A. A. Vittone

Short-period Active Binaries – Retrospect and Prospects

The most important characteristics and multi-frequency behaviour of the active RS CVn binaries are reviewed. New long-term photometric and spectroscopic observations of several short-period active RS CVn binaries are presented. The results for RT And, XY UMa and preliminary analysis of SV Cam and ER Vul are given. New prospects for research in the field are outlined.

Multifrequency Study of the Very Slow Nova V723 Cas

Multifrequency behaviour of the very slow nova V723 Cas is reviewed. The long-term photometry of the object revealed the orbital period 0.693265 days of the binary, quasi-periodic oscillations in the envelope of the outbursted white dwarf and 182 days periodicity of activity due to the mass transfer bursts from the red to the white dwarf probably caused by a periastron passage of the third body. The photometry at the maximum of brightness was used to calculate the velocity v = 210 {r km s}^{-1} of ejection of an expanding supergiant photosphere -- main inner envelope of the nova. The emission line profiles in nebular stage show multiple peaks formed in an expanding equatorial ring and polar blobs of this envelope. The HeI line profile and radio observations suggest the existence of the outer envelope, shaped and accelerated by the spherical and polar winds, detected as absorption components of the HI and HeI P Cygni type line profiles. Radio observations allowed to determine ejected mass 2.5 x 10 -4 M o and confirmed the clumpy structure of the ejecta.

Multifrequency Monitoring of RU Lupi: Observational Results and a Model

A large campaign of multifrequency observations of the extreme T Tauri star RU Lupi was performed from 1983 to 1988.

Multicolour Photometry and Spectroscopy of the Slow Nova V475 Sct (Nova Scuti 2003)

The UBVRI photometry and 460–900 nm spectroscopy of a classical nova V475 Sct obtained after its outburst in August 2003 is discussed. The nova was classified as a Fe II slow nova with the t2,V = 48 d, t3,V = 53 d. The absolute magnitudes of the nova at maximum MVmax = −7.16±0.15, MBmax = −6.96±0.39, the color excess E(B−V) = 0.69±0.05 and the distance to the nova d = 4.8±0.9 kpc was determined. Observed 13.4-day periodicity of flares can be explained either by pulsation of the nova envelope or by the mass transfer bursts from the red to the white dwarf probably caused by a periastron passage of the third body. The rapid fade of the brightness, which started 57 days after the maximum, is related to a dust formation in the ejecta of the nova. The early optical spectra display the forest of low ionization emission lines, primarily Fe II and Balmer H, accompanied by two P Cygni absorptions, arising in the inner and outer envelope of the expanding nova shell ejected at brightness maximum and accelerated by continuous stellar wind. The spectrum taken in the nebular stage of the nova, which started in March 2004, shows very strong emission [O III] 495.9 nm and 500.7 nm lines, responsible for discrepancy of the B and V magnitudes determined from observations taken by different instruments. The nebular emission line profiles suggest a nonspherical ejection of the shell.

Is It Possible to Observe Radiation of Fuors Boundary Layer

We have estimated the optical depth of stellar wind of 3 FUORs (V1057 Cyg, FU Ori, Z CMa) in Balmer and Paschen continuum and conclude that it seems plausible that it exceeds unity. If so it is not possible in principle to observe optical and UV radiation from the innermost and the hottest regions of these objects, i.e. boundary layer of the accretion disk.

On the Source of Optical Variability and Outflow in Z CMa System

We discuss our new (Teodorani et al. 1997) and already published photometric and spectroscopic data regarding the binary system Z CMa and conclude that these data, in contrast to wide spread opinion, do not contradict the hypotesis that a FU Ori type secondary rather than the IR primary is the main source of the observed optical variations and outflow. In the frame of this hypothesis, we explain observed larger polarization in the emission lines than in the continuum as a result of Thomson scattering of line quanta inside the region of their formation.