The detection of the Gravitational Wave by the LIGO-VIRGO observatory network, as well as a gamma-ray source, on 17 August 2017 has resulted in one of the largest Target of Opportunity campaigns at ESO. Observations with several La Silla Paranal Telescopes led to the discovery of the first electromagnetic counterpart of a Gravitational Wave event. In addition, the Observatory carried out mid-infrared imaging with NACO (in the L' band) and VISIR (at 8.9 microns), albeit no source was detected. ESO and several of the observing teams involved have now made their datasets from this event publicly available.

All NACO and VISIR raw images, as well as reduced data from VISIR are publicly available through the ESO Science Archive under programme ID 60.A-9392. The VISIR data release includes coadded images and error maps and is accompanied by a comprehensive description.

The following Principal Investigators have kindly agreed to waive the proprietary periods for their programmes in order to make their raw data publicly available to the whole community through the ESO Science Archive:

• SOFI and EFOSC at NTT observations taken within the ePESSTO programme (ID 199.D-0143, PI: S. Smartt).
• VIRCAM at VISTA observations taken as part of the ESO Public Survey VINROUGE (ID 198.D-2010, PI: N. Tanvir).
• FORS2 at VLT observations taken within programme ID 099.D-0116 (PI: S. Covino).
• GROND at Max Planck 2.2m telescope observations taken within programme ID 99.A-9025 (PI: A. Rau).
• X-shooter at VLT observations taken within programme ID 099.D-0376 (PI: S. Smartt).
• NACO and VISIR at VLT observations taken within programme ID 60.A-9392 (PI A. Kaufer).

Image: Montage of X-shooter spectra showing changes in the kilonova in NGC 4993 over 12 days.
Image credit: ESO/Pian et al./Smartt & ePESSTO.