641 research outputs found
Disentangling effective temperatures of individual eclipsing binary components by means of color-index constraining
Eclipsing binary stars are gratifying objects because of their unique
geometrical properties upon which all important physical parameters such as
masses, radii, temperatures, luminosities and distance may be obtained in
absolute scale. This poses strict demand on the model to be free of systematic
effects that would influence the results later used for calibrations, catalogs
and evolution theory. We present an objective scheme of obtaining individual
temperatures of both binary system components by means of color-index
constraining, with the only requirement that the observational data-set is
acquired in a standard photometric system. We show that for a modest case of
two similar main-sequence components the erroneous approach of assuming the
temperature of the primary star from the color index yields temperatures which
are systematically wrong by ~100K.Comment: 6 pages, 3 figures, 1 table; to appear in proceedings of the Close
Binaries in the 21st Century conference in Syros, Greec
Asiago eclipsing binaries program. III. V570 Per
The orbit and physical parameters of the previously unsolved SB2 EB V570 Per
are derived using high resolution Asiago Echelle spectroscopy and B, V
photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02
+/- 0.03, and reddening from interstellar NaI and KI absorption lines is E(B-V)
=0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350
+/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still
within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from
chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are
dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2}
=40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital
solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos
distance of 123 +/- 11 pc. The observed properties of V570 Per components are
compared to BaSTI models computed on purpose for exactly the observed masses
and varied chemical compositions. This system is interesting since both
components have their masses in the range where the efficiency of convective
core overshooting has to decrease with the total mass as a consequence of the
decreasing size of the convective core during the central H-burning stage. Our
numerical simulations show that, a small but not null overshooting is required,
with efficiencies lambda_{OV} =0.14 and 0.11 for the 1.449 and 1.350 Msun
components, respectively. This confirms the finding of Paper II on the similar
system V505 Per. At the approx 0.8 Gyr age of the system, the element diffusion
has reduced the surface metallicity of the models from the initial [M/H]=+0.17
to [M/H]=+0.02, in perfect agreement with the spectroscopically derived
[M/H]=+0.02 +/- 0.03 value.Comment: accepted by A&A. This revised upload to astro-ph correct a formatting
error generated by uncorrect A&A style fil
Influence of interstellar and atmospheric extinction on light curves of eclipsing binaries
Interstellar and atmospheric extinctions redden the observational photometric
data and they should be handled rigorously. This paper simulates the effect of
reddening for the modest case of two main sequence T1 = 6500K and T2 = 5500K
components of a detached eclipsing binary system. It is shown that simply
subtracting a constant from measured magnitudes (the approach often used in the
field of eclipsing binaries) to account for reddening should be avoided.
Simplified treatment of the reddening introduces systematics that reaches
\~0.01mag for the simulated case, but can be as high as ~0.2mag for e.g.
B8V--K4III systems. With rigorous treatment, it is possible to uniquely
determine the color excess value E(B-V) from multi-color photometric light
curves of eclipsing binaries.Comment: 6 pages, 9 figures, 1 table, Kopal's Binary Star Legacy conference
contribution (Litomysl 2004), to be published by Kluwer A&S
Evaluating GAIA performances on eclipsing binaries. II. Orbits and stellar parameters for V781 Tau, UV Leo and GK Dra
The orbits and physical parameters of three close, double-lined G0 eclipsing
binaries have been derived combining H_P, V_T, B_T photometry from the
Hipparcos/Tycho mission with 8480-8740 \AA ground-based spectroscopy. The setup
is mimicking the photometric and spectroscopic observations that should be
obtained by GAIA. The binaries considered here are all of G0 spectral type, but
each with its own complications: V781 Tau is an overcontact system with
components of unequal temperature, UV Leo shows occasional surface spots and GK
Dra contains a delta-Scuti variable. Such peculiarities will be common among
binaries to be discovered by GAIA. We find that the values of masses, radii and
temperatures for such stars can be derived with a 1-2% accuracy using the
adopted GAIA-like observing mode.Comment: accepted for publication in Astronomy and Astrophysics, contains 5
Tables and 3 Figures; correction of an important typ
Evaluating GAIA performances on eclipsing binaries. III. Orbits and stellar parameters for UW LMi, V432 Aur and CN Lyn
The orbits and physical parameters of three detached F and G-type eclipsing
binaries have been derived combining Hipparcos H(P) photometry with 8480-8740
Ang ground-based spectroscopy, simulating the photometric+spectroscopic
observations that the GAIA mission will obtain. Tycho B(T) and V(T) light
curves are too noisy to be modeled for the three targets, and only mean Tycho
colors are retained to constrain the temperature. No previous combined
photometric+spectroscopic solution exists in literature for any of the three
targets. Quite remarkably, CN Lyn turned out to be an equal masses F5 triple
system. Distances from the orbital solutions agree within the astrometric error
with the Hipparcos parallaxes.Comment: A&A, accepted in pres
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