In the AtharvaShira Upanishad (32/3), we get
yat param brahma sa ekah, ya ekah sa rudrah yo rudrah sa ishAno ya ishAnah sa bhagavan maheswarah. Meaning the absolute Brahman is One, He is nemed as Rudra, Ishana and Maheswara.
Yes, the sense is the same.In Srimad-Bhagavatam also we get that the same Advaya (One without a Second) Tattva is named Brahman and Bhagavan.
vadanti tat tattva-vidas
tattvaṁ yaj jñānam advayam
bhagavān iti śabdyate
The name Mahadeva of Bhagavan is mentioned in Srimad-Bhagavatam (11/12/3).
The definition of Bhagavan as the Absolute Brahman is present in many puranas including Vishnu-purana.
The Vishnu-Purana says about Bhagavan Vishnu :
Is Visnu merely the lord of protection and preservation? He is the embodiment of the divine Principle that permeates the entire universe in which the world-play of creation, preservation and dissolution is enacted. He ‘abideth in all.’ He is ‘all’. He assumes all forms (vide Vishnu purana 1.12.71)