94 research outputs found
Radial Velocity Studies of Close Binary Stars.VII. Methods and Uncertainties
Methods used in the radial-velocity program of short-period binary systems at
the David Dunlap Observatory are described with particular stress on the
Broadening Function (BF) formalism. This formalism has permitted determination
of radial velocities from complex spectra of multiple-component systems with
component stars showing very different degree of rotational line broadening.
The statistics of random errors of orbital parameters is discussed on the basis
of the available orbital solutions presented in the six previous papers of the
series, each with ten orbits. The difficult matter of systematic uncertainties
in orbital parameters is illustrated for one typical case of GM Dra from the
most recent Paper VI.Comment: AASTeX5, 5 figures, extensively modified after the AJ revie
Contact binary stars of the W UMa type as distance tracers
Contact binaries can be used for distance determinations of stellar systems.
They are easy to discover and identify and are very abundant among solar-type
stars, particularly for M_V > +3. The period - luminosity - colour (PLC)
relations have similar properties to those for pulsating stars and can
currently predict individual values of M_V to about +/-0.25 mag.Comment: IAU Sydney 2003, JD13 Extragalactic Binaries, ed.I.Ribas, uses
elsart3.cl
Radial Velocity Studies of Close Binary Stars. XI
Radial-velocity measurements and sine-curve fits to the orbital radial
velocity variations are presented for ten close binary systems: DU Boo, ET Boo,
TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi and AG Vir. By this
contribution, the DDO program has reached the point of 100 published radial
velocity orbits. The radial velocities have been determined using an improved
fitting technique which uses rotational profiles to approximate individual
peaks in broadening functions.
Three systems, ET Boo, VW LMi and TV UMi, were found to be quadruple while AG
Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual
binary with years, was previously known to be a multiple
system, but we show that the second component is actually a close,
non-eclipsing binary. The new observations enabled us to determine the
spectroscopic orbits of the companion, non-eclipsing pairs in ET Boo and VW
LMi. The particularly interesting case is VW LMi, where the period of the
mutual revolution of the two spectroscopic binaries is only 355 days.
While most of the studied eclipsing pairs are contact binaries, ET Boo is
composed of two double-lined detached binaries and HL Dra is single-lined
detached or semi-detached system. Five systems of this group were observed
spectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-lined binary),
V566 Oph, AG Vir, but our new data are of much higher quality than the previous
studies.Comment: Accepted by AJ, August 2006, 10 figures, 3 table
The photometric-amplitude and mass-ratio distributions of contact binary stars
The distribution of the light-variation amplitudes, A(a), in addition to
determining the number of undiscovered contact binary systems falling below
photometric detection thresholds and thus lost to statistics, can serve as a
tool in determination of the mass-ratio distribution, Q(q), which is very
important for understanding of the evolution of contact binaries. Calculations
of the expected A(a) show that it tends to converge to a mass-ratio dependent
constant value for a->0. Strong dependence of A(a) on Q(q) can be used to
determine the latter distribution, but the technique is limited by the presence
of unresolved visual companions and by blending in crowded areas of the sky.
The bright-star sample to 7.5 magnitude is too small for an application of the
technique while the the Baade's Window sample from the OGLE project may suffer
stronger blending; thus the present results are preliminary and illustrative
only. Estimates based on the Baade's Window data from the OGLE project, for
amplitudes a>0.3 mag. where the statistics appear to be complete allowing
determination of Q(q) over 0.12<q<1, suggest a steep increase of Q(q) with
q->0. The mass-ratio distribution can be approximated by a power law, either
Q(q)~(1-q)^a1 with a1=6+/-2 or Q(q)~q^b1, with b1=-2+/-0.5, with a slight
preference for the former form. Both forms must be modified by the
theoretically expected cut-off caused by a tidal instability at about q_min
0.07-0.1. An expected maximum in Q(q), is expected to be mapped into a local
maximum in A(a) around 0.2-0.25 mag.Comment: AASTeX5, 12 figures, 5 tables, accepted by AJ, Aug.200
Radial Velocity Studies of Close Binary Stars.VIII
Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the seventh set of ten close binary systems: V410
Aur, V523 Cas, QW Gem, V921 Her, V2357 Oph, V1130 Tau, HN UMa, HX UMa, HD
93917, NSV 223. All systems, but three (V523 Cas, HD 93917, NSV 223), were
discovered photometrically by the Hipparcos mission. All systems are
double-lined (SB2) binaries and all, but the detached, very close system V1130
Tau, are contact binaries. The broadening-function permitted improvement of the
orbital elements for V523 Cas, which was the only system observed before for
radial velocity variations. Spectroscopic/visual companions were detected for
V410 Aur and HX UMa.Comment: AASTeX5, 4 figures, 3 tables, to appear AJ, June 200
Radial Velocity Studies of Close Binary Stars
ABSTRACT Radial velocity measurements and simple sine-curve Ðts to the orbital velocity variations are presented for the third set of 10 close binary systems : CN And, HV Aqr, AO Cam, YY CrB, FU Dra, RZ Dra, UX Eri, RT LMi, V753 Mon, and OU Ser. All systems except two (CN And and RZ Dra) are contact, double-line spectroscopic binaries, with four of them (YY CrB, FU Dra, V753 Mon, and OU Ser) being the recent discoveries of the Hipparcos satellite project. The most interesting object is V753 Mon with the mass ratio closest to unity among all contact systems (q \ 0.970^0.003) and large total mass [(M 1 Several of the studied systems are prime candidates for combined light and ] M 2 ) sin3 i \ 2.93^0.06]. radial velocity synthesis solutions
Light Curve Analysis of Hipparcos Data for the Massive O-type Eclipsing Binary UW CMa
Hipparcos photometric data for the massive O-type binary UW CMa were analysed
within the framework of the Roche model. Photometric solutions were obtained
for five mass ratios in the range. The system is found to
be in a contact configuration. Independently of , the best-fitting model
solutions correspond to the orbital inclination and the
temperature of the secondary component , at the fixed
temperature of the primary . Considering that the spectrum of the
secondary is very weak, photometric solutions corresponding to the contact
configuration favor the mass ratio smaller than unity (in which case the
luminosity of the secondary is smaller than that of the primary). The absolute
parameters of the system are estimated for different values of the mass ratio.Comment: 18 pages, 6 figure
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