This can be translated as a direct quotation. Alternate translation: "men, and he asked them, 'When exactly did this star appear?'" (See: [[rc://en/ta/man/translate/figs-quotations]])
It is implied that the learned men told him when the star appeared. Alternate translation: "what time the star had appeared. The learned men told Herod when the star first appeared" (See: [[rc://en/ta/man/translate/figs-explicit]])