Notes on VOEvent

VOEvent is the International Virtual Observatory Alliance (IVOA) recommended mechanism for describing astronomical transients. Specifically, the VOEvent standard (Seaman, 2011)

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.

This document provides an introduction to working with VOEvents. It is not normative; rather, it represents the authors’ own particular biases and experiences. This material is intended to accompany the “VOEvent Hands-On Session” presented at Hot-Wiring the Transient Universe IV (henceforth “Hotwired 4”) in May 2015; we hope, though, that it will prove generally useful.

We assume a working knowledge of Python.

• What is a VOEvent and why would I want one?
  • The transient deluge
  • The VOEvent standard
  • Distributing VOEvents
  • Higher level functionality
• Finding and installing useful tools
  • Background and dependencies
  • Reading and writing VOEvents: voevent-parse
  • Sending and receiving VOEvents: Comet
  • An alternative approach: containerization
• A look inside a VOEvent
  • Overall structure
  • Event roles
  • IVORNs and identifiers
  • Unified Content Descriptors
• Manipulating VOEvents in code
  • Parsing a VOEvent
  • Creating a VOEvent
• Subscribing to VOEvent streams
  • A VOEvent Transport Protocol primer
  • Subscribing to a broker
  • Acting on events received
  • Filtering event streams
• Distributing VOEvents
• Future challenges
  • Authentication and verifiability
  • Discoverability
  • Scalability of VOEvents and VTP
  • XML as an event format
  • High level infrastructure and scientific understanding
• Bibliography