SNe 1999dd and 1999de are AGN
ATel #586; Avishay Gal-Yam (Caltech)
on 19 Aug 2005; 21:23 UT
Credential Certification: Avishay Gal-Yam (avishay@astro.caltech.edu)
Subjects: Optical, AGN, Supernovae
I have obtained a spectrum of the host galaxy of SN 1999dd (Gal-Yam & Maoz 1999; IAUC # 7227 ) with the LRIS spectrograph mounted on the Keck I 10m telescope at WMKO, Hawaii, on UT August 1, 2005. Full reduction reveals the galaxy is a type I AGN at z=1.064, derived from broad Mg II 2800 and confirmed by narrow OII 3727. I therefore conclude the optical variability originally attributed to a SN is more likely to have been an AGN flare, and that SN 1999dd is likely not a SN at all. I have also observed the location of SN 1999de (Gal-Yam & Maoz, IAUC # 7227 ) using the same setup. The target acquisition image showed a source at the location of SN 1999de has re-emerged. I have obtained spectra of this source, as well as of the nearby galaxy originally assumed to have been the host of SN 1999de. I find that the variable source is another type I AGN at z=0.65, based on a broad Mg II 2800 line and confirmed by a narrow NeV 3346 line. The nearby galaxy is at z=0.384 based on narrow lines of OIII 5007, Hbeta 4861 and OII 3727. I therefore conclude that the source reported as SN 1999de is actually a variable AGN, projected near a lower redshift galaxy, and both objects are behind and unrelated to the cluster Abell 24 which lies in the foreground. I note that these observations now make the sample of SNe discovered by the Wise Observatory Optical Transients Survey (WOOTS; e.g., Gal-Yam et al. 2003, AJ, 125, 1087) complete in the sense that every object reported by WOOTS has either been spectroscopically confirmed or is not a SN.
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