Locating Astrophysical Transients


New generation wide-field instruments, especially SKA pathfinders in the radio regime, will detect a huge number of transient sources that can be followed-up by the very long baseline interferometry (VLBI) technique at the highest possible angular resolution. The main goal of the workshop was to bring together researchers with various backgrounds to review the status of the transient science field, with a special focus on the radio band and VLBI.  How to find and localize transients, how to make the best use of a multi-band approach, and how to improve the operations of the European VLBI Network (EVN).


The sessions were organized around topics like X-ray binaries, supernovae, gamma-ray bursts etc., each followed by a discussion session to identify the key scientific questions in the field, and the areas where radio (VLBI) observations could contribute the most. A special session was dedicated to the progress of automated triggering of the EVN and similar projects at other arrays. The NEXPReS eVSAG (e-VLBI Science Advisory Group) had a closed business lunch on 16 May, to discuss the inputs received from the participants on how to improve e-EVN operations. The last day was for presenting the latest results from other SKA pathfinders, and for a brief outlook to the future of VLBI in the SKA era.


The first success of the workshop was the great number of participants that registered; unfortunately we had to make a down-selection and reject some excellent researchers in the field. The second success was the lively atmosphere (within the discussion sessions and in the breaks) which certainly played a great role in the forming of new collaborations during the week. These collaborations meant groups actually working on observing proposal ideas, but also plans were formulated on how to bring the various communities closer (e.g. XMM-EVN, INTEGRAL-EVN). As a direct output, the eVSAG has prepared an 11 page workshop summary with recommendations to be submitted to the EVN Programme Committee and the EVN Consortium Board of Directors.


The most important scientific result presented was the discovery of 4 new Lorimer-type fast transients (by Dan Thornton). In general, finding and localizing fast transients featured in a number of talks, to the pleasant surprise of the organizers.

Another important result discussed on the corridors was the parallax distance determination of the dwarf nova system SS Cyg using triggered EVN and VLBA observations (appeared in Science just a few days after the workshop; published by the team lead by James Miller-Jones). But there were several other occasions when mobile phone cameras took snapshots of “secret” slides shown during the presentations.

The format of the workshop perfectly suited our goals, we would organize the sessions almost exactly the same way next time. We found that a discussion session for the morning and one for the afternoon is sufficient; those sessions that were left “free-floating” were usually much more productive than the well-organized ones that were sometimes dominated by the discussion leader a bit too much. The local organization was just excellent. It was a huge relief to be able to connect a review speaker (who had to cancel on a short notice) through Skype in the very first session, and see that everything works beautifully.


We expect to see a number of new results resulting directly from this workshop. The first of these have already been published. A newly-formed group teamed-up to observe a new type of AGN outburst (not even covered in the workshop topics) with the e-EVN. The first results were reported in an Astronomer's Telegram (Atel #5125, by Jun Yang et al.).


We thank to the Lorentz Center for this fantastic experience, and to RadioNet3 and NEXPReS for additional support.