M. Friedjung

A catalogue of symbiotic stars

We present a new catalogue of symbiotic stars. In our list we include 188 symbiotic stars as well as 28 objects suspected of being symbiotic. For each star, we present basic observational material: coordinates, V and K magnitudes, ultraviolet (UV), infrared (IR), X-ray and radio observations. We also list the spectral type of the cool component, the maximum ionization potential observed, references to finding charts, spectra, classifications and recent papers discussing the physical parameters and nature of each object. Moreover, we present the orbital photometric ephemerides and orbital elements of known symbiotic binaries, pulsational periods for symbiotic Miras, Hipparcos parallaxes and information about outbursts and flickering.

The characteristics of the cool component of the cataclysmic binary AE Aquarii derived from its HIPPARCOS parallax

Abstract Observations of the parallax of the cataclysmic binary AE Aqr, using the HIPPARCOS satellite, are combined with the published spectrum and magnitudes in the K band. The radius of the cool component of the binary is probably significantly larger than that of a main sequence star of the same spectral type, though the errors and uncertainties do not make this result completely certain.

First unambiguous X-ray detection of R Aquarii

Coordinated UV and X-ray observations of the symbiotic Mira R Aqr obtained with IUE and Exosat during June and December of 1985 at phases 0.0 and 0.5 of the Mira light curve are analyzed. Consideration is given to two models for the X-ray source in R Aqr. The first assumes that high-energy photons from a central source photoionize some parts of the circumstellar matter, while the second model assumes that emission is associated with shocks arising as ejected material interacts with the circumstellar environment. 25 references.

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

Aims. 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. Methods. 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 American Association of Variable Star Observers’ (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. Results. 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 JD 2 446 600. 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. Conclusions.

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 10 12 cm and 1:6 10 14 cm, while the forbidden lines are formed in a region with a minimum radius of 5:3 10 12 cm. The populations of the lower levels of the permitted lines indicate a minimum column density of Fe+ of 3:0 10 18 atoms cm 2 and, by assuming cosmic abundances, to a minimum column density of 7:5 10 22 atoms cm 2 for H. If we assume a minimum radius of 1:0 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 3:510 6 Mo 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.

Analysis of the circumstellar environment of the B[ e] star HD 45677 (FS Canis Majoris)

Aims. We studied the circumstellar environment of the B[e] star HD 45677 through the analysis of the emission lines from ionized metals. Methods. We used the statistical approach of the self absorption curve method (SAC) to derive physical parameters of the line emitting region. Results. The Fe II and Cr II double-peaked emission line structure is explained by the presence of a thin absorption component red shifted by ∼ 3k m s −1 . This absorption component can be interpreted geometricaly as being due to infalling material perpendicularly to the disk seen nearly pole-on, as indicated by the emission line structure. The Cr II and Fe II emission lines have a complex structure with two (narrow and broad) components, of 45 and 180 km s −1 FWHM for the permitted lines and 25 and 100 km s −1 FWHM for the forbidden ones, respectively. From our best data set of 1999, we obtained a Boltzmann-type population law whose excitation temperature is 3900 +900 −600 K and 3150 +350 −300 K for the narrow component lower and upper levels respectively. We obtained an excitation temperature of 3400 +350 −300 K for the broad component upper levels. The forbidden lines are found to be formed in the outer regions with higher excitation temperatures of 10 500 ± 1000 K and 8000 ± 1500 K for the narrow and broad components respectively in 1999. Our results are consistent with line formation in a rotating disk, around a young star. In the framework of a very simplified geometrical model, we argue that the narrow components are principaly emitted by an optically thin disk seen nearly pole-on, in a region whose minimum radius is estimated to be 4×10 12 cm, while the broad ones are formed in a disk-linked wind.

A long term spectroscopic and photometric study of the old nova HR Delphini

Context. The Nova HR Del, discovered in 1967, was found to be exceptionally bright in the optical and UV during the whole lifetime of the IUE satellite (ending in 1996) and appears to still be extremely luminous today. The reason for this continuing activity is not clear, but continuing weak thermonuclear burning might be involved. Aims. We therefore need to better understand the processes at play in HR Del. Methods. HR Del was thus monitored over several years, both in broad band photometry and spectroscopically in the Hα spectral region. Results. The profile of the Hα line shows two components: a narrow, central component and broader wings. The former is most easily understood as the result of an accretion disk whose geometry might lead it to partly occult certain regions of itself. That component shows something like an S wave with an orbital phase dependence, suggesting that it could be due to a spot bright in Hα. The wide component must come from another region, with a probably non-negligible contribution from the material ejected during the 1967 outburst. Non-orbital variations of the Hα equivalent width were found both on long and short time scales. Similar variations were found in the photometry, showing a component with a clear dependence on the orbital phase, however with no obvious relation with the Hα variations. Conclusions. The orbital part of the photometric variations can be explained by irradiation of the companion, while the properties of Hα are explicable by the presence of an accretion disk and a spot bright in Hα.

Line formation regions of the UV spectrum of CI Cygni

Aims. They are the interpretation of the emission line formation regions in CI Cygni Methods. They involve the examination of radial velocities and fluxes of ultraviolet emission lines at different epochs, deduced from archival IUE and GRHS/HST spectra. Results. The line fluxes give electron densities and were in addition used to calculate emission measures, suggesting line formation in regions rather smaller than the binary separation. Examination of the radial velocities led to us to find a systematic redshift of the high ionization resonance lines with respect to the intercombination, and He ii lines. Possible explanations of the redshift and the high resolution GHRS C iv profile are discussed. We favour that involving resonance line absorption by a circum-binary region most probably in an asymmetric wind interaction shell or in a wind from the accretion disk.

Do novae have optically thick winds during outburst with large deviations from spherical symmetry

Context. The evidence for the presence of optically thick winds that are produced by classical novae after optical maximum has been challenged in recent papers. In addition, signs of orbital phase-dependent photometric variations, sometimes seen quite early in the development of nova outbursts, are hard to interpret in the framework of optically thick envelopes and especially winds. Aims. A general discussion of the assumption of optically thick winds with increasing ejection velocities during the early stages of novae after their explosion is needed, also to clarify ideas about novae and in particular to contribute to the understanding of the behaviour of novae V1500 Cyg and V1493 Aql, which show phase-dependent variations during the very early decline after the outburst. Methods. We considered possible ways of overcoming the apparent contradiction of phase-ependent variations through the production of deviations from spherical symmetry of the winds and made order-of-magnitude estimates for different theoretical scenarios that might produce these deviations. Results. We found that large deviations from the spherical symmetry of the optically thick winds in early phases after the explosion can easily explain the problem of variations. In particular, the presence of a magnetic field might have had a non-negligible effect on the wind of V1500 Cyg, while at the present there is not enough information available concerning V1493 Aql. Conclusions. Optically thick winds/envelopes are almost certainly present in the early stages after the optical maximum of a nova, while it is difficult to make pure Hubble-flow models fit the observations of those stages. New more detailed observational and theoretical work, in particular including the effects of magnetic fields on the winds, is needed.

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.