Variation of fluxes of RR Tel emission lines measured in 2000 with respect to 1996

The aim of this work is to make available unpublished non-Fe+ emission line fluxes from optical spectra of the symbiotic nova RR Tel which were taken in 2000, and to compare them with fluxes of the same lines from spectra taken in 1996. After leaving out blends and misidentifications, as well as the unreliable far-red and violet lines, we present the log (F2000/F1996) flux ratios for identified non-Fe+ lines. Mean values of log (F2000/F1996) for different ionization potential ranges of the ions producing the lines are shown separately for the permitted and forbidden lines. All means show fading, which is larger in the lowest range of ionization potential. Provisional interpretations are suggested. We also measured the values of FWHM in 2000; the previously known decrease with time of FWHM of lines due to the same ion has continued.Comment: 16 pages, 5 figure

The effect of dust obscuration in RR Tel on optical and IR long-term photometry and Fe II emission lines

Infrared and optical photometric and spectroscopic observations of the symbiotic nova RR Tel are used to study the effects and properties of dust in symbiotic binaries containing a cool Mira component, as well as showing "obscuration events" of increased absorption, which are typical for such Miras. A set of photometric observations of the symbiotic nova RR Tel in different wavelength bands - visual from 1949 to 2002 and near-infrared (JHKL) from 1975 to 2002 - are presented. The variability due to the normal Mira pulsation was removed from the JHKL data, which were then compared with the AAVSO visual light curve. The changes of the Fe II emission line fluxes during the 1996-2000 obscuration episode were studied in the optical spectra taken with the Anglo-Australian telescope. We discuss the three periods during which the Mira component was heavily obscured by dust as observed in the different wavelength bands. A change in the correlations of J with other infrared magnitudes was observed with the colour becoming redder after JD2446000. Generally, J-K was comparable, while K-L was larger than typical values for single Miras. A distance estimate of 2.5 kpc, based on the IR data, is given. A larger flux decrease for the permitted than for the forbidden Fe II lines, during the obscuration episode studied, has been found. There is no evidence for other correlations with line properties, in particular with wavelength, which suggests obscuration due to separate optically thick clouds in the outer layers.Comment: 19 pages, 11 figures, 3 table

Modelling of dust around the symbiotic Mira RR Telescopii during obscuration epochs

Context. Symbiotic Miras represent a class of peculiar binaries whose nature is still not well understood. Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding the evolution of symbiotic binaries and the interaction between their components. We present a model of inner dust regions around the cool Mira component of the symbiotic nova RR Tel based on the near-IR terrestrial photometry and infrared ISO spectra. Aims. Our goal is to find a comprehensive and consistent model of the circumstellar inner dust regions around the Mira component that can explain the observed photometric and spectroscopic features in the near- and mid-infrared. Methods. Available JHKL photometric observations from South African Astronomical Observatory were collected and corrected for Mira pulsations as well as for interstellar reddening to follow temporal changes of the near-infrared colours. Spectral energy distributions (SEDs) from 1 to 13 μm during obscuration epoch were reconstructed with the simultaneously available ISO/SWS spectra and JHKL magnitudes. The dust properties were determined by modelling both the reconstructed SEDs and the near-IR colours using the DUSTY numerical code. This 1D code solves radiative transfer through the circumstellar dust by calculating the dust temperature profile assuming spherical symmetry. Results. The Mira pulsation period of 387 days was found and confirmed with two independent fitting methods. A long-term variation of  ~7000 days, which cannot be attributed to orbital motion, was obtained from the analysis of the near-IR magnitudes. Reconstructed infrared SEDs were modelled successfully by a single dust shell with dust distribution enhanced by radiatively driven stellar winds. Mira temperature, dust sublimation temperature, grain diameter, density distribution, and optical depth have been obtained. Our model shows a maximum dust grain diameter of 4 μm, which is larger than expected and can be explained by grain growth in conditions of increased mass loss during obscuration epochs. Obscurations in the near-IR can be understood as a result of change of the dust optical depth and of the mass loss rate of Mira component. Change of the dust temperature on the inner boundary of the dust shell with pulsation phase have been identified by SED modelling. Assuming a gas-to-dust ratio of 200, we found a variable mass loss rate between 2.3 and 9.0 × 10-6   M⊙/yr and estimated the distance to RR Tel to be 2.7 kpc. Our results suggest a relatively low influence of the hot component on circumstellar dust and strong shielding of dust from the UV flux

Circumstellar Dust in Symbiotic Novae

We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the near-IR photometry, ISO spectra and mid-IR interferometry. The dust properties were determined using the DUSTY code. A compact circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel shows the presence of an equatorially enhanced dust density during minimum obscuration. Obscuration events are explained by an increase in optical depth caused by the newly condensed dust. The mass loss rates are significantly higher than in intermediate-period single Miras but in agreement with longer-period O-rich AGB stars

RR Tel: Determination of Dust Properties During Minimum Obscuration

the ISO infrared spectra and the SAAO long-term JHKL photometry of RR Tel in the epochs during minimum obscuration are studied in order to construct a circumstellar dust model. the spectral energy distribution in the near- and the mid-IR spectral range (1–15 μm) was obtained for an epoch without the pronounced dust obscuration. the DUSTY code was used to solve the radiative transfer through the dust and to determine the circumstellar dust properties of the inner dust regions around the Mira component. Dust temperature, maximum grain size, dust density distribution, mass-loss rate, terminal wind velocity and optical depth are determined. the spectral energy distribution and the long-term JHKL photometry during an epoch of minimum obscuration show almost unattenuated stellar source and strong dust emission which cannot be explained by a single dust shell model. We propose a two-component model consisting of an optically thin circmustellar dust shell and optically thick dust outside the line of sight in some kind of a flattened geometry, which is responsible for most of the observed dust thermal emission

CH Cygni 1987-89: The inactive state as a precursor to the new outburst

In order to help answering the question generally posed for symbiotic stars: are the apparently inactive periods quiescent at all, or should they be regarded merely as a transition between adjacent outbursts, we tried to establish correlation between the subtle phenomena in the time evolution of the cool giant's photosphere and emission line profiles of the symbiotic star CH Cygni during the period 1987-89. Optical spectra of this star in its inactive state taken at the Haute Provence Observatory as well as the spectra of late type giant's of the same spectral type have been used. The comparison of the results obtained suggests that the time evolution of the physical parameters of CH Cyg reflect the symbiotic phenomena rather than the intrinsic variability of the cool component. The time behaviour of the Balmer emission line profiles rules out the general validity of the established models. An acceptable model valid at least for the observed period has been proposed. According to it, an envelope of variable optical thickness surrounds the hot component. The development of its inner radius, of $\rm H \alpha$ and $\rm H \beta$ line profiles and of the $\lambda5007~\rm [OIII]$ nebular line leads to the conclusion that the inactive state is not stationary, but is gradually evolving in time toward the new activity of the star

Circumstellar Dust in Symbiotic Miras during Obscuration Events

International audienceWe present a study of circumstellar dust properties in the symbiotic Miras RX Pup, V835 Cen, RR Tel and R Aqr, which show obscuration events during the observed time intervals. The obscuration events, as seen from the light curves corrected for Mira pulsations, have been investigated in view of the change of colors caused by the circumstellar dust. Assuming a spherical temperature distribution of the dust in the close neighborhood of the Mira, the DUSTY code was used to solve the radiative transfer in order to determine the dust temperature and its properties in each particular case. The preliminary results of this study provide information on the nature of the dust during the obscuration events

The region of Fe II emission line formation of the symbiotic nova RR Telescopii

In our investigation of the region of formation of the Fe II emission lines in RR Tel, we have applied the SAC method to the optical Fe II emission line fluxes measured by Crawford et al. (1999). It is possible to determine physical parameters of the line emitting region, because of the presence both of lines with large and much smaller optical thicknesses. The values we obtained, given in Tables 3 and 4, are limits in most cases. The upper limit to the excitation temperature of the metastable levels in the permitted line region of 6600 K, is close to the value of this temperature in the forbidden line region. Other excitation temperature limits corresponding to level population ratios were also found. The permitted lines are formed in a region with a radius between $1.8 \times 10^{12}$ cm and $1.6 \times 10^{14}$ cm, while the forbidden lines are formed in a region with a minimum radius of $5.3 \times 10^{12}$ cm. The populations of the lower levels of the permitted lines indicate a minimum column density of Fe+ of $3.0 \times 10^{18}$ atoms cm-2 and, by assuming cosmic abundances, to a minimum column density of $7.5 \times 10^{22}$ atoms cm-2 for H. If we assume a minimum radius of $1.0 \times 10^{14}$ cm, which is supposed to be that of dust condensation of the cool Mira component of this symbiotic binary, a minimum mass loss rate of $3.5 \times 10^{-6}~ M_{\rm o}$ yr-1 is found. Our results support a model according to which both the permitted and the forbidden lines are formed in the wind of the cool Mira component above the regions where absorption by dust is important. The forbidden and the permitted lines are not formed in quite the same region, the former being most probably formed further out in the part of an accelerated wind which is ionized by the hot component