This is twice in four months. First was the detection last September that was announced in February. This detection occurred in December, and was announced today in a press conference and a published paper. Two instances is not enough to establish a trend, but it suggests that we might at some point have four or more detections a year, if we get to running the detectors all or most of the time. As it is, the last science run ended in December, and the next one will start in the autumn.
Now, how about some neutron stars?
For second time, LIGO detects gravitational waves
Astronomy Picture of the Day: GW151226: A Second Confirmed Source of Gravitational Radiation
Physical Review Letters: GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence
This black hole pair is 1.4 GLY (billion light years) away from Earth.
Press Conference has just started. More to come.
Update 1:
The inferred source-frame initial black hole masses are 14.2(+8.3 −3.7)M⊙ and 7.5(+2.3 −2.3)M⊙, and the final black hole mass is 20.8(+6.1 −1.7)M⊙.
Update 2:
LIGO Science Collaboration: GW151226: Observation of Gravitational Waves from a 22 Solar-mass Binary Black Hole Coalescence
Update 3: A report on the press conference.
Gravitational waves spotted for a SECOND time: Scientists make 'spectacular' new detection of ripples in space-time