LIGO Detected Primordial Black Holes?

In September 2015, gravitational waves (GWs) were detected for the first time by the LIGO detectors, the two laser interferometers in the United States. It was found that detected GWs originate from the coalescence of two black holes (BHs) in a binary, each weighing about 30 times the mass of the Sun (30 solar mass). Although there have been indirect observations of BHs in the X-ray binaries, their masses are at most 15 solar masses.