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GCN Circular 1609

Subject
XRF 020903 spectrum
Date
2002-10-09T06:51:57Z (22 years ago)
From
Ryan Chornock at UC Berkeley <chornock@astro.berkeley.edu>
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.

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