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

DÍAZ, M. C.; MACRI, L. M.; LAMBAS, D. GARCIA; RODRIGUEZ, H.

The Astrophysical Journal

The American Astronomical Society

Año: 2017 vol. 848

We present the results of prompt optical follow-up of the electromagnetic counterpart of the gravitational-waveevent GW170817 by the Transient Optical Robotic Observatory of the South Collaboration. We detected highlysignificant dimming in the light curves of the counterpart (Dg = 0.17  0.03 mag, Dr = 0.14  0.02 mag,Di = 0.10  0.03 mag) over the course of only 80 minutes of observations obtained ∼35 hr after the trigger withthe T80-South telescope. A second epoch of observations, obtained ∼59 hr after the event with the EABA 1.5 mtelescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that thisevent was a ?blue kilonova? relatively free of lanthanides.