IVOA Time Domain Interest Group

Working Group Chair: Rafael Martinez-Galarza

Vice Chair: Pierre Fernique

Chairs Emeritus: Ada Nebot, Roy Williams, Rob Seaman, Matthew Graham, John Swinbank

Vice Chairs Emeritus: Alasdair Allan, Roy Williams, John Swinbank, Mike Fitzpatrick, Dave Morris


The time domain is the emerging field of astronomical research, as recognized in the European ASTRONET and 2010 US National Research Council Decadal Survey of Astronomy and Astrophysics. Planned facilities for the next decade and beyond, both ground-based, such as the LSST and SKA, and space-based, such as CHEOPS, EChO and PLATO, will revolutionize our understanding of the universe with nightly searches of large swathes of sky for changing objects and networks of robotic telescopes ready to follow up in greater detail selected interesting sources. This will impact essentially every area of astronomy, from the Solar System to cosmology, and from stellar evolution to extreme relativistic phenomena, making it a very rich area for scientific exploration and discovery, and extending beyond the traditional electromagnetic spectrum into neutrino and gravitational wave astronomy. Moreover, many interesting phenomena, e.g., supernovae and other types of cosmic explosions, can only be studied in the time domain. The challenges lie in the automated distribution, processing, classification, and archiving of vast streams of triggers. The VO is well-placed to support and facilitate research in this area.

The IVOA Time Domain Interest Group has evolved from the IVOA VOEvent Working Group recognizing that the mechanics of celestial event notification are now broadly resolved within the VO but that broader representation of the emerging time domain community has become necessary.

It will:

  • Provide a forum for discussing time domain specific issues in a VO context.
  • Contribute to other IVOA working groups to ensure that time domain specific requirements are included.
  • Incorporate standard approaches defined in these groups when designing and implementing services on time domain archives.
  • Define standard services relevant for time domain archives.
  • Promote development of services for comparing theoretical results to observations and vice versa.
  • Define relevant milestones and assign specific tasks to interested parties.


VOEvent defines the content and meaning of a standard information packet for representing, transmitting, publishing and archiving information about a transient celestial event, with the implication that timely follow-up is of interest. VOEvent 2.0 was published as an IVOA Recommendation on 11 July 2011. The VOEvent 2.0 wiki, which was used to discuss the evolution of the standard, is still available.

Introductory Material

A tutorial introduction, based on material prepared for Hotwiring the Transient Universe IV in May 2015, is available.

The VOEvent book, "Hotwiring the Transient Universe", provides an introduction to the VOEvent system and related infrastructure. It is available in printed form from Lulu. A Kindle version is also available: do a "download file as" and drag to the documents directory on your Kindle via USB.

SkyAlert provides a web-based interface for exploring and collating VOEvents and defining personalised event alert schemes.

Dakota and Comet provide tools for connecting to high-speed TCP streams of VOEvents.

NASA Gamma-ray Coordinates Network provides a VOEvent stream of GRB and transient notices, including example source code for tools to receive messages.

VOEvent Transport

VOEvent is deliberately transport-agnostic. However, the VOEvent Transport Protocol (VTP) may be used to distribute streams of VOEvents across the internet with a relatively low latency. The following "brokers" provide access to such streams. A tool such as Dakota or Comet, below, is required to subscribe.

Address Port Organization Accessibility Comments
voevent.dc3.com 8099 DC3 Dreams Public Dakota broker "home" site, feeds GCN, 4 Pi Sky, LOFAR, others.
voevent.swinbank.org 8099 Comet Public Comet broker "home" site; deploys the latest pre-release.
voevent.transientskp.org 8099 LOFAR/Univ. Amsterdam Public  
envoy5.cacr.caltech.edu 8099 Skyalert/Caltech Public CRTS etc. Offline as of 2014-07-08.
voevent.4pisky.org 8099 4 Pi Sky Public 8099 NASA GCN Public Only GCN events; VOEvent 1.1. 8099 NASA GCN Public Only GCN events; VOEvent 1.1. 8099 NASA GCN Public Only GCN events; VOEvent 2.0. 8099 NASA GCN Public Only GCN events; VOEvent 2.0.

Tools and Libraries

Since VOEvents are XML documents, they can be manipulated with a wide range of standard tools. In addition, the following libraries and tools may be useful.

Generating, Reading and Manipulating VOEvents

  • VOEventLib is a Python library for working with VOEvent documents.
  • voevent-parse is a lightweight Python library for parsing, manipulating, and generating VOEvents.

Working with the VOEvent Transport Protocol

  • The Dakota VOEvent Tools are a cross-platform, open source set of tools which fully implement the VOEvent Transport protocol for subscriber/listener, publisher, and broker operations, as well as strict VOEvent 2.0 packet validation. Dakota includes a fully functional broker. The Dakota tools are written in portable C# and are open source.
  • Comet is a Python implementation of the VOEvent Transport Protocol. It is capable of receiving events either by subscribing to one or more remote brokers or by direct connection from authors, and can then both process those events locally and forward them to its own subscribers. In addition, Comet provides a tool for publishing VOEvents to a remote broker.
  • PyGCN is a Python-based client that anonymously listens for VOEvent format notices from the NASA Gamma-ray Coordinates Network over the VOEvent Transport Protocol.

VOEvent Databases

voeventdb, run by the 4 Pi Sky project, provides a REST interface to a database of VOEvents. See their tutorial for examples of what this makes possible.

VOEventStream: Metadata for Collections of Events


Shanghai interop 2017, discussion session for VOEvent

Time Series Data

What is "Time Series Data"? It is a temporal sequence of measurements containing a time coordinate and a flux (or similar - magnitude) / RV / position / polarisation / number of spots / spectra / images,...

Science use Cases for Time Series

TIMESYS: annotating time in VOTables

ST-MOCs: connecting space & time coverages

Astropy and TimeSeries

Some other relevant documents concerning Time Series

InterOps presentations

Virtual 2021 May

Virtual Nov 2020

Virtual May 2020

Groningen 2019

Paris 2019

College Park 2018

Victoria 2018

Santiago 2017

Shanghai 2017

Other meetings

VOEvent and GCN discussion 20 Sep 2022

Strasbourg 2017 Meeting

Strasbourg 2018 Meeting

Goal: work on the Time Series model and annotation. Summary of the meeting:

  • We have converged to one unique model for simple time series. See UML
  • We started from Gaia requirements
  • Different serialisations and annotations on VOTables are proposed:
    • VODML
    • VODML-Lite
    • Utypes
  • TIMESYS annotation in VOTables
  • We have a roadmap to provide a working prototype by end of 2019.
    • Examples based on Gaia DR2 light-curves are being built (deadline mid September)
    • These need to be properly tested by data providers and clients (deadline to start the testing loop end September)
    • Present results as a note (deadline end of October) and discuss at the next interop (mid November)
  • Detailed notes of the meeting can be found here

2020 time series proposal

A new proposal to meet a specific set of requirements Time Series 2020.

Some relevant missions concerning Time Series

Mailing List

All interested parties are welcome to join the mailing list: please use it not only suggest and discuss technical proposals, but also to explore how the TDIG can best engage with your particular science goals.

Note that the volume of "spam" subscription requests received means that legitimate ones can sometimes get lost: if you don't receive a timely receipt of your subscription, please accept our apologies and try again or contact the TDIG chair or vice chair for help.

Past Events

  • Transient Sky in 2020, 1st week of June 2018, France

  • IVOA InterOp - TDIG Session, Stellenbosch, South Africa, 11 May 2016

  • VAO All-hands meeting requires login - Charlottesville, VA, Sep 30 - Oct 1, 2010

  • SPIE AT&I, especially Obs. Ops. session 4, Orlando, May 24 - 31, 2006

  • VOEvent session at the IVOA Interoperability Meeting in Madrid, October 6 - 7, 2005

  • VOEvent session at the IVOA Interoperability Meeting in Kyoto, May 16-20, 2005


Gamma-ray Burst Coordinate Network (GCN)

Astronomer's Telegram

RTML - Remote Telescope Markup Language and Twiki here

Real Time Virtual Observatory

Space-Time Coordinate Metadata for the Virtual Observatory (STC)

Unified Content Descriptors, and more here

Resource Metdata for the Virtual Observatory

Pairitel Project

The eSTAR Project is now defunct.


Discussion leading up to the VOEvent Recommendation

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf 2013-11-14_-_Hotwired_3_Breakout.pdf r1 manage 49.6 K 2013-11-15 - 19:09 JohnSwinbank Summary slides from the TDIG breakout session at Hotwired 3
PowerPointppt ADASS2007_VOEventBoF_Auden.ppt r1 manage 307.5 K 2007-09-25 - 15:30 ElizabethAuden E. Auden's ADASS '07 BoF slides: SEAP, STAP, HPKB
Unknown file formatazw HotwiringtheTransientUniverse.azw r1 manage 3469.4 K 2011-02-17 - 03:24 RobSeaman Kindle of "Hot-wiring the Transient Universe"
PDFpdf P8-3.pdf r1 manage 860.4 K 2019-04-04 - 11:25 AdaNebot  
HTMLhtml PR-VOEvent-2.0-20110601.html r2 r1 manage 113.0 K 2011-05-28 - 23:05 RoyWilliams  
PDFpdf PR-VOEvent-2.0-20110601.pdf r1 manage 1299.6 K 2011-05-28 - 23:06 RoyWilliams  
Microsoft Word filedoc SEAP-v0.1.doc r1 manage 141.0 K 2008-10-23 - 05:54 MatthewGraham First write-up of SEAP
PDFpdf Sky_is_the_limit.pdf r1 manage 1530.9 K 2009-12-11 - 21:23 RobSeaman  
PDFpdf Strasbourg-17-20July2018.pdf r3 r2 r1 manage 413.8 K 2018-08-03 - 09:45 AdaNebot  
PDFpdf Strasbourg-TimeSeriesData-Meeting-Agenda.pdf r1 manage 202.9 K 2017-12-19 - 10:52 AdaNebot  
PDFpdf Strasbourg-TimeSeriesData-Meeting-Agenta.pdf r1 manage 202.9 K 2017-12-19 - 10:47 AdaNebot  
PDFpdf Strasbourg-TimeSeriesData-Meeting-MinimalRequirements.pdf r2 r1 manage 95.0 K 2017-12-19 - 13:34 AdaNebot  
PDFpdf Strasbourg-TimeSeriesData-Meeting-Notes.pdf r1 manage 504.1 K 2017-12-19 - 11:04 AdaNebot  
PNGpng TS_overview.png r1 manage 113.8 K 2018-07-26 - 09:07 AdaNebot  
PDFpdf TimeDomainHackAthon.pdf r1 manage 254.5 K 2017-05-17 - 04:51 FrancoisBonnarel Asterics Tech Forum discussion on Time Series
HTMLhtm VOEvent-0.1.htm r1 manage 17.6 K 2004-11-25 - 15:03 RoyWilliams VOEvent-0.1
HTMLhtm VOEvent-0.2.htm r1 manage 22.7 K 2004-11-25 - 15:04 RoyWilliams VOEvent-0.2
HTMLhtm VOEvent-0.3.htm r1 manage 31.5 K 2004-12-27 - 23:05 RoyWilliams Version 0.3
HTMLhtml VOEvent-0.90.html r1 manage 66.8 K 2005-05-13 - 16:47 RoyWilliams VOEvent 0.90
PDFpdf VOEvent-0.90.pdf r1 manage 314.1 K 2005-05-13 - 16:49 RoyWilliams VOEvent 0.90 pdf
HTMLhtml VOEvent-0.94.html r1 manage 68.2 K 2005-06-21 - 17:34 RoyWilliams  
PDFpdf VOEvent-0.94.pdf r1 manage 206.9 K 2005-06-21 - 17:35 RoyWilliams  
Unknown file formatxsd VOEvent-v0.9.xsd r1 manage 8.5 K 2005-07-06 - 18:39 RoyWilliams VOvent schema v0.9
PDFpdf VOEvent-v1.0-schema.pdf r1 manage 97.5 K 2005-07-11 - 07:06 RobSeaman Model diagram of the v1.0 schema
HTMLhtml VOEvent-v1.0.html r1 manage 70.7 K 2005-07-11 - 09:16 RobSeaman VOEvent v1.0 specification
Unknown file formatxsd VOEvent-v1.0.xsd r1 manage 7.6 K 2005-07-11 - 07:04 RobSeaman VOEvent v1.0 schema
Unknown file formatxsd VOEvent-v1.01.xsd r1 manage 7.6 K 2006-03-24 - 02:33 RoyWilliams New start on the schema March 2006
HTMLhtml VOEvent-v1.1-060425.html r1 manage 64.4 K 2006-04-25 - 14:27 RoyWilliams VOEvent 1.1 draft 060425
Unknown file formatxsd VOEvent-v1.1-060425.xsd r1 manage 6.6 K 2006-04-25 - 14:28 RoyWilliams VOEvent 1.1 schema draft 060425
HTMLhtml VOEvent-v1.1-060501.html r1 manage 65.1 K 2006-05-01 - 23:06 RoyWilliams VOEvent 1.1 draft 060501
HTMLhtml VOEvent-v1.1-060508.html r1 manage 70.9 K 2006-05-08 - 00:53 RoyWilliams Elaboration of the STC section
Unknown file formatxsd VOEvent-v1.1-060508.xsd r1 manage 6.7 K 2006-05-09 - 20:24 RoyWilliams Correct links to STC 1.30
HTMLhtml VOEvent-v1.1-060510.html r1 manage 71.7 K 2006-05-10 - 23:24 RoyWilliams corrected the STC section
HTMLhtml VOEvent-v1.1-060511.html r1 manage 73.9 K 2006-05-11 - 20:07 RoyWilliams  
HTMLhtml VOEvent-v1.1-060519.html r1 manage 74.3 K 2006-05-19 - 14:06 RoyWilliams Near final version 1.1 after IVOA
Unknown file formatxsd VOEvent-v1.1-060519.xsd r1 manage 6.1 K 2006-05-19 - 14:05 RoyWilliams Near-final schema. Change is element=unqualified.
Unknown file formatxsd VOEvent-v1.1-060808.xsd r1 manage 6.4 K 2006-08-09 - 17:50 RoyWilliams Adds "format" atrtribute to Description, etc
HTMLhtml VOEventService-0.2.html r2 r1 manage 108.5 K 2008-10-08 - 05:39 MatthewGraham  
HTMLhtml VOEventStream-0.2.html r1 manage 108.4 K 2008-10-17 - 02:37 RoyWilliams  
HTMLhtml VOEvent_transport_060412.html r1 manage 42.5 K 2006-05-11 - 20:30 RobSeaman  
HTMLhtml VOEvent_v1.1.html r3 r2 r1 manage 76.3 K 2006-06-29 - 22:22 RoyWilliams VOEvent v1.1 - IVOA Proposed Recommendation
PDFpdf VOEvent_v1.1.pdf r1 manage 232.0 K 2006-06-22 - 16:05 RobSeaman VOEvent v1.1 - IVOA PR PDF
PDFpdf adassxix_voevent.pdf r1 manage 3398.3 K 2009-10-20 - 17:20 RobSeaman Slides from ADASS XIX on transient response
PDFpdf autoBof.pdf r2 r1 manage 45.2 K 2006-10-07 - 05:15 RobSeaman Revised Agenda for Autonomous BoF
PDFpdf cubeDM.PDF r1 manage 1344.8 K 2017-11-28 - 12:36 AdaNebot  
XMLxml example1-v1.0.xml r1 manage 0.8 K 2005-07-11 - 07:13 RobSeaman Simple VOEvent XML packet
XMLxml example2-v1.0.xml r1 manage 3.2 K 2005-07-11 - 07:14 RobSeaman Typical VOEvent packet
XMLxml example3-v1.0.xml r1 manage 0.2 K 2005-07-11 - 07:17 RobSeaman Indirection packet (w/o schema)
PDFpdf gray-bof-vocabularies.pdf r1 manage 104.2 K 2007-09-25 - 07:40 NormanGray Norman Gray's vocabularies talk, ADASS VOEvent BoF
XMLxml ivo_GCN_swift_20250563a_20060323_073655.xml r1 manage 2.1 K 2006-03-25 - 00:32 RoyWilliams Talons event using 1.01 schema
Compressed Zip archivetar noao_posters.tar r1 manage 4880.0 K 2009-12-03 - 09:18 RobSeaman posters from various meetings (by P. Marenfeld)
PDFpdf obs_agent.pdf r1 manage 14218.2 K 2008-11-10 - 19:00 RobSeaman Slides from ADASS on agents (w/ bonus topic)
XMLxml pointer.xml r2 r1 manage 0.4 K 2005-07-06 - 21:36 RoyWilliams VOEvent example that just points to another
XMLxml simple.xml r3 r2 r1 manage 0.8 K 2005-07-07 - 22:18 RoyWilliams Simple VOEvent example
XMLxml typical.xml r5 r4 r3 r2 r1 manage 3.1 K 2006-03-25 - 00:30 RoyWilliams Packet that uses 1.01 schema
HTMLhtml voevent_v2.html r1 manage 95.9 K 2010-09-30 - 14:58 RobSeaman initial VOEvent v2.0 working draft
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