SIMBAD references

J. Vinko, University of Texas; F. Yuan, University of Michigan; H. Marion, University of Texas and Texas A&M University; R. Quimby, California Institute of Technology; D. Chamarro, M. D. Sisson, and C. Akerlof, University of Michigan; and J. C. Wheeler and E. Chatzopoulos, University of Texas, on behalf of the ROTSE collaboration, report the discovery of two 1991T-like type-Ia supernovae. SN 2009fx, which was discovered in unfiltered CCD images taken on May 29.34 (at mag about 18.5) and June 1.32 UT (mag about 18.0) with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory, is located at R.A. = 16:53:11.28, Decl. = +23:57:54.9 (equinox 2000.0; uncertainty about 0".5), which is 0".4 north of the center of its apparent host galaxy, SDSS J165311.27+235754.4; according to the NASA/IPAC Extragalactic Database (NED), the apparent host galaxy has a spectroscopic redshift of z = 0.04766. A finding chart has been posted at the following website URL: http://www.rotse.net/rsvp/j165311.3+235755/j165311.3+235755.jpg. A spectrum (range 420-1020 nm), obtained on June 6.40 with the 9.2-m Hobby-Eberly Telescope (HET; + Marcario Low-Resolution Spectrograph) by S. Rostopchin, shows 2009fx to be a type-Ia supernova. The spectrum contains the Si II 635.5-nm line and also other S II/Mg II/Fe II features that are characteristic of type-Ia supernovae. SNID software (Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that the spectrum best matches the spectra of normal type-Ia supernovae between -6 and +2 days relative to maximum, at a redshift consistent with that of the presumed host; this age estimate is supported by the ROTSE-III lightcurve, which shows that 2009fx brightened before the spectroscopic observation and stayed roughly constant (at mag about 17.5) between June 5.3 and 8.3. However, the Si II 635.5-nm feature is weak compared to the majority of type-Ia supernovae, and the Si II 580.0-nm feature is not detected. The spectrum is noisy at longer wavelengths, but there is no evidence for the O I 770-nm feature, and the Ca II infrared triplet is weak or absent. This suggests that 2009fx belongs to the subclass of 1991T-like, shallow-silicon supernovae (Filippenko xxxx, Ann. Rev. A. Ap. 35, 309; Branch et al. 2006, PASP 118, 560), and it is slightly before or at maximum light. The expansion velocity, derived from the minimum of the Si II 635.5-nm line, and correcting for the host-galaxy redshift, is about 10000 km/s. SN 2009fy was discovered in unfiltered CCD images taken on June 1.04 with the 0.45-m ROTSE-IIId telescope at the TUBITAK National Observatory at Bakirlitepe, Turkey, and it was also observed by ROTSE-IIIb since May 24.43, although the transient-search pipeline software did not identify it due to a nearby saturated object. SN 2009fy is located at R.A. = 23:24:05.13, Decl. = +16:39:50.9 (equinox 2000.0, uncertainty about 0".5), which is 1".4 west and 7".7 north of the center of its apparent host galaxy, SDSS J232405.23+163943.1 (= 2MASXI J2324052+163943; z = 0.0408, according to NED). ROTSE-III photometry shows 2009fy at mag about 16.0 between May 24 and 28, and it decayed afterward. A finding chart has been posted at website URL http://www.rotse.net/rsvp/j232405.1+163951/j232405.1+163951.jpg. An HET/LRS spectrum obtained by S. C. Odewahn on June 8.44 shows 2009fy to be a type-Ia supernova about two weeks after maximum. According to SNID, the spectrum best resembles those of SN 1991T (16 days after maximum) and SN 1997br (+12 days). The Si II 635.5-nm line appears to be slightly blended with Na I D. There is no O I feature at 770 nm, and the Ca triplet is weak. The redshift measured by SNID is z = 0.042, which is consistent with the redshift of the host. The photospheric velocity, estimated from the minimum of the Si II 635.5-nm feature, and corrected for the host-galaxy redshift, is about 8700 km/s.