2003IAUC.8167....3P

F. Patat, European Southern Observatory; and A. Pastorello, INAF-Padova, on behalf of the European Supernova Collaboration, report that J. Aceituno obtained two spectra (ranges 400-500 and 600-700 nm; resolutions 0.17 and 0.2 nm, respectively) with the Calar Alto 3.5-m telescope (+ TWIN spectrograph) on July 16.87 UT of the object given the supernova designation 2003gm (cf. IAUC 8164). The spectra show a featureless continuum, on which three emission lines – identified as H_alpha, H_beta, and H_gamma from the Balmer series – are visible, each showing a narrow peak overimposed on a broader component; the expansion velocities, deduced from the H_alpha profile, are 300 km/s and 1400 km/s (FWHM), respectively. The line peaks are redshifted at 1420 km/s, a value very similar to the host-galaxy recession velocity (1382 km/s, via NED). Even though the overall characteristics are similar to those of a type-IIn supernova, the distance to NGC 5334 (19.2 Mpc, assuming H_o = 72 km/s/Mpc) and the observed luminosity (IAUC 8164) imply that the absolute magnitude is about -14.4 – i.e., quite low. This, together with the spectral appearance, seems to indicate that the object is not a real supernova, but rather an eta-Car-like event, similar to SN 1997bs (Van Dyk et al. 2000, 112, 1532).