2016ApJ...821...23S -
Astrophys. J., 821, 23-23 (2016/April-2)
X-ray spectra of the high-mass X-ray binary 4U 1700-37 using BeppoSAX, Suzaku, and RXTE observations.
SEIFINA E., TITARCHUK L. and SHAPOSHNIKOV N.
Abstract (from CDS):
We present an X-ray spectral analysis of the high-mass binary 4U 1700-37 during its hard-soft state evolution. We use BeppoSAX, Suzaku, and Rossi X-ray Timing Explorer observations for this investigation. We argue that the X-ray broadband spectra during all of the spectral states can be adequately reproduced by a model consisting of a low-temperature blackbody component, two Comptonized components which are both due to the presence of a Compton cloud (CC) that up-scatters seed photons of Ts1 <= 1.4 keV and Ts2 < 1 keV, and an iron-line component. Using this model, we find that the photon power-law index is almost constant, Γ1 ∼ 2 for all spectral states. However, Γ2 shows behavior that is dependent on the spectral state. Namely, Γ2 is quasi-constant at the level of Γ2 ∼ 2 while the CC plasma temperature {{kT}}_{e}^{(2)} is less than 40 keV; on the other hand, Γ2 is in the range of 1.3 < Γ2 < 2 when {{kT}}_{e}^{(2)} is greater than 40 keV. We explain this quasi-stability of Γ during most of the hard-soft transitions of 4U 1700-37 in the framework of a model in which the resulting spectrum is described by two Comptonized components. We find that these Comptonized spectral components of the high-mass X-ray binaries 4U 1700-37 are similar to those previously found in neutron star (NS) sources. This index dependence versus both the mass accretion rate and kTe revealed in 4U 1700-37 is universal observational evidence for the presence of an NS in 4U 1700-37.
Abstract Copyright:
© 2016. The American Astronomical Society. All rights reserved.
Journal keyword(s):
accretion, accretion disks - black hole physics - radiation mechanisms: non-thermal - stars: individual: 4U 1700-37 - X-rays: binaries
Simbad objects:
13
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