We present the timing and spectral properties of the transient X‐ray pulsar GX 304−1 during its recent outburst in 2010 August, using observations carried out with the Proportional Counter Array (PCA) instrument on board the Rossi X‐ray Timing Explorer (RXTE) satellite. We detected strong intensity‐ and energy‐dependent variations in the pulse profiles during the outburst. The pulse profile showed significant evolution over the outburst. It showed complex structures consisting of a main peak with steps on both sides during the start of the outburst. On some days, a sharp dip‐like feature was seen which disappeared at the end of the outburst when the profile evolved into a sinusoidal shape. At low energies, the pulse profiles appeared complex, consisting of multiple peaks and a narrow minimum. The amplitude of the second brightest peak in low energies decreased with energy, and above 12 keV the shape of the pulse profile changed to a single broad peak with a dip‐like feature. The dip had energy dependence, both in phase and in width. We detected quasi‐periodic oscillations (QPOs) at 0.125 Hz with a harmonic. The QPO feature had a low rms value of 2.9 per cent and it showed a positive energy dependence up to 40 keV with the rms value increasing to 9 per cent at 40 keV. The QPO frequency decreased from 0.128 to 0.108 Hz in 12 days. During most of the outburst, the 3–30 keV spectrum of GX 304−1 can be well fitted with a partial covering power‐law model with a high‐energy cut‐off and iron fluorescent line emission. For a few of the observations carried out during the decay of the outburst, the partial covering absorption component is found to change to single‐component absorption. We also found that the partial covering and high‐energy cut‐off parameters vary significantly with the pulse phase.

We report the discovery of quasi‐periodic oscillations (QPOs) at 0.02 Hz in a transient high‐mass X‐ray binary pulsar KS 1947+300 using the RXTE Proportional Counter Array (PCA). The QPOs were detected during 2001 May–June, at the end of a long outburst. This is the ninth transient accretion‐powered high magnetic field X‐ray pulsar in which QPOs have been detected, and the QPO frequency of this source is lowest in this class of sources. The unusual feature of this source is that though the outburst lasted for more than 100 days, the QPOs were detected only during the last few days of the outburst when the X‐ray intensity had decayed to 1.6 per cent of the peak intensity. The rms value of the QPO is large, ∼15.4 ± 1.0 per cent with a slight positive correlation with energy. The detection of QPOs and strong pulsations at a low luminosity level suggests that the magnetic field strength of the neutron star is not as high as was predicted earlier on the basis of a correlation between the spin‐up torque and the X‐ray luminosity.

We report a detailed timing and spectral analysis of Rossi X‐ray Timing Explorer Proportional Counter Array (RXTE‐PCA) data obtained from observations during the outburst of a transient X‐ray pulsar 1A 1118−61 in 2009 January. The pulse profile showed significant evolution during the outburst and also significant energy dependence – a double‐peaked profile up to 10 keV and a single peak at higher energy. We have also detected quasi‐periodic oscillations (QPOs) at 0.07–0.09 Hz. The rms value of the QPO is 5.2 per cent, and it shows a significant energy dependence with highest rms of 7 per cent at 9 keV. The QPO frequency changed from 0.09 to 0.07 Hz within 10 d. The magnetic field strength calculated using the QPO frequency and the X‐ray luminosity is in agreement with the magnetic field strength measured from the energy of the cyclotron absorption feature detected in this source. The 3–30 keV energy spectrum over the 2009 outburst of 1A 1118−61 can be well fitted with a partial covering power‐law model with a high‐energy cut‐off and an iron fluorescence line emission. The pulse phase resolved spectral analysis shows that the partial covering and high‐energy cut‐off model parameters have significant changes with the pulse phase.

In this work, a cosmological model inspired by string/M-theory with fermionic field is taken into consideration. Here it is investigated whether the introduction of a non-Dirac fermionic field — characterized by an interaction term — affects the cosmological evolution. The self-interaction potential is considered as a combination of the scalar and pseudoscalar invariants. It is observed that the fermionic field under consideration behaves like an inflation field for the early universe and later on, as a dark energy field. The late time acceleration becomes more prominent by the addition of the interaction term. There is a slight decrease for the inflation peak as well as for the energy density. We see that the addition of higher-order terms to the fermionic part of Lagrangian does not significantly change either the inflation or the late time acceleration behavior.

In this work, a cosmological model inspired by string theory with Gauss–Bonnet term coupled to the fermionic field is taken into consideration. The self-interaction potential is considered as a combination of the scalar and pseudoscalar invariants. Here the cosmological contribution of the coupling of Gauss–Bonnet term with a non-Dirac fermionic field — characterized by an interaction term[Formula: see text] — is investigated. It is observed that the new type of coupling plays a significant role in the accelerating behavior of the universe. Specifically, in addition to the late time acceleration for the universe, [Formula: see text] produces an early decelerating behavior. The behavior of the equation-of-state parameter (w) is such that it guarantees the stability of the theory.