RXTE confirms cyclotron line near 50 keV for A 0535+26
ATel #605; Colleen A. Wilson (NASA/MSFC), Mark H. Finger (NSSTC)
on 13 Sep 2005; 21:19 UT
Credential Certification: Colleen A. Wilson (Colleen.Wilson@nasa.gov)
Subjects: X-ray, Gamma Ray, Binary, Neutron Star, Transient, Pulsar
Referred to by ATel #: 613
The cyclotron feature near 50 keV in the spectrum of A 0535+26 measured with Integral (Atel #601) is visible in the count rate spectra of RXTE/HEXTE data from the current outburst.
The feature is significant at the 17 sigma level in the 2.7-150 keV PCA/HEXTE energy spectrum from observations on August 28 between 13:55 and 14:54 UT. Using a MPLCUT (Coburn et. al. 2002, ApJ, 580, 394) continuum model and a Gaussian absorption line model for the cyclotron feature, we find the following line parameters: centroid energy 48.5+-0.7 keV, sigma 5.9+0.5-0.9 keV, and depth 0.75+-0.07. The 2-100 keV flux measured with RXTE in this observation of A 0535+26 was 2.5e-8 ergs/cm^2/s (Lx = 1.2e37 erg/s @ 2 kpc).
The August 28 observation occurred during a narrow intensity spike near the beginning of the current outburst (ATel #595, #597). Following the spike, the outburst rose in intensity until September 3, when the 2-100 keV flux was 2.2e-8 ergs/cm^2/s. Since September 3, the intensity has been declining.