X-Ray Spectra of the High-Mass X-Ray Binary 4u 1700-37 Using Bepposax, Suzaku, and Rxte Observations

Abstract

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 T s1 1.4 keV and T s2 <1 keV, and an iron-line component. Using this model, we find that the photon power-law index is almost constant, Γ 1 ∼2 for all spectral states. However, Γ 2 shows behavior that is dependent on the spectral state. Namely, Γ 2 is quasi-constant at the level of Γ 2 ∼2 while the CC plasma temperature kT e 2 ( ) is less than 40 keV; on the other hand, Γ 2 is in the range of 1.3<Γ 2 <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 kT e revealed in 4U1700-37 is universal observational evidence for the presence of an NS in 4U 1700-37.

An XMM-Newton and NuSTAR Study of IGR J18214-1318: A Non-pulsating High-mass X-Ray Binary with a Neutron Star

“…The relatively slow 400 km s −1 wind of this donor star helps maintain a high mass accretion rate onto the compact object, resulting in a slightly higher X-ray luminosity (L 10 X 36 erg s −1 ) than in other Sg HMXBs (Barragán et al 2009). 4U 1700-377 displays the highest levels of variability of any of the non-pulsating Sg HMXBs; its flux, even at hard X-ray energies, varies by factors >100, and the pattern of spectral variations as a function of luminosity provides further evidence that 4U 1700-377 likely hosts an NS (Seifina et al 2016). However, the mass of the compact object in this system has been measured to be 2.44±0.27 M e (Clark et al 2002), placing it among the most massive NSs observed (Ozel & Freire 2016).…”

Possible detection of a new cyclotron feature in 4U 1700–37

“…The extreme 07 f star HD 153919 is a confirmed optical counterpart (Penny et al 1973;Hutchings et al 1973;Dolan et al 1980), of which an orbital eccentricity of 0.22±0.04 and a radial velocity semi-amplitude of 20.6±1.0 km s −1 have been measured (Hammerschlag-Hensberge et al 2003). The binary parameters of the 4U 1700-37 System are tabulated in Seifina et al (2016) and Islam & Paul (2016).…”

Monte Carlo simulations of thermal comptonization process in a two-component advective flow around a neutron star

“…13, for both the cases, to study the effect of cooling of the CENBOL, by the NBOL and by the disc. This is just to find out the two temperatures in the two halves which Seifina et al (STF13,STSS15) and Titarchuk et al (TSS14) found in their work by fitting COMPTB1 and COMPTB2 respectively. The results of this excercise is shown in Fig.…”