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 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 …
The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards. II. NLTE spectral analysis of the OB-type subdwarf Feige 110
The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards. I. NLTE spectral analysis of the DA-type white dwarf G 191-B2B
Spectral Analyses Of The Hottest White Dwarfs: Grids Of Spectral Energy Distributions For Extremely Hot, Compact Stars In The Framework Of The Virtual Observatory
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…
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…
Discovery of wide low and very low-mass binary systems using Virtual Observatory tools
多重系统的频率及其性质是恒星形成和演化的关键约束。甚低质量天体的形成机制仍有相当大的争议，准确评估其多重性和轨道特性对于约束当前的理论模型至关重要。利用虚拟天文台的功能，我们使用UKIDSS LAS DR 10、SDSS DR 9和2 MASS星表的大面积巡天来寻找共动低和VLM双星（或多个）系统。其他目录（WISE，GLIMPSE，SuperCosmos.）的物理参数。我们报告了36个低和VLM（~M0-L0光谱类型）候选者的二元/多元系统（分离度在200和92000 AU之间）的识别，其物理关联通过共同的自行，距离和低概率的机会对齐来确认。这个新的系统列表显著地增加了其质量分离参数空间（~100）中的先前采样。我们还发现了50个低质量的天体，我们可以根据它们的光度信息将它们归类为~L0-T2。这些天体中只有一个是共同的自行大质量伴星。虽然我们无法限制大多数候选人的年龄，但除了四名可能处于中断过程中的候选人外，他们中的大多数人可能仍然受到约束。我们建议，我们的样本可以分为两个群体：一个紧密结合的宽VLM系统，预计将持续超过10 Gyr，和其他形成的弱约束宽VLM系统，将在几个Gyr内消散。
Stellar synthetic spectroscopy in the Virtual Observatory era
参数包括在VO大网格的合成光谱完全覆盖HR图。一个明显的需要是在所有红移的人口合成。理论光谱还具有预测特殊行为的能力，这些行为可能在观察到的光谱中未被注意到，或导致错误的结论。一个有趣的例子是极端贫金属恒星中的Ca II H & K线。在富碳大气中，H & K线相对于连续谱变得更弱，这将导致低估金属丰度。实际发生的是连续谱的位移，这在绝对通量合成光谱中很明显，但在观测到的连续归一化光谱中看不到。图书馆的合成光谱的描述，以及用于计算它们的代码。对通过VO提供这些库的问题以及必要的输入数据，即行列表和模型大气，作了一些评论。
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…
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…
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…
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: Part I: UKIDSS LAS DR5 vs SDSS DR7
该项目的目的是提高我们对低质量和低金属丰度群体的认识，以调查金属丰度对恒星（和亚恒星）质量函数的影响。我们提出了一个光度和自行搜索的结果，旨在发掘超冷次矮星在大规模的调查。我们采用并结合了UKIDSS LAS DR 5和SDSS DR 7，并补充了来自2 MASS、DENIS和SuperCOSMOS的辅助数据。SDSS DR 7与UKIDSS LAS DR 5的搜索共返回了32个超冷亚矮星候选者，只有两个在文献中被认为是亚矮星。在600和1000 nm之间的光学范围内对27个候选物进行了光谱跟踪。我们确认了20颗光谱类型晚于M5的次矮星、极端次矮星或超次矮星，成功率约为60%。在这20个新的次矮星中，我们发现了2个早期的L次矮星，它们很可能位于100 pc以内，我们建议将它们作为未来搜索的模板，因为它们是它们子类的第一个例子。另外7个源是太阳金属丰度M矮星，光谱类型在M4和M7之间，没有H α发射，表明它们是古老的M矮星。剩下的5颗候选星还没有后续的光谱观测，只有1颗在修正了自行后仍然是真正的超冷亚矮星。我们根据当前的分类方案分配光谱类型，并在可能的情况下测量它们的径向速度。利用有限数量的具有三角形半径的次矮星，我们估计新的次矮星的距离在90到600之间。我们提供了两颗亚矮星的WISE中红外测光结果，并讨论了它们的颜色。最后，我们估计了超冷次矮星表面密度的下限，其数量级比太阳金属丰…
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…
Flares and CMEs can have deleterious effects on their surroundings: they can erode atmospheres of orbiting planets over time and also have high importance in stellar evolution. Most of the CME detections in the literature are single events found serendipitously sparse for statistical investigation. We aimed to gather a large amount of spectral data of M-dwarfs to drastically increase the number of known events to make statistical analysis possible in order to study the properties of potential stellar CMEs. Using archive data we investigated asymmetric features of Balmer-lines, that could indic…
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 …
Identification of unresolved binaries in the VVV b294 tile: A Pro-Am collaboration using the Virtual Observatory
Universidad Complutense de Madrid（马德里康普顿斯大学）；Centro de Astrobiología (CSIC-INTA)（天体生物学中心（西班牙国家研究委员会-国家航空航天技术研究所））；Asociación Astronómica AstroHenares（AstroHenares天文协会）；Agrupación Astronómica de Córdoba（科尔多瓦天文团）；Agrupación Astronómica de Sabadell（萨巴德尔天文团）
Archives of Photographic PLates for Astronomical USE (APPLAUSE) Digitisation of astronomical plates and their integration into the International Virtual Observatory
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 …
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS
我们的目标是发展一种有效的方法来寻找晚型次矮星（光谱类型>M5的金属耗尽矮星），以改善目前的统计。我们的目标是：提高我们对贫金属低质量矮星的认识，弥合晚M型和L型之间的差距，确定它们的表面密度，并了解金属丰度对恒星和亚恒星质量函数的影响。我们使用STILTS、Aladin和Topcat对SDSS、2 MASS和UKIDSS进行了交叉匹配搜索。我们考虑了不同的光度和自行标准，我们的选择。我们确定了29和71晚型亚矮星候选人在每个交叉相关超过8826和3679平方度，分别。我们获得了71个候选人的低分辨率光谱与GTC，NOT和VLT和检索光谱的30个候选人从SDSS光谱数据库。我们分类92候选人的101光谱的基础上使用两种方法：光谱指数和比较与模板已知的次矮星。我们分别从SDSS与2 MASS和SDSS与UKIDSS交叉匹配中确认了86%和94%的候选者为晚型次矮星。这些次矮星的光谱类型介于M5和L0.5之间，SDSS星等在r=19.4-23.3等范围内。我们新发现的晚型M包括49颗次矮星、25颗极端次矮星、6颗超次矮星、1颗次矮星/极端次矮星和2颗矮星/次矮星。在SDSS DR 7与UKIDSS LAS DR 10的交叉比对中，我们得出晚型次矮星的表面密度为每平方度0.040 $^{+0.012}_{-0.007}$。我们还检查了已知和新的亚矮星的AllWISE测光，发现M亚矮星的中…
