Augustin Skopal

Broad Hα wings from the optically thin stellar wind of the hot components in symbiotic binaries

Aims. To model broad H 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 Ly photons on atomic hydrogen. Methods. Prole-tting analysis. Comparison of the observed broad H wings and their luminosity with those predicted by the model. Results. Synthetic H proles t excellently the observed wings forj vj> 200 km s 1 in our sample of 10 symbiotic stars during the quiescent as well as active phases. The wing prole 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 prole. Some observational characteristics of the H -emission, its relationship with the emission measure of the symbiotic nebula and a steep radio spectrum at 1.4 n 15 GHz suggest the ionized stellar wind from the hot component to be the dominant source contributing to the H 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.

On the effect of emission lines on UBVR photometry

Abstract We investigate the effect on the U, B, V, RC and RJ magnitudes of the removal of emission lines from a spectrum. We determined Δm corrections from the ratio of fluxes with and without emission lines, transmitted from the object through a photometric filter. An exact and simplified approach for operative use was applied. The effect was demonstrated for classical symbiotic stars, symbiotic novae and the classical nova V1974 Cyg . It was found that about 20–30%, 30–40%, 10% and 26/20% of the observed flux in the U, B, V and RC/RJ filters, respectively, are radiated in the emission lines of the investigated classical symbiotic stars. The largest effect was found for symbiotic novae ( RR Tel and V1016 Cyg ) and the classical nova V1974 Cyg at 210 days (an average of 74%, 79%, 56% and 66/60%), because of their very strong emission line spectrum. In all cases, the line corrected flux points fit the theoretical continuum well. The difference between Δm corrections obtained by the accurate calculation and that given by our approximate formula is less than 10%. Deviations up to 30% can exist only in the U passband. Examples for practical applications are suggested.

Recent photometry of symbiotic stars

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)

What mimics the reflection effect in symbiotic binaries

We discuss the origin of a periodic wave-like variation as a function of the orbital phase observed in the light curves (LC) of symbiotic stars. It is shown that this type of variability cannot be ascribed to a reflection eect. For example, the observed amplitudes of the LCs are far larger than those calculated within a model of the reflection eect. Here, the nature of the orbitally related changes in the optical continuum is outlined within an ionization model of symbiotic binaries.

Transient Jets in the Symbiotic Prototype Z Andromedae

We present the development of collimated bipolar jets from the symbiotic prototype Z And that appeared and disappeared during its 2006 outburst. We monitored the outburst with optical high-resolution spectroscopy and multicolor UBVR C photometry. In 2006 July, Z And reached its historical maximum at U ~ 8.0. After ~1 mag decline in mid-August, it kept its brightness at a high level of U ~ 9 up to 2007 January. During this period, rapid photometric variations with ?m ~ 0.06 mag on the timescale of hours developed. Simultaneously, high-velocity satellite components appeared on both sides of the H? and H? emission line profiles. Their presence was transient, being detected to the end of 2006. They were launched asymmetrically with a red/blue velocity ratio of 1.2-1.3. From about mid-August onward they became symmetric at ~?1200 km s?1, reducing the velocity to ~?1100 km s?1 at their disappearance. The spectral properties of these satellite emissions indicated the ejection of bipolar jets collimated within an average opening angle of 61. If the jets were expelled at the escape velocity, then the mass of the accreting white dwarf is M WD ~ 0.64 M ?. We estimated the average outflow rate via jets to M ? yr?1, during their August-September maximum, which corresponds to the emitting mass in jets, M em jet ~ 6 ? 10?10(R jet/1 AU)3/2 M ?. During their lifetime, the jets released a total mass of M total jet 7.4 ? 10?7 M ?. Evolution in the rapid photometric variability and asymmetric ejection of jets around the optical maximum can be explained by a disruption of the inner parts of the disk caused by radiation-induced warping of the disk.

A photometric and spectroscopic study of the eclipsing symbiotic binary AX Persei

We analysed photometric and spectroscopic optical observations of the eclipsing symbiotic binary AX Persei. For the first time, we present and discuss its historical, 1887-1999, photographic/ B -band and visual light curve (LC). The red giant in AX Per losses mass via the wind at a rate of

Recent photometry of symbiotic stars: Recent photometry of symbiotic stars

\dot M = 7.4\pm 1.7 10^{-7} M_{\odot} \rm yr^{-1}

Wind mass transfer in S-type symbiotic binaries I. Focusing by the wind compression model

. The terminal velocity of the wind is

Wind mass transfer in S-type symbiotic binaries - II. Indication of wind focusing

v_{\infty} = 32 \pm 6 \rm km s^{-1}

The spectroscopic evolution of the symbiotic star AG Draconis I. The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008

. We estimated an effective radius of the Hii nebula during the post-outburst stage (to JD 2450000) to be of