------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2329 2007 Apr 23 19.09UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- V5558 SAGITTARII = NOVA SAGITTARII 2007 Yukio Sakurai, Japan, reports on CBET 931 the discovery of a possible nova (mag 10.3) on two 20-s CCD exposures taken on 2007 Apr. 14.78UT with a Fuji FinePix S2 Pro Digital camera (+ Nikon 180-mm f/2.8 lens). The position is: RA 18h 10m 18.4s DEC -18 46'51" (2000) The object was not present on the discoverer's image of Apr. 9.8UT to a limit of magnitude 11.4. Nakano obtained his own unfiltered CCD frames of the new object (at mag 10.2) with a 0.25-m f/4.8 reflector, providing the position end figures RA 18.19s, DEC 50.9". Neither the USNO catalogue nor the Digitised Sky Survey indicates any precursor at the position of the new star. K. Haseda, Japan has located several prediscovery images of the new star with a Canon EOS-5D digital camera (+ 120-mm-f.l.f/3.5 lens), providing the following estimated magnitudes: 2007 Apr.7.78,[11.8; 12.792, 11.2; 13.793, 10.8; 14.777, 10.4. N. N. Samus, Institute of Astronomy, Russian Academy of Sciences, advises that this nova has been given the designation V5558 Sgr. T. Iijima, Astronomical Observatory of Padova, Asiago, reports on CBET 934 that medium-dispersion spectra taken on Apr. 20.12 and 20.14 UT at Asiago Astrophysical Observatory with a Boller-and-Chivens spectrograph mounted on the 1.22-m reflector show prominent narrow emission lines of H I and He I (e.g., equivalent width -3.4 nm and FWHM = 480 km/s for H_beta, and -0.50 nm and 360 km/s for He I 587.6-nm). Weak emissions of some Fe II lines of multiplets 37, 42, and 49 were seen, and Mg II, Si II, and probably N II were also noticed in emission. Most of the prominent emission lines were accompanied by a weak absorption component blueshifted by 400-500 km/s with respect to the line center of the emission body. This object could be a rather peculiar classical nova in the pre-maximum stage. H. Naito and K. Matsuda, Nishi-Harima Astronomical Observatory; and H. Yamaoka, Kyushu University, report that a low-resolution spectrum obtained on Apr.20.80 UT with the 2.0-m NAYUTA telescope (+ MALLS), showed a smooth continuum with emission lines of the Balmer series and P-Cyg profiles of He I 492.2-nm (+ Fe II 492.4-nm), 501.50nm (+ Fe II 492.4-nm), 504.8-nm,587.6-nm, 667.8-nm, and Fe II 516.9-nm. The expansion velocity, derived from the FWHM of the Balmer series (H_alpha, H_beta, H_gamma), is 500, 520, and 540 km/s, respectively. Notable Na I D absorption lines suggest that our view of the nova suffers some reddening. The overall feature of the spectrum does not resemble that of a classical nova, but with the amplitude (> 10 mag) of outburst and the absence of a pre-outburst counterpart in the infrared or x-ray regions, it could be a very remarkable object. Guy M Hurst