Abstract Details
| Name: Pragati Pradhan Affiliation: Penn State University, USA and St. Joseph Conference ID: ASI2018_698 Title : Pulse Profile Studies and Hard X-Ray Properties of Neutron Stars Authors and Co-Authors : - Abstract Type : Thesis Abstract Category : Thesis Abstract : Neutron stars are known to be strong emitters of electromagnetic waves in a wide band of energy starting from the radio frequency to very high energy gamma-rays. These enigmatic objects show complex emission pattern in a wide energy band and the broad band emission characteristics of such neutron stars is an extremely challenging topic in high energy astrophysics. During the past years, the operation of the present generation X-ray satellites, such as RXTE, XMM-Newton, Chandra, Swift, INTEGRAL and Suzaku has opened a new era in the study of X-ray binaries. A recent X-ray mission ASTROSAT launched by India will now be adding an extra mileage in X-ray astronomy. This thesis mainly is a study of detailed timing and spectral analysis of accreting High Mass X-ray Binaries (HMXBs) and supergiant fast X-ray transients (SFXTs) that host neutron stars as their compact object. Compared to classical systems, SFXTs show a much more pronounced variability, comprising sporadic short X-ray outbursts and fainter flares with fast rise times (tens of minutes) and typical durations of a few hours. Outside these events, the SFXTs have average X-ray luminosities that are 2-3 orders of magnitude lower than the classical systems with similar orbital periods. In the latter half of the thesis, we have also explored the pulse profile evolution of rotation powered pulsars (RPPs) and dicussed the physical significance of the findings. Using archived data from XIS and PIN instruments onboard Suzaku, we have carried out a detailed broadband (0.3-70 keV) spectral analysis of all classical HMXBs and SFXTs by fitting the broadband X-ray spectrum of the sources with a powerlaw model modified with a high energy cut-off, emission lines and cyclotron line feature(s) (where required). Such a comprehensive study covering luminosities spanning five orders of magnitude is the first of its kind so far. We studied the correlation between various spectral parameters and discussed the findings in terms of different properties of the stellar winds and wind accretion mechanisms.Taking a clue from the remarkable distinction in absorption in Suzaku spectra of SFXTs and classical HMXBs (which is further accentuated by rigorous spectral analysis of all archived XMM data till July 2016), we propose that this difference between two classes can be explained either by assuming that the stellar winds in the SFXTs are less powerful than those in classical systems or that the interaction between the compact object and the stellar wind in these two classes is not the same. Further, we also discuss the elaborate timing and spectral analysis of individual NS-HMXBs like OAO 1657-415, SW J2000.6+3210, 4U 0114+65 and map the varied environs around these systems, albeit the same class, using Suzaku, Swift and INTEGRAL data. Lastly, we elaborate on the timing analysis of RPPs like PSR B1509-58 by studying the stability of the pulse profile shape with the Fourier decomposition technique using all available data from RXTE-PCA during the mission lifetime. We explored the usefulness of this pulsar in its use for interplanetary spacecraft navigation and also present a physical interpretation arising from this pulse profile study. |