Journal paper and conference proceedings note appear to be identical, is this plagiarism?

I am looking at these two papers in the field of astrophysics. One is this journal paper and the other is a proceedings notes from a conference.

It almost looks like these two papers are copied word-for-word, with the exception of Equation 4.24 in paper 1 (although I guess considering the flow of things, it should maybe correspond go Equation 61 in the second paper). Is this plagiarism? I understand that it varies from field to field. How does one go about determining whether it is?

Two issues:

1. 
   

   The latter journal article does not cite the proceedings notes.

   
   


2. 
   
   

   The latter journal includes two authors (the proceedings notes has only one author), and the newly appearing person is listed as the first author.

   
   

I guess this highlights the ethics issues which aren't brought up often enough.