Observations of the First Electromagnetic Counterpart to a Gravitational-wave Source by the TOROS Collaboration

DÍAZ, M. C.; MACRI, L. M.; LAMBAS, D. GARCIA; OLIVEIRA, C. MENDES DE; CASTELLÓN, J. L. NILO; RIBEIRO, T.; SÁNCHEZ, B.; SCHOENELL, W.; TOROS COLLABORATION; LARES, MARCELO

The Astrophysical Journal

IOP Publishing

Lugar: Philadelphia; Año: 2017 vol. 848

We present the results of prompt optical follow-up of the electromagnetic counterpart of the gravitational-wave event GW170817 by the Transient Optical Robotic Observatory of the South Collaboration. We detected highly significant dimming in the light curves of the counterpart (Delta g = 0.15 mag, Delta r = 0.14 mag, Delta i = 0.10 mag) over the course of only 80 minutes of observations obtained ~35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59 hr after the event with the EABA 1.5 m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a "blue kilonova" relatively free of lanthanides.