During the Gupta period, there were several great astronomers and mathematicians who made significant contributions. Option 1, Bhanugupta, is not the correct answer as there is not enough historical evidence to suggest that he was a prominent astronomer or mathematician during the Gupta period. Option 2, Vagabhatta, is also not the correct answer as there is no significant information available about him in relation to astronomy or mathematics during the Gupta period.

Option 3, Aryabhatta, is the correct answer. Aryabhatta was a renowned astronomer and mathematician who lived during the Gupta period. He made important discoveries and calculations in the field of mathematics, including the concept of zero and the approximation of pi. He also developed a comprehensive understanding of astronomy and made significant contributions to the study of planetary motions.

Option 4, Varahamihira, was another prominent astronomer and mathematician during the Gupta period. Although he made significant contributions to the field, he is not the correct answer in this case.

Therefore, the correct answer is option 3, Aryabhatta, as he was one of the great astronomers and mathematicians during the Gupta period.