[vsnet-grb-info 15496] GRB 140903A: Confirmation of Optical Fading from Discovery Channel Telescope

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16785
SUBJECT: GRB 140903A: Confirmation of Optical Fading from Discovery Channel Telescope
DATE:    14/09/06 05:06:52 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko at nasa.gov>

S. B. Cenko (NASA-GSFC), J. Capone, V. Toy (UMD), A. Cucchiara, E. Troja, A. Kutyrev (NASA-GSFC), S. Veilleux, and S. Gezari (UMD) report on behalf of a larger collaboration:

We obtained additional r'-band imaging of the candidate optical afterglow (Capone et al., GCN 16769) of the Swift short burst GRB 140903A (Cummings et al., GCN 16763) with the Discovery Channel Telescope, beginning at 2:55 UT on 6 September 2014 (2.5 d after the Swift trigger).  Performing digital image subtraction using our most recent epoch as a template, we detect significant fading in this source, confirming the results of Levan et al. (GCN 16784).  Assuming no afterglow contamination in our latest epoch, we measure an afterglow brightness of r' = 21.7 at the time of our first DCT images (~ 12 hr after the Swift trigger).  This suggests the early emission was heavily contaminated by the host galaxy, consistent with the results of Fruchter et al. (GCN 16776) and Xu et al. (16783).  A figure showing our subtraction image can be found at:

http://asd.gsfc.nasa.gov/Brad.Cenko/grb140903A_dct.pdf

The detection of optical variability, together with a coincident radio detection (Fong, GCN 16777), confirm the host association of z = 0.351 for GRB 140903A (Cucchiara et al., 16774).  We encourage additional follow-up (e.g., super/kilonova searches) to help clarify the nature of the progenitor system of this event.