TITLE:   GCN CIRCULAR
NUMBER:  20994
SUBJECT: GRB 170405A: LCO FTN observations
DATE:    17/04/06 13:02:36 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc 
(U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large 
collaboration report:

We observed Swift GRB 170405A (Troja et al. GCN 20984) on April 06, from 
10:23 to 11:01 UT (0.66 to 0.68 days since the GRB) with the 2-m LCO 
Faulkes Telescope North with the SDSS i and r filters. We do not detect 
the optical afterglow (Troja et al; Malesani et al. GCN 20988; Klotz et 
al. GCN 20989; de Ugarte Postigo et al. GCN 20990; Martin-Carrillo et 
al. GCN 20991; Mazaeva et al. GCN 20992) down to the following limits:

Mid Time      Exposure       Filter       Magnitude (AB)
(days)           (s)
-------------------------------------------------------
0.66           5x120          SDSS-R        > 21.6
0.68           4x120          SDSS-I        > 21.6
-------------------------------------------------------

as calibrated against nearby Pan-STARRS objects. The nearby Pan-STARRS 
object mentioned by Malesani et al. is clearly visible in our stacked 
frames.