TY  - JOUR
A1  - Bersier, David
A1  - Fruchter, Andrew S.
A1  - Strolger, Louis-Gregory
A1  - Gorosabel, Javier
A1  - Levan, Andrew
A1  - Burud, Ingunn
A1  - Rhoads, James E.
A1  - Becker, Andrew C.
A1  - Cassan, Andrew C.
A1  - Chornock, Ryan
A1  - Covino, Stefano
A1  - De Jong, Roelof S.
A1  - Dominis, Dijana
A1  - Filippenko, Alexei V.
A1  - Hjorth, Jens
A1  - Holmberg, Johan
A1  - Malesani, Daniele
A1  - Mobasher, Bahram
A1  - Olsen, Kurt A. G.
A1  - Stefanon, Mauro
A1  - Castro Cerón, José María C.
A1  - Fynbo, Johan P. U.
A1  - Holland, Stephen T.
A1  - Kouveliotou, Chryssa
A1  - Pedersen, Hans-Georg
A1  - Tanvir, Nieal R.
A1  - Woosley, S. E.
T1  - Evidence for a supernova associated with the X-ray flash 020903
N2  - We present ground-based and Hubble Space Telescope optical observations of the X-ray flash ( XRF) 020903, covering 300 days. The afterglow showed a very rapid rise in the first day, followed by a relatively slow decay in the next few days. There was a clear bump in the light curve after similar to 25 days, accompanied by a drastic change in the spectral energy distribution. The light curve and the spectral energy distribution are naturally interpreted as describing the emergence and subsequent decay of a supernova ( SN), similar to SN 1998bw. At peak luminosity, the SN is estimated to be 0.8 +/- 0.1 mag fainter than SN 1998bw. This argues in favor of the existence of a SN associated with this XRF. A spectrum obtained 35 days after the burst shows emission lines from the host galaxy. We use this spectrum to put an upper limit on the oxygen abundance of the host at [O/H] <= 0.6 dex. We also discuss a possible trend between the softness of several bursts and the early behavior of the optical afterglow, in the sense that XRFs and X-ray-rich gamma- ray bursts ( GRBs) seem to have a plateau phase or even a rising light curve. This can be naturally explained in models in which XRFs are similar to GRBs but are seen off the jet axis.
Y1  - 2006
UR  - http://iopscience.iop.org/0004-637X/
U6  - https://doi.org/10.1086/502640
SN  - 0004-637X
ER  -