54 research outputs found
Accretion disk in the eclipsing binary AU Mon
We analyze the CoRoT and V-passband ground-based light curves of the
interacting close binary AU Mon, assuming that there is a geometrically and
optically thick accretion disk around the hotter and more massive star, as
inferred from photometric and spectroscopic characteristics of the binary. Our
model fits the observations very well and provides estimates for the orbital
elements and physical parameters of the components and of the accretion disk.Comment: Accepted for publication in MNRA
Long photometric cycle and disk evolution in the Lyrae type binary OGLE-BLG-ECL-157529
The subtype of hot algol semidetached binaries dubbed Double Periodic
Variables (DPVs) are characterized by a photometric cycle longer than the
orbital one, whose nature has been related to a magnetic dynamo in the donor
component controlling the mass transfer rate. We aim to understand the
morphologic changes observed in the light curve of OGLE-BLG-ECL-157529 that are
linked to the long cycle. In particular, we want to explain the changes in
relative depth of primary and secondary eclipses. We analyze and -band
OGLE photometric times series spanning 18.5 years and model the orbital light
curve. We find that OGLE-BLG-ECL-157529 is a new eclipsing Galactic DPV of
orbital period 24\fd8, and that its long cycle length decreases in amplitude
and length during the time baseline. We show that the changes of the orbital
light curve can be reproduced considering an accretion disk of variable
thickness and radius, surrounding the hottest stellar component. Our models
indicate changes in the temperatures of hot spot and bright spot during the
long cycle, and also in the position of the bright spot. This, along with the
changes in disk radius might indicate a variable mass transfer in this system.Comment: 8 pages, 14 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
Physical processes leading to surface inhomogeneities: the case of rotation
In this lecture I discuss the bulk surface heterogeneity of rotating stars,
namely gravity darkening. I especially detail the derivation of the omega-model
of Espinosa Lara & Rieutord (2011), which gives the gravity darkening in
early-type stars. I also discuss the problem of deriving gravity darkening in
stars owning a convective envelope and in those that are members of a binary
system.Comment: 23 pages, 11 figure, Lecture given to the school on the cartography
of the Sun and the stars (May 2014 in Besan\c{c}on), to appear in LNP, Neiner
and Rozelot edts V2: typos correcte
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IV. A 0.61 + 0.45 M_sun binary in a multiple system
We present the orbital and physical parameters of a newly discovered low-mass
detached eclipsing binary from the All-Sky Automated Survey (ASAS) database:
ASAS J011328-3821.1 A - a member of a visual binary system with the secondary
component separated by about 1.4 seconds of arc. The radial velocities were
calculated from the high-resolution spectra obtained with the 1.9-m
Radcliffe/GIRAFFE, 3.9-m AAT/UCLES and 3.0-m Shane/HamSpec
telescopes/spectrographs on the basis of the TODCOR technique and positions of
H_alpha emission lines. For the analysis we used V and I band photometry
obtained with the 1.0-m Elizabeth and robotic 0.41-m PROMPT telescopes,
supplemented with the publicly available ASAS light curve of the system.
We found that ASAS J011328-3821.1 A is composed of two late-type dwarfs
having masses of M_1 = 0.612 +/- 0.030 M_sun, M_2 = 0.445 +/- 0.019 M_sun and
radii of R_1 = 0.596 +/- 0.020 R_sun, R_2 = 0.445 +/- 0.024 R_sun, both show a
substantial level of activity, which manifests in strong H_alpha and H_beta
emission and the presence of cool spots. The influence of the third light on
the eclipsing pair properties was also evaluated and the photometric properties
of the component B were derived. Comparison with several popular stellar
evolution models shows that the system is on its main sequence evolution stage
and probably is more metal rich than the Sun. We also found several clues which
suggest that the component B itself is a binary composed of two nearly
identical ~0.5 M_sun stars.Comment: 12 pages, 7 figures, 7 tables, to appear in MNRA
The evolution stage and massive disc of the interacting binary V393 Scorpii
V393 Scorpii is a bright Galactic Double Periodic Variable showing a long
photometric cycle of approx. 253 days. We present new VIJK photometric time
series for V393 Scorpii along with the analysis of ASAS V-band photometry. We
disentangled all light curves into the orbital and long cycle components. The
ASAS V-band orbital light curve was modeled with two stellar components plus a
circumprimary optically thick disc assuming a semidetached configuration. We
present the results of this calculation, giving physical parameters for the
stars and the disc, along with general system dimensions. Our results are in
close agreement with those previously found by Mennickent et al. (2010) from IR
spectroscopy and the modeling of the spectral energy distribution. The
stability of the orbital light curve suggests that the stellar + disc
configuration remains stable during the long cycle. Therefore, the long cycle
should be produced by an additional variable and not-eclipsed emitting
structure. We discuss the evolutionary stage of the system finding the best
match with one of the evolutionary models of van Rensbergen et al. (2008).
According to these models, the system is found to be after an episode of fast
mass exchange that transferred 4 M_sun from the donor to the gainer in a period
of 400.000 years. We argue that a significant fraction of this mass has not
been accreted by the gainer but remains in an optically thick massive (about 2
M_sun) disc-like surrounding pseudo-photosphere whose luminosity is not driven
by viscosity but probably by reprocessed stellar radiation. Finally, we provide
the result of our search for Galactic Double Periodic Variables and briefly
discuss the outliers beta Lyr and RX Cas.Comment: 10 pages, 5 tables, 6 figures, accepted for publication in MNRAS main
journa
Physical parameters of close binaries QX Andromedae, RW Comae Berenices, MR Delphini, and BD +07{\circ} 3142
Aims. We analyze new multicolor light curves and recently published radial
velocity curves for close binaries QX And, RW Com, MR Del, and BD +07{\circ}
3142 to determine the physical parameters of the components. Methods. The light
curves are analyzed using a binary star model based on Roche geometry to fit
the photometric observations. Spectroscopic parameters, such as the mass ratios
and spectral types, were taken from recent spectroscopic studies of the systems
in question. Results. Our findings provide consistent and reliable sets of
stellar parameters for the four studied binary systems. Of particular interest
is the BD +07{\circ} 3142 system, since this is the first analysis of its light
curves. We find that it is an overcontact binary of W UMa type and W subtype,
and that each component has a large cool spot in the polar region. QX And is an
A subtype, and RW Com a W subtype W UMa binary, and in both systems we find a
bright spot in the neck region between the components. MR Del is a detached
binary with a complex light curve that we could model with two cool spots on
the hotter component.Comment: 10 pages, 4 figures. Accepted for publication by A&
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