31 research outputs found
High resolution spectroscopy of symbiotic stars. VI. Orbital and stellar parameters for AR Pav
We present new dynamical parameters of the AR Pav binary system.
Ourobservations consist of a series of high resolution optical/NIR spectra from
which we derive the radial velocity curve of the red giant as well as its
rotation velocity. Assuming co-rotation, we determine the stellar radius (130
R_solar) of the red giant. Based on this we derive the red giant's luminosity
and mass (2.0 M_solar) as well as the distance of the system (4.9 kpc). The
binary mass function finally yields the companion's mass (0.75 M_solar) and the
binary separation (1.95 AU). We find that the red giant does not fill its Roche
lobe. We review the radial velocity data of Thackeray and Hutchings (1974), and
compare it with our red giant's orbit. We find that their RV curves of the blue
absorption system and the permitted emission lines are in anti-phase with the
red giant, and that the forbidden emission lines are shifted by a quarter of a
period. The blue absorptions and the permitted emission lines are associated
with the hot companion but not in a straightforward way. The blue absorption
system only tracks the hot component's orbital motion whilst it is in front of
the red giant, whereas at other phases line blanketing by interbinary material
leads to perturbations. We finally present UV light curves based on IUE archive
spectra. We clearly detect eclipses in the continuum at all wavelengths. The
eclipse light curves are unusual in that they show a slow and gradual decline
prior to eclipse which is followed by a sharp increase after eclipse.Comment: 9 pages, 5 figure
A multi-epoch spectrophotometric atlas of symbiotic stars
A multi-epoch, absolute-fluxed spectral atlas extending from about 3200 to
9000 Ang is presented for 130 symbiotic stars, including members of the LMC,
SMC and Draco dwarf galaxies. The fluxes are accurate to better than 5% as
shown by comparison with Tycho and ground-based photometric data. The spectra
of 40 reference objects (MKK cool giant standards, Mira and Carbon stars,
planetary nebulae, white dwarfs, hot sub-dwarfs, Wolf-Rayet stars, classical
novae, VV Cep and Herbig Ae/Be objects) are provided to assist the
interpretation of symbiotic star spectra. Astrometric positions and
counterparts in astrometric catalogues are derived for all program symbiotic
stars.Comment: A&A, in press (264 pages, 3 tables, 256 figures). The spectra are
available in electronic form from the authors. Only a sample of the whole
paper is given here. The full text can be downloaded from
http://ulisse.pd.astro.it/symbio-atlas/ where the spectra in electronic form
of the 40 reference objects can be found to
UV and X-Ray Monitoring of AG Draconis During the 1994/1995 Outbursts
The recent 1994-1995 active phase of AG Draconis has given us for the first
time the opportunity to follow the full X-ray behaviour of a symbiotic star
during two successive outbursts and to compare with its quiescence X-ray
emission. With \ros observations we have discovered a remarkable decrease of
the X-ray flux during both optical maxima, followed by a gradual recovering to
the pre-outburst flux. In the UV the events were characterized by a large
increase of the emission line and continuum fluxes, comparable to the behaviour
of AG Dra during the 1980-81 active phase. The anticorrelation of X-ray/UV flux
and optical brightness evolution is shown to very likely be due to a
temperature decrease of the hot component. Such a temperature decrease could be
produced by an increased mass transfer to the burning compact object, causing
it to slowly expand to about twice its original size.Comment: 12 pages postscript incl. figures, Proc. of Workshop on Supersoft
X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996
The hydrogen and helium lines of the symbiotic binary Z And during its brightening at the end of 2002
High resolution observations in the region of the lines Halpha, He II 4686
and Hgamma of the spectrum of the symbiotic binary Z And were performed during
its small-amplitude brightening at the end of 2002. The profiles of the
hydrogen lines were double-peaked. These profiles give a reason to suppose that
the lines can be emitted mainly by an optically thin accretion disc. The Halpha
line is strongly contaminated by the emission of the envelope, therefore for
consideration of accretion disc properties we use the Hgamma line. The Halpha
line had broad wings which are supposed to be determined mostly from radiation
damping but high velocity stellar wind from the compact object in the system
can also contribute to their appearance. The Hgamma line had a broad emission
component which is assumed to be emitted mainly from the inner part of the
accretion disc. The line He II 4686 had a broad emission component too, but it
is supposed to appear in a region of a high velocity stellar wind. The outer
radius of the accretion disc can be calculated from the shift between the
peaks. Assuming, that the orbit inclination can ranges from 47 to
76, we estimate the outer radius as 20 - 50 R_sun. The behaviour of the
observed lines can be considered in the framework of the model proposed for
interpretation of the line spectrum during the major 2000 - 2002 brightening of
this binary.Comment: 19 pages, 5 figures. Accepted for publication in Astronomy Report
Spectral classification of the cool giants in symbiotic systems
We derive the spectral types
of the cool giants in about 100 symbiotic systems.
Our classification is mainly based on near IR spectra
in order to avoid the contamination of the spectrum
by the nebula and the hot component in the visual region.
The accuracy of our spectral types is approximately one spectral
subclass, similar to previous near IR classification
work, and much better than visual spectral type estimates.
Strong, intrinsic spectral type variations ( spectral subtypes)
are only seen in systems containing pulsating mira variables.
We present a catalogue of spectral types for cool giants
in symbiotic systems which also includes determinations taken from the
literature. The catalogue gives spectral types for the
cool giants in about 170 systems which is nearly the full
set of confirmed symbiotics.
Based on our classifications we discuss the distribution of
spectral types of the cool giants in galactic symbiotic binaries. We find
that the spectral types cluster strongly between M3 and M6, with
a peak at M5. The distribution of
systems with a mira variable component peaks even later, at
spectral types M6 and M7. This is a
strong bias towards late spectral types when compared to
red giants in the solar neighbourhood. Also the frequency of
mira variables is much larger among symbiotic giants. This
predominance of very late M-giants in symbiotic systems seems
to indicate that large mass loss is a key ingredient for
triggering symbiotic activity on a white dwarf companion.
Further we find for symbiotic systems a strong correlation
between the spectral type of the cool giant and the orbital period.
In particular we find a tight relation for the minimum orbital
period for symbiotic systems with red giants of a given spectral
type. This limiting line in the spectral type –
orbital period diagram seems to be equivalent with the
relation , where R is the radius of the red giant and
the distance from the center of the giant to the inner
Lagrangian point L1. This correlation possibly discloses
that symbiotic stars are – with probably only one exception
in our sample – well detached binary systems