52 research outputs found
Improved model of the triple system V746 Cas that has a bipolar magnetic field associated with the tertiary
V746 Cas is known to be a triple system composed of a close binary with an
alternatively reported period of either 25.4d or 27.8d and a third component in
a 62000d orbit. The object was also reported to exhibit multiperiodic light
variations with periods from 0.83d to 2.50d, on the basis of which it was
classified as a slowly pulsating B star. Interest in further investigation of
this system was raised by the detection of a variable magnetic field. Analysing
spectra from four instruments, earlier published radial velocities, and several
sets of photometric observations, we arrived at the following conclusions: (1)
The optical spectrum is dominated by the lines of the B-type primary
(Teff1~16500(100) K), contributing 70% of the light in the optical region, and
a slightly cooler B tertiary (Teff3~13620(150) K). The lines of the low-mass
secondary are below our detection threshold; we estimate that it could be a
normal A or F star. (2) We resolved the ambiguity in the value of the inner
binary period and arrived at a linear ephemeris of T_super.conj.=HJD
2443838.78(81)+25.41569(42)xE. (3) The intensity of the magnetic field
undergoes a~sinusoidal variation in phase with one of the known photometric
periods, namely 2.503867(19)d, which we identify with the rotational period of
the tertiary. (4) The second photometric 1.0649524(40)d period is identified
with the rotational period of the B-type primary, but this interpretation is
much less certain and needs further verification. (5) If our interpretation of
photometric periods is confirmed, the classification of the object as a slowly
pulsating B star should be revised. (6) Applying an N-body model to different
types of available observational data, we constrain the orbital inclination of
the inner orbit to ~60 deg to 85 deg even in the absence of eclipses, and
estimate the probable properties of the triple system and its components.Comment: Accepted for publication in Astronomy and Astrophysic
Properties and nature of Be stars 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries
Reliable determination of the basic physical properties of hot emission-line
binaries with Roche-lobe filling secondaries is important for developing the
theory of mass exchange in binaries. It is a very hard task, however, which is
complicated by the presence of circumstellar matter in these systems. So far,
only a small number of systems with accurate values of component masses, radii,
and other properties are known. Here, we report the first detailed study of a
new representative of this class of binaries, BR CMi, based on the analysis of
radial velocities and multichannel photometry from several observatories, and
compare its physical properties with those for other well-studied systems. BR
CMi is an ellipsoidal variable seen under an intermediate orbital inclination
of ~51 degrees, and it has an orbital period of 12.919059(15) d and a circular
orbit. We used the disentangled component spectra to estimate the effective
temperatures 9500(200) K and 4655(50) K by comparing them with model spectra.
They correspond to spectral types B9.5e and G8III. We also used the
disentangled spectra of both binary components as templates for the 2-D
cross-correlation to obtain accurate RVs and a reliable orbital solution. Some
evidence of a secular period increase at a rate of 1.1+/-0.5 s per year was
found. This, together with a very low mass ratio of 0.06 and a normal mass and
radius of the mass gaining component, indicates that BR CMi is in a slow phase
of the mass exchange after the mass-ratio reversal. It thus belongs to a still
poorly populated subgroup of Be stars for which the origin of Balmer emission
lines is safely explained as a consequence of mass transfer between the binary
components.Comment: 17 pages, 5 figures, accepted for publication in Astronomy and
Astrophysics. appears in Astronomy and Astrophysics 201
Properties and nature of Be stars 31. The binary nature, light variability, physical elements, and emission-line changes of HD~81357
Reliable determination of the basic physical properties of hot emission-line
binaries with Roche-lobe filling secondaries is important for developing the
theory of mass exchange in binaries. It is not easy, however, due to the
presence of circumstellar matter. Here, we report the first detailed
investigation of a new representative of this class of binaries, HD~81357,
based on the analysis of spectra and photometry from several observatories.
HD~81357 was found to be a double-lined spectroscopic binary and an ellipsoidal
variable seen under an intermediate orbital inclination of
, having an orbital period of 33\fd77445(41) and a~circular
orbit. From an automated comparison of the observed and synthetic spectra, we
estimate the component's effective temperatures to be 12930(540)~K and
4260(24)~K. The combined light-curve and orbital solutions, also constrained by
a very accurate Gaia Data Release 2 parallax, give the following values of the
basic physical properties: masses and ~\Mnom, radii
and 13.97\pm0.05~\Rnom, and a~mass ratio 10.0\pm0.5$.
Evolutionary modelling of the system including the phase of mass transfer
between the components indicated that HD~81357 is a~system observed in the
final slow phase of the mass exchange after the mass-ratio reversal. Contrary
to what has been seen for similar binaries like AU~Mon, no cyclic light
variations were found on a~time scale an~order of magnitude longer than the
orbital period.
243,1 15%Comment: 16 pages, 9 figures; accepted for publication in Astronomy and
Astrophysic
Properties and nature of Be stars: 27. Orbital and recent long-term variations of the Pleiades Be star Pleione = BU Tauri
Radial-velocity variations of the H-alpha emission measured on the steep
wings of the H-alpha line, prewhitened for the long-time changes, vary
periodically with a period of (218.025 +/- 0.022)d, confirming the suspected
binary nature of the bright Be star Pleione, a member of the Pleiades cluster.
The orbit seems to have a high eccentricity over 0.7, but we also briefly
discuss the possibility that the true orbit is circular and that the
eccentricity is spurious owing to the phase-dependent effects of the
circumstellar matter. The projected angular separation of the spectroscopic
orbit is large enough to allow the detection of the binary with large optical
interferometers, provided the magnitude difference primary - secondary is not
too large. Since our data cover the onset of a new shell phase up to
development of a metallic shell spectrum, we also briefly discuss the recent
long-term changes. We confirm the formation of a new envelope, coexisting with
the previous one, at the onset of the new shell phase. We find that the full
width at half maximum of the H-alpha profile has been decreasing with time for
both envelopes. In this connection, we briefly discuss Hirata's hypothesis of
precessing gaseous disk and possible alternative scenarios of the observed
long-term changes
Effect of nitrogen and sulphur fertilization on the quality of barley protein
A small-plot field experiment was set up during 2011, 2012 and 2013 to test the effect of nitrogen (N) fertilizers and nitrogen fertilizers combined with sulphur (S) in the nutrition of spring barley cv. Bojos. The following parameters were studied, the effect of fertilization on grain yield, specific weight, percentage of the grain retained on a 2.8 mm and 2.5 mm sieve, the content of starch and proteins, and the percentage of protein fractions. Also the influence of weather conditions on the studied parameters was evaluated. Starch content and specific weight of grain were not influenced by the fertilizer applied. Grain yield was rising until the overall dosage reached 50 kg N/ha and 21 kg S/ha while any higher rate of fertilizer reduced the yield. The percentage of A- and B-hordeins increased and the content of C- and D-hordeins reduced as the fertilizer rate increased. A significant effect of weather on the monitored parameters as well as on the percentage of protein fractions was demonstrated. The results enabled a conclusion that there is no improvement in technological quality of barley grain once the optimal rate of fertilizer has been reached. The optimal rate is influenced by weather conditions during the growing season. © 2015 Institute of Agricultural and Food Information. All rights reserved.Internal Grant Agency of Faculty of Agronomy Mendel University in Brno [IP 18/2014
The field high-amplitude SX Phe variable BL Cam: results from a multisite photometric campaign. II. Evidence of a binary - possibly triple - system
Short-period high-amplitude pulsating stars of Population I ( Sct
stars) and II (SX Phe variables) exist in the lower part of the classical
(Cepheid) instability strip. Most of them have very simple pulsational
behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is
a unique object among them, being an extreme metal-deficient field
high-amplitude SX Phe variable with a large number of frequencies. Based on a
frequency analysis, a pulsational interpretation was previously given. aims
heading (mandatory) We attempt to interpret the long-term behaviour of the
residuals that were not taken into account in the previous Observed-Calculated
(O-C) short-term analyses. methods heading (mandatory) An investigation of the
O-C times has been carried out, using a data set based on the previous
published times of light maxima, largely enriched by those obtained during an
intensive multisite photometric campaign of BL Cam lasting several months.
results heading (mandatory) In addition to a positive (161 3) x 10
yr secular relative increase in the main pulsation period of BL Cam, we
detected in the O-C data short- (144.2 d) and long-term ( 3400 d)
variations, both incompatible with a scenario of stellar evolution. conclusions
heading (mandatory) Interpreted as a light travel-time effect, the short-term
O-C variation is indicative of a massive stellar component (0.46 to 1
M_{\sun}) with a short period orbit (144.2 d), within a distance of 0.7 AU
from the primary. More observations are needed to confirm the long-term O-C
variations: if they were also to be caused by a light travel-time effect, they
could be interpreted in terms of a third component, in this case probably a
brown dwarf star ( 0.03 \ M_{\sun}), orbiting in 3400 d at a
distance of 4.5 AU from the primary.Comment: 7 pages, 5 figures, accepted for publication in A&
Clasts of Variscan high-grade rocks within Upper Viséan conglomerates - constraints on exhumation history from petrology and U-Pb chronology
Migration of risk elements within the floodplain of the Litavka River, the Czech Republic
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