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ATEL # 2537; Mark H. Finger (USRA) and Ascension Camero-Arranz (FECYT)
on 6 Apr 2010; 18:35 UT
Password Certification: Dr. Mark H. Finger (Mark.Finger@msfc.nasa.gov)
Subjects: Binaries, Pulsars, Transients
RXTE ToO observations on 6 April 2010 of the x-ray transient detected by MAXI (ATel #2527) show strong pulsations at a period of 205.26(5) s (not barycentered), with a 35% pulse fraction ([mean-min]/mean, 3-60 keV). This is close to the period of 202.5(5) s found by Reig & Roche (1999, MNRAS 306, 100) for RXTE J0440.9+4431 = BSD 24-491 = LS V +44 17. We therefore conclude this is the out-bursting source. The mean count rate was 379 c/s/PCU. As far as we know, this is the first detection of transient behavior in a source classified as a persistent Be/X-ray binary pulsar.