According to Bhāgavatapurāṅa, Ātapa is one of the sons born out of the womb of Ūṣā (Usha), sired by Vibhāvasu (Vibhavasu). He is the father of the god called Pañcayāna (Panchayana).

Bhāgavatpurāṇa Vols. 1-12(66.16)