F. Fuerst, S. Suchy, I. Kreykenbohm, L. Barragan, J. Wilms, K. Pottschmidt, I. Caballero, P. Kretschmar, C. Ferrigno, R. E. Rothschild
We present an in-depth study of the High Mass X-ray Binary (HMXB) GX 301-2
during its pre-periastron flare using data from the XMM-Newton satellite. The
energy spectrum shows a power law continuum absorbed by a large equivalent
hydrogen column on the order of 10^24 cm^2 and a prominent Fe K-alpha
fluorescent emission line. Besides the Fe K-alpha line, evidence for Fe K-beta,
Ni K-alpha, Ni K-beta, S K-alpha, Ar K-alpha, Ca K-alpha, and Cr K-alpha
fluorescent lines is found. The observed line strengths are consistent with
fluorescence in a cold absorber. This is the first time that a Cr K-alpha line
is seen in emission in the X-ray spectrum of a HMXB. In addition to the
modulation by the strong pulse period of ~685 sec the source is highly variable
and shows different states of activity. We perform time-resolved as well as
pulse-to-pulse resolved spectroscopy to investigate differences between these
states of activity. We find that the fluorescent line fluxes are strongly
variable and generally follow the overall flux. The N_H value is variable by a
factor of 2, but not correlated to the continuum normalization. We find an
interval of low flux in the light curve in which the pulsations cease almost
completely, without any indication of an increasing absorption column. We
investigate this dip in detail and argue that it is most likely that during the
dip the accretion ceased and the afterglow of the fluorescent iron accounted
for the main portion of the X-ray flux. A similar dip was found earlier in RXTE
data, and we compare our findings to these results
View original:
http://arxiv.org/abs/1110.2700
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