46 research outputs found
Effect of Sulphur Fertilization on Yield and Quality of Wheat Grain
The influence of sulphur fertilization on plant dry weight, grain yield and quality of wheat grain (var. Mulan) was investigated. Wheat was grown in the small plot field experiments conducted in 2011–2012. At the beginning of tillering, the regenerative sulphur fertilization increased dry plant weight and sulphur concentration in dry matter by 28.1–43.2%. Sulphur application reduced the number of unproductive tillers and increased the number of ears per unit area by 10–70%. The highest grain yield was achieved after the application of solid fertilizers YaraBela SULFAN and fertilizer YaraVita Thiotrac applied in the late growing stages. Sulphur fertilization slightly improved the values of grain specific weight, protein content and Zeleny sedimentation volume, but the effect was not significant. The effect of fertilizer application significantly differed between the studied years
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: 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
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
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&
Period changes of the long-period cataclysmic binary EX Draconis
The cataclysmic variable star EX Dra is a relatively faint but frequently investigated eclipsing dwarf nova. In total 35 new eclipses were measured photometrically as part of our long-term monitoring of interesting eclipsing systems. Using published and new mid-eclipse times obtained between 2004 and 2011 we constructed the observed-minus-calculated diagram. The current data present 21 years of period modulation with a semi-amplitude of 2.5 min. The eclipse timings show significant deviations from the best sinusoidal fit, which indicates that this ephemeris is not a complete description of the data. The fractional period change is roughly ΔP/P = 3 × 10-6
Rapid apsidal motion in eccentric eclipsing binaries: OX Cassiopeia, PV Cassiopeia, and CO Lacertae
Aims.Double-lined eclipsing binaries are a traditional tool to test the
capability of
the stellar evolutionary models. If such binaries show apsidal motion,
it is also
possible to check, in addition to their absolute dimensions, some
aspects of their
internal structure. In order to perform this additional test,
we monitored the times of a minimum of three eclipsing binaries
with accurate absolute dimensions.
Methods.Approximately thirty new precise times of minimum light recorded with
CCD photometers were obtained for three early-type eccentric-orbit
eclipsing binaries OX Cas (P = 2\fd49, e = 0.041),
PV Cas (1\fd75, 0.032), and CO Lac (1\fd54, 0.029).
diagrams were analyzed by the Lacy's method using all reliable
timings found in the literature, and the elements of
apsidal motion were improved. On the other hand, stellar models
computed for
the precise observed masses of the three systems were used as
theoretical
tools to compare with the observed shift in the periastron position.
Results.We confirm very short periods of apsidal motion of approximately 38.2, 91.0, and 43.4 years for
OX Cas, PV Cas, and CO Lac, respectively. The relativistic
effects are negligible, being up to 6% of the total apsidal
motion rate in all systems. The corresponding observed apsidal motion
rates are in good agreement with the theoretical predictions, except
for the case of PV Cas, whose components seem to be more mass
concentrated than the models predict