Authors are allowed to post a preprint version of their article on arXiv: http://www.elsevier.com/journal-authors/author-rights-and-responsibilities#author-posting
The journal is subscription based and modestly priced: http://store.elsevier.com/product.jsp?issn=22131337
Authors can publish Open Access by paying a flat fee of USD 2200 per article: http://www.elsevier.com/journals/astronomy-and-computing/2213-1337/open-access-optionshttp://www.elsevier.com/journals/astronomy-and-computing/2213-1337/open-access-options