SIMBAD query result

Please have a look at the "Dictionary of Nomenclature"

Result of query: info cati RXJ 1624.9 7554

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 [Class]      Acronym  (Explanation)   . . . . . . . . . in Simbad, use:
 [X]          RXJ (ROSAT sat. (X), J2000)  . . . . . . . RX JHHMM.m+DDMM
                                                      or RX JHHMMSS+DDMMm
                                                      or RX JHHMMSS.s+DDMMSS