V745 Scorpii

R. M. Wagner and R. Bertram, Ohio State University; S. Starrfield, Institute of Geophysics and Planetary Physics, Los Alamos National Laboratory; and S. Shore, Computer Sciences Corporation, report: "Optical spectra (range 430-500 nm, resolution 0.2 nm) of the recurrent nova V745 Sco were obtained on Aug. 1.2 UT with the Perkins 1.8-m telescope at the Lowell Observatory using the Ohio State CCD spectrograph. They show strong H beta in emission with a FWHM of about 1200 km/s. There is a shallow P-Cyg profile extending to about 6000 km/s. In addition, both the H beta and H gamma emission lines show multiple subcomponents on the red side of the profile indicating nonspherical ejection. In addition to the hydrogen lines, He I 447.1 nm and the C III/N III 464-nm complex are present in emission. He II 468.6 nm is not obvious and may be absent. Fe II lines are present in emission at 452.3, 454.1, 455.6 and 458.4 nm. These spectra resemble that of the recurrent nova T CrB obtained at maximum light on 1946 Feb. 9 (Morgan and Deutsch 1947, Ap.J. 106, 362). The major difference is the absence of He II 468.6 nm, which was only weakly present at maximum for T CrB but within a day or two became extremely strong. The spectral evolution of this V745 Sco could be extremely rapid; in 1937 the star took 12 days to decline 3 mag."