2010CBET.2202....1M

U. Munari and A. Siviero, Istituto Nazionale di Astrofisica, Astronomical Observatory of Padova; and S. Dallaporta and P. Valisa, "Asiago Novae and Symbiotic Stars" (ANS) collaboration, write that, in 1978, the symbiotic nova V1413 Aql (= AS 338) began a not-yet-concluded outburst, characterized by two broad maxima at V = 11 in 1982-1983 and in 1995-1996. Since then, V1413 Aql has been exponentially declining, reaching mean brightness levels of B = 14.6, V = 13.6, V-R_c = +0.91, and V-I_c = +2.17 in 2008 – still appreciably brighter than the quiescence level. In April last year, Munari et al. (CBET 1761) detected the beginning of a re-brightening. V1413 Aql was closely monitored during all of 2009 and measured at mean values B = 13.80, V = 12.79, V-R_c = +0.88, V-I_c = +1.90. At that time, they predicted that the 2009 event could mark the beginning of a long ascent to a third maximum that, extrapolating from the previous two peaks, could be reached at V = 11 in about one year. That is precisely what it seems to have now occurred. As soon as V1413 Aql re-emerged from seasonal conjunction with the sun, Munari et al. resumed observations and found it shining at B = 11.74, V = 10.90, V-R_c = +0.70, V-I_c = +1.39 (mean values for the nights 2010 Mar. 6-9). The three maxima so far observed during the symbiotic-nova outburst of V1413 Aql are regularly spaced by about 14 years. The previous two maxima were marked by spectacularly deep eclipses of the outbursting companion following the orbital period of 434.1 days derived by Munari (1992, A.Ap. 257, 163), and this will presumably occur also during the current third maximum. The center of the next eclipse will be on May 15, and it will offer a great opportunity to derive an accurate radius for the outbursting component. A flat bottom of the eclipse should occur, lasting for about 25 days. Following eclipse analysis by Siviero et al. (2007, Baltic Astronomy 16, 55), the ingress should soon begin (depending upon the inflated dimension of the outbursting component). The last measurement of Munari et al. on Mar. 13.15 UT (B = 11.837, V = 11.009, V-R_c = +0.728, V-I_c = +1.423) could actually mark the start of the ingress phase. Absolutely fluxed, low-resolution spectra of V1413 Aql were obtained on Mar. 13.16 UT with the Asiago 1.22-m telescope (range 325-753 nm; 0.23 nm/pixel) and the Varese 0.6-m telescope (range 380-840 nm; 0.21 nm/pixel). The blue spectrum of the outbursting component completely overwhelms the molecular absorption spectrum of the M 5 III companion over the whole optical range. The Balmer continuum is in emission, and the only significant absorption features are the interstellar Na I D1/D2 and Ca II K lines. Compared to 2009, the emission-line spectrum has become very rich and characterized by low-ionization and low-velocity conditions, with no P-Cyg profile visible, disappearance of [O III] lines, and emergence of a forest of Fe II lines. The strongest emission lines belong to the Balmer series, He I, and Fe II multiplets 27, 28, 37, 38, 42, 46, 48, 49, 55, 73, and 74. The H_beta flux is 4.0 x 10**(-12) erg cm**(-2) s**(-1), and the flux ratio (H_alpha):(Hbeta):(He I 587.6-nm):(Fe II 468.6-nm) is 6.41:1.00:0.18:0.14.