I think in most of the USA, "bot", "lot", "cot", "not", and "father" all share the same vowel, while "bought", "lost", "caught", "nought", and "fought" all share a different vowel.

The following wikipedia article discusses the two phonemes and how they are merged in many dialects of english, and contains audio samples of the same guy pronouncing both words.

https://en.wikipedia.org/wiki/Cot%E2%80%93caught_merger#Nort...