To determine the P. argus from the two other Plebejus species in Lower Austria you need to look at the fore-tibia of the Male species. If it has a spine it's P. argus.

If it hasn't a spine, it could be either P. idas or the P. argyrognomon, which only can be determined using genitalia preparation of the Male.

This is a female, so it could be any of the 3 species. 

Females of the P. idas and P. argyrognomon often has a clear sprinkel of blue on the upperside wings.