Recent massive sky surveys in different bandwidths are providing new opportunities to modern astronomy. The Virtual Observatory (VO) represents the adequate framework to handle the huge amount of information available and filter out data according to specific requirements.
In this work, we applied a selection strategy to find new, uncatalogued hot subdwarfs making use of VO tools. We used large area catalogues (GALEX, SDSS, SuperCosmos, 2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cutoff, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates. Based on previous results, we expect our procedure to have an overall efficiency of at least 80 per cent. Visual inspection of the 68 candidates with SDSS spectrum showed that 65 can be classified as hot subdwarfs: 5 sdOs, 25 sdOBs and 35 sdBs. This success rate above 95 per cent proves the robustness and efficiency of our methodology.
The spectral energy distribution of 45 per cent of the subdwarf candidates showed infrared excesses, a signature of their probable binary nature. The stellar companions of the binary systems so detected are expected to be late-type main sequence stars. A detailed determination of temperatures and spectral classification of the cool companions will be presented in a forthcoming work.
In the last few years, we have carried out several extensive observational campaigns on pulsating hot subdwarf stars using the Mont4K CCD camera attached to the 1.55 m Kuiper Telescope on Mount Bigelow. The Mont4K is a joint partnership between the University of Arizona and Universite de Montreal. It was designed and built at Steward Observatory. Using the Mont4K/Kuiper combination, we have so far, and among others, gathered high-sensitivity broadband light curves for PG 1219+534, PB8783, HS 0702+6043, and Feige 48. We report very briefly on some of the most interesting observational results t…
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. We made use of Virtual Observatory tools and large-scale public surveys to look in Gaia for 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 de…
Hot subdwarf stars are faint, blue objects, and are the main contributors to the far-UV excess observed in elliptical galaxies. They offer an excellent laboratory to study close and wide binary systems, and to scrutinize their interiors through asteroseismology, as some of them undergo stellar oscillations. However, their origins are still uncertain, and increasing the number of detections is crucial to undertake statistical studies. In this work, we aim at defining a strategy to find new, uncatalogued hot subdwarfs. Making use of Virtual Observatory tools we thoroughly search stellar catalogu…
The aim of the project is to improve our knowledge on the low-mass and low-metallicity population to investigate the influence of metallicity of the stellar (and substellar) mass function. We present the results of a photometric and proper motion search aimed at unearthing ultracool subdwarfs in large-scale surveys. We employed and combined the UKIDSS LAS DR5 and the SDSS DR7 complemented with ancillary data from 2MASS, DENIS and SuperCOSMOS. The SDSS DR7 vs UKIDSS LAS DR5 search returned a total of 32 ultracool subdwarf candidates, only two being recognised as a subdwarf in the literature. Tw…
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. Ou…
In the framework of the Virtual Observatory (VO), the German Astrophysical Virtual Observatory (GAVO) developed the registered service TheoSSA (Theoretical Stellar Spectra Access). It provides easy access to stellar spectral energy distributions (SEDs) and is intended to ingest SEDs calculated by any model-atmosphere code, generally for all effective temperature, surface gravities, and elemental compositions. We will establish a database of SEDs of flux standards that are easily accessible via TheoSSA's web interface. The OB-type subdwarf Feige 110 is a standard star for flux calibration. Stat…
With available Virtual Observatory tools, we looked for new bright blue high proper motion objects in the entire sky: white dwarfs, hot subdwarfs, runaway OB stars, and early-type stars in nearby young moving groups. We performed an all-sky cross-match between the optical Tycho-2 and near-infrared 2MASS catalogues with Aladin, and selected objects with proper motions >50mas/yr and colours Vt-Ks<-0.5mag with TOPCAT. We also collected multi-wavelength photometry, constructed the spectral energy distributions and estimated effective temperatures from fits to atmospheric models with VOSA for the m…
We aim at developing an efficient method to search for late-type subdwarfs (metal-depleted dwarfs with spectral types >M5) to improve the current statistics. Our objectives are: improve our knowledge of metal-poor low-mass dwarfs, bridge the gap between the late-M and L types, determine their surface density, and understand the impact of metallicity on the stellar and substellar mass function. We carried out a search cross-matching the SDSS, 2MASS, and UKIDSS using STILTS, Aladin, and Topcat. We considered different photometric and proper motion criteria for our selection. We identified 29 and…
We present an update of our low-resolution spectroscopic follow-up and model atmosphere analysis of hot subdwarf stars from the Galaxy Evolution Explorer (GALEX) survey. Targets were selected on the basis of colour indices calculated from the GALEX GR6 N_UV, Guide Star Catalogue (GSC2.3.2) V and the Two Micron All Sky Survey (2MASS) J and H photometry. High signal-to-noise ratio spectra were obtained at the European Southern Observatory (ESO) and the Kitt Peak National Observatory (KPNO) over the course of three years. Detailed H, He and CNO abundance analysis helped us improve our T_eff, log …
We present a model-fit pipeline to determine the stellar parameters of M-type dwarfs, which is an improvement upon our previous work described in Hejazi et al. 2020. We apply this pipeline to analyze the low-resolution (R~2000) spectra of 3745 M dwarfs/subdwarfs, collected at the MDM Observatory, Lick Observatory, Kitt Peak National Observatory, and Cerro Tololo Interamerican Observatory. We examine the variation of the inferred parameter values in the HR diagram constructed from their Gaia Early Data Release 3 (EDR3) parallaxes and optical magnitudes. We also study the distribution of our sta…
New, updated, and/or revised CCD parallaxes determined with the Strand Astrometric Reflector at the Naval Observatory Flagstaff Station (NOFS) are presented. Included are results for 309 late-type dwarf and subdwarf stars observed over the 30+ years that the program operated. For 124 of the stars, parallax determinations from other investigators have already appeared in the literature and we compare the different results. Also included here is new or updated $VI$ photometry on the Johnson-Kron-Cousins system for all but a few of the faintest targets. Together with 2MASS $JHK_s$ near-infrared p…
We investigate and parameterise high proper motion red stars in the Torino Observatory Parallax Program. Observations of 27 objects were made over the period 1994 - 2001 on the 1.05m Torino telescope. The trigonometric parallaxes and proper motions were determined using standard techniques. We determine parallaxes and proper motions, and by comparison to models we infer masses, ages, and {metallicities}. Of the 27 objects, 22 are within 25pc and 4 appear to be subdwarfs. There are published parallaxes for 18 objects, and all but 4 agree to within 2$σ$. The discrepancies are discussed.
We report the discovery of two new hot, hydrogen-rich subdwarfs (sdB) in close binary systems. The hot subdwarfs, GALEX J0321+4727 and GALEX J2349+3844, were selected from a joint optical-ultraviolet catalogue of hot sub-luminous stars based on GSC2.3.2 and the Galaxy Evolution Explorer all-sky survey. Using high-dispersion spectra of the Halpha core obtained using the 2m telescope at Ondrejov Observatory we measured the radial velocities of the sdB primaries and determined orbital periods of 0.26584+/-0.00004 days and 0.46249+/-0.00007 days for GALEX J0321+4727 and GALEX J2349+3844, respectiv…
In the last decade, numerous Virtual Observatory organizations were established. One of these is the German Astrophysical Virtual Observatory (GAVO) that e.g. provides access to spectral energy distributions via the service TheoSSA. In a pilot phase, these are based on the Tuebingen NLTE Model-Atmosphere Package (TMAP) and suitable for hot, compact stars. We demonstrate the power of TheoSSA in an application to the sdOB primary of AA Doradus by comparison with a "classical" spectral analysis.
In the framework of the Virtual Observatory, the newly developed service TheoSSA provides access to theoretical stellar spectral-energy distributions. In a pilot phase, this service is based on the well established Tuebingen NLTE Model-Atmosphere Package for hot, compact stars. We demonstrate its present capabilities and future extensions.
The Virtual Observatory (VO) provides access to both, data and theory. Quality control is a general problem and the VO user needs partly some experience to judge the reliability of the VO products. As far as spectral analysis is concerned, many different areas are involved, from atomic data to stellar model-atmosphere codes. Within the framework of the German Astrophysical Virtual Observatory (GAVO) project, the service TheoSSA is developed. It allows the VO user an easy access to synthetic spectral energy distributions (SEDs). We discuss quality control problems and the reliability of SEDs pr…
Present X-ray missions like Chandra and XMM-Newton provide high-resolution and high-S/N observations of extremely hot white dwarfs, e.g. burst spectra of novae. Their analysis requires adequate Non-LTE model atmospheres. The Tübingen Non-LTE Model-Atmosphere Package TMAP can calculate such model atmospheres and spectral energy distributions at a high level of sophistication. In the framework of the Virtual Observatory, the German Astrophysical Virtual Observatory (GAVO) offers TheoSSA, a Virtual Observatory (VO) service that provides easy access to theoretical SEDs. We present a new grid of SE…
In a collaboration of the German Astrophysical Virtual Observatory (GAVO) and AstroGrid-D, the German Astronomy Community Grid (GACG), we provide a VO service for the access and the calculation of stellar synthetic energy distributions (SEDs) based on static as well as expanding non-LTE model atmospheres. At three levels, a VO user may directly compare observed and theoretical SEDs: The easiest and fastest way is to use pre-calculated SEDs from the GAVO database. For individual objects, grids of model atmospheres and SEDs can be calculated on the compute resources of AstroGrid-D within reasona…
We assembled a catalogue of bright, hot subdwarf and white dwarf stars extracted from a joint ultraviolet, optical, and infrared source list. The selection is secured using colour criteria that correlate well with effective temperatures T_eff ~> 12,000 K. We built a N_UV-V versus V-J diagram for more than 60,000 bright sources using the Galaxy Evolution Explorer (GALEX) N_UV magnitude (N_UV<14), and the associated Guide Star Catalog (GSC2.3.2) photographic quick-V magnitude and the Two Micron All Sky Survey (2MASS) J and H magnitudes. This distillation process delivered a catalogue of approxim…
This paper describes the main characteristics of the Virtual Observatory as a research infrastructure in Astronomy, and identifies those fields in which it can be of help for the community of spectral stellar libraries.
Detection of hot subdwarf binaries and sdB stars using machine learning methods and a large sample of Gaia XP spectra
Institute of Theoretical Physics and Astronomy, Vilnius University（维尔纽斯大学理论与天体物理研究所）；Centro de Astrobiología (CSIC-INTA)（天体生物学中心（CSIC-INTA））；Applied Physics Department, Universidade de Vigo（维戈大学应用物理系）；Centro de Investigación Mariña, Universidade de Vigo（维戈大学海洋研究中心）；Universidade da Coruña (UDC)（拉科鲁尼亚大学）；CIGUS CITIC - Department of Computer Science and Information Technologies, University of A Coruña（拉科鲁尼亚大学CIGUS CITIC计算机与信息技术系）；IES de Beade, Conseller ı́a de Educación e Ordenación Universitaria（贝德高中，加利西亚教育及大学统筹部）；Institute of Applied Mathematics, Vilnius University（维尔纽斯大学应用数学研究所）；CIGUS CITIC - Department of Nautical Sciences and Marine Engineering, University of A Coruña（拉科鲁尼亚大学CIGUS CITIC航海科学与海洋工程系）
Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations $>$20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core ($\sim$5,000$-$10,000 au). We mined the recently published Gaia-DR2 catalog to identify bright comoving systems in the five-dimensional space (sky position, parallax, and proper motion). We identified 3,741 comoving binary and multiple stellar candidate…
Using Virtual Observatory tools, we cross-matched the Carlsberg Meridian 14 and the 2MASS Point Source catalogs to select candidate nearby bright M dwarfs distributed over ~ 25,000 deg^2. Here, we present reconnaissance low-resolution optical spectra for 27 candidates that were observed with the Intermediate Dispersion Spectrograph at the 2.5m Isaac Newton Telescope (R ~ 1600). We derived spectral types from a new spectral index, R, which measures the ratio of fluxes at 7485-7015 A and 7120-7150 A. We also used VOSA, a Virtual Observatory tool for spectral energy distribution fitting, to deriv…
We examine a sample of 223 F, G and early K metal-poor subdwarfs ([m/H]<-1) with high proper motions ($μ> 0.2"/$ year) at the distances of up to 250 pc from the Sun. By means of our own speckle interferometric observations conducted on the 6 m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, and the spectroscopic and visual data taken from the literature, we determine the frequency of binary and multiple systems in this sample. The ratio of single, binary, triple and quadruple systems among 221 primary components of the sample is 147:64:9:1. We show th…
Starting from the Strasbourg ESO Catalogue (SEC) of Planetary Nebulae (PNe), the largest PNe compilation available with ~ 1500 objects, we undertook a comprehensive study of the whole PN population, never carried out so far, only using on-line catalogues and data from public imaging surveys. The study includes the PN dynamics through their measured proper motions (PMs), the study of their galactocentric orbits, the study of their interactions with the interstellar medium (ISM), and the study of their UV-to-IR spectral energy distribution (SED). As a preliminary step required to perform cross-c…
The aim of the project is to search for lithium in absorption at 6707.8 Angstroms to constrain the nature and the mass of the brightest low-metallicity L-type dwarfs (refered to as L subdwarfs) identified in large-scale surveys. We obtained low- to intermediate-resolution (R~2500-9000) optical (~560-770 nm) spectra of two mid-L subdwarfs, SDSSJ125637.13-022452.4 (SDSS1256; sdL3.5) and 2MASSJ162620.14+392519.5 (2MASS1626; sdL4) with spectrographs on the European Southern Observatory Very Large Telescope and the Gran Telescopio de Canarias. We report the presence of a feature at the nominal posi…
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 ob…
AIMS: We selected the bluest object, WISE~J0725$-$2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to unravel the nature of this relatively bright ($V$$\sim$12, $J$$\sim$11) HPM star ($μ$$=$267\,mas/yr). METHODS: We obtained low- and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/XSHOOTER instruments, investigated the radial velocity and performed a quantitative spectra…
In the last years we have witnessed a dramatic change in the research infrastructures: Advances in communication networks, computational resources and data storage devices are fostering new and more efficient science. In this new scenario, the Virtual Observatory (VO) is the framework where a new methodology for astronomical research is being built. This poster shows the natural connection between Asteroseismology and VO. We describe the current status of a project developed by the Spanish Virtual Observatory in which, for the first time, asteroseismic models together with visualization tools …
The German Astrophysical Virtual Observatory (GAVO) developed the registered service TheoSSA (theoretical stellar spectra access) and the supporting registered VO tool TMAW (Tuebingen Model-Atmosphere WWW interface). These allow individual spectral analyses of hot, compact stars with state-of-the-art non-local thermodynamical equilibrium (NLTE) stellar-atmosphere models that presently consider opacities of the elements H, He, C, N, O, Ne, Na, and Mg, without requiring detailed knowledge about the involved background codes and procedures. Presently, TheoSSA provides easy access to about 150000 …
Aims: With available Virtual Observatory tools, we looked for new M dwarfs in the solar neighbourhood and M giants with high tangential velocities. Methods: From an all-sky cross-match between the optical Tycho-2 and the near-infrared 2MASS catalogues, we selected objects with proper motions >50mas/yr and very red V-Ks colours. For the most interesting targets, we collected multi-wavelength photometry, constructed spectral energy distributions, estimated effective temperatures and surface gravities from fits to atmospheric models, performed time-series analysis of ASAS V-band light curves, and…
The frequency of multiple systems and their properties are key constraints of stellar formation and evolution. Formation mechanisms of very low-mass (VLM) objects are still under considerable debate and an accurate assessment of their multiplicity and orbital properties are essential for constraining current theoretical models. Taking advantage of the Virtual Observatory capabilities, we looked for comoving low and VLM binary (or multiple) systems using the Large Area Survey of the UKIDSS LAS DR10, SDSS DR9, and the 2MASS Catalogues. Other catalogues (WISE, GLIMPSE, SuperCosmos ...) were used …
H-rich, DA-type white dwarfs are particularly suited as primary standard stars for flux calibration. State-of-the-art NLTE models consider opacities of species up to trans-iron elements and provide reliable synthetic stellar-atmosphere spectra to compare with observation. We establish a database of theoretical spectra of stellar flux standards that are easily accessible via a web interface. In the framework of the Virtual Observatory, the German Astrophysical Virtual Observatory developed the registered service TheoSSA. It provides easy access to stellar spectral energy distributions (SEDs) an…
In this contribution we report the current stage of the MOLecular Dissociation (MOL-D) database which is a web service within the Serbian virtual observatory (SerVO) and node within Virtual Atomic and Molecular Data Center (VAMDC). MOL-D is an atomic and molecular (A&M) database devoted to the modelling of stellar atmospheres, laboratory plasmas, industrial plasmas etc. The initial stage of development was done at the end of 2014, when the service for data connected with hydrogen and helium molecular ions was done. In the next stage of the development of MOL-D, we include new cross-sections an…
Arguments for including in the VO large grids of synthetic spectra fully covering the HR diagram are presented. One obvious need is that of population synthesis at all redshifts. Theoretical spectra have also the power to predict peculiar behaviors, that could remain unnoticed in observed spectra, or lead to erroneous conclusions. One interesting example is given of the Ca II H & K lines in extremely metal-poor stars. In carbon-rich atmospheres, the H & K lines become much weaker relative to the continuum, which will lead to an underestimate of the metallicity. What actually happens is a displ…
The Virtual Observatory is a new technology of the astronomical research allowing the seamless processing and analysis of a heterogeneous data obtained from a number of distributed data archives. It may also provide astronomical community with powerful computational and data processing on-line services replacing the custom scientific code run on user's computers. Despite its benefits the VO technology has been still little exploited in stellar spectroscopy. As an example of possible evolution in this field we present an experimental web-based service for disentangling of spectra based on code …
(abridged) We want to provide further evidence of the origin of the proposed stellar members of Chamaeleon and to identify interlopers from the foreground εCha and ηCha associations. To this aim, we compile lists of spectroscopically confirmed members of Chamaeleon I and II, εCha and ηCha, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-match these lists with the UCAC3 catalogue to get the proper motions of the objects. In the vector point diagram, we identify the different moving groups, and use this information to study the membership of propose…
Massive far-red and infrared imaging surveys in different bandpasses are the main contributors to the discovery of brown dwarfs. The Virtual Observatory represents an adequate framework to handle these vast datasets efficiently and filter them out according to specific requirements. A statistically significant number of BDs is mandatory for understanding their general properties better for identifing peculiar objects. WISE, an all-sky survey in the mid-infrared, provides an excellent opportunity to increase the number of BDs significantly, in particular those at the lower end of the temperatur…
In this paper we report a search for vanishing sources in POSS I red images using Virtual Observatory archives, tools and services. The search, conducted in the framework of the VASCO project, aims at finding POSS I (red) sources not present in recent catalogues like Pan-STARRS DR2 (limiting magnitude r=21.4) or Gaia EDR3 (limiting magnitude G=21). We found 298 165 sources visible only in POSS I plates, out of which 288 770 had a crossmatch within 5 arcsec in other archives (mainly in the infrared), 189 were classified as asteroids, 35 as variable objects, 3 592 as artefacts from the compariso…
Ultracool dwarfs 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 has proven to be of great utility to efficiently exploit these astronomical resources. We aim to validate a Virtual Observatory methodology designed to discover and characterize ultracool dwarfs in deep extragalactic surveys like ALHAMBRA and COSMOS. Three complementary searches based on parallaxes, proper motions and colours, respectively were carried out. A total of 897 candidate ul…
This tutorial is devoted to extending an existing catalogue with data taken elsewhere, either from CDS Vizier or Simbad database. As an example, we used the so-called 'Spectroscopic Survey of Stars in the Solar Neighborhood' (aka. S4N, Allende Prieto et al. 2004) in order to retrieve all objects with available data for the set of fundamental stellar parameters effective temperature, surface gravity and metallicity. Then for each object in this dataset we query Simbad database to retrieve the projected rotational velocity. This combines Vizier and Simbad queries made using Python astroquery mod…
Observing Orbital Decay in the Ultracompact Hot Subdwarf Binary System ZTFJ213056.71+442046.5
Hamburger Sternwarte, University of Hamburg（汉堡天文台，汉堡大学）；Deutsches Zentrum für Astrophysik（德国天体物理中心）；Department of Physics and Astronomy, Texas Tech University（德克萨斯理工大学物理与天文学系）；Leibniz Institute for Astrophysics Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Institut für Physik und Astronomie, Universität Potsdam（波茨坦大学物理与天文学研究所）；Space Science Department, University of Alabama in Huntsville（阿拉巴马大学亨茨维尔分校空间科学系）
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 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 occasionally the field of view. We present two complementary methodologies to identify asteroids serendipitously observed in large-area astronomica…
Context. The nature of the recently identified "sdA" spectroscopic class of star is not well understood. The thousands of known sdAs have H-dominated spectra, spectroscopic surface gravities intermediate to main sequence stars and isolated white dwarfs, and effective temperatures below the lower limit for He-burning subdwarfs. Most are likely products of binary stellar evolution, whether extremely low-mass white dwarfs and their precursors, or blue stragglers in the halo. Aims. Stellar eigenfrequencies revealed through time series photometry of pulsating stars sensitively probe stellar structu…
The heterogeneity of papers dealing with the discovery and characterization of exoplanets makes every attempt to maintain a uniform exoplanet catalog almost impossible. Four sources currently available online (NASA Exoplanet Archive, Exoplanet Orbit Database, Exoplanet Encyclopaedia, and Open Exoplanet Catalogue) are commonly used by the community, but they can hardly be compared, due to discrepancies in notations and selection criteria. Exo-MerCat is a Python code that collects and selects the most precise measurement for all interesting planetary and orbital parameters contained in the four …
2MASS J06562998+3002455 or PSS 309-6 is a high proper-motion star that was discovered during a survey with the 2.1 m telescope at Kitt Peak National Observatory. Here, we reevaluate the status of this interesting star using Gaia DR2. Our results strongly suggest that PSS 309-6 could be a Population II star as the value of its V component is close to -220 km/s, which is typical for halo stars in the immediate solar neighborhood. Kapteyn's star is the nearest known halo star and PSS 309-6 exhibits similar kinematic and photometric signatures. Its properties also resemble those of 2MASS J15484023…
Archives of Photographic PLates for Astronomical USE (APPLAUSE) Digitisation of astronomical plates and their integration into the International Virtual Observatory
One of the very first steps astronomers working in stellar physics perform to advance in their studies, is to determine the most common/relevant physical parameters of the objects of study (effective temperature, bolometric luminosity, surface gravity, etc.). Different methodologies exist depending on the nature of the data, intrinsic properties of the objects, etc. One common approach is to compare the observational data with theoretical models passed through some simulator that will leave in the synthetic data the same imprint than the observational data carries, and see what set of paramete…
The third data release of Gaia has provided low resolution spectra for ~100,000 white dwarfs (WDs) that, together with the excellent photometry and astrometry, represent an unrivalled benchmark for the study of this population. In this work, we first built a highly-complete volume-limited sample consisting in 12,718 WDs within 100 pc from the Sun. The use of VOSA tool allowed us to perform an automated fitting of their spectral energy distributions to different atmospheric models. In particular, the use of spectrally derived J-PAS photometry from Gaia spectra led to the classification of DA an…
Ultracool dwarfs (UCDs) are objects with spectral types equal or later than M7. 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 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. In this work we make use of the Internal Data Releas…
University of Michigan（密歇根大学）；NASA GSFC（美国国家航空航天局戈达德太空飞行中心）；NorthWest Research Associates（西北研究协会）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）
Both NASA's Solar Dynamics Observatory (SDO) and the JAXA/NASA Hinode mission include spectropolarimetric instruments designed to measure the photospheric magnetic field. SDO's Helioseismic and Magnetic Imager (HMI) emphasizes full-disk high-cadence and good spatial resolution data acquisition while Hinode's Solar Optical Telescope Spectro-Polarimeter (SOT-SP) focuses on high spatial resolution and spectral sampling at the cost of a limited field of view and slower temporal cadence. This work introduces a deep-learning system named SynthIA (Synthetic Inversion Approximation), that can enhance …
Ultracool dwarfs (UCDs) comprise the lowest mass members of the stellar population and brown dwarfs, from M7 V to cooler objects with L, T, and Y spectral types. Most of them have been discovered using wide-field imaging surveys, for which the Virtual Observatory (VO) has proven to be of great utility. We aim to perform a search for UCDs in the entire Javalambre Photometric Local Universe Survey (J-PLUS) second data release (2176 deg$^2$) following a VO methodology. We also explore the ability to reproduce this search with a purely machine learning (ML)-based methodology that relies solely on …
