Difference between /o/ and /ō/ in Aryanpur transcription

[qzhqzh]

I'm using the Aryanpur Progressive English-Persian Persian English dictionary and noticed that the short vowel /o/ is transcribed two different ways in the phonetic transcription, /o/ and /ō/.

Examples:

/o/ = ترب torob

/ō/ = همین‌طور hamintōr

I'm guessing that the /ō/ is used to indicate that the vowel was originally the dipthong /ow/, which has been simplified to a lengthened /o:/ in modern Teherani?

Follow-up question: Is this /ō/, such as in همین‌طور hamintōr or نو nō noticeably pronounced as a lengthened /o:/ in normal Tehanri speech, or is it only lengthened in "careful" speech?

[eskandar]

I'm guessing that the /ō/ is used to indicate that the vowel was originally the dipthong /ow/, which has been simplified to a lengthened /o:/ in modern Teherani?

Exactly.

Follow-up question: Is this /ō/, such as in همین‌طور hamintōr or نو nō noticeably pronounced as a lengthened /o:/ in normal Tehanri speech, or is it only lengthened in "careful" speech?

I think it varies between speakers. In 'authentic' Tehrani speech I think the distinction between the two has totally collapsed. Even in careful/formal speech it might just be [o] with no sign of [o:] or [ow], unless one is reciting poetry. However the distinction is preserved in other dialects, and it's worth noting that there are millions of people living in Tehran whose origin is from elsewhere in the country; they generally claim their accent is "Tehrani" but still maintain subtle influence from their original region's accent or dialect. That's partly why it may vary from person to person.