VOEvent
VOEvent is a standardized language used to report observations of astronomical events; it was officially adopted[1] in 2006 by the International Virtual Observatory Alliance (IVOA). Though most VOEvent messages currently issued are related to supernovae, gravitational microlensing, and gamma-ray bursts, they are intended to be general enough to describe all types of observations of astronomical events, including gravitational wave events. Messages are written in XML, providing a structured metadata description of both the observations and the inferences derived from those observations. The rapid dissemination of event data with a formalized language was the original impetus[2] for the creation of VOEvents and the network (now called VOEventNet) used to transport the messages; indeed VOEvent messages are designed to be compact and quickly transmittable over the internet. The VOEvent language (which is codified in an XML schema) continues to evolve; the latest version is 2.0.
Contents
History
VOEvent builds upon previous generic publishing schemes such as International Astronomical Union Central Bureau for Astronomical Telegrams (IAUCs and CBETs) and the Astronomer's Telegrams (ATELs). The principal difference is that VOEvent messages are intended to be automatically parsed and filtered whereas ATELs and IAUCs are intended to be read by humans. The scope of VOEvent is informed by several other messaging schemes used to facilitate rapid discovery announcements for specialized sub-fields of astronomy (such as OGLE microlensing alerts and Supernova Early Warning System). The closest ancestors of VOEvent are The Telescope Alert Operation Network System (TALON)[3] and the Gamma Ray Burst Coordinates Network (GCN) messages, used extensively by the gamma-ray burst community.
Structure of the Language
A typical VOEvent message contains the following tags:
- <who> - describing who is responsible (the author and the publisher) for the information contained in the message
- <how> - a description of the instrumental setup on where the data were obtained
- <what> - the data (such as source flux) associated with the observations of the event
- <why> - inferences about the nature of the event
- <wherewhen> - description of the time and place where the event was recorded. This draws from the Space-time Coordinate (STC) recommendation to the IVOA.
A well-formed VOEvent message must validate against the VOEvent schema (.xsd). A valid message may omit most of the informational tags listed above, but since the creation of VOEvent messages is done automatically, most opt to transmit the fullest content available.
Current uses
As with most products of the Virtual Observatory, there are no promises that once a VOEvent message has been issued, it will persist indefinitely. It is the role of the publisher, generally, to maintain and curate VOEvents issued. Still, public VOEvent messages may be distributed and or archived through 3rd parties.
VOEvent Software
- Dakota tools on SourceForge
- Comet, a complete VOEvent transport system
- voevent-parse, VOEvent parsing and manipulation routines for Python
VOEvent feeds
There are live VOEvent feeds (through a variety of protocols, such as RSS and XMPP) currently available from:
- The Skyalert project at Caltech.
- DC-3 Dreams, SP
- The 4PiSky project at the University of Oxford.
Vizualizations
Since VOEvents note the location and time events, it is possible to convert streams of events into temporal or spatial visualizations. Skyalert has Worldwide Telescope views of the event sky. eStar hosts an AJAX mashup of microlensing events.
