Radio telescopes zoom in gravitational wave counterpart

© LIGO-Virgo Consortium (image); ASTRON, JIVE

Last year we learned about the birth of the new field of gravitational wave astronomy, when gravitational waves were first detected from merging stellar-mass black holes. Yesterday, on 16 October 2017, the LIGO-Virgo Consortium (LVC) and various observatories made another major announcement: the first detection of gravitational waves from merging neutron stars. Such events are particularly interesting to astronomers because the matter ejected during this type of merger is expected to become bright in various parts of the electromagnetic spectrum, including at radio wavelengths. That is, we can study these phenomena in detail with observations from our 'ordinary' telescopes.

The LVC was well prepared: they made agreements to a great number of observing facilities and astronomy groups several years ago. When the event GW170817 was detected on 17 August this year, it was immediately followed up by our telescopes. This resulted in another milestone discovery: the detection of an electromagnetic transient counterpart resulting from the explosive processes that followed the inspiral and merging of the two neutron stars. The arXiv preprint server was flooded yesterday by the scientific results from this discovery.

One particular paper summarizes the events from the gravitational wave detection and localization, as well as all the additional observations with different telescopes. This paper was put together in a collaborative effort by approximately 70 contributing groups. This paper has about 3500 authors affiliated to more than 900 institutions, demonstrating how global this collaboration was.

Our JIVE and ASTRON colleagues took part in the follow-up program. The ASTERICS initiated Euro VLBI team has observed the transient at centimetre wavelengths with the UK-based e-MERLIN, and with the European VLBI Network (EVN), at a number of epochs. The LOFAR team observed part of the LVC localization footprint at metre wavelengths. The radio emission is still very faint and we could not detect it with our (very) long baseline interferometers, but we expect the source to brighten in the coming weeks. The image therefore shows the LVC localization of the GW170817 event, together with the localization of the related short gamma-ray burst detected by Fermi, as well as the first optical image (and a pre-discovery image) of the transient now called SSS17a.

Zsolt Paragi for the Euro VLBI team

Jess Broderick and Antonia Rowlinson for the LOFAR team