What is the proper form of the word "Dunedain"?

Question

I have always assumed that the word in question should be written "Dúnedain", but in reading The Hunt for the Ring in Unfinished Tales, I came across a puzzling passage:

Night was waning on the twenty-second day of September when drawing together again they came to Sarn Ford and the southernmost borders of the Shire. They found them guarded for the Rangers barred their way. But this was a task beyond the power of the Dúnedain; and maybe it would still have proved so even if their captain, Aragorn, had been with them. But he was away to the north, upon the East Road near Bree; and the hearts even of the Dûnedain misgave them. Some fled northward, hoping to bear news to Aragorn, but they were pursued and slain or driven away into the wild. Some still dared to bar the ford, and held it while day lasted, but at night the Lord of Morgul swept them away, and the Black Riders passed into the Shire....

Which of these renderings is correct? Is it "Dúnedain" or "Dûnedain"? Is there a difference, however subtle?

Bonus points for explaining why Tolkien used two versions of the word in a single paragraph.

Answer 1

My edition of Unfinished Tales (Houghton-Mifflin, 1980) reflects the situation you see, with an acute accent ú the first time and a circumflex û the second. Christopher Tolkien, in the notes following the primary version of the story "The Hunt For The Ring", dates this text to the period between the release of the first volume and that of the third, i.e. to somewhere in the period late 1951–mid 1954.

In Appendix E to The Lord of the Rings, which among other things discusses the Elvish languages, and the writing systems (both Elvish and Roman alphabet) used to represent them, Tolkien makes the following statement:

Long vowels are usually marked with the 'acute accent', as in some varieties of Fëanorian script. In Sindarin long vowels in stressed monosyllables are marked with the circumflex, since they tended in such cases to be specially prolonged; so in dûn compared with Dúnadan. [Tolkien clarifies in a footnote: "So also in Annûn 'sunset', Amrûn 'sunrise', under the influence of the related dûn 'west', and rhûn 'east'."]

(emphasis added)

Similarly, the Silmarillion's "Note on Pronunciation" states:

A circumflex accent in stressed monosyllables in Sindarin denotes the particularly long vowel heard in such words (thus Hîn Húrin).

The Appendix E note, of course, dates shortly after "The Hunt For The Ring"; I don't know the date for the "Note On Pronunciation". But I see no particular reason to believe that the ideas present here didn't exist already at the time of the writing of "The Hunt For The Ring". I conclude therefore that Dûnedain is a misprint for the more correct Dúnedain. It is either a misprint in one particular edition, not caught by the proofreader, or else a slip on the part of Tolkien (father or son)—especially in light of the dûn-Dúnadan comparison drawn in Appendix E.