28 research outputs found
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
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
Radial Velocity variations of the roAp-star HD122970: new results. Veröffentlichungen der Kommission fĂŒr 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
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
Frequency spectrum of the rapidly-oscillating mass-accreting component of the Algol-type system ASÂ Eri
The first multisite photometric campaign devoted to the rapidly
oscillating mass-accreting (primary) component of the Algol-type eclipsing
binary system ASÂ Eri
has confirmed the presence of rapid pulsations with frequency
59.03116Â âd-1, and revealed the second and third
oscillation modes with frequencies 62.5631Â âd-1
and 61.6743Â âd-1, respectively. These modes are related to the 5-6 overtone
oscillations and are among the shortest periods excited in non-magnetic
MS A-F stars.
The nearly equator-on visibility of eclipsing binaries
help to narrow the range of possible mode identifications for the
detectable modes as radial or ,
and .
We checked the high-order pulsation-to-orbital synchronization
(POS) using the trial mode identification and the Doppler
effect correction for frequencies of non-radial pulsation.
We found that or
and identifications for and modes
respectively satisfied the high-order POS. These mode
identifications are in agreement with the range of modes
visible in disk integrated light of an equator-on visible
pulsating component.â©The wavelength distribution of pulsation amplitudes in ASÂ Eri is largest
in the Strömgren u filter and decreases toward longer wavelengths.
We place ASÂ Eri and other known mass-accreting pulsating components of
Algols on HR-diagram.
They are located inside the instability strip on the Main Sequence.
We also discuss the peculiar evolutionary status of primary
components in Algols and stress that they are not normal ÎŽ Scuti
stars, but form a separate group of pulsators. Finally, we discuss
proximity and eclipse effects, and have simulated the effect of primary
minimum data gaps that may produce the 1/ alias sidelobes
in DFT analysis of eclipsing binary data. Aliases from gaps in primary
minimum observations seem to be the principal limitation on spectral
window functions in asteroseismic studies of eclipsing binaries
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