B How is LIGO doing?

Quoting myself from an earlier discussion. A-LIGO is still down for upgrades for the O3 run scheduled in the autumn.

 

Also the wiki page you linked to links to https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations which answers your first questions.

 

I really like the attached graphic, which shows the LIGO/VIRGO detected events and how the BH/NS masses compare to objects detected by other means.

 

I'm not really sure, but I don't think the horizontal axis means anything. The objects are just spread out to differentiate them. The arrows indicate the mergers.

 

Interestingly, the 7 July 2017 news release from LIGO (https://www.ligo.org/news.php) references eight candidate detections, although it's not clear whether that number includes the four detections (or five, if you count the not-sufficiently-statistically-significant event LVT151012) which had already been made public at that time. Since then, only two further detections have been made public. It would be nice to know if there are candidates still being worked on, or if they didn't pan out.