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Quasi-Periodic Oscillations detected in the hard-X ray flux of A 0535+26 by Fermi/GBM

ATel #2346; Mark H. Finger (USRA) , Colleen A. Wilson-Hodge (NASA/MSFC) and Ascension Camero-Arranz (FECYT) on behalf of the GBM Pulsar and Occultation teams
on 12 Dec 2009; 19:39 UT
Credential Certification: Dr. Mark H. Finger (Mark.Finger@msfc.nasa.gov)

Subjects: X-ray, Gamma Ray, Binary, Transient, Pulsar

Power spectra of the hard-X ray flux of A 0535+26 based on GBM observations during the current giant outburst (ATel #2324, ATel #2337) contained strong mHz quasi-periodic oscillations (QPO), similar to those seen in the 1994 giant outburst (Finger, Wilson & Harmon,1996). Between 3 mHz and 1 Hz the power spectra consists of an approximately 1/f power law continuum plus a broad QPO and a pulse component. On December 10 in the 25-50 keV band, the QPO was centered on 62 +/- 1 mHz, with a FWHM of 29 +\- 2 mHz. The fractional r.m.s. variability of the QPO was 9.1 +/- 0.4 %, that of pulse component was 6.6 +/- 0.5 % and that of the continuum 24+/- 1%. This QPO is of comparable strength in the 50-100 keV band, but is not detected in the 12-25 keV range.