Suzaku detection of cyclotron line near 50 keV for A0535+26
ATel #613; H. Inoue (JAXA/Japan); H. Kunieda (Univ. Nagoya); N. White and R. Kelley (NASA/GSFC);T. Mihara and Y. Terada (RIKEN/Japan), H. Takahashi, M. Kokubun, and K. Makishima (Univ. Tokyo); and the Suzaku Team
on 26 Sep 2005; 01:34 UT
Credential Certification: Kazuo Makishima (maxima@phys.s.u-tokyo.ac.jp)
We report on the Suzaku detection of a cyclotron resonance absorption feature from the transient binary X-ray pulsar A0535+26.
Since the middle of August, the Suzaku X-ray Observatory (launched on 2005 July 10) has made regular observations using the X-ray telescope (XRT) plus X-ray CCD camera (XIS) system sensitive over 0.3-10 keV, and the Hard X-ray detector (HXD) covering 10-600 keV.
A0535+26 was observed with Suzaku for 20 ksec on 2005 September 14, and was clearly detected with both instruments. The HXD detection was up to at least 120 keV, with a 10-100 keV flux of 8.0E-10 ergs/s/cm2 which is equivalent to about 30 mCrab. The HXD spectrum reveals a broad absorption feature at about 50 keV, with a significance of 5 sigmas. When the feature is modelled by a cyclotron absorption factor applied to a mildly curving continuum, the resonance energy obtained is 44.9+-1.3 keV. This reconfirms the INTEGRAL (ATEL #601) and RXTE (ATEL #605) detections of the same feature on August 31-September 1 and August 28, respectively, when the source was about an order of magnitude brighter.
