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Archival ROSAT observations of the newly discovered X-ray Pulsar IGR J22534+6243 and its period derivative

ATel #4241; G. L. Israel (INAF-OAR), G. Rodriguez (Univ. Roma "La Sapienza") report on behalf of a larger collaboration
on 7 Jul 2012; 15:20 UT
Credential Certification: GianLuca Israel (gianluca@mporzio.astro.it)

Subjects: X-ray, Binary, Neutron Star, Pulsar

Referred to by ATel #: 4248

46.6s pulsations from CXOUJ225355.1+624336 were independently detected within the CATS@BAR (ChAndra Timing Survey at Brera And Rome astronomical observatories) project aimed at the search for coherent signals among the serendipitously detected X-ray sources in the archival Chandra fields.

As reported in ATel \#4240 the signal is detected in each Chandra pointing where the source is detected. A phase-coherent fitting algorithm allows us to derive a best period of 46.6610(1)s at 1 sigma c.l.

The source was also detected by Swift XRT and in ROSAT PSPC. The Swift observations have been already reported in ATel \#4240. We found a best period of P=46.6148(6)s based again on a phase-coherent fitting procedure.

ROSAT observed the field of the pulsar on 18-19 June 1993 for a total exposure time of about 18.5ks. The signal is clearly detected at a period of 46.406s (1sigma c.l. inferred with a not phase-coherent technique).

The three (AXAF, SWIFT and ROSAT) values allowed us to infer a preliminary first period derivative of 5 x 10^-10 s/s.

In all cases the energy spectra are well fitted by an absorbed (Nh=1.7x10^22 cm^-2) powerlaw (Gamma=1.3) with a 1.-10.keV observed flux of approx 2x10^(-12) ergs/cm^2/s. A flux variability of a factor of about 2 may be present among ROSAT and AXAF.

Follow-up observations are in progress.