Comprehensive broadband study of accreting neutron stars with Suzaku: Is there a bi-modality in the X-ray spectrum?
arXiv:2101.01727 · doi:10.1093/mnras/stab024
Abstract
We present a broadband spectral analysis of accreting neutron stars using data from XIS and PIN onboard \emph{Suzaku}. From spectral fits of these sources with a single continuum model including a powerlaw and high energy cut-off, cyclotron lines (where required), we studied the correlation between various spectral parameters. Among 39 sources we studied, 16 are those where the existence of a cyclotron line is known in literature, and 29 need a cutoff energy. Among these 29 sources, 18 have cutoff energy bunched in a range of 3-10 keV while for 11 sources, it spreads over 12-25 keV. This bi-modal behaviour is not based on the specific nature of the systems being a Be XRB or supergiant HMXB, nor on different beaming patterns characterizing their X-ray emission (as inferred from simultaneous study of their pulse profiles). The broadband coverage of \emph{Suzaku} also shows that the cutoff energies saturate for higher values of cyclotron line energies - consistent with previous works in literature - for both the groups and the width of the cyclotron line show a weak correlation with the cyclotron line energy. We also find an anticorrelation with luminosity for both spectral index and folding energy, respectively. Unlike previous works, we did not detect any anticorrelation between X-ray luminosity and EW of K lines. Finally, we show that the EW and flux of the iron K line are smaller in SFXTs than classical NS-HMXBs. We discuss these findings in terms of different properties of stellar winds and accretion mechanisms.
50 pages, 19 figures, accepted for publication in MNRAS
References in corpus (21)
- Thermal and Bulk Comptonization in Accretion-Powered X-Ray Pulsars
- Unveiling supergiant fast X-ray transient sources with INTEGRAL
- Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. I. The nature of the companion star
- The hard X-ray spectral evolution in X-ray binaries and its application to constrain the black hole mass of ultraluminous X-ray sources
- Patterns of variability in Be/X-ray pulsars during giant outbursts
- Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. II. The environment of the companion star
- Unveiling the nature of INTEGRAL objects through optical spectroscopy. VI. A multi-observatory identification campaign
- VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX301-2
- Unveiling the nature of six HMXBs through IR spectroscopy
- IGR J17544-2619: A new supergiant fast X-ray transient revealed by optical/infrared observations
- An XMM-Newton view of FeKα in HMXBs
- Long-term change in the cyclotron line energy in Hercules X-1
- Discovery and Modeling of a Flattening of the Positive Cyclotron Line/Luminosity Relation in GX 304-1 with RXTE
- Decade long RXTE monitoring observations of Be/X-ray binary pulsar EXO 2030+375
- A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522
- Variations in the pulsation and spectral characteristics of OAO 1657-415
- Spectral Softening Between Outburst and Quiescence In The Neutron Star Low-Mass X-Ray Binary SAX J1750.8-2900
- A Suzaku View of Accretion Powered X-ray Pulsar GX 1+4
- Probing the nature of IGR J16493-4348: Spectral and temporal analysis of the 1-100 keV emission
- The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE
- Multitude of iron lines including a Compton scattered component in OAO 1657--415 detected with Chandra