GW150914: First search for the electromagnetic counterpart of a gravitational-wave event by the TOROS collaboration

MARIO C. DÍAZ; MARTÍN BEROIZ; TANIA PEÑUELA; LUCAS M. MACRI; RYAN J. OELKERS; WENLONG YUAN; DIEGO GARCÍA LAMBAS ; JUAN CABRAL; CARLOS COLAZO; MARIANO DOMINGUEZ; BRUNO SANCHEZ; SEBASTIÁN GUROVICH; MARCELO LARES

The Astrophysical Journal Letters

IOP Publishing for the American Astronomical Society

Año: 2016

We present the results of the optical follow-up conducted by the TOROS collaboration of the firstgravitational-wave event GW150914. We conducted unfiltered CCD observations (0.35 − 1µm) withthe 1.5-m telescope at Bosque Alegre starting ∼ 2.5 days after the alarm. Given our limited field ofview (∼ 100ut0), we targeted 14 nearby galaxies that were observable from the site and were locatedwithin the area of higher localization probability.We analyzed the observations using two independent implementations of difference-imaging algorithms,followed by a Random-Forest-based algorithm to discriminate between real and bogus transients.We did not find any bona fide transient event in the surveyed area down to a 5σ limitingmagnitude of r = 21.7 mag (AB). Our result is consistent with the LIGO detection of a binary blackhole merger, for which no electromagnetic counterparts are expected, and with the expected rates ofother astrophysical transients.