173) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on
Sierra San Pedro Mártir from 2020/02 24.36 to 2020/02 24.54 UTC (5.33
to 9.66 hours after the BAT trigger), obtaining a total of 3.44 hours
exposure in the r and i bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS
DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r > 23.88
  i > 23.84

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

Castro-Tirado et al. (GCN 27176)
and Stecklum et al. (GCN 27177) report an afterglow candidate at roughly
magnitude 22 at about 1 and 2 hours after the burst. Our observations show
subsequent fading of this source and confirm that it is the afterglow.

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.