Two long-period X-ray pulsars detected in the SMC field around XTE J0055-727

Abstract

An XMM-Newton target of opportunity observation of the field around the transient 18.37 s pulsar XTE J0055-727 in the Small Magellanic Cloud (SMC) revealed two bright, long-period X-ray pulsars in the EPIC data. A new pulsar, XMMU J005517.9-723853, with a pulse period of 701.7 ± 0.8 s was discovered and 500.0 ± 0.2 s pulsations were detected from XMMU J005455.4-724512 (=CXOU J005455.6-724510), confirming the period found in Chandra data. We derive X-ray positions of RA = 00h54m55.88s, Dec = -72°45'10.5'' and RA = 00h55m18.44s, Dec = -72°38'51.8'' (J2000.0) with an uncertainty of 0.2 arcsec utilizing optical identification with OGLE stars. For both objects, the optical brightness and colours and the X-ray spectra are consistent with Be/X-ray binary systems in the SMC.

Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member states and the USA (NASA).