TITLE:   GCN CIRCULAR
NUMBER:  33259
SUBJECT: GRB 230201B: TURBO Optical Upper Limits
DATE:    23/02/03 22:21:28 GMT
FROM:    Robert Strausbaugh at University of Minnesota  <rstrausb@umn.edu>

R. Strausbaugh (UMN), D. Warshofsky (UMN), P. L. Kelly (UMN) report on
behalf of a larger collaboration:

We observed the GRB 230201B (Fermi GBM Team, GCN 33247) field with the
Total-Coverage Ultrafast Response to Binary-Mergers Observatory (TURBO)
prototype telescope in St. Paul, Minnesota on February 2, from 02:58 to
03:14 UT (corresponding to 7.03 to 7.30 hours after GRB trigger) in SDSS g
and r-band filters.

We acquired a series of 10x90s exposures in each band.  We do not detect
any fading sources in the GBM error region in either band, consistent with
available optical upper limits (Lipunov et al., GCN 33249).

The following 3-sigma upper limits in AB magnitudes are calculated using
the Pan-STARRS catalog as reference:

g > 17.95

r > 17.84

These magnitudes are not corrected for foreground Galactic extinction.

The TURBO prototype in St. Paul consists of two co-mounted 11-inch
telescopes each with a 6.6 square degree field of view. TURBO will consist
of two arrays of 8 pairs of co-mounted 11-inch telescopes at two dark-sky
sites: Magdalena Ridge Observatory, New Mexico, USA and Skinakas
Observatory, Crete, Greece.