Virtual Observatory Tools Research Articles

Confirmation and characterization of neglected WDS systems using Gaia data release 3 and the virtual observatory

AbstractThe aim of this article is making use of the Gaia DR3 catalogue and virtual observatory tools, to confirm and characterize 428 binary and multiple stellar systems classified as neglected (only one observation) in the Washington Double Star Catalogue (WDS). The components of the stellar systems have the same parallax and proper motion (within the errors) and are separated by less than 50,000 AU, which minimizes the number of by‐chance counterparts. Effective temperatures calculated using VOSA were used to estimate stellar masses. Binding energies were calculated for 42 binary systems confirming they are physical pairs. Also we found 75 pairs with F/G‐ M spectral types, which are very interesting to improve the determination of the metallicity of the M star from the higher mass component.

M dwarf stars in the b294 field from the VISTA Variables in the Vía Láctea (VVV)

ABSTRACT M dwarf stars are the dominant stellar population in the Milky Way, and they are important for a wide variety of astrophysical topics. The Gaia mission has delivered a superb collection of data, nevertheless, ground-based photometric surveys are still needed to study faint objects. Therefore, the present work aims to identify and characterize M dwarf stars in the direction of the Galactic bulge using photometric data and with the help of Virtual Observatory tools. Using parallax measurements and proper motions from Gaia Data Release 3, in addition to different colour-cuts based on VISTA filters, we identify and characterize 7 925 M dwarf stars in the b294 field from the Vista Variables in the Vía Láctea (VVV) survey. We performed a spectral energy distribution fitting to obtain the effective temperature for all objects using photometric information available at Virtual Observatory archives. The objects in our sample have temperatures varying from 2800–3900 K. We also search for periodic signals in VVV light curves with up to 300 epochs, approximately. As a secondary outcome, we obtain periods for 82 M dwarfs by applying two methods: the Lomb–Scargle and Phase Dispersion Minimization methods, independently. These objects, with periods ranging from 0.14–34 d, are good candidates for future ground-based follow up. Our sample has increased significantly the number of known M dwarfs in the direction of the Galactic bulge and within 500 pc, showing the importance of ground-based photometric surveys in the near-infrared.

Identification of new hot subdwarf binary systems by means of Virtual Observatory tools

ABSTRACT The estimation of the binary fraction of hot subdwarfs is key to shed light on the different evolution scenarios proposed to explain the loss of the hydrogen envelope during the red giant branch phase. In this paper, we analyse the spectral energy distribution of the hot subdwarfs included in a recent and comprehensive catalogue with the aim of identifying companions. Our methodology shows a performance superior to the photometric criteria used in that study, identifying 202 objects wrongly classified as binaries according to their spectral energy distributions, and finding 269 new binaries. Out of an initial sample of 3186 objects, we classified 2469 as single and 615 as binary hot subdwarfs. The rest of the objects (102) were not classified because of their inadequate spectral energy distribution fitting due, in turn, to poor quality photometry. Effective temperatures, luminosities, and radii were computed for 192 singles and 42 binaries. They, in particular the binary sample, constitute an excellent data set to further perform a more careful spectroscopic analysis that could provide detailed values for the chemical composition, masses, ages, rotation properties, or reflection effects for the shortest period systems. The results obtained in this paper will be used as a reference for a forthcoming work where we aim to generalize binary and single hot subdwarf classification using Artificial Intelligence-based techniques.

The data center construction of the Xinjiang Astronomical Observatory based on virtual observatory standards

As part of the Chinese National Astronomical Data Center, the Xinjiang Astronomical Observatory Data Center is built based on the virtual observatory standards. The data resources mainly include the pulsar dataset, the molecular spectral lines dataset, the intra-day variability source dataset generated by the Nanshan 25 m radio telescope, and the Nanshan 1 m wide-field telescope dataset, published through about a dozen data services, including a Table Access Protocol (TAP) endpoint. Some of these data services are registered with the International Virtual Observatory Alliance. Users can use standard virtual observatory tools, browsers, and scripts to retrieve all the metadata information in the data center and to realize simple data analysis, processing, and visualization operations.

Въвеждане на ученици и студенти в практическата астрономия посредством инструменти на Виртуалната обсерватория

Large-scale astronomical surveys from the last decades have turned the usage of catalogs and archival data into one of the primary skills of contemporary observational astronomers. Virtual observatory tools give high-school and university students the opportunity to conduct astronomical research by themselves, using freely available observational data. For this purpose, they need basic theoretical knowledge in astronomy. The current paper includes a review of this theoretical knowledge as well as a review of Virtual observatory tools suitable for students. Results obtained by students using VO tools at the Beli Brezi Summer School in Astronomy and Astrophysics are presented as well.

Wide companions to M and L subdwarfs withGaiaand the Virtual Observatory

Aims.The aim of the project is to identify wide common proper motion companions to a sample of spectroscopically confirmed M and L metal-poor dwarfs (also known as subdwarfs) to investigate the impact of metallicity on the binary fraction of low-mass metal-poor binaries and to improve the determination of their metallicity from the higher-mass binary.Methods.We made use of Virtual Observatory tools and large-scale public surveys to look inGaiafor common proper motion companions to a well-defined sample of ultracool subdwarfs with spectral types later than M5 and metallicities below or equal to −0.5 dex. We collected low-resolution optical spectroscopy for our best system, which is a binary composed of one sdM1.5 subdwarf and one sdM5.5 subdwarf located at ∼1360 au, and for another two likely systems separated by more than 115 000 au.Results.We confirm one wide companion to an M subdwarf, and infer a multiplicity for M subdwarfs (sdMs) of 1.0−1.0+2.0% for projected physical separations of up to 743 000 au. We also find four M–L systems, three of which are new detections. No colder companion was identified in any of the 219 M and L subdwarfs of the sample, mainly because of limitations on the detection of faint sources withGaia. We infer a frequency of wide systems for sdM5–9.5 of 0.60−0.60+1.17% for projected physical separations larger than 1 360 au (up to 142 400 au). This study shows a multiplicity rate of 1.0−1.0+2.0% in sdMs, and 1.9−1.9+3.7% in extreme M subdwarfs. We did not find any companion for the ultra M subdwarfs of our sample, establishing an upper limit of 5.3% on binarity for these objects.

HiSS-Cube: A scalable framework for Hierarchical Semi-Sparse Cubes preserving uncertainties

A wide variety of approaches are available for big data cube visualization and analysis. However, few exploit the power of array databases and none preserve the scientific uncertainties in measurements when constructing lower resolutions. In machine learning applications, we often need to rapidly search data for regions of interest and then focus on these areas, but without having to retrain the model every time we change the resolution. However, the reliable verification of these areas also requires details of the accuracy of the measured values. In this study, we developed a new software infrastructure called Hierarchical Semi-Sparse Cube (HiSS-Cube) based on Hierarchical Data Format version 5. HiSS-Cube enables visualization and machine learning using combined heterogeneous data and it was designed to be scalable for big data. HiSS-Cube allows data from multiple domains (imaging, spectral, and time-series data) to be combined and the construction of a multi-resolution semi-sparse data cube that preserves the uncertainties of scientific measurement at all resolutions. The functionality of HiSS-Cube was verified based on a subset of the Sloan Digital Sky Survey Stripe 82 survey. We compared the times and volumes for visualizations and machine learning data exported to HiSS-Cube and the original format (FITS). Using these data, we demonstrated that HiSS-Cube is faster by several orders of magnitude. HiSS-Cube supports export to the VOTable format and it is compatible with common Virtual Observatory tools. The source code for our prototype HiSS-Cube is available from GitHub and the data are available from Zenodo.

Ultracool dwarfs in deep extragalactic surveys using the virtual observatory: ALHAMBRA and COSMOS

ABSTRACT Ultracool dwarfs (UCDs) encompass a wide variety of compact stellar-like objects with spectra classified as late-M, L, T, and Y. Most of them have been discovered using wide-field imaging surveys. The Virtual Observatory (VO) has proven to be of great utility to efficiently exploit these astronomical resources. We aim to validate a VO methodology designed to discover and characterize UCDs in deep extragalactic surveys like Advance Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) and Cosmological Evolution Survey (COSMOS). Three complimentary searches based on parallaxes, proper motions and colours, respectively, were carried out. A total of 897 candidate UCDs were found, with only 16 previously reported in SIMBAD. Most of the new UCDs reported here are likely late-M and L dwarfs because of the limitations imposed by the utilization of optical (Gaia DR2 and r-band) data. We complement ALHAMBRA and COSMOS photometry with other catalogues in the optical and infrared using VOSA, a VO tool that estimates effective temperatures from the spectral energy distribution fitting to collections of theoretical models. The agreement between the number of UCDs found in the COSMOS field and theoretical estimations together with the low false-negative rate (known UCDs not discovered in our search) validates the methodology proposed in this work, which will be used in the forthcoming wide and deep surveys provided by the Euclid space mission. Simulations of Euclid number counts for UCDs detectable in different photometric passbands are presented for a wide survey area of 15 000 deg2, and the limitations of applicability of Euclid data to detect UCDs using the methods employed in this paper are discussed.

CARMENES input catalogue of M dwarfs

Context. The relevance of M dwarfs in the search for potentially habitable Earth-sized planets has grown significantly in the last years. Aims. In our on-going effort to comprehensively and accurately characterise confirmed and potential planet-hosting M dwarfs, in particular for the CARMENES survey, we have carried out a comprehensive multi-band photometric analysis involving spectral energy distributions, luminosities, absolute magnitudes, colours, and spectral types, from which we have derived basic astrophysical parameters. Methods. We have carefully compiled photometry in 20 passbands from the ultraviolet to the mid-infrared, and combined it with the latest parallactic distances and close-multiplicity information, mostly from Gaia DR2, of a sample of 2479 K5 V to L8 stars and ultracool dwarfs, including 2210 nearby, bright M dwarfs. For this, we made extensive use of Virtual Observatory tools. Results. We have homogeneously computed accurate bolometric luminosities and effective temperatures of 1843 single stars, derived their radii and masses, studied the impact of metallicity, and compared our results with the literature. The over 40 000 individually inspected magnitudes, together with the basic data and derived parameters of the stars, individual and averaged by spectral type, have been made public to the astronomical community. In addition, we have reported 40 new close multiple systems and candidates (ρ < 3.3 arcsec) and 36 overluminous stars that are assigned to young Galactic populations. Conclusions. In the new era of exoplanet searches around M dwarfs via transit (e.g. TESS, PLATO) and radial velocity (e.g. CARMENES, NIRPS+HARPS), this work is of fundamental importance for stellar and therefore planetary parameter determination.

Clusterix 2.0: a virtual observatory tool to estimate cluster membership probability

ABSTRACT Clusterix 2.0 is a web-based, Virtual Observatory compliant, interactive tool for the determination of membership probabilities in stellar clusters based on proper-motion data using a fully non-parametric method. In an area occupied by a cluster, the frequency function is made up of two contributions: cluster and field stars. The tool performs an empirical determination of the frequency functions from the vector point diagram without relying on any previous assumption about their profiles. Clusterix 2.0 allows us to search the appropriate spatial areas in an interactive way until an optimal separation of the two populations is obtained. Several parameters can be adjusted to make the calculation computationally feasible without interfering with the quality of the results. The system offers the possibility to query different catalogues, such as Gaia, or upload a user’s own data. The results of the membership determination can be sent via Simple Application Messaging Protocol (SAMP) to Virtual Observatory (VO) tools such as Tool for OPerations on Catalogues And Tables (TOPCAT). We apply Clusterix 2.0 to several open clusters with different properties and environments to show the capabilities of the tool: an area of five degrees radius around NGC 2682 (M67), an old, well-known cluster; a young cluster NGC 2516 with a striking elongated structure extended up to four degrees; NGC 1750 and NGC 1758, a pair of partly overlapping clusters; the area of NGC 1817, where we confirm a little-known cluster, Juchert 23; and an area with many clusters, where we disentangle two overlapping clusters situated where only one was previously known: Ruprecht 26 and the new Clusterix 1.

Astronomy Data, Virtual Observatory and Education

AbstractWe shall present with examples how analysis of astronomy data can be used for an educational purpose to train users in methods of data analysis, statistics, programming skills and research problems. Special reference will be made to our IAU-OAD project ‘Astronomy from Archival Data’ where we are in the process of building a repository of instructional videos and reading material for undergraduate and postgraduate students as well as interested participants. Virtual Observatory tools will also be discussed and applied. As this is an ongoing project, by the time of the conference we will have the projects and work done by students included in our presentation. The material produced can be freely used by the community.

Identification of asteroids using the Virtual Observatory: the WFCAM Transit Survey

Abstract The nature and physical properties of asteroids, in particular those orbiting in the near-Earth space, are of scientific interest and practical importance. Exoplanet surveys can be excellent resources to detect asteroids, both already known and new objects. This is due to their similar observing requirements: large fields of view, long sequences, and short cadence. If the targeted fields are not located far from the ecliptic, many asteroids will cross the field of view occasionally. We present two complementary methodologies to identify asteroids serendipitously observed in large-area astronomical surveys. One methodology focuses on detecting already known asteroids using the Virtual Observatory tool SkyBoT, which predicts their positions and motions in the sky at a specific epoch. The other methodology applies the ssos pipeline, which is able to identify known and new asteroids based on their apparent motion. The application of these methods to the 6.4 deg2 of the sky covered by the Wide-Field CAMera Transit Survey in the J-band is described. We identified 15 661 positions of 1821 different asteroids. Of them, 182 are potential new discoveries. A publicly accessible online, Virtual Observatory compliant catalogue was created. We obtained the shapes and periods for five of our asteroids from their light curves built with additional photometry taken from external archives. We demonstrated that our methodologies are robust and reliable approaches to find, at zero cost of observing time, asteroids observed by chance in astronomical surveys. Our future goal is to apply them to other surveys with adequate temporal coverage.

Stars and brown dwarfs in the σ Orionis cluster

Context. Only a few open clusters are as important for the study of stellar and substellar objects, and their formation and evolution, as the young σ Orionis cluster. However, a complete spectroscopic characterisation of its whole stellar population is still missing. Aims. We filled most of that gap with a large spectroscopic and astrometric survey of targets towards σ Orionis. Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion of confirmed cluster members with known uncontrovertible youth features. Methods. We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the 2.5 m Isaac Newton Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li I, Hα, and other key lines from these spectra, and determined spectral types. We complemented this information with Gaia DR2 astrometric data and other features of youth (mid-infrared excess, X-ray emission) compiled with Virtual Observatory tools and from the literature. Results. Of the 168 observed targets, we determined for the first time spectral types of 39 stars and equivalent widths of Li I and Hα of 34 and 12 stars, respectively. We identified 11 close (ρ ≲ 3 arcsec) binaries resolved by Gaia, of which three are new, 14 strong accretors, of which four are new and another four have Hα emission shifted by over 120 km s−1, two juvenile star candidates in the sparse population of the Ori OB1b association, and one spectroscopic binary candidate. Remarkably, we found 51 non-cluster-members, 35 of which were previously considered as σ Orionis members and taken into account in high-impact works on, for example, disc frequency and initial mass function.

J-PLUS: Discovery and characterisation of ultracool dwarfs using Virtual Observatory tools

Context. Ultracool dwarfs are objects with spectral types equal to or later than M7. Most of them have been discovered using wide-field imaging surveys. The Virtual Observatory has proven to be very useful for efficiently exploiting these astronomical resources. Aims. We aim to validate a Virtual Observatory methodology designed to discover and characterise ultracool dwarfs in the J-PLUS photometric survey. J-PLUS is a multiband survey carried out with the wide-angle T80Cam optical camera mounted on the 0.83 m telescope JAST/T80 in the Observatorio Astrofísico de Javalambre. We make use of the Internal Data Release covering 528 deg2. Methods. We complemented J-PLUS photometry with other catalogues in the optical and infrared using VOSA, a Virtual Observatory tool that estimates physical parameters from the spectral energy distribution fitting to collections of theoretical models. Objects identified as ultracool dwarfs were distinguished from background M giants and highly reddened stars using parallaxes and proper motions from Gaia DR2. Results. We identify 559 ultracool dwarfs, ranging from i = 16.2 mag to i = 22.4 mag, of which 187 are candidate ultracool dwarfs not previously reported in the literature. This represents an increase in the number of known ultracool dwarfs of about 50% in the region of the sky we studied, particularly at the faint end of our sensitivity, which is interesting as reference for future wide and deep surveys such as Euclid. Three candidates are interesting targets for exoplanet surveys because of their proximity (distances less than 40 pc). We also analysed the kinematics of ultracool dwarfs in our catalogue and found evidence that it is consistent with a Galactic thin-disc population, except for six objects that might be members of the thick disc. Conclusion. The results we obtained validate the proposed methodology, which will be used in future J-PLUS and J-PAS releases. Considering the region of the sky covered by the Internal Data Release used in this work, we estimate that 3000–3500 new ultracool dwarfs will be discovered at the end of the J-PLUS project.

Search and study of asteroids from the digitized first Byurakan survey using virtual observatory tools

The Digitized First Byurakan Survey (DFBS) is the digitized version of the Markarian Survey and it is the largest spectroscopic survey by its sky coverage (17, 000 deg2) and by the number of spectra (∼40,000,000). It provides a unique possibility to compare objects between different epochs, as the observations have been carried out in 1965–1980 and it complements the epochs between POSS1 and POSS2. DFBS is especially efficient for discovery and study of moving objects, such as asteroids. On the other hand, searching with a “naked eye” in planetary data archives takes a considerable time. Therefore, such work must be done in an automatic way. However, the planetary data archive is subject to a constant change (new elements, new version of analysis, new parameters). Furthermore, there are several archives for the same object, thus, obtaining reliable information requires a sequential search of several different archives. Workflows developed in the frame of the virtual observatories (VO), can use all collections of integrated astronomical data archives and software tools that utilize computer networks to create an environment in which research can be conducted. In this paper, we have used the VO tool SkyBoT for searching for asteroids in the DFBS and other archives and we have developed a workflow using a selection of the VO tools in the case of the hot topic of asteroids.

Bridging the Gap Between Geographical Information Systems and Planetary Virtual Observatory

Virtual Observatory tools are specifically designed for astronomical data, but they can be adapted to work with geospatial data by providing existing Geographical Information System tools with Simple Application Messaging Protocol interface. Open source QGIS package was chosen as a platform for this. The Simple Application Messaging Protocol interface was made with Python plug‐ins. Geospatial data were exposed to Virtual European Solar and Planetary Access via a dedicated German Astronomical Virtual Observatory Data Center Helper Suite server and several tables exposing existing Open Geospatial Consortium—compliant planetary services were published to Virtual European Solar and Planetary Access providing a variety of geospatial data types: vector data and spectral cube rasters, as well as Open Geospatial Consortium Web Map Service of planetary maps.

The XinJiang Astronomical Observatory NSRT Pulsar Data Archive

The sensitivity of our pulsar observation system with typical integration time of 16 minutes has reached 0.4 mJy after we have upgraded the receiver cooling system of NanShan 25-m radio telescope (NSRT) at Xinjiang Astronomical Observatory (XAO) in 2002. About 280 pulsars were observed after the upgrade. The NanShan station pulsar data is transmitted to the data center at XAO headquarters via a 300Mb/s dedicated data link for long-term storage, and the remote backup is realized by synchronous data transmission between NanShan station and XAO headquarters. Metadata extraction, archiving, and releasing are completed by the data release servers which are located in XAO headquarters. At present, more than 84000 pulsar observation data files in the PSRFITS format have been released with a maximum file size of 1GB. XAO pulsar data online service provides cone search and multiobject constraint query. We have published our data based on Virtual Observatory (VO) standards. The online pulsar data service is registered in the International Virtual Observatory Alliance’s Registry. Users can access the data through common VO tools.

A white dwarf catalogue from Gaia-DR2 and the Virtual Observatory

We present a catalogue of 73,221 white dwarf candidates extracted from the astrometric and photometric data of the recently published Gaia DR2 catalogue. White dwarfs were selected from the Gaia Hertzsprung-Russell diagram with the aid of the most updated population synthesis simulator. Our analysis shows that Gaia has virtually identified all white dwarfs within 100 pc from the Sun. Hence, our sub-population of 8,555 white dwarfs within this distance limit and the colour range considered, $-\,0.52<(G_{\rm BP}-G_{\rm RP})<0.80$, is the largest and most complete volume-limited sample of such objects to date. From this sub-sample we identified 8,343 CO-core and 212 ONe-core white dwarf candidates and derived a white dwarf space density of $4.9\pm0.4\times10^{-3}\,{\rm pc^{-3}}$. A bifurcation in the Hertzsprung-Russell diagram for these sources, which our models do not predict, is clearly visible. We used the Virtual Observatory tool VOSA to derive effective temperatures and luminosities for our sources by fitting their spectral energy distributions, that we built from the UV to the NIR using publicly available photometry through the Virtual Observatory. From these parameters, we derived the white dwarf radii. Interpolating the radii and effective temperatures in hydrogen-rich white dwarf cooling sequences, we derived the surface gravities and masses. The Gaia 100 pc white dwarf population is clearly dominated by cool ($\sim$ 8,000 K) objects and reveals a significant population of massive ($M \sim 0.8 M_{\odot}$) white dwarfs, of which no more than $\sim$ $30-40 \%$ can be attributed to hydrogen-deficient atmospheres, and whose origin remains uncertain.

The mean transmission of the neutral intergalactic medium in the LYα -line from a sample of high-resolution quasar spectra

We present our measurements of the mean transmission $$\overline F \left( z \right)$$ of the neutral intergalactic medium in the Lyα line. For this purpose we used the sample of 33 high-resolution (R = 5300…45 000) spectra selected from the public available archive of the European Southern Observatory with the help of the Virtual Observatory tools. For continuum determination in each spectra the points with maximum flux in Lyα-forest region were selected and fitted by spline. The obtained values of the mean transmission $$\overline F \left( z \right)$$ was fitted by power-law τeff = α(1 + z)β, where α = (4.4 −0.2 +4.4 )× 10–3, β = 3.278 −0.054 +0.083 for averaging of the F(z) over the redshift bins Δz = 0.1 and α = (10.6 −1.0 +1.1 )× 10–3, β = 2.685 −0.071 +0.081 for averaging over each quasar. The results were compared with those ones from previous studies of high- and low-resolution quasar spectra.

VESPA: A community-driven Virtual Observatory in Planetary Science

The VESPA data access system focuses on applying Virtual Observatory (VO) standards and tools to Planetary Science. Building on a previous EC-funded Europlanet program, it has reached maturity during the first year of a new Europlanet 2020 program (started in 2015 for 4 years). The infrastructure has been upgraded to handle many fields of Solar System studies, with a focus both on users and data providers. This paper describes the broad lines of the current VESPA infrastructure as seen by a potential user, and provides examples of real use cases in several thematic areas. These use cases are also intended to identify hints for future developments and adaptations of VO tools to Planetary Science.