2007CBET.1006....1I

T. Iijima, Astronomical Observatory of Padova, Asiago, writes that the spectral evolution of V5558 Sgr has been monitored at Asiago Observatory (CBET 934). Since its discovery on April 14, (IAUC 8832), the luminosity of this object gradually increased (CBET 965, IAUC 8854), with its maximum luminosity on July 9, and then a rather rapid fading (http://ooruri.kusastro.kyoto-u.ac.jp/pipermail/vsnet-alert/2007-July/ 001030.html). The photometric evolution suggested that a drastic change in the spectral features occurred. Spectra (range 350-600 nm; resolution 1000) taken on July 6.97 UT showed narrow, weak emissions of H_beta and Fe II multiplets 42 and 49, accompanied by P-Cyg-type absorption components blueshifted by about 400 km/s with respect to the emission features. The higher numbers of the hydrogen Balmer series and the other metallic lines were seen as pure absorptions. Also, Na I D and Ca II H and K were seen as absorptions, and a weak trace of the Fraunhofer G band was detected. On the contrary, the spectra (range 350-800 nm) taken on July 14.99 with the same resolution showed broad (FWHM about 1000 km/s) emission lines of H I, He I, and Fe II multiplets 27, 28, 37, 38, 42, 46, 48, 49, 55, 74, etc. P-Cyg-type absorptions were seen only in Ca II H and K, of which blueshifts were about 670 km/s. These spectral features are similar to those of the extremely slow nova V723 Cas in the early decline stage (Iijima 2006, A.Ap. 451, 563). Visual magnitude estimates (cf. IAUC 8854): July 10.953 UT, 6.7 (A. P. Correia, Esposende, Portugal); 12.960, 7.5 (Correia); 13.881, 7.7 (K. Hornoch, Vohancice, Czech Republic); 13.954, 7.9 (Correia); 16.883, 8.2 (Hornoch); 16.957, 8.3 (Correia); 17.986, 8.4 (Correia); 17.965, 8.5 (J. Carvajal, Madrid, Spain).