How do I remove chapter heading "before" text from bibliography header?

In LO 5.0 on a mac.
I have a multi-doc book with a master doc and many chapters.
Each chapter I have its title as a “heading 1” with before text of "Chapter ".
I have a bibliography and alphabetical index in the master doc.
The para style for each of these are a “Heading 1” and they appear in the TOC
with correct page numbers.
so far so good.
Unfortunately the headings in both the Alphbetical index and Bibliobraphy & their
TOC entreis appear with the prefix of “Chapter 17” and “Chapter 18” (as do the other real chapters).
How do I remove this “Chapter” prefix? When “editing” the master doc, it won’t let me actually edit.
thanks!