148 research outputs found
The spectroscopic orbit and the geometry of R Aqr
R Aqr is one of the closest symbiotic binaries and the only D-type system
with radial velocity data suitable for orbital parameters estimation. The aims
of our study are to derive a reliable spectroscopic orbit of the Mira
component, and to establish connections between the orbital motion and other
phenomena shown by R Aqr. We reanalize velocity data recently published by
McIntosh & Rustan complemented by additional velocities. We find an eccentric
orbit (e=0.25) with a period 43.6 yr. This solution is in agreement with a
resolved VLA observation of this system. We demonstrate that the last 1974-1981
increase of extinction towards the Mira occured during its superior
spectroscopic conjunction, and can be due to obscuration by a neutral material
in the accreting stream. We also show that jet ejection is not connected with
the orbital position.Comment: 7 pages, 4 figures, accepted for publication in A&
HII regions in symbiotic binaries and their radio emission
The slow and dense wind from a symbiotic red giant can be significantly
deflected toward the orbital plane by the gravitational pull of the companion
star. In such an environment, the ionizing radiation from the companion creates
a highly asymmetric HII region. We present three-dimensional models of HII
regions in symbiotic S-type systems, for which we calculate radio maps and
radio spectra. We show that the standard assumption of spherically symmetric RG
wind results in wrong shapes, sizes and spectra of ionized regions, which in
turn affects the observational estimates of orbital separation and mass loss
rate. A sample of radio maps and radio spectra of our models is presented and
the results are discussed in relation to observational data.Comment: Accepted for publication in A&
Recurrent Novae at Quiescence: Systems with Giant Secondaries
Spectroscopic and photometric behaviour of the class of recurrent novae with
giant secondaries (T Coronae Borealis, RS Ophiuchi, V3890 Sagittarii and V745
Scorpii) at quiescence are presented in this study. The hot component in these
systems is variable, with the variability manifesting as variability in the
ultraviolet luminosity, the ultraviolet and optical emission line fluxes and in
the UBV/visual magnitudes. The variations are uncorrelated with the binary
orbital motion. The observed ultraviolet+optical spectral characteristics of
the hot component in these systems can be explained by a white dwarf+accretion
disc embedded in an envelope of wind from the M giant secondary. We suggest the
observed variations are a result of (a) fluctuations in the mass accretion
rate; (b) changes in the column density of the absorbing, optically thick, wind
envelope.Comment: 11 pages, 7 postscript figures. Uses laa.sty, eps.sty. To appear in
A&A (main journal
Circumstellar environment of RX Puppis
The symbiotic Mira, RX Pup, shows long-term variations in its mean light
level due to variable obscuration by circumstellar dust. The last increase in
extinction towards the Mira, between 1995 and 2000, has been accompanied by
large changes in the degree of polarization in the optical and red spectral
range. The lack of any obvious associated changes in the position angle may
indicate the polarization variations are driven by changes in the properties of
the dust grains (e.g. variable quantity of dust and variable particle size
distribution, due to dust grain formation and growth) rather than changes in
the viewing geometry of the scattering region(s), e.g. due to the binary
rotation.Comment: Paper presented at Torun 2000 conference on Post-AGB objects as a
phase of stellar evolution; 8 pages, 3 figure
The spectroscopic orbits and the geometrical configuration of the symbiotic binary AR Pavonis
We analyze optical and near infrared spectra of intermediate and high
resolution of the eclipsing symbiotic system AR Pavonis. We have obtained the
radial velocity curves for the red and the hot component from the M-giant
absorption lines and from the wings of Halpha, H and He II4686 emission
profiles, respectively. From the orbital elements we have derived the masses,
Mgiant=2.5 and Mhot =1.0 solar masses, for the red giant and the hot component,
respectively. We also present and discuss radial velocity patterns in the blue
cF absorption spectrum as well as various emission lines. In particular, we
confirm that the blue absorption lines are associated with the hot component.
The radial velocity curve of the blue absorption system, however, does not
track the hot companion's orbital motion in a straightforward way, and its
departures from an expected circular orbit are particularly strong when the hot
component is active. We suggest that the cF-type absorption system is formed in
material streaming from the giant presumably in a region where the stream
encounters an accretion disk or an extended envelope around the hot component.
The broad emission wings originate from the inner accretion disk or the
envelope around the hot star.We also suggest that the central absorption in H
profiles is formed in a neutral portion of the cool giant's wind which is
strongly concentrated towards the orbital plane. The nebula in AR Pav seems to
be bounded by significant amount of neutral material in the orbital plane. The
forbidden emission lines are probably formed in low density ionized regions
extended in polar directions and/or the wind-wind interaction zone.Comment: 12 pages, 5 figures, accepted by A&
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