N. Morrell, G. Folatelli, and M. Stritzinger, on behalf of the Carnegie Supernova Project, report that a spectrogram (range 375-912 nm) of 2007on (cf. CBET 1121), obtained on Nov. 11.29 UT with the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory, shows this to be a type-Ia supernova a few days before maximum light. Adopting the NED recession velocity of 1947 km/s for the host galaxy (from Graham et al. 1998, A.Ap. Suppl. 133, 325), the 'superfit' spectrum-comparison code (Howell et al. 2005, Ap.J. 634, 1190) provides the best match to SN 2004gs at three days before maximum. The spectrum shows the characteristics of relatively fast-declining supernovae, similar to those of SN 1986G, with strong Si II 597.2-nm absorption relative to Si II 635.5-nm. A strong P-Cyg line identified as O I 777.3-nm is observed. Considering the recession velocity given above, the maximum absorption of the Si II 635.5-nm line indicates an expansion velocity of about 12000 km/s.
Central Bureau Electronic Telegrams
- Pub Date:
- November 2007