Abstract. We describe a method of disentangling the composite, 0.12-5 µm continuum of symbiotic binaries. The observed SED is determined by the IUE/HST archival spectra and flux-points corresponding to the optical UBVRI and infrared JHKLM photometric measurements. The modeled SED is given by superposition of fluxes from the cool giant, hot stellar source and nebula including the effect of the Rayleigh scattering process and considering influence of the iron curtain absorptions. We applied this method to 21 S-type symbiotic stars during quiescence, activity and eclipses. We isolated four main components of radiation and determined their properties. (i) Stellar radiation from the giant corresponds to a unique luminosity classnormal giants. Characteristic luminosities are 1600 ± 200 and 290 ± 30 L for red and yellow giants, respectively in our sample of objects. (ii) Hot object radiation during quiescence consists of the nebular and stellar component. The former radiates at a mean electron temperature of 19 000 K and its amount of emission suggests a mass-loss rate from giants via the wind aṫ M W = a few × 10 −7 M yr −1 . Radiation of the latter conforms well with that of a black-body photosphere at a characteristic temperature of 105 000 K. The corresponding effective radii are a factor of ∼10 larger than those of white dwarfs, which thus precludes observing the accretor's surface. Extreme cases of AX Per and V443 Her, for which the hot star temperature from the fit is not capable of producing the nebular emission, signal a disk-like structure of the hot stellar source even during quiescence. (iii) Hot object radiation during activity consists of three components -the stellar and the low-and high-temperature nebular radiation. The stellar radiation satisfies that of a black-body photosphere at a low characteristic temperature of ∼22 000 K (we call it the 1st type of outbursts) or at a very high characteristic temperature of ≈165 000 K (2nd type of outbursts). All the active objects with a high orbital inclination show features of the 1st-type of outbursts (here Z And, AE Ara, CD − 43• 14304, TX CVn, BF Cyg, CH Cyg, CI Cyg, AR Pav, AX Per), while AG Dra represents the 2nd-type. The presence of a two-temperature type of UV spectrum and an enlargement of effective radii of the stellar source by a factor of ∼10 with respect to the quiescent values during the 1st-type of outburst suggest an expansion of an optically thick medium at the orbital plane in the form of a disk. The low-temperature nebula radiates at a mean electron temperature of 14 000 K and is subject to eclipses, while the high-temperature nebula, which is seen during eclipses as the only component, is characterized by T e > 30 000 K. Radiative and geometric properties of the main sources of radiation allowed us to reconstruct a basic structure of the hot object during the 1st-type of outburst. There is an edge-on disk around the accretor. Its outer flared rim represents a warm pseudophotosphere of the hot stellar source, whose radiation is Rayleigh atten...

We present new photometric observations of 15 symbiotic stars covering their last orbital cycle(s) from 2003.9 to 2007.2. We obtained our data by both classical photoelectric and CCD photometry. Main results are: EG And brightened by ∼0.3 mag in U from 2003. A ∼0.5 mag deep primary minimum developed in the U light curve (LC) at the end of 2006. ZAnd continues its recent activity that began during the 2000 autumn. A new small outburst started in summer of 2004 with a peak U magnitude of ∼ 9.2. During the spring of 2006 the star entered a massive outburst. It reached its historical maximum at U ∼ 8.0 in 2006 July. AEAra erupted in 2006 February with Δmvis ∼ 1.2 mag. BF Cyg entered a new active stage in 2006 August. A brightness maximum (U ∼ 9.4) was measured during 2006 September. CH Cyg persists in a quiescent phase. During 2006 June–December a ∼ 2 mag decline in all colours was measured. CI Cyg started a new active phase during 2006 May–June. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Aims. To model broad Hα wings observed in symbiotic binaries by an optically thin, bipolar stellar wind from their hot components as an alternative to that considering the Raman scattering of Lyβ photons on atomic hydrogen. Methods. Profile-fitting analysis. Comparison of the observed broad Hα wings and their luminosity with those predicted by the model. Results. Synthetic Hα profiles fit excellently the observed wings for |∆v| > ∼ 200 km s −1 in our sample of 10 symbiotic stars during the quiescent as well as active phases. The wing profile formed in the stellar wind can be approximated by a function f (∆v) ∝ ∆v −2 , which is of the same type as that arising from the Raman scattering. Therefore it is not possible to distinguish between these two processes only by modeling the line profile. Some observational characteristics of the Hα-emission, its relationship with the emission measure of the symbiotic nebula and a steep radio spectrum at 1.4-15 GHz suggest the ionized stellar wind from the hot component to be the dominant source contributing to the Hα wings during active phases. The model corresponding mass-loss rates from the hot components are of a few ×10 −8 M yr −1 and of a few × (10 −7 −10 −6 ) M yr −1 during quiescent and active phases, respectively.

Aims. We determine the temporal evolution of the luminosity (L WD ), radius (R WD ) and effective temperature (T eff ) of the white dwarf (WD) pseudophotosphere of V339 Del from its discovery to around day 40. Another main objective was studying the ionization structure of the ejecta. Methods. These aims were achieved by modelling the optical/near-IR spectral energy distribution (SED) using low-resolution spectroscopy (3500-9200 Å), UBVR C I C and JHKLM photometry. Important insights in the physical conditions of the ejecta were gained from an analysis of the evolution of the Hα and Raman-scattered 6825 Å O vi line using medium-resolution spectroscopy (R ∼ 10 000). Results. During the fireball stage (Aug. 14. 8-19.9, 2013), T eff was in the range of 6000-12 000 K, R WD was expanding non-uniformly in time from ∼66 to ∼300 (d/3 kpc) R , and L WD was super-Eddington, but not constant. Its maximum of ∼9 × 10 38 (d/3 kpc) 2 erg s −1 occurred around Aug. 16.0, at the maximum of T eff , half a day before the visual maximum. After the fireball stage, a large emission measure of 1.0−2.0×10 62 (d/3 kpc) 2 cm −3 constrained the lower limit of L WD to be well above the super-Eddington value. The mass of the ionized region was a few ×10 −4 M , and the mass-loss rate was decreasing from ∼5.7 (Aug. 22) to ∼0.71× 10 −4 M yr −1 (Sept. 20).The evolution of the Hα line and mainly the transient emergence of the Raman-scattered O vi 1032 Å line suggested a biconical ionization structure of the ejecta with a disk-like H i region persisting around the WD until its total ionization, around day 40. On Sept. 20 (day 35), the model SED indicated a dust emission component in the spectrum. The dust was located beyond the H i zone, where it was shielded from the hard, > ∼ 10 5 K, radiation of the burning WD at that time. Conclusions. Our extensive spectroscopic observations of the classical nova V339 Del allowed us to map its evolution from the very early phase after its explosion. It is evident that the nova was not evolving according to the current theoretical prediction. The unusual non-spherically symmetric ejecta of nova V339 Del and its extreme physical conditions and evolution during and after the fireball stage represent interesting new challenges for the theoretical modelling of the nova phenomenon.