Object-happiness (viṣaya-ānanda) is a name given to a phenomenon that naturally occurs in the subtle body.
Brahman is of the nature of sat-cid-ānanda (Existence-Awareness-Bliss).
Although Brahman pervades the entire world/universe (jagat) as its substratum (adhiṣṭhāna) – the manifestation of its nature varies from object to object.
The inert objects (eg: rock) of the world fully manifest only as Existence (sat).
The sentient subtle bodies (animals, humans) in the world fully manifest as Existence-Awareness (sat-cit).
Existence-Awareness-Bliss (sat-cid-ānanda) is only fully manifest in an subtle body that is predominated by sattva guna (pure reflector of Original Consciousness).
The subtle body becomes predominated by sattva when it is without any pursuit (like goals, desires, fears, wishes).
The subtle body is without pursuit when it attains a desired object that it was pursuing.
For example, when the man gets the girl, his pursuit disappears because the object of desire was attained. Hence his subtle body is predominated by Sattva, therefore experiences viṣaya-ānanda. Or person gets a raise, job.
Thus since the attainment of an object brings about a state of the subtle body in which it is able to manifest the bliss of the Self (brahma-ānanda), the manifested bliss is called object-happiness (viṣaya-ānanda).
The manifestation of brahma-ānanda (bliss of the Self) in the subtle body is a natural phenomenon.
It happens in every subtle body, including the subtle body of a jñānin (Enlightened person).
Therefore, a jñānin also experiences object-happiness.
The difference between an ajñānin (ignorant person) and a jñānin is that the ajñānin concludes that the happiness is coming from the object, while the jñānin knows that the same happiness is simply a manifestation of his own nature .
Thus while the ajñānin actively seeks objects, mistaking it to be the source of happiness… a jñānin only experiences object-happiness as an incidental phenomenon.
1) Excerpts from Vichara Sagara – A Nineteenth Century Vedanta Text