This article discusses the process of active implementation of online learning modes based on digital technologies. Currently available theoretical postulates and recommended procedures of learning ...activities have been verified in practice during the course in History in Financial University under the Government of the Russian Federation. On this basis, certain experience of seminar classes has been accumulated (online conversations, discussions, presentations, webinars), this article is devoted to its analysis and generalization. The author has concluded that digital technologies diversify the classes and possess numerous tools to enhance motivation of students. The obtained results make it possible to state that application of several methods has been activated, such as brainstorming, mind games, metal mapping, interactive enquiries, testing and guessing games using learning platforms, for instance: Kahoot. Meanwhile, well balanced combination of the existing conventional learning modes and modern digital technologies makes it possible to provide even greater effect and result.
Gaia Early Data Release 3 Brown, A. G. A.; Prusti, T.; Eyer, L. ...
Astronomy and astrophysics (Berlin),
05/2021, Volume:
649
Journal Article, Web Resource
Peer reviewed
Open access
Context.
We present the early installment of the third
Gaia
data release,
Gaia
EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the ...list of radial velocities from
Gaia
DR2.
Aims.
A summary of the contents of
Gaia
EDR3 is presented, accompanied by a discussion on the differences with respect to
Gaia
DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of
Gaia
EDR3 results.
Methods.
The raw data collected with the
Gaia
instruments during the first 34 months of the mission have been processed by the
Gaia
Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to
Gaia
DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity.
Results. Gaia
EDR3 contains celestial positions and the apparent brightness in
G
for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (
G
BP
−
G
RP
) colour are also available. The passbands for
G
,
G
BP
, and
G
RP
are provided as part of the release. For ease of use, the 7 million radial velocities from
Gaia
DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of
Gaia
DR3. Finally,
Gaia
EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the
Gaia
-CRF3, which is based solely on extragalactic sources. The creation of the source list for
Gaia
EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for
Gaia
DR2, but it does feature new sources and there are some notable changes. The source list will not change for
Gaia
DR3.
Conclusions. Gaia
EDR3 represents a significant advance over
Gaia
DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30–40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for
G
,
G
BP
, and
G
RP
is valid over the entire magnitude and colour range, with no systematics above the 1% level
Gaia Data Release 2 Holl, B.; Audard, M.; Nienartowicz, K. ...
Astronomy and astrophysics (Berlin),
10/2018, Volume:
618
Journal Article
Peer reviewed
Open access
Context.
The
Gaia
Data Release 2 (DR2) contains more than half a million sources that are identified as variable stars.
Aims.
We summarise the processing and results of the identification of variable ...source candidates of RR Lyrae stars, Cepheids, long-period variables (LPVs), rotation modulation (BY Dra-type) stars,
δ
Scuti and SX Phoenicis stars, and short-timescale variables. In this release we aim to provide useful but not necessarily complete samples of candidates.
Methods.
The processed
Gaia
data consist of the
G
,
G
BP
, and
G
RP
photometry during the first 22 months of operations as well as positions and parallaxes. Various methods from classical statistics, data mining, and time-series analysis were applied and tailored to the specific properties of
Gaia
data, as were various visualisation tools to interpret the data.
Results.
The DR2 variability release contains 228 904 RR Lyrae stars, 11 438 Cepheids, 151 761 LPVs, 147 535 stars with rotation modulation, 8882
δ
Scuti and SX Phoenicis stars, and 3018 short-timescale variables. These results are distributed over a classification and various Specific Object Studies tables in the
Gaia
archive, along with the three-band time series and associated statistics for the underlying 550 737 unique sources. We estimate that about half of them are newly identified variables. The variability type completeness varies strongly as a function of sky position as a result of the non-uniform sky coverage and intermediate calibration level of these data. The probabilistic and automated nature of this work implies certain completeness and contamination rates that are quantified so that users can anticipate their effects. Thismeans that even well-known variable sources can be missed or misidentified in the published data.
Conclusions.
The DR2 variability release only represents a small subset of the processed data. Future releases will include more variable sources and data products; however, DR2 shows the (already) very high quality of the data and great promise for variability studies.
Context. Gravitational waves from black-hole (BH) merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on ...most stellar evolution models – and also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars. Aims. Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors. Methods. As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions. Results. The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70 ± 0.82 M ⊙ BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc. Conclusions. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way.
Abstract
We present results from the analysis of 2997 fundamental mode RR Lyrae variables located in the Small Magellanic Cloud (SMC). For these objects, near-infrared time series photometry from the ...VISTA survey of the Magellanic Clouds system (VMC) and visual light curves from the OGLE IV (Optical Gravitational Lensing Experiment IV) survey are available. In this study, the multi-epoch Ks-band VMC photometry was used for the first time to derive intensity-averaged magnitudes of the SMC RR Lyrae stars. We determined individual distances to the RR Lyrae stars from the near-infrared period–absolute magnitude–metallicity ($PM_{K_{\rm s}}Z$) relation, which has some advantages in comparison with the visual absolute magnitude–metallicity (MV–Fe/H) relation, such as a smaller dependence of the luminosity on interstellar extinction, evolutionary effects and metallicity. The distances we have obtained were used to study the three-dimensional structure of the SMC. The distribution of the SMC RR Lyrae stars is found to be ellipsoidal. The actual line-of-sight depth of the SMC is in the range 1–10 kpc, with an average depth of 4.3 ± 1.0 kpc. We found that RR Lyrae stars in the eastern part of the SMC are affected by interactions of the Magellanic Clouds. However, we do not see a clear bimodality observed for red clump stars, in the distribution of RR Lyrae stars.
We present results of the analysis of 70 RR Lyrae stars located in the bar of the Large Magellanic Cloud (LMC). Combining the spectroscopically determined metallicity of these stars from the ...literature with precise periods from the OGLE III catalog and multi-epoch K sub(s) photometry from the VISTA survey of the Magellanic Clouds system, we derive a new near-infrared period-luminosity-metallicity (PLKsZ) relation for RR Lyrae variables. In order to fit the relation we use a fitting method developed specifically for this study. The zero-point of the relation is estimated two different ways: by assuming the value of the distance to the LMC and by using Hubble Space Telescope parallaxes of five RR Lyrae stars in the Milky Way (MW). The difference in distance moduli derived by applying these two approaches is ~0.2 mag. To investigate this point further we derive the PLKsZ relation based on 23 MW RR Lyrae stars that had been analyzed in Baade-Wesselink studies. We compared the derived PLKsZ relations for RR Lyrae stars in the MW and LMC. Slopes and zero-points are different, but still consistent within the errors. The shallow slope of the metallicity term is confirmed by both LMC and MW variables. The astrometric space mission Gaia is expected to provide a huge contribution to the determination of the RR Lyrae PLKsZ relation; however, calculating an absolute magnitude from the trigonometric parallax of each star and fitting a PLKsZ relation directly to period and absolute magnitude leads to biased results. We present a tool to achieve an unbiased solution by modeling the data and inferring the slope and zero-point of the relation via statistical methods.
Context . Strongly lensed quasars are fundamental sources for cosmology. The Gaia space mission covers the entire sky with the unprecedented resolution of 0.18″ in the optical, making it an ideal ...instrument to search for gravitational lenses down to the limiting magnitude of 21. Nevertheless, the previous Gaia Data Releases are known to be incomplete for small angular separations such as those expected for most lenses. Aims . We present the Data Processing and Analysis Consortium GravLens pipeline, which was built to analyse all Gaia detections around quasars and to cluster them into sources, thus producing a catalogue of secondary sources around each quasar. We analysed the resulting catalogue to produce scores that indicate source configurations that are compatible with strongly lensed quasars. Methods . GravLens uses the DBSCAN unsupervised clustering algorithm to detect sources around quasars. The resulting catalogue of multiplets is then analysed with several methods to identify potential gravitational lenses. We developed and applied an outlier scoring method, a comparison between the average BP and RP spectra of the components, and we also used an extremely randomised tree algorithm. These methods produce scores to identify the most probable configurations and to establish a list of lens candidates. Results . We analysed the environment of 3 760 032 quasars. A total of 4 760 920 sources, including the quasars, were found within 6″ of the quasar positions. This list is given in the Gaia archive. In 87% of cases, the quasar remains a single source, and in 501 385 cases neighbouring sources were detected. We propose a list of 381 lensed candidates, of which we identified 49 as the most promising ones. Beyond these candidates, the associate tables in this Focused Product Release allow the entire community to explore the unique Gaia data for strong lensing studies further.
ABSTRACT
We present new luminosity–metallicity (LZ; $M_{V}\!-\!\rm Fe/H$ and $M_{G}\!-\!\rm Fe/H$) relations and, for the first time, empirical, Gaia three-band (G, GBP, GRP) ...period-Wesenheit-metallicity (PWZ) relations of RR Lyrae stars (RRLs) derived using a hierarchical Bayesian approach and new accurate parallaxes published for these variables in the Gaia Early Data Release 3 (EDR3). In a previous study, we obtained Bayesian hierarchically derived LZ relations from a sample of about four hundred Milky Way field RRLs with G-band light curves and trigonometric parallaxes published in the Gaia Data Release 2 (DR2), using V mean magnitudes, metallicities, absorptions, and pulsation periods available in the literature. We now extend that study in two directions. First, we update our previous results using trigonometric parallaxes from Gaia EDR3 and incorporate the Bayesian analysis of a first empirical PWZ relation derived using those field RRLs with G, GBP and GRP time-series photometry available in Gaia DR2. Secondly, we use Bayesian inference to derive LZ relations and empirical PW Gaia three-band relations from 385 RRLs belonging to 15 Milky Way globular clusters (GC) with literature-compiled spectroscopic metallicities ranging from −0.36 to −2.39 dex and prior distances extending from 2.2 to 41.2 kpc. From the samples of RRLs analysed in this paper we infer a mean Gaia EDR3 zero-point offset of −0.028 mas with median values ranging from −0.033 (LZ and PWZ models for field stars) to −0.024 mas (LZ model in the V band for GC RRLs).
Gaia Data Release 2 Clementini, G.; Ripepi, V.; Molinaro, R. ...
Astronomy and astrophysics (Berlin),
02/2019, Volume:
622
Journal Article
Peer reviewed
Open access
Context.
The
Gaia
second Data Release (DR2) presents a first mapping of full-sky RR Lyrae stars and Cepheids observed by the spacecraft during the initial 22 months of science operations.
Aims.
The ...Specific Objects Study (SOS) pipeline, developed to validate and fully characterise Cepheids and RR Lyrae stars (SOS Cep&RRL) observed by
Gaia
, has been presented in the documentation and papers accompanying the
Gaia
first Data Release. Here we describe how the SOS pipeline was modified to allow for processing the
Gaia
multi-band (
G
,
G
BP
, and
G
RP
) time-series photometry of all-sky candidate variables and produce specific results for confirmed RR Lyrae stars and Cepheids that are published in the DR2 catalogue.
Methods.
The SOS Cep&RRL processing uses tools such as the period–amplitude and the period–luminosity relations in the
G
band. For the analysis of the
Gaia
DR2 candidates we also used tools based on the
G
BP
and
G
RP
photometry, such as the period–Wesenheit relation in (
G
,
G
RP
).
Results.
Multi-band time-series photometry and characterisation by the SOS Cep&RRL pipeline are published in
Gaia
DR2 for 150 359 such variables (9575 classified as Cepheids and 140 784 as RR Lyrae stars) distributed throughout the sky. The sample includes variables in 87 globular clusters and 14 dwarf galaxies (the Magellanic Clouds, 5 classical and 7 ultra-faint dwarfs). To the best of our knowledge, as of 25 April 2018, the variability of 50 570 of these sources (350 Cepheids and 50 220 RR Lyrae stars) has not been reported before in the literature, therefore they are likely new discoveries by
Gaia
. An estimate of the interstellar absorption is published for 54 272 fundamental-mode RR Lyrae stars from a relation based on the
G
-band amplitude and the pulsation period. Metallicities derived from the Fourier parameters of the light curves are also released for 64 932 RR Lyrae stars and 3738 fundamental-mode classical Cepheids with periods shorter than 6.3 days.
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