Arya are those who sincerely and consistently practice Dharma.

According to the Chapter 16 Verse 6 of the Gita, there are only two types of beings on this earth – Those with Divine qualities and those with Demonic qualities.

The ones with divine qualities are the ones who are Arya.

Divine Qualities:

Bhagavad Gita(Chapter 16 Verses 1-3)

(1) The Blessed Lord said: Fearlessness, purity of mind, wise apportionment of knowledge and concentration, charity, self-control and sacrifice, study of the scriptures, austerity and uprightness.

(2) Non-violence, truth, freedom from anger, renunciation, tranquility, aversion to fault finding, compassion to living beings, freedom from covetousness, gentleness, modesty and steadiness (absence of fickleness).

(3) Valour, forgiveness, fortitude, purity and cleanliness, freedom from malice, envy and excessive pride – these, O Pandava (Arjuna), are the endowments of him who is born with the divine nature.

(5) The divine endowments are said to make for deliverance and the demoniac for bondage. Grieve not, O Pandava (Arjuna), thou art born with the divine endowments (for a divine destiny).

In addition to the above, other qualities of Arya are those who consistently practice what I have figured out.