15 months from event to publication
Your metadata has one data point, so hardly sufficient to spot trends.
But looking at the paper (it's
available on arxiv), one notes that it has hundreds of authors - I didn't count how many (I estimate 1200), but the list of authors and their affiliations is enough to fill six whole pages! One could imagine them all squabbling amongst themselves for the full fifteen months about whether a colon or semicolon should be used in a particular sentence, or what shade of blue should be used in a graph. But I jest...
So, the paper is a report, not of new data, but of tests of General Relativity using older data, and one can easily imagine leisurely communications taking place between many of the authors, where they express an interest or idea on this or that constraint on GR, using various aspects of the data from the GW170817 event. Eventually, there would be enough momentum to propose a paper collecting these various threads of thoughts into a cogent whole, the end result being this paper. Fifteen months sounds about right for that, especially considering that many of the authors would probably have teaching duties and other research interests.
But do I detect a note of frustration in your post? Is it the case that having to wait so long between events and publication of papers on those events is causing you concern or anxiety? Do you feel, as a member of the public who has a particular interest in these topics, that you have some kind of special claim on their publishing as soon as is physically possible?
If so, then I would respectfully suggest that you, and others who may feel the same way, calmly consider the idea that publishing of scientific papers takes just as long as it takes, and we all just have to wait until the papers emerge into the light of day.
