Exploring Time Domain Multi-Messenger Astronomy through the Virtual Observatory
What do Cepheid stars, Binary Neutron stars, Supernovae explosions and Active Galactic Nuclei have in common? They are all variable objects, although the physical processes and the associated time-scales that govern their variability can be very different (pulsations, collapse, accretion, bursts, … with characteristic time-scales from milliseconds to hundreds of years). Some events can trigger follow-up observations and a fast reaction to those events can be crucial to determining the nature of the object. To better understand the nature of these objects and the mechanism behind the source of variation a multi-wavelength and even multi-messenger approach is often needed. In 2017 for the first time there was a direct detection of gravitational waves and electromagnetic emission from colliding neutron stars. The discovery involved more than 70 ground and space based telescopes and more than 3000 astronomers. GW170817 beyond being of great relevance by its own illustrates at the highest level the need from the Time Domain Astronomy community to transmit events, collect and share information and to coordinate observations. The Virtual Observatory (VO) should match the common needs of the different scientific use cases. In this paper, we give some highlights of the work on enabling Time Domain Astronomy in the VO, and coordinating the international effort in IVOA, part of which has been done within the ASTERICS DADI package. This includes standards for spatial and temporal coverage, and Time Domain data as will be needed for Time Domain Multi-Messenger Astronomy. Other highlights include prototype visualisation tools taking into account the temporal dimension, and tools for fast cross-matching.