2007CBET.1183....1M

U. Munari and A. Siviero, Istituto Nazionale di Astrofisica, Padova Astronomical Observatory; and P. Valisa, A. Frigo, S. Dallaporta, G. Cherini, and G. Dalla Via "Asiago Novae and Symbiotic Stars" (ANS) collaboration, report that CCD photometry of this nova (cf. CBET 1181), calibrated on nearby Tycho-2-catalogue stars, yields the following magnitudes and colors: Dec. 27.70 UT, V = 7.593, B-V = +1.080; Dec. 27.75, V = 7.576, B-V = +1.101; Dec. 28.72, V = 7.700, B-V = +1.141. Absolutely fluxed spectra of the nova were obtained on Dec. 27.75 and 28.70 with the 1.22-m telescope of the University of Padova in Asiago and the 0.6-m telescope of the Schiaparelli Observatory in Varese over the ranges 622-976 nm at 0.16 nm/pixel, 330-800 nm at 0.23 nm/pixel, 622-685 nm at 0.032 nm/pixel, and 560-628 nm at 0.033 nm/pixel. The spectra on Dec. 27.75 were dominated by the fully developed absorption spectrum of the expanding, optically thick ejecta, with only H_alpha and O I 777.2-nm showing a weak emission component flanked by a deep, unstructured P-Cyg absorption. The higher Balmer series and Fe II lines reported in emission on CBET 1181 were gone. The absorption lines had a Gaussian shape with a FWHM (corrected for instrumental resolution) of 610 km/s and a velocity of -640 km/s with respect to H_alpha and O I emission components, which had a FWHM of 750 km/s. On Dec. 28.70, the spectrum changed remarkably, indicating that the decline from maximum has probably begun. Higher Balmer series lines have turned into emission, together with N II and Na I D. H_alpha increased the flux by five times with respect to the H_alpha on Dec. 27.75, and Fe II displayed a rich emission-line spectrum composed of multiplets 27, 28, 37, 38, 42, 46, 48, 49, 55, and 74. Overall, the absorption line spectrum typical of a nova at maximum brightness has decreased, and almost all of the absorptions still visible are now part of P-Cyg profiles. Strong diffuse interstellar bands and Na I interstellar lines suggest a large reddening, possibly with E(B-V) > 0.7.