TITLE:   GCN CIRCULAR
NUMBER:  10032
SUBJECT: GRB 091003: Possible Supernova Component
DATE:    09/10/18 19:56:31 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <Stephen.T.Holland@nasa.gov>

S. T. Holland (CRESST/USRA/GSFC) reports:

     The excess light from the z = 0.8969 host galaxy candidate for
GRB 091003 (Cucchiara et al. 2009, GCNC 10031) correspond to a
rest-frame B-band absolute magnitude of approximately M_B = -20 mag.
This is approximately consistent with the peak rest-frame B-band
absolute magnitude of SN1998bw.  The Cucchiara et al. (2009, GCNC
10031) observation was taken on 2009 Oct 17, which corresponds to
approximately seven days after the burst in the rest frame, which is
approximately the expected time of maximum light for a SN Ib/c.
Therefore, we suggest that the excess light seen in this galaxy may be
due to a supernova component of GRB 091003.  The lack of an observed
optical afterglow at earlier times supports this interpretation.
Further spectroscopic observations are encouraged to test this
hypothesis.