GCN Circular 1609
R. Chornock and A. V. Filippenko, University of California, Berkeley, report that an optical spectrum (range 300-940 nm) of the proposed optical transient (OT) associated with XRF 020903 (GCN 1554) was obtained with the Low Resolution Imaging Spectrometer on the Keck-I 10-m telescope on Oct. 8 UT. Our spectrum is similar to that obtained by Hamuy & Shectman (GCN 1554), revealing a rich set of narrow emission lines associated with the host galaxy. The host is clearly a low-metallicity, high-excitation starburst galaxy, with high [O III]/H-beta and low [N II]/H-alpha intensity ratios; [Ne III] is also visible. The shape of the underlying continuum suggests the presence of an older population of stars as well. While we cannot yet rule out a contribution from an optical supernova (rather than some other type of OT), at this time there is little if any direct spectroscopic evidence for supernova features. Specifically, the deficit at rest wavelengths below 4000A (mentioned in GCN 1554) is consistent with a population of old to intermediate-age stars. This message may be cited.