[vsnet-grb-info 18006] GRB 160425A: SMARTS late-time observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19454
SUBJECT: GRB 160425A: SMARTS late-time observations
DATE:    16/05/24 18:35:05 GMT
FROM:    Bethany Cobb at GWU  <bcobb at gwu.edu>

B. E. Cobb (GWU), reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
additional optical/IR imaging of the error region of GRB 160425A
(GCN 19343, Krimm et al.) at 7.3, 18.4 and 26.4 days post-burst.
For each epoch, total summed exposure times amounted to 36 minutes in
I and 30 minutes in J.

The possible host of GRB 160425A (GCN 19350, Tanvir et al.,
GCN 19351, Balanutsa et al.) is observed in these images. This object
appears as two separate knots and, therefore, may be a merging pair
of galaxies (GCN 19350, Tanvir et al.). The object, with a magnitude
of I~20.1 (calibrated using USNO-B1.0 stars), exhibits no significant
changes in brightness between 7 and 26 days post-burst, though changes
in brightness of less than 0.05 magnitudes cannot be ruled out by the
data. In this type of host, at a redshift of z=0.555 (GCN 19350,
Tanvir et al.), a 1998bw-like supernova would be expected to increase
the brightness of the host by approximately 0.1 magnitudes, and can
therefore be excluded. If this unusual burst (GRB GCN 19343, Krimm
et al.) is actually a long-duration GRB, than any associated supernova
must be dimmer at peak than SN 1998bw.