Cyclotron Line in XTE J0658-073
ATel #200; William Heindl (UCSD/CASS), Wayne Coburn (UCB/SSL), Ingo Kreykenbohm (IAAT/ISDC), Joern Wilms (IAAT)
on 23 Oct 2003; 20:19 UT
Credential Certification: William A. Heindl (wheindl@ucsd.edu)
Subjects: X-ray, Neutron Star, Transient, Pulsar
Joint RXTE PCA and HEXTE spectral analysis of the 2003 October 20
observation of the 160.7 second accreting pulsar XTE J0658-073 (Morgan
et al. 2003, ATEL #199) reveals a strong cyclotron line at ~35keV. We
fit a range of continuum models typical of accreting pulsars to the
pulse phase averaged spectra. In all cases, significant residual
deviations characteristic of a cyclotron feature were detected above
~20keV. To determine spectral parameters, we used a power law which
breaks smoothly to a power law times an exponential, modified by an
absorption line with a Gaussian optical depth profile (MPLCUT*GABS,
Coburn et al. 2002, ApJ, 580, 394), plus an iron line. The resulting
parameters are, (continuum): photon index = (1.09 +/- 0.01), break
energy = (16.8 +/- 0.1)keV, exponential folding energy = (11.5 +/-
0.3)keV, (cyclotron line): energy = (36 +/- 1)keV, sigma = (7.5 +/-
1.0)keV, central optical depth = (0.33 +/- 0.05). These parameters
are typical of cyclotron line pulsars. The line centroid implies a
magnetic field of 3E12*(1 + z) G (z is the gravitational redshift at
the line-forming region).
