SIMBAD query result

Please have a look at the "Dictionary of Nomenclature"

Result of query: info cati 2XMM J193938.5-305704

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 [Class]      Acronym  (Explanation)   . . . . . . . . . in Simbad, use:
 [X]          2XMM (Second XMM-Newton X-ray source catalogue)  2XMM JHHMMSS.s+DDMMSS