We report the X-ray spectral and timing analysis of the high mass X-ray binary EXO 2030+375 during the 2021 type II outburst. We have incorporated NuSTAR, NICER, Swift/BAT & Fermi/GBM observations to carry out a comprehensive analysis of the source. Pulse profiles in different energy ranges and time intervals have been generated and analyzed. We have performed a brief comparison of the observations amidst the peak outburst condition and also during the decaying state of the outburst. Pulse profiles are found to evolve with time and energy. An iron emission line at (6–7) keV is observed in the X-ray continuum. Distinct absorption features were observed in the spectra corresponding to the peak outburst state while such features were not detected during the later decaying phase of the outburst. We have estimated the characteristic spin-up time scale to be ∽ 60 years. The continuum flux of the system and the varying luminosities covering the entire outburst period have been used to interpret the characteristics of the source. We have summarized the variability of various parameters along with their underlying physical implications.
We have studied the temporal and spectral properties of SXP 15.3, observed by NuSTAR in the hard energy range 3–79 keV during late 2018. Timing analysis of the NuSTAR observations predicts coherent pulsation at $15.2388\,\,\pm \,\,0.0002\, \mathrm{s}$. The pulse profiles in different energy bands demonstrate energy dependence. The shape of the pulse profile was generally suggestive of a fan-beam-dominated pattern, which, when combined with the measured luminosity, predicts that the source may be accreting in the supercritical regime. A non-monotonic increase in pulse fraction with energy was observed. The NuSTAR observations show that the pulse period of the source has spun up at a rate of −0.0176 s yr−1 compared with the previous analysis by the same observatory more than 1 year ago. The source flux in the present NuSTAR study in the 3–79 keV energy range is ${\sim }1.36\,\,\times \,\,10^{-10}\, \mathrm{erg\, cm}^{-2}\, \mathrm{s}^{-1}$, which corresponds to a luminosity of ${\sim }6\,\,\times \,\,10^{37}\, \mathrm{erg\, s}^{-1}$. Cyclotron line energy of the source is detected at ∼5 keV. Pulse-phase-resolved spectroscopy shows that the cyclotron line energy varies significantly with pulse phase and the photon index becomes softer with increasing flux. In addition, we have studied the evolution of the luminosity with time using 2017 and 2018 Swift/XRT observations. Analysis of the Swift/XRT data reveals that the photon index is positively correlated with the source luminosity, which is a characteristic of supercritical accretion phenomena.
In this paper, we report on the hard X-ray observation of the X-ray pulsar 1E 1145.1-6141 performed with the Nuclear Spectroscopic Telescope Array mission (NuSTAR). The coherent pulsation of the source with a period of ∼296.653 ± 0.021 s is detected. The source may be in the equilibrium phase, according to the most recent measurements of its pulse period. The pulse profile reveals a mild energy dependence and generally hints at a pencil-beam pattern. The pulse profile have evolved with time. The Pulse fraction is found to depend on energy with a fall in the value at ∼32 keV. The NuSTAR spectra can be approximated by a composite model with two continuum components, a blackbody emission, cut-off powerlaw, and a discrete component in the form of Gaussian to account for the emission line of iron. The estimated absorbed flux of the source is ∼6 × 10−10 erg cm−2 s−1 which corresponds to a luminosity of ∼5 × 1036 erg s−1. Pulse phase-resolved spectroscopy were performed to understand the evolution of spectral parameters with pulse phase. The estimated blackbody radius is found to be consistent with the size of the theoretical prediction.
We have presented NuSTAR and Swift observations of the newly discovered Be/X-ray pulsar eRASSU J052914.9-662446. This is the first detailed study of the temporal and spectral properties of the pulsar using 2020 observations. A coherent pulsation of 1411.5±0.5 s was detected from the source. The pulse profile was found to resemble a simple single peaked feature which may be due to emission from the surface of the neutron star only. Pulse profiles are highly energy dependent. The variation of the pulse fraction of the pulse profiles are found to be non-monotonic with energy. The 0.5-20 keV Swift and NuSTAR simultaneous can be fitted well with power-law modified by high energy cutoff of ∼ 5.7 keV. The NuSTAR luminosity in the 0.5-79 keV energy range was ∼ 7.9× 1035erg/s . The spectral flux in 3-79 keV shows modulation with the pulse phase.
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