New religious movements are one of my areas of research focus. In fact, this website's domain name (nrms.net) comes from the term "new religious movement" (NRM). During the 1970s, scholars coined the phrase “new religious movement” because the former terms of “cult” and “sect” had lost their sociological distinction and become pejorative labels. The new term has enabled scholars of new religious movements to continue our work without casting value judgments on the groups that we study. I use the term with historical awareness, recognizing that “new” is a slippery concept, and that most new groups claim ancient lineages.
In addition to Heaven's Gate, I have researched several other NRMs of the American counter-culture (notably the Unification Church and the Hare Krishnas), as well as Scientology. I have also studied schismatic (alternative) Catholic groups. Complete information is available on my cv (http://www.uofr.net/~zeller/cv.pdf), and many of my articles are available on academic.edu (https://lakeforest.academia.edu/BenjaminZeller), requires free subscription.
One of the best resources for the study of NRMs is the journal Nova Religio: The Journal of Alternative and Emergent Religions, of which I serve as a co-general editor. Details are available on the Nova Religio website (novareligio.org). Academic users can access back issues on JSTOR and ATLA. Current issues require a subscription, generally through a university library.