Supernova 2011af = Psn J02255436+1023111

Report the Catalina Real-time Transient Survey's discovery of an apparent supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2011 UT R.A. (2000.0) Decl. Mag. Offset 2011af Jan. 11.09 2 25 54.36 +10 23 11.1 16.7 4" W, 1" N Further CSS magnitude estimates for 2011af: 2010 Dec. 10.21 UT, [19.0; 2011 Jan. 5.15, 16.5. This object was designated PSN J02255436+1023111 when posted at the Central Bureau's TOCP webpage by Drake, and based on the spectroscopy below is here designated SN 2011af. Kuiyun Huang and Yoichi Ohyama, Institute of Astronomy and Astrophysics, Academia Sinica; Chia-Jung Chuang, Yuji Urata, and Induk Lee, National Central University, Taiwan; and Eric Y. Hsiao, Lawrence Berkeley National Laboratory, report that the inspection of a CCD spectrum (range 400-900 nm), obtained on Jan. 29.5 UT with the 1.8-m Ritchey Cretien reflector and medium dispersion spectrometer at Bohyunsan Optical Astronomy Observatory, Korea, shows that SN 2011af is a type-IIn supernova. The spectrum consists of a flat continuum and prominent narrow emission lines of the Balmer series (H-alpha FWHM of about 1500 km/s), with the narrow peaks yielding a redshift of 0.064. The "superfit" program of Howell et al. (2005, Ap.J. 634, 1190) shows its spectrum to be an excellent match to that of SN 1988Z. SN 2011af is measured to have a magnitude r' about 17.2 on Feb. 7.46 UT with the 1-m telescope at the Lulin Observatory in Taiwan; this corresponds to an absolute magnitude of about -20, nearly a month past its initial discovery....