49 research outputs found
Teaching Management at Technical Universities Business Reality in the Academic Environment
Students of technical universities often do not understand why their studies should include learning management skills (in addition to the study of economics). However, not only the experience of graduates but also the requirements of their future employers show that education in the field of the management should provide training, skills and practical testing. It is only a matter of time before graduates of technical university take up leading positions or become part of a team working on some complicated technical problem. A classical technical education is no longer sufficient and, aboveall, it is employees with knowledge of economics and with managerial skills, specifically soft skills that come to the fore. It is evident from ample experience that people’s individual dispositions play a role in learning soft skills, but many of these skills can also be acquired by progressive training. The question is which form of teaching to choose to enable necessary skills to be learned, without at the same discouraging students by offering them potentially unattractive courses. These are the issues that will be treated in this paper
Teaching Management at Technical Universities, Business Reality in the Academic Environment
Students of technical universities often do not understand why their studies should include learning management skills (in addition to the study of economics). However, not only the experience of graduates but also the requirements of their future employers show that education in the field of the management should provide training, skills and practical testing. It is only a matter of time before graduates of technical university take up leading positions or become part of a team working on some complicated technical problem. A classical technical education is no longer sufficient and, aboveall, it is employees with knowledge of economics and with managerial skills, specifically soft skills that come to the fore. It is evident from ample experience that people’s individual dispositions play a role in learning soft skills, but many of these skills can also be acquired by progressive training. The question is which form of teaching to choose to enable necessary skills to be learned, without at the same discouraging students by offering them potentially unattractive courses. These are the issues that will be treated in this paper
Absolute dimensions and apsidal motion of the eclipsing binaries V889 Aquilae and V402 Lacertae
Context. Double-lined eclipsing binaries allow the direct determination of masses and radii, which are key for testing stellar models. With the launch of the TESS mission, many well-known eclipsing binaries have been observed at higher photometric precision, permitting the improvement of the absolute dimension determinations. Aims. Using TESS data and newly obtained spectroscopic observations, we aim to determine the masses and radii of the eccentric eclipsing binary systems V889 Aql and V402 Lac, together with their apsidal motion parameters. Methods. We simultaneously modelled radial velocity curves and times of eclipse for each target to precisely determine the orbital parameters of the systems, which we used to analyse the light curves and then obtain their absolute dimensions. We compared the obtained values with those predicted by theoretical models. Results. We determined masses and radii of the components of both systems with relative uncertainties lower than 2%. V889 Aql is composed of two stars with masses 2:17±0:02 M⊙ and 2:13±0:01 M⊙ and radii 1:87±0:04 R⊙ and 1:85±0:04 R⊙.We find conclusive evidence of the presence of a third body orbiting V889 Aql with a period of 67 yr. Based on the detected third light and the absence of signal in the spectra, we suggest that this third body could in turn be a binary composed of two ±1.4 M⊙ stars. V402 Lac is composed of two stars with masses 2:80 ± 0:05 M⊙ and 2:78 ± 0:05 M⊙ and radii 2:38 ± 0:03 R⊙ and 2:36 ± 0:03 R⊙. The times of minimum light are compatible with the presence of a third body for this system too, although its period is not yet fully sampled. In both cases we have found a good agreement between the observed apsidal motion rates and the model predictions
The CARMENES search for exoplanets around M dwarfs: Nine new double-line spectroscopic binary stars
Context. The CARMENES spectrograph is surveying ~300 M dwarf stars in search
for exoplanets. Among the target stars, spectroscopic binary systems have been
discovered, which can be used to measure fundamental properties of stars. Aims.
Using spectroscopic observations, we determine the orbital and physical
properties of nine new double-line spectroscopic binary systems by analysing
their radial velocity curves. Methods. We use two-dimensional cross-correlation
techniques to derive the radial velocities of the targets, which are then
employed to determine the orbital properties. Photometric data from the
literature are also analysed to search for possible eclipses and to measure
stellar variability, which can yield rotation periods. Results. Out of the 342
stars selected for the CARMENES survey, 9 have been found to be double-line
spectroscopic binaries, with periods ranging from 1.13 to ~8000 days and orbits
with eccentricities up to 0.54. We provide empirical orbital properties and
minimum masses for the sample of spectroscopic binaries. Absolute masses are
also estimated from mass-luminosity calibrations, ranging between ~0.1 and ~0.6
Msol . Conclusions. These new binary systems increase the number of double-line
M dwarf binary systems with known orbital parameters by 15%, and they have
lower mass ratios on average.Comment: Accepted for publication in A&A. 17 pages, 4 figure
A Machine Learning approach for correcting radial velocities using physical observables
Precision radial velocity (RV) measurements continue to be a key tool to
detect and characterise extrasolar planets. While instrumental precision keeps
improving, stellar activity remains a barrier to obtain reliable measurements
below 1-2 m/s accuracy. Using simulations and real data, we investigate the
capabilities of a Deep Neural Network approach to produce activity free Doppler
measurements of stars. As case studies we use observations of two known stars
(Eps Eridani and AUMicroscopii), both with clear signals of activity induced RV
variability. Synthetic data using the starsim code are generated for the
observables (inputs) and the resulting RV signal (labels), and used to train a
Deep Neural Network algorithm. We identify an architecture consisting of
convolutional and fully connected layers that is adequate to the task. The
indices investigated are mean line-profile parameters (width, bisector,
contrast) and multi-band photometry. We demonstrate that the RV-independent
approach can drastically reduce spurious Doppler variability from known
physical effects such as spots, rotation and convective blueshift. We identify
the combinations of activity indices with most predictive power. When applied
to real observations, we observe a good match of the correction with the
observed variability, but we also find that the noise reduction is not as good
as in the simulations, probably due to the lack of detail in the simulated
physics. We demonstrate that a model-driven machine learning approach is
sufficient to clean Doppler signals from activity induced variability for well
known physical effects. There are dozens of known activity related observables
whose inversion power remains unexplored indicating that the use of additional
indicators, more complete models, and more observations with optimised sampling
strategies can lead to significant improvements in our detrending capabilities
The CARMENES search for exoplanets around M dwarfs: Convective shift and starspot constraints from chromatic radial velocities
Context. Variability caused by stellar activity represents a challenge to the
discovery and characterization of terrestrial exoplanets and complicates the
interpretation of atmospheric planetary signals.
Aims. We aim to use a detailed modeling tool to reproduce the effect of
active regions on radial velocity measurements, which aids the identification
of the key parameters that have an impact on the induced variability.
Methods. We analyzed the effect of stellar activity on radial velocities as a
function of wavelength by simulating the impact of the properties of spots,
shifts induced by convective motions, and rotation. We focused our modeling
effort on the active star YZ CMi (GJ 285), which was photometrically and
spectroscopically monitored with CARMENES and the Telescopi Joan Or\'o.
Results. We demonstrate that radial velocity curves at different wavelengths
yield determinations of key properties of active regions, including spot
filling factor, temperature contrast, and location, thus solving the degeneracy
between them. Most notably, our model is also sensitive to convective motions.
Results indicate a reduced convective shift for M dwarfs when compared to
solar-type stars (in agreement with theoretical extrapolations) and points to a
small global convective redshift instead of blueshift.
Conclusions. Using a novel approach based on simultaneous chromatic radial
velocities and light curves, we can set strong constraints on stellar activity,
including an elusive parameter such as the net convective motion effect.Comment: A&A, in pres
Спостереження як метод державного фінансового контролю за сплатою податків суб'єктами малого підприємництва
У статті проаналізовано особливості державного контролю за діяльністю суб’єктів малого підприємництва. Наведено авторське визначення методу спостереження в державному фінансовому контролі за сплатою податків та обґрунтовано доцільність його застосування в перспективі.
(The features of state control over the activities of small businesses are analyzed. The author’s definition of the method of monitoring in the state financial control over tax payments is given, and the expedience for its use in the prospects is grounded.
The CARMENES search for exoplanets around M dwarfs, Wolf 1069 b: Earth-mass planet in the habitable zone of a nearby, very low-mass star
We present the discovery of an Earth-mass planet () on a 15.6d orbit of a relatively nearby (9.6pc)
and low-mass () M5.0V star, Wolf 1069. Sitting at a
separation of au away from the host star puts Wolf 1069b in
the habitable zone (HZ), receiving an incident flux of
. The planetary signal was detected using
telluric-corrected radial-velocity (RV) data from the CARMENES spectrograph,
amounting to a total of 262 spectroscopic observations covering almost four
years. There are additional long-period signals in the RVs, one of which we
attribute to the stellar rotation period. This is possible thanks to our
photometric analysis including new, well-sampled monitoring campaigns undergone
with the OSN and TJO facilities that supplement archival photometry (i.e., from
MEarth and SuperWASP), and this yielded an updated rotational period range of
d, with a likely value at d. The stellar
activity indicators provided by the CARMENES spectra likewise demonstrate
evidence for the slow rotation period, though not as accurately due to possible
factors such as signal aliasing or spot evolution. Our detectability limits
indicate that additional planets more massive than one Earth mass with orbital
periods of less than 10 days can be ruled out, suggesting that perhaps Wolf
1069 b had a violent formation history. This planet is also the 6th closest
Earth-mass planet situated in the conservative HZ, after Proxima Centauri b, GJ
1061d, Teegarden's Star c, and GJ 1002 b and c. Despite not transiting, Wolf
1069b is nonetheless a very promising target for future three-dimensional
climate models to investigate various habitability cases as well as for
sub-ms RV campaigns to search for potential inner sub-Earth-mass planets
in order to test planet formation theories.Comment: 26 pages, 15 figure
The CARMENES search for exoplanets around M dwarfs
Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets.
Aims: We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey.
Methods: The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained.
Results: We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online.
Conclusions: CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres
The CARMENES search for exoplanets around M dwarfs : stable radial-velocity variations at the rotation period of AD Leonis: A test case study of current limitations to treating stellar activity
Context. A challenge with radial-velocity (RV) data is disentangling the origin of signals either due to a planetary companion or to stellar activity. In fact, the existence of a planetary companion has been proposed, as well as contested, around the relatively bright, nearby M3.0 V star AD Leo at the same period as the stellar rotation of 2.23 days.
Aims. We further investigate the nature of this signal. We introduce new CARMENES optical and near-IR RV data and an analysis in combination with archival data taken by HIRES and HARPS, along with more recent data from HARPS-N, GIANO-B, and HPF. Additionally, we address the confusion concerning the binarity of AD Leo.
Methods. We consider possible correlations between the RVs and various stellar activity indicators accessible with CARMENES. We additionally applied models within a Bayesian framework to determine whether a Keplerian model, a red-noise quasi-periodic model using a Gaussian process, or a mixed model would explain the observed data best. We also exclusively focus on spectral lines potentially associated with stellar activity.
Results. The CARMENES RV data agree with the previously reported periodicity of 2.23 days, correlate with some activity indicators, and exhibit chromaticity. However, when considering the entire RV data set, we find that a mixed model composed of a stable and a variable component performs best. Moreover, when recomputing the RVs using only spectral lines insensitive to activity, there appears to be some residual power at the period of interest. We therefore conclude that it is not possible to determinedly prove that there is no planet orbiting in synchronization with the stellar rotation given our data, current tools, machinery, and knowledge of how stellar activity affects RVs. We do rule out planets more massive than 27 M⊕ (=0.084 MJup). Likewise, we exclude any binary companion around AD Leo with M sin i greater than 3–6 MJup on orbital periods <14 yr