[T-A]

Dark matter, quite possibly:

https://astrobites.org/2017/08/31/could-dark-matter-be-black...

http://aasnova.org/2017/09/27/can-ligo-find-the-missing-dark...

[QAPereo]

http://resonaances.blogspot.com/2016/06/black-hole-dark-matt...

http://4.bp.blogspot.com/-jnY74NBc7ic/V2UcuCswL-I/AAAAAAAAB7...

The odds are still very low on MACHO's as a source of most dark matter.