TITLE:   GCN CIRCULAR
NUMBER:  14202
SUBJECT: GRB 130131B: CTIO 0.9-m optical upper-limits
DATE:    13/02/13 18:57:53 GMT
FROM:    Francisco Virgili at Liverpool John Moores U  <fjv@astro.livjm.ac.uk>

D. Calderón Espinoza, B. Indahl, L. Paredes Alvarez, C. Kaleida (CTIO), and F. J. Virgili (LJMU) report:

"As part of the REU/PIA student program at the Cerro Tololo Inter-American Observatory (CTIO) we observed
GRB 130131B (Siegel et al., GCN 14159) with the SMARTS 0.9-m telescope beginning 11.6 hrs after the Swift
trigger.  No optical counterpart is detected within the XRT error circle to the following conservative limits:

Midtime of exposure     Exposure time     Filter     Magnitude
--------------------------------------------------------------------------
      12.7 hr               7x450s            R        > 20.7
      12.8 hr               7x450s            V        > 20.3
--------------------------------------------------------------------------

Magnitudes are calibrated using nearby USNOB-1 (R-band) and NOMAD (V-band) stars."