Supernova 2015B in NGC 4782 = Psn J12543553-1234186

S. Leonini, Siena, Italy, reports the discovery by M. Conti, G. Guerrini, P. Rosi, L. M. Tinjaca Ramirez, and himself of an apparent supernova (mag about 15.0) on two unfiltered CCD images (limiting mag about 18.1) taken on Jan. 5.123 UT at the Montarrenti Observatory in the course of an automatic survey of the Italian Supernovae Search Project using a 0.53-m f/8.7 Ritchey-Chretien telescope (+ Apogee Alta U47 CCD camera). The new object is located at R.A. = 12h54m35s.53 +/- 0".2, Decl. = -12d34'18".6 +/- 0".2 (equinox 2000.0), which is 2" west and 10" south of the nucleus of NGC 4782. Nothing is visible at this position on Palomar Sky Survey infrared, red, and blue plates from 1995 Mar. 23, 1991 Feb. 12, and 1982 Apr, 19 (limiting mag 20.0). The discovery image has been posted at the following website URL: http://www.astrofilisenesi.it/public/Sne/Uploads/PSN_NGC4782.jpg. The variable was designated PSN J12543553-1234186 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2015B based on the spectroscopic confirmation reported below. Additional CCD magnitudes for 2015B: 2014 apr. 23, [19.0 (Leonini et al.); 2015 Jan. 7.05, 15.6 (M. Caimmi, Loreto, Italy; 0.24-m f/6.5 reflector; position end figures 35s.49, 18".5; reference stars from UCAC-4 catalogue; image posted at website URL http://www.oav.name/public/PSN_J12543553-1234186_20150107,05.jpg). L. Tomasella, S. Benetti, E. Cappellaro, N. Elias-Rosa, P. Ochner, A. Pastorello, G. Terreran, L. Tartaglia, and M. Turatto, Osservatorio Astronomico di Padova, INAF, report that an optical spectrogram (range 340-1000 nm; resolution 1.2 nm) of PSN J12543553-1234186 = SN 2015B, obtained on Jan. 11.12 UT with the Asiago 182-cm Copernico Telescope (+ AFOSC) under the Asiago Transient Classification Program (Tomasella et al. 2014, A.N. 335, 841), shows that this is a type-Ia supernova. Assuming a recessional velocity of 4628 km/s (de Vaucouleurs et al. 1999, RC3.9; via NED) for the host galaxy, NGC 4782, a good match is found with several type-Ia supernovae about one week after B-band maximum light. An expansion velocity of 10800 km/s is derived from the minimum of the Si II 635-nm line. Classification was done with GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) and SNID (Blondin and Tonry 2007, Ap.J. 666, 1024). The Asiago classification spectra are posted at website URL http://sngroup.oapd.inaf.it.