32 research outputs found
Asteroseismology of close binary stars
In this review paper, we summarise the goals of asteroseismic studies of
close binary stars. We first briefly recall the basic principles of
asteroseismology, and highlight how the binarity of a star can be an asset, but
also a complication, for the interpretation of the stellar oscillations. We
discuss a few sample studies of pulsations in close binaries and summarise some
case studies. This leads us to conclude that asteroseismology of close binaries
is a challenging field of research, but with large potential for the
improvement of current stellar structure theory. Finally, we highlight the best
observing strategy to make efficient progress in the near future.Comment: Invited Review Talk at S240 of the IAU: To appear in: Binary Stars as
Critical Tools and Tests in Contemporary Astrophysics, Eds W. Hartkopf, E.
Guinan, P. Harmanec. 10 pages, 4 figure
Constraining the properties of delta Scuti stars using spectroscopic eclipsing binary systems
Many stars exhibit stellar pulsations, favoring them for asteroseismic
analyses. Interpreting the oscillations requires some knowledge of the
oscillation mode geometry (spherical degree, radial and azimuthal orders). The
delta Scuti stars (1.5 - 2.5 M_sol) often show just one or few pulsation
frequencies. Although this may promise a successful seismological analysis, we
may not know enough about either the mode or the star to use the oscillation
frequency to improve the determination of the stellar model, or probe the
star's structure. For the observed frequencies to be used successfully as
seismic probes of these objects, we need to concentrate on stars for which we
can reduce the number of free parameters in the problem, such as binary systems
or open clusters. We investigate how much our understanding of a delta Scuti
star is improved when it is in a detached eclipsing binary system instead of
being a single field star. We use singular value decomposition to explore the
precision we expect in stellar parameters (mass, age and chemical composition)
for both cases. We examine how the parameter uncertainties propagate to the
luminosity - effective temperature diagram and determine when the effort of
obtaining a new measurement is justified. We show that for the single star, a
correct identification of the oscillation mode is necessary to produce strong
constraints on the stellar model properties, while for the binary system the
observations without the pulsation mode provide the same or better constraints
on the stellar parameters. In the latter case, ...Comment: emulateapj 16 pages, accepted Ap
A multi-wavelength study of the radio source G296.7-0.9: confirmation as a Galactic supernova remnant
We present a multi-wavelength study of the radio source G296.7-0.9. This
source has a bilateral radio morphology, a radio spectral index of -0.5 +/-
0.1, sparse patches of linear polarisation, and thermal X-rays with a bright
arc near the radio boundary. Considering these characteristics, we conclude
that G296.7-0.9 is a supernova remnant (SNR). The age and morphology of the SNR
in the context of its environment suggest that the source is co-located with an
HII region, and that portions of the shock front have broken out into a lower
density medium. We see no evidence for a neutron star or pulsar wind nebula
associated with SNR G296.7-0.9.Comment: 11 pages with 9 figures and 2 tables. Accepted for publication in
MNRA
A Search for Pulsating, Mass-Accreting Components in Algol-Type Eclipsing Binaries
We present a status report on the search for pulsations in primary componants of Algols systems (oEA stars). Analysis of 21 systems with A0-F2 spectral type primaries revealed pulsations in two systems suggesting that of the order of ten persent of Algols primaries in this range are actually pulsators
Photometric mode identification methods of nonradial pulsations in eclipsing binaries I. -- Dynamic Eclipse Mapping
We present the Dynamic Eclipse Mapping (DEM) method designed specifically to
reconstruct the surface intensity patterns of non-radial stellar oscillations
in eclipsing binaries. The method needs a geometric model of the binary,
accepts the light curve and the detected pulsation frequencies on input, and on
output yields estimates of the pulsation patterns, in form of images -- thus
allowing a direct identification of the surface mode numbers.
Since it has minimal modelling requirements and can operate on photometric
observations in arbitrary wavelength bands, DEM is well suited to analyze the
wide-band time series collected by space observatories.
The method was extensively tested on simulated data, in which almost all
photometrically detectable modes with a latitudinal complexity
were properly restored. Multimode pulsations can be also reconstructed in a
natural manner, as well as pulsations on components with tilted rotation axis
of known direction. It can also be used in principle to isolate the
contribution of hidden modes from the light curve.
Sensitivity tests show that moderate errors in the geometric parameters and
the assumed limb darkening can be partially tolerated by the inversion, in the
sense that the lower degree modes are still recoverable. Tidally induced or
mutually resonant pulsations, however, are an obstacle that neither the eclipse
mapping, nor any other inversion technique can ever surpass.
We conclude that, with reasonable assumptions, Dynamic Eclipse Mapping could
be a powerful tool for mode identification, especially in moderately close
eclipsing binary systems, where the pulsating component is not seriously
affected by tidal interactions so that the pulsations are intrinsic to them,
and not a consequence of the binarity.Comment: Accepted for publication in MNRAS. 16 pages, 11 figures and 5 table
Radial Velocity variations of the roAp-star HD122970: new results. Veröffentlichungen der Kommission für Astronomie|Communications in Asteroseismology|Communications in Asteroseismology 145 144|
Spectral Typing Stars in the COROT Field Using the Objective Prism of the TLS 2m telescope: A status report
Eclipsing Systems with Pulsating Components (Types β Cep, δ Sct, γ Dor or Red Giant) in the Era of High-Accuracy Space Data
A search for pulsating, mass-accreting components in Algol-type eclipsing binaries
We present a status report on the search for pulsations in primary componants of Algols systems (oEA stars). Analysis of 21 systems with A0-F2 spectral type primaries revealed pulsations in two systems suggesting that of the order of ten persent of Algols primaries in this range are actually pulsators. © Springer Science+Business Media B.V. 2006