Oggetto: CBET 1251: 20080210 : BF CYGNI Da: IAUC mailing list Data: Sun, 10 Feb 2008 18:15:31 -0500 (EST) A: biblio@arcetri.astro.it Electronic Telegram No. 1251 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html BF CYGNI U. Munari and A. Siviero, Istituto Nazionale di Astrofisica, Padova Astronomical Observatory; and S. Dallaporta, P. Valisa, L. Buzzi, G. Dalla Via, A. Maitan, L. Baldinelli, S. Moretti, S. Tomaselli, C. Gualdoni, and G. Cherini, ANS ("Asiago Novae and Symbiotic stars") collaboration, write that BF Cyg is currently on a rapid rise to a new bright maximum, as indicated by the following magnitudes and colors: Feb. 8.18 UT, B = 11.146, B-V = +0.76, V-Ic = +1.52; Feb. 9.19, 11.086, +0.74, +1.51. This symbiotic nova erupted in 1894, peaking at B = 9.7 (Leibowitz and Formiggini 2006, MNRAS 366, 675), and its decline back to quiescence required a century to complete. In 2006, Munari et al. discovered that BF Cyg was entering a new outburst phase (cf. CBET 596), peaking at B = 10.28, U-B = -0.31, B-V = +0.47, V-I_c = +1.14, and R_c-I_c = +0.59 on 2006 Oct. 12. Since then, BF Cyg had been smoothly declining, reaching B = 12.00, B-V = +0.81, V-I_c = +1.79 by 2007 Dec. 13. The spectroscopic evolution following the 2006 outburst has been tediously slow and characterized by persisting low-ionization conditions. Spectra obtained on 2007 Dec. 29 were still characterized by a forest of Fe II emission lines accompanying Balmer and weak He I emission lines. Spectra for 2008 Feb. 10.18 surprisingly show only marginal changes, in spite of the intervening large photometric brightening; they are still dominated by the same Balmer, He I, and Fe II emission lines, with reduction of their equivalent widths by about 20 percent compared to the spectra of Dec. 2007. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2008 CBAT 2008 February 10 (CBET 1251) Daniel W. E. Green