TITLE:   GCN CIRCULAR
NUMBER:  19497
SUBJECT: GRB 160601A: Discovery Channel Telescope Limits
DATE:    16/06/03 17:32:35 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko and E. Troja (NASA/GSFC) report on behalf of a larger collaboration:

We imaged the location of the optical afterglow (Malesani et al., GCN 19485) of the short GRB 160601A (Kocevski et al., GCN 19478) with the Large Monolithic Imager on the 4.3-m Discovery Channel Telescope in Happy Jack, AZ.  We obtained a series of 180 s exposures in the r-band filter beginning at 5:00 UT on 2016 June 3 (~ 1.6 d after the Swift trigger).  We do not detect any significant emission at the location of the optical afterglow to a limiting magnitude of r > 25.0 (calculated with respect to nearby point sources from SDSS).  Compared to the most recent detection with Gemini (Cenko et al, GCN 19492), our limits imply a significant steepening of the afterglow decay, with a lower limit on the power-law index of alpha > 1.3 (compared to alpha ~ 0.6 at earlier times; Schulze et al. 19488).

We thank the observers (T. Farnham, M. Knight, and L. Feagan) and the DCT staff for their assistance with these observations.