GCN Circular 3787

Derek B. Fox (Penn State) and S. Bradley Cenko (Caltech) report on
behalf of a larger collaboration:  

"The Robotic 60-inch Telescope at Palomar Observatory (P60) responded
automatically to Swift Trigger 150139, recording a series of images
beginning at 06:50:30 UT, approximately 6 minutes after the burst.

Visual inspection of these images does not reveal any new objects by
comparison to the second-generation DSS images (XDSS).  Times and
approximate limits (calibrated against USNO-B1.0 catalog photometry)
for new point sources within the BAT error circle are as follows:

    Band    Exp     Epoch       Limit
   ==========================================
      R     60s     06:51:00   R > 18.3 mag
      i     60s     06:53:22   I > 17.0 mag
      R     3x60s   06:58:18   R > 18.9 mag
   ==========================================

Observations will continue as long as the source is visible."