Red Giant Component Research Articles

The destructive effects of binary encounters on red giants in the Galactic Centre

We consider the destructive effects of encounters between binaries and red giant stars in the Galactic Centre. Such encounters may explain the observed depletion of luminous red giants within the central 0.2 pc of the galaxy. We consider encounters involving 2- and 8-M⊙ red giants, and thus span the range of stellar masses contributing to the most luminous red giants observed in the Galactic Centre. To explore the phase space of encounters thoroughly, we simulate 18 × 103 encounters using a modified four-body code in which the red giant core and components of the binary are treated as point masses, and where the envelope configuration is assumed to remain static throughout the encounter. We then rerun a small number of encounters with a smoothed particle hydrodynamics (SPH) code to confirm the reliability of conclusions drawn from the four-body runs. We see two possible pathways to red giant destruction. A large fraction of encounters lead to the formation of common-envelope systems, where two compact objects (drawn from the red giant core and the components of the original binary) form a binary within a common gaseous envelope, whilst the third body is ejected. The destruction of the red giant will then follow when the envelope is ejected as the binary hardens. In a smaller number of encounters, the intruding binary passes through the star and ejects the red giant core from the envelope. The red giant envelope will then disperse on short time-scales. We compute the time-scales for both of these processes to occur in the Galactic Centre for a variety of binary populations.

Models for the remnants of recurrent novae - III. Comparison with the X-ray observations of RS Ophiuchi (1985)

Ealiers papers of this series developed a model for the interaction of ejecta with a circumstellar medium which was principally applied to the 1985 outburst of the recurrent nova RS Ophiuchi. Here the X-ray emission predicted by this model is compared in detail to EXOSAT observations of the outburst. Fits to the first observations 55 days after outburst lead to values for model parameters which are consistent with existing estimates : outburst energy ⇒ 1.1 × 10 43 erg; ejecta mass ⇒ 1.1 × 10 -6 M ⊙ ; and mass-loss rate into the wind of the red giant component ⇒ 6 × 10 12 g/cm. Once these parameters are fixed the model predicts the subsequent evolution of the X-ray emission

CH Cygni Half a Century Ago – Changing Activity of the Cool Component

CH Cyg was observed visually by Professor Władysław DziewulsKi in the years 1930–1940 at the Vilno Observatory, with the 15 cm refractor using Argelander’s method. As a sKillful and experienced observer he achieved the accuracy of his single measurement of about 0.05 mag. The series of his 652 estimates of CH Cyg has been recently reduced and is discussed in this paper.Apparently in those years the star was in relatively quiet state (like in the years 1970–1977), when in the visual region the light of only the red giant component of this binary is visible. We deduce it from:a)absence of any emission lines in spectra taKen by A. Joy in 1930 (Joy 1942)b)visual brightness of the star almost never exceeding 7.0 mag. what is typical for the quiet state of pure M6III spectrumc)red color, resulting from comparison of our visual brightnesses and the photographic ones published by S. Gaposchkin (1952)

A radio survey of symbiotic stars

view Abstract Citations (202) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Radio Survey of Symbiotic Stars Seaquist, E. R. ; Taylor, A. R. ; Button, S. Abstract The results of a VLA survey of 59 symbiotic stars at 4.9 GHz are presented. Seventeen of these were detected as radio sources, and eight of the detected stars were also observed at 1.5 GHz. The majority of the radio detections have large H-beta equivalent width, and there is also a positive correlation between radio luminosity and the spectral type of the red giant component. The radio emission is consistent with optically thick thermal bremsstrahlung from an ionized gas in all cases. A model is discussed in which the hot companion in a binary system ionizes a portion of a stellar wind from the late-type giant. Mass loss rates ranging from 10 to the -7th to 10 to the -6th solar mass/yr appear to be consistent with the radio emission. Publication: The Astrophysical Journal Pub Date: September 1984 DOI: 10.1086/162399 Bibcode: 1984ApJ...284..202S Keywords: Radio Astronomy; Stellar Radiation; Symbiotic Stars; Data Correlation; Flux Density; Giant Stars; H Beta Line; Stellar Models; Stellar Spectra; Astronomy full text sources ADS | data products SIMBAD (60) Related Materials (1) Erratum: 1987ApJ...317..555S