304 research outputs found
Kinematics of W UMa-type binaries and evidences on the two types of formation
The kinematics of 129 W UMa binaries is studied and its implications on the
contact binary evolution is discussed. The sample is found to be heterogeneous
in the velocity space that kinematically younger and older contact binaries
exist in the sample. Kinematically young (0.5 Gyr) sub-sample (MG) is formed by
selecting the systems which are satisfying the kinematical criteria of moving
groups. After removing the possible MG members and the systems which are known
to be members of open clusters, the rest of the sample is called Field Contact
Binaries (FCB). The FCB has further divided into four groups according to The
orbital period ranges. Then a correlation has been found in the sense that
shorter period less massive systems have larger velocity dispersions than the
longer period more massive systems. Dispersions in the velocity space indicates
5.47 Gyr kinematical age for the FCB group. Comparing with the field
chromospherically active binaries (CAB), presumably detached binary progenitors
of the contact systems, the FCB appears to be 1.61 Gyr older. Assuming an
equilibrium in the formation and destruction of CAB and W UMa systems in the
Galaxy, this age difference is treated as empirically deduced lifetime of the
contact stage. Since the kinematical ages of the four sub groups of FCB are
much longer than the 1.61 Gyr lifetime of the contact stage, the pre-contact
stages of FCB must dominantly be producing the large dispersions. The
kinematically young (0.5 Gyr) MG group covers the same total mass, period and
spectral ranges as the FCB. But, the very young age of this group does not
leave enough room for pre-contact stages, thus it is most likely that those
systems were formed in the beginning of the main-sequence or during the
pre-main-sequence contraction phase.Comment: 19 pages, including 11 figures and 5 tables, accepted for publication
in MNRA
Kinematics of the chromospherically active binaries and evidence of an orbital period decrease in binary evolution
Kinematics of 237 Chromospherically Active Binaries (CAB) were studied. The
sample is heterogeneous with different orbits and physically different
components from F to M spectral type main sequence stars to G and K giants and
super giants. The computed , , space velocities indicate the sample
is also heterogeneous in the velocity space. That is, both kinematically
younger and older systems exist among the non-evolved main sequence and the
evolved binaries containing giants and sub giants. The kinematically young
(0.95 Gyr) sub-sample (N=95), which is formed according to the kinematical
criteria of moving groups, was compared to the rest (N=142) of the sample (3.86
Gyr) in order to investigate observational clues of the binary evolution.
Comparing the orbital period histograms between the younger and older
sub-samples, evidences were found supporting Demircan's (1999) finding that the
CAB binaries lose mass (and angular momentum) and evolve towards shorter
orbital periods. The evidence of mass loss is noticeable on the histograms of
the total mass (), which is compared between the younger
(available only N=53 systems) and older sub-samples (available only N=66
systems). The orbital period decrease during binary evolution is found to be
clearly indicated by the kinematical ages of 6.69, 5.19, and 3.02 Gyr which
were found in the sub samples according to the period ranges of ,
, and among the binaries in the older sub
sample.Comment: 26 pages, including 11 figures and 5 tables, 2004, MNRAS, 349, 106
The Spectroscopic Orbits of Three Double-lined Eclipsing Binaries: I. BG Ind, IM Mon, RS Sgr
We present the spectroscopic orbit solutions of three double-lines eclipsing
binaries, BG Ind, IM Mon and RS Sgr. The first precise radial velocities (RVs)
of the components were determined using high resolution echelle spectra
obtained at Mt. John University Observatory in New Zealand. The RVs of the
components of BG Ind and RS Sgr were measured using Gaussian fittings to the
selected spectral lines, whereas two-dimensional cross-correlation technique
was preferred to determine the RVs of IM Mon since it has relatively short
orbital period among the other targets and so blending of the lines is more
effective. For all systems, the Keplerian orbital solution was used during the
analysis and also circular orbit was adopted because the eccentricities for all
targets were found to be negligible. The first precise orbit analysis of these
systems gives the mass ratios of the systems as 0.894, 0.606 and 0.325,
respectively for BG Ind, IM Mon and RS Sgr. Comparison of the mass ratio
values, orbital sizes and minimum masses of the components of the systems
indicates that all systems should have different physical, dynamical and
probable evolutionary status.Comment: 17 pages, 6 figures and 4 tables, accepted for publication in New
Astronom
A catalog of chromospherically active binary stars (third edition)
Chromospherically Active Binaries (CAB) catalogue have been revised and
updated. With 203 new identifications, the number of CAB stars is increased to
409. Catalogue is available in electronic format where each system has various
number of lines (sub-orders) with a unique order number. Columns contain data
of limited number of selected cross references, comments to explain
peculiarities and position of the binarity in case it belongs to a multiple
system, classical identifications (RS CVn, BY Dra), brightness and colours,
photometric and spectroscopic data, description of emission features (Ca II
H&K, , UV, IR), X-Ray luminosity, radio flux, physical quantities
and orbital information, where each basic entry are referenced so users can go
original sources.Comment: 5 pages, including 2 figures and 3 tables, accepted for publication
in MNRA
Dynamical evolution of active detached binaries on log Jo - log M diagram and contact binary formation
Orbital angular momentum (Jo), systemic mass (M) and orbital period (P)
distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W
UMa) systems were investigated. The diagrams of log Jo - log P, log M - log P
and log Jo-log M were formed from 119 CAB and 102 W UMa stars. The log Jo-log M
diagram is found to be most meaningful in demonstrating dynamical evolution of
binary star orbits. A slightly curved borderline (contact border) separating
the detached and the contact systems was discovered on the log Jo - log M
diagram. Since orbital size (a) and period (P) of binaries are determined by
their current Jo, M and mass ratio q, the rates of orbital angular momentum
loss (dlog Jo/dt) and mass loss (dlog M/dt) are primary parameters to determine
the direction and the speed of the dynamical evolution. A detached system
becomes a contact system if its own dynamical evolution enables it to pass the
contact border on the log Jo - log M diagram. Evolution of q for a mass loosing
detached system is unknown unless mass loss rate for each component is known.
Assuming q is constant in the first approximation and using the mean decreasing
rates of Jo and M from the kinematical ages of CAB stars, it has been predicted
that 11, 23 and 39 cent of current CAB stars would transform to W UMa systems
if their nuclear evolution permits them to live 2, 4 and 6 Gyrs respectively.Comment: 28 pages, including 6 figures and 2 tables, accepted for publication
in MNRA
Predicting Remaining Useful Life with Similarity-Based Priors
Prognostics is the area of research that is concerned with predicting the remaining useful life of machines and machine parts. The remaining useful life is the time during which a machine or part can be used, before it must be replaced or repaired. To create accurate predictions, predictive techniques must take external data into account on the operating conditions of the part and events that occurred during its lifetime. However, such data is often not available. Similarity-based techniques can help in such cases. They are based on the hypothesis that if a curve developed similarly to other curves up to a point, it will probably continue to do so. This paper presents a novel technique for similarity-based remaining useful life prediction. In particular, it combines Bayesian updating with priors that are based on similarity estimation. The paper shows that this technique outperforms other techniques on long-term predictions by a large margin, although other techniques still perform better on short-term predictions.</p
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