176 research outputs found
V745\,Cassiopeia: an interacting young massive binary in a multiple star system
We present spectroscopic observations of the massive early type system
V745\,Cas, embedded in a multiple star system. The brightest star of the system
is the eclipsing binary V745\,Cas with an orbital period of 1.41 days. The
radial velocities of both components and light curves obtained by
and missions were analysed. The components of V745\,Cas are shown
to be a B0\,V primary with a mass M=18.310.51 M and radius
R=6.940.07 R and a B(1-2)\,V secondary with a mass
M=10.470.28 M and radius R=5.350.05 R.
Our analysis shows that both components fill their corresponding lobes,
indicating double contact configuration. Using the UBVJHK magnitudes and
interstellar absorption we estimated the mean distance to the system as
170050\,pc. The locations of the component stars in the mass-luminosity,
mass-radius, effective temperature-mass and surface gravity-mass are in
agreement with those of the main-sequence massive stars. We also obtained
photometry of the three visual companions and we estimate that all are B-type
stars based upon their de-reddened colours.We suspect that this multiple system
is probably a member of the Cas OB4 association in the arm of the
.Comment: 21 pages, 7 figures Accepted by MNRA
Is NP Aqr a new near-contact binary?
We present radial velocities of the double-lined spectroscopic binary NP Aqr.
The radial velocities and the optical light curves obtained by Hipparcos and
ASAS-3 are analyzed separately. The masses of the primary and secondary
components have been found to be 1.650.09 and 0.990.05 M,
respectively. The cross-correlation functions indicate triple peaks which show
presence of a tertiary star. The spectroscopic properties of this additional
component resemble to that of the primary star. The analysis of the light
curves yielded that the more massive primary star fills its corresponding Roche
lobe. The secondary component is at or near Roche lobe indicating a new
Lyrae-type near-contact binary. The orbital inclination is about 40
and, therefore, the observed light variations are produced only by the
proximity effects. Due to the absence of eclipses, the effective temperature of
the secondary star and the radii of the components could not be determined
accurately. We conclude that NP Aqr is a non-eclipsing double-lined
spectroscopic binary with a distance of about 1347 pc. The absolute
parameters of the components are also compared with the evolutionary models.
While the location of the primary star seems to be suitable with respect to its
mass in the Hertzsprung-Russell diagram, the secondary component is located as
if a star having a mass less than 0.6 M. This discrepancy is
originated from very low effective temperature determined only from the light
curve produced by proximity effects. The distance to the third star appears to
be very close to that of the close binary which indicates that it may be
dynamically bounded to the binary.Comment: 14 pages, 5 figure, Accepted by New Astronom
Long-term photometric and spectroscopic observations of the near-contact binary KR Cygni
We present the multi-color, five-year light curves and the first radial
velocities of the near-contact binary system KR Cyg. We derived the masses of
the components as 2.880.20 M and 1.260.07 M and
the radii as 2.590.06 R and 1.800.04 R. Analyses
of the UBVR light curves and the radial velocities indicate that none of the
components exactly fill their corresponding Roche lobes. We have calculated the
distance to the system of KR Cyg as {41112} pc using the observed apparent
UBV magnitudes and the bolometric corrections for the component stars. We also
searched for the empirical determination of albedo and effective temperature of
the cooler, less massive star of KR Cyg, and of two similar near contact
binaries AK CMi, and DO Cas. The residuals between the observed and computed
fluxes are attributed to the effect of mutual illumination which heats the
surface layers of the illuminated star and does vary not only its bolometric
albedo but also its limb-darkening coefficient and gravity-brightening
exponent. The analysis of the light curves shows that the effective albedos are
generally smaller than that expected from an envelope of convective star, being
mostly departed from the theoretical value at the B passband. As the reflected
light diminishes the effective temperature and, therefore, the luminosity of
the irradiated star increase. The observed bluer U-B colors during primary
minimum are attributed to the effects of mutual irradiation and multiple
scattering processes which may alter several characteristics of these systems.Comment: Accepted. 18 pages, 7 figures; 2012, October, Rev. Me
V1135 Herculis: a double-lined eclipsing binary with an Anomalous Cepheid
BVR light curves and radial velocities for the double-lined eclipsing binary
V1135\,Her were obtained. The brighter component of V1135\,Her is a Cepheid
variable with a pulsation period of 4.224330.00026 days. The orbital
period of the system is about 39.997820.00233 days, which is the shortest
value among the known Type\,II Cepheid binaries. The observed B, V, and R
magnitudes were cleaned for the intrinsic variations of the primary star. The
remaining light curves, consisting of eclipses and proximity effects, are
obtained. Our analyses of the multi-colour light curves and radial velocities
led to the determination of fundamental stellar properties of both components
of the interesting system V1135\,Her. The system consists of two evolved stars,
G1+K3 between giants and supergiants, with masses of M=1.4610.054
\Msun ~and M=0.5040.040 {\Msun} and radii of R=27.10.4
{\Rsun} and R=10.40.2 {\Rsun}. The pulsating star is almost filling
its corresponding Roche lobe which indicates the possibility of mass loss or
transfer having taken place. We find an average distance of d=7500450 pc
using the BVR magnitudes and also the V-band extinction. Location in the Galaxy
and the distance to the galactic plane with an amount of 1300 pc indicate that
it probably belongs to the thick-disk population. Most of the observed and
calculated parameters of the V1135\,Her and its location on the color-magnitude
and period-luminosity diagrams lead to a classification of an Anomalous
Cepheid.Comment: 25 pages, 9 Tables, 9 Figures, Accepted Revista Mexicana de
Astronom\'ia y Astrof\'isica. arXiv admin note: substantial text overlap with
arXiv:1211.120
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