78 research outputs found
The development of innovative processes in professional education
The article considers the problems of innovative processes in professional education. Innovation plays a major role in the determination of the leadership of the economic market in conditions of tough global competition, and allow you to achieve the goal of obtaining high dividends on the basis of new technologies and introduction of innovationsВ статье рассматривается проблематика инновационных процессов в профессиональном образовании. Инновации играют одну из важнейших ролей в определении лидерства на экономическом рынке в условиях жесткой мировой конкуренции, а также позволяют достигать цель получения мощных дивидендов на базе новых технологий и введения новшест
A novel and sensitive method for measuring very weak magnetic fields of DA white dwarfs: A search for a magnetic field at the 250 G level in 40 Eri B
Searches for magnetic fields in white dwarfs have clarified both the
frequency of occurrence and the global structure of the fields found down to
field strengths of the order of 500 kG. Below this level, the situation is
still very unclear. We are studying the weakest fields found in white dwarfs to
determine the frequency of such fields and their structure. We describe a very
sensitive new method of measuring such fields in DA (H-rich) white dwarfs, and
search for a field in the brightest such star, 40 Eri B. Our new method makes
use of the strongly enhanced polarisation signal in the sharp core of Halpha.
We find that with one-hour integrations with the high-resolution
spectropolarimeter ESPaDOnS on the 3.6-m CFHT, we can reach a standard error fo
the longitudinal field of about 85 G, the smallest error ever achieved for any
white dwarf. Nevertheless, we do not detect a magnetic field in this star.
Observations with ISIS at the WHT, and the Main Stellar Spectrograph at the
SAO, support the absence of a field at somewhat lower precision. The new method
is very efficient; it is shown that for suitable DA stars the integration time,
with ESPaDOnS on a 3.6-m telescope, to reach a 500 G standard error on a white
dwarf of V = 12.5, is about half an hour, about the same as the time required
on an ESO 8-m telescope with FORS using conventional low-resolution
spectropolarimetry.Comment: Accepted by Astronomy & Astrophysics on 20/06/201
The variation of the magnetic field of the Ap star HD~50169 over its 29 year rotation period
Context. The Ap stars that rotate extremely slowly, with periods of decades
to centuries, represent one of the keys to the understanding of the processes
leading to the differentiation of stellar rotation.
Aims. We characterise the variations of the magnetic field of the Ap star HD
50169 and derive constraints about its structure.
Methods. We combine published measurements of the mean longitudinal field
of HD 50169 with new determinations of this field moment from circular
spectropolarimetry obtained at the 6-m telescope BTA of the Special
Astrophysical Observatory of the Russian Academy of Sciences. For the mean
magnetic field modulus , literature data are complemented by the analysis of
ESO spectra, both newly acquired and from the archive. Radial velocities are
also obtained from these spectra.
Results. We present the first determination of the rotation period of HD
50169, Prot = (29.04+/-0.82) y. HD 50169 is currently the longest-period Ap
star for which magnetic field measurements have been obtained over more than a
full cycle. The variation curves of both and have a significant degree
of anharmonicity, and there is a definite phase shift between their respective
extrema. We confirm that HD 50169 is a wide spectroscopic binary, refine its
orbital elements, and suggest that the secondary is probably a dwarf star of
spectral type M.
Conclusions. The shapes and mutual phase shifts of the derived magnetic
variation curves unquestionably indicate that the magnetic field of HD 50169 is
not symmetric about an axis passing through its centre. Overall, HD 50169
appears similar to the bulk of the long-period Ap stars.Comment: 10 pages, 3 figures, accepted for publication in A&
Search for stellar spots in field blue horizontal-branch stars
Blue horizontal-branch stars are Population II objects which are burning
helium in their core and possess a hydrogen-burning shell and radiative
envelope. Because of their low rotational velocities, diffusion has been
predicted to work in their atmospheres. In many respects, blue
horizontal-branch stars closely resemble the magnetic chemically peculiar stars
of the upper main sequence, which show photometric variability caused by
abundance spots on their surfaces. These spots are thought to be caused by
diffusion and the presence of a stable magnetic field. However, the latter does
not seem to be axiomatic. We searched for rotationally induced variability in
30 well-established bright field blue horizontal-branch stars in the solar
neighbourhood and searched the literature for magnetic fields measurements of
our targets. We employed archival photometric time series data from the ASAS,
ASAS-SN, and SuperWASP surveys. The data were carefully reduced and processed,
and a time series analysis was applied using several different techniques. We
also synthesized existing photometric and spectroscopic data of magnetic
chemically peculiar stars in order to study possible different surface
characteristics producing lower amplitudes. In the accuracy limit of the
employed data, no significant variability signals were found in our sample
stars. The resulting upper limits for variability are given. We conclude that
either no stellar surface spots are present in field blue horizontal-branch
stars, or their characteristics (contrast, total area, and involved elements)
are not sufficient to produce amplitudes larger than a few millimagnitudes in
the optical wavelength region. New detailed models taking into account the
elemental abundance pattern of blue horizontal-branch stars are needed to
synthesize light curves for a comparison with our results.Comment: 6 pages, 2 figures, 2 tables, accepted for publication in Astronomy &
Astrophysic
HD 965: An extremely peculiar A star with an extremely long rotation period
Context. One of the keys to understanding the origin of the Ap stars and
their significance in the general context of stellar astrophysics is the
consideration of the most extreme properties displayed by some of them. In that
context, HD 965 is particularly interesting, as it combines some of the most
pronounced chemical peculiarities with one of the longest rotation periods
known.
Aims. We characterise the variations of the magnetic field of the Ap star HD
965 and derive constraints about its structure.
Methods. We combine published measurements of the mean longitudinal field
of HD 965 with new determinations of this field moment from circular
spectropolarimetry obtained at the 6-m telescope BTA of the Special
Astrophysical Observatory of the Russian Academy of Sciences. For the mean
magnetic field modulus , literature data are complemented by the analysis of
ESO archive spectra.
Results. We present the first determination of the rotation period of HD 965,
P = (16.5+/-0.5) y. HD 965 is only the third Ap star with a period longer than
10 years for which magnetic field measurements have been obtained over more
than a full cycle. The variation curve of is well approximated by a cosine
wave. does not show any significant variation. The observed behaviour of
these field moments is well represented by a simple model consisting of the
superposition of collinear dipole, quadrupole and octupole. The distribution of
neodymium over the surface of HD 965 is highly non-uniform. The element appears
concentrated around the magnetic poles, especially the negative one.
Conclusions. The shape of the longitudinal magnetic variation curve of HD 965
indicates that its magnetic field is essentially symmetric about an axis
passing through the centre of the star. Overall, as far as its magnetic field
is concerned, HD 965 appears similar to the bulk of the long-period Ap stars.Comment: 7 pages, 4 figures, accepted for publication in Astronomy &
Astrophysics. arXiv admin note: text overlap with arXiv:1902.0586
Magnetic stars with wide depressions in the continuum. 2. The silicon star with a complex field structure HD 27404
© 2017, Pleiades Publishing, Ltd. Observations of the chemically peculiar star HD 27404 with the 6-m SAO RAS telescope showed a strong magnetic field with the longitudinal field component varying in a complicated way in the range of −2.5 to 1 kG. Fundamental parameters of the star (T eff = 11 300 K, log g = 3.9) were estimated analyzing photometric indices in the Geneva and in the Stro¨ mgren–Crawford photometric systems. We detected weak radial velocity variations which can be due to the presence of a close star companion or chemical spots in the photosphere. Rapid estimation of the key chemical element abundance allows us to refer HD 27404 to a SiCr or Si+ chemically peculiar A0–B9 star
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