We present the results of the photographic spectral observations of MWC560 carried out in the period 1990-1993. The evolution of the spectrum, the changes in the radial velocities of the different line systems, as well as the variations in the equivalent widths of the different Balmer absorption components, are given and briefly discussed. The suggestion that the hot component of MWC560 ejects high-velocity, highly-collimated jets along the line of sight, is in very good agreement with the observations. All the results, including the variations in the shapes, velocities and equivalent widths of the strong-shifted Balmer absorptions, confirm that compact companion in MWC560 ejects matter in two different regimes - discrete and quasi-stationary. It is supposed that the permanent presence of a relatively weak and small-shifted Balmer absorption component in the spectrum, indicates additional persistent, not spherically symmetric matter outflow.
V838 Mon erupted at the beginning of 2002. In the course of the outburst the object evolved to low effective temperatures and declined as a very late M-type supergiant. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. We aim at studying the structure and evolution of the object in the decline from the 2002 eruption. We obtained spectroscopic observations of V838 Mon in January-March 2009 with UVES/VLT. The results are analysed and compared with similar observations obtained in October 2005 with HIRES/Keck. The most striking difference between 2009 and 2005 is a complete absence of the B3 V component and of the [FeII] emission lines in 2009. The present spectrum displays only the spectrum of the 2002 eruption remnant. It resembles that of an ~M6 giant, although the molecular bands in V838 Mon are deeper than those in standard stellar spectra of a similar spectral class. Several atomic lines, which displayed P-Cyg profiles in 2005, are now dominated by pure absorptions. Some of these lines, however, show a narrow emission component, which, as we argue, measures the radial velocity of V838 Mon. The resulting heliocentric velocity is 71km/s, which very well agrees with the velocity obtained from SiO maser observations. The atomic lines and the molecular bands show very complex kinematics. In some atomic lines and high-excitation molecular bands we observe matter infalling in the object atmosphere. The infall components were already observed in 2005, but were less pronounced and present in fewer lines than in 2009. We argue that the most negative radial velocity components seen in the resonance atomic lines and in the low-excitation molecular bands were formed in the ejecta of the 2002 eruption. The B3V companion most probably became engulfed in an opaque dusty matter of the 2002 V838 Mon ejecta.
FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its Ks-band brightness only 1.5mag below the outburst brightness level. Our Very Large Telescope (VLT)/XSHOOTER spectroscopic observations display several strong forbidden emission lines toward the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.
In this document, we discuss practices related to the use of RDF-based
consensus vocabularies in the Virtual Observatory, that is the creation,
publication, maintenance, and consumption of hierarchical word lists
agreed upon within the IVOA. To cover the wide range of use cases
envisoned, we define different vocabulary types for informal knowledge
organisation on the one hand, and strict hierarchies of classes and
properties on the other. While the framework rests on the solid
foundations of W3C RDF, provisions are made to facilitate using IVOA
vocabularies without specific RDF tooling. Non-normative appendices
detail the current vocabulary-related tooling.
VODataService: a VOResource Schema Extension for Describing Collections and Services
Date:
21 Oct 2016 08:20:00
Publisher:
IVOA
Description:
VODataService refers to an XML encoding standard for a specialized extension of
the IVOA Resource Metadata that is useful for describing data collections and
the services that access them. It is defined as an extension of the core
resource metadata encoding standard known as VOResource [Plante et al. 2008]
using XML Schema. The specialized resource types defined by the VODataService
schema allow one to describe how the data underlying the resource cover the sky
as well as cover frequency and time. This coverage description leverages
heavily the Space-Time Coordinates (STC) standard schema [Rots 2007].
VODataService also enables detailed descriptions of tables that includes
information useful to the discovery of tabular data. It is intended that the
VODataService data types will be particularly useful in describing services
that support standard IVOA service protocols.
VO-DML: a consistent modeling language for IVOA data models
Date:
31 May 2018 09:00:00
Publisher:
IVOA
Description:
This document defines a standard modelling language, or meta-model, for
expressing data models in the IVOA. Adopting such a uniform language for all
models allows these to be used in a homogeneous manner and allows a
consistent definition of reuse of one model by another. The particular language
defined here includes a consistent identification mechanism for model which
allows these to be referenced in an explicit and uniform manner also from other
contexts, in particular from othe IVOA standard formats such as VOTable.
The language defined in this specification is named VO-DML (VO Data Modeling
Language). VO-DML is a conceptual modeling language that is agnostic of
serializations, or physical representations. This allows it to be designed to
fit as many purposes as possible. VO-DML is directly based on UML, and can be
seen as a particular representation of a UML2 Profile. VO-DML is restricted to
describing static data structures and from UML it only uses a subset of the
elements defined in its language for describing "Class Diagrams". Its concepts
can be easily mapped to equivalent data modelling concepts in other
representations such as relational databases, XML schemas and object-oriented
computer languages.
VO-DML has a representation as a simple XML dialect named VO-DML/XML
that must be used to provide the formal representation of a VO-MDL data model.
VO-DML/XML aims to be concise, explicit and easy to parse and use in code that
needs to interpret annotated data sets.
VO-DML as described in this document is an example of a domain specific
modeling language, where the domain here is defined as the set of data and
meta-data structures handled in the IVOA and Astronomy at large. VO-DML
provides a custom representation of such a language and as a side effect allows
the creation and use of standards compliant data models outside of the IVOA
standards context.
The ephemeris were produced by simulating the ejection of meteoroids
from the sunlit hemisphere of cometary nuclei, typically from 0 to 3
au, followed by the propagation of orbits of meteoroids in the Solar
System, taking into account the gravity of the Sun, the 8 planets,
Pluto, and the Moon, as well as the radiation pressure and the
Poynting-Robertson drag. Note that asteroid parent bodies were
considered as active (i.e. comet-like bodies) even if they are not
active today. The showers are predicted when a planet enters a large
enough set of meteoroids, at a distance less than typically 0.01 au.
See Vaubaillon J., Colas F., Jorda L. 2005 A new method to predict
meteor showers. I. Description of the model, Astronomy and
Astrophysics, Volume 439/2 p.751-760, as well as: Vaubaillon J. 2017 A
confidence index for forecasting of meteor showers, Planetary and
Space Science, Volume 143 p.78-82
New entries in the
`Virtual Observatory <http://www.ivoa.net>`_'s registry in RSS format;
this service lets you use a common "news aggregator" to learn of
services appearing in the VO in almost real time.
The data is taken from the VO registry by querying for new records
twice a day. New items are announced here for 30 days.
To subscribe to this feed, point your browser/news aggregator
to http://dc.g-vo.org/regrss.
If you can configure your client's update frequency, for this feed it
is sufficient to update every 12 hours -- it is only updated morining and
afternoon UTC.
New entries on this feed are also distributed `on the Fediverse`_. To
get notifications of new VO services, subscribe to `gavo@botsin.space`_.
.. _gavo@botsin.space:
.. _on the Fediverse: https://botsin.space/@gavo
Space Research Centre of Polish Academy of Sciences
Description:
The VO HPSL datacenter is TAP end point. The Table Access Protocol
(TAP) lets you execute queries against our database tables, inspect
various metadata, and upload your own data. It is thus the VO's
premier way to access public data holdings.
Tables exposed through this endpoint include: columns, groups, key_columns, keys, schemas, tables from the tap_schema schema, epn_core from the rwcalerts schema, epn_core from the lofar_jupiter_raw schema, main from the arihip schema, epn_core from the lofar_jupiter schema, epn_core from the ionosondes schema, epn_core from the rwc_alerts schema, epn_core from the planetmongo schema.