237 research outputs found
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
Bipolar ejection by the symbiotic binary system Z And during its 2006 outburst
High resolution data in the region of the line Halpha have been obtained at
the time of the light maximum and after it of the 2006 optical outburst of the
symbiotic binary Z And. A blue-shifted absorption component indicating outflow
velocity of about 1400 km/s as well as additional emission components with
similar velocities, situated on the two sides of the main peak of the line were
observed during that time. It is suggested that all of them are spectral
signature of bipolar outflow, observed for the first time in the optical
spectrum of this binary. The emission measure and the mass of the nebular part
of the streams were estimated approximately.Comment: 5 pages, 2 figures; to be published in MNRAS Letter
Interpretation of the line spectrum of classical symbiotic stars in the scenario for their prototype Z And
Results of the study of the symbiotic binary Z And during its recent active
phase 2000 -- 2010 when it experienced a series of six optical outbursts are
presented. High-resolution spectra obtained during the first and fourth
outburst, which was the strongest one, have been analyzed. These data are
compared with results of theoretical computations. The comparison provides
information about the behaviour of the system during the entire active phase
rather than during an individual outburst. In particular it was found
fundamental difference between the first outburst, which opened the active
phase, and the recurrent outbursts - namely, the presence of bipolar collimated
optical outflow during some of the recurrent outbursts. A scenario that can
explain all the spectroscopic phenomena observed during this active phase as
well as previous active phases of Z And is proposed. The possibility to use
this scenario for explanation of the line spectrum of other classical symbiotic
stars during their active phases is motivated.Comment: 10 pages, 10 figures; to be published in AIP Conf. Proc., School and
Workshop on SPACE PLASMA PHYSICS, Kiten, Bulgaria; corrected typo
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