Science frontiers for SKA-VLBI

The e-EVN has pioneered/implemented real-time electronic very long baseline interferometry (e-VLBI) operations during the past ten years, providing the technological roadmap and setting an operational example for very high resolution observations with SKA1-mid, for short SKA-VLBI. Besides providing very sensitive long East-West baselines to Australia, and North-South baselines to Europe, SKA-VLBI will excel in calibration, by the ability to use multiple faint sources sources (down to about a mJy) within the primary beam of the telescopes. This technique will have the advantage of delivering ultra-precise relative astrometry (among others).

A recent example of what could be done routinely with SKA-VLBI was demonstrated by three years monitoring of the first jetted tidal disruption event (TDE) with the European VLBI Network. This type of extragalactic transients are extremely interesting because they light up dormant galactic nuclei, allowing us to study a hitherto unknown massive black hole population, and the impact of their new-born jets on the host galaxy. The EVN monitoring of the radio counterpart to Swift J1644+5734 achieved an astrometric accuracy of about 10 microarcseconds (unprecedented for faint continuum sources with the EVN) using an in-beam radio source as the astrometry reference point (Yang et al. 2016, MNRAS 462, L66). The upper limit on the apparent jet proper motion is 0.27c, constraining the intrinsic jet speed as a function of viewing angle (Fig. 1).


Figure 1. Left: Constraints on Swift J1644+5734 average intrinsic jet velocity βint and Lorentz factor for various viewing angles, from the proper motion upper limit (red line). Right: EVN image of the radio counterpart to the first jetted Tidal Disruption Event J1644+5734, and the in-beam astrometry reference source (Yang et al. 2016).

Nanoradians on the Sky: VLBI Across the Mediterranean and Beyond

The SKA VLBI working group organised a special session during the EWASS conference in Athens (4-8 July 2016) to address various key science areas for SKA-VLBI. The topics were astrometry, continuum surveys, and transients. During this meeting astrometry of pulsars and star forming regions, surveys of low-luminosity AGN, and among transient phenomena TDE, and fast radio bursts were highlighted. Related technical issues were discussed as well, like multi-source calibration, the limitations due to the small number of SKA1-mid VLBI beams available, and the requirements for being able to carry out triggered VLBI observations. The various science and technical topics were further discussed during the VLBI breakout session during the SKA KSP workshop in Goa (7-11 November 2016).


Figure 2. Poster for the “Nanoradians on the Sky” special session during EWASS 2016 in Athens.

Jumping JIVE

The Joint Institute for VLBI in Europe has transformed into a European Research Infrastructure Consortium (ERIC) during the past year. As an ERIC, JIVE has strengthened its position as a European institute. At the same time, the EVN expands further. During the EVN Consortium Board of Directors meeting in Riga it has been decided that Irbene joins the network, and Latvia is committed to join JIVE as well.

As for SKA-related activities, JIVE is involved in the signal data transport (SADT) consortium, and we are playing a leading role in the SKA VLBI working group. The Horizon2020 project Jumping JIVE will commence in 2017. It has two work packages especially relevant for SKA-VLBI. In the framework of the ’Integrating new elements’ work package we will start fringe tests in early 2017 with the Kuntunse telescope in Ghana, that will become part of the African VLBI Network (AVN). Our SKA-VLBI work package will support the VLBI working group. A Jumping JIVE liaison person in the SKA Office will work on the policies that will allow for an operational SKA-VLBI network, and she/he will investigate the options for commensal SKA-VLBI operations – which is very relevant to the science cases described above.

Report provided by the Zsolt Paragi