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‘θ –ΌFCyclotron resonance scattering features and Magnetic field of pulsars
uŽtFDr. Gaurava K. Jaisawal iƒCƒ“ƒh@Astronomy and Astrophysics Division@Physical Research Laboratoryj
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‰ο κF—Šw•”‚P†ŠΩ•¨—‰ο‹cŽΊ

Abstract
Cyclotron resonance scattering features or cyclotron absorption lines are unique features observed in hard Xray spectra of accretion powered X-ray pulsars with magnetic field of the order of 1012 G. Detection of these features is a powerful tool and the only direct method to estimate the magnetic field strength close to the surface of neutron stars. Corresponding to magnetic field of ~1012 G, the fundamental lines are expected in 10-100 keV energy range with harmonics expected at multiples of fundamental line energy. However, we detected first harmonics of cyclotron line at less than twice of the fundamental line energy (~ 1.7 times the fundamental line energy) in Be/X-ray binary pulsar Cep X-4. With the broadband spectral capability of Suzaku and NuSTAR observatories, we have investigated several X-ray pulsars to understand line shape, width, magnetic field mapping, anharmonicity in the line energies and luminosity-dependent properties of cyclotron lines. The results obtained from these works and new detection of cyclotron line in unknown/ poorly studied sources will be discussed in detail.

Poster: PDF



‘θ –ΌFSFXTs vs sgHMXBs: does the difference lie in the companion wind?
uŽtFDr. Pragati Pradhan iƒCƒ“ƒh St. Joseph's Collegej
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‰ο κF—Šw•”‚P†ŠΩ•¨—‰ο‹cŽΊ

Abstract
We present a comparative study of classical supergiant HMXB and SFXT systems by using the absorption column density and equivalent width of iron KƒΏ line in their X-ray emission. The work has been carried out using out-of-eclipse observations sgHMXBs(SFXTs) with Suzaku and XMM-Newton and we have taken care to separately analyse parts of any observation with significant variation in the spectrum. Analysis of all archival Suzaku and XMM-Newton observations of these systems show that sgHMXBs have a wide range of equivalent width of iron emission line and equivalent column density of absorption, both over three orders of magnitude. In comparison, the SFXTs show a smaller range for both the parameters, less than one and a half order of magnitude. These findings indicate a crucial difference in the wind characteristics of the companions of sgHMXBs and SFXTs, which could be an important factor for the intriguing difference in average X-ray luminosity and transient behavior between these two classes of sources.

Poster: PDF